Milk, Fermentation, and Dairy Products PDF

MILK, FERMENTATION, FERMENTED AND NON- FERMENTED DAIRY PRODUCTS FERMENTATION In addition to being made more shelf stable, all fermented foods have aroma and flavor characteristics that result directly or indirectly from the fermenting organisms. In some instances, the vitamin content of the...

MILK, FERMENTATION, FERMENTED AND NON- FERMENTED DAIRY PRODUCTS FERMENTATION In addition to being made more shelf stable, all fermented foods have aroma and flavor characteristics that result directly or indirectly from the fermenting organisms. In some instances, the vitamin content of the fermented food is increased along with an increased digestibility of the raw materials. Lactobacillus bacteria convert sugars naturally present in fruit or vegetables into lactic acid. Lactic acid is a natural preservative that helps fight bad bacteria and preserves not only the flavor and texture of food but also its nutrients as Lb. brevis, Lactobacillus fermentum, Lb. buchneri, Lactobacillus kefiri, Lactobacillus rhamnosus, Lactobacillus curvatus, Lb. Bongkrekic acid is a little-known toxin and source of food poisoning that is produced by the bacterium Burkholderia gladioli. coconut- based fermented product that is popular in Southeast Asia – this is how the toxin got its name. Besides fermented coconut and corn based products, B. cocovenenans may also be found in snow fungus and black fungus. Tempe bongkrek, a traditional fermented presscake produced in Indonesia, has been responsible for thousands of cases of bongkrekic acid poisoning, many of which were fatal.  The word fermentation has had many shades of meaning in the past. According to one dictionary definition, it is “a process of chemical change with effervescence... a state of agitation or unrest... any of various transformations of organic substances.” The word came into use before Pasteur’s studies on wines  DAIRY PRODUCTS Milk Milk is used throughout the world as a human food in at least one form, and from at least one of a number of different mammals  Composition The protein content of milk is considerably lower (3.5 vs. 18.0%) while the carbohydrate content is considerably higher (14.9 vs. ca. 1.0%). Milk protein consists mainly of 80-85% casein, and it exists in several classes: α, β, etc. If milk pH falls below 4.6, the casein precipitates. When precipitation occurs, the liquid portion is referred to as whey. 65% protein (Lou et al., 2016) Zhang et al., 2021  The pH of fresh whole milk is around 6.6 but it may reach ca. 6.8 from a cow that has mastitis. Mastitis is an infection of the udder that is most often caused by Streptococcus agalactiae and S. uberis but sometimes by Staphylococcus aureus or Streptococcus dysgalactiae. Fresh milk from a mastitic cow typically contains leucocytes (white blood cells) >106/ml in contrast to non-mastitic milk that contains leucocytes around 70,000/ml. NOTES FROM PREV. SLIDE Milk contains a very adequate supply of B vitamins with pantothenic acid and riboflavin being the two most abundant. Vitamins A and D are added for human consumption, and their presence has no known effect on the activity of microorganisms. Overall, the chemical composition of whole cow’s milk makes it an ideal growth medium for heterotrophic microorganisms, including the nutritionally fastidious Gram-positive lactic acid bacteria. PROCESSING  PASTEURIZATION The objective of milk pasteurization is the destruction of all disease- causing microorganisms. Endospores of pathogens such as Clostridium botulinum and spoilage organisms such as Clostridium tyrobutyricum, C. sporogenes, or Bacillus cereus are not destroyed.  NOTES FROM PREV. SLIDE spores are extremely resistant to heat, dehydration, and chemical or physical stresses. Typical treatments used in the food industry, including heat treatments, can inactivate vegetative cells but fail to kill spores. The resilience of an endospore can be explained in part by its unique cellular structure. The outer proteinaceous coat surrounding the spore provides much of the chemical and enzymatic resistance. Beneath the coat resides a very thick layer of specialized peptidoglycan called the cortex.  METHODS OF PASTEURIZATION Low temperature-long time (LTLT) (batch method) - consists of heating the coolest part to 145◦F (63◦C) for 30 minutes. High temperature-short time (HTST) (flash method) - consists of heating to 161◦F (72◦C) for 15 seconds which is less destructive than the batch method. Basis for the heating time and temperature is the thermal death time (TDT) of the most heat-resistant non-spore forming milk-borne pathogens. NOTES: The low-temperature pasteurization process enables the killing of all pathogenic microbes, and the high-temperature pasteurization process causes the killing of vegetative pathogenic and spoilage bacteria (Milk pasteurization, 2017). It also causes denaturation of serum proteins.  UHT (ultra-high temperature) is another thermal treatment that destroys non-spore forming pathogens in milk, but in addition some spore formers are severally reduced in numbers. The UHT treatment is achieved by heating at temperatures of 275–284◦F (135–140◦C) for a few sec (the minimum treatment is 130◦C for 1 sec). UHT-treated milk is commercially sterile with a shelf life of 40–45 days at 40◦F when aseptically packaged in sterile. NOTES: UHT Technology. Used for the sterilization of low acid foods, UHT treatment involves heating the product to over 135 °C. It destroys all microorganisms, making the end product suitable for ambient distribution.  