MILK AND ,MILK F'RBDIICTS

A-jantha Horadagoda

Introduction

Ruminants- as a group, are able to produce inilk from poor quality feed such as roughages, agro-industrial by-products and also utilise non-protein nitrogen sources. This feature has beer? exploited by man from ancient tirnes to domesticate ruminants and use their milk to supplement nutritional requirements. In most countries. cow mi!k is an essential component of the human diet \vllile in certaii~ countries, where water i s scarce, goat and sheep milk is produced for human consumption.

The current world milk production is around 400 million metric tons of which 85 per cent is produced in the developed countries 1151. Most of this niilk constitutes co~v milk, while a large proportion of' &lie balance 15 per cent that is prcduced in the developing world consists o f but'falo milk. I n t11i: Indian subcontinent, it is estimated that 80 per cent of rile inilk produced is horn the buffalo 1161. In Sri Lanka, buffalo milk constitutes 25 per cent of the total milk produced (Table 1).

Tablc I. Average rnonthly milk production (liires) in Sri Lanka.

- Year Cou m11k Ruffalo m ~ l k

1993 17 082.700 6.330.100

1995 2 1,120.600 6,654,900

Adapted frorn: Department of ('ensus and Stat~\ t~cs, 1995

Structure and funccticm of the udder

I he anatomy of the udder (mammary gland) of the buffalo is essentially ~imilar to that of the cow, except for a few differences in the structure of the teats. Ir! the buffalo, the teats arc large and cjlindrical. This character istic shape of the teat had poszd a difficulty in directly using rnacl~ine milking equipment designed for the cow.

Department of i)?[ei-incity Preci~~zical Studi~s, Faculty of I'eteri~mty :Medicine und 4tzimn6 Scieizce. (inivrrrity c!i'Perraderzi.yu. Perau2eni,vcl

tiowever, recent studies conducted in lrtdia have helped to redesign .the teat cup to suit the buffalo. Since the latter development, machine milking has gained popularity, particularly in the large buffalo -farms of India. Another structural difference in the buffalo is in the sphincter at the teat orifice (Fig. 1 ), which is firmer than in cattle. 'The tightness of the sphincter is the reason for the extra pliysical effort required while milking buffaloes. This anatornical feature is believed to reduce the invasion of organisms into the manjmary gland thereby reducing the incidence of udder infections (mastitis) in the bui'falo.

In most countries, buffaloes are milked by hand. Traditionally, the calf is introduced prior to milking in order to stimulate milk let-dohn. Although it is widely conceived that the calf is essential to initiate milk let-down, washing of the udder, the tactile effect of hands on teats, the presence of the milker and the utensils can trigger the milk let down as i n tlze case of the dairy cow. The only difference is that it takes longer in the buffaloes when compared to cattle. This may be because of the delayed release of oxytocin which is essential to activate milk let-down.

1. Structure of tlie buffalo teat

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I'he milk yield qf the buffalo varies depending on several Sactors si~ch as the breed, lactation number, diet, management and environmental factors. River type breeds like Murrah, Surti, Jaffrabadi and Nili Ravi found in the Indo-Pakistan sub-continent produce more milk as they have bcen selected specially for their dairy traits On the other hand, swamp type buffaloes found in East and Far East As~an countries are poor milk producers.

Table 2. The average milk yield of some river and swamp type buffaloes and their crosses.

Brced Average milk yield (kg per

lactation) Surti (Indian) 1600 - 1800

Nili Ravi (Pakistanj 1800 - 2000

Murrah (Indian) 2000 - 2 100

L,anka buffalo 350 - 390

L,anka buffilo x Murrah (Indian) F I 910- 950 35 Lartka buffalo x % Murrah (Indian) 1270 - 1290

Sourccs: Ganguli. (1997)

Cross-breeding programmes have been undertaken with the objective of increasing the milk production of swamp type animals. Table 2. shnfis production statistics of some river and swarnp lype buffaloes and tlicir crosses with the Lanha buffalo. Milk yield is also known to vary with the stage of lactation. In the 1,anka buffalo, the milk j ~ e l d during early lactation is between 3 -5 litrestday while on an average the mid-lactation milk yield is around 1.5 - 2 litreslday 11 71.

Composition o f buffalo milk

The compoc;ition of milk varies between species and to a great extent it is dependant on the growth rate of the offspring. The higher the growth rate the more concentrated is the milk. Nevertheless, thc growth rate of cattle is greater than that of the buffaio, although buffalo milk is more concentrated than cow milk. Table 3 illustrates the composition of buffalo milk in comparison lo human, cow and goat milk. In relation to other domesticated ruminants, buffalo milk is rich in fat, proteins, calcium and vitamins.

