1. Is raw milk safe for consumption?
The raw milk is not safe for consumption, unless and until the health of the milch cow or buffalo and the environment in which the milk is produced and handled till it reaches the consumer is definitely known, it is always advisable to drink pasteurized milk or boiled milk from the safety point of the consumer.
2. What is pasteurization?
Pasteurization refers to the process of heating milk to at least 63oC for 30 min (LTLT method) or 72oC for 15 sec (HTST) or to any approved temperature-time combination which is equally efficient in an approved and properly operated equipment. Immediately after pasteurization, the milk is invariably cooled to 5oC or below.
3. Why does raw milk curdle when heated after standing at room temperature for considerable period of time?
Milk contains a variety of microorganisms, which are capable of converting lactose present in the milk to lactic acid, increasing the acidity. When the milk is stored at room temperature (30-37oC) for considerable period of time, it provides ideal temperature for the growth of most of the harmful organisms and in turn increases the acidity. When the acidity increases beyond 0.20% of lactic acid, the milk starts clotting on boiling or heating.
4.What is responsible for the characteristic flavour in curd?
Curd is a fermented dairy product produced by souring milk with mainly lactic starter cultures, which include Lactococcus lactis subspecies lactis, Lactococcus lactis subspecies cremoris and Lactococcus lactis subspecies lactis biovar diacetylactis. Sometimes, the starter may contain Leuconostocs. The Lactococcus lactis subspecies lactis, Lactococcus lactis subspecies cremoris are capable of fermenting lactose present in the milk into lactic acid resulting in coagulation of milk whereas the Lactococcus lactis subspecies lactis biovar diacetylactis is both lactose and citric acid fermenter. Citric acid fermentation results in the production of end products such as diacetyl, acetoin and 2,3 butylene glycol which are responsible for the characteristic desirable flavour production. Leuconostocs are purely citric acid fermenting bacteria and hence responsible for flavour production but not acid.
5.Why do strict vegetarians refuse to consume ice cream made with gelatin as a stabilizer?
For ice cream production, stabilizers such as gelatin, sodium alginate, carageenan, agar etc. are used. Stabilizers are added in ice cream to produce smoothness in body and texture, retard or reduce ice crystal growth during storage and provide uniformity in the product and resistance to melting. Although the gelatin was the one of the first commercial stabilizers and it is still used, it is obtained from the bone of animals. Hence strict vegetarians often oppose its use as stabilizer in ice cream. Instead, it can be replaced by sodium alginate.
6. Why does milk appear white?
The normal milk ranges in colour from yellowish creamy white (cow milk) to creamy white (buffalo milk). The colour of milk is due to the combined effect of colloidal casein particles and the dispersed fat globules, both of which scatter light and carotene and to some extent xanthophylls, which impart a yellowish tint to milk. The intensity of yellow colour of cow milk is dependent upon factors such as breed, feed, size of fat globules present in milk, fat percentage. In buffalo milk, the carotene is present in the form of vitamin A. Skimmed milk has a bluish and whey, a greenish yellow colour. ----
7. How to detect milk adulterated with water?
Milk adulterated with water can be easily found out with an instrument called ‘lactometer’. The lactometer measures the specific gravity of milk. The average specific gravity of milk ranges (at 60oF) from 1.028 to 1.030 for cow milk and 1.030 to 1.032 for buffalo milk. If lower values are found than the standard measurements, then it indicates that the milk is adulterated with water.
8. Can I make Ice Cream in my home with conventional refrigerator?
No. It is not possible to prepare ice cream in home with the conventional refrigerator. After the preparation of ice cream mix, it is frozen in the ice cream freezer (batch type or continuous) along with incorporation of air during the freezing process. This step is very essential to get proper body and texture in the finished product.
9. What is the reason for fishy flavour in butter?
Under commercial storage conditions (-23oC to -29oC), high acid salted butter develops fishy flavour in the presence of appreciable amounts of copper and / or iron content. To avoid this defect, unsalted sweet cream butter may be used.
10. What is rennet? Where is it used?
Rennet is a crude preparation or extract obtained commercially from the fourth stomach (abomasum) of young calf, known as vell. The preparation methodology include washing, drying and cutting of the lining of the stomach in to small pieces and macerating it in to water containing about 4 percent boric acid at 30oC for 5 days. Rennet is used in clotting of milk, especially in cheese production. It may be used along with starter cultures.
11. How much energy shall I get from 100 ml of milk?
The energy value of milk varies with its composition. On an average cow milk furnishes 75oC per 100 g and buffalo milk 100oC per 100 g. Component wise, milk fat furnishes 9.3 C / g, milk protein 4.1 C / g and milk sugar (lactose) 4.1 C / g.
