HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION FACULTY OF CHEMICAL AND FOOD TECHNOLOGY SUBJECT DAIRY AND RELATED DAIRY PRODUCTION TOPIC 01 LIQUID MILK Instructor PhD Phạm Thị Hoàn Group 01 1.
HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION FACULTY OF CHEMICAL AND FOOD TECHNOLOGY SUBJECT: DAIRY AND RELATED DAIRY PRODUCTION TOPIC 01: LIQUID MILK Instructor: PhD Phạm Thị Hoàn Group: 01 Nguyễn Trần Hoàng Anh Nguyễn Vũ Đức Hoài Trần Kiều Hương Trần Tiểu Phụng Nguyễn Hoàng Hồng Thắm Phan Nguyên Thanh Trúc Nguyễn Ngọc Lâm Vy HO CHI MINH CITY, OCTOBER 2021 19116012 19116052 18116020 19116053 19116049 17116040 19116039 MEMBER’S WORK Nguyễn Trần Hoàng Anh 2.2.1; 2.2.5 Completed or not Completed Nguyễn Vũ Đức Hoài 2.2.2.; 2.2.4 Completed Trần Kiều Hương Completed Trần Tiểu Phụng Nguyễn Hoàng Hồng Thắm (Leader) Phan Nguyên Thanh Trúc 2.1.3; 2.1.4 Completed 1.1, 4.2 Completed Nguyễn Ngọc Lâm Vy 1.2, 4.1 Completed Member’s name Work 2.1.1; 2.1.2 Completed Contents INTRODUCTION 1.1 Definition 1.2 Classification PROCESSES 2.1 Pasteurized milk 2.1.1 Manufacture 2.1.2 Changes During Pasteurisation 2.1.3 Shelf life 2.1.4 Criteria 10 2.2 Sterilized milk 11 2.2.1 Manufacture 11 2.2.2 Change during sterilization 13 2.2.4 Product quality criteria (TCVN 7028:2009) 14 2.2.5 Shelf life 15 MACHINES 15 3.1 Microfiltration membrane 15 3.2 Centrifugal Separator 15 3.3 Plate Heat Exchanger 16 3.4 Homogenizer 16 ORIENTATION AND ALTERNATIVE CHOICES OF PRODUCT 17 4.1 Vietnam 17 4.1.1 Market analysis 17 4.1.2 Alternative choices of product 18 4.2 World 19 4.2.1 Market analysis 19 4.2.2 Challenges and alternative choices 19 REFERENCES INTRODUCTION 1.1 Definition Liquid milk is the most commonly consumed, processed, and commercialized dairy product (FAO, 2015) [1] Liquid milk can be delivered to the consumer after various heat treatments: pasteurized or sterilized, and either packaged or not (although sterilized milk is, of course, always packaged) Raw milk that has not been pasteurized so it is not liquid milk Although raw milk has the best nutritional content compared to other types of milk that have been processed, the risk of exposure to pathogenic bacteria like Salmonella spp, Mycobacterium paratuberculosis and others in raw milk far outweighs such potential benefits The nutritive value of pasteurized and UHT-sterilized milk in the heat treatment and during storage changes less than in in-bottle sterilized milk The importance in liquid milk are the decrease of available lysine and the total or partial loss of some vitamins Some data are given in Table Table Approximate Loss (in %) of Some Nutrients in Milk during Heating and Storage Treatment Available Lysine Vitamin B1 Vitamin B1 Vitamin (Thiamin) (Thiamin) B9 (Folic Acid) 5–10 0–5 3–5 5–15 5–10 10–20 a,b a 10–20 20–50 30–100b Vitamin B12 Vitamin C Pasteurization 3–10 5–20 UHT sterilization, directly 10–20 10–20 b UHT sterilization, after 20–50 30–100b c months storage In-bottle sterilization 5-10 20–40 10–20 30–50 30–60 30–60 a b c Dependent on exposure to light Dependent on O2 concentration At about 25°C The properties of liquid milk that require the most attention are safety to the consumer, shelf life, and flavor Safety is essential, milk must be pasteurized to kill pathogens for safe consumption In addition, products need to be packed carefully to avoid health hazards Flavor is an important evaluation criterion of dairy products Low-intensity pasteurization is generally preferred because most consumers dislike a cooked flavor Sterilized milk normally contains a stronger cooked flavor than pasteurized milk However, the sensitivity to cooked flavor varies considerably from one group of people to another Burton (1988) [2] stated that some people prefer a strongly heated flavor in milk, perhaps because they have traditionally drunk boiled or in-container sterilized milk Moreover, sterilized milk is used primarily in coffee or tea, in cooking, in baking where the absence of a cooked flavor is mostly not essential and shelf life may be the most important quality mark 1.2 Classification Types of milk liquid: Pasteurized milk is raw milk that has been heated to a specified temperature and time to kill pathogens that may be found in the raw milk Raw milk includes milk from cows, goats, sheep and other dairy animals [3] Sterilized milk may be defined as (homogenized) milk which has been heated to a temperature of 100 degree Celsius or above for such lengths of time that it remain fit for human consumption for at least days at room temperatures Commercially sterilized milk is rarely sterile in the strict bacteriological sense [4] Skimmed milk is essentially prepared from the milk from where all the fat content from the milk has been removed mechanically The milk fat percentages are 0.5% and solid non-fat content is 8.7% Fortified milk is cow's milk that contains extra vitamins and minerals that are not naturally found in milk in significant amounts Typically, vitamins D and A are added to milk