Cheese

History of Cheese Manufacturing

Cheese is one of the oldest foods of mankind. It is commonly believed that cheese evolved in the Fertile Crescent between the rivers Tigris and Euphrates in Iraq some 8000 years ago. The so-called Agricultural Revolution occurred here with the domestication of plants and animals. Cheese is a protein rich product but at the same time, it also contains a considerable amount of fat. So, the calorie conscious populace of the world reduced the consumption of cheese. Keeping this in mind, a variety of low fat cheeses have been developed throughout the world to increase its consumption and to make it healthier. Now-a-days, work is being carried out to produce low salt cheese as increased salt consumption is leading to increased heart diseases in many countries particularly United States.

Introduction

The word ‘cheese’ is derived from the Old English ‘cese’ which in turn was derived from the Latin ‘caseus’ which means correct or perfect thing. Cheese may be defined ‘as the curd of milk separated from the whey and pressed into a solid mass’. This definition of cheese is satisfactory but too limited and vague from a technical standpoint. Therefore, a relatively complete definition is as follows:

Cheese is the curd or substance formed by the coagulation of milk of certain mammals by rennet or similar enzymes in the presence of lactic acid produced by added or adventitious microorganisms, from which part of the moisture has been removed by cutting, warming and pressing, which has been shaped in mould and then ripened (also unripened) by holding for sometime at suitable temperatures and humidity.

Such a grouping, though informative, is imperfect and incomplete. These can also be classified on the basis of their rheology, and according to the manner of ripening as shown below:

1) Very hard (grating) - Moisture < 35% on matured cheese and ripened by bacteria, e.g. Parmesan, Romano.

2) Hard - Moisture < 40%

a) Ripened by bacteria, without eyes: Cheddar

b) Ripened by bacteria, with eyes: Swiss

3) Semi-hard - Moisture 40-47%

a) Ripened principally by bacteria: Brick

b) Ripened by bacteria and surface microorganisms: Limburger

c) Ripened principally by blue mold: Camembert, Gorgonzola, Blue, Roquefort

4) Soft - Moisture > 47%

a) Unripened – Cottage

b) Ripened – Neufchatel (as made in France)

Composition of cheese

 It comprises proteins and fat from milk, usually the milk of cows, buffalo, goats, or sheep.

• Protein - 27%

• Fats - 33%

• Minerals - 4%

• Moisture - 35%

• Salt - 1.5%

An excellent source for several fat soluble vitamins, such as A, D, E & K .

Ingredients

The main ingredient in cheese is milk. Cheese is made using cow, goat, sheep, water buffalo or a blend of these milk .

The type of coagulant used depends on the type of cheese desired. For acid cheeses, an acid source such as acetic acid (the acid in vinegar) or gluconodelta - lactone (a mild food acid) is used. For rennet cheeses, calf rennet or, more commonly, a rennet produced through microbial bioprocessing is used. Calcium chloride is sometimes added to the cheese to improve the coagulation properties of the milk . Flavorings may be added depending on the cheese. Some common ingredients include herbs, spices, hot and sweet peppers, horseradish, and port wine etc. 

Bacterial Cultures

Starter cultures are used early in the cheese making process to assist with coagulation by lowering the pH prior to rennet addition. The metabolism of the starter cultures contribute desirable flavor compounds, and help prevent the growth of spoilage organisms and pathogens. Typical starter bacteria include Lactococcus lactis subsp. lactis or cremoris, Streptococcus salivarius subsp. thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Lactobacillus helveticus .

Yeasts and molds are used in some cheeses to provide the characteristic colors and flavors of some cheese varieties. Torula yeast is used in the smear for the ripening of brick and limburger cheese. Examples of molds include Penicillium camemberti in camembert and brie, and Penicillium roqueforti in blue cheeses .

General Cheese Processing Steps

• Standardize Milk

• Pasteurize/Heat Treat Milk

• Cool Milk

• Inoculate with Starter & Non-Starter Bacteria and Ripen

• Add Rennet and Form Curd

• Cut Curd and Heat

• Drain Whey

• Texture Curd

• Dry Salt or Brine

• Form Cheese into Blocks

• Store and Age

• Package

The times, temperatures, and target pH values used for  cheese will depend on individual formulations and the intended end use of the cheese. These conditions can be adjusted to optimize the properties of  cheese for shredding, melting, or for cheese that is meant to be aged for several years.

