The importance of keeping cheese warm during hooping and pressing

Make pressed cheese on a cold or cool day requires some general awareness so that you can modify some parts of your cheesemaking process when undertaking the pressing process

When cheese is pressed, the curd pieces knit together and are formed into the desired shape.  This fusion of the thousands of pieces of curd particles relies on two processes: firstly the curd particles under pressure have to ‘flow’, which causes them to flatten and increase in surface area and then secondly these curd particles have to bond to each other.  When cool or cold or dry curd particles are placed into a cheese hoop the contact area between the curd particles is lessened, basically the curd has become firmer and less resilient to the flow.  The look of a finished cheese that is pressed while cold can be a rough and open texture, both internally or internally with obvious definitions of curd particles instead of a close-knit texture. Conversely warmed curd particles are more resilient and have a better level of distortion and knit together much better than colder curd. The best way to achieve correct pressing on a cool day is to have the room warm, temperatures above 25c are sufficient when you are filling your hoops.  Then the filling of the hoop needs to be completed reasonably quickly, so when the curd is removed from the warm whey it does not have time to cool off or to dry off.

During the actual pressing stage, the hoop full of warm curd should not be allowed to cool, this is especially important for the first few hours after pressing has commenced. This warmth allows the fermentation process by the starter culture to continue which in turn assists syneresis, resulting in an increase in acidity and a decrease in the moisture content of the cheese. Both the moisture and acidity level will be very important attributes for the subsequent ripening process and the final quality of a matured pressed cheese. A cheese that has a higher than expected moisture level will probably have a higher level of protein degradation, higher acidity, possibly producing bitter compounds and a weaker pasty body.

Seventeen variables for the cheesemaker to consider

There are thousands of varieties of cheese made each day across the world. A cheesemaker will start with a vat of milk and by the end of the cheesemaking process a cheese has been made. But why are there so many different cheeses when they are all coming from the one ingredient; milk. What does the cheesemaker do that makes one cheese different to another?

 

The cheesemaker has at least 17 variables under their control, each of which will slightly or significantly influence the type of cheese being produced. When combined, they produce cheese that are sometimes close and sometimes vastly different. The variables include:

 

Variables in manufacture of cheese varieties

 

  • Type of milk
  • Standardisation of fat levels
  • Raw or Pasteurised milk
  • Homogenisation
  • Degree of souring allowed (priming)
  • Starter Cultures
  • Ripening and Flavouring Cultures
  • Amount of rennet used
  • Size of cut
  • Temperatures used in cooking (or no cooking)
  • Amount and speed of stirring
  • Degree of whey drainage
  • Pressing or not pressing the curd
  • Method of salting
  • Conditions and length of curing
  • Use of special bacteria or mould in curing; and
  • Use of additives

 

Type of milk

Milk from different animals will impart different characteristics to a cheese.  Some varieties are only considered genuine when made from the milk of a particular animal (for example, Roquefort from ewes’ milk, Chabichou from goat milk).  Cow’s milk tends to impart a yellow colour to cheese.

 

Difficulty may be experienced in manufacturing a cheese variety from milk other than that traditionally used for that variety (for example, Mozzarella from goat milk).

 

Standardisation of fat

In setting out to make any particular cheese variety the resultant cheese will be different depending on the balance of fat to protein in the milk. The fat content can be adjusted by adding or removing cream. Lower cream levels will tend toward increased hardness of a variety eg Parmesan and Comte. Increased cream levels will tend towards higher fat and higher moisture cheese such as a Brie or Triple Cream.

 

Heat treatment of milk

The use or raw or pasteurised milk often divides the cheesemaking community. Raw milk can only be used to produce certain varieties of cheese, mostly those with protected designations of origin (PDO). Outside of those rules the cheesemaker has a make a significant decision about the safety of the cheese based partly on using either raw or pasteurised milk.

 

Curd from pasteurised milk may tend to be softer, due to precipitation of some of the soluble calcium and it may be necessary to compensate by the addition of calcium chloride before renneting.

 

Homogenising

The disruption of fat globules caused by homogenising exposes a much greater surface area of fat to the action of the enzyme lipase, thereby accelerating the fat breakdown process during cheese maturing. Homogenising also makes milk and cheese feel much smoother, and produces a slightly paler curd.  These factors, and the extra fat breakdown, are all desirable in Blue Vein cheese, where the cream in removed from the milk, homogenised and then returned to the milk.