~Vilk,firt: Milk Sat contains fatty acids which may be saturated or. unsaturated. In the cow. the proportion of saturated fatty acids is greater than the unsaturated while in the buffalo this ratio is reversed. Tlie volatile fatty acids in buffalo milk gives a pleasant flavour to the curd. Milk fat also acts as a carrier of the l i t soluble vitamins A,D,E and K ancl contains significant amounts of essential fatty acids. The content of fat has an important bearing on the economics of rnilk and milk products. Most pricing schemes for milk are based on the fat content, since milk fat is reiatively expensive when compared to the other rnilk constituents (Table 4). 'The fat content ofthc I,anka buffalo milk is in .the range of 70-80 g/I and is alrnost doiible that of cow .milk.

Lactose: Lactose or milk sugar is a disaccharide made up oi'a glucose and a galactose molecule and is synthesised within the mammary gland using glllcose frorn the blood. The lactose content in cow and buffalo ~nilk varies from 48 - 52 g1I while in human milk the lactose content is approximately 70 dl. Therefore, when cow or buffalo milk i s used as an infant formula, it has to be fortified with lactose or another source of'carbohydrate.

Casein: When compared to cattle, buffaloes are more efficient converters of digestEble nitrogen into milk proteins. Casein is the main milk protein. Buffalo casein is less easily digested than cow casein.

l'able 3. A comparison of major milk constiti~ent conrents in the Lanka buffalo with that of human, cow and goat.

-- Constituent Buffalo Human Cokv -- Goat Fat (gll) 7 5 38 3 7 4 1 'Total Protein (gll) 5 2 9 3 3 33 Casein (g!I) 44 2.5 28 25 Lactalbumin (511) 6 6.4 4 4 13-Lactoglobulrn (gll) 2 nil 3 2 Lactose (~11 ) 43 70 44 43 Calcii~rn (mg/l) 1560 297 1170 1300 i'hosphate (mgll) 1000 270 960 1060 Sodium (mgll) 46 15 58 4 1 Iron (mgll) 0.2 0.2 0.1 0.05 Enernv kcalsil 100 69 67 76 Source: I loradagoda. ( 199 1)

Ash: Buffalo milk contains higher amounts of calcium and phospl~orus D~ie to the high calcium content, buffalo inilb coagulates much faster than COW milk and also the coagulate is rnore firm. In contrast. sodium, potassium and chloride concentrations arc higher in LOW ~ n i l k than in buffalo milk.

Other co~istit~ients rich in buffalo mllL are vitamins A and B complex. The most obvious visual difference between buffalo and cow inilk is that buffalo ~n i lk appears white while cow milk is more yellowish. 'Phis difference in colour is duc to the fact that the buffalo is able to convert [3-carotene, a yelloh p~glnent mule cfficier~tly to vitamin A vvhiih 1s ~olur less .

Fable 4. Tlie current milk priczs" in relation to milk Tat YO and SNF

Milk fat O/o Solids-r~ot-fat K upees/l itre

3.2 ,

12.0 1

5.0 14.20

9.5 17.17 19.52

*Price srructurc applicable i n 1997

The higher contents of butter fat, solids-not-fat (SNF) and minerals, make buffalo milk superior to cow milk. In Sri i,anka. as milk is priced on the milk Sat and S N F (which is reflected on the lactomeler reading;) a litre of bt~ffalo milk fetches a higher price than cow milk. The proportion of buffaloes milked vary between districts (refer Chapter 2). In districts such as Batticaloa, Matara and i ia~nbantota over 95 per cent of the buffaloes are milked while in other districts the number of animals milked is r r~~ lch lower. On an average about 30 per cerit of the adult female buf'falo population is milked 1181.

Quality of milk

Milk is a rapidly perisliable commodity. Being a nutritious medium it is ri good nlediurn for the growth of microorganisms. 'I'he tropical environment also plays a vital role in regulating milk quality. Thus rnilk must be handled ni th care to kccp it safe for cons~lrnption. In this regard, fanners need to play a major role in improving the

quality of milk. Clean milk production can be encouraged by renumerating farmers on the basis of bacterial counts and keeping quality in addition to the fat and SNF contents.

Utilisation of buffalo milk

In Sri Lanka, buffalo milk i s generally not consumed as fresh liquid milk. It is often processed to prepare value added products such as curd, yogurt, ghee, condensed milk, cottage cheese, Mozzarella cheese and butter. In areas where such dairy products are not prepared, fresh milk is sold to the collecting network either as buffalo milk or after mixing mith cow's milk.

