Whey Beverages and Drinks

The use of whey for the manufacture of whey-based beverage has been the most traditional approach to whey utilization for human nutrition. Whey based fruit beverages are manufactured by mixing of appropriate fruit pulp/ juice or juice concentrate and processed whey. The more sophisticated technological approaches include the painstaking selection of proper flavour or flavour blends, complex whey treatment operations and often the inclusion of additional nutrients to increase the consumer appeal. The pH adjustment in the heat processed long shelf life beverage is important in order to minimize heat induced whey protein precipitation.

A variety of whey beverages consisting of plain, carbonated, alcoholic, soy and fruit have been successfully developed and marketed all over the world, because they hold great potential for utilising whey solids. In India also, a number of refreshing whey drinks including the low cost ‘Whevit’ and ‘Acidowhey’ are in the market.

These drinks are preferably prepared from paneer/chhana whey, which is acidic and has low protein content. Whevit, an orange, pineapple, lime or mango flavoured alcoholic drink from whey, was developed at National Dairy Research Institute, Karnal. For its manufacture, fresh whey is efficiently separated in cream separator, deproteinised by steaming for half an hour and cooled to room temperature. To the deproteinised and clarified whey, 22-23% of 50% sugar solution is added followed by 2-2.1% of 10% citric
acid, colour and flavour. It is then fermented by incubation at 22 o C for 14-16 hr with a 1% culture of Saccharomyces cerevisae. The product is bottled, pasteurised (75 o C/30 min), cooled and stored at low temperature (5-10 o C). Final product contain
0.5 to 1% alcohol.

For the manufacture of Acidowhey that is a non-alcoholic whey drink, deproteinised whey is fermented with a culture of Lactobacillus acidophilus and Lactobacillus bulgaricus (1:1). Sugar and flavour are then added and the product is reheated at 75 o C for 5 min, cooled to 5 o C, packed in pouches and stored in refrigerated conditions.

The common operation for the manufacture of whey-based beverage is to blend the whey and fruit juice components, followed by proper heat processing and packaging.

The sedimentation problem can be encountered by centrifugal clarification to remove all sedimentable casein fine particles. The pH adjustment of the final product should be controlled accurately, especially if subsequent severe heat processing is to be used. To minimize heat induced whey protein precipitation, adjustment below pH 3.8-3.6 is necessary as the whey protein fraction becomes resistant to coagulation below this critical range.

Technological problems may be encountered also when the desired formulation contains additional components that interfere with processing or final product quality.

Flavour losses with some fruit juices may be encountered in UHT processing of the final product, especially in the direct type machines employing a flash cooling vacuum chamber.

Packaging of whey based soup and fruit beverages varies considerably. The tetra- pack paper based containers of 200 ml capacities predominate in India, while 250 or 500 ml plastic cups with aluminium foil are also being used, probably for the manufacturer’s convenience in western countries. Metal cans, glass or rigid plastic containers have very seldom been used for these products.

Ghee Residue

Ghee residue is a by-product of ghee manufacturing industry and is produced in large quantity (about 91000 tonnes per annum) in India. During the manufacture of ghee, the solids not fat (SNF) present in cream or butter appears in the form of small particles known as ghee-residue. It is obtained after molten ghee has been either strained out with bag filters or muslin cloth or separated by continuous centrifugal clarifiers. The yield of ghee-residue varies with the method of preparation of ghee.

This is due to the variation in the non-fatty serum constituents of the different raw materials used for the preparation of ghee. The average yield of ghee-residue is maximum in direct creamery (DC) method (12%) followed by about 3.7% yield in creamery butter (CB) and desi butter (DB) method. Keeping quality of all types of GR clarified at 120°C is 3 months. Its shelf life can further be increased to more than 4 months by pressing it in cake form.

Physical attributes: Ghee residue is moist brownish sediment. On average, particle diameter of ghee residue is about 115 ì and density is 1.14 g/cm3.

i. Chemical Composition

A look at the chemical composition and yield of GR obtained from various sources(Table) will give an idea of the huge quantity of nutrients in terms of fat, protein,lactose and minerals that go in ghee-residue. There are considerable variations in the chemical composition of ghee-residue depending upon the method of preparation of ghee. The approximate composition (%) of ghee-residue varies as fat (32-70), protein (12-39), moisture (8-30), lactose (2-14) and ash (1-8). Moisture, protein and ash contents are more in CB and DB ghee-residue than in DC ghee-residues.Fat content is higher in DC residues than in butter ghee-residue. Lactose content is the highest in DB followed by DC and CB ghee-residues. Thus ghee residue is a rich source of lipids, proteins and carbohydrates.

