White mould is known as Penicillium Candidum or white mould spores or PC or PCA. The aim of adding white mould spores is to get an even coverage of white mould on the surface of the cheese as soon as possible after demolding and salting. White mould spores can be added to the milk and/or the brine and/or sprayed on the surface of the cheese. Some cheesemakers will use more than one of these methods to add the white mould spores. Camembert is a surface ripened mould cheese. The cheese matures from the surface to the inside. We will cover this in another article. A good coverage of white mould is a key element to developing a good flavour and softening the paste of the cheese as it ripens.
The white mould spores usually do not start growing instantly on the surface of the cheese.
The first hurdle to the growth of white mould is the acidity level of the cheese. A good Camembert can be quite acidic when it is moulded on day 2. The ideal pH range of Camembert is usually between 4.7 and 5.1; however, the white mould spores will not grow well at this level of acidity. Geotrichum Candidum (Geo) is more acid-tolerant and grows very quickly on the surface of the cheese at this acid level and can very rapidly deacidify the surface of the cheese. This lower surface acid level is now more suited to white mould growth. Other yeasts such as DH ) Debaryomyces Hansenii), CU (Candida utilis ) and KL (Kluyveromyces lactis) are also very capable of rapidly deacidifying the surface of the cheese. While Geo and these yeasts are not usually visible, they will all also provide different flavour profiles within the cheese.
When the cheese is salted on day two, there is an intense amount of salt in contact with the surface at this stage. The white mould spores will tolerate this salt, but only just, but for the white mould to grow, it has to wait until some of that salt has defused away from the surface to the inner paste of the cheese.
White mould will not grow with wet feet. In the first 24 hours after salting, the camembert is not placed in a 95% humidity environment. It usually sits on a rack in a covered container and is turned several times. This will allow moisture to run off the surface of the cheese physically. This cheese turning assists moisture removal and also allows fresh oxygen to the surface of the cheese. The cheeses at no time should be allowed to dry off or harden on the surface; white mould will not grow well on a harder or drier surface. It is good to hold the cheese at 14c to 16c for this 24 hours which favours the growth of the yeasts. You may have noticed that sometimes your cheese has a surface that is higher on the outside than the inside, sort of saucer-like in appearance. As moisture lands on the surface of the cheese, it will pool in the centre of the cheese instead of running off the cheese. This wetness will restrict good mould growth.
When both the 24 hours of drying and Geo growth has been, the cheese needs to be held at 10 -14c and at 95% relative humidity and turned every 24 hours. The turning is important for fresh oxygen and even mould growth.
When the white mould is fully developed, it is ready for wrapping. Excessive white mould growth at this stage will cause a thick rind to develop. For best results, use professional cheese wrap. I know baking paper and foil etc. is cheaper, but professional wraps help regulated moisture between the surface of the cheese and the wrap. They are better at keeping the white mould healthy and white. As we said earlier, white mould does not like wet feet. You may have taken your camembert out of a ripening container at 10c. This cheese is cold, and when left on the bench waiting to be wrapped, condensation will quickly form on the surface of the cheese. This is particularly important on hot, humid summer days. This wetness will then be trapped under the wrapper, and it will kill the mould (and make the cheese really smell) during the upcoming maturation.
Then finally, when you have now wrapped your cheese. It needs to be held at 7C or similar. 10 to 14c is to warm and gives higher proteolysis and less lipolysis. You get more and better flavour if the lipolysis is allowed to develop. BUT the container the cheese is held in needs to be completely dry, so no condensation in the container and it needs to have a lid. The domestic fridge is evaporative and even at four weeks in this sort of fridge will gradually dry the cheese out. A dry cheese will not ripen sufficiently.
Having both the correct level of moisture and acidity in a cheese that is 24 hours old is very important in making good quality cheese. The 24 hours’ time is the point where you will have a fairly good idea of how well your cheese is going to turn out. Simply the cheese is now in its finished state and it is at day 1 of the journey down the path of maturation. But unfortunately, there is not a lot that you can do to remedy any deficiencies with how the cheese is made. It is important to know, that when you add the curds to the hoop, both the moisture and acid level are very important to the outcome of the cheese. The cheese quality at day one will be heavily influenced by the size of the curd particle when those curds were placed into the hoop 24 hours earlier and the temperature that the hooped curd was held at over the 24 hours after hooping.
When you add your curds to the hoop, those curds still contain water (moisture), and lots of it. Where there is cheese moisture in curds there is also lactose. Think, how much moisture comes out of your hoop in the next 24 hours after you have hooped the curd. The cultures in the curd at the time of hooping have grown to much larger numbers compared to when you started making that cheese. And these cultures are at their most active just coming out of warm curd and whey. So, with lots of lactose and lots of very active cultures, there will be ongoing acidification of the curds over the next 24 hours. If the curd particle at hooping is larger than the required size at hooping, you will have an excess of lactose for the curds s they continue fermenting. This will result in excessive lactic acid produced, particularly in the first 24 hours after hooping. This will result in an over acid cheese. The reverse is also true if the curds are smaller than what they should be, the cheese may end up with less acid in it.
The second thing that is important at hooping is the temperature that the curds are held at over the next 24 hours. The acid produced over the next 24 hours will cause the curd to shrink and that shrinkage helps gradually expel the moisture from the cheese. Have you noticed how much whey has come from your cheese overnight? If you have a lower temperature overnight you will have a lower level of starter activity, resulting in a lower acid level in your cheese. Which means you may have excessive moisture in the cheese on day 2. For example, if the ambient temperature is colder than 20°C then the starter cultures will start to slow down the rate of acid production. If the temperature drops to below 10°C there will very little acid production and an even lower acid level in the cheese. An ideal temperature to keep cheese at overnight may be between 25°C to 28°C for mesophilic cultures and low 30°C for thermophilic cultures. Note that while minimum overnight temperatures are important but very hot summer days and nights are not. While ambient temperatures may be 40°C in some places, the cheese temperature will be well below this and will not be heavily affected.
In summary, the size of the curds at hooping and the temperature that the cheese is held at overnight are both interrelated and very important to the final quality of your cheese.
Cheese has been produced from many animals over several thousands of years. Milk from cow, goat, sheep and buffalo are quite common with less common animals being the yak, camel, llama, ass, elk, mare, caribou and reindeer.
The principal constituents of milk are water, milkfat (butterfat), protein, lactose, minerals and enzymes. Milk also contains trace amounts of other substances such as vitamins, gases and white blood corpuscles (leucocytes).
The average composition of milk is given below.
The average composition of milk:
Total Solids & Solids-not-Fat (TS & SNF)
When water and gases are removed from milk the remaining residue is called the total solids (TS) or dry solids content of milk.
When the fat is removed from the total solids the remaining portion or constituents are referred to as solids-non-fat (SNF)
Total solids–fat = solids-non-fat.
Solids-non-fat = protein + lactose + others.
The components of milk vary in their characteristics and significance and how they differ can affect how you make your cheese. The major aspects of the constituents are:
Milk is nearly 90% water. Milk without water is milk powder. Cheese is a preserved form of milk. The water of milk is the same colourless fluid known to everyone. In cheese, it is technically referred to as ‘moisture’. Moisture in cheese serves two main purposes.
Suspension of constituents – the lactose, portion of the protein and the ash are dissolved in the water. The fat and the rest of the proteins are suspended in the form of small particles.
