Cream and Butter

CREAM

Cream

  • According to the PFA rules (1976), cream, excluding sterilized cream, is the product of cow or buffalo milk or a combination thereof, which contains not less than 25 per cent milk fat. Cream is rich in energy giving fat and fat-soluble vitamins A, D, E, and K, the contents of which depends on the fat level in cream.

Classification

Cream may be broadly classified into Market cream, which is used for direct consumption,and Manufacturing cream, which is used for the manufacture of dairyproducts.The three different types of cream are

  • Table cream/Lightcream contains 20-25% milkfat.
  • Coffee cream/ Whipping cream Contains 30-40 % milk fat,and
  • Heavy cream/Plastic cream contains 65-85 % milk fat.

Composition of cream

The average chemical composition of cream is as follows:

  • Water 45.45-68.2%
  • Fat 25-60 %
  • Protein 1.69-2.54 %
  • Lactose 2.47-3.71. %
  • Ash 0.37-0.56 %
  • Total solids 31.8-54.55 %
  • Solids not fat 4.55-6.80 %.

T he solids not fat (SNF) content of cream can be determined by

% SNF in cream = (100 - % fat in cream / 100 - % fatin milk)  X % SNF in milk

Cream can be separated from milk by either ‘gravity’ or‘centrifugal separation’ methods. The basic principle of cream separation is based on the fact that milk fat is lighter than the skim milk portion (difference in densities). The average density of milk fat is 0.93 and skim milk is 1.036. Hence when milk is subjected to centrifugal force, the two components, viz., cream and skim milk,gets separated.

Method of cream production

I. Gravity method

When the milk is allowed to stand undisturbed for some time,there is a tendency for the fat to rise is given by he following equation,which is known as Stokes Law:

V = 2G (ds - df) r 2 / ù

where,

V = velocity or rate at which a single fat globule rises

G = acceleration due to gravity.

ds = density of skim milk

df = density of fat.

r = radius of fat globules.

ù = viscosity of skim milk.

Applying the stokes law it can be observed that theoretically,velocity is increased byIncrease in radius of fat globules:Increase indifference in densities of skim milk and fat, Decrease in viscosity of skim milk.

The rate of rise of fat globules in gravity methods is affected by

  • Size of fat globules: as the size of fat globules increases, the rate at which cream rises also increases.
  • Temperature: As temperature increase, viscosity decreases and hence the velocity increases.
  • A clump or cluster acts like a single globule in so far as movement through skim milk is concerned.
  • Gravity methods being very slow, are no, longer used commercially for cream separation.

II. Centrifugal method

Centrifugal cream separators are similar to clarifiers in that they consists of a stack of conical discs housed in a separator bowl and rotated at high speed by an electric motor.

The Separator

  • The separator is a unit, which removes most of the milk fat from milk by centrifugal force. Its principal components are power source, a separator bowl, a set of gears and shafts, a product inlet and a product outlet for cream and skim milk.
  • The separator bowl consists of an outer shell within which are a large number of cone shaped discs constructed so that between each pair is a very small space of not more than 0.5mm. As the milk enters the bowl,it is distributed into these spaces between the discs; it is immediately subjected to a tremendous force. While both the fat and skim milk subjected to the centrifugal force, the difference in density affects the heavier portion (skim milk) more intensely than the lighter portion(i.e. Cream) thereby the skim milk is forced to the periphery while the fat portion moves towards the centre. The skim milk and cream both form vertical walls within the bowl and are separated by being led trough separate outlets.
  • Any insoluble particles in the milk, such as bits of curd or dirt etc., collects as ‘separator slime’ and is thrown outward as the bowl operates. These pass along with the skim milk into the space between the outer edge of the discs and the inner face of the bowl shell. Such material is deposited on this face of the bowl shell, which is removed latter. Separator bowl operate at speeds as great as 20,000 rpm. The separator is a precision instrument andhence has to be in good condition and operated properly to get maximum skimming efficiency.

Centrifugal force (F) = K .W. R . N2

Where

W= mass of the revolving body,

R= radius of the circle in which body revolves.,

N= R.P.M of the revolving body.

K= constant.

Stokes’s law applied to centrifugal separation is as follows

((ds-df) / n ) X  V = r2 N2.R.K.

Where

V = velocity

n = viscosity of skim milk

r = radius of fat globule,

ds = density of skim milk

df density of fat,

N= speed of the bowl

R= distance of fat globule from the axis of rotation.

