History of Fermented milk Products
- The history of fermented foods is lost in antiquity. It may have been a mere accident when people first experienced the taste of fermented food.
- The first fermentation must have started with the storage of surplus milk, which resulted in a fermented product the next day.
- After drying, fermentation is the oldest food preservation method.
- Fermentation became popular with the dawn of civilization because it not only preserved food but also gave it a variety of tastes, forms, and other sensory sensations.
- Slowly, people over the ages have realized the nutritional and therapeutic value of fermented foods and drinks, and this has made fermented foods even more popular.
- It seems that the art of fermentation originated in the Indian subcontinent, in the settlements that predate the great Indus Valley civilization.
- During the Harappan spread or pre-Vedic times, there are indications of a highly developed system of agriculture and animal husbandry.
- Artefacts from Egypt and the Middle East also suggest that fermentation was known from ancient times in that region of the world.
- It is believed that the knowledge is written in the four Vedas (sacred Hindu writings) came from the experiences, wisdom, and foresightedness of sages, which had been preserved by verbal tradition.
- Both the biological and medical communities now recognise the significance of the role of fermented milk in both health and disease.
- The bacterial microflora of the human gut is widely accepted as an integral component of the functional food industry. A prebiotic is a non-viable component of the diet that reaches the colon in an intact form and is selectively fermented by colonic bacteria.
- The most recent definition regarding a prebiotic is ‘A selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora, that confer benefits on host well-being and health’. The selectivity is by commensal bacteria already resident in the gut that are thought to have beneficial properties to the host regarding the promotion of health.
- Examples of such colonies include Lactobacilli and Bifidobacterial, both of which are present in significant numbers. Health is improved by fortification of such selected bacteria. A schematic representation of the prebiotic concept is shown in Figure.
KEY MILESTONES IN HISTORY OF FERMENTED FOODS
| Mile stones | Development /Location |
| ca.10,000 B.C. to Middle Ages | Evolution of fermentation from salvaging the surplus, probably by pre-Aryans. |
| ca. 7000 B.C. | Cheese and bread making practiced |
| ca. 6000 B.C. | Wine making in the Near East |
| ca. 5000 B.C. | Nutritional and health value of fermented milk and beverages described |
| ca. 3500 B.C. | Bread making in Egypt |
| ca. 1500 B.C. | Preparation of meat sausages by ancient Babylonians |
| 2000 B.C.–1200 A.D. | Different types of fermented milks from different regions |
| ca. 300 B.C. | Preservation of vegetables by fermentation by the Chinese |
| 500–1000 A.D. | Development of cereal-legume based fermented foods |
| 1881 | Published literature on koji and sake brewing |
| 1907 | Publication of book Prolongation of Life by Eli Metchnikoff describing therapeutic benefits of fermented milks |
| 1900–1930 | Application of microbiology to fermentation, use of defined cultures |
| 1970–present | Development of products containing probiotic cultures or friendly intestinal bacteria |
| 1980-1990 | Development of DVC (Direct vat Cultures) cultures |
Origin of Some Important Fermented Milk Products │Health Benefits of Fermented Milk Products
| Product | Characteristics and use | Culture used |
| Dahi/Curd India 6000 4000 BC | Coagulated sour milk eaten as a food item; an intermediate product for making country butter and ghee (clarified butter) | LACTIC CULTURES -Lb. delbrueckii ssp. bulgaricus, Streptococcus thermophilus or Lc. lactis ssp.lactis, Lc. lactis ssp. cremoris, Lc. lactis ssp. lactis biovar diacetylactis, and Leu. mesenteroides ssp. cremoris |
| Chhhach (Butter Milk) India 6000 -4000 BC | Diluted dahi or the butter milk left after churning of dahi into butter; used as beverage after or with meal | Lb. delbrueckii ssp. bulgaricus, Streptococcus thermophilus or Lc. lactis ssp. lactis, Lc. lactis ssp. cremoris, Lc. lactis ssp. lactis biovar diacetylactis, and Leu. mesenteroides ssp. cremoris |