Water is essential for the growth of bacteria, and for the enzymatic and chemical reactions which occur in the manufacture and maturing of cheese. The amount of water in the cheese influences the rate of maturing and the hardness or softness of the cheese. A hard, grating Romano will have about 23% moisture (77% TS). Cheddar is 37% moisture (63% TS), a Camembert 53% moisture (47%TS) Quark 79% moisture (21%TS).
If milk is left to stand, a layer of cream will form on the surface. The cream differs considerably in appearance from the bottom layer of skim milk. Under the microscope, the cream can be seen to consist of a large number of spheres of varying sizes floating freely in the milk. Each sphere is surrounded by a thin skin.
Cow milk fat is yellow in colour where all other mammal’s milk is white. Cow’s milk contains a colouring pigment called Beta-carotene (a carotenoid which is a precursor of vitamin A). The same carotenoid is also found in vegetables like a carrot.
In cheese, fat gives the product a flavour, richness, creaminess and smoothness as well as affecting the softness and hardness of the cheese. The breakdown of fat by bacteria and enzymes is responsible for much of the strong flavour development in matured cheese. In some cases, excessive fat breakdown leads to rancidity. The fat content influences the firmness and smoothness of the cheese. Lipase is a lipolytic enzyme that is added to milk increase the rate of fat breakdown.
Proteins in milk
Proteins are an essential part of our diet. The proteins we eat are broken down into simpler compounds in the digestive system and in the liver, and these compounds are then conveyed to the cells of the body where they are used as a construction material for the body’s own proteins.
Milk proteins are generally divided into 4 main classes. Casein which makes up 78% of the proteins in milk, the whey proteins albumin and globulin and the membrane proteins.
Casein is vital for the coagulation of milk. During coagulation, the casein forms a fibrous network which enmeshes all the other constituents and retains most of them in the cheese. Casein is present in milk in combination with calcium, in the form of colloidal particles called micelles.
The coagulated casein can hold moisture and the solid components of the milk like a sponge. It will shrink and expel moisture in response to changes in temperature and acidity, and these are the means by which moisture expulsion is achieved in the cheese vat. If you are not careful in stirring the curd, these structures are broken up and more moisture plus some of the solids components are released into the whey. Simply you will get less solids cheese in your cheese.
Casein influences the firmness and resilience (body) of cheese; the greater the proportion of casein in the cheese, the firmer being the body. Casein is broken down by bacteria and protease enzymes during maturing, and its breakdown products, as with those of the fat, are responsible for some of the flavour development. Rennet is a protease enzyme.
Between 10 and 15% of the protein in milk consists of albumin. In cheesemaking, the albumin remains dissolved in the whey. Albumin is therefore called whey protein.
Globulin occurs in very small amounts in normal milk. It coagulates when the milk is heated to about 75oC. Colostrum (the milk which cows produce during the first three days after calving) contains large amounts of albumin and globulin. Colostrum milk should not be pasteurised, because it coagulates when heated.
Lactose is a sugar (often referred to as milk sugar) and thus belongs to the group of organic chemical compounds called carbohydrates. It is exclusively found in mammals’ milk. If you taste freshly cut curd it has a slight sweet taste to it, but lactose is only 1/6 the sweetness of sucrose.
Lactic acid bacteria contain an enzyme called lactase, which attacks lactose, splitting its molecules into simple sugars glucose and galactose. Enzymes from the lactic acid bacteria then attack the glucose and galactose, converting them into various acids of which lactic acid is the most important in cheesemaking. This is what happens when milk goes sour, i.e. fermentation of lactose to lactic acid. The lactase enzyme is added to milk to break down the lactose into these simple sugars to make it lactose-free milk for persons with lactose intolerance.
Lactose is water-soluble, and 90% of it is lost in the whey, from which it can be recovered if economically feasible. The remaining lactose sits in the curd particles and is of vital importance, as it provides the food for the starter organisms which convert it mainly into lactic acid. The volume of lactose (and moisture) remaining in the curd at the whey off step and the subsequent conversion or fermentation is the key to making good quality cheese.
Lactic acid in milk:
The total volume of minerals in milk is very small, less than 1% but they are very important to the cheesemaking process. Minerals are in two forms in milk: soluble (in whey) or colloidal (linked to proteins).
Milk is known as a good source of calcium, magnesium, phosphorus, potassium, selenium, and zinc. The bond between calcium, phosphorous and the casein in the milk is critical to the formation of a good curd. In milk, approximately 67% of the calcium, 35% of the magnesium, and 44% of the phosphate are salts bound within the casein micelle and the remainder are soluble in the serum phase. We have all added calcium chloride to milk to supplement the existing calcium levels in the milk. Note that adding Calcium Chloride should be done asap as it takes approximately 60 minutes for the Calcium to bind with the casein. Adding Calcium just before adding rennet is of little benefit.
Cows that have reached the end of lactation or cows with mastitis will have a significant imbalance in the mineral content of the milk.
Enzymes are proteins that have biological functions and have both detrimental and beneficial effects on the cheese. Milk enzymes come from several sources: the naturally occurring enzymes in the milk that are provided to help the calf digest the fats, proteins and sugars in the milk. Some of these enzymes will be destroyed by pasteurisation. Then there are enzymes from bacteria, from good bacteria such as the starter cultures and the white and blue moulds and the rennet. Then there are enzymes from bacteria that are not essential and those are considered contaminates, whether those bacteria airborne contamination or unclean equipment or personal hygiene.
How to freeze milk when you have an excess
Do you have a fresh supply of milk and it is too much that you cannot use it all? You are the envy of many cheesemakers across Australia. Or do you want to want to have access to goat milk that may not be as readily available later in the year? Freezing that milk is an option available to you. But what is the best way to freeze milk?
Freezing and Cooling Systems: Domestically you may not have access to larger cooling or freezing systems such as cold rooms, freezer rooms or milk storage vats. These items are designed to chill or freeze the milk in a very short period. The domestic refrigerator or freezer will only reduce the temperature of the milk over a much longer period. The aim of freezing should be to remove the heat from the milk as quickly as possible. Simply put, you want to achieve freeze fast and cool slowly. In our summer weather it’ is very easy to do the opposite. Slow freezing and fast thawing produce sharp ice crystal structures that damage the fat and protein in the milk and may give milk and inferior structure that will make an inferior cheese. The ‘sludge’ that you find in the bottom of containers are damaged fat and protein cells.
Volume of milk to be frozen: Fresh milk is lower in both microbial and enzyme activity than older milk. If you are getting a few litres per day you may not want to freeze each day you may want to composite it. But you must make a judgement based on how often you freeze, the volume of milk that needs to be frozen, the age of the milk to be frozen, and your time available to undertake the freezing.
Containers: Use containers that are freezer safe. Glass has a better heat transfer for chilling and freezing than plastic. It’s not that significant though so plastic if that is all that is available is also fine. However, the smaller the container the better. Two x two-litre containers will freeze a lot faster than one x four-litre containers.
Heat load: Remove the initial heat out in the milk before freezing it by chilling it, basically have the milk as cold as you can. If the milk is straight from the animal it will be around 37°C, so add it straight to the sanitised containers used for freezing, then use ambient water or even better, chilled water to reduce initial heat load. Keep direct light, especially sunlight off the milk. Leave the then mostly chilled milk in the fridge to finish cooling and await freezing. When freezing, leave an air gap between the individual containers to aid cooling.
Thawing: The easy way to thaw frozen milk is to leave the frozen milk on the bench. But thawing should be slow. The best way to thaw the milk is to leave it in the fridge for 24 hours.