K = constant

Factors influencing the fat percentage of cream

The important factors that influence the fat percentage of cream by centrifugal cream separation methods are

  • Position of the cream screw
    • The cream screw /outlet consists of a small threaded, hollow screw pierced by a circular orifice thorough which the cream emerges. This screw can be driven IN and OUT thus bringing it nearer to and away from, the center of rotation. Similarly the skim milk screw /outlet for the removal of skim milk, once the cream screw or skim milk screw has been adjusted, the cream separator delivers, under normal conditions, a definite ratio of skim milk and cream, which is usually90:10 (or 85:15) by volume. By altering the position of the cream screw or skim milk screw the ratio of skim milk to cream changes. Thus when the cream screw is IN towards the axis of rotation, a higher fat percentage in cream is obtained and vice versa. This is because the force tending to discharge cream through the orifice is decreased while that tending to discharge skimmilk remains unaltered. Smaller proportions o cream is therefore discharged, which, containing the same quantity of fat, shows a higher fat percentage. Screwing OUT the cream screw produces thinner cream. Similarly the skim milk screw OUT results in richer cream and vice versa.
  • Fat percentage in milk
    • The higher the fat percentage in milk, the higher the percent fat in cream. And vice versa. Since practically all the fat in milk is contained in the cream.
  • Speed of bowls
    • Higher the speed of the bowl, the higher the fat percentage on cream, and vice versa.
  • Rate of milk in-flow
    • The higher the rate of milk inflow, lower the fat percentage in cream and vice versa.
  • Temperature of milk
    • The lower the temperature of milk during separation, the higher the fat percentage of the cream and vice versa.
  • Amount of water or skim milk added to flush the bowl.
    • The greater the quantity of water added to flush the bowl, the lower the fat percentage in cream, and vice versa.

Factors affecting fat loss in skim milk during separation

The ‘skimming efficiency (SE) of a cream separator refers to the ‘percentage total fat from milk recovered in the cream. The higher the fat percentage in milk and/or the greater the fat loss in skim milk, the lower the skimming efficiency and vice versa.

The factors affecting the fat loss in skim milk are

  • Temperature of milk
    • The lower the temperature, higher the fat loss in skim milk and vice versa. For the efficient separation the temperature of milk should be above the melting point of fat, so that the milk fat in the fat globules is uniformly in liquid form. A satisfactory temperature for separation isaround 40 ° C. The milk is heated before separation to 35-40 ° C in plate or tubular heaters for efficient separation. This is known as ‘ preheating /fore warming’of milk.
  • Speed of the bowl
    • The lower the speed, the higher the fat loss in skim milk and vice versa. At below –rated speed,there will be more fat loss in skim milk because insufficient centrifugal force is generated for efficient cream separation. With above rated speeds, the skimming efficiency will not increase greatly.
  • Rate of milk inflow
    • The higherthe rate of inflow, the higher the fat loss in skim milk and vice versa.
  • Position of cream screw
    • Upto 50% of fat in cream, there is little effect on the fat loss in skim milk, but when the cream fat test is greater than 50-60% there is greater fat loss in skim milk; if above 60% of cream is obtained still higher fat loss in skim milk results.
  • Mechanical condition of the machine
    • Unsatisfactory mechanical condition of the cream separator causes greater fat loss in skim milk that include, vibration of the separator, conditions of discs, amount of separator slime in the bowl.
  • Size of the fat globule
    • The greater the number of fat globules of less than 2 microns size, the higher the fat loss in skim milk and vice versa, as they escape the centrifugal force and to be recovered in cream.
  • Degree and temperature at which milk is agitated before separation
    • The higher the degree and temperature of agitation the greater the loss in skim milk and vice versa.
  • Presence of air in milk
    • The greater the amount of air, the higher the fat loss in skim milk.
  • Acidity of acidity
    • The higher the acidity, the lower the efficiency of separation. The higher acidity, the lower the stability of casein particles, which in turn get precipitated and clog the bowl, there by lowering the efficiency of separation.

Quality of cream

Cream is no better than the milk from which it is made. It is not possible to obtain good bacteriological quality cream from low grade milk. In order to produce high quality cream, the following steps are needed,

  • Clean milk production
  • Cooling of milk soon after production
  • Separating milk under hygienic conditions
  • Prompt cooling of cream and its storage at a low temperature \ transport of cream to the dairy under low temperature.

Standardization of cream

  • This refers to the adjustment of the fat level in cream to the desired percentage conforming to standard requirements. The fat percentage in cream is usually adjusted to the prescribed level by the addition of calculated amount of skimmilk by Pearson’s square method.

