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Milk and Milk products
Properties of milk
Water: It constitutes the medium in which the other milk constituents are either
dissolved or suspended. Most of it is ‘free’ and only a very small portion is in
the ‘bound’ form, being firmly bound by milk proteins, phospholipids, etc.
Milk fat (lipid): The bulk of the fat in milk exists in the
form of small globules, which average approximately 2 to 5 microns in size (range 0.1 to
22 microns). The thickest cream layer is secured from milks, which have higher fat
content, and relatively large fat globules (such as buffalo’s milk when compared with
cow’s milk).
Milk proteins: The proteins of milk consist mainly of casein, b -lactoglobulin, a
-lactalbumin, etc. Casein exists only in milk and is found in the form of a calcium
caseinate-phosphate complex. It is present in the colloidal state. It forms more than 8
per cent of the total protein in milk.
Milk sugar or lactose: Lactose is responsible, under certain
conditions, for the defect known as ‘sandiness’ in ice cream and sweetened
condensed milk.
Mineral matter or ash: The mineral matter or salts of milk include
potassium, sodium, magnesium, calcium, phosphate, citrate, chloride, sulphate and
bicarbonate, although present in small quantities, exert considerable influence on the
physico-chemical properties, exert nutritive value of milk.
Minor milk constituents
Phospholipids: Phospholipids are excellent emulsifying agents, in milk three types of phospholipids, viz.
Lecithin, cephalin and sphingomylin are present. Lecithin contributes to the
‘richness’ of flavour of milk.
Pigments: These are
1) fat soluble, such as carotene and xanthophyll, and
2) water
soluble, such as riboflavin.
Carotene (the pure substance of which has a reddish-brown
colour) is fat soluble and responsible for the yellow colour of milk, cream, butter, ghee
and other fat-rich dairy products and acts as an anti-oxidant and also as a precursor of
vitamin A. Riboflavin gives the characteristic colour to whey.
Enzymes: The important milk enzymes and their specific actions are as follows.
1)
Analase (diastase) – starch splitting,
2) Lipase – fat splitting, leading to
rancid flavour,
3) Phosphate – capable of splitting certain phosphoric acid esters
(basis of phosphatase test for checking pasteurization efficiency);
4) Pro-tease –
protein splitting;
5) Peroxidase and Catalase – decomposes hydrogen peroxide.
Vitamins: Those found in milk are; fat-soluble vitamins A, D, E and K; and water-soluble
vitamins of the ‘B-complex’ group (such as thiamine or B1, riboflavin
or B2, pantothenic acid, niacin, pyridoxine or B6, biotin, B12,
folic acid, etc.) and vitamin C (ascorbic acid).
Acidity and pH of milk
Acidity: Freshly drawn milk is amphoteric in nature and the pH of normal, fresh, sweet milk usually
varies from 6.4 to 6.6 for cow milk and 6.7 to 6.8 for buffalo milk.
Density and Specific Gravity The average specific
gravity ranges (at 600F) from 1.028 to 1.030 for cow milk, 1.030 to 1.032 for
buffalo milk and 1.035 to 1.037 for skim milk. Milk is dense than water.
Freezing point of milk Milk freezes at
temperatures slightly lower than water due to the presence of soluble constituents such as
lactose, soluble salts, etc., point depression of Indian cow milk may be taken as 0.5470C
(31.020F) and buffalo milk 0.5490C (31.010F).
Colour of milk The carotene (to some
extent xanthophyll) which imparts a yellowish tint to milk. Milk ranges in colour from
yellowish creamy white (cow milk) to creamy white (buffalo milk).
Flavour The flavour of milk is a blend of the sweet taste of lactose and salty taste of minerals, both of which are damped down by proteins. The phospholipids, fatty acids and fat of milk also contribute to
the flavour.
Milk products
Milk is only used as such but many products, non-fermented and fermented are used in cookery.
Non-fermented products:
Skim Milk: Fat is removed by centrifugation in
skimmed milk. Fat content is reduced to 0.5%-2%. Usually this milk is fortified with
vitamins A&D. Condensed milk finds extensive use in baking industry and manufactured
of confectionery. Skim milk is used for low calorie diets and for children who need high
protein.
Evaporated milk: In this type about 50-60% of water is
evaporated. Raw milk is concentrated in vacuum pan at temperature of 74-77%.It is
fortified with vitamin D and homogenized.