Pasteurisation: You may want to use the milk as raw milk so good hygiene along the way is important. However, if you want to pasteurise the milk you need to choose between pasteurising the fresh milk before freezing or the thawed milk. My personal preference is to pasteurise after thawing. There is less heating involved and the heating step in closer to the actual consumption or the cheesemaking step.
Hygiene: Keep milking, personal and equipment hygiene high always for milk for human consumption. Equipment to be well cleaned and then well sanitised immediately before use.
Labelling: Adequately label all containers with the date of manufacture and date of freezing.
Quality ingredients are an essential part of making good cheese. Ingredients need to be predictable in their use. If they are not, then your cheese may not turn out as you want them to. There are many variables in cheesemaking that can affect how cheese turns out. Using old and unpredictable ingredients should not be one of those variables.
If you have been making cheese long enough, you will have come across cheesemaking ingredients in your fridge or freezer that will soon have reached or even passed their best before or expiry date.
There are only a handful of manufacturers across the world that manufacture starter cultures and ingredients for making cheese. There is not a lot of difference in the way the cultures are selected grown and distributed.
Lactic Starter Cultures
Lactic Starter cultures to make cheese come in various forms:
Most home cheesemakers will be using freeze-dried cultures to make cheese. Some will also be growing their own liquid cultures, some back-slopping and using some raw milk. These methods require some degree of monitoring to obtain the correct end result and optimal activity. These processes will not be discussed in this article.
Starter cultures that are freeze-dried look like milk powder but are highly concentrated with bacteria. There is somewhere around the 1010to 1013 organisms per gram of powder. The technology used to make freeze-dried cultures has been used commercially since the 1970s. The cultures come with different recommendations on the actual shelf of the product. For example:
Company A storage recommendation: At least 24 months from the date of manufacture when stored according to recommendations. At 5°C the shelf life is six weeks.
Company B storage recommendation: 18 months from the date of manufacture at <= 4c
Company C storage recommendation: Cultures can be kept for six months without loss of activity if stored between 4°C– 8°Cand 12 months if stored at -18°C
There are various terms used: ‘best-before’, ‘date-of-manufacture’. The important issue here is can you still use your cultures after the end use date has been reached? By storing the cultures in the freezer, you are maximising their shelf life. There should be no loss of the culture’s viability if the culture is stored in the freezer and the freezer is operating correctly. Generally, the cultures will last for another several months. I think we have all used cultures in this way. After several months have passed their optimum performance may or may not have diminished, you simply cannot tell without some sort of technical analysis. So, you need to decide to continue to use those cultures or replace them with a new batch. At stake is a possibly inferior batch of cheese plus the cost of the milk and all the time put into making and maturing it.
Flavour and Ripening Cultures
Flavour and ripening cultures to make cheese usually come in these three formats:
Most home cheesemakers will be using either the freeze-dried or the hyptonic formats.
Flavour and ripening cultures that are freeze-dried look like milk powder but are highly concentrated with. As in the lactic starter cultures, these cultures also come with different recommendations on the actual shelf of the product. For example:
Company A storage recommendation: culture can be kept for four months if stored at +4°C or
for six months if stored at -18°C,
Company B storage recommendation: 12 months from the date of manufacture at -18c or 2 months if stored at +4c
Company C storage recommendation: At least 12 months if stored below -18c
Flavour and ripening cultures can be quite varied in the type of microbe that is being used for bacteria, yeast, moulds etc. Due to this variation between organisms and each organism having different shelf life characteristics, the shelf lives between product s will also vary. So, a single shelf cannot be used against all of the ripening cultures you have. You are still maximising the life of your cultures by storing them in the freezer (unless they are specifically to be stored in the fridge). There should be no loss of the cultures viability if the culture is stored in the freezer and the freezer is operating correctly. Generally, the cultures will last for a few months after the best before date has been reached. Usually, I find they do not last as long after the best-before as is the case with the lactic cultures. After a few months past the best before date has been reached it is recommended that they are discarded, and a new batch used.
Rennet is such a key ingredient in making cheese that my recommendation is to make cheese using a rennet where the best before date has not expired.
Lipase can usually be stored in the freezer or fridge. It is very stable and can be stored for several months after the best before date has been reached.
Annatto has a shelf life of around 12 months from the date of manufacture. The deterioration is with oxidation. Some settling of the solids may also occur. Its function is to change the colour, so it is not going to change the functionality of the cheese. I find it will last for several months past the best before date.
Freeze Dried or the technically correct term is Lyophilised: Often referred to as ‘LYO’. Cultures are manufactured using a low-temperature dehydration process so that the heat used in traditional drying processes does not damage the bacterial cells. The bacterial cultures are grown in a liquid medium, but the acid is neutralised during the manufacture, again not to damage the bacteria cells. The incubated liquid is then frozen and then placed under a strong vacuum which lowers the temperature at which evaporation occurs. Evaporation of the moisture in the liquid occurs until the liquid portion a powder remains.
Hyptonic: The live cultures are stored in a liquid solution. The liquid is specially balanced to keep the cultures alive but also the keep the medium they are in from deteriorating with age. Salts and sugars are used in the liquid solution. The bacterial cells have membranes which are permeable to sugars and water diffusion, but which do not allow the storage solutions salts to pass. The cell membrane allows the cell to choose, using receptors and channels, the things it will let in, e.g. nutrients.
Cheese is made ‘in-the-whey’
When you have cut the curds you are then ‘in-the-whey’ and at the most important step in making good cheese. It is the step in cheesemaking where you can make a big difference to the quality of your cheese. The several steps below are all happening around the same time when you make your cheese.
By increasing the temperature of the curds and whey closer to 40C, you increase the gel strength of the curd particle, this, in turn, increases the rate of whey (moisture) loss. But be mindful that the rate of acidity development will also change with any temperature change. Based on whether you are using mesophiles or thermophiles or combinations of these cultures.
Stirring of the curd
Stirring of the curd helps with whey removal from the curd. Two reasons, firstly it helps stop curd sinking to the bottom of the vat and secondly as the curd particles collide with each other (collision effect), the wall of the cheese vat and the stirrer, the rate of whey loss increases.
Acidity of the curd during setting
Curd strength increases in a more acidic environment. The more acidic the curd is during the curds and whey the stronger curd will become
Acidity of the curd during curds/whey stage
A higher level of acidity (lower pH) will shrink the curd causing more moisture from the curd, so more calcium, phosphate and other minerals will also be removed from the curd. A Cheddar cheese with a final pH around 5.0/5.1 will have 50% less Calcium than a hard-Swiss style with a final pH of 5.6. The Cheddar will be crumbly and the harder Swiss will be more elastic
If you completed all the required steps and the curd has not reached the required level of set. If you proceed to cut, you will have soft curd that will result in a curd with higher moisture and higher acidity. The reasons this occurs can be quite varied. If you were using the same milk again, maybe increase CaCl or if the milk is that bad don’t use that milk. But as cutting is delayed longer, the level of acidity will increase. A solution may be to wait until a firm set is achieved, cut smaller or stir longer or faster to remove residual lactose and moisture
Solids levels of the milk
Milk with higher solids levels will set faster and have a stronger curd particle than milk with a lower solids level. Solids include fats, proteins, lactose, minerals, vitamins but it is the increased levels of protein, calcium and phosphorous in the milk that provide that strength of the curd
Washing the curd
Washing the curd involves removing some of the whey, usually 20% – 30% and replacing it with pasteurised water. This will rapidly remove some of the acid and lactose from the curd and some of the minerals. The latter helping to make the curd softer and more flexible. Washing is usually used for sweeter cheese styles. Two simple examples, washing turns a Farmhouse Cheddar into a Colby or turns a Parmesan into a Comte
Dry stirring or stirring after half whey off
This is gently stirring the curd after you have drained most or all the whey to rapidly remove moisture from the curd. Removing moisture also removes lactose. But this process is used for semi-hard and hard cheese mostly. It is also the last resort as it can break up the curd if you are not careful. A scenario is that the correct level of acidity has been reached but the curd still has too much moisture. If you delay the whey-off the acidity will get too high, so half whey off or full whey off at that point, keep curd warm and gently stir it to remove moisture.
