MANUFACTURE OF DAIRY PRODUCTS

MANUFACTURE OF DAIRY PRODUCTSDR ATHIRA PRAKASH14-MVM-06

BUTTER

Definitions As per FSSAI (2011), Butter means the fatty product derived exclusively from milk of cow and/or buffalo or its products principally in the form of water-in-oil type of an emulsion. Product may be with or without added common salt and starter cultures of harmless lactic acid and/or flavour producing bacteria.Table butter shall be obtained from pasteurised milk and/or other milk products which have undergone adequate heat treatment to ensure microbial safety.

It shall be free from animal body fat, vegetable oil and fat, mineral oil and added flavour. It shall have pleasant taste and flavour free from off flavour and rancidity. It may contain food additives permitted in these Regulations It shall conform to the microbiological requirements of the regulation. It shall conform to the microbiological requirements of the regulation.

FSSAI standards for butter Product Moisture Milk FatMilk solids not fatCommon saltTable Butter16.0% (w/w, max.) 80.0% (w/w, min.)1.5% (w/w, max.)3.0% (w/w, max.)Desi /cooking butter---76.0% (w/w, min.) ------

Permitted food additives in butter as per FSSRAdditiveQuantityColours (natural: singly or in combination) Curcumin100 ppm maxBeta carotene100 ppm maxCarotene (natural extract)100 ppm maxAnnatto extract on bixin/nor bixin basis (50:50)20 pm maxBeta apo-8 carotenal35 ppm maxMethyl ester of beta apo-8 carotenoic acid35 ppm maxAcidity regulatorsSodium and calcium hydroxide2000 ppm max

Microbiological requirements of pasteurized butter Microbiological parametersSampling planCountTotal plate countm10,000/gM50,000/gColiform countm10/gM50/gE.coliMAbsent/gSalmonellaMAbsent/gStaphylococcus aureusm10/gM50/gYeast and mould countm20/gM50/gListeria monocytogenesMAbsent/g

BIS standards for pasteurized butter Characteristic Table butterWhite butterMilk fat, per cent by mass (min.)8082Moisture, per cent by mass (max)1616Acidity (as lactic acid), per cent by mass (max).15.06Curd, per cent by mass (max)11.5Common salt, per cent by mass,(max)2.5---Coliforms, per ml, (max)55Yeast and mould count, per ml, (max)2020

CODEX STANDARDS OF BUTTER Butter is a fatty product derived exclusively from milk and/or products obtained from milk, principally in the form of an emulsion of the type water-in-oil. Butter should be made from milk and/or products obtained from milk. Permitted ingredients Sodium chloride and food grade salt Starter cultures of harmless lactic acid and/or flavour producing bacteria Potable water.

Composition Minimum milk fat content 80% m/m Maximum water content 16% m/m Maximum milk solids-not-fat content 2% m/m The products should comply with any microbiological criteria established in accordance with the Principles for the Establishment and Application of Microbiological Criteria for Foods (CAC/GL 21-1997).

Composition of butter ConstituentsQuantity (% w/w)Fat80-83Moisture15.5-16Salt0-3Curd1-1.5

CLASSIFICATION OF BUTTER Based on acidity of cream used for butter making:Sweet cream butter : made from non-acidified cream; having pH of 6.4Mildly acidified butter: made from partially acidified sweet cream, having pH in the range of 5.2 to 6.3.Sour cream butter: made from ripened cream which has more than 0.2% acidity, having pH 5.1.

Based on salt content :Salted butter: Butter to which salt has been added. It is added to improve flavour and keeping quality of butter. Unsalted butter: This type of butter contains no salt. It is usually prepared for manufacturing other products such as ghee and butter oil

Based on end use (as followed by BIS): Table Butter: made from pasteurized cream obtained from cow or buffalo milk or a combination thereof with or without ripening with the use of standard lactic culture, addition of common salt, annatto or carotene as colouring matter and di-acetyl as flavouring agent. White Butter: made from pasteurized cream obtained from cow or buffalo milk or a combination thereof without ripening and without addition of any preservative including common salt, any added colouring matter or any added flavouring agent.

Based on the manufacturing practice (as followed by FSSAI): Pasteurized cream butter/ Pasteurized Table butter: This is made usually from pasteurized sweet cream. Such butter usually has a milder flavour than that made from similar cream not pasteurized. Desi butter: The butter obtained by traditional process of churning dahi or malai as practiced at domestic levels.

Cream preparation for Butter Manufacturing

Butter Manufacturing

Neutralization of creamSour cream must be neutralized to make butter of good keeping quality. By neutralization of cream acidity of cream is reduced. Churning of High acid cream may cause high fat loss which can be prevented by neutralization. In pasteurization of sour cream, the casein curdles, by entrapping fat globules, as the bulk of curd goes in butter milk, causing high fat loss.

Objectives of neutralizationTo reduce the acidity in cream to a point (0.14 -0.16%) which permits pasteurization without risk of curdling, to produce butter which keeps well in cold storageTo avoid excess loss of fat which result from the churning cream i.e. excessively sour.To guard against undesirable flavors which may result when a cream of high acid which is subjected for pasteurization at higher temperatures.To improve the keeping quality of butter from high acid cream. Salted-acid-butter develops a fish flavor during commercial storage at -23 to -29C.

