Module 13. Defects in cheese

Lesson 28


28.1 Defects in Cheddar 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.

Table 28.1 Defects in cheese can be related to the following aspects

28.2 Defects Related to Moisture Content

The presence of either too little or too much moisture in cheese is associated with certain characteristics. The qualities of cheese affected are flavor, body or consistency, texture or openness and color. When the moisture is extremely high or low, the finish of the cheese is also affected.

Moisture has an influence on all of these characteristics because it is directly related to the composition and physical qualities of the cheese. Moisture is indirectly related to these characteristics because it carries lactose and some of the milk salts in solution. Microorganisms change lactose to acid, chiefly lactic. A certain amount of such lactic acid formation is necessary for proper cheese making and ripening; excessive amounts make the cheese taste sour while inadequate amounts may delay ripening or may actually encourage abnormal fermentations of undesirable type. The amount of moisture in cheese must be properly controlled.

28.2.1 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. Causes

One or more of the following may be responsible:

  • An unusually high fat content in milk fat delays firming.
  • Lack of acid development during making.
  • Insufficient heating or heating too rapidly.
  • Incomplete removal or elimination of whey. Prevention

It is usually not necessary to apply all the measures of control indicated. The results might produce cheese with too little moisture. The corrections may be selected by scrutinizing the manufacturing records.

28.2.2 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. Causes

May be due to one or more of the following:
  • Maximum acid development throughout making process.
  • The use of excessive amounts of rennet or CaCl2
  • Fine cutting or breaking of the curd.
  • Heating and holding temperature high.
  • Excessive stirring of the curd while the whey is being removed and immediately after dipping.
  • Lack of piling during cheddaring operation.
  • Addition of too much salt.
    • Holding the cheese in a warm drying room long before paraffining. Prevention

a) At salting

Steps may be taken to reduce the acid development, ripening period and amount of starter, besides adding the rennet sooner. The amount of rennet should be reduced, use of calcium chloride should be avoided, a firm cut should be developed at cutting and coarser knives may be used for cutting curd.

b) At heating

The temperature may be decreased. If the temperature used approximates 36°C, then acid development may be stimulated.

c) At dipping

Minimum amount or acid recommended for normal making operation should be developed. The curd should be settled 30 min before dipping and it should not be stirred at any time thereafter. As the curd settles under the whey, it should be pushed towards the side of the vat to form layers approximately 25 cm deep. The whey should be removed early and before the curd develops extreme firmness, this measure of control is most commonly used and is entirely adequate even when applied alone in ordinary making practice. The layers of curd should be cut into blocks 25 cm wide and piling should be sooner than usual. It should be piled 4 or 5 high before milling. Allow the curd to cool during cheddaring.

d) At Milling

Use the minimum acid development consistent with recommended making procedure. Cool the curd promptly after milling by stirring and rinsing highly with water at 15-21°C. Salt the curd promptly and use the minimum amount indicated for normal cheese. After pressing remove the cheese to a cool room and paraffin it as soon as the rind is properly dried.

28.3 Defects Related to Acid Content

The presence of too much or too little acidity in Cheddar cheese is associated with certain defects. Excessive acidity is found in cheese that contains more than normal amounts of moisture because such cheese contains more than normal amounts of lactose. Excessive acid development during the making process can also produce acid defects in the finished cheese even when the moisture content of the product is normal or perhaps less than normal.

28.3.1 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. Causes

• Too much moisture in cheese

• High acid initial milk

• Use of too much starter

• Prolonged ripening period

• Too much acid development before adding rennet

• Too much acid development at other steps

28.3.2 Effects of lack of acidity

The common characteristics:

a) Flavor - mild when fresh and fermented, fruity or lacking when aged. True cheese flavor develops slowly, if at all.

b) Body - corky, pasty, sticky or weak. The cheese remains curdy for long time in curing.

c) Texture - open, with large mechanical holes. The cheese with insufficient acidity may also show the effects of uncontrolled fermentations of gas producing yeasts or bacteria.

d) pH - usually more than 5.3 when the cheese is approximately 4 days old. Causes
  • Failure of starter - due to inactive starter, improper handling of starter, unfavorable conditions for starter activity, or bacteriophage.
  • Abnormal milk - unfavorable manufacturing methods, unnecessary amount of CaCl2.
  • At Milling - Delay milling until the whey draining from the curd shows at least 0.30% acid. The hot iron test should be nearly 3/8″ long and the pH of the curd should be not more than 5.6.
If the acidity of the whey after two hours of dipping does not exceed 0.25%, then it is highly probable that the starter is faulty or that it is contaminated with bacteriophage. If contaminated with phage, prolonging Cheddaring operations for 4-5 h do not help acid development. Holding the curd in pack for 12 h or longer sometimes permits acid development in curd affected with phage. The curd must be kept at 29°C during this period.

