Unit1_dairymicrobiologypptx__2023_02_08_12_43_16.pptx

Dairy microbiology

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2. Subject name Applied Microbiology Subject Code: 02MB0353 Unit 1 Food Microbiology and Dairy Microbiology Department of Microbiology Dr. Niralee Patel Food and Dairy Microbiology

3. Food Microbiology: Food spoilage and microbial flora of fresh foods, Preservation of food, Microbiological examination of food, Fermented products and microorganisms as a food. Dairy Microbiology: Fermented dairy products: Starter Culture, Dairy fermented foods (Cheese, yogurt and Indigenous dairy products India), Introduction to probiotics, prebiotics, Production and application of Baker’s Yeast, Application of microbial enzymes in Dairy industry

4. Dairy Microbiology

5. Starter Culture Starter culture means a selected strain of food-grade microorganisms of known and stable metabolic activities and other characteristics that is used to produce fermented foods of desirable appearance, body, texture, and flavor. Some starter cultures are also used to produce food additives, as probiotics and for drug delivery . This process was found to give better products than those produced through natural fermentation of the raw materials. These starters were mixtures of unknown bacteria. Processing plants started maintaining a good starter by daily transfer (mother starter) and produced product inoculum from these .

6. Bacteriological makeup of these starters (types and proportion of the desirable as well as undesirable bacteria) during successive transfers was continually susceptible to changes as a result of strain dominance among those present initially, as well as from the contaminants during handling. Some private companies started supplying mixed cultures of unknown bacterial composition for cheese manufacture both in the U.S. and in Europe. Subsequently, the individual strains were purified and examined for their characteristics, and starter cultures with pure strains were produced by these commercial companies. Initially, such starter cultures were developed to produce cheeses. Currently, starter cultures for many types of fermented dairy products, fermented meat products, some fermented vegetables, fermented baking products, for alcohol fermentation, and for other purposes (especially with genetically modified organisms, GMOs) are commercially available.

7. Fermented dairy product

8. Fermented dairy product Fermented dairy products can be broadly divided into two groups: fermented milk products and cheeses . In fermented milk products , all the constituents of the milk are retained in the final products, with the exception of those partially metabolized by the bacteria. In cheeses , a large portion of milk constituents is removed in whey to obtain the final products.

9. General method for production Raw (or Starting) Materials A large number of raw materials from plant and animal sources are used to produce fermented foods. These include milk (from cows, buffalo, sheep, goats), meat (beef, pork, lamb, goat, and fowl), fish (many types), eggs (chicken and duck), vegetables and vegetable juices, many fruits and fruit juices, cereal grains, tubers, lentils, beans and seeds. Some are used in combination

10. 2. Microorganisms Used Many desirable species and strains of bacteria, yeasts and molds are associated with fermentation of foods. Depends on single predominating species and strain Some times mixed populations were used Depend on environmental parameters such as nutrients, temperature of incubation, oxidation–reduction potential and pH.

11. 3. Fermentation Process Foods can be fermented in three different ways, based on the sources of the desirable microorganisms: Natural fermentation, Back slopping, Controlled fermentation.

12. 1. Natural Fermentation Many raw materials used in fermentation (usually not heat treated ) contain both desirable and associated microorganisms. The conditions of incubation are set to favor rapid growth of the desirable types and no or slow growth of the associated (many are undesirable) types.

13. A product produced by natural fermentation can have some desirable aroma resulting from the metabolism of the associated flora. However, because the natural microbial flora in the raw materials may not always be the same, it is difficult to produce a product with consistent characteristics over a long period of time. Also, chances of product failure because of growth of undesirable flora and foodborne diseases by the pathogens are high.

14. 2. Back Slopping In this method, some products from a successful fermentation are added to the starting materials, and conditions are set to facilitate the growth of the microorganisms coming from the previous product. This is still practiced in the production of many ethnic products in small volumes. Retention of product characteristics over a long period may be difficult because of changes in microbial types. Chances of product failure and foodborne diseases are also high.