Pasteurization of cream

  • Pasteurization of cream refers to the process of heating every particle of cream to not less than 71°C and holding it at such a temperature for at least 20 minutes, or to any suitable temperature – time combination using approved and properly operated equipment.

Objectives of pasteurization

  • To destroy the pathogenic microorganism in cream so as to make it, and also resultant butter, safe for human consumption.
  • To destroy undesirable micro organisms and inactivate the enzymes present , so as to prolong the keeping quality of the cream and butter,
  • To complete the neutralization process.
  • To eliminate some of the gaseous tainting substances.
  • To make possible the removal of some volatile off-flavours

Methods

  • Holding pasteurization
    • The cream is heated to 71 ° C for 20minutes and then promptly cooled.
  • HTST pasteurization
    • The Plate Pasteurizer is better suited to freshly separated sweet cream than neutralized cream, as the latter more easily forms burnt-on films on the plates. The maximum heating temperature may be 95-100 ° C for 5-16seconds.
  • Vacuum pasteurization
    • This is a continuous process and removes the off-flavours effectively. This process dilutes the cream and it will lower the fat percentage of cream up to 6 - 8 %.

Manufacture of different types of cream

  • Sterilized or canned cream
    • Sweet cream is standardized to 20% fat, pre-heated to 80 ° C without holding and then double homogenized immediately, cooled to 16 ° C filled in to tin cans and immediately sealed. It is then sterilized at 118 ° C for 12-15minutes.
  • Plastic cream
  • Frozen cream
    • Objectives: To improve the keeping quality of cream during transportation over long distance, to store surplus cream for use during shortage mainly used by ice cream manufacturers who add sucrose to cream before freezing to prevent oiling off after thawing. First the cream is standardized to 40-50% fat, pasteurized at 77 ° CC for 15minutes cooled to below 4 ° C and filled into paper /plastic container or tin can and sealed well and then frozen at –12 ° C or below.
  • Clotted cream
    • This is prepared by heating cream to 77-88 ° C in shallow pan and then allowing it to cool slowly. The surface layer consists of clotted cream, which is skimmed off and strained.
  • Sour cream
    • This is a heavy bodied ripened cream of high acidity (0.6%) clean flavor and smooth textures made by inoculating sweet, pasteurized and homogenized cream with a culture of lactic acid and allowing fermentation to proceed until thesequalities are obtained.
  • Synthetic cream
    • This is mixture of flour, egg-yolk, sugar, water, and vegetable fat usually groundnut oil.

Packaging and storage of table cream

  • Packaging: Table cream is packaged for retail sale in units similar to those for milk such as glass bottle, paper cartons LDPE sachets, plastic bottles etc.
  • Storage and distribution: cream is stored preferably at 5-10 ° C and distributed as early as possible, but preferably within three hours of removing from, cold storage.

Defects in cream, their causes and prevention

Name of the defect

Causes

Prevention

Table cream

Flavour

Cooked flavour

Excessive heating of cream during preparation.

Proper heating of cream during pasteurization.

Feed and weed flavour

Feeding of milk-tainting feeds and weeds within 3 hours before milking

I) Feeding of milk-tainting feeds and weeds soon after milking

ii)eradication of milk tainting weeds

iii)vacuum pasteurization of cream

Highly acid/sour cream

Use of sour milk for separation.

Acid development in cream.

Using fresh, sweet milk for perpetration.

Neutralization

Oxidized /oily/metallic /tallow.

Fat oxidation due to direct contact of milk with copper or iron, exposure of milk or cream to sunlight etc.

Proper tinning of milk or cream or cream holding vessels or using aluminum alloy or stainless steel as contact surface.

Vacuum pasteurization of cream.

Rancid

Fat hydrolysis due to lipase action in milk or cream.

Inactivating lipase by proper pasteurization of milk and cream.

Miscellaneous

Feathering on hot coffee

excessive homogenization pressure

Using sour cream

Addition of salts.

.proper homogenization pressure

using sweet cream

Avoiding addition salts.

Manufacturing cream

a) Flavor.

Barney

Poor ventilation of milking byre/barn

Not keeping milk properly covered during production.

Proper ventilation of milking byre/barn

Keeping milk properly covered during production.

Bitter

Intake of bitter weeds by milch animals

Lipase activity during cream separation.

Growth of proteolytic bacteria in cream.

Eradication of offending weeds.

Checking lipase activity by avoiding the danger zone during 39-49 ° C during raw cream separation.

Storage of cream at 5 ° C or below to check bacterial growth.

Cheesy

Growth of proteolytic bacteria leading to casein breakdown.

Storage of cream at 5 ° C or below to check the bacterial growth.