 

Homogenising is also used for Cream cheese and some soft cheese types.

 

Degree of souring of milk

This may be controlled by varying the amount of starter added or by varying the time between addition of starter and rennet. Some cheese such as Cheddar require only a small amount of souring before the rennet is added and some cheese such as certain blue vein varieties require more than one hour. Lactic curd such as Persian Feta requires several hours. High acidities will favour increased moisture expulsion and firmer curd.

 

Starters

Starters are selected for different cheese varieties for two basic reasons: they must be able to produce, as appropriate, acid, gas and desirable flavours, and they must be able to withstand some of the temperatures which are themselves integral parts of the manufacture methods.  In large eye type cheesemaking (for example, Emmental), the starter comprises several different cultures because of the various stages of manufacture, to produce acid slowly during the early stage of manufacture, and then to withstand the high cooking temperature later in the process.

 

Some cheese varieties such as Ricotta require no starter.  The curd is formed by heating to near boiling and adding an organic acid to complete the precipitation.  The curd rises to the top and is ladled into perforated moulds for draining.  It is the eaten fresh.

 

Amount of rennet

Increased quantities of rennet will tend to produce a firmer curd, with an increased rate of protein breakdown during maturing.  Excess rennet may cause ‘bitterness’.  Some cheese such as Halloumi do not usually require a starter culture but rennet is essential. Some cheese such as Lactic Acid varieties require very minimal rennet, relying on the developed acidity to form the curd.

 

Size of cut

Fine cutting of the curd will favour increased moisture expulsion, resulting in a firmer cheese.  Softer varieties, for example, Blue Vein and Camembert, frequently employ a larger cut to retain moisture.

 

Temperature used in cooking

High cooking temperatures favour increased curd shrinkage to produce firm curd in the whey and in some cases to reduce the levels of undesirable bacteria.  Use of heat tolerant starters ensures that acid production resumes later, and usually continues during early maturing until the lactose is used up.

 

In some fresh, soft, or semi‑hard types where high moisture content is desired (for example Blue Vein, Feta and Camembert) the curds and whey are not cooked.

 

Near boiling temperature is used for non‑cultured cheese where the curd is formed by heat precipitation of the albumin followed by sudden acidification to induce coagulation and flocculation of all the protein (for example, Ricotta).

 

In the manufacture of Gouda and Raclette styles, part of the whey is removed during or immediately after cooking, and replaced by water, either at the same temperature as the vat contents or slightly hotter, in order to reach the final cooking temperature.  The amounts of whey removed and water added can be varied and are used to vary the pH and body of the cheese.

 

The more water is added, the longer the curd remains in the diluted whey, the higher will be the cheese pH, and the weaker the body.  The extra water in the whey surrounding the curd particles causes more lactic acid and lactose, to diffuse out of the curd.  This results in less residual lactose in the curd after whey removal, thereby limiting the extent of subsequent acid development.

 

Degree of whey drainage

The stage and method of whey removal have important effects on the cheese produced.  Early drainage of a soft curd is usually used in making soft cheese types.  Some traditional Camembert only requires the ladling of coagulated curd directly into the moulds, with no cutting, stirring or cooking.  Some feta styles are placed in drainage hoops or trays as soon as the curd has been cut.  Blue Vein requires a short period of agitation and curd firming before it is placed in perforated hoops for draining and matting.

 

Late draining after prolonged agitation, cooking and acid development characterises the making of most firm and hard cheese (for example, Cheddar, Parmesan).

 

For eye‑type cheese, whey drainage is completed only after the curd has been compressed under the whey.  This is necessary to achieve a close textured cheese with no mechanical openings due to inclusion of air during drainage and pressing.  Any mechanical openings in eye‑type cheese will cause uneven and irregular eye formation, a serious appearance defect.

 

Bag draining without hooping and little or no pressing is applied to cheese with no real fused curd structure or shape.  Cheese of this type includes Quark and Cream cheese.

 

Methods used to compact curd

Curd may be salted and pressed without any time allowed for matting (stirred‑curd type such as Romano) or allowed prolonged periods of matting (for example, Cheddar).  Some varieties such as Edam and Gouda employ matting by pressure under the whey to give close textured cheese due to complete exclusion of air.

 

Varieties such as Mozzarella and Pizza incorporate vigorous dry or wet stretching of the matted curd (pasta‑filata process) to impart a smooth velvety character to the curd.