Chemical composition and yield of ghee-residue (Hand pressed)

Lipids in ghee-residue

i) Analytical constants: The lipids of ghee-residue have lower Reichert value and polenske value (24.4., 1.3) but higher iodine value (43.4) in comparison to those of corresponding ghee (30.1, 1.6, 33.9 respectively.

ii) Fatty acid composition: The lipids of ghee-residue have lesser lower chain fatty acids C4.0 to C12.0 (5.3%) and total saturated fatty acids (58.7%) and more of unsaturated fatty acids (41.3%) in comparison to those of ghee (10.1, 66.8, 33.2% respectively). The fatty acid composition of phospholipids shows that it has no fatty acids lower than 12 carbon atoms.

iii) Polyunsaturated fatty acids (PUFA): Irrespective of the method of preparation, PUFA content of ghee-residue lipids (4.4%) is higher than those of corresponding ghee (2.8%).

iv) Phospholipids: Ghee-residue is rich in phospholipids (1-9%). The phospholipid content of ghee-residue is dependent upon the method of preparation. It is highest in CB ghee-residue lipids (17.39%) followed by DB ghee residue lipids (4.95%) and the least in DC ghee residue lipids (1.57%). These levels are much higher than those in ghee (0.004 - 0.08%). Phospholipid acts synergistically with reducing substances in ghee residue and protects it from oxidative defect. Higher phospholipid (a good emulsifier) content of ghee residue is beneficial in developing certain products where emulsification of fat and aqueous phase is desired.

The phospholipid content of ghee residue decreases as the period of heating increases due to the transfer of phospholipids from ghee-residue to ghee. While heating cream butter, only a small fraction of the phospholipids get transferred to ghee, most of the phospholipids remain with the residue because of their polar character. The differences observed in the physico-chemical constant, fatty acids and PUFA contents between lipids of ghee-residue and ghee are due to the high phospholipid content of  ghee-residue.

Proteins in ghee-residue: Soluble nitrogen content of ghee-residue prepared from cream or creamery butter decreases with heating time. This decrease is due to the denaturation of the proteins. The total reducing capacity expressed as mg of cysteine hydrochloride/g of CB-ghee-residue (26.0) and free sulphydryl content (μm/g) of ghee-residue (2.90) are much higher than those in ghee (0.075 and 0.02, respectively).These substances are liberated from protein during heat treatment and because of their polar nature are mostly retained in the ghee-residue. Whey proteins, especially ß-lactoglobulin are the main source for these sulphydryl compounds

Milk sugars in ghee-residue: Main sugars in ghee-residue prepared at 120oC are lactose, galactose and glucose. As the period of heating is increased, the lactose content of ghee-residue decreases with a corresponding increase in galactose and glucose content.

ii. Nutritional Properties

Ghee residue is a rich source of protein and fat apart from containing considerable amounts of minerals and can be used as human dietary supplement. However the nutritional value of ghee-residue protein is low due to the damage of some essential amino acids during preparation of ghee at high temperature. The lack of lysine in ghee-residue is the most dominant factor in depressing the PER of ghee-residue.The supplementation of ghee-residue with a combination of lysine (8%), methionine (2.5%) and tryptophane (1.4%) increases its nutritional value even slightly higher than that of SMP. It has been observed that skim milk powder (SMP), SMP: gheeresidue (2:1), SMP: ghee-residue (1:2) and ghee-residue diets have protein efficiency ration (PER) of 3.44, 3.07, 2.46 and 0.66, respectively.

Antioxidant Properties: Ghee-residue is a rich source of natural antioxidants and its antioxidant properties are due to its constituents affected by various technological parameters. The overall antioxidant properties are due to both lipid and non-lipid constituents. Ghee residue can be used as a source of natural antioxidants for improving the shelf life of food products including dairy products where use of synthetic antioxidants is generally not preferred because of their toxic effects.

i) Contribution of lipid constituents: Phospholipids show the maximum antioxidant activity followed by á-tocopherol and vitamin A. Among the various phospholipid fractions, cephalin shows the greatest antioxidant activity. The oxidative stability of ghee can be increased by increasing its phospholipid content to 0.1% either through heat treatment or through solvent extraction process. It has been observed that heating ghee-residue with ghee in the ratio of 1:4 at 130°C have maximum transfer of phospholipids from ghee-residue to ghee.These antioxidant concentrates can be added to ghee to give about 0.1% phospholipids so as to increase the keeping quality of ghee.

ii) Contribution of non-lipid constituents: Among the non-lipid constituents, the amino acid proline, lysine, cysteine hydrochloride and tryplophane show the antioxidant properties. The contribution of proline as antioxidant is maximum, though less than BHA at 0.02% level. Further, the addition of lactose, glucose, galactose and their interaction products with protein and phospholipids to ghee also increase the oxidative stability of ghee. As ghee-residues contain large amount of reducing substances including free sulphydryls, such compounds may also contribute to the antioxidant properties of ghee-residue.

iii) Antioxidant Properties as Affected by the Temperature of Clarification:

The antioxidant efficiency of ghee-residue decreases with increase in the temperature of clearification of ghee. The addition of ghee-residue obtained from ghee prepared at lower temperature (110°C) results in lesser development of peroxides than the addition of ghee-residue prepared at higher temperature (150°C).

iv) Antioxidant Properties as Affected by the Method of Preparation: CB ghee-residue has the maximum antioxidant properties followed by DB and DC ghee residues.

