A change in the quality and even spoilage of drinking milk can occur under the influence of many factors, and therefore proceed in different ways. With full observance of the modes and parameters of the technology, as well as the established storage conditions (duration, temperature), as a rule, all of them retain the quality within the norm of standard requirements throughout the warranty period of storage.
color flaws
brownish tint
Cause. Melanoidin reaction products during long-term storage of baked and sterilized milk.
. Observe the temperature and duration of languishing, milk sterilization, and avoid prolonged storage of the product.
Pronounced yellow, pink-red shades
Cause.
Prevention and mitigation measures
Consistency defects
Viscous sand
Cause. Zootechnical factors, violation of milking rules and high bacterial contamination of raw milk.
Prevention and mitigation measures. Do not mix colostrum and old milk with normal milk. Comply with the conditions for obtaining, storing and transporting milk.
Noticeable fat sludge
Cause. Insufficient homogenization efficiency.
Prevention and mitigation measures. Maintain the required homogenization pressure in accordance with the technological instruction (TI).
flaky
Cause. The use of raw materials - milk with low thermal stability. The development of Bacillus subtilis, B. circulans, B. coagulans and non-spore-forming bacteria as a result of violation of the regimes: sterilization, asepsis, washing and disinfection of equipment (tanks, pipelines) and storage.
Prevention and mitigation measures. Select raw materials for thermal stability. Observe the modes of sterilization, washing and disinfection of equipment (tanks and pipelines), as well as the storage conditions of the product.
Presence of rendered fat
Cause. Denaturation of protein shells of fat globules and their partial destruction
Prevention and mitigation measures. Observe the parameters of languishing in the production of baked milk.
Thickening (gelling), noticeable sediment in sterilized milk
Cause. Enzymatic and physico-chemical processes during long-term storage of the product.
Prevention and mitigation measures. Do not use raw materials - long-term storage milk. Do not allow long-term storage of the finished product. Reduce product storage temperature
Sediment of non-dispersed particles of milk powder, watery
Cause. Unsatisfactory quality of milk powder. Non-compliance with the parameters of the dissolution of milk powder, lack of homogenization.
Prevention and mitigation measures. Use quality powdered milk. Observe the parameters of the dissolution of milk powder in accordance with TI. Carry out homogenization.
Defects of smell, taste and aroma
Forage, unclean
Cause. Zootechnical factors, violation of the conditions for obtaining and storing milk.
Prevention and mitigation measures. Comply with the conditions for obtaining, storing and transporting milk.
bitter taste
Cause. The development of secondary microflora with high lipolytic and proteolytic activity during long-term storage after unsatisfactory washing and disinfection of equipment. Residues of detergents and disinfectants.
Failure to comply with the rules for feeding and keeping cows, the conditions for storing milk on the farm. Long-term storage of milk in packages, including non-standard materials.
Lowering the milk sterilization temperature; insufficient sterilization efficiency of milk and packaging material.
Specific (drugs, petroleum products)
Cause. Violation of the rules for the treatment of cows and the storage of milk.
Comply with the conditions for obtaining, storing and transporting milk.
Soapy, soda flavors
Cause. Contact with detergents and disinfectants. Intentional neutralization with soda to reduce the acidity of milk.
Prevention and reduction measures. Thoroughly rinse the equipment (pipelines and containers), do not allow detergents and disinfectants to enter the product. Do not allow falsification of milk with soda.
Slightly salty taste
Cause. Ingress of brine during cooling of the product.
Prevention and reduction measures. Ensure that no brine enters the product during cooling.
Watery, incomplete taste
Cause. Mixing the product with water residues in tanks and pipelines. Malfunction of the automatic temperature difference control system during preheating, steam sterilization and in the vacuum chamber. For reconstituted milk - the use of low-quality milk powder. No homogenization.
Prevention and reduction measures. Monitor the complete outflow of water from tanks, pipelines when starting or temporarily stopping the line. Reject the first packages with the product. Maintain the preheat temperature before sterilization 1 to 2 °C lower than in the vacuum chamber.
