Fermented Milk and History|Beneficial & Therupatic effects of Fermented Products

Nutritional Function of Fermented Milk Products by functional enhancement of key ingredients

Lactose (Milk sugar) in Fermented Milk and its benefits

• Lactose is considered as an excellent food for babies and has a favourable effect in the intestinal tract. Lactose requires longer time for digestion; this provides a suitable medium for beneficial probiotic bacteria including Lb. acidophilus and bifidobacteria, .
• The beneficial effect of lactose on the absorption of calcium is well established. Lactose stimulates gastrointestinal activity. Lactose increases the capacity of the body to utilize phosphorus and calcium.
• Polysaccharides such as cellulose (e.g., carboxymethylcellulose) are generally added to yoghurt mix as a stabilizer and many of these polysaccharides are considered as “Bifidus factor” and may prevent constipation by providing bulk.
•  Lactic acid acts as a preservative by reducing pH, which inhibits the growth of potentially spoilage and harmful bacteria. Lactic acid also influences physical properties of casein curd to induce a finer suspension, which appears to promote digestibility.
• During fermentation, lactic acid bacteria convert 20–30% of lactose into lactic acid. Consequently, the lactose levels in fermented milk can be lower than milk. Fermented milk with lower lactose content is better tolerated by lactose-intolerant individuals.
• Yoghurt in general is supplemented with 2–4% skim milk powder, so the protein and sugar contents are usually higher than cow’s milk. Even after fermentation, the product may contain 4–5 g of lactose per 100 g of the product . Nevertheless, yoghurts fortified with skim milk powder and containing higher levels of lactose also appear to be tolerated by lactose malabsorbers.

Milk Proteins in Fermented milks and its benefits

• Milk protein is considered to be of high nutritional value in terms of its biological value, net protein utilization, and protein efficiency ratio. The proteins in milk are of excellent quality as caseins and whey proteins (alpha lactalbumin and  beta-lactoglobulin) contain high levels of essential amino acids.
• Protein content of fermented milks such as yogurt is often increased due to supplementation with skim milk solids (typically,2–3%). This means that it is an even more attractive source of protein than its liquid counterpart.
• The levels of soluble proteins, nonprotein nitrogen and free amino acids are higher in yoghurt as a result of heat treatment to milk and breakdown of casein by starter bacteria. Lactic acid bacteria require amino acids for their growth; they break down milk proteins due to their proteolytic activity.
• Protein in fermented milks is reported to be totally digestible. Fermented milks are more digestible than milk due to proteolytic activity of starter bacteria resulting in higher levels of peptides and amino acids .
• Feeding of yoghurt resulted in increased weight gains and increased feed efficiency in rats compared to that of milk from which it is prepared.  Thus, it can be assumed that yoghurt made with Str. thermophilus will have a growth-promoting effect, possibly due to enhanced bioavailability of minerals, in particular iron. This indicates a higher protein value of fermented products compared to unfermented milk. Consumption of 250 g of fermented milk per day can serve an individual with the minimum daily requirement of animal protein, which is reported to be 15 g .
• Milk is heat-treated (typically 85◦C for 30 min) for making most fermented milk. This results in soft curd when milk proteins are coagulated by the acid produced by yoghurt starter bacteria.
• Milks with softer curds resulting from such high heat treatment show more human milk like characteristics and are more digestible as a substitute for mother’s milk than harder curds. Further, the more open nature of the casein aggregates allows the proteolytic enzymes of gastrointestinal tract freer access during digestion. The soft curd does not give rise to any feeling of discomfort; this is very important in children.
• The curd formed from milk in the stomach of the young by the action of chymosin and pepsin is less accessible to subsequent enzymatic digestion. The digestibility of milk protein is the highest (>90%) among proteins. This may be due to decrease in protein particle size and an increase in soluble nitrogen, nonprotein nitrogen and free amino acids during heat processing of milk and proteolysis by starter bacteria.

In general, yogurt has been found to be more digestible than milk.

Milk Fat as an energy source and Essential Vitamins in Fermented Milk

• Milk fat is highly digestible. The lactic acid in fermented milk has been found to promote peristaltic movement, which improves overall digestion and absorption of food. Traditional yoghurt contains 3–4% fat. Concentrated yoghurt (labneh) or yoghurt from sheep milk may contain 7–8% fat. . The overall energy (calorie) content of yoghurt reflects both the fat content of the milk from which it was made and the supplementation of ingredients such as cream or sugar.
• Milk fat improves the consistency and mouthfeel of the product. Milk fat has the highest value as an energy source with each gram of fat provides 9 kcal. Milk fat supplies essential fatty acid including linoleic and linolenic acid and fat-soluble vitamins such as vitamin A, carotene, vitamin D, E, and K.
• Choline, a constituent of a phospholipid, promotes the oxidation of lipids in the liver and acts to maintain an equilibrium cholesterol concentration. Yoghurt is reported to produce hypocholesterolaemia effects.

Enhancement in Absorption of Vitamins and Minerals in Fermented Milk

• Milk contains more calcium than other foods. Similarly, absorption of calcium is better from milk than from other forms. The mineral content is hardly altered during fermentation; however, reports suggest that the utilization of Ca, P, and iron in the body is better for fermented milk than that of milk. One possible reason could be phospho-peptides released by the hydrolysis of casein that accelerate absorption.
• Animal studies on the amount of calcium in bone and bone weight and strength suggested that lactic acid was involved. These observations suggest that calcium absorption from fermented milk is better than the unfermented counterpart. The utilization of Ca and P in the body is known to improve in the presence of lactose and vitamin D. Calcium is required for bone metabolism and prevention of osteoporosis.
• Yoghurts contain an appreciable quantity of sodium and potassium and thus may not be suitable for feeding babies less than 6 months unless these minerals are reduced prior to yoghurt manufacturing.
• Fermented milk is an excellent source of vitamin B2 and also a good source of vitamin A, vitamins B1, B6, B12, and pantothenic acid. The level of fat-soluble vitamins, particularly vitamin A, is dependent on the fat content of the product. Some lactic bacteria are able to synthesize the B vitamin folic acid.
• Vitamin content of yoghurt, in general, is higher as starter bacteria synthesize certain B group vitamins during fermentation. Levels of some B vitamins, particularly vitamin B12, are reduced due to the requirement of some lactic acid bacteria for this vitamin.