| Laban zeer/Khad Egypt 5000-3000 BC | Sour milk, traditionally coagulated in earthenware vessels | Lactic cultures |
| Leben Iraq Ca.3000 BC | Traditional fermented milk containing yogurt bacteria; whey partially drained by hanging the curd | Lb. delbrueckii ssp. bulgaricus, Str. thermophilus |
| Zabady Egypt 2000 Bc | Natural type yogurt; firm consistency and cooked flavor | Lactic Cultures |
| Cultured cream Mesopotamia 1300 BC | Naturally soured cream | Lactic cultures |
| Shrikhand /shrikhand wadi India 400 BC | Concentrated sour milk, sweetened and spiced; semisolid mass eaten with meals as sweet dish | Cultures used in Dahi/curd. Lactic cultures. |
| Kishk Egypt & Arab world | Dry fermented product made from Laban and par boiled wheat ,hard texture; highly nutritious with high amino acids and vitamin content | |
| Kumys, Kumiss Central Asia (Mongol, Russia) 400 BC | Traditionally mares’ milk fermented by lactobacilli and yeast; sparkling beverage containing lactic acid, alcohol, and carbon dioxide | Lb. acidophilus, Lb. delbrueckii ssp. bulgaricus, Sacchamyces lactis, Torula koumiss |
| Mast Iran | Natural type yogurt; firm consistency and cooked flavor | |
| Villi Finland | High viscosity fermented milk with lactic acid bacteria and mold | Lc. lactis ssp. lactis, Lc. lactis ssp. cremoris, Lc. lactis ssp. lactis biovar diacetylactis, Geotrichum candidum |
| Taette Norway | Viscous fermented milk also known as cellarmilk | |
| Langfil, Tattemjolk Sweden | Milk fermented with slime-producing culture of lactococci | Lactococci cultures used. |
| Ymer Denmark | Protein fortified milk fermented by Leuconostocs and lactococci; whey is separated | |
| Skyr Iceland 870 AD | Made from ewes’ milk by addition of rennet and starter; today concentrated by membrane technology | |
| Prostokvasha Russia | Fermented milk made from ancient times by fermenting raw milk with mesophilic lactic bacteria | |
| Kefir Caucasusian China | Milk fermented with kefir grains; foamy effervescent product with acid and alcoholic taste | Lc. lactis ssp. lactis, Lc. lactis ssp. cremoris, Lc. lactis ssp. lactis biovar diacetylactis, and Leu. mesenteroides ssp. dextranicum, Str. thermophilus, Lb. delbrueckii ssp. bulgaricus, Lb. acidophilus, Lb. helveticus, Lb. kefir, |
| Yoghurt (Kisle Milako) Bulgria | Cow’s or ewe’s milk fermented by Str. thermophilus and Lb. bulgaricus | |
| Yoghurt Turkey 800 AD | Custard like sour fermented milk | Lb. delbrueckii ssp. bulgaricus, Str. thermophilus |
| Bulgrian Milk Bulgria 500 AD | Very sour milk fermented by Lb. bulgaricus alone or with Str. Thermophilus | Lactobacillus delbrueckii ssp. bulgaricus |
| Trahana Greece | Traditional Balkan fermented milk; fermented ewe’s milk mixed with wheat flour and then dried | |
| Churpi Nepal | Fermented milk is churned and the buttermilk remaining is heated to form a solid curd; may be further dried | |
| Airan Central Asia ,Bulgria 1235-1255 AD | Cow’s milk soured by Lb. bulgaricus, used as refreshing beverage | |
| Yakult Japan 1935 AD | Highly heat treated milk fermented by Lb. casei strain Shirota; beverage and health supplement | Lb. paracasei ssp. casei |
Nutritional and Health Benefits of Fermented Foods
| Beneficial Effect | Possible Causes and Mechanisms |
| Improved digestibility | Partial breakdown of proteins, fats and carbohydrates |
| Improved nutritional value | Higher levels of B-vitamins and certain free amino acids, viz. methionine, lysine and tryptophan |
| Improved lactose utilization | Reduced lactose in product and further availability of lactase |
| Antagonistic action toward enteric pathogens | Disorders such as diarrhoea, mucous colitis, ulcerated colitis; prevention of adhesion of pathogens |
| Anticarcinogenic effect | Reduction of carcinogen-promoting enzymes; inhibitory action toward cancers of the gastrointestinal tract by degradation of precarcinogens; stimulation of the immune system |
| Hypocholesterolaemia action | Production of inhibitors of cholesterol synthesis; use of cholesterol by assimilation and precipitation with deconjugated bile salts |
| Immune modulation | Enhancement of macrophage formation; stimulation of production of suppressor cells and -interferon |
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.