Use good quality milk powder. Be sure to homogenize. Use fragrances.
Smoky
Cause. The ingress of milk on hot surfaces (200 - 250) ° C in Tetra-Pak machines due to a pressure drop of the product during its uneven supply from an aseptic tank.
Prevention and reduction measures. Monitor the correct operation of the pressure regulators in the aseptic tank and ensure a uniform supply of product to the machines.
Pronounced smell and taste of pasteurization, repasteurization, steel, cabbage
Cause. High temperature of heat treatment of milk (130 - 150) ° C and long exposure (more than 5 s).
Prevention and reduction measures. Observe the sterilization regimen.
Caramelized, burnt
Cause. Exceeding the parameters of soaking, UHT treatment and sterilization in bottles. Reduced thermal stability of raw materials. Burning of the product on the surface of the heat exchanger.
Prevention and reduction measures. Use heat-resistant raw materials. Observe the parameters of languor. Make sure that the heat exchangers operate no longer than it is stipulated in the instructions for their maintenance.
Lipolytic, rancid
Cause. Conducting homogenization after pasteurization.
Prevention and reduction measures. Homogenize milk prior to pasteurization. Do not mix pasteurized and homogenized milk with raw milk.
Fruity, malty flavors
Cause. Failure to comply with the rules for feeding and keeping cows, the conditions for obtaining, primary processing and storage of milk on farms.
Prevention and reduction measures. Observe the rules for feeding cows.
Avoid strong and prolonged mixing and long-term storage of raw materials. Thoroughly wash and disinfect equipment.
Sour taste
Cause. Secondary contamination during storage and bottling of pasteurized milk or in the aseptic part of the sterilizer as a result of depressurization of equipment sections, violation of asepsis of bottling or tightness of packaging; poor-quality washing and disinfection of equipment.
Prevention and reduction measures. Observe the technological and sanitary regimes of production.
Strangers, unpleasant
Cause. Enzymatic oxidation of amino acids to keto- and hydroxycarboxylic acids, aldehydes, amines, amyl ketones, ammonia, CO2 during long-term storage of milk.
Prevention and reduction measures. Systematically check the condition of the surface of the plates, change the broken seals in a timely manner and regulate the operation of the return valve of the pasteurization and cooling units. Avoid prolonged storage of the product.
Phenolic
Cause. Bacillus circulans spore contamination in sterilized milk bottled in glass bottles.
Prevention and reduction measures. Hands should be disinfected when lubricating filling machines
Musty, stale
Cause. Accumulation of products of lipid peroxidation reactions during long-term storage.
Prevention and reduction measures. Store pasteurized milk before bottling no more than 6 hours at (6 ± 2) °C. Observe the established duration and temperature of storage from the end of the technological process.
Taste of packaging material
Cause. For long-term storage in packages made of non-standard packaging materials
Prevention and reduction measures.
Do not use packaging materials that have odors and carry out the necessary control. Do not store the product in the packaging for more than a certain period
Oxidized, metal- and light-induced oxidized
Cause. Peroxidation of lipids, vitamins, catalyzed by metals and light exposure
Prevention and reduction measures. Minimize the saturation of milk with air. Avoid contamination of milk with traces of heavy metals, especially copper and iron. Use natural antioxidants. Avoid strong and prolonged shaking. Eliminate the influence of direct short-wave radiation. Properly select and use light- and gas-tight packaging materials. Comply with the rules for transporting milk and technological parameters of production
"Sunny" taste
Cause. Non-enzymatic oxidation of sulfur-containing and some other amino acids as a result of light exposure
Prevention and reduction measures. When packaging products in glass bottles, ensure the least exposure to light during transportation and on retail shelves
For reconstituted milk - rancid, greasy, slightly salty, metallic flavors
Cause. Unsatisfactory quality of milk powder. Excessive content in the water used to dissolve milk powder, mineral salts. Use of raw materials from poorly tinned metal containers.