Factors affecting neutralizationAccurate neutralization of sour cream is important to get a desired quality product. Accuracy in sampling. Accuracy in testing. Accuracy in estimation of amounts of cream and neutralizer. Careful weighing the quantity of neutralizer. Thorough mixing of neutralizer in cream prior to pasteurization.

Method of neutralization of cream There are five essential steps to follow for cream neutralization. These are: Adoption of definite standard of churning acidity Correct estimation of acidity Calculating the amount of neutralizer to be added Adding neutralizer in the correct manner Checking results by re-testing acidity

Adoption of a definite standard of churning acidityAcidity of cream at churning time controls the flavour and keeping quality of the butter. Therefore, it is important to decide that at what acidity the cream shall be churned.Churning acidity should be kept upto that maximum acidity where absence chemical deterioration of butter (fishy flavour) with age can be ensured. For cream of average richness (about 30%), fishy flavor can be prevented by keeping the churning acidity to 0.3% maximum.The safe maximum limit of churning acidity varies with the richness of the cream.

Correct Estimation of AcidityRepresentative sample should be taken. Weight of cream should be accurately measured as the final amount of neutralizer will be dependent on the weight of cream.Effect of CO2 on acidity should be taken care especially in high acid cream (acidly> 0.65%)

Calculating the amount of neutralizer to be added

Adding neutralizer in the correct manner Neutralizer should be dissolved or emulsified in clean water, diluted to approx. 20 times its weight with water.The solution must be distributed quickly & uniformly throughout the entire batch of cream and mixed thoroughly with cream. For efficient mixing, neutralizer is usually sprayed onto the surface of well agitated cream. While the neutralizer is added, the cream should be agitated vigorously and continuously. Agitation of cream is preferable for 5-10 min after neutralization. Temperature at the time of neutralization should be 30oC.

Checking Results of Neutralization by Re-testing for AcidityAcidity should not be checked immediately after neutralization because of the following reasons:In case of lime and Magnesia neutralizers, the neutralizing action is slow. It completes after pasteurization & cooling.In case of soda neutralizers, CO2 is liberated and this reacts acid toward the phenolphthalein indicator. After pasteurization, expulsion of CO2 is largely accomplished. Therefore, testing acidity after pasteurization would give correct results

Type of NeutralizersNeutralizers in order to accomplish the purpose, for which they are used in the creamery, must have alkaline properties. They must be alkalis, alkaline earths or their substances.The neutralizers used for reducing acidity in cream belong to either one or the other of two groups namely. Lime NeutralizersSoda Neutralizers

Lime neutralizers:The principal constituent of the majority of lime neutralizers is calcium. Many of the lime neutralizers available for cream neutralization also contain some magnesium. The various commercial lime neutralizers differ from one another chiefly with respect to the proportion of calcium and magnesium they contain.

Cont..They are conveniently placed in three groups, as follows:Low magnesium limes: Containing 5% or less of magnesium. A well Known brand of creamery lime belonging to this group is peerless lime.Medium magnesium limes: Containing about 30-35% magnesium. To this group belong such brands as Kelly Island lime, Neutra-Lac and Neutra-Lime. High magnesium limes: Containing about 45 to 55% magnesium. All wood lime is an outstanding representative of this group. All magnesium limes in the form of magnesium oxide and magnesium carbonate are also available. They are artificially prepared limes

Soda neutralizers:Soda neutralizers commonly used in the creamery are: Bicarbonate of soda or baking soda Sodium carbonate or soda ashMixtures off baking soda and soda ash, such as Sodium sesquicarbonate, Neutralene and Wyandotte

Standardization of Cream Adjustment of fat to desired level .Done by adding calculated quantity of skim milk or butter milk. Desired level of fat in cream for butter making is 33 to 40 per cent. Standardization to both higher and lower level leads to higher fat loss in butter milk.

Pasteurization of Cream Adjustment every particle of cream to a temperature not less that 71C and holding it at that temperature for at least 20 min or any suitable temperature-time combination using properly operated equipment. A number of equipment can be employed for this purpose.More severe heat treatment of cream should be avoided Pasteurization of cream for making ripened cream butter is commonly carried out at higher temperature than for sweet cream butter e.g. 90-95C for 15 or 105-110C with no holding.

Ripening of Cream Process of fermentation of cream with the help of suitable starter culture.Can be eliminated if sweet-cream butter is desired.Main object of cream ripening is to produce butter with higher di-acetyl content. Starter culture consisting of a mixture of both acid producing (Streptococcus lactis, S.cremories) and flavour producing (S.diacetylactis, Leuconostoc citrovorum and/or Leuc. dextranicum) organisms is added. Amount of starter added usually ranges between 0.5-2.0 per cent of the weight of the cream

After thoroughly mixed, the cream is incubated at about 21C till desired an acidity is reached. Cream is subsequently cooled to 5-10C to arrest further acid development. Biosynthesis of diacetyl is not sufficient above pH 5.2. Stopping fermentation of cream by cooling at pH 5.1-5.3, results in a milder flavour; whereas continuing fermentation upto pH 4.5-4.7 results in higher levels of both diacetyl and lactic acid, giving more pronounced flavour

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Starter cultureMixture of both acid producing organisms (Lactococcus lactis, L. cremoris) and flavour producing organisms (S. lactis subsp. diacetylactis, Leuconostoc citrovorum and/or Leuconostoc dextranicum) is used. Starter culture is added at the rate of 0.5 to 2.0% of the weight of cream and incubated at about 21oC till desired acidity is reached. Usually it takes 15-16 hrs

Cooling and Ageing Processes which prepare the cream for subsequent operation of churning. When cream leaves the pasteurizer, the fat in the globule is in liquid form. When cream is cooled, fat crystallization starts, cream will not churn unless the butter fat is at least partially crystallized. If solidification of fat is not sufficient, the fat losses in butter are high.