12. What is the difference between Maillard browning and caramelization?
The darkening of colour commonly referred to as browning discolouration is a defect, which develops during the manufacture and storage of condensed milk varieties. The browning results from the interaction of amino compounds with sugar i.e. mainly casein with lactose. This defect is called as Maillard browning. Caramelization or non amino browning occurs in milk products due to heat decomposition of sugar in the absence of amino compounds.
13. What is dry ice?
Dry ice is solid carbon dioxide with a freezing point of -78oC (-109oF). It is extensively used for package deliveries of frozen dairy products such as ice cream. It is cut into pieces of appropriate size, which are wrapped in paper to avoid rapid evaporation and then placed around the package of the ice cream inside an insulated packer or in a single service type packer.
14.What is lactose intolerance?
Lactose is the milk sugar present in milk. It acts as a source of energy not only for the individuals who consume milk but also for the microorganisms in milk. Normally, lactose is converted to glucose and galactose, which are subsequently converted to lactic acid and absorbed from the intestine. Beta galactosidase is the enzyme that plays a major role in the conversion of lactose in to lactic acid. Lactose intolerance develops when the secretion of enzyme beta galactosidase decreases. Undigested lactose absorbs excess water, while passing through the large intestine. Bacteria present in large intestine act on the lactose and convert it in to acid and gas. This acid, gas and excess water are responsible for flatulence, stomach pain and sometimes enteritis.
The ability to digest lactose differs among different human races. This defect is commonly noticed among Asian races. As an individual grows old, the beta galactosidase secretion decreases. It is related to the genetics of the individual. Temporary lactose intolerance is sometimes noticed among children who have been suffering from intestinal disorders and nutritional deficiency diseases.
15.Does milk act as a source of disease?
Definitely, Milk and Milk products act as a source of contamination of various disease causing bacteria such as Salmonella, Shigella, Staphylococci, Clostridium, Bacillus, Pseudomonas, Listeria, Campylobacter, Yersinia, Vibrio, Mycobacterium, Brucella, Corynebacterium, Coxiella and viruses such as Entero viruses, Infectious hepatitis virus, Tick-borne Encephalitis Virus, Foot and Mouth Disease virus. The important mould transmitted through milk products is Aspergillus resulting in aflatoxicosis in the affected individual. The mode of transmission may be through food infection, food intoxication or toxi-infection. Hence it is desirable to pasteurize the milk before consumption.
16. What is probiotic?
'Pro' means for and 'bio' means life. Hence, probiotics are generally considered as agents that favour the well being of a human being or an animal by various mechanisms. Probiotics are generally lactic acid producing live bacteria which, when ingested orally, brings out the desirable effect in the individual by getting implanted in the intestinal tract. The mechanism of action includes competitive replacement of the pathogens from the intestinal tract, production of metabolic compounds inimical to the growth of pathogens etc. Generally lactobacilli, especially, Lactobacillus acidophilus is considered as a good probiotic.
17. What is meant by SNF and total solids?
SNF (Solids Not Fat) is that nutrient portion present in milk devoid of milk fat. It consists of protein and lactose. When SNF is combined with milk fat, then it is called total solids. The legal standards for standardized milk are 4.5% fat and 8.5% SNF and the total solid is 13%.
18. What is the difference between skimmed milk and whole milk?
It all depends upon the fat content of milk. Generally cow milk (whole milk) contains 4.0% milk fat whereas buffalo milk contains upto 9.0% milk fat. Milk fat is the valuable portion of milk, based on which, milk is priced in most countries. When skimming is done to separate the fat by means of a cream separator, cream is obtained as a main product, which is rich in milk fat (approximately 25%) and skim milk as a byproduct (containing less than 0.5% milk fat). It is impossible to remove all fat portion from milk.
19. What is "Clean Milk"?
The term 'clean milk' does not mean milk in which all visible dirt is absent or milk from which all visible dirt has been removed; rather it does denote raw milk from healthy animals, that has been produced and handled under hygienic conditions; that contains only small number of harmless bacteria and that possesses a good keeping quality without being treated by heat.
In other words, the unhygienic production of milk may lead to inferior keeping quality as a result of rapid microbial multiplication under favourable storage conditions apart from serving as a potential health hazard. These microorganisms cause the milk to sour quickly, putrefy and develop undesirable flavours, colour defects, ropiness and bitterness. On the other hand, the pathogenic microorganisms, which may gain entry through various sources, may cause many diseases to the consumers.
20. What is "homogenization"?
Homogenization is one of the basically important processes of the dairy industry. The principle behind the homogenization is that it breaks up the already small fat globules of milk into even smaller globules and stabilizes the emulsion to an extent that prevents any noticeable rising (cream layer formation) of the fat. Milk to be homogenized is pumped under pressure of several thousand pounds through a narrow or constricted orifice, during which the native fat globules are broken down to uniform smaller size of 2 ----.