Flavouring Properties: Ghee residue is also a rich and natural source of flavor compounds viz. FFA, carbonyls and lactones. The level of FFA, carbonyls and lactones in ghee-residue are respectively 11, 10 and 132 times than in ghee. Ghee flavour can be induced in vanaspati and butter oil etc. by adding 10% ghee-residue and clarification at 120°C/flash (10%). This treatment also enhances their keeping quality because of the antioxidant property of ghee residue.

 

Chemical composition and yield of ghee-residue (Hand pressed)

 iii. Utilization of Ghee-Residue

Ghee residue, by virtue of its chemical composition, nutritional quality, physical characteristics, bulk of production and long shelf life permitting its collection and centralized handling has great potential and is more amenable to exploit its utilization.Ghee residue can be utilised in a number of products like chocolate burfi, samosa filling, chapatis etc. However, most dairy plants in India have not been utilising ghee residue profitably except for fat extraction. Commercial utilisation of whole ghee residue is yet to pick up. Most of the ghee residue goes to waste. A sincere R & D work and a strong willingness on the part of manufacturer is required to develop food uses of ghee residue and put it in the market

Recovery of Ghee

In dairy plants, attempt has been made to recover as much ghee as possible from ghee residue. Two methods of recovery of ghee from ghee-residue have been developed.

i) Pressure technique: This consists of subjecting the heated ghee-residue (65- 70°C) to a limited pressure in hand screw or hydraulic press. This method gives a yield of about 45% (extraction efficiency of about 67%). This method has been recommended for adoption as it is simple, efficient, more practical, economical and requires no electricity or sophisticated equipment.

ii) Centrifugal process: This consists of heating ghee residue in water (65°C) so as to transfer the occluded ghee of the residue to water. Ghee is subsequently recovered by centrifuging the water-fat phase. The method yields 25% ghee (46% efficiency).

Processing of Ghee Residue

Ghee residue has soft and smooth texture but gets progressively hardened during storage. The change in the textural characteristics is much faster particularly during the first 15 days and by the end of a month its grain becomes very hard and gritty. In order to eliminate the undesirable characteristics, it is necessary to process it so as to yield a soft and smooth texture essential for edible preparations. Before subjecting the residue to any-treatment, its lumps are broken and then pulverized by passing through 40-mesh sieve. A number of treatments of ghee residue (Table ) have been suggested. All the treatments make the processed residue soft and smooth.The trend of changes brought about in the constituents of residue remains same. Residues absorb considerable amount of moisture and its acidity reduces. In case of treatments II, IV and VI acidity reduces to nil. Fat and lactose contents of the residue also reduce considerably. Washing of residue with 50% alcohol followed by cooking in soda, i.e., treatment IV is best so far as removal of excess fat from the residue is concerned. Autoclaving of this residue after incorporating 2% vinegar lowers the moisture content and improves the texture of the product.

Preparation of confections

The physico-chemical properties of processed ghee-residue are very suitable for preparation of confections. It contains the major constituents in suitable proportion and possesses fine texture that imparts requisite body to such products. Further the treatment during processing of these confections involves heating to such an extent that it completely arrests enzyme activity and flavour deterioration in the final product.The higher fat content in the residue quite often obviates the need for addition of oils and fats in its preparation

i) Preparation of candy: The recipe for candy preparation consists of 1 kg processed ghee-residue, 500 to 625 g sugar and 125 to 250 g dry coconut powder. 50% sugar syrup is prepared and processed ghee residue is thoroughly mixed in it with the help of suitable ladle. The mixture is heated on low fire with continuous stirring to evaporate moisture. When the mass becomes sufficiently sticky, coconut powder is added. The candy is evenly spread on a plate and cooled (5-10°C) for about an hour and cut into small cubes and wrapped in parchment paper.

ii) Preparation of chocolate: The recipe for preparation of chocolate consists of 1 kg processed ghee residue, 500 to 625 g sugar, 60 to 90 g cocoa powder and 250 g skim milk powder. 50% sugar syrup is prepared and processed ghee residue is thoroughly mixed in it with the help of suitable ladle. The contents are desiccated on a low flame till dough is formed. At this stage cocoa and skim milk powder are added and stirred vigorously till pat is formed. Finished product is spread on a plate and cooled overnight in refrigerator and cut into slabs or cubes and wrapped in parchment paper. The product has a shelf life of more than 3 months.

 

                                                        Comparision of chemical composition of ghee-residue

subjected to various processing treatments.

 Treatment I : Loosely tieing the residue in the form of bundle and cooking in boiling water for 30 min.

Treatment II : Cooking the residue in boiling 1.0% sodium bicarbonate for 30 min.

Treatment III : Washing the residue with 50% alcohol and then cooking in boiling water for 30 min.

Treatment IV : Washing the residue with 50% alcohol followed by boiling in 1% sodium bicarbonate.

Treatment V : Autoclaving the residue (15 PSI/10 min) obtained from III after incorporating 2% vinegar

Treatment VI : Autoclaving the residue obtained from IV after incorporating 2% vinegar.