Salt plays a significant role in directly influencing the flavour, ripening and appearance of cheese. Many points can be written and discussed on salting and cheese, here are just a few points.
Salt has two other important effects, which more precisely determine the amount to be used. These are the extraction of moisture from the curd and the retarding of starter development and bacterial processes associated with cheese ripening. The application of salt to the curd causes more moisture to be expelled, both through an osmotic effect and a salting-out effect on the protein. The osmotic effect may be likened to the creation of suction at the surface of the curd causing moisture to be drawn out. The salting out effect is the natural tendency of the protein to precipitate from a solution in the presence of salt.
Salt is incorporated into cheese by one of the following methods:
The quantity of salt used depends on the variety of cheese for example soft lactic cheese will have less than 1%, a brine salted feta at 4.5%, Cheddar less than 2%, Camembert and Gouda will have slightly more than 2%, an Emmenthal less than 1%, blue vein salting can vary greatly and can be greater than 3%. Cheese with propionic acid bacteria added will have propionic inhibited at salt levels over 2%. In blue mould cheese, the blue spores are germinated at levels of 1% salt. Is white mould cheese, the white mould is mostly unaffected by salt, but the Geotrichum Candidum is heavily affected by salt. Salt can be used to control the final acidity of, e.g. if salting is delayed then acid development may continue to excessive levels, if salting is carried out too early it can slow the development of lactic acid production. Too much salt will leave a definite salty flavour in the cheese and can affect textures, making the cheese dry and crumbly.
However, the effect of salt on the bacterial, both starter cultures and spoilage bacteria depends on the strength of the brine formed by the solution of the salt in the moisture of the curd. Brine strength is expressed as the percentage of salt in the moisture (SM) of the curd or cheese, for example, Cheddar cheese containing 1.7% salt and 36.0% moisture would have salt in the moisture concentration of:
It should be noted that in low concentrations (less than about 2% SM), salt acts as a microbial stimulant but at higher concentrations has a definite inhibitory effect. Starter bacteria are progressively inhibited as the brine strength increases and total inhibition occurs at about 6% SM. However, salt tolerance of bacteria varies and unfortunately some which may cause cheese defects, for example, coliforms, can withstand quite high concentrations of salt. Mucor or black moulds like to grow at low levels of salt in moisture.
When dry salt is applied to milled curd, some of the salt dissolves in the moisture on the curd particles and diffuses into the curd. This causes whey to flow out of the curd and the outer curd layer to shrink. The free whey dissolves some of the remaining salt crystals and these either diffuse into the curd or is lost in the whey. This salty whey is high in fat content. This is thought to occur through the abrasive action of the salt and through curd contraction.
If salting, mellowing (time between salting and pressing) and pressing are properly controlled, the cheese should have a uniform salt content 3-4 days after pressing.
Allowances need to be made when dry salting cheese, for a percentage of salt to be lost in the ‘salty whey’ that comes out of the cheese when salt is added.
Some cheese varieties eg eye-type cheese, hard grana, Edam and Gouda and even white mould are salted by immersion in a sodium chloride brine solution. When brines are used, the following principles should be followed.
brine storage baths should be made from a non-corrosive material
The mechanism of salt uptake is similar to that of dry salting that is, salt is taken up from the brine, and whey (moisture) is expelled from the cheese. Variation to salting rate can be achieved by:
Salt quality and types
Several types of types of salt can be used on cheese. Salts can be very ground, fine or coarse grains, in rock form, Kocher, pickling salt, sea salt, flake salt. Some salts have different densities. Many salts have iodine so definitely avoid those, anti-caking agents are common in many salts but are less of a problem. Salt must be free from insoluble matter (dirt) as this will add extraneous matter to the cheese. Some gourmet salts can produce an off flavour that is the result of the fat oxidation reaction with the naturally high iron levels in these salts. Salt should be stored in a dry environment to prevent ‘caking.’
What is marinated cheese?
The naming of these style of cheese can be quite ambiguous, it can be called Goats Feta, Persian Feta, Marinated Feta, Gourmet Feta, Greek Feta in Oil, or any mixture of these words. For this article, we will call it marinated cheese. Marinating cheese is becoming a very common style cheese. Typically, the cheese is added to a jar with oil plus some herbs and then stored in the fridge. The cheese component does not usually require complex cheeses, the product relies heavily on the oil and herb marinate to create a very nice flavoursome product.
But there are some misconceptions around the manufacture of a marinated cheese. There are several points that you should understand if you are making a marinated cheese. Here is some information on some of the variables used to make this cheese:
Food Spoilage v’s Food Poisoning
Food poisoning and spoilage are two different things, which affect the final quality of the foods we eat. Food spoilage refers to spoiled food, which is unfit for consumption eg it has gone mouldy, curdled, smells foul, is rotten etc… While food spoilage often there are tell-tale signs that it is spoiled so it is discarded before being eaten.
Food poisoning refers to the condition affecting a person’s health due to consumption of spoilt or contaminated food. Symptoms include diarrhoea, vomiting, nausea, headaches, cramps in the stomach and in extreme cases hospitalization and even death. Unfortunately, food poisoning usually does not have tell-tale signs in the food. You cannot smell, taste, or see food poisoning.
The equipment and the process
Make sure that all your equipment is well sanitised. This is the same for all your cheese making, that should not change between different cheese. But some specifics for the marinating step includes cutting boards, knives, jars, lids etc, that will eventually come into contact with either the cheese, the oil or the herbs. All equipment should be thoroughly washed then sanitised. Sanitising can be achieved by a chemical sanitise or by a very hot water sanitise.
The cheese can be rennet set or acid set. Marinated cheese is often a fresh lactic acid set cheese. It has a low volume of rennet compared to many cheese, it is incubated with a mesophilic culture at ambient temperature for upwards of 16 hours. Some cheese is drained in a cloth/bag and reformed in hoops and some cheese is added straight into hoops and then straight into the oil marinate. The endpoint of incubation is the key to safety for this cheese. A minimum pH of 4.6 is required for all cheese to be marinated, this is the point the liquid milk sets into an acid curd. The cheese is quite acidic at this point, it is much like the pH of yoghurt. If all the correct hygiene practices have been followed up to this point, a pH of 4.6 for the cheese, excluding the herbs and oil, should not allow the growth of food poisoning bacteria within the cheese itself. Simply the cheese will not support food poisoning.
There are many options for the herbs that you can use to flavour your oil. Thyme, rosemary, bay leaves, dried chilis, peppercorns, citrus zest… The list goes on. But how you obtain and treat those herbs is important. Do they come fresh from your garden, fresh from the supermarket, or do you obtain prepackaged from the supermarket? Some herbs and spices imported into Australia are treated with ethyleneoxide (EtOH) to control microbial contamination and this makes them safe. So, shop purchased dry packaged herbs may be considered free of food poisoning bacteria. But fresh herbs cannot be considered this way. It is this step, the addition of herbs, that is the weakest link in keeping marinated feta free of poisoning bacteria. The following link: https://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/ProducePlantProducts/ucm337088.htm provides a very comprehensive document for the treatment of fresh herbs. It is nearly 200 pages and covers the best practices for processing of fresh culinary herbs, everything from growing, picking, transportation, washing, storage etc It is a very comprehensive document.