15. 3. Controlled Fermentation The starting materials (may be heat treated) are inoculated with a high population (106 cells/ml or more) of a pure culture of single or mixed strains or species of microorganisms (starter culture). Incubation conditions are set for the optimum growth of the starter cultures. Large volumes of products can be produced with consistent and predictable characteristics each day. Generally, there is less chance of product failure and foodborne diseases

16. Microbiology of Cultured Buttermilk Fermentation It is produced from partially skim milk through controlled fermentation with starter cultures Starter (Controlled Fermentation) Lactococcus lactis ssp. lactis or Lactococcus cremoris is used for acid and Leuconostoc mesenteroides ssp. Leuconostoc cremoris for diacetyl and CO 2 .

17. Growth At 72℉, there is balanced growth of the two species, and balanced production of acid, diacetyl, and CO 2 . Above 72 ℉, the growth of Lactococcus species is favored, with more acid and less flavor; below 72 ℉, the growth of Leuconostoc species is favored, with less acid and more flavor.

18. Lactose (transported by PEP-PTS system) is hydrolyzed by b- galactosidase in Lactococcus spp.:

19. Lactococcus lactis strains should transport and hydrolyze lactose (Lac+), metabolize P-galactose by the tagatose pathway , Strains will be phage resistant, not produce slime, and not be very proteolytic. Leuconostoc species should be able to transport and utilize citrate to produce more diacetyl and less acetaldehyde and ferment lactose, Strains will be phage resistant, and not produce slime.

20. Strains should not produce inhibitory compounds (such as bacteriocins) against each other, but can have antimicrobial activity toward undesirable organisms. Through selection and genetic manipulation, strains have been developed that grow rapidly, produce desirable characteristics, and are resistant to some phages. Current information on genome sequences of Lactococcus and Leuconostoc strains and their phages will help develop better strains in the future.

21. Microbial Problems Because of too much acetaldehyde production (especially if biovar diacetylactis is used), green (yogurt flavor) may develop. A slimy texture implies contamination with bacteria that produce slime ( Alcaligenes faecalis ) or that starter cultures (some Leuconostoc lactic strains) are slime formers (exopolysaccharides). A yeasty flavor implies contamination with lactose- fermentating yeasts, and a cheesy flavor alludes to contamination with proteolytic psychrotrophs (during storage). Proteolysis by proteases of contaminants in starters can also cause development of bitter flavor, especially during storage.

22. Yoghurt Yogurt is a variety of curd. Whole, low fat, skim milks & even cream can be used to make yogurt. In production of yogurt, a mixed culture of streptococcus thermophilus, lactobacillus acidophilus is usually added to to the pasteurised milk & incubated at 42-46 ° C. Increase in folic acid concentration during fermentation. Fermented milk is useful for a wide variety of disorders like colitis, constipation, diarrhoea, gastroenteritis, diabetes & hyper cholesteremia.

23. Microbiology of Yogurt Fermentation Plain yogurt has a semisolid mass due to coagulation of milk (skim, low, or full fat) by starter-culture bacteria. It has a sharp acid taste with a flavor similar to walnuts and a smooth mouth feel. The flavor is due to the combined effects of acetaldehyde, lactate, diacetyl, and acetate, but 90% of the flavor is due to acetaldehyde. Many types of yogurt are available in the market, e.g., plain yogurt, fruit yogurt, flavored and colored yogurt, blended yogurt, sweetened yogurt, heated yogurt, frozen yogurt, dried yogurt, low-lactose yogurt and carbonated yogurt.

24. Starters (Controlled Fermentation) Frozen concentrates or direct set starters can be used. Normally, Lactobacillus delbrueckii ssp., Lactobacillus bulgaricus and Streptococcus thermophilus are used. Some processors also combine these two with other species, such as Lactobacillus acidophilus and Bifidobacterium spp., Lactobacillus rhamnosus , or Lactobacillus casei . However , in general, they do not compete well in growth with the two yogurt starters. Therefore , they are added in high numbers after fermentation and before packaging. They may not survive well when present in yogurt with the regular yogurt starter cultures.