Preparation of edible pastes: For preparation of edible paste for sandwich, processed ghee-residue is first mixed with 2.5-3% salt and then 0.1-0.5% marmite (a yeast product). The whole mass is heated on a low fire for about 5 min till a paste is formed. An edible paste for ‘dosa’ and ‘samosa’ can be prepared if 2-4% chatni powder is used instead of marmite. Both these preparations, if properly packaged, can remain marketable for 2 months.

Preparation of burfi-type sweet: Processed ghee residue is mixed with khoa in the proportion of 1:1, on total solids basis. Sugar is added @75% of the total solids (khoa + ghee residue). The whole mass is heated and worked rigorously for 10-15 minutes so as to dissolve the added sugar completely. At this stage about one-third of the sweetened mass is separated and 8% chocolate powder, on total solids basis, is added to processed ghee residue and khoa and thoroughly mixed. This portion containing the dissolved chocolate is applied as a thin layer over the remaining twothird of the mixture, which has already been spread-out as a thick layer on a wellgreased tray. The mass is cooled and when set, cut into pieces of uniform size and shape.

Preparation of bakery products: Nankatai type cookies and sponge cake can be prepared from processed ghee-residue obtained from ripened cream. 30 and 20% part of vanaspati fat used in preparation of cookies and sponge cake, respectively is replaced by ghee-residue fat. Use of ghee-residue enriches both the bakery products in protein content.

Buttermilk

Buttermilk is an important by-product obtained during manufacture of butter. Normally three types of buttermilk are produced in our country, viz. (i) sweet cream buttermilk obtained by churning of fresh/ pasteurized cream with little or no developed acidity,(ii) sour buttermilk obtained by churning cultured cream, and (iii) desi buttermilk (lassi) obtained by churning of curd (dahi) during the manufacture of makkhan.The sweet and sour buttermilks are produced in the organized sector and lassi at the household levels in small quantities. The exact amount of buttermilk production in India is not estimated. However, based on conversion of 6.5% of total milk production into creamery butter, it can be estimated that about 400 million kg of buttermilk is produced in organized sector annually as a by-product. In addition, a substantial amount of lassi (sour buttermilk) is also produced during the manufacture of makkhan directly from fermented milk (curd). Total annual production of buttermilk in India is estimated at 35000 million kg.

i. Chemical Composition

The chemical composition of buttermilk varies to a great extent, depending on the amount of water added to cream. Some of the butter manufacturers standardize cream with water, thereby decreasing the total solids level of buttermilk. The gross chemical composition of buttermilk produced under ideal conditions is almost similar to that of skim milk Table

Average gross composition and physico-chemical properties of

sweet cream buttermilk and skim milk (obtained from buffalo milk)

Sour buttermilk differs from sweet cream buttermilk in respect of titratable acidity.The acidity in sweet cream buttermilk varies from 0.10 to 0.14 per cent, whereas in sour buttermilk it is even as high as 1%. However, there is not much difference in the chemical composition of two types of buttermilk. Desi buttermilk has wide range of composition depending on the quality of milk used for making curd and levels of addition of water during churning. Desi buttermilk, on an average, contains 4% total solids comprising of 0.8% fat, 1.29% protein and 1.2% lactic acidity. The colour of desi buttermilk is brownish due to prolonged heating of milk before culturing and the body not as homogeneous as that of factory produced buttermilk. When kept undisturbed for sometime, curdy material deposits at the bottom of desi buttermilk.

ii. Processing and Drying of Sweet Cream Buttermilk

Being almost similar in gross chemical composition of skim milk, no problem is encountered during its processing, i.e., separation, clarification, pasteurization, concentration and drying. Rather the heat stability of sweet cream buttermilk is considered to be better than skim milk thereby making it more suitable for processing to very high heat treatments. Concentration and spray drying of sweet cream buttermilk can also be achieved adopting the same standard conditions used for skim milk. The physico-chemical properties of spray dried sweet cream buttermilk and skim milk are given in Table

Physico-chemical characteristics of spray powders

The striking differences between two types of powders are the high total lipids including phospholipids and low bulk density in sweet cream buttermilk powder in comparison with skim milk. The spray dried buttermilk powder is less free flowing and dusty because of high fat content in comparison with skim milk powder. Though the high fat content reduces the shelf life of the powder during storage, the high phospholipids will provide better oxidative stability to dried buttermilk..

iii. Utilisation of Sweet Cream Buttermilk

Sweet cream buttermilk, because of its resemblance in gross chemical composition with skim milk, is usually admixed with bulk of skim milk for further spray drying or even product manufacture in dairy plants. Sweet cream buttermilk can be used in beverage form and in the fluid milk industry as a milk extender with specific benefits over skim milk. The other potential uses of buttermilk solids are in manufacture of soft varieties of cheese, paneer, fermented milks and traditional milk products.