Fermented milk in Health
1.Alleviation of Lactose Malabsorption by drinking Fermented Milks
- Lactose malabsorbers often complain of “gastric distress” after consuming fresh, unfermented milk or milk products. Lactose malabsorption is a condition in which lactose, the principal carbohydrate of milk, is not completely hydrolysed into its component monosaccharides, glucose, and galactose. Since lactose is broken into its constituent monosaccharides with the help of lactase or Beta D-galactosidase enzyme, lactose malabsorption results from a deficiency of this enzyme.
- Lactase deficiency is a common problem in many parts of the world. The prevalence of lactose malabsorption varies depending on the ethnic origin of the population. Infants in general have higher lactase activity than adults. Prevalence of lactose malabsorption is common in China, Thailand, Japan, and Africa and Australian aborigines, but less common among Caucasians. Temporary deficiency of beta-galactosidase occurs in people suffering from diarrhoea’s unabsorbed lactose reaches the colon, where it is fermented by colonic flora to volatile fatty acids, lactic acid, CO2, H2, and CH4. The unhydrolyzed lactose withdraws water and electrolytes from duodenum and jejunum. The lactase deficient people can suffer from bloat, flatulence, abdominal pain, and diarrhoea.
- Fermented milk, in particular, yoghurt appears to be well tolerated by lactose malabsorbers and lactose malabsorbers suffer fewer symptoms with fermented dairy foods. Reduced levels of lactose in fermented products are due to partial hydrolysis of lactose during fermentation and is partly responsible for greater tolerance of yoghurt. Factors other than the presence of yoghurt starter are responsible for better tolerance of lactose in lactose maldigests from fermented dairy foods.
- At least three factors appear to be responsible for better tolerance of lactose from yoghurt including (a) yoghurt bacteria, (b) lactase enzyme or beta-galactosidase elaborated by these bacteria.
- The traditional cultures used in making yoghurt (i.e., Lb. delbrueckii ssp. bulgaricus and Str. thermophilus) contain substantial quantities of Beta-D-galactosidase, and it has been suggested that the consumption of yoghurt containing cultures with high levels of lactase may assist in alleviating the symptoms of lactose malabsorption.
- Slower gastric emptying of semisolid fermented milk products such as yoghurt is another factor responsible for better absorption of lactose. Delayed gastric emptying is responsible for the hydrolysis of lactose by indigenous beta-d galactosidase located in the sides and tips of the villi of the jejunum and by bacterial beta d galactosidase. Viscous foods such as yoghurt or foods with higher solids are reported to delay gastric emptying and are effective in alleviating lactose intolerant symptoms.
2.Antimicrobial Activity and Gastrointestinal Infections by use of Fermented Milk
- The gastrointestinal tract has a large number of indigenous microflora. There is a balance between useful microorganisms and harmful microflora. This balance is affected by gastrointestinal illnesses, stress, and use of antibiotics leading to disturbances of its function.
- Fermented milk has been used to improve intestinal health since ancient times. This includes diarrhoea caused by infection due to pathogenic bacteria. Fermented foods are reported to improve the composition and metabolic activity of intestinal microflora.
- Fermented milk has shown beneficial effects on intestinal health. Reduction of infant diarrhoea and antibiotic-associated diarrhoea due to consumption of fermented milk has been reported.
- Consumption of fermented milk has shown to increase the counts of bifidobacteria and decrease the levels of putrefactive compounds in faeces. This is because of the enhancement of intestinal immune function by lactic acid bacteria in fermented milk and antimicrobial substances produced during fermentation, which have shown improvement in intestinal microflora.
3.ANTICANCER EFFECT OF FERMENTED MILK
Yoghurt has been found to reduce the levels of bacterial enzymes, glucuronidase, azoreductase, and nitroreductase. These enzymes are believed to contribute to the pathogenicity of bowel cancer as they catalyse the conversion of procarcinogens to carcinogens (Lankaputhra and Shah, 1998; Goldin and Gorbach,1977, 1984, Cenci et al., 2002).