Prevention and reduction measures. Use good quality milk powder. Monitor the quality of the water used to dissolve milk powder. Use standard milk storage containers
Milk defects are caused by the poor quality of feed, the ingress of microflora into milk, improper processing technology, violation of storage conditions and terms, and other reasons.
Taste defects are the most common type of vices. As a result of the vital activity of lactic acid bacteria or E. coli, milk acquires a sour taste.
Rancid taste is formed in milk during its long-term storage at low temperatures under the action of lipase enzymes. A rancid taste also appears in the milk of the last days of lactation.
The bitter taste in milk is due to the activity of putrefactive peptonic bacteria, and can also be caused by the presence of wormwood in the feed.
Unpleasant specific flavors can appear from the presence in the diet of animals of nettle, garlic, onion, turnip, radish, field mustard, etc.
Salty taste in milk appears in some diseases of the udder.
Milk acquires a metallic taste as a result of the interaction of lactic acid with the metal of the container.
A salty taste occurs in milk when it is stored in the light as a result of the oxidation of milk fat by oxygen in the air.
A smoky taste and smell is possible in sterilized milk and packages if the paper is burned when gluing the transverse seams of the package.
Color defects appear under the influence of pigmenting bacteria with the formation of redness, blue and yellowing of milk. Sometimes yellowing of the color of milk is associated with getting into the milk when milking blood due to the diseased state of the animal.
Odor defects are most often caused by specific feed odors or unsanitary conditions of the premises in which animals are kept. Smell defects include barnyard, rotten, cheesy, garlic, etc.
Consistency defects are formed as a result of the vital activity of certain microorganisms. Milk acquires a thick consistency with the participation of lactic acid bacteria, mucous or viscous - under the action of mucus-forming bacteria. As a result of the development of E. coli bacteria, milk undergoes fermentation and foam is formed. When rennet-producing bacteria enter, the milk coagulates during heating even at low acidity.
When milk freezes, its quality noticeably decreases: the colloidal state is disturbed, as a result of which the milk is stratified; desalinated ice forms on the walls of the container, fat floats to the surface, and protein is concentrated in the central and lower parts. When flaking, flakes and lumps form in the milk. The taste becomes watery and sweet.
Milk received within seven days after calving is called colostrum. It does not withstand pasteurization, has high acidity and a high content of albumin, globulin and salts. Not used for processing.
Old milk is milk produced within 7-10 days before milking is stopped.
It has a salty rancid taste due to changes in the mineral composition and the presence of lipase. Butter from such milk is unstable during storage, the cheese is of poor quality. Old milk is not accepted.
6 . Requirements for the purchase of milk
Technical requirements:
Raw cow's milk.
Milk must be obtained from healthy animals in farms that are free from infectious diseases in accordance with the rules of veterinary legislation, and must comply with the requirements of this standard (GOST 13264-88) in quality.
Milk after milking must be filtered and cooled on the farm no later than 2 hours later. after milking.
Raw milk upon delivery and acceptance at the enterprises of the dairy industry must have a temperature not higher than + 10°C, and upon delivery and acceptance at the farm - no higher than + 6°C.
Milk should be natural, white or slightly creamy in color, without sediment and flakes. Freezing milk is not allowed.
Milk should not contain inhibitory and neutralizing substances. The content of heavy metals, arsenic, aflotoxin M) and pesticide residues in milk should not exceed the maximum allowable level.
Milk must have a density of at least 1027kg/m3.
Raw milk is divided into three grades - the highest, first and second in accordance with the requirements specified in table No. 4.
Table No. 4 Raw cow's milk
Milk intended for the production of baby food and sterilized products must meet the requirements of the highest or first grade, but with a somatic cell content of not more than 500 thousand / cm3 and in terms of heat resistance should not be lower than the 2nd group.