However, various physico-chemical properties of buttermilk differ from that of skim milk (Table). Sweet cream buttermilk has lower acidity and curd tension but higher viscosity as compared with skim milk. These differences in physico-chemical properties of buttermilk and skim milk provide many choices for their selective applications in dairy products manufacture. Buttermilk contains higher fat content than skim milk, which can be reduced to some extent by subjecting it to centrifugal separation. Buttermilk contains a larger proportion of protein mixture sloughed from the fat globule-milk-serum interface by churning process. The amount of fat globule membrane protein (FGMP) is, however, not as large in comparison with total buttermilk proteins. The FGMP are hydrophilic and hydrophobic in nature and their physical properties, nitrogen content and amino acid composition do not correspond with any other milk proteins. The FGMP also contributes a complex mixture of glycerophospholipids to buttermilk. Sweet cream buttermilk contains about nine times higher phospholipids than skim milk (Table ). It has been noticed that phospholipids in buttermilk do not have short chain fatty acids. The principal fatty acids are C16 (palmitic) and higher acids. Of the total phospholipid fatty acids,about 40% by wt. are saturated acids and the rest are non-conjugated di- to pentaunsaturated acids. Phospholipids of buttermilk include more or less equal proportions of lecithin, sphingomyelin and cephalin together with a small proportion of cerebrosides.

i) Beverage: As beverage, buttermilk is consumed in plain and spiced forms throughout the year and highly used as a refreshing drink in summer season. A number of state federations and private plants sell plain buttermilk in 500 ml and 1 kg pack and salted and spiced buttermilk in 200 ml pouches. “Sumul chhach” is packed in 500 ml packs.

ii) Market milk: The undiluted sweet cream buttermilk produced in the organized dairies is partly admixed with the whole milk for fluid milk supply. It has been observed that use of sweet cream buttermilk in the market milk for toning of buffalo milk improves the palatability, viscosity and heat-stability and reduce the curd tension without adversely affecting the keeping quality. In addition to plain fluid milk, it can also be used for the preparation of flavoured milks and milk beverages. The powder made from the mixture of skim milk and sweet cream buttermilk is treated as a skim milk powder and used for reconstitution purposes.

iii) Fermented milk product: Curd prepared by incorporating sweet cream buttermilk into whole milk has soft-body which is probably due to the change in the electric charge on the casein during churning, the presence of phospholipids and other FGM materials, and the free fat in the buttermilk. Addition of 1-2% skim milk powder is recommended for improving the body of dahi made from buttermilk. As an alternative to curd making, sweet cream buttermilk can be successfully utilized in the manufacture of cultured buttermilk and lassi in which the firmness is not of much consideration.

iv) Paneer: Buffalo milk has to be standardized to a fat and SNF ratio of about 1:1.65 to meet the PFA requirements for the manufacture of paneer. The replacement of skim milk with sweet cream buttermilk for the standardization of buffalo milk has been found to increase the yield of paneer by about one per cent without altering the organoleptic and textural properties. It is also possible to prepare good quality paneer from low fat milk by incorporating buttermilk solids to buffalo milk.

v) Cheese: The preparation of hard varieties of cheese like Cheddar and Gouda involves the adjustment of casein and fat ratio with the help of skim milk. The replacement of skim milk with sweet cream buttermilk results into softer body due to the presence of higher amount of fat globule membrane materials in buttermilk. Several benefits of utilizing buttermilk solids in the manufacture of soft varieties of cheeses are: decreased waste disposal problems at the creamery, reduction in cost, increased cheese yield and improved flavour, texture, biological value and hypocholesterolaemic effects of cheese.

vi) Other uses: Sweet cream buttermilk can also be used for manufacture of some popular indigenous dairy products, e.g., khoa, kheer and rubri. The dried buttermilk can replace the skim milk powder in the manufacture of gulabjamun mix powder. Because of high lecithin content in buttermilk, it may improve the textural properties of rasogolla. The buttermilk powder can also be used in the preparation of ice cream and bakery products.

vii) Utilization of desi and sour cream buttermilk: Desi buttermilk (lassi) is an important domestic beverage in India. It has high nutritive and therapeutic value.In addition to normal milk constituents, lassi is also a rich source of vitamins. It is considered to be an excellent thirst quenching and nourishing beverage, particularly during summer months. It is also used for making some popular traditional preparation, e.g. karhi, raita etc. The industrial utilization of lassi cannot be exploited due to lack of proper collection system and day-to-day variations in the composition and quality. Sour cream buttermilk has similar utilization as desi buttermilk.

Buttermilk and Ghee Residue

Buttermik and ghee residue are important nutritional byproducts of butter and ghee making industry, respectively. These byproducts differ widely in their relative chemical constituents depending on the manufacturing process of butter and ghee. Proper utilization of these byproducts for human consumption would, not only ensure the availability of more nutrition for humans, but also give better economic return and

help in reducing waste disposal in dairy plants.