sold in the United States However, milk can be fortified with various other nutrients, including zinc, iron, and folic acid [5] Standardized milk means cow milk or buffalo milk or sheep milk or goat milk or a combination of any of these milk that has been standardized to fat and solids-not-fat percentage given in the table below in 1.0 by the adjustment of milk solids Standardized milk shall be pasteurized and shall show a negative Phosphatase Test [6] Reconstituted milk: this product is made by dissolving whole milk power in water to obtain a liquid similar to its composition Recombined milk: This product is made by mixing skimmed milk powder in water, then adding liquid milk fat It is similar to homogenized whole Milk, except that it lacks most of the material of the natural fat globule membrane, such as phospholipids Filled milk: It is like recombined milk, except that instead of milk fat, a vegetable oil is used to provide the desired fat content Toned milk: It is a mixture of buffaloes’ milk and reconstituted skim milk The high fat content of buffaloes’ milk is thereby toned down Human milk: milk produced by a woman's breasts after childbirth as food for her child PROCESSES 2.1 Pasteurized milk Removing harmful bacteria in milk is essential for food safety [7] Pasteurization is therefore the critical step for processing the raw milk Pasteurization is now mostly performed as a continuous process, which is known as the high‐temperature, short‐time (HTST) process [8] The description of pasteurization given by the IDF (1986) remains very appropriate: “a process applied with the aim of avoiding public health hazards arising from pathogenic microorganisms associated with milk, by heat treatment which is consistent with minimal chemical, physical and organoleptic changes in the product” [9] Today, pasteurization is used widely in the dairy industry and other food processing industries to to eliminate pathogens and extend shelf life, to achieve food preservation and food safety In addition, prevention of cross-contamination before, during and after pasteurization is extremely important for ensuring the safety of the processed milk products 2.1.1 Manufacture Thermalization: [7], [9], [10] Several approaches enable control of the microbial quality of bulk raw milk during its storage The simplest is to lower the storage temperature; a decrease from to 2°C causes substantial retardation of the growth of psychrotrophs up to the critical value of 106 cfu/mL for days (Griffiths et al., 1987) To avoid the undesirable growth of psychrotrophs, which can be in excess of × 105 cfu/mL after days of refrigerated storage, a moderate heat treatment (57–68°C for >15s) called thermalization followed by cooling at 4°C is applied Thermalization kills nearly all psychrotrophs and many lactic acid bacteria, extending the cold storage period of raw milk to days before processing However, during the cold storage period endogenous milk enzymes are generally active This is especially true for lipoprotein lipase, which can hydrolyze the triglycerides of fat globules when the milk fat globule membrane (MFGM) is damaged by temperature fluctuations or by agitation and foaming The induced lipolysis in milk results in rancidity Actually, lipoprotein lipase activity is only a problem in raw milk, because it is almost totally inactivated by pasteurization Its potential activity in raw milk is enough to produce rancid flavours in less than 10 Nevertheless, the activity of the enzyme decreases slowly in raw milk kept under refrigeration and provided that the milk triglycerides are protected by an intact MFGM, its action is controlled (Olivecrona et al., 2003; Walstra et al., 2006) Furthermore, thermalization at a rather high temperature (say 20 s at 67.5°C) causes a considerable inactivation of milk lipase (about 50%) and permits a somewhat lower pasteurization temperature in the manufacture of homogenized milk Despite these obvious advantages of thermalization, dairy plants often only cool the milk (mainly to save on costs), taking the risk of some growth of psychrotrophs Figure Example of the manufacture of homogenized, pasteurized beverage milk Separation: [7] [11] In dairy industry, the process of separating milk into cream and skim milk is known as separation Most modern plants use a separator to control the fat content of various products A separator is a highspeed centrifuge that acts on the principle that cream or butterfat is lighter than other components in milk Centrifugation causes the skim, which is denser than cream, to collect at the outer wall of the bowl The lighter part (cream) is forced to the centre and piped off for appropriate use An additional benefit of the separator is that it also acts as a clarifier Particles even heavier than the skim, such as sediment, somatic cells, and some bacteria, are thrown to the outside and collected in pockets on the side of the separator This material, known as “separator sludge,” is discharged periodically and