25. Growth For balanced growth of the two species, the fermentation is conducted at 110℉ (43.3℃). At this temperature, both acid and flavor compounds are produced at the desired level. If the temperature is raised above 110℉, the Lactobacillus sp. predominates, causing more acid and less flavor production; at temperatures below 110℉, growth of Streptococcus sp. is favored, forming a product containing less acid and more flavor.

26. Biochemistry In Lactose metabolism both species have a constitutive b-galactosidase system, and lactose (transported by permease systems) is hydrolyzed to glucose and galactose. Both species are homofermentative and produce lactate from glucose by the EMP pathway. Lactobacillus delbrueckii ssp. or Lactobacillus bulgaricus strains have enzymes for the Leloir pathway to metabolize galactose, but while actively metabolizing glucose they do not utilize galactose well. Most Streptococuss thermophilus strains do not have the enzymes of the Leloir pathway (or have a very weak system) and thus do not metabolize galactose. As a result, galactose is excreted outside, causing its accumulation in yogurt.

27. Phage Resistance. Both species have phages; resistant strains need to be developed and used. Symbiotic and Synergistic Relationship. Strain selection for best combinations is necessary. Antagonistic Effect. Strains should not produce inhibitory compounds (such as bacteriocins) against each other. Good Survival to Freezing and Drying. Possible genetic basis needs to be studied to develop resistant strains to produce concentrated starter cultures.

28. Yogurt as probiotic food Y ogurt i s b asical l y a p r obiotic f ood w i t h l i v e a n d active cultures. It contains different kinds of bacteria that are believed to be beneficial to your overall health. Four major strains of bacteria to look for: Lactobacillus acidophilus, Lactobacillus bulgaricus , Streptococcus thermophilus , and Bifidobacteria

29. YOGURT Nutrifacts- Y ogurt i s ric h i n p o tassium, c al c ium, p r o t ein and B vitamins, including B-12 Yogurt is easier to digest than milk Y ogurt c ontribu t es t o c ol o n health Y o g h u r t s t r engthens and s t abil iz es the i m mune system R esea r c h s h o w s w omen w h o eat 4 cup s of yoghurt/week have less vaginal and bladder infections Th e lacti c acid of y o g h u r t i s a per f e c t medi u m to maximize calcium absorption Y ogurt ca n be u s ed a s a n e f f e c t i v e douche

30. Yogurt - A rich source of calcium An 225g serving of most yogurts provides 450 mg. of calcium, one-half of a child's RDA and 30 to 40 percent of th e adult R D A f or calcium . Because the live-active cultures in yogurt increase the absorption of calcium, an 225g serving of yogurt gets more calcium into the body than the same volume of milk can.

31. Cholesterol control Although cholesterol is important and necessary for human health, high levels of cholesterol in the blood have been linked to damage to arteries and cardiovascular disease. Major dietary sources of cholesterol include cheese, egg yolks, beef, pork, poultry, fish, and shrimp. Cholesterol contributes to atherosclerosis - a condition that greatly increases the risk of heart attack and stroke - by suppressing the activity of a key protein that protects the heart and blood vessels

32. Yoghurt as Cholesterol Reducer Yogurt contains a factor that inhibits the synthesis of cholesterol from acetate. This factor may be either 3-hydroxy-3-methylglutaric acid

33. Dairy fermented foods -Cheese There are many types of cheeses, all require the formation of a curd, which can be separated from the main liquid fraction, or whey. The curd is made up of a protein, casein, and is usually formed by the action of an enzyme, rennin (or chymosin), which is aided by acidic conditions provided by certain lactic acid- producing bacteria. These inoculated lactic acid bacteria also provide the characteristic flavors and aromas of fermented dairy products during the ripening process. The curd undergoes a microbial ripening process, except for a few unripened cheeses, such as ricotta and cottage cheese.

