Cheddar Cheese

CHEDDAR CHEESE

Manufacture of cheddar cheese

  • Receiving of milk
  • Preheating
  • Filtration/clarification.
  • Standardization
  • Pasteurization (63ºC/30min.)
  • Adding startercultures (ripening)
  • Adding colour
  • Adding rennet(clotting)31ºC.
  • Coagulation ad setting
  • Cutting
  • Cooking (up to37ºC)
  • Drainage of whey
  • Cheddaring
  • Milling
  • Salting
  • Hooping
  • Dressing
  • Pressing
  • Drying
  • Paraffining
  • Curing/ maturing.

Receiving milk

Only high-grade milk can yield high gradecheese. The quality of finished cheesedepends upon the initial quality of milk from which it is made. Cheese is no better than the milk form, whichit is made.

Successful cheese factories follow a system ofdaily, efficient grading of all milk received. This consist of

  • Determining the odour of milk.
  • Inspecting the appearance of milk ,
  • Determining the sediment
  • Performing MBRT, Resazurin and rennet curd testson the milk.
  • Determining the percentage of titrable acidity.
  • Examining milk for bacteriophage, antibiotics,and inhibitory substances.
  • After the milk has been examined for quality andaccepted, it is weighed, then a representative sample is taken for determiningof fat and casein contents etc.

Filtration and clarification

  • To remove visible dirt in milk . The milk isusually preheated to 35 to 40ºC for efficient filtration and clarification.

Standardization

In cheese making standardization refers toadjustment of the casein/fat ratio in cheese to 0.68 to 0.70. The objectives are

  • To regulate the fat in the dry matter of cheese.
  • To produce the maximum amount of cheese per kg.of fat in cheese milk.

Pasteurization

The usual temperature time employed for pasteurization of cheese milk is holder – 63ºc for 30min. HTST – 72ºC for 15sec.

The objectives or advantages of pasteurizationof cheese milk are

  • To destroy all pathogens
  • To destroy fault producing microorganism.
  • To produce a more uniform product of highquality.
  • To increase the yield.

The chief limitations of pasteurization are

  • It destroys the typical flavour and body ofcheese .
  • It entails a longer ripening period.
  • It encourages the use of low quality milk.
  • It increases the overall cost of cheese making.
  • Homogenization: cheese milk is not normally homogenized.

Addition of calcium chloride

  • Excessive heat treatment of milk causesthe precipitation of a part of calcium salts in milk, this results in slowerrenneting action and a weaker curd, which can be corrected by the addition of0.001 to 0.03 per cent calcium chloride to milk.

Adding starter

  • Ripening or souring of milk refers to thedevelopment of acidity in milk from the time it is received in the vat untilrenneting. In cheese milk, ripening isdone by the addition of starter.
  • The starter is the heart of the cheese. A bad starter is almost certain to give lowquality cheese. A good starter may makeup for other defects, such as contaminated milk; there are different kind ofcheese starters, such as those producing acids, aroma, special effects such as‘eyes’ etc. A cheddar starter usually contains S. lactis and /or S. cremoris .
  • The usual time to add the starter is before allthe milk has been received in the vat. The amount of starter added is to theextent of 0.5 to 1 per cent of the milk, and the temperature of addition is 30to 31ºC. Before being added to the milk, the starter should be examined for itsquality; it should then be stirred until smooth and creamy in consistency; thenstrained and added in the required quantity and mixed thoroughly and uniformlyinto the milk.
  • Ripening in milk is measured by titration,rennet test and pH meter.

Adding colour

  • The colour of cheese is usually analkaline solution of annatto. The colour is usually diluted with approximately20 times its volume of potable water for even distribution. The usual amount ofcolour is 30 to 200 ml or more for 1000 kg of milk.

Renneting

  • Adding rennet to milk in cheese making iscommonly known as renneting or setting.
  • Rennet is the crude preparation or extract fromthe abomasum, rennet contains two principal enzymes viz., rennin, andpepsin. Rennin is an extremely powerfulclotting enzyme, which causes rapid clotting without much proteolysis. On the other hand pepsin induces proteolysisis leading to bitterness in cheese. Rennet is available as liquid or powder or as tablet. Commercial rennet should be stored in aclosed vessel, in a dark room at below 10ºC.
  • Rennet: it is a sulphur containing protein. One part can clot about 5 million parts ofmilk In cheese making one part of liquid rennet (2%) is used for about 5000parts of milk. It is very sensitive to alkali. Heating to 70ºC at pH 6.8 –7.0 will destroy it in 14 minutes.