- Cancer is one of the main causes of death in the world. Epidemiological studies suggest that cancer is caused by environmental factors, particularly diet.
- Several factors are responsible for causes of colorectal cancer including bacteria and metabolic products such as genotoxic compounds (nitrosamine, heterocyclic amines, phenolic compounds, and ammonia). Many bacterial enzymes such as beta-glucuronidase generate these carcinogenic products, except lactic acid bacteria and probiotics, such as Lactobacilli and bifidobacteria.
- Lactic acid bacteria and fermented products have potential anticarcinogenic activity. An inverse relationship between the consumption of fermented dairy foods and the risk of colorectal cancer has been found. Lactic acid bacteria suppress bacterial enzymes and reduce intestinal pH.
- Several studies have shown that fermented dairy products or preparation containing lactic acid bacteria inhibit the growth of tumour cells in experimental animals. Animal studies using chemical carcinogen 1, 2-dimethyl hydrazine (DMH) have been carried out. Rats were given DMH to induce colon cancer and fed with fermented milk. DMH is activated in the large intestine by beta-glucuronidase. Addition of Lactobacillus to the diet has been reported to delay tumour formation. The inhibitory effects of fermented milk on colon cancer are either because of the decrease of mutagenic activity or modification of intestinal microflora.
- Several types of fermented milk including yoghurt, colostrum fermented with Lb. delbrueckii ssp.bulgaricus, Str. thermophilus, and Lb. acidophilus or milk fermented with Lb. helveticus are reported to suppress cancer cell growth.
4.Reduction in Serum Cholesterol
Elevated levels of serum cholesterol, particularly LDL-cholesterol have been linked to an increased risk of cardiovascular disease, which is one of the main causes of death. Cholesterol-lowering properties of fermented milk were observed as early as the 1960s among Masai tribes of East Africa. Mann and Spoerry (1974) observed a decrease in serum cholesterol levels in men fed large quantities (8.33 L/man/day) of milk fermented with Lactobacillus. Those people had low-blood cholesterol levels although they consumed a large quantity of meat.
- Consumption of a high quantity of yoghurt was found to be responsible for lowering of serum cholesterol. Rabbits fed on a high cholesterol diet supplemented with yoghurt showed lower cholesterol levels as compared to the diet supplemented with nonfermented milk.
- Cholesterol-lowering effects of yoghurt have been reported in human volunteers. The subjects consumed 240 mL of yoghurt three times per day. The role of fermented milk in reducing serum cholesterol is not completely understood.
- Cholesterol is an essential component of cell membrane and is required to produce certain hormones and bile acids. It is synthesized by the liver and from absorbed foods.
- The mechanism of controlling blood cholesterol level is complex. The metabolite of starter cultures in fermented milk is reported to produce hydroxymethyl-glutarate, which inhibits hydroxymethylglutaryl-CoA reductase, an enzyme required for the synthesis of cholesterol in the body. This could limit cholesterol synthesis.
5.Immune System Stimulation by use of fermented Milk
- The health benefits of fermented milks are primarily because of the ability of starter bacteria to survive in the gastrointestinal tract. Yogurt starter bacteria are reported to survive in the stomach and are also found in feces.
- The intestinal system defends the body against bacterial and viral infection and cancer and allergies. The intestine is the body’s largest immune organ and the intestinal microflora and the metabolic activity of intestine is equivalent to that of the liver.
- The intestinal tract works as a peripheral organ to protect against intestinal infections and affects systemic immunological function. Its function is affected by intestinal microflora.
- The mechanism for immunomodulation is not clearly understood. Lactic acid bacteria (LAB) are likely to, directly or indirectly (by changing the composition or activity of the intestinal microflora), influence the body’s immune function, but the mechanism is not fully understood.
- Fermented milk has been reported to inhibit infections in mice caused by Klebsiella pneumonia. Mice fed with fermented milk were healthier and lived longer. In a human clinical study, feeding yoghurt starter bacteria in yoghurt increased the serum level of gamma-interferon and NK cell count.
- Yoghurt bacteria are reported to have nitrate reductase activity. Nitrate is an intermediate product in the formation of N-nitroso compounds, which are highly carcinogenic.