34. Cheeses are generally classified by their hardness, which is produced in the ripening process. The more moisture lost from the curd and the more the curd is compressed, the harder the cheese. Romano and Parmesan cheeses, for example, are classified as very hard cheeses ; cheddar and Swiss are hard cheeses . Limburger, blue, and roquefort cheeses are classified as semisoft ; Camembert is an example of a soft cheese.

35. The hard cheddar and Swiss cheeses are ripened by lactic acid bacteria growing anaerobically in the interior. A Propionibacterium species produces carbon dioxide, which forms the holes in Swiss cheese. Blue and roquefort cheeses are ripened by Penicillium molds inoculated into the cheese. The texture of the cheese is loose enough that adequate oxygen can reach the aerobic molds. The growth of the Penicillillm molds is visible as blue-green clumps in the cheese.

36. Cheese is made up of casein. Varieties of cheese are differentiated according to their Flavour Texture Type of milk CH EE SE H a r d Bac t er i al r i pen i ng Ch e s h i r e ; cheddar Mould r i pen i ng St i l t on Se mi h a r d Bac t er i al r i pen i ng G ouda Edam Mould r i pen i ng R o que f o r t Soft Bac t er i al r i pen i ng L i mbe r g er Mould r i pen i ng Camembert Unripened C o t t a g e cheese Salts & seasoning added Type of bacteria & mould species used in ripening Manufacturing & processing method

37. Production of cheese Maturation, curing ripening & ageing Pressing & moulding Milling & salting Cheddaring curd cutting & pilling Curd formation Pasteurised milk Curd formation: pasteurised whole milk is brought to a temperature of 31’C, starter & required colo u ri n g m a t t e r is ad d ed. A f t e r 30 m in r en n in is added, stirred & allowed to set curd. Curd cutting: into small cubes Curd cooking: heated to 38 ° C & held for 45 min. curd is stirred to prevent matting. Curd drainage: whey is drained off & curd is allowed to mat. Cheddaring: cutting matted curd into blocks turning them at 15 min interval & then piling. It is then passed to curd mill which cuts the slab into strips. Salting the curd: to draw out the whey from curd & as preservative. Pressing : overnigh t

38. Examples of cheese, the microbes involved and the category they can be placed CHEESE MICROORGANISMS SOFT, UN R IP E NED Cottage Lactococcus lactis Leuconostoc citrovorum Cream Streptococcus cremoris Neufchatel Streptococcus diacetilactis SOFT, RIPENED 1 – 5 MONTHS Brie Lactococcus lactis Penicillium candidium Streptococcus cremoris Penicillium camemberti Brevibacterium linens Camembert Lactococcus lactis Streptococcus cremoris Penicillium candidium Penicillium camembert Limburger Lactococcus lactis Brevibacterium linens Streptococcus cremoris

39. CHEESE MICROORGANISMS CHEESE SEMISOFT, RIPENED 1 – 12 MONTHS Blue Lactococcus lactis Penicillium roqueforti Streptococcus cremoris Penicillium glaucum Brick Lactococcus lactis Brevibacterium linens Streptococcus cremoris Gorgonzola Lactococcus lactis Penicillium roqueforti Streptococcus cremoris Penicillium glaucum Monterey Lactococcus lactis Streptococcus cremoris Meunster Lactococcus lactis Brevibacterium linens Streptococcus cremoris Roquefort Lactococcus lactis Penicillium roqueforti Streptococcus cremoris Penicillium glaucum