If there are best practice guidelines for commercial operations that are very comprehensive and aimed at significantly reducing the risk of food poisoning, it is conceivable that cheesemakers may not have the means available to follow all these guidelines when adding fresh herbs to a cheese or oil. Fresh herbs are desirable because they have the colour, flavour and are more attractive to use than dried herbs. But fresh herbs can significantly increase the risk of food poisoning. So how can you make fresh herbs safe? The simple answer is you cannot. However, this is how I go about this process. Please note I am offering this as my personal method of sanitising the fresh herbs and in no way am I advocating this process to you. This process has not been validated scientifically to ensure it reduces the risk of food poisoning.
Only the freshest oil should be used for marinating. The oils added to the cheese vary in flavour from canola, macadamia, rice bran. Basically, you can use what oil you like. Olive oil is a great oil, but it solidifies at fridge temperatures, so it is not commonly used. The fresh lactic cheese also has a light delicate flavour and the olive oil tends to dominate the fresh cheese flavour. Oil has been used for thousands of years as a preservative, keeping foods from oxidising and desiccating. When olive oil is old, it oxidises and becomes rancid. That’s food spoilage.
There is no pH value of oil because it doesn’t have one! pH is a measure of the hydrogen ion concentration in an aqueous solution(water). Because there is no water in oil, there is no pH value. Most bacteria can not grow in the oil itself, garlic is an exception (see garlic below), they require a watery medium. Additives such as cheese and herbs will, however, supply that watery medium that is important for microbial growth.
Importantly oil provides an anaerobic environment, it has no oxygen to support the growth of many different types of bacteria. But there are still certain types of microbes, that will grow in anaerobic conditions. This means that oil can create an environment that will support bacterial growth. Some of the bacteria capable of growing in this environment are capable of very severe food poisoning. Thus, the refrigeration of a marinated oil/cheese/herbs mix is vital. The aim of refrigeration is to create a hurdle to the potential growth of any food poisoning bacteria that may be present.
Botulism: Garlic in oil
Garlic, onions, shallots, and leeks are grown under the ground and consist of pungent flavoured bulbs called cloves. In the ground where these bulbs are grown, some of the most dangerous pathogenic microbes also reside. Regardless of its pungent flavour garlic is a low acid vegetable. Garlic has a pH of around 5.3 to 6.3. It is often incorrectly categorized as having antibacterial qualities. As with all low acid vegetables, garlic will support the growth of Clostridium botulinumand if, given the right conditions, garlic will support the production of a toxin from this bacterium called Botulism, it is the most severe neurotoxin available. It can cause paralysis or even death. It’s is my understanding that Clostridiumbotulinumcells from the soil can become encased within the garlic as it grows. Sanitising the surface of the garlic or removing the shell of the garlic will not necessarily remove all the live bacteria. The Clostridium botulinum spores and the Botulism toxin can also survive a heat treatment far greater than what milk pasteurisation will provide.
Oil in a jar is exactly the type of environment that Clostridium botulinumcan grow in, it is a low oxygen or totally depleted of oxygen environment. If you add garlic to that oil, you are potentially adding Clostridium botulinumto the oil. Roasted garlic may offer some protection, but it is also my understanding that even the roasting may not kill off the spores. Clostridium botulinumwill not grow in the actual cheese if it is pH below 4.6, or in the fridge below 4°C, so the cheese for marinating should be below pH 4.6 and refrigerated. But the safest strategy is simply don’t add garlic, raw or roasted to oil.
Pasteurisation of milk is a process used to heat raw milk to make it safe for human consumption. It is aimed at destroying all of the pathogenic or disease-causing bacteria that are in raw milk. It follows on that cheese made from pasteurised milk should also be free from these same pathogenic or disease-causing bacteria. That is providing the milk was pasteurised correctly and there is no recontamination of the milk or cheese with pathogens post the pasteurisation process.
There are three commonly used heat treatments that can be applied to milk to pasteurise it to make cheese:
As a cheesemaker you may want to know that the pasteurisation process can affect milk that is used to make cheese. The main areas are:
Achieving a good set of your milk is one of the most important steps in making cheese if you want to make good cheese. But it can also be one of the most frustrating. There are several practical considerations that the cheesemaker needs to be aware of that can affect how well the rennet will work when it is added to the milk to make cheese.
Background to forming a cheese curd
A key part of making cheese is forming a curd. A cheese curd can be formed by either the addition or production of acid in the milk, this is an acid set cheese. Yoghurt, Persian feta and some Mozzarella types are good examples of these. The second way a curd can be formed is by the addition of rennet and is called a rennet set curd. The vast majority of cheeses that you will make and eat will come from rennet set curds eg. Cheddar, Camembert, Blue Vein, Gouda and so on.
What is happening when the rennet forms a curd?
Rennet is an enzyme that coagulates the milk, basically it turns the milk from a liquid to a solid. Chymosin is the active enzyme in the rennet that does this. When rennet is added to the milk (see foot note) it needs to be stirred in very well, the milk is then left undisturbed for a predetermined time, usually from 30 – 60 minutes depending on the type of cheese and the recipe. During this time the Chymosin cuts (cleaves) off the casein portion of the protein from the other proteins (whey proteins) in the milk and the caseins then all bond together into a fibrous structure referred to as a gel. The gel grows in strength during the set period. This gel now contains most of the milks components: fat, casein, calcium, starter cultures, some water, and some of the chymosin itself.
What are the Practical considerations for the cheesemaker?
The formation of this gel is when a cheesemaker may experience differences in how well the curd will set. A cheesemaker requires the gel to be a certain strength (referred to as being set) before the curd can be cut and then stirred. If the set is not strong enough at the cut stage, the finished cheese may have inconsistencies and it may turn out as an inferior quality cheese. A curd that is too soft will not drain sufficiently and will make a cheese that is over moist, over acid and with a weak structure. A curd that is over set will produce a cheese that is too firm, too dry and will not ripen adequately. The issue for the cheesemaker is that all milks do not set exactly the same so it is important for the cheesemaker to understand that there are several variables that may affect how well a cheese is going to set. Understanding these variables will assist you with dealing with the problem for the current batch and or future batches of cheese.
Factors to consider when handling your rennet:
Foot Note: Many people use the practice of diluting their rennet in 20 times the volume in distilled or boiled cooled water. This is not necessary for rennet’s that are up to 200IMCU strength. What is important is that the rennet is added over the length of the cheese vat and stirred in very well and the milk is then left undisturbed to set.
Cheese comes in lots of different colours. The addition of colour to cheeses was historically quite common but in the last 30 years its use in cheesemaking has dramatically decreased.
Colour was added to cheese for cosmetic reasons, to give an appealing brilliant yellow colour. There is no actual functional use in adding colouring. The natural yellow colour in cow’s milk cheese comes from the carotene in the cream. When the cheese is made the loss of the whey concentrates the carotene and leaves a colour darker than the original milk.
Cows are the only mammal with yellow milk. Cheeses made from sheep, goat and buffalo milk are white. These animals have an ability to synthesise the carotene in grass whereas a cow cannot. Cows fed on dry feed during cold winters and housed in barns will also have whitish milk compared with cows that are free ranging, who will have more yellow colouring in their milk. Breeds such as Jersey and Guernsey will have a more yellow milk than say a Friesian cow.