Curd: In Sri Lanka, buffalo milk is widely used in the preparation of curd. Curd is prepared by inoculating boiled cooled milk with a small portion of lactic starter culture which is usually the curd prepared on the previous day. I his rnixture is allowed to ferment for 24 - 72 hours. I'he common bacteria used in this starter culture are Lactobuczllus acidophilus, Lactohaczllus b ~ f i d u ~ and Lactobacillus bulgaricus. During fernenlation, bacterial enzymes partially hydrolyse the protein to proteoses and peptones making the protein of fermented milk more digestible. In the presence of acid, casein gives fine coagulate particles which are more readily accessible to gastric juice and moreover the water-soluble vitamins are better preserved in curd than in fresh milk. Retention of nitrogen, phosphate, calciun~ and iron are also higher in fermented milk than in fresh milk.

In the Southern and Eastern provinces, curd preparation is a popular cottage industry. In Sri Lanka curd is traditionally marketed in clay pots. More recently in some parts of thc country plastic containers have replaced the clay pots as thcy have been found to be cheaper and more durable during transport. However, consumers still prefer .to purchase curd in clay pots as the curd .in plastic containers is thought to taste more sour than that in clay pots. Indeed. from an environmental perspective, containers made of clay are preferred as they are easy to dispose iinlilce plastic.

Condensed milk: Condensed milk is prepared by concentrating milk by heating. The viscosltj of the milk is further increased by the addition of sugar and butter fat. Milk with a high fat content is preferred in the preparation of condensed milk and this fact has been taken into consideration when locating the condensed milk factory at

Polonnaruwa, where a large buffalo populatior~ exists. Condensed milk is widely used in the confectioner- and food industry where milk is an essential component of the recipe.

Gher: In the Indian sub-continent, buffalo milk is skimmed and the fat extracted is used in the preparation of ghee which is an important part of the diet. Ghee is an oil decanted after heating milk fat for about 12 hours and it is a good source of energy. Ghee can be preserved for many years without adding salt or any other preservatives.

Cream: Buffalo milk is best suited for cream preparation owing to its high fat content and whitish colour. Cream, which is an extract of milk mainly contains fat while about a third consists of protein and lactose. Cream is divided into different types according to the butterfat content; half crearn contains 12% of butterfat, double cream contains 185141 while whipping cream contains 35 % bcltterfht. These creams are widely used in desserts, pastries and in the confectionery industry. Further. cream extracted from buffalo milk is offered when coffee and other beverages are served in hotels.

Soured milk: In India, soured milk is an important ingredient in the diet. This is prepared by boi!ing the milk in an open pan and allowing it to cool after which fresh lemon juice is added to allow curdling. The curdled mi!k (soured milk) is collected after removing the water by straining it through a piece of muslin. Soured milk mainly contains clotted proteins and thus has a high nutritive value. Food prepared from soured milk is less likely to be contan~inated with micro- orgar~isms and therefore has 2 longer shelf-life.

Mozzarella Cheese. Originally, Mo~zarclla c h e e ~ e was produced in Italy as a cottage industry [ I 91. Over the years, the popuiarity of this cheese has increased ~vorld-widc and at present Mediterranean buffalo milk is primarily processed for preparation of Momrella cheese. In the nmnufacture of this type of cheese, fresh buffalo milk is first inoculated with a culture to curdle the milk. 'This curd is allowed to acidify and later rrlelted in hot water. The melted checse is then kneaded and stretched until itbecomes a ?oft and homogeneous mass which is cut and shaped. Finally the cheese is hardened in cold brine. Mozzarella cheese is an essential ingredient in "Pizza", a globally known traditional Italian delicacy. At present M o ~ ~ a r e l i a cheese is prepared at some commercial dairies and with the increasing arrival of

tourists to the country, one could expect a greater demand for this product.

Powdered milk: Buffalo milk is used along with cow milk in the manufacture of powdered milk. In India, partially skimmed bufralo milk is used in most of the infant milk formulae. In Sri I.anka, fill1 cream powdered milk (27.5 Yo fat) is widely consumed in preference to fresh milk owing to the convenience, higher keeping quality and availability. Buffalo milk with its high fat content is most suited for full cream milk powder production.

'The milk production potential of the buffalo is to a great extent, under-exploited. Many of the Third World countries of Asia are in tropical and subtropical regions, where natural grasslands are limited and livestock farmers have to rely on poor quality forage to feed animals. The ability of the buffalo to better utilise crude fibre for milk production makes it an ideal choice within such an environment 1201. The low productivity of the animal is a limitation which has to be overcome by upgrading with exotic river type breeds. Further, to increase the utilisation of buffalo milk farmers should be educated on clcan milk production and on the preparation of value added products.