The temperature to which cream is cooled is chosen is such a way that the butter produced is of optimum consistency and cream churns to butter in a responsible time of about 35-45 minutes. Churning at too high temperature may give butter with greasy body which may work up too quickly and become sticky. Generally cooling temperature in summer should be 7-9C and that of in winter 10-13C.

CHURNING OF CREAM The sequence of events that occur during churning is as follows: Churning is initiated by agitation of cream causing incorporation of numerous air bubbles into the cream. With incorporation of air there is increase in the volume of cream and air plasma interface. Surface active (such as frictional, impact, concussion etc.) causes partial disruption of fat globule membrane The fat film, thus formed, serve as a foam depressant causing the air bubble to burst. The liquid fat also serves as cementing material causing fat globules to clump together and eventually butter grains are formed which floats in plasma i.e. butter milk.

Initial Working:Working of butter is essentially a kneading process in which butter granules are formed into a compact mass. During this operation, any excess moisture or buttermilk is removed. However, the emulsion (w/o) at this stage is not fully stable.

Salting of Butter In conventional process, butter may be salted by adding salt to butter churn after initial working of butter. Salt to be added must be high quality e.g. IS 1845:1961, with low level of lead, iron and copper. It should be 99.5 to 99.8% sodium chloride and microbial count should be less than 10/g. Salt sets up osmotic gradient which draws water from the butter grains. This can lead butter to be leaky. Salted butter should therefore, must be thoroughly worked. Salt may be added either in dry form or as saturated brine solution.

Adjustment of Moisture After the addition of salt, the moisture content in butter is adjusted by adding calculated amount of additional water. In most countries, maximum limits of 16% is placed on the level of moisture. Starter distillates, if required, may also be added at this stage to enhance the flavour of resultant butter, if cream has not been cultured.

Final Working of Butter: The objective is to incorporate moisture and uniformly distribute added moisture and salt in butter.During this process remaining fat globules also break up and form a continuous phase, and moisture is finally distributed to retard bacterial growth in butter. Moisture droplet size normally ranges from 1 to 15 micron and there are approximately 10 billion droplets per gram of butter. Air content of conventional butter range from 3-7% by volume with an average of 4 ml/100 while that of vacuum worked butter it is about 1 ml/100g.

EVAPORATED MILK

The product obtained from cow or buffalo milk or a combination thereof or from standardized milk by partial removal of water.May contain calcium chloride, citric acid and sodium citrate, sodium salts of ortho-phosphoric acid and poly-phosphoric acid not exceeding by 0.3% by weight of the finished product.Shall contain not less than 8% milk fat and 26% milk solids.

Composition of evaporated milkComponentPercentageMoisture69Total solids31Fat9Milk SNF22Protein8.3Lactose12.2Ash1.5Total milk Solids31

Standards CharacteristicsrequirementsEvaporated milkEvaporated partly skimmed milkEvaporated skim milkEvaporated high fat milkTotal milk solids (min)26202027Fat % by massNot < 8Not > 8& Not < 1Not > 1Not < 15

Milk protein in milk SNF (min)34343434

Manufacture Receiving milkFiltration / clarificationStandardizationFore warming / pre heatingEvaporationHomogenisation first stage (2000 psi)Second stage (500 psi)Cooling

Cont..Pilot sterilization test (117C, 15 mins)PackagingSterilization (116-118C, 15 mins)CoolingShakingStorage

Filtration/clarification : to remove the visible foreign matter at a temperature of 35-40C, and then cooled.StandardizationStandardization of the raw milk is carried out in 3 stages,For desired fat/SNF ratio, (usually 1:2.44, done in raw milk)Desired ratio of added sugar to the total milk solids (done prior to condensing)To adjust the concentration of the finished product to the required total solids content (after finishing the batch, i.e, prior to homogenization).

Fore warming/Pre-heating:Done for making the finished product free from microorganisms and enzymes.To ensure uninterrupted boiling in pan To control age thickening in the finished product. The time temperature combination varies over 82-93C for 5-15 minutes or 115 118C for no hold. Tubular heat-exchangers are commonly used.

Evaporation:Means the concentration of milk or liquid products. Milk is passed through steam heated tubes under vacuum Correct concentration of solids density 1.07No sugar is added here and normally a continuous operation takes place. It is customary to slightly over-condense the milk to facilitate standardization later.

Homogenization:After evaporation and before cooling, the evaporated milk is thoroughly homogenized to obtain a uniform fat emulsion and reduce separation of fat to a minimum during storage. The temperature is usually 49 C as the product is removed from the last part of the evaporator. Two-stage homogenization is generally recommended, 2000 psi in the first stage and 500-psi in the second stage. After which the samples are cooled to 7 C and stored.