Annatto is the most common colour used by cheesemakers. It is derived from the berry of the annatto tree (Bixa orellana) which grows in the rainforests of Central and South America. The English Red Leicester cheese which is red in colour has approximately 20 – 30 times more annatto than a Cheddar cheese.
If annatto is to be used, it is added to the milk when the bacteria or starter culture is added but before the rennet. It is difficult to determine if a colour has been added just by looking at a cheese. Most cheesemakers choose not to add annatto at any time, preferring to display the natural colours of the cheese. Some cheesemakers will add it all year round for uniformity and some add it only when the cheese milk becomes light in colour (eg when the dry winter feed produces pale coloured milk).
If making port wine cheese, there are a number of ways to get the port wine colour (and flavour) into the cheese. The most common way is to spike some holes into the matured cheese, and soak the cheese in Port wine for several days. However an unattractive brown earthy colour sometimes appears and not the rich red port colour. This can be remedied by adding a small amount of beet dye to the port before the soaking begins.
Other ways to change colours of a cheese
In Sage Derby a green vegetable dye and dried sage herb is added to the cheese just before the curd is hooped. The colour only adheres to the surface of the curd particles to give a mottled green effect.
Naturally smoked cheeses will have a bright yellow to brown colour as a result of the heat, smoke and some drying of the cheese. Inconsistencies in naturally smoked cheese are very normal.
The red, orange or brown and sometimes neutral colour from washed rind cheeses comes from the brevibacterium linens bacteria that is washed onto the surface of the cheese which breaks down the proteins into desired flavours.
Herbs, grape skins (marc) husk and alcohols such as wine, beer and spirits can be used to wash the outside of cheese. Sometimes cheeses are soaked in these solutions for several days. The solution is usually diluted with distilled water and a small percentage of salt added.
With the release of the first raw milk bleu vein cheese made in Australia (Udder Delights King Saul), it is probably timely to cover the issue of pasteurisation of milk for home cheesemakers. This article is not about the pros and cons of using either raw or pasteurised milk it is about how to pasteurise raw milk in a home situation.
The government in Australia requires that milk is pasteurised and milk products such as cheese be made from pastuerised milk. There are a few exceptions for some imported cheeses and a few Australian made cheeses such as King Saul and for raw goat milk in a few states across Australia.
However the law does not require milk produced from your own cows and goats, intended for home consumption, to be pasteurised.
The reason for pasteurisation is that raw milk is a rich product that supports the growth of a large number of microorganisms. The milk as it comes from the cow’s udder is almost sterile and it picks up numerous microbes on its journey through the cold chain. The environment where the milk is produced on the farm has numerous microbes: some may be pathogenic or disease producing, some may be spoilage and some may be beneficial bacteria required to make raw milk cheese.
Some of these microbes will find their way into the milk. Unless you have access to a laboratory you will not know which type and how many microbes are actually in the milk.
The temperatures used to make cheese requires the same milk to be held for up to a few hours at temperatures between 20°C and 40°C where any microbes (the good, bad or pathogenic) can grow and multiply. If a significant number of disease producing bacteria grow they can potentially cause serious illness to those persons consuming the cheese.
Time and temperature treatments for milk pasteurisation
Pasteurisation requires the milk to be heated to a time and temperature combination that will destroy the pathogenic microbes in the milk. Unfortunately the good or starter bacteria will also be destroyed. Starter cultures are added back into the pasteurised milk as a replacement for the ones destroyed by pasteurisation.
There are numerous pasteurisation time and temperature combinations available but the four most logical treatments for use by home cheesemakers, based on the equipment most people will have available are:
69°C for 1 minute
68°C for 2 minutes
66°C for 5 minutes
65°C for 10 minutes
By properly pasteurising milk you will:
Destroy all pathogenic bacteria and make the milk or cheese safe for human consumption
To destroy some of the spoilage bacteria and enzymes and therefore improve quality of the cheese
Increase the shelf life of the milk
How to batch pasteurise at home:
In the batch pasteurisation process the milk is placed into a pot and heated, usually on a stove top to one of the required temperatures. Some people will do this by placing the pot directly on the heat source (eg stove top) and others will place the milk in a double boiler.
The latter has a less severe effect on the milk and is the preferred approach. The milk will need to be stirred continuously but very gently while it is being heated. When the required temperature is reached heating should be stopped.
A warning note: The above time temperatures are the minimum required to pasteurise the milk for making cheese however additional time and temperatures are also not desirable as they may cause some damage to the milk constituents and make cheesemaking more difficult.
When the maximum temperature is reached, the milk will need to be held for the required time, and cooling commenced immediately. Do not continue with a higher or longer heat treatment thinking it is better. Be aware that the pot and the stove top will also contain residual heat and this may alsocause the milk temperature to continually rise past the minimum temperature.
When the holding time is reached continue cooling the milk straight away, do not delay the cooling so be prepared. You will need to have a supply of cold tap water or refrigerated water to start the cooling process. A sink, a bucket or an outer boiler can be used to hold the cold water. Ice or refrigerated water can be used, it is beneficial but it is not necessary.
You will find that the cooling water in the outer jacket will increase in temperature and will need to be discarded for a new batch of cooling water. Most damage to the milk is done while it is above the 55°C temperature, so it is desirable to cool the milk down below this temperature as quickly as possible.
Continue cooling the milk until it reaches the desired cheesemaking temperature. You are now ready to start making cheese. The same time and temperature standards apply to milk from cow, goat, sheep and buffalo.
Pasteurisation will cause calcium precipitation so it is helpful to add calcium chloride to the milk as soon as it is cooled to cheesemaking temperature. Pasteurisation may extend the time taken to coagulate the milk, give a softer curd and make drainage of moisture from the curd more difficult.
If you want to make cheese, you have a choice of using either homogenised or non-homogenised milk. Fifty years ago the only options were raw or pasteurised milk; homogenised milk was not readily available. Now the situation has reversed, it is a little harder to find non-homogenised milk, but most states in Australia have several dairy farmers that are turning the milk from their own cows into pasteurised but not homogenised milk.
When you purchase milk from a supermarket, quite often the only choice is pasteurised homogenised milk. Homogenisation and pasteurisation are two very separate processes. The law requires all milk sold in Australia to be pasteurised milk; it is illegal to sell non-pasteurised or raw milk. Homogenisation is optional as long as it is declared on the label of the bottle or carton.
If you want to make cheese, you have a choice of using either homogenised or non-homogenised milk. Fifty years ago the only options were raw or pasteurised milk; homogenised milk was not readily available. Now that the situation has reversed, it is a little harder to find non-homogenised milk, but most states in Australia now have several dairy farmers that are turning the milk from their cows into pasteurised but not homogenised milk. I use only non-homogenised milk at the Intensive Cheesemaking and Intensive Yoghurt Making courses.
So, which milk should you choose to make cheese?
The answer is non-homogenised milk. Why? Let’s start with an explanation of why milk is homogenised. Homogenisation came about because the public wanted the cream evenly distributed through the milk as opposed to having the cream layer at the top, where the bottle or carton had to be shaken before being poured. A secondary effect of homogenisation is that it generally lasts a few days longer than non-homogenised milk. Initially homogenised milk was met with scepticism but now it is readily accepted.