Coarse acid-/sour.

Uncontrolled acid development in cream.

Storage of cream at 5 ° C or below to check the acid development.

Cooked, feed and weed , rancid, oxidized etc.,

Same as table cream

Same as table cream.

Fruity

development of by-products of growth of certain undesirable microorganisms

Storage of cream at 5 ° C or below to check microbial growth.

Utensil

Using dirty utensils

Using well – cleaned utensils

Yeasty

Growth of lactose fermenting yeasts.

Storage of cream at 5 ° C or below to check the yeast growth.

BUTTER

  • Butter may be defined as a fat concentrate, obtained by churning cream, gathering the fat into compact mass and then working it.
  • According to the PFA rules (1976), table creamery butter is the product obtained from cow or buffalo milk or a combination there of, or from cream or curd from cow or buffalo milk or a combination thereof with or without the addition of common salt and annatto or carotene as colouring matter. It should be free from other animal fats, wax, and mineral oils,vegetable oils and fats. No preservatives except common salt and no colouring matter except annatto and carotene may be added. It must contain not less than 80% by weight of milk fat, not more than 1.5 % by weight of curd, and, not more than 3% by weight of common salt. Diacetyl may be added as a flavoring agent but, if so used the total diacetyl content must not exceed 4 ppm. calcium hydroxide , sodium carbonate,sodium polyphosphate may be added, but must not exceed the weight of butter as whole by more than 0.2 %.

Classification

Many kinds of butter are found in the market. This differs with the type of cream from,which they are made, and with variations in the manufacturing process. The types of butter are

  • Pasteurized cream butter
    • Made usually from pasteurized sweet cream. Such butter usually has a milder flavour than that made from similar cream not pasteurized.
  • Ripened cream butter
    • Butter made from the cream in which butter culture is added and incubated till the desired acidity and flavour are produced. Properly made ripened cream butter has a delicate flavour which is referred to as ‘ real butter flavour’
  • Unripened cream butter
    • Made from unripened cream.
  • Salted butter
    • Butter towhich salt has been added
  • Unsalted butter
    • Contains no added salt.
  • Sweet cream butter
    • Butter produced from cream in which the acidity does not exceed 0.2% in the churned cream.
  • Sour cream
    • Made from cream in which the acidity exceeds 0.2%.
  • Fresh butter
    • Butter that does not undergo cold storage.
  • Cold storage butter
    • Butter stored at a temperature of about -18 ° C for some time.
  • Dairy butter (USA)
    • Made on farm. It is usually made from unpasteurised sour cream, which has not been standardized for acidity. This butter generally has a sour flavour due to the high acid content of cream.
  • Creamery butter
    • Made in a creamery or dairy factory. It is more uniform in quality than dairy butter.

Composition

According to PFA Rules (1976) Table/Creamery Butter should contain not less than 80% fat, not more than 1.5 % curd and not more than 3%common salt. The typical composition of Indian butter has been given below.

Constituent

Percentage

Butterfat

80.2

Moisture

16.3

Salt

2.5

Curd

1.0

Butter is very rich in fat and fat-soluble vitamins.

Method of manufacture, packaging and storage

  • Receiving milk
  • Preheating (35-400C)
  • Separation
  • Cream Neutralisation Receiving cream
  • Standardisation for Fat (cow milk – 40%) (buffalo milk – 35%) (around 40% Fat)
  • Pasteurisation 82 – 88oC with out holding / 65oC for 30 mts / 74oC for15 sec.
  • Cooling (room Temp.)
  • Butter culture (0.5 to 2.0%)
  • Ripening (210C/15-16 hrs.)
  • Ageing (5-100C) (at least 2 to 4 hours) (preferably 15 to 16 hours)
  • Churning and Washing (9-110C)
  • Addition of butter colour*
  • (3%) Salting and Working of Butter
  • Packaging and storage (-23 to -29 ° C)

Overrun is caused by the presence (in addition to that of fat) of moisture, curd, salt, etc. in butter. It is a source of profit to the butter-maker (economical aspect); and also helps to check the efficiency of factory operations (technical aspect).