Sweetened condensed milk: The product is made from pasteurised milk that is concentrated and sweetened with sucrose. Sugar concentration is 65%.
Dry milk : It can be made with whole milk or
skimmed milk. Milk powder can be dehydrated by spray drying or vacuum drying. The low cost
good shelf life makes it valuable product.
Khoa:Khoa is a partially dehydrated whole milk product.
Method of preparation:
Milk is cautiously stirred in a circular motion to prevent scorching. When milk
becomes viscous the rate of stirring is increased to maintain a uniform consistency. The
pan is removed from the fire and the product is worked up with the flattened end of the
scraper by alternatively spreading into thin layers and collecting repeatedly until it
retains its shape. After cooling it becomes solid. Nearly 36% of the country’s total
khoa production takes place in U.P.
| Composition | ||
|---|---|---|
| Characteristics | Cow | Buffalo |
| Moisture | 25.6 | 19.2 |
| Fat | 25.7 | 37.1 |
| Protein | 19.2 | 17.8 |
| Lactose | 25.5 | 22.1 |
| Ash | 3.8 | 3.6 |
| Iron (ppm) | 103 | 101 |
Kheer: Kheer is also known as Basundi. It is used for
direct consumption as desert. It is prepared by concentrating milk to half of its original
volume by open pan concentration and adding sugar and other condiments.
Method of preparation:fresh, sweet, cleaned milk standardized to 4.0% fat and vigorously boiled in a
jacketed stainless steel pan for 3 to 5 minutes accompanied by constant stirring cum
scraping with a khunti. High-grade rice 2.5%of milk, pre-cleaned and washed with cold
water before use, is now added. The mixture is gently boiled, with periodical
stirring-cum-scraping. When the concentration is about 1:8:1, clean, good quality sugar is
added @ 5% of milk. Gentle heating is continued for another 3 to 5 minutes till a final
concentration of about 2:1 is obtained. The yield of finished kheer should be about 50% of
the milk used.
Ultra high temperature processed milk:
Milk is heated at
temperature higher than pasteurization temperature, 138-1500C for 2-6 seconds.
Then, under
sterilised condition it is packed and aseptically sealed. Hydrogen peroxide may be used to
sterilise the milk packaging.
Rabri: It is prepared concentrated and sweetened product comprising of several layers of clotted cream. The layer of cream formed, as a skin is continuously removed. When the
milk is reduced to 1/3 of the original volume, sugar is added and the layer of cream skin
is mixed.
| Composition | |
|---|---|
| Characteristics | % |
| Moisture | 30 |
| Fat | 20 |
| Protein | 10 |
| Lactose | 17 |
| Ash | 3 |
| Sugar | 20 |
Chhana:Chhana, also called panir in certain parts of the country, constitutes one of the two chief bases (the other being khoa) for the preparation of indigenous sweetmeats. Chhana refers to the milk-solids obtained by the acid coagulation of boiled hot whole milk and subsequent drainage of whey. The acids commonly used are lactic or citric, in both natural and chemical forms. It should not contain more than 70% moisture, and the milk fat content should not be less than 50.0 per cent of the dry matter.
| Composition | ||
|---|---|---|
| Characteristics | Cow (%) | Buffalo (%) |
| Moisture | 53.4 | 51.6 |
| Fat | 24.8 | 29.6 |
| Protein | 17.4 | 14.4 |
| Lactose | 2.1 | 2.3 |
| Ash | 2.1 | 2.0 |
Method of production: There are two methods for making chhana,
which are adopted by commercial manufacturers. Batch method and bulk method is used for
its preparation.
Ice Cream:It is frozened
product consisting of whole milk, skim milk, cream, butter,condensed milk product or dried
milk products. Milk fat and milk solids constitute about 60% of total solids of ice cream.
Sugar is added for smoothening and lowers the freezing point. Stabiliser used to prevent
the formation of ice crystals during heating.