Pilot sterilization test:Purpose is to determine the amount of chemical stabilizers (tri sodium citrate or di sodium phosphate) to be added to any given batch of evaporated milk for the most satisfactory heat stability.The amount of stabilizers to be added to any batch is determined by trial. The sample cans containing measured amount of stabilizer solution and a fixed quantity of evaporated milk are sterilized at 117 C for 15 minutes and then cooled rapidly to 24 CAs soon as they have been cooled the cans are opened, examined for smoothness and colour and tested for viscosity.

According to Mojonnier and Troy, a viscosity of 150R on the Mojonnier-Doolittle viscosimeter represents the correct viscosity of evaporated milk as it comes out of the sterilizer.If the viscosity tests for pilot sterilized can show that no stability correction is necessary, the batch is ready to be filled into the cans. However if the tests show otherwise, stability corrections becomes necessary.Based on the pilot sterilization test, the calculated quantity of stabilizer should be added to the evaporated milk in the form of a solution using just enough water to dissolve it.

PackagingThe cans are now mechanically filled with volumetric fillers, the types of one used for this purpose are the sanitary can, the can with a solder seal, and the vent hole can. The temperature of evaporated milk when filling the cans should be neither high nor low, but around 5 C; a higher temperature cause foaming; while a lower temperature increases the tendency towards flipping. The cans should be filled as nearly full as possible.

Sterilization:Immediately after sealing and before sterilization, each can is tested for any leakage using leak checker /detector, where the cans pass submerged in a hot-water bath. In case of leaky cans, air bubbles rise to the top: these cans are removed for repair. The filled and sealed cans, which have passed the test for leaks, are ready for sterilization. The purpose of sterilization is to destroy all germ life and enzymes present, thereby preserving the product permanently. During sterilization, the temperature is raised to 116-118 C and held at this temperature for 15 minutes. If the cans cannot be sterilized within an hour or two, they should be then held under refrigeration.

Batch method :This consists of a water steam boiler-like, horizontal steam drum, with hollow interior having a revolving frame, in which the cans are loaded. The sterilizer rotates at 6-12 rpm, with uniform distribution of heat.Continuous method:Here the cans are progressively heated to a few degrees below the boiling point, and finally enter the sterilizing area proper. Later cooling process starts with the cans gradually moving through progressively less hot-water chambers and finally through cold water.

CoolingImmediately after holding time is over, the evaporated milk is cooled within 15 minutes to 27-32C. Rapid and uniform cooling is important. Bulging of the cans can be avoided by using cold water and in continuous system, cooler operates at 10 psi.Shakingdone to break mechanically, any curd, which might have formed during the process of sterilization to a homogenous smooth consistency.

StorageThough evaporated milk can be stored at room temperatures, a storage temperature of 5-16 C is generally used, which helps to keep the product acceptable even up to 2 years. Inversion of cans once in 3-6 months during storage will help to minimize fat separation

CONDENSED MILK

Milks obtained by evaporating part of water of whole milk, or fully or partly skimmed milk, with or without the addition of sugar.The term condensed milk is commonly used when referring to full cream sweetened condensed milk.Skimmed milk products are known as sweetened condensed skim milk and unsweetened condensed skim milk.The ratio of concentration of milk solids is about 1:2.5 for full cream products and 1:3 for sweetened condensed skim milk.

According to the PFA (1976) the various condensed milks have been specified as follows:Unsweetened condensed milk (evaporated milk) : the product obtained from cow or buffalo milk or a combination therefore, or from standardized milk, by the partial removal of water. It may contain added calcium chloride, citric acid and sodium citrate, sodium salts of ortho-phosphoric acid and poly-phosphoric acid not exceeding 0.3 per cent by weight of the finished product. Such addition need not be declared on the label. Unsweetened condensed milk should contain not less than 8.0 per cent milk fat, and not less than 26 per cent milk solids.

Sweetened condensed milk : the product obtained from cow or buffalo milk or a combination thereof, or from standardized milk, by the partial removal of water and after addition of cane sugar. It may contain added refined lactose, calcium chloride, citric acid and sodium citrate, sodium salts of ortho-phosphoric acid and poly phosphoric acid not exceeding 0.3 per cent by weight of the finished product. Such addition need not be declared on the label. Sweetened condensed milk should contain not less than 9.0 per cent milk fat, and not less than 31 per cent milk solids and40.0 per cent cane sugar.

Unsweetened condensed skim milk (evaporated skimmed milk) : the product obtained from cow or buffalo milk or a combination thereof, by partial removal of water. It may contain added calcium chloride, citric acid and sodium citrate, sodium salts of ortho-phosphoric acid and poly phosphoric acid not exceeding 0.3 per cent by weight of the finished product. Such addition need not be declared on the label. Unsweetened condensed skim milk should contain not less than 20.0 per cent total milk solids. The fat content should not exceed 0.5 per cent by weight.