Milk is homogenised by passing it through very narrow openings under very extreme pressure. These openings are called homogeniser valves. These valves shatter the fat and proteins in the milk into billions of much tinier pieces. The cream can no longer rise to the surface and is evenly spread through the milk. That the fat globules have been broken up does not affect the cheese. The flow on effect for cheesemaking is that the very high pressure of homogenisation also breaks up the proteins into much smaller pieces. These proteins are needed in their “whole form” to turn the milk into a curd when the rennet is added or the curd does not form properly. Homogenised milk will still form a curd but it is a very weak and the resulting cheese is much lower quality. It is for this reason that commercial cheese manufacturers the world over do not use homogenised milk to make cheese.
There are a few minor exceptions where you can use homogenised milk to make cheese. Both homogenised and non-homogenised milk can be used to make Ricotta. Homogenised milk can also be used to make gourmet feta because it requires a soft curd.
So if you want to make good cheese, use non-homogenised milk. If you want milk with a full flavour and lots of body use non-homogenised milk. Don’t let anyone tell you otherwise.
Salting involves the spreading and distribution of salt through a cheese. There are two ways to add salt to cheese: by immersing the cheese into salt water, which is called brining or by physically or mechanically adding the salt to the surface of the cheese which is called dry salting.
There are several key reasons that salt is added to cheese and all are very important for the quality of the finished cheese:
Alters the texture and appearance
Slows down or stops lactic acid fermentation
Controls enzyme activity and subsequent breakdown of fats and proteins
Suppresses the growth of spoilage bacteria
Aids moisture control
Brining is the immersion of the whole cheese in a sodium chloride solution. Most brines are around 20% – 27% salt content. Once 27% salt is reached that is called the saturation level for salt in water. Brining is thought to have come about because if dry salt was not available then partially evaporated sea water would serve the same purpose.
When brines are used, the following principles should be followed:
Brine storage vessels should be made from non-corrosive material
The volume of brine should be at least 1.5 times the volume of cheese
The amount of salt to be added is calculated from the desired brine strength, for example 20% brine for white mould cheeses
If reusing a brine, the salt strength should be monitored and salt needs to be added to ensure concentration is maintained
The pH and calcium content of the brine must be maintained so that these two components roughly equal the same level as the cheese
Ideally brines should be refrigerated between uses but also ensure they are handled correctly as they are very corrosive
The mechanism of salt uptake of salt from the brine to the cheese is similar to that of dry salting.
The salt that is taken into the cheese from the brine and whey (including moisture and some minerals) is then expelled from the cheese into the brine. This transfer is not always even, as a general rule two grams of water is lost from the cheese into the brine to every 1 gram of salt taken up by the cheese.
A variation in salt uptake means that different styles and sizes of cheeses will require different amounts of time in a brine.
Variation of the rate that salt is taken into the cheese can be achieved by:
Different concentrations of brine (20% salt v’s 27% salt)
Length of time the cheese in the brine solution
Moisture content of cheese
Temperature of brine
Surface texture of cheese
Surface area, size and shape of cheese;
Agitation of brine solution
Hardness of the cheese
Fat and protein content of the cheese
Making and using a salt brine
The water used to make up the initial brine should be straight from the tap and heated to at least 80c to kill any unwanted bacteria and the salt should be added to the hot water. The salt for making up a brine does not have to be premium fine cheesemaking salt, as this type of salt can be expensive. The cheapest non iodised supermarket salt is suitable. The salt should also ideally be free from foreign matter, however if the salt does have foreign matter it will be rendered safe by the hot water and the salt.
When a salt brine is first made up it is necessary to add approximately 1ml of acetic acid and 1ml of calcium chloride for every litre of water so that the acid and calcium levels of both the brine and the cheese are equal. The purpose of adding CaCl to the brine is to maintain the same concentration of calcium in the brine and in the cheese – if the calcium concentration is too low in the brine then calcium will move from the cheese to the brine to establish equilibrium concentration in the brine vs the cheese. If the calcium leaves the cheese then the cheese will go soft.
When the cheese is sitting in the brine, it is ideal to sprinkle a pinch of salt over the surface of the cheese that is protruding from the brine. The cheese should be turned 180 degrees a few times during the brining process.
It is ideal to reuse a brine as it builds up with substances such as lactic acid, proteins, minerals, lactose and moisture from the cheese however many people will not have sufficient space to store their brines in a refrigerator between use. If reusing a brine any floating pieces of curd should be removed before use.
The size that you cut the curd will affect the moisture and characteristics of your cheese.
The cutting of the curd that has been formed after the addition of the rennet is one of the most critical aspects of cheesemaking. Cutting is the start of the dehydration process and will affect the final moisture, acidity, maturation rate and yield of the cheese. All of which are very important factors that distinguish the exact characteristics and quality of a cheese. After the curd is cut it holds the main constituents of the cheese which are the fat and casein plus it also contains some water, minerals, whey, starter culture and rennet. The constituents that are lost in the whey are the water, lactose, whey proteins, some minerals and a small amount starter culture. The term used to describe the loss of these components is called syneresis.
The volume and the amount of these constituents that are either retained in or removed from the curd are very closely related to the surface area of the curd particle after it is cut. The general rule is that the smaller the size of the cut, the greater is the surface area of the curd and the greater is the loss of components into the whey.
To show this: If we started with 1 litre of milk and added rennet so that it formed a cube of curd. We would have a 10cm cube of curd; the surface area would be 600cm cm² (6 sides to a cube). If that cube of curd was cut into 1cm cubes (Cheddar cheese is cut to this size), then we would have 100 cubes with a surface area of 6000cm². If we cut those 1cm cubes into 5mm cubes then we would have 8000 cubes of curd with a surface area of 12,000cm². Simply put the more surface area means more loss of whey and constituents into the whey.
Different cut sizes for a few cheeses may be:
· Parmesan styles 2 – 3mm
· Cheddar 8 – 10mm
· Camembert 12 – 15mm
· Persian feta very large pieces
I receive regular emails from people that have been using their thermometers for fairly long periods of time but they are not sure if they are working correctly. Checking your thermometer is something that you should consider doing every several batches of cheese. It is very simple and quick to do and can give you good peace of mind.
How do thermometers become incorrect?
Regardless of how much you spend on a thermometer, $10 or $1000, they are all capable of providing an inaccurate reading. Inaccurate readings can be caused because it was dropped, you changed a battery or it’s just one of those electrical/mechanical things that happens from time to time. If you are using a non-water resistant or non-water proof thermometer to make cheese then the electrics of the thermometer may be starting to deteriorate due to water damage of the internal components.
What is a satisfactory level of accuracy for a thermometer?
For most people making cheese at home, you should be happy with your thermometer if it is within +/– 1°C or even 2°C of a true and correct reading. However if your thermometer is out by any more than this it may affect the quality and consistency of the cheese you are making.
How do I check the level of accuracy?
There are two standard methods that you can use at home to check your thermometer. The Ice Bath or Freezing Point method and the Hot Water or Boiling Point method. You can check your thermometer by using either or both of these methods. If you are making yoghurt or ricotta where you are heating the milk to i.e. 90°C then the hot water method is best for you to use. If you are using cheesemaking temperatures around 30°C then the ice bath method is best to use. If you are using both high and low cheesemaking temperatures then use both methods. It does not take long and it’s a good idea to check your thermometer against both methods.