1. Standardize Milk

Milk is often standardized before cheese making to optimize the protein to fat ratio to make a good quality cheese with a high yield .

2. Pasteurize/Heat Treat Milk

Depending on the desired cheese, the milk may be pasteurized or mildly heat-treated at 63°C for 30min. to reduce the number of spoilage organisms and improve the environment for the starter cultures to grow. Some varieties of milk are made from raw milk so they are not pasteurized or heat-treated.

3. Cool Milk

Milk is cooled after pasteurization or heat treatment to 90°F (32°C) to bring it to the temperature needed for the starter bacteria to grow. If raw milk is used the milk must be heated to 90°F (32°C).

4. Inoculate with Starter & Non-Starter Bacteria and Ripen

The starter cultures and any non-starter adjunct bacteria are added to the milk and held at 90°F (32°C) for 30 minutes to ripen. The ripening step allows the bacteria to grow and begin fermentation, which lowers the pH and develops the flavor of the cheese.

5. Add Rennet and Form Curd

The rennet is the enzyme that acts on the milk proteins to form the curd. After the rennet is added, the curd is not disturbed for approximately 30 minutes so a firm coagulum forms.

6. Cut Curd and Heat

The curd is allowed to ferment until it reaches pH 6.4. The curd is then cut with cheese knives into small pieces and heated to 100°F (38°C). The heating step helps to separate the whey from the curd.

7. Drain whey

The whey is drained from the vat and the curd forms a mat.

8. Texture curd ( cheddaring )

The curd mats are cut into sections and piled on top of each other and flipped periodically. This step is called cheddaring. Cheddaring helps to expel more whey, allows the fermentation to continue until a pH of 5.1 to 5.5 is reached, and allows the mats to "knit" together and form a tighter matted structure. The curd mats are then milled (cut) into smaller pieces.

9. Dry Salt or Brine

For cheddar cheese, the smaller, milled curd pieces are put back in the vat and salted by sprinkling dry salt on the curd and mixing in the salt. In some cheese varieties, such as mozzarella, the curd is formed into loaves and then the loaves are placed in a brine (salt water solution).

10. Form Cheese into Blocks

The salted curd pieces are placed in cheese hoops and pressed into blocks to form the cheese.

11. Store and Age

The cheese is stored in coolers until the desired age is reached. Depending on the variety, cheese can be aged from several months to several years.

12. Package

Cheese may be cut and packaged into blocks or it may be waxed.   

Nutritional value and therapeutic value

Cheese is a fermented dairy product. Fermentation has occupied a place of pride in food preservation practice from time immemorial. It improves and enhances the nutritional value and enriches flavor, texture and rheology of the product. Fermented milk products have been reported to have therapeutic, anticholesterolemic, anticarcinogenic antihypertensive and anticariogenic properties. Cheese, as a delightful fermented food contributing to a variety in our diets, has been recognized to provide important nutrients and considered superior to non-fermented dairy products in terms of nutritional attributes as the microflora present produce simple compounds like lactic acid, amino acids and free fatty acids that are easily assimilable .

Defects in cheese 

Cheese is a product of fermentation and consequently undergoes constant changes. Its characteristics of flavor, body and texture, color and curing qualities are influenced by the quality of milk, techniques of manufacture, temperature of curing and length of curing time. Cheese develops defects when there is deviation in the selection of appropriate quality of milk, method of manufacture and curing. 

1.Defects Related to Moisture Content

The presence of either too little or too much moisture in cheese is associated with certain characteristics .

Effects of excessive moisture 

The characteristics of cheese with excessive moisture are as follow:

a) Flavor may be sour or acid or merely slightly acid when fresh, and lacking in cheese flavor and sour when aged.

b) Body may be weak or soft when fresh, and sticky and pasty when aged.

c) Texture may be open if the acid development during the making operation is inadequate.

d) Color may be higher

Effects of insufficient moisture 

a) Flavor - mild or lacking. It may be slightly acid if lack of moisture was caused by excessive acid during making. Cheese flavor develops slowly.

b) Body - firm, hard or corky, and sometimes crumbly and mealy. Loss of curdy characteristics during ripening is extremely slow.

c) Texture - usually close and solid but may show mechanical openness where curd particles failed to knit together properly during pressing.

d) Color - sometimes deeper in shade and rind formation is frequently darker in color than the rest of the cheese.

e) Finish - may show defective knitting together of curd particles.