Sweetened condensed skim milk : the product obtained from cow or buffalo skimmed milk or a combination thereof by the partial removal of water and after addition of cane sugar. It may contain added refined lactose, calcium chloride, citric acid and sodium citrate, sodium salts of orthophosphoric acid and polyphosphoric acid not exceeding 0.3 per cent by weight of the finished product. Such addition need not be declared on the label. Unsweetened condensed skim milk should contain not less than 26.0 per cent total milk solids and not less than 40 per cent cane sugar. The fat content should not exceed 0.5 percent by weight.

Composition of condensed milkCondensed milkSkim sweetenedwater2629Total solids7471Fat90.5Milk solids not fat2225.5Protein8.39.3Lactose12.214Ash1.52.2Total milk solid3126Sucrose4345

Indian Standard Specifications for condensed milkCharacteristicsRequirement forCondensed milkSkim sweetenedTotal milk solids (%wt.) Min3126Fat (% wt)Not less than 9Not more than 0.5Sucrose (% wt.) min4040Acidity (% lactic) max0.350.35Bacterial count (per g)500500Coliform count (per g)NegativeNegative

Yeast and mould count (per g.) Max1010

Manufacture of condensed milkReceiving milkFiltration /Clarification (38-40C)StandardizationFore warming/preheating (115-118 C / No Hold)Condensing (2.5:1)Addition of sugar

Cont..HomogenizationQuickly cooled to 30CSeeded with 0.1 - 0.3% lactoseVigorous stirring and slow cooling for 1 hour.Temperature of 15 c reachedStirring continued until packed.Storage at 10 c.

The basic principle in the production of condensed milk and evaporated milk is that high quality milk is filtered /clarified, standardized, fore-warmed and condensed /evaporated to the desired level. The concentrated product is preserved by the addition of sugar for condensed milk and by heat sterilization for evaporated milk.When the milk is received at the plant, its temperature should be at 10C or below. The milk should be clean, sweet, and free from off-flavours and odours and reasonably free form extraneous material.

Filtration/clarification: This is done in order to remove the visible foreign matter at a temperature of 35-40C, and then cooled.First standardization: the ratio of milk fat to non fat solids is adjusted so that compositional quality requirements for the final product are met.Yield and quantity of the final product depends on this step.It establishes desired ratio of fat:SNF in milk.It is carried out by the addition of milk with different fat contents, such as skim milk or cream, based on the requirement of the final product.

Preheating: heat treating the milk before it is concentrated.it is required to destroy all pathogenic and potential spoilage organisms, to inactivate all enzymes and regulate viscosity and age thickening.Additional consequences of the thermal processing are:The decrease of milk fat separation.The retardation of oxidative changes.Economic and technological effects.The time temperature combination varies over82-93C for 5-15 minutes. Tubular heat exchangers are commonly used.

Homogenisation: Not always applied.Depends on the product type, market (shelf life) and preference of the manufacturer.If the product need to be shelf-stable it should be homogenized at a pressure of 5-10 MPa.Also it helps to regulate viscosity.Recombined sweet condensed milk is always homogenised.

Condensation: usually done by evaporation, but reverse osmosis can also be used.Same as that for evaporated milk.Usually condensed in a multistage falling film evaporator.Because of the high viscosity of the product, evaporators are usually equipped with a finisher, in which the concentrate is reheated before concentrating into final solids content.Otherwise flow of the product over evaporator will not be uniform resulting in fouling and low heat transfer.

Addition of sugar: sugar can be dissolved in cold milk before pre heating.Microorganisms present in the milk will be killed in pre heating.But adding sugar will make the process of evaporation more difficult.Alternative method is addition of sugar after pre heating or at the end of the condensing.If sugar as added as a syrup it should be properly heat treated to kill osmophilic yeasts.

Refined cane sugar or beet sugar is used in the manufacture of sweet condensed milk.Sucrose must be microbiologically approved, with no acids or invert sugar.Advantages of sucrose good solubility, low susceptibility to fermentation, and user preference.One method of addition of sugar is running a part of fore warmed milk into a sugar mixing pan where sugar is mixed in a fine stream with proper agitation.The sweetened milk is then drawn into the vacuum pan.

Another method is to dissolve sugar by boiling in water in a separate tank called sugar well.This is then added to milk in the vacuum pan towards the end of evaporation process.Disadvantage additional water need to be removed from added sugar solution.

Striking the batch: refers to the end of concentration operation in the vacuum pan.Determined by specific gravity or density test.The dry matter content which is acquired by the evaporation step is determined by determining the density of the concentrate.Should be 1.30 for SWM and 1.35 for SSM when the correct dry matter has been reached.Baume hydrometer or a viscometer is used to determine the progress of concentration.

Hydrometer scale record the density.For condensing milk Baume reading ranges from 30-37 Be at 49C.When desired concentration as indicated by Baume reading is reached milk is removed from the pan striking the batch.Second sterilization: final standardization.Carried out after evaporation and sugar addition. During this stage total solids, sugar and milk fat content are controlled.

Cooling: essential to control the texture of SCM.Most critical and most important stage.The quantity of sugar that milk can carry in solution varies according to the temperature of milk.The water in the condensed milk can hold only half of the lactose in solution.Remaining will be allowed to precipitate in the form of crystals.If surplus lactose is allowed to precipitate freely gritty and unsuitable product.Largest crystal permitted in first grade milk - 10m.They remain dispersed under normal temperature (15-25 C) and are not felt on the tongue.