sometimes automatically when buildup is sensed If homogenization is omitted, only a part of the milk will be skimmed, while the skim milk volume obtained should suffice to standardize the milk Current standards generally set whole milk at 3.25% fat, low-fat at or 2%, and skim at less than 0.5% (Most skim milk is actually less than 0.01% fat.) Homogenization: [7] [9] [11] Milk is homogenized to prevent fat globules from floating to the top and forming a cream layer or cream plug Homogenizers are simply heavy-duty, high-pressure pumps equipped with a special valve at the discharge end They are designed to break up fat globules from their normal size of up to 18 micrometres to less than micrometres in diameter A loose cream layer of agglutinated fat globules occurs in low-pasteurized milk (alkaline phosphatase merely inactivated), which can be easily redispersed throughout the milk The cold agglutinin in high-pasteurized milk has been inactivated, and a cream layer forms much more slowly, but it is a compact, hardly dispersible layer; partial coalescence of the fat globules may even result in a solid cream plug As a result, this milk is frequently homogenized To save money, only the cream fraction of the milk is usually homogenized (partial homogenization) Obviously, all milk should be separated at this point Homogenization clusters should be absent after homogenization; as a result, the fat content of the cream should be low (10% to 12%), and the homogenizing temperature should not be too low (55°C); additionally, two-stage homogenization should be used To reduce the possibility of recontamination, homogenization is usually done before pasteurization Because milk lipase is still present, the milk should be pasteurized right away Due to cold agglutination, the milk may retain cream after partial homogenization This is due to the fact that the agglutinin in skim milk after heated separation is not completely inactivated by pasteurization Standardization: [7] [9] Standardization with respect to fat content can be done by adding skim milk (or cream) to the milk in the storage tank or by continuous standardization Standardization of the composition of a milk product is needed because it is legally required or because manufacturers set a standard for their product It mostly concerns the fat content, often also the dry-matter content (or the degree of concentration), sometimes the protein content, or still another component Pasteurization: [7], [8], [10], [11], [12] Pasteurization ensures the safety and greatly enhances the shelf life of the product Every particle of milk and/or milk product is heated in properly designed and operated equipment that meets the requirements to one of the temperatures specified in the following table and held continuously at or above that temperature for at least the time specified: Table *If the fat content of the milk product is ten percent (10%) or greater, or a total-solids of 18% or greater, or if it contains added sweeteners, the specified temperature shall be increased by 3ºC (5ºF) Image Source: Grade “A” Pasteurized Milk Ordinance (PMO) established by the Food and Drug Administration (FDA) [13] Effects on microorganisms: Pasteurization destroys all pathogens, including Mycobacterium TB, Salmonella spp., enteropathogenic E coli, Campylobacter jejuni, and Listeria monocytogenes, to the point where there is no health risk Some cells of Staphylococcus aureus strains survive heat treatment, but they not proliferate to the point where they produce dangerous levels of toxins Low pasteurization kills most spoilage microorganisms in raw milk, including coliforms, mesophilic lactic acid bacteria, and psychrotrophs Heat-resistant micrococci (Microbacterium spp.), some thermophilic streptococci, and bacterial spores are among those who are not killed Except for Bacillus cereus, these microbes not develop quickly in milk The latter organism is harmful in big quantities, but the milk had become undrinkable due to its off-flavor previous to this Effects on enzyme activity: Lipases are enzymes that degrade fats The major lipase in milk is lipoprotein lipase It is associated with the casein micelle Agitation during processing may bring the lipase into contact with the milk fat resulting in fat degradation and off-flavors Pasteurization will inactivate the lipase in milk and increase shelf life Proteases are enzymes that degrade proteins The major protease in milk is plasmin Some proteases are inactivated by heat and some are not Protein degradation can be undesirable and result in bitter off-flavors Pasteurization does not inactivate plasmin, although the shelf life of pasteurized beverage milk is usually too short to cause difficulties Alkaline phosphatase is a heat sensitive enzyme in milk that is used as indicator of pasteurization Batch pasteurization or high-temperature, short-time pasteurization inactivates the alkaline phosphatase and, therefore, the presence of phosphatase activity in pasteurized milk indicates