 

Firm cheese varieties employ mechanical pressure to finally mould the finished cheese, while softer varieties frequently rely on no application of pressure.

 

Method of salting

Salt, except in low concentrations, retards or stops bacterial growth, including that of starters, so it is always applied when acid production is sufficient and needs to be moderated.  Salting from the outside, either by brining or dry salting, after the cheese has been pressed, allows acid production, regulated by storage temperature, to continue inside the cheese for some time, as the salt only penetrates slowly.

 

Brine or dry salting aids in forming a rind, by producing a dry salty zone around the outside.

 

The salt content of cheese is controlled by the amount added, when it is added and the time of exposure during brining and by rubbing salt into the cheese.  Some cheese (for example, Feta) are packed, stored, and marketed in brine.

 

Conditions and length of curing

Curing conditions are not means of producing varietal characteristics in cheese.  The object of curing is to allow the cheese to mature at a rate which results in the properly balanced development of flavour and other properties such as mould development and softening.  Cost considerations generally mean that the fastest rate of maturing, which does not affect quality, is used.

 

Generally speaking, cheese of high moisture content and a delicate flavour requires the shortest ripening period.  Fresh cheese such as Cottage and Quark are not ripened at all.  Cheese like Camembert reaches and passes its peak of maturity very quickly.

 

Curing times lengthen as moisture contents decrease.  Romano cheese at six months of age is a moderately flavoured table cheese, but can be cured for 12 months or more and used for grating and cooking.

 

Curing conditions for most varieties vary between 7‑15°C at 75‑80% relative humidity.  These conditions ensure the desired flavour development and prevent mould growth and drying out of cheese.  Mould ripened varieties require high humidity (95%).

 

Use of special bacteria or mould in curing

Under this heading there are several treatments which are peculiar to certain types of cheese, and contribute to their characteristics.

 

Internal mould ripening:  In the various ‘blue’ cheese varieties the growth of Penicillium roqueforti, inside the cheese produces a characteristic spicy, peppery flavour, as well as a distinctive marbled colour.  The flavour is a combination of the mould itself and various fat and protein breakdown products resulting from the actions of enzymes, produced either by the mould and the starter, or present in the milk. The mould may be added either to the milk before setting or to the curd after whey removal, before hooping.

 

During storage, the cheese is usually pierced with thick stainless steel wires to admit air which is essential for mould growth.  The cheese should also have considerable mechanical openness to allow even mould growth throughout.

 

Surface ripening:  The ripening of many types of soft or semi‑hard cheese is aided by enzymes and flavouring substances produced by microorganisms growing on the surfaces.

 

The ways in which these surface growths are induced and controlled are varied, ranging from strictly controlled use of pure cultures to rather ‘haphazard’ arrangements in which many organisms grow either together or in succession during storage.  The use of a high humidity ripening container with even temperatures, often with little or no air circulation is usually necessary to obtain good surface growths.

 

Eye formation:  Although Gruyere and Emmental are the best-known examples of eye type cheese, there are many others, having smaller or fewer eyes; these include Tilsit, Havarti, Samsoe, Gouda and Edam.

 

Successful eye formation depends on the inclusion of organisms in the starter such as propionic acid bacteria or Streptococcus diacetylactis strains. Correct temperatures of storage are also essential.  Large eye types such as Gruyere are usually stored at a temperature around 20°C for several weeks, during which time eye formation occurs, causing the cheese to swell.  When the eyes are the right size, the temperature must be reduced to around 10°C to stop further enlargement of the eyes.

 

Use of additives

A number of herbs and spices are used in traditional cheese varieties.  These are usually mixed with the curd just before hooping.  Whole peppercorns are added to stirred Romano type curd to make Pepato cheese. Leiden cheese is flavoured with added cumin seeds.  Sage Derby cheese has ground sage mixed in with the milled curd. This not only flavours the cheese but also produces a pleasing green veining as each milled curd particle is outlined with a green edge.  It is important to ensure any herbs or spice added to cheese has low bacterial numbers as failure to do so may result in cheese defects.

Enzymes such as lipase are added to varieties such as Feta, Parmesan, and Romano to accelerate the breakdown of fat and produce the required flavour.

The Eight Basic Steps in cheesemaking

Have you ever wondered why each cheese is different?   It gets down to the 8 basic steps in cheesemaking.

The Eight Basic Steps in cheesemaking

Have you ever wondered why each cheese is different? Each variety of cheese made throughout the world has its own definite composition of protein and fat and a moisture content that is regulated by the cheesemaker in the manufacturing process.

