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.