Factors affecting rennin action

  • Temperature : below 20ºC, rennin is almost inactive; from 30 to 48ºC it is about equallyactive, the optimum temperature being 41ºC. Above 50ºC the activity falls offrapidly.
  • Acidity: the rate of clotting increases rapidly withsmall increase in acidity. Alkalisretard the clotting of by rennet.
  • Calcium ions: coagulation of milk is very sensitive to changesin concentration of calcium ions, it is common practice to add calcium chlorideto which has been severely pasteurized. E.g. at 80ºC for 30 seconds. Thisacts in three ways by lowering the pH value, increasing the calcium ionconcentration and raising the colloidal calcium phosphate content.
  • Inhibitory substances: Many colloidal substances interfere with rennincoagulation e.g. albumin, serum peptones, etc. Albumin and globulin retard coagulation (mastitis milk clots slowly withrennet; the alkalinity of such milk also contribute to this effect.). Boilingof milk resulting in denaturation of the protein removes the inhibitoryeffect. Five per cent peptone almost prevents clotting.
  • Homogenization: This has an accelerating effect on rennetclotting, but decreases the curd tension.
  • Heating the milk: Heat not only destroys rennin but also makesclotting of the milk by the enzyme less easy. The major reason for this is the removal or precipitation of calciumion.
  • Rennet preparations other than calfrennet: Theseinclude goat and lamb rennets, plant enzymes such as withania coagulans, ficus,papain etc
  • Difference in behavior between animal andvegetable rennet: Althoughvegetable rennet clots cow and vegetable milks, animal rennet do not clotvegetable milks even if the calcium ion concentration is raised to that ofcow’s milk.
  • Bacterial rennet: The use of enzymes from microorganisms,particularly aerobic spore formers (Bacillus subtilis) and some of thegram-negative rods (Serratia marcesens) is a fairly new development in cheesetechnology.
  • Adding rennet: Rennet is added when it has been determined thatthe acid is developing at the desired rate. Thus, when making cheese fromripened milk rennet is added when the acdity has increased from initial levelby 0.02 %. The ideal temperature for setting raw milk under normal conditionsis 30ºC and for pasteurized milk , 31ºC. The amount of rennet extract usedshould be such as to form curd that is firmer enough to be cut in 25-30 minutesafter the addition of rennet.

The amount of rennet, which should be added,depends on:

  • Strengthof the rennet
  • temperatureof milk
  • acidity of the milk
  • composition of milk

Usually, liquid rennet is diluted with 20-40times its volume of (potable) water before it is added, to ensure properdistribution for uniform coagulation. The milk is thoroughly stirred during the addition of the rennet andalso for 3 to 5 minutes afterwards. Thevat is covered as soon as possible when the stirring is over, to keep thesurface warm and protect it from contaminating dust particles.

Coagulation

  • This refers to liquid milk changing to asemi-solid junket. The first signs ofcoagulation are that bubbles of air stirred into the milk surface take longerto break and a spatula dipped into the milk and withdrawn shows small flakes ofcurd.

Cutting

  • Thisrefers to cutting of the ‘firm’ coagulum into cubes of a specific size.

When to cut the curd

  • When a glass rod inserted at a 45º angle and lifted straight up makes a clean breakin the curd, it is ready for cutting. Ifthe curd is cut too soon, there will be a lower yield of cheese, if cut toolate, cutting will be difficult and moisture expulsion delayed.

Curd Knives

  • Theseconsist of stainless steel wires or strips, 6 or 9 mm apart, one horizontal andthe vertical.

Method of cutting

  • Thecurd is usually first cut with the horizontal knife lengthwise, then with thevertical knife lengthwise and widthwise.

Syneresis of cheese curd

  • Thisrefers to the expulsion of whey and contraction of the curd. From the cheese-making point of view, thefactors controlling the loss of whey and contraction of the coagulum are:cutting, temperature, acidity, agitation, time and salt.

Behavior of curd after cutting

  • Afterthe curd is cut, whey begins to appear between the cubes and a film begins toform on the outer surface of each cube. This film should not harden, i.e., become firm, too rapidly. Care hasalso to be taken to avoid breaking this film.