Forced crystallization: to produce mass crystallization of lactose.Before seed lactose is added condensed milk must be cooled to a temperature where lactose will be supersaturated seed lactose will not dissolve.After seeding the cooling should be continued to crystallize the lactose.A vacuum cooler is used in which a thin layer of milk passes the wall of the vat that is under vacuum.Alternatively it can be cooled in a scrap surface heat exchanger.

Seeding : crystallization of lactose is usually assisted by the addition of fine powder of lactose or small quantity of condensed milk from previous batch in which lactose crystals are in minute form.other alternative is to use spray dried skim milk powder as seed material.Seeding refers to the addition of fine spray of lactose during cooling so as to provide nuclei for crystallization.The purpose is to give lactose an added incentive to crystallize.Recommended amount of finely pulverized lactose for seeding is 375-500 per 1000 kg of initial milk taken or 0.1-0.3% of condensed milk.

Required amount of seed lactose is blended with small quantity of condensed milk and then added to the batch with vigorous agitation at 30CAfter forced crystallization and seeding, cooling is continued slowly to 24-25C for about an hour or longer.Robust agitator is needed as viscosity of condensed milk is very high.Packaging:For large quantity / bulk transport barrels of size varying from 50-300 kg.Retail sale cans of various sizes ranging from 200 g to 5 kg

MILK POWDER

Dried milk or milk powder is the product obtained by removal of water from milk by heat or any other suitable means to produce a solid containing 0.5% or less moisture.Whole milk, partly skimmed milk or skim milk can be used for drying.

CLASSIFICATIONBased on the type of drier:Spray driedRoller driedFreeze dried.Based on fat content of milk:Skim milk powderPartly skim milk powderWhole milk powder

Heat applied for drying of milk:Low heatMedium heatHigh heatBased on method of manufacture:InstantizedFoam dried

COMPOSITIONWHOLE MILK POWDERSKIM MILK POWDERMoisture34Fat271Protein2635Lactose3851.5Ash68

Legal standards - PFAMilk powder : the product obtained from cow or buffalo milk or a combination thereof , or from standardized milk, by the removal of water.It may contain added calcium chloride and sodium citrate, sodium salts of ortho-phosphoric acid, and poly-phosphoric acid, not exceeding 0.3% of the weight of the finished product and 0.01% of BHA by weight of finished product.It may contain lecithin to a maximum limit of 0.5%.It shall contain not more than 5% moisture and not less than 26% fat.The maximum acidity expressed as lactic acid shall not be more than 1.2%.Plate count shall not exceed 50,000/g and coliform shall be absent in 0.1g of the powder.

Skimmed milk powder: the product obtained from cow or buffalo milk or a combination thereof , or from standardized milk, by the removal of water.It may contain added calcium chloride and sodium citrate, sodium salts of ortho-phosphoric acid, and poly-phosphoric acid, not exceeding 0.3% of the weight of the finished product It shall contain not more than 5% moisture and fat not more than 1.5%.The maximum acidity expressed as lactic acid shall not be more than 1.5%.Plate count shall not exceed 50,000/g and coliform shall be absent in 0.1g of the powder.

Partly skimmed milk powder: the product obtained from cow or buffalo milk or a combination thereof , or from standardized milk, by the removal of water.It may contain added calcium chloride and sodium citrate, sodium salts of ortho-phosphoric acid, and poly-phosphoric acid, not exceeding 0.3% of the weight of the finished product It shall contain not more than 5% moisture and fat content should be more than 1.5% and less than 26%. 0.01% of BHA by weight of finished product could be added.The exact fat content shall be indicated on the label.

BIS STANDARDSMILK POWDER (IS:1165-2002)CharacteristicsRequirementsMoisture % by mass, max4Total milk solids % by mass, min96Fat, % by mass, min26Insolubility index, max2 mlTotal ash, % by mass , max7.3Titratable acidity, % by mass, max1.2Bacterial count/g, max40,000Coliform countAbsent in 0.1 gStaphylococcus aureusAbsent in 0.1gSalmonella & shigellaAbsent in 25g

SKIMMED MILK POWDER (IS:13334 (part I)-1998)CharacteristicsRequirementsMoisture % by mass, max4Total milk solids % by mass, min96Fat, % by mass, min1.5Insolubility index, max15 (roller dried), 1.5( spray dried)Total ash, % by mass , max8.2Titratable acidity, % by mass, max1.5Bacterial count/g, max50,000Coliform countAbsent per 0.1 g

EXTRA GRADE SKIMMED MILK POWDER (IS:13334(part II)-1992)CharacteristicsRequirementsMoisture % by mass, max3.5Total milk solids % by mass, min96.5Fat, % by mass, min1.25Insolubility index, max0.5 mlTotal ash, % by mass , max7.3Titratable acidity, % by mass, max1.5Bacterial count/g, max40,000Coliform countAbsent in 0.1 gStaphylococcus aureusAbsent in 0.1gSalmonella & shigellaAbsent in 25g

PARTLY SKIMMED MILK POWDER (IS: 14542-1998)CharacteristicsRequirementsType IType IIMoisture % by mass, max44Total milk solids % by mass, min9696Fat, % by mass, min1.5261.526Insolubility index, max15(RD),1.5 (SD)---Total ash, % by mass , max8.28.2Titratable acidity, % by mass, max1.51.5Bacterial count/g, max50,00050,000Coliform countAbsent in 0.1 gAbsent in 0.1 g

Manufacturing of milk powderStandardization:The objective is to adjust the ratio of milk fat and total solids to the level required for the final product.Pre heat treatment: is done for the production of safe and better stable milk powders and also for inducing in it other desirable attributes.Usually carried out at a temperature higher than that for pasteurization.