Average Overrun in Butter – 25% (due to moisture, curd, salt)

Details of manufacture

  • Receiving milk / cream
  • Grading
    • Purpose of grading is to pay for the product on the basis of its quality. Cream is graded on the basis of smell, taste,appearance, touch, acidity and sediment. The technique of grading cream consists in removing the lid of each can,inverting it and smelling it. Next the cream is examined for appearance and the presence of any extraneous matter. Cream for butter making isgraded in accordance with the grades of butter that can be made from it. The cream grades are:
      • First grade cream - sweet or slightly sour
      • Second gradecream - sour, coagulated
      • Reject grade cream - markedly sour, fermented.
  • Sampling
    • Beforesampling, the cream in the cans is thoroughly mixed by a combined rotary andvertical movements of the plunger/stirrer. If required the lidded cans of cream may be sprayed with hot water to reducecream viscosity, and facilitate mixing. Then a representative sample may be drawn for testing purposes.
  • Weighing
    • The cans of cream, which have been accepted, are thenweighed and the weight recorded for accounting and other purposes. First grade creams are tipped directly into the main neutralization vats. The cream adhering to the inner walls of the cansis recovered by inverting the cans over steaming jet for short periods.
  • Testing
    • The cream samples drawn are tested for fat, solids –not fat,acidity, etc., by standard methods.
  • Neutralizationof cream
    • Neutralization of sour cream for butter making refers to apartial reduction in its acidity.

Objectives

  • To avoid excessive fat loss in buttermilk that results from churning highly acid pasteurized cream. When pasteurizingsour cream, the casein curdles; thereby entrapping fat globules as the bulk ofcurd goes to butter milk this cause high fat loss.
  • To guard against the production of an undesirable off-flavour in cream.
  • To improve the keeping quality of butter made from high acid cream. Salted – acid-butter develops a fishy flavour during commercial storage at –23 to –29ºC. Correct neutralization is done by
  • Adoption of a definite standard of churning acidity. Butter for longstorage, the cream acidity should be reduced to 0.06-0.08% before churning.Butter for early consumption the cream acidity should be reduced to 0.25-30 %before churning.
  • Testing correctly for acidity take a sample of cream after through mixing,
  • First partially neutralize acid cream with a known quantity of standardalkali, and then treat as above.
  • Determine the lactic acidity of cream by titration of a fixed weight with a standard alkali using phenolphthalein as an indicator.
  • Correct amount of neutralizers to be added

The considerations are

  • The quantity of neutralizers to be added to a vat of cream varies withthe acidity of cream, the final acidity desired in pasteurized cream and withthe neutralizer compound used.
  • It is necessary; first, to calculate the quantity of lactic acid to beneutralized per 100 kg cream. Then the amount of neutralizer required must be calculated.
  • There are two groups of neutralizers available for use viz., lime(calcium hydroxide , and magnesium hydroxide) and soda (caustic soda, sodiumcarbonate, sodium bicarbonate and sodium sesquicarbonate)

The requirement of two selected neutralizers are given in table.

Types of neutralizers

Theoretical (kg)

Practical

Sodium bicarbonate

0.93

0.83 Up to 0.30 per cent cream acidity.

0.91. Beyond 0.30 per cent cream acidity

0.49

Calcium hydroxide

0.41

Correct procedure for adding neutralizer

  • The neutralizer should never be dry when added, but dissolved in clean, potable water and properly diluted, mixed with 10-15 timesof its weight in water. The temperature of cream when adding the neutralizer should be preferably is 29- 32º C. The cream acidity should be determined tocheck to whether it has been correctly neutralized.
  • Pasteurization/ vacreation of cream.

Ripening of cream

  • This refers to fermentation of cream with the help of desirable starter cultures.
  • Objectives: 1. To produce butter with a pleasing pronounced characteristic flavour,aroma,uniformly from day to day.
  • 2.To obtainan exhaustive churning, i.e., a low fat loss in buttermilk.
  • The butter starter culture containing lactic acid producers such as Lactococcus lactis subsp.lactis and Lactococcus lactis subsp. cremoris together with aroma (diacetyl)producers such as Lacotcoccus lactis subsp. lactis biovar diacetylactis,Leuconostoc mesenteroides subsp. dextranicum or L. citrovorum, in correctproportions, is added to the standardized, pasteurized and cooled (20-22 ° C) cream at0.5-2.0 per cent. After being thoroughly mixed, the cream is incubated at 21 ° for 15-16hours. The typical flavour of butter from ripened cream is mainly the effect ofdiacetyl, and to a smaller extent, of acetic acid and propionic acids. There is no diacetyl in sweet cream. The normal diacetyl content of ripened cream butter is on average 2.5 ppm and very rarely over 4 ppm.