either improper pasteurization or post-pasteurization contamination with raw milk Testing milk for phosphatase for regulatory and quality control purposes has been a common practice for nearly 30 years Since adoption of the phosphatase test as an indicator of proper pasteurization, several modifications for the detection of phosphatase have been developed which possess a high degree of sensitivity and accuracy The acid phosphatase is more heat-stable than alkaline phosphatase and is not inactivated completely upon pasteurization Lactoperoxidase, another enzyme present in raw milk, is inactivated by heat treatments in excess of about 80oC for 15s Thus, the presence of lactoperoxidase can be used to detect milk which has not been over-heated, it can help to check the intensity of highpasteurization of milk On pasteurizing homogenized milk, the agglutinins should be inactivated to such an extent as to prevent creaming of the milk A cooked flavor may sometimes be observed High-pasteurized milk has a somewhat whiter color (as has ultra-high temperature [UHT] short-time heated milk), for the most part due to its homogenization A more intense heating causes browning due to Maillard reactions Occasionally, heating to over 100°C is applied to kill spores of B cereus, thereby enhancing shelf life Packaging: [7] [11] Today more than 75 percent of retail sales are in translucent plastic jugs Glass bottles make up less than 0.5 percent of the business and are used mostly at dairy stores and for home delivery In terms of product safety, but especially because of the effect of recontamination on the shelf life of the product, great care should be taken to guarantee hygiene during packaging; aseptic packaging would be preferable Due to movement in pipelines and on conveyor belts, as well as the usage of sealing technology, the temperature of the milk may rise by around K during packaging Because packaged items take a long time to recool, especially if they are stacked close together, such temperature rises should be anticipated by a deeper chilling following pasteurization Modern packaging machines remain fresh for at least 14 days and has made it possible for use with ultra-pasteurizing equipment for extended shelf-life applications 2.1.2 Changes during Pasteurization 2.1.2.1 Microbiological Aspects [7], [10], [12] Raw milk from healthy animals has a very low microbial count, but it easily becomes contaminated with spoilage and sometimes pathogenic microorganisms These need Heat Treatments of Milk – Pasteurization From a milk processor’s standpoint, raw milk composition and its microbial loading will vary from day to day So applying heat treatment as soon as possible after milking is needed Pathogenic microorganisms in raw milk, which may be picked up from the farm environment, will be destroyed (in a small number) These include non‐spore‐forming bacteria such as St aureus, Campylobacter jejuni, Salmonella spp, Escherichia coli including E coli O157:H7, Yerisinia enterocolitica, Listeria monocytogenes, C burnetii and M tuberculosis, together with spore‐formers such as Bacillus cereus and Clostridium spp The non‐spore‐forming pathogens can be effectively controlled by pasteurisation The second microbiological group will be eliminated are spoilage organisms, particularly psychrotrophic bacteria which can grow and cause spoilage during storage of milk at low temperatures Pseudomonas species are the major psychrotrophic bacteria in cold‐stored raw milk but several other psychrotrophs also occur Since these bacteria increase in numbers over time, raw milk should be processed as quickly as possible The commercial reality is that some raw milk is pasteurised within 24 hours of milking, but some may be up to one week old before it is pasteurized In addition, it is important for the raw milk to be maintained at a low temperature, preferably ≤4 °C In countries where it is not possible to refrigerate raw milk, its keeping quality can be extended by activation of the naturally occurring milk lactoperoxidase system While pasteurisation destroys the pathogenic and most of the spoilage non‐spore‐forming bacteria in raw milk, some thermoduric bacteria remain A count of the microbial flora in pasteurised milk determined soon after processing provides a measure of these thermoduric bacteria High thermoduric counts are sometimes found in raw milk and these give rise to high counts in freshly pasteurised milk These most probably arise from brief lapses in hygiene during milking, poor temperature control or unfavourable climatic conditions Thermoduric bacteria play a minor role in spoilage of pasteurised milk The thermodurics include non‐spore‐formers and spores of spore‐formers which are more heat‐resistant than the non‐spore‐formers; the spores all survive 80°C for 30 minutes and some survive 100°C for 30 minutes Some non‐spore‐formers such as coryneforms also survive 80°C for 30min The main non‐spore‐ forming thermoduric genera are