Main objectives of pre heat treatment :To destroy all pathogenic bacteria and most of the saprophytic organisms.To inactivate enzymes, especially lipase.To activate SH groups of - lactalbumin , thus increasing resistance to the oxidative changes during storage.It also contributes to the shelf lie of the product primarily through the development of antioxidant or reducing substances.Most commonly followed heating regime is 88-95C for 15-30 seconds.

Evaporation: compulsory step in powder processing.Milk powder produced from evaporated milk has longer shelf life and large powder particles.Also help in reducing the duration of drying process.For this purpose , a continuous multiple effect evaporator, usually of tubular type is used.For spray drying, milk is concentrated to 40-45% total solids, while for roller drying it is up to 18-20%.

Homogenization:Is not an obligatory process but is usually applied to decrease free fat content.It also helps to prevent clumping of fat during reconstitution and improves keeping quality of powder.It is conducted after evaporation or in partly concentrated milk.The customary homogenisation is at 2500-3000 psi at 63-75C.

Drying:A number drying process are followedSpray drying.Fluid bed drying.Drum drying.Batch drying in rays.Freeze drying.Microwave drying.Super heated steam drying

SPRAY DRYINGThe predominant method of drying milk and milk products.Basic principle is the exposure of a fine dispersion of droplets, created by means of atomization of pre-concentrated milk to a hot air stream.The small droplets created more surface area- faster evaporation of water and minimized heat damage.Spray dryer utilizes a product which is first pre concentrated in a vacuum pan or an evaporator, the product is then atomized inside a drying chamber of the dryer.

The most common method of atomization force the product by high pressure pump through the nozzle to assist the break up of the liquid.As the atomized product is introduced into the drying chamber, heated air is forced through the chamber.This air provides heat for evaporation and it also act as a carrier for moisture to be removed from the dryer.The air may be forced through the dryer either by air or by suction.Air and product is separated following drying.The product is then cooled and packed.

In nutshell, spray drying comprises of 5 essential sub processesAtomization of the feedMixing of the spray drying air.Evaporation.Separation of the product from drying air.Cooling of the powder.

ICE CREAM

Ice cream is a frozen dairy product made by freezing a mix with agitation to incorporate air and ensure uniformity and consistency.According to the PFA rules (1976) ice cream is the frozen product obtained from the cow or buffalo milk or a combination thereof or from cream and or on the milk products, with or without the addition of cane sugar, eggs, fruits, fruit juices , preserved fruits, nuts, chocolate, edible flavours and permitted colours. It may contain permitted stabilizers and emulsifiers not exceeding 0.5 per cent by weight.

The mixture must be suitably heated before freezing. The product should contain not less than 10%milk fat, 3.5% protein, and 36% total solids. However, when any of the aforesaid preparations contains fruits or nuts or both, the content of milk fat may be proportionately reduced but not less than 8 % by weight, starch may be added to a maximum extent of 5 %, with a declaration to that effect on the label.

CompositionISI specifications for ice cream are:

CharacteristicsRequirementsWeight (g/litre, min)525Total solids (% wt, min)36Milk fat (% wt, min)10 (tentative)Acidity (% lactic acid, max)0.25Sucrose (% Wt., max)15Stabilizers and emulsifiers (% Wt., max)0.5Standard plate count (per g)Not more than 2,50,000Coliform count (per g)Not more than 90

Manufacturing of ice creamIngredients:I.dairy productsSource of fatSweet cream: this is the most desirable concentrated source of fat for use in a mixFrozen creamPlastic creamUnsalted butterButter oil.Source of milk-solids- not fatSkim milk.

Skim milk powder-this is most frequently used in the spray dried or flaked form.Condensed skim milkSweet cream buttermilk.Sources of both fat and solids not fatWhole milk.Whole milk powderCondensed whole milkEvaporated milk

II.Non-dairy productsSweetening agentsCane sugar or beet sugar.Corn sugar (dextrose)Corn syrup solids (dextrose + maltose)Corn syrupInvert sugar (glucose +fructose)Saccharin.StabilizersGelatin-of animal origin .

Commonly gelatin is used at the rate of 0.25 to 0.5 % for a 250 bloom gelatin. The ice-cream mix stabilized with gelatin usually requires about 4 hours of ageing to develop complete stabilizing properties, while other stabilizing materials do not require an ageing period.The amount of gelatin used depends on several factors such as the source of gelatin whether from calf, pork skin or bonematerials.