Churning

Churning of cream consists of agitation at suitable temperatures until the fat globules adhere, forming larger and larger masses and until a relatively complete separation of fat and serum occurs. The object of churning is to produce butter from cream. The fat exists in the formof emulsion i.e. a continuous phase. This emulsion is fairly stable. As long as itremains intact, there is no formation of butter. The factors contributing towards the stability of this fat in skim milk emulsion are:

  • Force of surface tension: this causes the fat globules in milk/ cream to retain their individuality and prevent butter formation.
  • Phenomenon of adsorption: the surface layer of the fat globules contains an adsorbed,phospholipid protein complex, which resists deemulsion.
  • Electriccharge: the fat globules have negative charge and repel each other. The charge decreases as the cream acidity increases.
  • Viscosity:increased viscosity retards churning.
  • A greater concentration of fat globules in cream promotes amore profuse and rapid coalescence and aggregation than milk.
  • Preparationof churn: a new churn requires careful pre-treatment before use. An old churn requires proper sanitation and cooling, to render it clean.
  • Filling the cream into the churn: the amount of cream filled should be slightly below the rated capacity.
  • Addition ofbutter colour: this is done to maintain the uniformity of yellow colour in butter throughout the year for consumer satisfaction. The amount of standard color added varies from 0 to 250 ml ormore per 100 kg of butterfat. The butter colour should preferably be added to the cream in the churn.
  • Butter colourshould have the following properties: it should be harmless, free from offflavours, concentrated, permanent, and oil soluble. Butter colours are of following types:
    • Vegetableorigin: annatto and carotene. Annatto isobtained from the seeds of the annato plant (Bixa orellana) carotene isextracted from carrots and other carotene rich vegetable matter. Its use growing for it increases vitamin A potency.
    • Mineralorigin: harmless oil soluble coal tar dyes. Examples: yellow AB ( benzene Azo b - naphthyl-amine),Yellow OB( ortho toluene Azo- b -naphthylamine).

Churning of cream

  • Good churnability refers to clear breaking stage churninguntil the grains of butter are of the correct size. Exhaustiveness of churning - refers to fatlosses in buttermilk, satisfactory washing and optimum churning period.

Factors influencing churnability of cream and body of fat

  • Chemical composition of fat: an increase in the proportion of soft fat shortens the churning period, diminishes the firmness of butter and increases the fat lossesin butter milk and vice versa. Fresh green succulent feeds increase the proportion of soft fat and dry hard feeds increase the proportion of hard fat.
  • Size of the fat globes; the higher the proportion of the small –sized fat globules, the longer the churning time and the greater the fat loss in buttermilk and viceversa.
  • Viscosity ofcream: the greater the viscosity of cream, the greater the churning period andvice versa.
  • Temperatureof cream at churning: Under Indian conditions the optimum churning temperature ranges from 9-11 ° C. A higher churning temperature causes a shorter churning time, higher fat loss and a weak body in butter, which is difficult to wash and from which it is difficult toremove curd particles properly. A lower churning temperature prolongs the churning period.
  • Fatpercentage of cream. The higher thepercentage of cream, the lower the churning period. The fat percentage under Indian conditionswill be 40 for cow milk and 35 for buffalo milk.
  • Acidity ofcream: according to Hunziker, acid cream churns more rapidly and exhaustivelythan sweet cream. However Mc Dowel believes that the reverse is the case.
  • Load offchurn: the butter churn should be filled with one-half to one –third of its total capacity with cream. Overloading prolongs churning time, while under loading reduces total capacity of thechurn.
  • Nature ofagitation: this is influenced by he size, type, and RPM of the churn, and affects the churning period.
  • Pre-churning ageing period. Refers to cooling and ageing of cream.

Operating the churn

  • Afterinitially rotating the churn for 5 –10 min., the liberated gas is removed once or twice by opening the churn vent. Thenthe cream sample is drawn for the fat test. During the churning process there is invariably a rise in temperaturefrom 1-3 ° C. Churning is accompanied by foaming. Then comesthe “breaking stage”. When the creambreaks away from the spyglass, which becomes clear. At this stage the fat in the skim milk emulsion breaks and very small butter granules of the size of pin heads maketheir appearance, it is sometimes necessary especially in the tropics, to add break water at this stage to reduce the temperature of churn contents, and there by control the body of the butter. The amount and temperature ofbreakwater depends on the temperate reduction required. After the breaking the churning is continued until the butter grains are of the desired size (viz., ‘ pea size’ in largechurns). In the tropics, addition ofbreakwater can be avoided by providing an air-conditioned butter making room and /or chill water spray over the butter churn.