Microbacterium, Micrococcus, Enterococcus, Lactobacillus, Corynebacterium and Streptococcus and the main spore‐forming genera are Bacillus, Geobacillus, Paenibacillus and Clostridium While the thermoduric non‐spore‐forming bacteria are not pathogenic, some sporefomers are Of particular interest are Clostridium species and some strains of B cereus 2.1.2.2 Enzyme Inactivation [7], [10, [12], [14] Table Behaviour of some important endogenous milk enzymes under heat treatments utilised for the production of milk for human consumption Both plasmin (EC 3.4.21.7) and plasminogen activators survive pasteurization and are resistant to many UHT treatments Low pasteurization enhances plasmin activity in milk by causing inactivation of plasminogen inhibitors, allowing the conversion of plasminogen to plasmin; only an appropriate UHT treatment (140°C for 15 s) can inactivate the plasmin system Nevertheless, the activation of bovine plasminogen observed at pasteurization temperatures could be attributed to its denatured form, which is more readily activated by plasminogen activators than the native form Lipoprotein lipase (EC 3.1.1.34) is heat sensitive and is almost inactivated by low pasteurization (63°C for 30 or 72°C for 15 s) Therefore, it is not an agent that could potentially deteriorate market milk Alkaline phosphatase was the most heat labile of those measured However, Acid phosphatase was much more heat resistant than alkaline phosphatase Therefore the alkaline phosphatase is inactivated through low-pasteurization while the acid one in not or just partially inactivated by pasteurization Alkaline phosphatase is an enzyme strongly connected to the heat treatment of milk because estimation of its activity is used to monitor the efficacy of (low) pasteurization of milk A complication related to its use as a heat treatment indicator is its reactivation after UHT treatment of milk No reactivation is observed in pasteurized milk and homogenization before heat treatment reduces the extent of reactivation Lactoperoxidase (LPO, EC 1.11.1.7) is a very important antimicrobial factor in raw milk and is one of the most heat-stable endogenous enzymes Because of its heat stability under the pH conditions of milk, LPO activity is used as an indicator for heat treatments of milk more severe than low pasteurization, i.e high pasteurization is such that the activity of the enzyme lactoperoxidase is destroyed, for which 20 s at 85°C suffices, although slow reactivation may be observed γ-Glutamyl-transferase (EC 1.15.1.1) has been proposed as an indicator of milk heat treatment at temperatures above 77°C After low pasteurization treatment at 72°C for 15s, more than 50% residual activity is observed; after treatment at 75°C for 15 s, less than 10% residual activity is observed No activity is observed after heating at above 77°C for 15 s For this reason γ-glutamyl-transferase has been proposed as an indicator of milk pasteurisation at temperatures above 77°C Catalase (EC 1.11.1.6) activity increases as SCC increase About 26% of its activity is destroyed after milk thermalization at 60°C for 16 s Low pasteurization reduces its activity by 92% The reactivation of catalase observed during refrigerated storage of heat-treated milk has been attributed to heat-resistant microorganisms N-Acetyl-β-d-glucosaminidase (EC 3.2.1.30), a lysosomal enzyme released from somatic cells into the milk serum, is inactivated by (low) pasteurization Enzymes may also arise from psychrotrophic bacteria Many of these are very heat‐ resistant and survive pasteurization However, it is unlikely that residual bacterial lipases and proteases will cause problems in pasteurized milk because of its relatively short shelf‐life, the refrigerated storage conditions and the very low activity of the residual protease In general, however, it is best to avoid using aged milk for pasteurization because of the risk of its containing bacterial enzymes but also because of its higher microbial count, higher acidity (lower pH), reduced heat stability, and greater likelihood of having off‐ flavours 2.1.2.3 Other Changes [7] [10] There are some other important changes that take place during pasteurization As far as chemical reactions are concerned, pasteurization can be considered to be a mild process In low-pasteurization, the flavor of milk is hardly altered, little or no serum protein is denatured, and cold agglutination and bacteriostatic properties remain virtually intact A more intense heat treatment is, however, often applied (e.g., 20 s at 75°C) This causes, for instance, denaturation of immunoglobulins (hence, decrease in cold agglutination and bacteriostatic activity) and sometimes a perceptible change in the flavor of milk In high-pasteurization, most of the bacteriostatic properties of milk are destroyed Denaturation of part of the serum proteins occurs A distinct cooked flavor develops; a gassy flavor develops in cream There are no significant changes in nutritive value, with the exception of loss of vitamin C The stability