Percentage composition Ice Cream
| Constituents | % |
|---|---|
| Milk fat | 12 |
| Milk solids-not fats | 11 |
| Sugar | 15 |
| Stabiliser | 0.2 |
| Emulsifier | 0.2 |
| Essence | traces |
Fermented milk products
Buttermilk
Condensed buttermilk
Also known as semi-solid buttermilk,
this is usually sweet cream buttermilk which has been ripened and condensed (approx. 3:1)
in much the same way as concentrated sour skim milk. Alternatively, sour-cream buttermilk
may be used without ripening it, but the acidity (lactic) of the buttermilk prior to its
being condensed should be greater than 1.6 %. This will ensure in the finished product a
5-6 per cent acidity, which is necessary for long keeping quality. Either sour whey or an
organic acid (such as lactic, acetic, citric or tartaric) may be used to increase the
acidity of buttermilk.
Cheese: - Cheese has a high protein content in a very digestible form, is rich in calcium
and phosphorous, and is an excellent source of fat-soluble and water-soluble vitamins. It
is concentrated form of energy, contributing 4cal/g and is also a highly suitable food for
those suffering from lactose intolerance. Cheese is a bio-enriched food the enrichment
being brought about by vitamins and micronutrients being produced as metabolites of the
starter bacteria. Although the precise mechanisms are not known, there is sample evidence
to suggest that the consumption of cheese at the end of a meal prevents dental caries by
reducing the thickness of the film formed on teeth, the degree of abrasion of the chewing
surfaces, dental surface defects and caries.
Panir: -
Panir refers to the indigenous variety of rennet-coagulated, small-sized, soft cheese.
| Composition | ||
|---|---|---|
| Characteristics | Cow (%) | Buffalo (%) |
| Moisture | 71.2 | 71.1 |
| Fat | 13.5 | 13.1 |
| Total solids | 28.8 | 28.9 |
Method of preparation:Surati Cheese or panir is the best known
of the few indigenous varieties of cheese. The name Surati appears to have been derived
from the town of Surat.
Srikhand: - Srikhand is a semi-soft sweetish sour, whole milk product prepared form lactic fermented curd. The basic ingredient of Srikhand is Chakka.
Method of preparation: - the standardized method of preparation consist of fresh, sweet buffalo milk,
which has been standardized to 6% fat, is pasteurized at 710C for 10 minutes
and then cooled to 28-300C. It is then inoculated @ 1% with lactic culture
which is mixed well, and incubated at 28-300C for 15-16 hours. When the curd
has set firmly (acidity 0.7-0.8% lactic), it is broken and placed in a muslin cloth bag
and removed after 8 to 10 hours. Now the curd gets change into a solid mass called Chakka.
This Chakka is then mixed with grinded sugar. Colour and flavour can also be added to
obtain the product known as Srikhand.
Ghee: Ghee is a clarified butter fat prepaired from cow or buffalo milk. The largest ghee producing states are U.P, A.P, Punjab, Rajasthan, M.P, Bihar,
Hariyana etc. The production of ghee is higher in winter and lower in summer.
Method of preparation: cream accumulated after few days is usually taken in a suitable vessel and
heated and stirred on a low flame to remove the moisture contain. After removing moisture
contain further heating is stopped then cooling is done. On cooling, when the residue has
settled down the clear fat is decanted into suitable containers.
| Composition | ||
|---|---|---|
| Characteristics | Cow (%) | Buffalo (%) |
| Milk fat | 99 to 99.5% | |
| Moisture | Not more than 0.5% | |
| Unsaponiable matter | ||
| Carotene (m g./g.) | 3.2-7.4 | - |
| Vit. A (I.U./g.) | 19-34 | 17-38 |
| Charred casein, salts of copper and iron, etc. |
Max.2.8 (Agmark) Traces | |
Lassi: - Lassi, also called chhas or matha, refers to desi buttermilk, which is the by-product obtained when churning curdled whole milk with crude indigenous devices for the production of desi butter (makkhan). It appears that 50-60kg. (ave.55kg) of lassi are producted for every kg of ghee. Lassi contains appreciable amounts of milk proteins and phospholipids.
| Composition | ||
|---|---|---|
| Characteristics | Milk (%) | |
| Water | 96.2 | |
| Totalsolids | 3.8 | |
| Fat | 0.8 | |
| Solids-not-fat | 3.0 | |
| Protein | 1.3 | |
| Lactose | 1.2 | |
| Ash | 0.4 | |
| Lactic acid | 0.44 | |
| Fat | 20 |
| Protein | 10 |
| Lactose | 17 |
| Ash | 3 |
| Sugar | 20 |