There are hundreds maybe thousands of cheese varieties manufactured throughout the world and many times that with different names.  This presents a rather confusing picture at first sight as there are differences in size, shape, colour, body, texture, aroma, and taste.  However, all cheeses, irrespective of origin, are basically closely related in the making.  They are all made using these eight steps, which can be listed when studying cheese manufacture, and these are summarised in the table below.

8 Basic steps in cheese manufacture

Step

Primary purpose(s)

(a) Selection and treatment of milk Ensure cheese of good quality displaying the desired characteristics and uniformity.
(b) Setting the milk Prepare milk for acid or rennet curd formation and the incorporation of suitable microbial cultures.
(c) Cutting or breaking the curd Speed up whey expulsion by increasing the surface area of the curd.  If cooking of the curd is carried out, further whey expulsion is achieved by contraction of the curd, develops texture and establishes moisture control.
(d) Draining Permanently separate the whey from the curds.
(e) Knitting or matting of curd Transform the curd into the characteristic texture and body of the cheese, give time for acid development and aid in moisture control.
(f) Salting Influence flavour, body, texture, and moisture.
(g) Pressing Shape the cheese and close up texture.
(h) Maturation Establish the proper environment for the growth of microorganisms and enzyme activity to transform fresh curd into a cheese of specific flavour, texture and appearance

Getting a crumbly Greek Feta

Summer salads with strong tasty and crumbly Greek feta: Turn that soft east eating Greek Feta into one that is strong in flavour and will crumble into a fresh salad.

Keep starter cultures up around the 3% to 3.5% which is quite high for most cheeses.

Allow approximately 1 hour between starter to rennet and another hour between rennet to cut.

24 Hours after hooping add the cheese to a salt brine for several hours and up to 48 hours depending on your salt tolerances, before vacuum packing and refrigerating for 6 weeks.

Controlling acid development in cheese

Acidity in cheese is a pleasant flavour but it can be too strong at times.   Different cheeses require quite a lot of acid, eg strong crumbly Feta’s, Fresh Acid cheeses, sharp Cheddars and even yoghurt. Other surprising cheeses that only require a little acid include Blue Veins, Edams and Muensters.

Lactic acid is produced by the fermentation of milk sugar or lactose to make lactic acid. To reduce the acidity of the cheese, the ability of the starter culture to produce this acid must be slowed down or stopped. There are several ways that the cheesemaker can do this:

1.       Add less starter at the beginning of the cheesemaking process

2.       Decrease the holding time between adding starter and adding rennet

3.       Decrease the holding time between adding rennet and cutting

4.       Reducing the size of the cut

5.       Increase the speed of stirring and amount of stirring undertaken

Changing the cheesemaking process to achieve the desired result should only be done minimally and would usually include only implementing the above steps one at a time.

Don't let your cheese dry out while draining overnight

When cheese is first hooped it is very moist and needs to be left out overnight and ideally above 20c.  This overnight draining is important to allow the lactic acid bacteria to finish fermenting the residual lactose in the cheese which in turn removes the residual moisture from the curd. Any ripening cultures added to the milk will also continue their established and growth in this phase.

When cheese is first hooped it is very moist and needs to be left out overnight and ideally above 20c.  This overnight draining is important to allow the lactic acid bacteria to finish fermenting the residual lactose in the cheese which in turn removes the residual moisture from the curd. Any ripening cultures added to the milk will also continue their established growth in this phase.

During this time the cheese should also be covered to stop excessive drying of the surface of the cheese.  This is especially important if the cheese is in a room that has a dry atmosphere. In commercial applications cheesemaking rooms can be quite wet from the washing procedures at the end of the day, so there is lots of moisture in the air and on the walls and floors. But in a home situation this is usually not the case.  The surface of a cheese that is left on the bench can soon become dry and discolored.  If the cheese is allowed to dry out excessively on the surface, the following may occur:

  • The skin or outer surface of the cheese will be less impervious to moisture, so removing moisture will be slow resulting in an over moisture cheese
  • Surface bacteria and other moulds (eg white moulds and washed rind cheeses) will not grow well on dry surfaces
  • During brining less salt will be unable to be incorporated into the cheese and you will not know if you have under or over salted
  • In extreme cases the cheese will crack and this may allow unnecessary contamination into the cheese as well as visually not being acceptable
  • Discoloration of the cheese
  • The surface of the cheese may also be tough and leathery

To minimise or prevent these defects the cheese needs to be covered with a moist damp cloth. The cloth needs to be very clean and washed well under running water. It should not be dripping onto or touching the cheese but sitting just above the cheese (usually on the top of the cheese hoops).  A Chux comes to mind for many people and these may work in some situations but they may be a little thin and tend to dry out quickly.  A small sheet of cotton fabric or a folded tea towel will work better.