Acidity of the curd after cutting

  • Decreasesby 0.05 % to 0.08 % from that of milk at renneting.

Stirring curd after cutting

  • Duringthe first 2-3 minutes after cutting, the curd is not stirred. Then gentle stirring starts. The speed ofstirring increases with the gradual firming of curd cubes. Matting isindicative of inadequate stirring.

Cooking

  • Thisrefers to the heating of curd cubes; it begins within 15 minutes of cutting.

Regulation of heating

  • Theheat is applied slowly to begin with. If the temperature is raised too rapidly,a condition similar to ‘case-hardening’ will result, and the curd cubes will behard on the outside but soft and ‘water-logged’ inside. The rate of heating issuch that the temperature rises to 32ºC in about 15 minutes and thereafter to amaximum cooking temperature (37 to 39ºC) at the rate of 1º C every 4 minutes.

Amount of heat required

  • Thisdepends chiefly on the type of cheese required. For cheddar, a maximum of 37 to39ºC is normal. Too high a temperature can reduce the souring rate and activityof the starter organisms.

Drainage of whey (dipping)

  • Thisrefers to the removal of whey from the curd. When the cubes have been reducedto about one-half of their size at cutting, the acidity approaches a desirablelimit and the cube attain a desirable consistency (elastic feel when squeezed),stirring is stopped and the cubes ‘pitched’. (Pitching refers to the curd cubesdropped to the bottom of the vat and piling them up together). The curd cubes are pushed away from the gateof the vat, a strainer is inserted in the gate, a curd-pail is hung on the curdout let, and the whey is drawn from the vat.

Cheddaring

This refers to the combined operations of packing, turning, piling and repiling the curd cubes.

  • Packing: Afterthe bulk drainage of whey, the curd cubes are kept closely together in twoheaps with a channel in between. This is known as packing and takes 5 to 15minutes after dipping. It results in the formation of two long slabs of curd.These are cut with a cheese knife into blocks or strips 15 to 20 cms wide
  • Turning: As soon as the blocks (strips) of curd can behandled without breaking, they are rolled bottom-side in the vat. This iscalled turning and is carried out every 15 minutes till the curd is ready formilling and salting.
  • Piling and repiling: Within 30 to 45 minutes of packing, blocks ofcurd are turned and laid one over another in twos or threes. This is calledpiling. Then the position of the curd block is altered and this is known asrepiling.

The cheddaring operation usually lasts for twohours or more and is very important not only for moisture control but also forimproving body and texture. Aftercheddaring, the curd becomes drier, more mellow and silky and changes from asorbo rubber-like material to one resembling chicken breast-meat. In the latterstages, it tends to tear apart in fibrous shreds and develops a characteristicnutty and buttery aroma.

Milling

This refers to the mechanical operation ofcutting the blocks of cheddared curd into mall pieces with the help of a cheesemill, with the following objectives:

  • To promote the further removal of whey
  • To enable quick distribution of salt in the curd
  • To prepare curd for pressing into final form
  • And also for de-odourization, cooling of thecurd etc.

Salting: This refers to the addition of common salt tothe curd pieces. Salt in cheese affects flavour, body and texture, and keepingquality. Cheese without salt is often soft, ripen quickly and rapidly developunpleasant flavors.

Objectives

  • For further removal of whey
  • Hardening and shrinking of curd
  • Retarding further formation of lactic acid
  • Checking the undesirable fermentation
  • Produce desirable quality characteristics

Holding before salting: Salting may be delayed ( by more than 15 minutesif needed) when it seems desirable to develop more acid in the cheese curd toencourage further drainage of whey, or to aerate the curd to improve itsflavour.

When done

  • Cheese curd is normally salted
  • About 15 minutes after milling
  • When a hot iron test shows threads 1 to 2 cmlong
  • When acidity is 0.4 to 0.5 % and
  • When pH is 5.4 to 5.

Amount of salt added

  • This depends on the amount of curd in the vatand salt desired, and generally varies from 1 to 2 % (average 1.5 %).

Hooping

  • Thisrefers to the curd being placed in hoops or moulds in which the cheeses curd ispressed into its final shape. For hooping operation all the added salt shouldhave completely dissolved and the temperature at hooping should be 30-32º C.Hooping and pressing at too high a temperature causes an excessive loss of fat, decreased yield, development of abnormal flavours and exaggeration of bacterialdefects. On the other hand, hooping and pressing at a too a low temperatureresult in an open texture, imperfect rind formation and lack of whey drainage.