Lactose

Lactose is carbohydrate of milk and is the only sugar of animal origin. Lactose in its pure form is a white, water-soluble crystalline powder of moderately sweet taste with no odour. Lactose is extensively used in food and pharmaceutical industries due to its nutritional importance and multiple functional properties. Low sweetness,consistency improvement in confectionery and bakery products, as carrier and anticaking agent in powder foods, filler for tablets and capsules, controlled browning in bakery products, flavour enhancer in sauces and dressings, nutritional importance in infant formulas, an additive in culture media etc. are some of the desirable functional properties and applications of crystalline lactose powder. Lactose is also important fermentation substrate for the production of a variety of fermented products. As a rough estimate, the quantity of lactose produced on a world-wide scale amounts to some 50 lakh MT per annum.

Lactose is produced commercially from whole whey or from UF permeate. The protein and mineral contents of the whey are the limiting factors for the crystallization of lactose, and this is the reason why UF permeate of whey is preferred as the starting material in the production of lactose. However, A significant quantity of food and pharmaceutical grade lactose is produced by conventional process. During the process, a protein-mineral precipitate is segregated, which is dried and sold as a by-product for animal feed.

i. Manufacture of crude lactose

Lactose can be manufactured either from sweet whey having a minimum pH of 5.6,usual range being 5.9 to 6.3 or from acid whey with a maximum pH of 5.1 (usual range, 4.4 to 4.6). In Indian context, chhana and paneer whey, whose pH ranges from 5.1 to 5.6, can also be used as a good raw material for lactose manufacture.Generally, sweet whey is preferred because of its high lactose and low ash content.Acid whey can be neutralized, but this will change the whey characteristics and the cost of manufacture will also increase.

i) Clarification and separation of whey: Clarification and separation is necessary to remove the fat, suspended curd particles and other impurities(dust, dirt, microbes) from whey.

ii) Deproteinisation and demineralization of whey: Whey contains about 20% of the total proteins of milk. The presence of protein and salts in whey increases the viscosity of concentrated whey and hinders the crystallization of lactose. The reduction of protein and mineral contents in whey causes reduction in viscosity and thereby permits concentration to higher total solids. Degree to which the proteins and salts are removed from whey prior to concentration and crystallisation, determines the yield and purity of lactose.Cheese whey on heat treatment to 85-87°C at pH 4.8 yields maximum whey solids on filtration, while in case of paneer whey, higher yield could only be obtained by heating to 90 to 92°C for 10 minutes at pH 6.6. Up to 85 % removal of proteins can be achieved by adding 1 % CaCl2 (20% soln.) to whey at 90 to 95°C. Addition of CaO at 93°C and holding for 30 minutes is also practiced where more than 90 % of proteins and minerals are removed.

iii) Concentration: The concentration of whey to 45 - 60 % total solids is very critical, because a high total solids concentrate will be too viscous to pump, while a lower total solid concentrate will result in lesser degree of supersaturation of lactose and so insufficient lactose crystallisation. This is performed either by a pre-concentration through reverse osmosis, followed by evaporation in multi effect evaporators or merely by evaporation. Reverse osmosis has the potential for removing a major portion of the water from whey or permeate more economically than the evaporator process. The concentration process must be conducted in such a way that no lactose crystallisation takes place in evaporator and piping.

iv) Crystallisation: Crystallisation is initiated in the hot concentrated whey. This is a complex process during which lactose molecules diffuse to the crystal surface and simultaneously release and transfer the heat of crystallisation from the crystal to the liquid. The purpose of crystallisation is to secure the formation of crystals that can be separated from the mother liquor. For easy recovery of lactose crystals, their size must be sufficiently large to ensure quick settling of crystals.Easy recovery is obtained with an average size of 0.2 mm. The number of crystals and their average size can be controlled by seeding the concentrate with a known number of very fine lactose crystals. The seed crystals are added in the form of fine particles of á-lactose monohydrate at the rate of 1 Kg per ton of concentrate. In concentrated lactose solution, the crystallisation rate depends on available crystal surface for growth, purity of the solution, degree

of supersaturation, temperature, viscosity and agitation.

Cooling of lactose syrup to a temperature below saturation temperature is necessary for crystallisation of lactose. Higher temperature of crystallization increases the growth rate of the crystals. Therefore, slow cooling of the concentrate is employed. Slow cooling to 10°C in minimum 20 h (up to 40 h) and further holding for 15 h with intensive stirring has been suggested. During crystallization, ß-lactose is converted into -lactose, which is crystallised out.Automatic systems in lactose crystallisation tanks are available to regulate temperature within 0.5oC.

v) Harvesting of lactose crystals: The lactose crystals can be harvested batchwise in basket centrifuges, which have the advantage of permitting complicated wash cycles. Wash water is introduced into the centrifuge during the separation of lactose crystals to assist in the removal of the remaining impurities. The use of 10 % wash water can reduce the ash level of the lactose

by more than 66 %. However, on a commercial scale, continuous decanters with a screw conveyor for crystal discharge are more commonly used. The crystals from first decanter are fed into a second decanter in order to improve washing and removal of mother liquour. The washed crystals recovered in decanter have moisture content of approximately 10% and can be dried directly.