The principle of these two methods is that a pure ice and water mixture will hold its temperature temporarily at 0°C and that pure water will boil at 100°C. If your thermometer is placed in either of these mixtures then ideally it should read the same temperature as the water bath. A description of the 2 methods follows:
Ice Bath method
Materials needed: 1 litre clean and dry container (glass or plastic), 300 grams of crushed ice (not ice cubes), 200 ml of the purest water available (filtered water is best but tap water is ok providing it is not overly hard with minerals), thermometer/s to be checked
Immerse the thermometer probe by more than half way in the ice and water slurry. The mixture should be a slurry and not have large chunks of ice. Hold the thermometer in the ice water bath and move it around in a stirring action without touching the sides of the water bath. Do this until the thermometer reading stops moving. The reading on your thermometer will show how accurate your thermometer is (it should read 0°C).
Boiling water method
Materials needed: Approximately 1 litre of the purest water available (filtered water is best but tap water is ok providing it is not overly hard with minerals), a 1.5 to 2 litre saucepan, thermometer/s to be checked.
Add the water to the saucepan and place on the stove top until water boils (when there are bubbles rapidly rising to the surface, not just simmering). When boiling commences turn the stove top down to its lowest setting but be careful to make sure that the water is still boiling. Immerse the thermometer probe by more than half way into the boiling water. Move the thermometer around in a stirring action without touching the sides of the saucepan. Do this until the thermometer reading stops moving. The reading will show how accurate your thermometer is (it should read 100°C).
How to adjust the thermometer if the reading is inaccurate?
Not all thermometers can be adjusted. Both of the thermometers that I provide on the Cheesemaking Shop are waterproof and have an ability to be calibrated by the freezing point or boiling water method. Manufacturer’s instructions are provided with each thermometer. When you test your thermometer and it is out by i.e. 2°C then you can adjust the thermometer by holding down the calibration button on the thermometer. If your thermometer is not adjustable then then next time you make cheese just add or subtract that difference each time you take a thermometer reading when you make the cheese. If the thermometer is out by more than 2°C you can still do the addition or subtraction, but it is probably time to look at replacing your thermometer
The purpose of pressing and moulding of cheese is to:
Produce the desired size and shape of cheese
Form all of the individual particles of curd into one cheese that can then be ripened, packaged and stored
Speed up removal of free whey
Consolidate the curd by removing the air and spaces between curd pieces
Create the initial stages of rind formation
The main variables that need to be controlled during pressing are the amount of pressure applied to the cheese, how fast pressure is applied, the temperature of the cheese during pressing and the length of time the cheese is pressed.
The amount of pressure
Some cheese such as fresh acid, blue mould and white mould; the curd is moulded and no pressure is applied, the cheeses are simply turned 180 degrees and allowed to be pressed under their own weight. Cheese such as Cheddar and Emmenthal are pressed at high pressures for several hours. In the case of eye-type cheese, prepressing may take place under the whey, usually after the curd is placed in the mould. Other cheese such as Tilsit and Havarti with some eyes and openness only have a moderate amount of pressure applied.
Applying pressure slowly
Pressure must be applied gradually to ensure that whey and air can escape through the natural channels between the curd pieces before pressure builds up sufficiently to close off the channels. 30 – 60 minutes is sufficient time before the full pressure is applied.
The temperature of the curd
The curd needs to warm when it is placed in a hoop just prior to pressing. Curd particles that are cold or have dried out will be hard and will not matt together sufficiently. If curd is salted prior to hooping (eg Cheddar) then the curd needs to be kept warm to allow the salt to slowly diffuse into the curd for approximately 10 minutes prior to being moulded and pressed. The curd should be kept warm while it is in the press.
The length of time the cheese is pressed
Pressing time can vary from 30 minutes to 24 hours. Pressing needs to be applied slowly at first and then gradually increased. This allows air and moisture to move from via natural channels from the inner to the outer layers of the cheese. Pressing at a too fast rate may close these channels and trap air and moisture in the centre of the cheese. The cheese hoop or mould should be lined with a cheese cloth, which can be made of cotton or synthetic material (blue cheese cloth) to aid in drainage of whey and to produce a smooth close surface finish. Once the cheese has been pressed, it is usually taken from the press after about 30 – 60 minutes, to straighten the outer cloth so an even surface results on the finished cheese. The cheese is then usually pressed overnight. The following morning the curds have cooled considerably and ‘set’ so additional pressure should not be applied the following morning. Keeping the curd warm after pressing is important especially on cool days. .
There are a large variety of cheese presses used by home and commercial cheesemakers. Pressure can be applied by hydraulics, spring or by vacuum.
Have you seen those small white crunchy specks on and in hard cheeses such as Cheddar and Parmesan? They are called calcium lactate crystals. They are part of the cheese and they are harmless. They are usually pin head size and some cheeses have a few and some cheeses have lots.
These crystals are often sought out by connoisseurs of such cheeses as being indicative of a mature cheese with a strong flavour, but they are also misunderstood by others as being foreign matter or extraneous to the cheese. Calcium lactate is formed as the lactose in serum (residual moisture in the cheese) is turned into lactic acid as the cheese ages, the casein bound calcium is released into the serum and this combines with the lactic acid to form crystals over several months. There are several factors that may cause these crystals, the main ones are too much acid and too much moisture in the cheese. Other factors include slow cooling and high maturation temperatures.
The big question: If you could purposely make a cheese with Calcium Lactate Crystals would you?
There are many famous cheeses around the world that have ash added to them. Sainte Maure, Morbier, Valencay, Selles ser Chur, plus local cheese such as Meredith Ashed Chevre and Yarra Valley ashed pyramid are just a few. But why is ash added to these cheeses? It is tasteless and odorless!
For thousands of years ash was used as a preservative, to stop lumber from rotting, bodies from decomposing, preserving food and water on long sea voyages, filtering muddy water, controlling odours and as a powerful medicine. Cheese also needed to be preserved especially as there was no refrigeration or the advantages of modern packaging. Originally ash was obtained from burning oak branches, grape vines or local timbers. The ash was sprinkled on the surface of the cheese often in conjunction with salt.
There are five main reasons why ash was added to the surface of the cheese:
1. To decrease the acidity of the cheese. Where the cheese has a high acidity, such as fresh acid cheeses (cheese made without the use of or minimal use of rennet; most of the cheeses mentioned above are this style) the ash will neutralize the surface acidity. The surface flora required of those cheeses, some added to the milk and some occurs naturally, do not grow well in very acid environments but will grow earlier than would be expected if ash is added and results in a more complex micro flora of the final cheese. The ash in this situation also restricts the growth of unwanted micro flora
2. To absorb surface moisture. The surface moisture reduces the hardness of the rind. The rind is the hardened surface of the cheese and is important to protect the cheese inside from drying and physical damage. So if moisture is soaked up soon after manufacture then the hardened rind will be able to preserve and protect the interior of the cheese
3. The addition of salt in conjunction with the ash also aids in assisting points 1 & 2 above
4. Purely cosmetic. With modern packaging and refrigeration and controlled environments the need for ash to preserve the cheese is reduced or not even required.
5. Tradition. Tradition does not need to be lost just because of modern technology. This ash has been used for centuries and is as much as a characteristic of the cheese as the cheese itself. We need to these traditions to be preserved plus the ash is an instantly identifiable characteristic of those cheeses.
Ash is technically known as Activated Charcoal. The word “carbon” comes from the Latin word for coal. Graphite, the most thermodynamically stable form of carbon (as in pencil “lead”) is in the ash family as is the diamond.
Charcoal from burning wood in the back yard is not “activated charcoal”; rather it is a raw material for the manufacture of activated charcoal. Commercially cheesemaking ash it is derived from wood, sawdust / wood chip, coconut shells, bamboo and peat. For food grade purposes these timbers are heated to between 600 °C – 1,200 °C which is much higher than a conventional fire or oven can achieve.