Dressing

  • Refers toarrangement of the cheesecloth before and after pressing.

Pressing

  • Thisrefers to the operation of forcing the particles of milled and salted curd inthe hoops into the smallest possible space to give cheese its final shapes.Cheese pressing is done with the help of presses which may be, Screw or Pneumatic or Hydraulic or spring types.

Drying

  • Thisis done for rind formation in cheese. It involves first taking the cheese outof the hoop and then stamping of date, batch, variety name etc., and keeping ina drying room at 12 to 16 º C for a few days. The cheese is turned at 24-hourintervals so that both ends and sides of the cheese can dry and form thedesired rind.

Paraffining

  • This refers to the operation of dipping the cheese for a few seconds in a bath ofmelted paraffin, whereby a thin coating of the paraffin is applied to thesurface of the cheese.

Objectives

  • To reduce the loss of moisture during curing
  • To prevent extensive mould growth
  • To protect it against insects

Curing

  • Thecuring/ripening/souring/maturing of cheese refers to the storage of cheese forat least 2 to 3 months at a given low temperature (0-16ºC) during which itsphysical, chemical and bacteriological properties are profoundly changed,resulting in the development of a characteristic flavour, body and texture.
  • Theterm ‘green cheese’ is usually applied to hard-pressed cheese in the earlystages of ripening before the characteristic flavour, body and texture ofripened cheese developed.
  • Theprocedure involves dipping of cheese blocks quickly and completely in themelted paraffin held at 104-121º C for about 5 seconds, allowed to drain for 10seconds.

Changes during curing

  • Flavour
    • From a mildly acid taste and aroma in greencheese to the development of characteristic flavour of ripened cheese which isa blend of several odours and tastes of diacetyl, traces of butyric and caproicacid, esters of alcohol, salts of propionic and acetic acids in well agedcheeses.
  • Body
    • Thecheese becomes slightly harder, due to loss of moisture. There is a gradualchange from the rubbery body in the green cheese to a mellow and waxy body in theripened cheese.
  • Texture
    • Curdcheese tends to acquire a fairly close to close texture.
  • Chemical changes
    • Thechief chemical changes which occur during the curing of cheddar cheese are:fermentation of lactose to lactic acid and small amounts of acetic acid,propionic acid and carbon dioxide; proteolysis; and a slight fat break down.The most obvious chemical changes are the breakdown of the proteins, the newlycreated solubility of about 25 % of total proteins in the cured cheddar cheese. In addition to fat breakdown, the ammoniaproduced by moulds and certain bacteria may have considerable effect on thebacteria and so assist in the growth of other types of bacteria.
    • An increase in acidity and decrease in pHtakes place for the first few days. ThepH is lowest in cheese on about the third or fourth day after pressing, and isnormally 5.10 to 5.05. It then decreasesslowly and steadily during the curing period.
  • Microbiological changes
    • Incheddar cheese type, which are low in moisture and close in texture sustain asteady changeover from Streptococci to Lactobacilli, some of which contributeto the flavour. Other types are of course present and the higher the proportionof miscellaneous types, the quicker is the curing and greater the possibility ofoff-flavours.

Shrinkage in Cheese

This refers to the loss in weight of cheese during curing/storage.Although a slight shrinkage is natural, excessive shrinkage should beprevented. Shrinkage is caused mainly by ‘loss of moisture’.

Factors causing Shrinkage in Cheese:

  • Temperature of curing: Higher the temperature,higher the shrinkage, and vive-versa
  • Relative humidity of curing: Higher the humiditylower the shrinkage.
  • Size (and shape) of cheese: Larger the size,lower the shrinkage and vice-versa
  • Moisture content of cheese: Higher the moisturecontent, higher the shrinkage
  • Paraffining of cheese: Paraffined cheeseundergoes less shrinkage, than non-paraffined cheese.

Ripening index

  • Proteindegradation measurements have been used systematically in studying the ripeningof cheese. The rate of ripening is measured by determination of the ‘ripening index’

Index= % soluble nitrogen  / %total nitrogen X 100

 Yield

  • This is affected by the quality of milk, nature of manufacturingoperations, the skill of the manufacturer, and curing procedures.
Last modified: Monday, 16 April 2012, 12:04 PM