2. Defects Related to Acid Content

The presence of too much or too little acidity in  cheese is associated with certain defects.

Effects of excessive acidity

All the physical characteristics of Cheddar cheese may be affected by excessive acidity.

a) Flavor – acid or sour. Bitterness is sometimes associated with too much acid development during making. True cheese flavor is lacking or slows in development.

b) Body – firm, dry, crumbly, short and mealy when the moisture content is low, it may be soft, pasty, sticky, and short when the moisture content is high.

c) Texture – usually close although in extreme instances the curd particles may be so poorly knitted together that numerous mechanical openings will be formed.

d) Color – bleached or acid cut and sometimes mottled.

e) pH – usually less than 5.05 when the cheese is 3 to 4 days old.

3. Defective flavors

a) Acid flavor 

It may occur from high acid milk as received, ripening too long before setting, too much starter, improper cutting, cooking too fast or other factors which may interfere with proper expulsion of whey from the curd, or otherwise developing acid faster and higher than normal. Low salt content of cheese may also be a contributing factor.

b) Bitter flavor

This is a common defect. It is associated with inferior milk and poor starter, with excessive moisture and high acidity in cheese and using too much rennet and unclean utensils. Relatively higher temperature and use of Leuconostoc sp. as starter has been noted to cause the defect. Conditions associated directly with the manufacturing operations may also be responsible e.g. excess acid, excess moisture, lack of salt, and high curing temperature.

c) flavor

These flavors are characteristics of the odor of fermented whey and possess some of the qualities of the combined odors of alcohol, acetic acid and propionic acid. It is caused by yeast and bacteria.

d) Fruity flavor

The fruity flavor defect has been described as pineapple, raspberry or pear-like flavor in cheese. The compounds responsible for the defect are esters, certain acetaldehydes and ketones and some alcohols.

e) Moldy flavor

It is associated with curing conditions. It is caused by the growth of mold in or on the cheese. Mold will grow in Cheddar cheese only when O2 gains entry through openings in the rind or through openings or cracks inside the cheese which connect with trier holes or other defects in the rind.

f) Rancid flavor 

Rancidity is the flavor characteristic of the odor of butyric acid. It is believed to be present in all normal Cheddar. This flavor may come from the milk itself.

g) Unclean flavor

Flavors that are foreign to milk and cheese but which can not be identified or otherwise described are usually called unclean. Unclean flavors are often attributed to the development of undesirable microorganisms in the milk, curd or cheese.

4. Defects Related to Body

The term body is used by technologists in the cheese industry to designate the physical properties of consistency .

a) Corky

Cheese with a firm, hard, tough and somewhat elastic consistency is called corky . It is caused by low fat content, lack of acid development, over-heating during cooking, lack of moisture and excessive salt content.

b) Crumbly

This defect is characterized by the falling apart of cheese when sliced, by difficulty in removing a full plug and by the breaking of the cheese into pieces that crumble when crushed between the thumb and fingers .This crumbly body is caused by ripening changes in the foods and by loss of moisture. This condition is associated only with a fully matured flavor in the cheese.

c) Curdy

This characteristic is natural in fresh cheese and is rightly regarded as a defect only when it persists beyond about 30 days.

Causes

• Low moisture content which delays curing

• Lack of proper acid development

• Lack of proper cheddaring in the vat before milling

• Addition of excessive amounts of salt, or

• Low temperature storage.

d) Mealy

This characteristic appears when cheese is crushed and rubbed between the thumb and fingers, the structure of the curd looks and feels rough, the characteristic is the opposite of the waxy, smoothness desired in normal cheese. It is caused by excessive acidity, it may be regarded as a stage of disintegration of crumbly cheese.

e) Pasty

Cheese with this defect is soft in consistency, when pressed and rubbed between the fingers, it quickly becomes sticky and clings to the fingers . Pasty body in cheese becomes apparent as soon as the curdy characteristics disappear. The defect is caused by excessive moisture.

Reference :-

• http://ecoursesonline.iasri.res.in/mod/page/view.php?id=5382

• http://milkfacts.info/Milk%20Processing/Cheese%20Production.htm   

Name : Akanksha Gupta https://sites.google.com

M.Sc. 2nd sem.

Roll No : 11