40. CHEESE MICROORGANISMS HARD, R IPENED 3 – 12 MONTHS Edam Lactococcus lactis, Streptococcus cremoris Gruyere Lactococcus lactis Lactobacillus helveticus Streptococcus thermophilus Propionibacterium sheranii or Lactobacillus bulgaricus and Propionibacterium freudenreichii Swiss Lactococcus lactis Lactobacillus helveticus Propionibacterium shermanii or Lactobacillus bulgaricus and Streptococcus thermophilus VERY HARD, RIPENED 12 – 16 MONTHS Parmesan Lactococcus lactis Lactobacillus bulgaricus Streptococcus cremoris Streptococcus thermophilus

41. Secondary Microbes Large holes: Propioni bacterium freudenreichii subsp. Shermaniee White moulds: Penicillium camembertii, P. caseiocolum and P. candidum Blue/green moulds: Penicillium roqueforti, P. glaucum Ripening adjuncts: Bacterial or yeast cultures added in addition to the regular LAB cultures Attenuated cultures which are not intended to grow but only to contribute their enzymes.

42. Species Major Known Function Product Propi o ni b acte r i u m shermanii Flavour and Eye formation Swiss cheese family Lactobacillus bugaricus Lactobacillus lactis Lactobacillus helveticus Acid and flavour Yoghurt, Swiss, Emmental, and Italian cheeses Lacto b acil l us acidophilus Acid Acidophilus buttermilk S t r e p t oc o ccus thermophilus Acid Emmental, Cheddar, and Italian cheeses, and yogurt Streptococcus durans Streptococcus faecalis Acid and flavour Soft Italian, cheddar, and some Swiss cheeses. Leuconostoc citrovorum Leuconostoc dextranicum Flavour Cultured buttermilk,, cottage cheese, and starter cultures. Some microbes involved in cheesemaking

43. Contd.. Ripening: 60 days to 12 months depending on the flavour required under controlled conditions of temperature & humidity. Changes from a bland tough rubbery mass to a full flavoured soft product. Rennin splits protein into peptones & peptides. Increases the B-vitamins & improves cooking quality. Cheese has limited keeping quality & requires refrigeration, should be kept cold & dry i.e., wrapped in wax paper or metal foil.

44. Health Benefits of Cheese Chees e c o n ta i n s a l ot s of n ut r i e nt s li k e calcium , p r o t ei n, phosphorus, zinc, vitamin A and vitamin B12. Calcium is one of the important nutrients most likely to be lacking in the American diet. The high-quality protein in cheese provides the body with essential building blocks for strong muscles. If you are lactose intolerant, many cheeses, particularly a g ed cheese s such as Chedda r and S wis s , c o n ta i n li t tl e or no lactose and are often well tolerated.

45. Probiotics Probiotics which are also known as friendly bacteria or good bacteria can be defined as living microorganisms that are beneficial to the health of their host .

46. Mechanism of action of Probiotics Their positive effect is used for the restoration of natural microbiota after antibiotic therapy. Therefore, probiotics may effectively inhibit the development of pathogenic bacteria, such as Clostridium perfringens , Campylobacter jejuni , Salmonella enteritidis , Escherichia coli , various species of Shigella, Staphylococcus, and Yersinia , thus preventing food poisoning. A positive effect of probiotics on digestion processes, treatment of food allergies, candidosis and dental caries has been confirmed.

47. Probiotic Microorganisms

48. Probiotic microorganisms such as Lactobacillus plantarum , Lactobacillus reuteri , Bifidobacterium adolescentis , and Bifidobacterium pseudocatenulatum are natural producers of B group vitamins (B1, B2, B3, B6, B8, B9, B12). They also increase the efficiency of the immunological system, enhance the absorption of vitamins and mineral compounds, and stimulate the generation of organic acids and amino acids . Probiotic microorganisms may also be able to produce enzymes, such as esterase, lipase and co-enzymes A, Q, NAD, and NADP . Some products of probiotics’ metabolism may also show antibiotic ( acidophiline , bacitracin, lactacin ), anti-cancerogenic, and immunosuppressive properties

49. Molecular and genetic studies allowed the determination of the basics of the beneficial effect of probiotics, involving four mechanisms: ( 1)Antagonism through the production of antimicrobial substances ( 2)Competition with pathogens for adhesion to the epithelium and for nutrients ( 3) Immunomodulation of the host; ( 4) Inhibition of bacterial toxin production .