A specially designed centrifuge gives a high degree of separation of lactose crystals from condensed cheese whey. Crystals of 40 μm can be recovered with final moisture content of 1.5-2.5%. Another designed centrifuge proved capable of continuously separating crystalline lactose with 2.5-2.9% moisture from concentrated whey at the rate of 250-300 kg/hr.

vi) Yield and purity: Lactose yields varying from 65 to 76 % have been reported by different workers. Lactose % in crude lactose obtained by different workers varies between 91 and 97 %.

vii) Drying: The most common crystalline form of lactose i.e. á-lactose crystallizes below 93.5°C and the other form, the ß-lactose, crystallises above 93.5°C. The drying process, therefore, should be limited to a product temperature of 93°C to prevent crystallisation into ß-lactose anhydride. Flash drying can result in the formation of a thin layer of amorphous lactose on alpha hydrate crystals leading to lump formation in the bagged lactose. A fluidized bed drier with a maximum product temperature of 92oC/15-20 min gives good results.Pneumatic transport of lactose from the drier must be carried out by means of dry air at about 30oC. It gives gentle product cooling.

ii. Refining of lactose

For high degree of purity, as in pharmaceutical grades, refining of lactose is done by subjecting crude lactose to treatment for removing colour, residual protein and salts followed by recrystallisation. Crude lactose is dissolved in hot water to a 50-60% concentration depending on its purity. About 1% of decolorizing paste consisting of 3 parts bone black, 1 part activated carbon and 1 part 36% hydrochloric acid is added. Quick dissolution requires heating to 105ºC. Carbon absorb colour and probably removes other impurities to some degree. Hydrochloric acid is added to assist the action of carbon, to solublize salts and to aid in removal of protein. Lime is used to adjust the reaction to that most favourable for the

 

Lactose Commercial - Specifications (IS 1000:1989)

precipitation of protein, and probably aids by combining with the protein to some extent. The liquid is boiled and filtered with the assistance of filter aid to remove carbon and precipitating impurities at high temperature to avoid premature crystallisation. The carbon and the precipitated impurities are removed by filtration.The resultant clear solution is further evaporated to 70% TS and introduced into crystallising tanks. The crystallized lactose is harvested and dried. Edible lactose is normally dried to 0.5% moisture content and pharmaceutical lactose to 0.1% moisture content. The lactose is finally ground to 80-200-mesh size before bagging.

iii. Grades of Lactose

The international trade recognises following commercial forms of lactose.

Whey Protein Concentrates

There has been a continuous increase in the production of whey protein concentrates (WPC) since the introduction of the latest ultrafiltration process about three decades ago. It is now a major means of WPC production throughout most of the dairy countries of the world. Increased production of WPC warrants its greater application in food products. Though soluble WPC have been found to be technically suited to a wide range of products, its use is not cost effective in all cases. Presently, WPC constitutes a very small proportion (10%) of protein utilisation in food industry. The largest potential use of WPC is as a replacement for non-fat dry milk (NFDM) in the food industry. WPC with 35% protein is perceived to be a universal substitute for NFDM, because of the similarity in gross composition and its dairy character.Superiority of WPC over NFDM is also due to cost advantage.Due to various reasons, buffalo and cow milks are being humanised and used partly or exclusively for feeding human infants throughout the world. For humanisation,apart from making other modifications, whey proteins proportion needs to be increased in these milks. For this, a great potential lies in the application of WPC.WPC can also be seen competing as protein and functional ingredient with casein,egg albumin and soya proteins for use in food products. The PER value of whey proteins (3.2) is very high compared to standard casein (2.5).

i. Manufacture of Whey Protein Concentrates

Procedures for the manufacture of whey protein products are based on known behaviour of whey components under defined conditions. Properties that have been exploited commercially include: molecular size differences (Ultrafiltration, gel filtration), insolubility of protein at high temperature, charge characteristics (demineralization, protein removal by ion exchange), aggregation by polyphosphates, and crystallization of lactose.

i) Ultrfiltration Process: By 1981, Ultrafiltration (UF) had become the most widely used process for recovery of soluble whey protein concentrate (WPC).The development of robust, synthetic and cleanable membranes and the refinement of continuous operation using multi-stage, recycle loops, and diafiltration have been significant factors contributing to the success of this process.With this process, a highly functional WPC is produced for a wide variety of applications.

ii) Gel Filtration Process: This process has been used commercially for recovery of WPC. The hydrated gel acts as a molecular sieve in that small molecular weight components are able to enter the solvent phase within the gel beads.Protein molecules remain in the solvent phase surrounding the beads. High and low molecular weight fractions then can be recovered. Products of 30 to 80% protein can be manufactured. The process is expensive to install and operate,and the yield, at 65% of the proteins in whey, is low. It also is subject to fouling and microbial contamination. It is no longer used in commercial operation.

iii) Heat precipitation process: Whey proteins may be precipitated with heating of whey at acid or near-neutral pH. Acid whey must be heated to at least 90oC and maintained at such temperatures for at least 10 min to achieve maximum yields. For sweet whey’s, good yields can be obtained by heating at pH between 6.0 and 6.5, although products so derived have higher mineral concentrations than those of acid whey unless pH is adjusted to 4.6 prior to protein removal.