Factors affecting fat loss in buttermilk

  • Fatpercentage of cream: Lower the fat percentage of cream, the lower the fat percentage in butter milk,but the greater is the percent total fat loss in buttermilk, vice versa
  • Size of fatglobules. the greater the proportion ofsmall sized fat globules, the greater the fat loss ,and vice versa
  • Acidity ofcream at churning. According toHunziker, sour cream causes a lower fat loss than sweet cream; but according toMc Dowell, the reverse is true.
  • Physical properties of fat: the softer the fat, the more the fat loss and vice versa.
  • Condition ofcooling and ageing: insufficient cooling and ageing i.e. improper crystallization causes more fatloss and vice versa
  • Conditions ofchurn: overloading, gross under loadingand under churning all a cause a greater fat loss in butter milk.

Washing

When thecream has been churned the churn is stopped in the proper position, adrain-plug fixed and the buttermilk removed thorough sieve.

The purpose of washing is

  • Remove allloose buttermilk adhering to butter grains so as to reduce the curd content ofbutter, thereby improving its keeping quality.
  • To correctd efects in the firmness of butter by proper adjustment of wash watertemperatures, and
  • To deceasethe intensity of certain off flavours

After buttermilk has been drained chilled water is added to the butter grains in thechurn. The temperature of water isusually1-2 ° C lower than the churning temperature of cream and an amount equal to the quantity of buttermilk removed. Normally one wash isenough for good quality butter. The quality of water should be physically clean and bacteriologically and chemically safe. It is better to use freshly pasteurized and cooled water.

Salting

  • Refers to addition of salt to butter.
  • To improve keeping quality
  • To enhance the taste.
  • To increase overrun. Salt is usually added at therate of 2.0-2.5 % of the butterfat. Excessive salt damages the quality of butter.
  • The calculated amount of salt may be added to butter eitherby sprinkling the powder salt over the butter surface during working or it may be wetted in the least amount of potable water and then sprinkled over the butter during working. The salt is added in the form of a saturated solution of brine.

Specifications of butter salt

  • The saltshould be a coarse grained and free from lump. It should pass completely through and IS sieve-85 (aperture 842 microns).99.5 –99.85 % sodium chloride on dry matter. Bacterial counts less than 10/kg.Completely soluble. High rate of solution. Negligible sediment.

Working

This refers to the kneading of butter

Objectives

  • To completely dissolve, uniformly distribute and properly incorporate the salt.
  • To expel buttermilk and to control the moisture content of butter,
  • To fully incorporate the added makeup water in butter.
  • To bring the butter grains together into a compact mass for convenient handling andpackaging.
  • During working, the moisture in butter is reduced todroplets of microscopic size, which are mostly sterile.
  • The working should be continued until the butter has acompact body, closely-knit grain, a tough waxy texture, and an even distribution of salt and moisture. Indicator paper develops a coloured spot if free moisture is present.Both over working and under working should be avoided; the over working damages the body and texture of butter and under working produces leaky butter. Working increases the air content ofbutter. Normally worked butter has anair-content of 0.5-10ml/100 g. The air content of butter is important because it affects I) the density of butter ii) its microbial spoilage; and iii) itsoxidative spoilage.

Keeping quality of butter

The factors affecting the keeping quality are

  • Temperature of storage
  • Copper and iron content the higher the content the lower the salt content of butter keeping quality.
  • Acidity content of butter
  • Curd content of butter
  • Air contentof butter.
  • Raw orpasteurized cream: pasteurization of cream increases the keeping quality.
  • The method ofpackaging: sanitized high quality packaging materials and sanitary methods ofpackaging increase the keeping quality and vice versa
  • Exposure tolight lowers the keeping quality
  • Sweet cream/unsalted butter has the maximum and acid cream /salted butter the minimum keeping quality under commercial cold storage.

Over run in butter

  • Over run may be defined as the increase in the amount ofbutter made from a given amount of fat. It is usually expressed as a percentage. Over run is caused by thepresence of moisture, curd, salt etc., in butter. It is a source of profit to the butter makerand helps to check the efficiency of factory operations

Types

Theoreticalover run

  • Maximumobtainable, viz.25%. Since the minimum legalfat content of butter is 80%, the maximum amount of butter that can be madefrom 100 kg of fat are 100/80x100=125kg. This gives an overrun of 25 %, which is not obtainable in actualpractice.

Actualover run

On the basisof fat actually bought and butter made there from.

  • Factorsinfluencing over run
  • Inaccuracy in weight, fat test of milk, creamor butter
  • Fat losses in skim milk or buttermilk
  • Mechanical fat losses
  • Unavoidable fluctuations in the fat contentof butter
  • Weight allowances in butter packs or cream orbutter
  • Handling losses etc.

Formula for calculation of overrun

% OR = ( B-F / F) X 100

Where

OR= overrunin butter

B= buttermade(kg)

F= fat inchurn (kg).