50. Prebiotics Different prebiotics will stimulate the growth of different indigenous gut bacteria . Prebiotics have enormous potential for modifying the gut microbiota, but these modifications occur at the level of individual strains and species and are not easily predicted priorly . Furthermore, the gut environment, especially pH, plays a key role in determining the outcome of interspecies competition.

51. Both for reasons of efficacy and of safety, the development of prebiotics intended to benefit human health has to take account of the highly individual species profiles . Fruit, vegetables, cereals, and other edible plants are sources of carbohydrates constituting potential prebiotics. The following may be mentioned as such potential souces : Tomatoes, artichokes, bananas, asparagus, berries, garlic, onions, green vegetables, legumes, as well as oats, barley, and wheat .

52. Some artificially produced prebiotics are, among others: lactulose , galacto oligosaccharides, fructo oligosaccharides, malto oligosaccharides, cyclodextrins, and lactosaccharose .. Fructans , such as inulin and oligofructose, are believed to be the most used and effective in relation to many species of probiotics

53. Mechanism of Action of Prebiotics Prebiotics are present in natural products, but they may also be added to food . The purpose of these additions is to improve their nutritional and health value. Some examples are: inulin, fructo oligosaccharides, lactulose and derivatives of galactose and β-glucans . Those substances may serve as a medium for probiotics. Prebiotics are not digested by host enzymes and reach the colon in a practically unaltered form , where they are fermented by saccharolytic bacteria (e.g., Bifidobacterium genus). The consumption of prebiotics largely affects the composition of the intestinal microbiota and its metabolic activity. This is due to the modulation of lipid metabolism, enhanced absorbability of calcium, effect on the immunological system, and modification of the bowel function.

54. Acidophilus Milk Acidophilus milk, also known as sweet acidophilus milk or probiotic milk. Milk that has been fortified with Lactobacillus acidophilus or other friendly bacteria cultures such as Lactobacillus bulgaricus , Bifidobacterium bifidum , or Streptococcus theromphilus .

55. Lactose intolerance Lactose intolerance , also called lactase deficiency and hypolactasia , is the inability to digest lactose ,a sugar found in milk and some dairy products . Lactose intolerant individuals have insufficient levels of lactase — the enzyme that metabolizes lactose—in their digestive system SYMPTOMS: Abdominal bloating and cramps, flatulence, diarrhea , nausea, borborygmi (rumbling stomach) and/or vomiting after consuming significant amounts of lactose.

56. Application of microbial enzymes in Dairy industry Enzymes produced by microbial sources are biological molecules that known to catalyze biochemical reactions which lead to stimulate the necessary chemical reactions, as well as to the formation of fermented products. Microbial protease, lipase and β-galactosidase are important examples of such interest in industrial food and dairy product.

57. Protease Proteases (mixture of peptidases and proteinases) also known as hydrolytic enzymes, peptidases and proteolytic enzymes . They are one of the largest group of enzymes in biotechnology and most important enzyme which produced on a large scale, nearby 60% of the world enzyme market . This enzyme that catalyze the hydrolysis of protein into amino acid or smaller peptide fractions, which depends upon the optimum pH. They are defined as alkaline, neutral or acidic proteases.

58. Microbial proteases are classified as exopeptidases and endopeptidases on basis of site of protein action which recognized into different families included : Serine carboxy proteases (EC 3.4.16), Metallo carboxy proteases (EC 3.4.17), Serine proteases (EC 3.4.21) family includes trypsin , chymotrypsin, elastase . Cysteine proteases (EC 3.4.22), Aspartic proteases (EC 3.4.23) which have two aspartic acid residues in the catalytic of the active site.