General Microbiota of Milk Theoretically, milk that is secreted to the udder of a healthy cow should be free of microorganisms. However, freshly drawn milk is generally not free of microorganisms.  Milk-Borne Pathogens Brucellosis Anthrax Tuberculosis Listeriosis Salmonellosis Q fever Campylobacteriosis Crohn’s disease (?) Enterohemorrhagic colitis Staph./Strep. Mastitis  Spoilage As the only natural source of the disaccharide lactose, milk undergoes microbial spoilage in a way that is unique. Only a relatively small number of milk-borne bacteria can obtain energy from this sugar (especially at refrigerator temperatures) in contrast to the disaccharides sucrose and maltose, and the lactic acid bacteria are well suited to this task. spoilage of UHT milk is caused by Bacillus spp. that survive the UHT process. Anaerobic spores appear not to be a problem because of the relatively high Oxidation–reduction potential Eh of milk. Bacillus species: B. cereus, B. licheniformis, B. badius, and B. sporothermodurans. Paenibacillus spp. have been isolated also from UHT-treated products.  PROBIOTICS AND PREBIOTICS PROBIOTICS - it is a consumable product that contains live organisms that are or are believed to be beneficial to the consumer. ABIOTIC – absence of viable organisms. Yogurt is the most consumed probiotic dated because of its presumed health benefits.  The typical starter cultures for yogurt are Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, some preparations are made by the addition of bifidobacteria.  PREBIOTICS are not microorganisms; they are substrates for the indigenous probiotic-type bacteria that reside in the colon. These substrates are non digestible as they pass through the small intestine, and they consist of oligosaccharides such as fructooligosaccharides of which inulin is an example. They are metabolized by the bidifobacteria and the anaerobic lactobacilli (both of which are indigenous to the colon) where the oxidation reduction favors their growth and activity, which results in an environment that is antagonistic to aerobic pathogens.  Lactose Intolerance (lactose malabsorption, intestinal hypolactemia) is the normal state for adult mammals, including most adult humans, and many more groups are intolerant to lactose than are tolerant. When lactose malabsorbers consume certain quantities of milk or ice cream, they immediately experience flatulence and diarrhea. The condition is due to the absence or reduced amounts of intestinal lactase, and this allows the bacteria in the colon to utilize lactose with the production of gases  STARTER CULTURES, FERMENTED PRODUCTS A lactic starter is a basic starter culture with widespread use in the dairy industry. For cheese making of all kinds, lactic acid production is essential, and the lactic starter is employed for this purpose. Lactic starters are also used for preparing butter, cultured buttermilk, cottage cheese, and cultured sour cream and are often referred to by product (butter starter, buttermilk starter, and so on).  LACTIC STARTERS L. lactis subsp. lactis, L. lactis subsp. cremoris, L. lactis subsp. lactis biovar diacetylactis. Where flavor and aroma compounds such as diacetyl are desired, the lactic starter will include a heterolactic such as: Leuconostoc mesenteroides subsp. cremoris, L. lactis subsp. lactis biovar diacetylactis, or Leuconostoc mesenteroides subsp. dextranicum Fermented Products  In the case of butter, where cream is inoculated, the acidified cream is then churned to yield butter, which is washed, salted, and packaged. Buttermilk, as the name suggests, is the milk that remains after cream is churned for the production of butter. Cultured sour cream is produced generally by fermenting pasteurized and homogenized light cream with a lactic starter. Yogurt The coccus grows faster than the rod and is primarily responsible for initial acid production at a higher rate than that produced by either when growing alone. The coccus can produce about 0.5% lactic acid and the rod about 0.6–0.8% (pH of 4.2 4.5). However, if incubation is extended, pH can decrease to about 3.5 with lactic acid increasing to about 2%. Yogurt (yoghurt) is produced with a yogurt starter, which is a mixed culture of S. salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in a 1:1 ratio. The coccus grows faster than the rod and is primarily responsible for initial acid production at a higher rate than that produced by either when growing alone. The coccus can produce about 0.5% lactic acid and the rod about 0.6–0.8% (pH of 4.2 4.5). However, if incubation is extended, pH can decrease to about 3.5 with lactic acid increasing to about 2%. S. salivarius subsp. thermophilus Lactobacillus delbrueckii subsp. bulgaricus  DISEASES CAUSED BY LACTIC ACID BACTERIA Although the beneficial aspects of the lactic acid bacteria to human and animal health are unquestioned, some of these bacteria are associated with human illness. Nosocomial (hospital acquired) infections