of the product with regard to autoxidation of fat is increased Except for protein denaturation, irreversible chemical reactions occur only to a limited extent Between and 15% of the whey protein is denatured in milk This is not sufficient to significantly release levels of volatile sulfur compounds which cause the development of cooked flavour as occurs with higher temperature treatments Whey protein denaturation is higher during pasteurization of skim milk concentrates produced by ultrafiltration, increasing with the increase in the concentration factor Pasteurization results in little change in the renneting properties of milk and little association of whey proteins with casein; as a result, good quality cheddar cheese can be produced from pasteurized milk and the majority of milk for cheesemaking is subjected to pasteurization No dephosphorylation and no significant reduction in pH and ionic calcium occur during pasteurization and there is very little effect on the heat‐sensitive water‐soluble vitamins Overall, pasteurization results in little change in texture, flavour and colour, compared to raw milk It was clear that the majority of people are unable to distinguish between raw and pasteurized milk It is reported that pasteurization barely alters the flavour of milk and that the volatile flavours responsible for cooked flavour are negligible 2.1.3 Shelf life [7] [15] [16] Shelf life is the time during which the pasteurized product can be kept under certain conditions (e.g., at a given temperature) without apparent undesirable changes Changes in beverage milk during storage can be distinguished in: Decomposition by bacteria growing in the milk, such as acid production, protein breakdown, and fat hydrolysis Decomposition by milk enzymes or by extracellular bacterial enzymes, like fat and protein breakdown Chemical reactions causing oxidized or sunlight flavor Physicochemical changes such as creaming, flocculation, and gel formation, which may, in turn, be caused by the above-mentioned changes Pasteurized drinking milk can have a shelf-life in the range of five to 20 days, depending on the quality of the raw milk, pasteurization conditions, the growth rate (generation time, g) of the bacteria involved, Extent of recontamination and finally is the Storage temperature In general, the lower the storage temperature, the longer the shelf-life of pasteurized milk The storage temperature of the milk is important because the generation time of the microorganisms is highly temperature dependent, as is shown in Table Table 4.Gerneration Time (Hours) of some Bacterial Strains in Low-Pasteurized Milk at Various Temperatures The shelf life of the milk at various temperatures may be predicted if the species of the bacteria involved as well as their initial count and generation time are known After pasteurization of the milk its count usually amounts to between 500 and 1000 ml-1, unless many heat-resistant bacteria are present in the original milk As a rule, the milk is spoiled by ‘sweet curdling’ caused by B cereus (g ≥ 10 h at 7°C), unless it is recontaminated B cereus, forming lecithinase, is also responsible for the ‘bittycream’ defect in nonhomogenized milk At a storagetemperature below 6°C, B cereus cannot grow; deterioration may then be caused by B circulans Below 10°C the milk deteriorates by the growth of psychrotrophs (g = to h at 7°C) The flavor becomes putrid and rancid due to protein degradation and hydrolysis of fat, respectively The effect of the temperature on the length of time thatpasteurized milk can be kept is shown in Table Table Examples of the Averages Numbers of Days That low- pasteurized milk can be stored at Various Temperatures before It surpasses the Criteria for Guaranteed Day of Ultimate Sale (A) and Guaranteed Shelf Life (B) Milk contains, say, 10 spores of B cereus per 100 ml; its shelf life for normal storage conditions amounts to 12 to 14 days if it is not recontaminated If the pasteurized milk is recontaminated, deterioration is generally faster and of a different nature This is illustrated in Table 16.2, in which the milk leaving the pasteurizer has not yet been recontaminated, but it commonly becomes so during packaging The presence of coliforms, detectable after keeping the milk at 20°C, is an indication of recontamination having occurred The (recontaminated) milk, stored uncooled, turns sour by the growth of, e.g., mesophilic lacticacid bacteria 2.1.4 Criteria 2.1.4.1 Viet Nam criteria for pasteurised milk (TCVN 5860:2007) [17] Sensory criteria Table Sensory criteria (Pasteurisied milk) Physicochemical criteria Table Physicochemical criteria (Pasteurilized milk) Microbial standards Table Microbial standards (Pasteurized milk) 2.1.4.2 FDA criteria for pasteurized milk [13] Table FDA criteria for pasteurized milk Chemical, Physical, Bacteriological and Temperature Standard (for FDA validated and NCIMS Accepted Test Methods.) Cooled to 70C (450F) or less and Temperature maintained thereat Bacterial limits