59. Microbial rennin is also one of the most significant enzymes, produced by GRAS microorganisms like Mucor pusilis , Mucor miehei and Bacillus subtilis . It has been used instead of calf's rennin in cheese manufacture . Thus, this enzyme has a low proteolytic activity and high milk-clotting activity.

60. Most of the commercial protease produced from bacteria viz. Bacillus that is the major source . It is one of the most important industrial enzymes in the world markets. The major application is recognized in dairy industry for cheese ripening, hydrolyzing whey protein and flavor development . Moreover, enzyme used to debittering of protein hydrolysates , synthesis of aspartame and accelerating cheese ripening times. Furthermore, proteases were also used for the production of milk proteins with low allergenic activity , which used as an ingredients in milk formulas of baby milk powder.

61. Lipase Lipase (EC 3.1.1.3) is also called as glycerol ester hydrolases, a lipolytic enzyme. Lipases are the key enzymes involved in fat digestion, catalyze the triacylglycerols reaction to fatty acids and glycerol, mono or di-glycerides and extracellular enzyme . They are mainly produced from fungi when induced by adding oils and fats . Microbial lipases constitute as an important group of biotechnologically valuable enzymes. Nowadays, bacterial lipases are receiving attention due to itʼs function in extreme conditions

62. Generally, commercial source of microbial lipase including fungi such as Aspergillus, Mucor, Rizopus and Candida while Pseudomonas , Achromobacter , Staphylococcus and Bacillus reported as bacterial lipases producers. Most of the researches indicated lipase application in dairy industry. For acceleration cheese ripening, hydrolysis of milk fat, development of lipolytic flavours in some cheese ripening which produces a wide range of compounds by primary and secondary biochemical pathways . Moreover, the lipolysis of fat in butter, margarine and cream.

63. β- galactosidase β-galactosidase (EC 3.2.1.23) is another name lactase, Lactosase and Lactosidase enzymes are classified in hydrolases class belongs to family 35 of the glycoside hydrolases (GH- 35). This enzyme is located in the border membrane of the small intestine of humans and other mammals , which responsible to hydrolyze the glycosidic bond of ß, (1-4) in lactose and produce glucose and galactose. This disaccharide is present in mammalian in concentrations up to 10% (w/w) and foremost sugar present in dairy products. Also, has an ability to catalyze the reverse reaction of the hydrolysis called as transglycosylation .

64. The main function of the β-galactosidase is to hydrolyze lactose into glucose and galactose . The β-galactosidase could reduce the crystallization problem during storage due to low dissolvability of lactose . Developed to a biosensor to apply for the quantitative detection of lactose in commercial milk samples from two enzymatic activities; one of them is glucose oxidase and second is β- galactosidase .

65. Whey lactose hydrolysis has a number of beneficial uses, which is characterized by high in sweet. So , it is a source of "sugars which can be used in the manufacture of sweets and syrup as an alternative to sucrose used for bread and pastry, and also in ice cream. Moreover, Saccharomyces cerevisae can ferment to the whey (contain lactose hydrolase ) as a carbon source for production of alcohol and other a wide range of the bio products. β- galactosidase is one of the most popular enzyme in the dairy industry, which works on the Lactose hydrolysis either from milk to glucose and galactose.

66. Many characteristics and qualities of the dairy products were improved such as solubility, flavor, sweetness, digestibility, problem of crystallization, resulting a sandy or gritty texture and mealy (in ice cream, condensed milk and frozen milks) was decreased while increasing of nutritional value by adding galacto oligosaccharides . β- galactosidase could employed to converts the whey lactose into the useful products such as sweet syrups that are used in soft drink, confectionery and bakery industry .

67. On the other hand, milk lactose hydrolyze with β- galactosidase was also used in the various dairy products such as yoghurt, processed cheese and some other products . They are enzymatically obtained which is considered as a substrate that is selectively utilized by probiotic bacteria conferring to the health benefit with the reduction of a significant number of potential pathogenic bacteria .