Curds are a healthy, universally useful food. It is formed by lactic fermentation of milk. Curd is esteemed for its smoothness and its pleasant and refreshing taste. It is highly versatile health promoting and valuable therapeutic foods. Once thought of only as a worthy health food, curd or yoghurt is now the base for tempting frozen desserts and is used as a healthier alternative to cream. The word yoghurt is of Turkish Origin and is believed that the first curd was made in Turkey. People who cannot drink milk may find that they can tolerate curd. Universally cow's milk is used to make curd. But in India, buffalo milk is also used extensively and in Russia, the milk of sheep, goat and mare is largely used for the same purpose.
Curd is a sour milk preparation. Curd or dahi or yoghurt is eaten as such with salt or sugar or added to other preparations. The butterfat is removed from dahi by churning and used to make ghee. Curd has almost the same calorific value of cow's milk. 40 percent of lactose is converted to lactic acid. It has 3.1gm of protein, 4gm of fat, 149mg of calcium, and 93mg of phosphorous.
Curd is reported to have better nutritive value than milk. Though there is no increase in the fat or protein content of milk during fermentation, the digestibility of curd is more than that of milk. The calcium and phosphorous contents of curd are more easily assimilated. Curd contains more vitamins than milk. During curd formation the lactose of milk is converted into lactic acid. There is some breakdown of protein increasing the non-protein nitrogen. The fat globules coalesce and distribute them selves on the top. Physically during curd formation milk proteins are jellied and a thin exudates of clear serum on the curd is seen.
The organism involved in curd formation belongs to the group of lacto bacillus and streptococci. Each of these organisms produces different levels of acidity. The formation of consistently good quality curd depends upon the use of the right type of starter. A starter culture containing a combination of lactobacillus and lactococcus organisms gives good results. Starters containing yeasts, molds and gas forming organisms spoil the quality of curd. When they are present, a product with a homogeneous texture or good aroma will not be obtained. There will be cracks and gas bubbles and the curd will be of poor quality and taste.
The method of preparation and quality of curd depends upon whether it is consumed as such or used for preparation of butter. Curd can be made either from whole milk or skim milk. When whole milk is used it has a creamy layer on top, the rest being made of a homogenous body of curd. The creamy layer can be removed for butter making before consuming curd as such or converting it into lassi or buttermilk.
The best and purest milk should always be used for preparing the curd. In the preparation of curd for consumption as food, milk is brought to a boil in order to destroy viable organisms, cooled to the body temperatures and earlier batch of curd is added as starter. About 5 -10 percent of the volume of milk is added as starter during cold weather. The quality of curd depends to a great extent on the starter used. Lesser quantities are required during summer. Milk is then kept in a warm or cool place depending upon the season. After 6 to 24 hours depending upon the climatic conditions a smooth homogeneous product having an acidity of 0.9 to 1.0 percent acid is formed.
In the preparation of curd for butter making, raw milk is used in some parts of the country. It is allowed to undergo natural fermentation by atmospheric bacteria or by the addition of a small quantity of buttermilk from the previous batch of raw milk curd. The result is a type of curd with gas bubbles and a mouldy flavour, separating into two distinct layers- serum at the bottom and cake of curd on top. This is a very undesirable form of making curd. The buttermilk obtained after separating butter from such a curd will not be fit for use as a beverage. It is always good to use boiled and cooled milk in curd making even if it is required only for butter making.
Curd is used in the preparation of beverages by beating it with water and adding sugar or salt and spices. Srikand is a semi dry mass of curd sweetened with sugar. Suspending curd in a muslin bag until all the whey is drained off makes it. It is then sugared and coloured. It is also used in various food preparations, both vegetarian and non-vegetarian.
Curd is also considered one of the best aids to natural good looks. The bacteria present in curd make the skin soft and glowing. It is also a good hair conditioner and has antidandruff property. Curd mixed with orange or lemon juice is a good face cleanser. It supplies moisture to the skin and fruit juice provides the essential vitamin C. Live yoghurt discourages the proliferation of harmful bacteria and yeasts in the gut that lead to bowel infection. It can help to relieve gastrointestinal disorders, diarrhoea and constipation. It can also reduce bad breath associated with some digestive disorders. Yoghurt is helpful for people suffering from diarrhoea on account of radiotherapy treatment, food poisoning or irritable bowel syndrome. It is often recommended as an external treatment for any one who is suffering from thrush. It is also claimed that yoghurt can improve the condition of the skin and alter the balance of bacteria in the large bowel in a way that may protect against colon cancer. Curd is used in the treatment of insomnia. It is also believed that taking sufficient curd in the daily diet could prevent premature ageing.
By Ms Mumtaz Khalid Ismail