28.4 Defective flavors

28.4.1 Acid flavor

This results from the development of too much acid at any stage of cheesemaking or curing. 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.

28.4.2 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. Unclean conditions e.g. rust spots, open seams, milk stones in cans and utensils may cause this 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.

28.4.3 Fermented 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. They may appear in cheese soon after it is made, but they usually develop after the cheese is two weeks old. They are believed to be caused by yeasts or bacteria. These organisms may get into the milk on the farms by contact with unclean and non-sterile surfaces of utensils, milking machines, and milk cans. This can be prevented by:

(i) Utmost precaution in plant sanitation,

(ii) Clean and active starter and

(iii) Ripening at 7°C or below.

28.4.5 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. This flavor defect is closely related to the fermented flavor defect. Hence the origin, prevention and remedies are identical to that of fermented flavor defect.

28.4.6 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.

Mold grows slowly on cheese held at low temperature and under dry conditions; it grows rapidly at high temperature and high humidity. It grows most luxuriantly on non-paraffined cheese.

Prevention – Proper paraffining, close texture, sound rind, curing at 7°C and relative humidity below 75% minimize the defect.

28.4.7 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.

28.4.8 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.

28.5 Defects Related to Body

The term body is used by technologists in the cheese industry to designate the physical properties of consistency. These properties include firmness, cohesiveness, elasticity and plasticity. These physical characteristics of cheese are sometimes called rheological properties. Firmness is the property of the cheese which causes it to resist deformation or distortion under pressure. Cohesiveness is the characteristics of the cheese that causes it to stick together. Elasticity is the capability of the cheese to recover its size and shape after deformation. Plasticity is the quality of the cheese which enables it to be deformed under pressure without rupture.

The rheological properties of cheese are affected by methods of manufacture and composition of cheese.

Various terms are used to indicate firmness, elasticity, cohesiveness, and plasticity of curd and cheese. These terms describe the appearance and feelings of the cheese when a plug is removed from the cheese block. A normal plug of ripened Cheddar cheese shows a smooth, uniform surface. It feels solid and firm, it does not crumble, when cut or pressed. It bends before breaking and when rubbed between the thumb and fingers, it feels smooth and waxy like cold butter.
Some of the common defects are as follow:

28.5.1 Corky

Cheese with a firm, hard, tough and somewhat elastic consistency is called corky. Such cheese is difficult to crush with the fingers, but when enough pressure is applied it breaks apart in a woody manner.

Corky body may be apparent as very firm curd at the time of draining; the characteristics usually appear before salting. Corky characteristics may persist throughout the life of the cheese.

Causes – Low fat content, lack of acid development, over-heating during cooking, lack of moisture and excessive salt content.

28.5.2 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 lack of cohesion is apparent through the whole cheese and is not limited to the surfaces of the curd particles which make up the cheese. Crumbly cheese usually feels firm before breaking. It shatters with a snap, like breaking of chalk.

The defect rarely appears during the making operations, although the first stage of crumbly body may be evident when excessively acid curd fails to mat properly during cheddaring. The defect is usually apparent in fresh cheese within a week after making; it persists throughout the life of the cheese.

Crumbly body in cheese can be prevented by observing the preventions and remedies for excessive acidity.

Crumbly body gradually develops in aged cheese and is not regarded as a defect, if the cheese is sweet in flavor. 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.

28.5.3 Curdy

This characteristic is natural in fresh cheese and is rightly regarded as a defect only when it persists beyond about 30 days. Curdy cheese, when broken apart, reveals the size and shape of the original curd particles after salting.

When pressed between the fingers it feels elastic, firm and somewhat like the particles of curd at the time of salting. It cannot be worked together in the fingers after it has once been broken apart. 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.
28.5.4 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.

Mealy body can be most readily detected after the curdy characteristics of the cheese have fully disappeared; it is actually apparent during the first week of curing but is not so easily discovered. It persists throughout the life of cheese.

Cause - Excessive acidity, it may be regarded as a stage of disintegration of crumbly cheese.

Mealy body in cheese can be eliminated in future lots by observing the preventions and remedies for excessive acidity.

28.5.5 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.

28.6 Defects Related to Texture

Open texture is the most common defect in cheese. It may be due to the formation of gas or mechanical faults. The causes of this defect are as follows:

a) Contamination of cheese with gas producing bacteria and yeasts.

b) Lack of acidity

c) Moisture content

d) Free whey trapped in curd, and

e) Lack of sufficient pressure during pressing of cheese.

The defect can be controlled by eliminating source of contamination, using pure culture, and pasteurizing the milk efficiently. Acidity of 0.16% LA at draining, piling high, milling at acidity 0.60% LA, delayed salting; washing the curd with water at 30°C and curing below 10°C also help in controlling the defect.

Table 28.2 Color defects in cheese

Last modified: Wednesday, 3 October 2012, 10:30 AM