Yield of butter

This is calculated by the formula:

F X ((100+%OR) / Y ) x  100

Where

Y = yield of butter(kg)

F = fat content ofcream. (Kg)

%OR = Percentage over run in butter (Ave. 20-22).

Theories of churning

They are three main theories on the churning of cream in tobutter. Viz.

  • Fisher and Hooker’s phase reversal theory
  • Rahn’s foam theory
  • King’s modern theory.

Fisher and Hookers Phase Reversal Theory

  • According tothis theory, churning is a process of phase reversal, i.e. changing anoil-in-water type emulsion to a water-in-oil type emulsion such as butter. Agitation of cream in the churning processcauses coalescence and clumping of fat globules until eventually the ratio ofthe surface area to the volume of fat units becomes so small that it can nolonger contain all the buttermilk in stable form. The fat-in-water emulsion then suddenlybreaks, yielding butter grains and free buttermilk.

Drawback

  • Butter is not true water in fat emulsion. Microscopicstudies reveal that a proportion of fat globules in butte is still intact inthe worked butter.

Rahn’s Foam Theory

  • According tothis theory, the presence of foam/froth is essential for churning. It also postulates that there is a foam producing substance present in cream, which gradually solidifies as the cream,or milk is agitated. Foam is created during the churning period. The fat globules due to surface tension effect tend to concentrate and clump on thefoam bubbles. The foam producing substance assumes a solid character and the foam collapses. The fat globules then coalesce and butter isformed.

Drawbacks

  • Foamformation is not required in some continuous butter making processes.

King’s Modern Theory

According tothis theory,

  • In cooledcream at churning temperature, the fat is present as clusters of fat globules;and within each globule it is present partly in liquid and partly in solidform.
  • Churningbreaks up the cluster and cause foam/ froth formation. The globules become concentrated to some extent in the film around the air bubbles in the foam and are thus brought intoclose contact with each other.
  • The movementof the globules over one another in the foam film and the direct concussion between them causes a gradual wearing away of the emulsion protecting surfacelayer of the phospholipid protein complex. The globules then adhere together to form larger and largerparticles. Eventually these particlesbecome visible as butter grains. As the granules form , they enclose some of the air from the foam. The fat in thegranules is still mainly in globular form.
  • The working of butter grains cause the globules to move overone another, under the effect of friction and pressure, some of them yield up aportion of liquid fat. Others are broken up during working. Finally there is enoughfree liquid fat present to enclose all the water droplets, air bubbles andintact fat globules.

Continuous butter making (CBM)

  • A number of types of continuous butter making machines havebeen developed for commercial use.

Advantages of CBM

  • Moreeconomical due to lower capital cost, lower running cost (reduced power,labour, refrigeration, steam, detergent etc.,).
  • Reduced floorspace, no expensive foundations to prepare, no time loss for fatcrystallization, less in butter wastage, etc.,
  • More hygienicdue to it’s being a closed system, free from air borne contamination.

Disadvantages

  • Lack ofuniformity on the quality.
  • Difficulty ingrading and analysis.

Basic principles

The continuousmethods of butter production developed since 1935 may be divided into threemain groups.

  • Groups I
    • Fritz process or churning process: this involves the use ofhigh-speed beaters to destabilize the fat emulsion in the chilled cream, andthus cause the formation of grains of butter in matter of seconds. Thebuttermilk is drained away and the resulting grains worked in a kneadingsection prior to extrusion.
  • Group II
    • Alfa-Laval process or the concentration and phase reversalprocess. This involves a system whereby cream of 30-40 per cent fat is concentrated in a special cream separator to 80-82% fat. After standardization, the concentrated creamor butter mix is subjected to combined cooling and mechanical action, whichcauses phase reversal and the formation of butter, followed by its expulsionfrom the machine.
  • Group III
    • Cherry Burrell process which again involves the concentration of 30-40 % cream. During concentration, the emulsion is broken and the fat, water, and salt content are standardized. This is followed byre-emulsification, cooling working, and finally extrusion.

Defects in butter, their causes, and prevention

  • Defects in butter may arise due to low quality milk orcream, and faulty method of manufacture and storage of butter. The common defects in butter, their causes,and prevention are given below.

Uses of butter

  • Direct consumption .
  • In the preparation of sauces.
  • As a cooking medium
  • In the baking and confectionery industries.
  • In the manufacture of Ice cream, butter oil and ghee.
  • In the production of reconstituted milk.
Last modified: Tuesday, 19 June 2012, 5:42 AM