Keeping cheese warm immediately after hooping

With the colder months of the year here you need to keep your newly made cheese warm at night. The basis is that starter cultures continue their fermentation process for several hours after the curd has been placed in the hoop/mould.  During these several hours the bacteria will ferment the residual lactose to produce lactic acid and this also helps remove the residual whey/moisture from the cheese. The starter cultures require temperatures of around 25c to continue this fermentation.  By leaving cheese that has just been hooped on the bench on a cold day or night you risk ending up with a cheese that is too high in moisture and too low in acid.  Therefore when the cheese matures it will not be true to type and may have off flavours and a soft body. The first few hours after hooping are the most critical as this is the time when most of the post hooping fermentation will occur.

A warm environment for your cheese can be achieved in several ways:

  • Place your cheese on a tray in an oven with very low residual heat. This may be achieved by turning the oven on for around 20 seconds. Ovens are well insulated and hold the heat in well;
  • Keeping cheese in a warm room, if you are warm your cheeses probably is to;
  • Placing the cheese beside a container of water that is heated eg a container with a fish tank heater or beside a slow cooker filled with water and cover with a fluffy towel to lock the heat in
  • On top of your hot water heater system

Place a container of water beside where the cheese is being kept and measure the water temperature to obtain a guide to the cheese temperature.  The cheese should also be covered with a clean damp cloth to prevent it from drying out.

Why use ‘Fresh, Clean and Cold’ milk to make cheese?

Why do you need to keep the milk for making cheese: fresh, clean and cold? At the cheesemaking courses we always talk about the freshest milk and cream will always make better cheese than the same milk or cream that is several days old. You know that refrigerated milk will eventually spoil. The reason is that as milk ages in the fridge bacteria will grow and multiply even if it is kept very cold.  This milk will not go sour as it ages it will go putrid, it has a real ‘yuk’ factor to it.  Technically these bacteria that grow at refrigeration temperatures are called psychrotrophs.

Interestingly enough many of these psychrotrophic bacteria are not usually destroyed by pasteurisation.  They live on in the milk, produce enzymes that digest the fats and proteins in the milk and with that comes flavours that are undesirable in the milk and subsequently the cheese made from that milk.  So if your milk is stored for several days or more, these bacteria will grow and multiply and therefore produce increasing amounts of off flavours that will make their way into the cheese.  Keeping the milk cold will slow down the rate of spoilage compared to keeping the milk at warmer temperatures.

An additional factor related to ‘freshest’ milk is that milk becomes stale as it ages.  That means the great flavour that milk has as it comes straight from the cow diminishes as the milk ages. It does not totally disappear though.

Please note that the bacteria that cause spoilage are not food poisoning bacteria.

The reason for keeping milk clean is that dirty surfaces will allow greater numbers of these undesirable bacteria to get into the milk. Some of these bacteria may be spoilage and some may be food poisoning types.

There reason for keeping the milk cold is that these same bacteria will grow to greater numbers and produce more off flavours at higher storage temperatures.

So what do you need to do! A general industry standard is to give pasteurised milk 10 – 14 days shelf life (usually expressed as a best before date).  If making cheese always select milk that is the freshest available, keep it in a chilled esky for the ride home, especially in summer and keep all equipment and utensils that come into contact with the milk clean and sanitise them before use.

An additional point, the acidity produced by the starter culture that you add to the cheese milk will grow best at warm temperatures and makes the milk sour as lactic acid develops.  The starter bacteria have been specifically selected to make the milk go sour whereas the bacteria that grow because of poor fresh, clean and cold make the milk putrid.

Freezing milk

Freezing any sort of milk will not give you the same quality as if the same milk was used fresh.  Freezing of milk will induce rancidity, make soft sets and give you a lower yield. Where possible always use fresh milk.  If you must freeze milk make sure it is fresh, use very clean and sanitised containers, take the initial heat from the milk with a cooling bath, freeze milk in small lots so that it freezes faster, use the frozen milk within three months and thaw it in the fridge slowly over 24 hours before use.

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