The precipitate so formed is firmer and more readily separated than that formed in non-acidified whey. precipitated protein is removed by settling (static or accelerated), washed, re-separated, and dried. In modern plants, high-speed centrifuges such as clarifiers and decanters are used for separation. The product is dried using ring, fluid bed, roller or spray driers. Typical yield of whey proteins by this process is 4.2 to 5.2 kg/m3.

 

                            Protein yieldsa and concentrations of principal classes of dried

whey protein products

a Expressed as precentage of (total-nonprotein N) X 6.38 in original whey.

b Ultrafiltration, UF; gel filtration, GF

c Regenerated cellulose, cell; silica, sil. Pilot-scale data only.

d Lactose, Lac; Minerals, Min.

e Whey protein concentrate, WPC; delactosed whey, DLW; demineralized whey,

DMW; delactosed, demineralized whey, DLDMW.

 Percentage composition of whey protein concentrates

 Process refinements include demineralization prior to heating, pre-concentration by reverse osmosis and Ultrafiltration, and continuous, high temperature reaction (120°C for 8 min at pH 6). Most processes result in an insoluble product, but through heating whey to 95oC at pH 2.5 to 3.5, then adjusting to pH 4.5 prior to separation,it has been claimed that a product soluble at pH 5 can be produced.

iv) Precipitation by complexing agents: This process is also called the cold precipitation process. Numerous complexing agents can be used to recover protein from whey; of these, polyphosphates appear to be the only group to be used commercially for this purpose. Long-chain polyphosphates precipitate protein from whey at low pH e.g., 3.5. Typically, potassium polymetaphosphate and sodium hexametaphosphate are used. The precipitates so formed are removed by centrifugation, washed, and then subjected to pH alteration and calcium addition to remove the phosphate. Removal of calcium prior to phosphate addition reduces the amount of phosphate required and results in recovery of up to 90% of the original whey proteins. Further modification of this process is also possible.

Whey Beverages and Drinks

The use of whey for the manufacture of whey-based beverage has been the most traditional approach to whey utilization for human nutrition. Whey based fruit beverages are manufactured by mixing of appropriate fruit pulp/ juice or juice concentrate and processed whey. The more sophisticated technological approaches include the painstaking selection of proper flavour or flavour blends, complex whey treatment operations and often the inclusion of additional nutrients to increase the consumer appeal. The pH adjustment in the heat processed long shelf life beverage is important in order to minimize heat induced whey protein precipitation.

A variety of whey beverages consisting of plain, carbonated, alcoholic, soy and fruit have been successfully developed and marketed all over the world, because they hold great potential for utilising whey solids. In India also, a number of refreshing whey drinks including the low cost ‘Whevit’ and ‘Acidowhey’ are in the market.These drinks are preferably prepared from paneer/chhana whey, which is acidic and has low protein content.Whevit, an orange, pineapple, lime or mango flavoured alcoholic drink from whey,was developed at National Dairy Research Institute, Karnal. For its manufacture,fresh whey is efficiently separated in cream separator, deproteinised by steaming for half an hour and cooled to room temperature. To the deproteinised and clarified whey, 22-23% of 50% sugar solution is added followed by 2-2.1% of 10% citric acid, colour and flavour. It is then fermented by incubation at 22oC for 14-16 hr with a 1% culture of Saccharomyces cerevisae. The product is bottled, pasteurized (75oC/30 min), cooled and stored at low temperature (5-10oC). Final product contain 0.5 to 1% alcohol.

For the manufacture of Acidowhey that is a non-alcoholic whey drink, deproteinised whey is fermented with a culture of Lactobacillus acidophilus and Lactobacillus bulgaricus (1:1). Sugar and flavour are then added and the product is reheated at 75oC for 5 min, cooled to 5oC, packed in pouches and stored in refrigerated conditions.

The common operation for the manufacture of whey-based beverage is to blend the whey and fruit juice components, followed by proper heat processing and packaging.The sedimentation problem can be encountered by centrifugal clarification to remove all sedimentable casein fine particles. The pH adjustment of the final product should be controlled accurately, especially if subsequent severe heat processing is to be used. To minimize heat induced whey protein precipitation, adjustment below pH 3.8-3.6 is necessary as the whey protein fraction becomes resistant to coagulation below this critical range.

Technological problems may be encountered also when the desired formulation contains additional components that interfere with processing or final product quality. Flavour losses with some fruit juices may be encountered in UHT processing of the final product, especially in the direct type machines employing a flash cooling vacuum chamber.

Packaging of whey based soup and fruit beverages varies considerably. The tetrapack paper based containers of 200 ml capacities predominate in India, while 250 or 500 ml plastic cups with aluminium foil are also being used, probably for the manufacturer’s convenience in western countries. Metal cans, glass or rigid plastic containers have very seldom been used for these products.