Sodiumalginate of vegetable origin . The basic stabilizing principle algin is extracted from ocean kelp (seaweed) growing on the shores of California and in Japan. This product improves whipping ability and leaves a slightly cleaner flavour in the mouth. It dissolves properly only when added to the mix at about 68-71 C. Guargum of Indian origin.CarageenanAgar agar:Carboxy methyl cellulosePectin

Emulsifiers:They are substances which help to form emulsions.Glycerol Mono Stearate (GMS).FlavoursColour Egg solids - Egg yolk solids improve the whipping ability.Fruits and nuts

Figuring the mix

Knowledge of calculation of ice cream mix is helpful in properly balancing the mix, in establishing and maintaining a uniform quality and in producing ice cream that conforms to legal standards. Ice cream mix - simple and complex. Simple mixes - require the least calculation and are made of ingredients, each of which supplies one constituent. Complex mixes - difficult to calculate as they include mixes where at least, one constituent is obtained from two or more products. Complex mixes require the use of the Pearsons square, algebraic methods.

Making the mixThe order in which ingredients are added is as follows:All liquid ingredients are placed in a jacketed vat provided with a power stirrer, and the agitation and heating started at once, the dry ingredients, including skim milk powder, sugar, and stabilizers are added while the liquid material is agitated before the temperature reaches 49C. Proper suspension to avoid lumpiness of the dry ingredients may be obtained by either mixing the dry materials thoroughly with part of the sugar before slowly adding it to the liquid, or by sifting / slowly adding these substances to the liquid.If gelatin is the stabilizer used, it is best added after it is thoroughly mixed with equal volume of sugar, and before the liquid material reaches 49C.

Alternatively, it can be sprinkled on the surface of the cold liquid and allowed to soak before the mixture is heated or soaked in water and the mixture heated to completely dissolve the gelatin, which is usually added to warm(38-49C) mix.If sodium alginate is used, it should not be added until the temperature of the liquid material has reached at least 66C. If butter, plastic cream, frozen cream, or other products are used, they should be cut into small pieces and added after time has been given to allow for complete melting before the pasteurizing temperature is reached. With a few exceptions, colouring and flavouring materials are added when the mix is frozen.

The ISI specification for pasteurization temperature time combination for ice cream mix are as follows:Batch system- 68.5 C for not less than 30min.HTST method - 80 C for not less than 25 sec.In batch system the heating and holding may be accomplished in the vat used for mixing the ingredients

Pasteurization of mix

Homogenization of mixThe main purpose of homogenization -make a permanent and uniform suspension of the fat by reducing the size of the fat globules to a very small diameter, preferably not more than 2 microns.The mix is usually homogenized at temperature from 63 to 77 C at pressure of 2500to 3000 psi with one valve, or 2,500 to 3000 psi at the first stage and 500 psi at the second stage will usually give good results for an average mix (with 3 - 12% fat).

Cooling and ageing of mixCooling the mix immediately after homogenization to 0-5C is essential, after which it should be held in ageing tanks until used. Ageing refers to holding the mix at a low temperature for a definite time before freezing. The ageing temperature should not exceed 5C. The ageing time under commercial conditions may range from 3 to 4 hours, except for sodium alginate which requires no ageing.

Advantages of agingImproves the body and texture of ice creamImproves the whipping capacityIncreases maximum overrunIncreases melting resistance.

Freezing the mixFreezing is one of the most important operations in the making of ice cream for upon it depends the quality, palatability and yield of the finished product.The freezing process may be divided into two parts. The mix with the proper amount of colour and flavouring materials generally added at the freezer, is quickly frozen while being agitated to incorporate air in such away as to produce and control the formation of small ice crystals which is necessary to give smoothness in body and texture, palatability and satisfactory overrun in the finished product.When ice cream is partially frozen to a certain consistency it is drawn from the freezer into packages and quickly transferred to cold storage rooms where the freezing and hardening is completed without agitation.

Overrun in ice creamOverrun is usually defined as the volume of ice creamobtainedin excess of the volume of the mix. It is usually expressed as a percentage. This increased volume is composed mainly of the air incorporated during the freezing process. The amount of air incorporated depends on the composition of the mix and the way it is processed; and is regulated so as to give that percentage overrun or yield which will give the proper body, texture and palatability necessary to a good quality product. Too much air will produce a snowy, fluffy, unpalatable ice cream while too little, a soggy, heavy product.

The desirable over run percentage in different ice creams is

Product% ORIce cream packaged70-80Ice cream bulk90-100Softy ice cream30-50

YOGHURT

May be defined as a coagulum obtained by lactic acid fermentation of prescribed milk or milk products by the action of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus.The addition of additives is optional.The two yoghurt bacteria are added as the starter culture at 2-5% inoculum, preferably at 1:1 ratio and incubated at 42-45C for 3-6 hours until pH 4.4 and titratable acidity 0.9-1.2% is achieved.Final product should contain large quantities of the above micro organisms.

CLASSIFICATION:Set type: incubated and chilled in the packet.Stirred type: incubated in tanks and chilled before packaging.Drinking type: similar to stirred type, but coagulum is broken down to a liquid before being packed.Frozen type: incubated in tanks and frozen like ice cream.Concentrated: incubated in tanks, concentrated and chilled before being packed. Also called as strained yoghurt/ labneh or labaneh.

CompositionFat (%)SNF(%)Yoghurt38.2Partly skimmed yoghurt0.5-38.2Skimmed yoghurt