Milk intended for the production of rennet cheeses must meet the requirements of the highest or first grade, but contain no more than 500 thousand/cm3 somatic cells, and, according to the rennet-fermentation test, meet the requirements of at least the 2nd class. The content of spores of mesophilic anaerobic lactate-fermenting bacteria in current milk should be no more than 10 cm3.
Milk intended for the production of baby food products, sterilized products and rennet cheeses is accepted with a corresponding surcharge on the purchase price.
Milk that meets the requirements of the highest, first or second grade, the temperature of which is above + 10 ° C, is accepted as “non-chilled” with a corresponding discount from the purchase price.
The mass fraction of fat and protein in milk must comply with the basic standards.
Milk with a density of 1026 thousand / cm3, acidity of 15 ° C and from 19 to 21 ° C is allowed to be accepted on the basis of a control sample of the first or second grade, if it is according to organoleptic indicators, purity, bacterial contamination and the content of somatic cells meets the requirements of the standard. The period of validity of the analysis of the control sample should not exceed 1 month.
Cow's milk subjected to heat treatment on the farm. Milk obtained from cows in disadvantaged farms for infectious diseases and permitted for use in food by veterinary legislation must be filtered, subjected to heat treatment on the farm immediately after milking and cooled to a temperature not exceeding 10 ° C. Such milk must not be mixed with raw milk obtained from sick animals.
Milk subjected to heat treatment on the farm is classified as non-varietal and in terms of quality it must meet the requirements of this standard.
Reception of milk.
Organoleptic indicators, temperature, density, purity, acidity, mass fraction of fat and pasteurization efficiency are determined in a batch of milk yield.
The mass fraction of protein, and the content of somatic cells is determined at least once a decade. The test results apply to milk taken between and the next test.
Bacterial contamination and inhibitory substances are determined simultaneously at least once a decade. Additionally, bacterial contamination and inhibitory substances may be determined at the request of the farm, but at least once a decade.
If inhibitory substances are found, the demand for milk received from the farm on the day of analysis is not classified as varietal, but subjected to heat treatment on the farm, they are pumped out, they pay a reduced price if the milk meets the requirements for other indicators. Acceptance of the next batch of milk received from the farm is delayed until the results of the analysis for the presence of inhibitory substances and bacterial contamination are obtained, if the presence of inhibitory substances is confirmed, the milk is not subject to acceptance.
Thermal stability is determined in each batch of milk intended for the production of baby food and sterilized products.
The rennet-fermentation sample and the content of spores of mesophilic anaerobic lactate-fermenting bacteria are determined at least once a decade in milk intended for the production of rennet cheeses.
Neutralizing substances are determined in milk if their presence is suspected.
Raw hammer that does not meet the requirements of the second grade, as well as milk from disadvantaged farms for infectious diseases that meet the requirements established by the standard for non-varietal milk, acceptance for food chains
The following should be known about milk defects, their causes and preventive measures.bitter taste
Causes of occurrence.
Appears in freshly milked milk when fed with wormwood, radish and other feeds that contain bitter substances, as well as when milk is stored at low temperatures (below + 6 ° C), when putrefactive bacteria develop.
Prevention measures.
Eliminate foods that contain substances that give milk bitterness.
Strictly observe the sanitary and hygienic conditions for the receipt, processing and storage of milk, the terms established for its storage.
The taste of wormwood, onion, colza, beet tops, silage and other feed
Causes of occurrence.
Irrational feeding.
Prevention measures.
Exclude from the diet or limit the supply of these plants, improve pastures.
Silo odor
Causes of occurrence.
Storage of silage in the barnyard, feeding during milking, untimely cleaning of silage residues.
Prevention measures.
Distribution of silage after milking.
Airing the room, storing the silo away from it.
"Impure" taste and smell
Causes of occurrence.
Dishwashing Disadvantages.
Bacterial contamination of milk.
Storing it in the barnyard in tightly closed jars (especially warm).
Prevention measures.
Compliance with sanitary and hygienic requirements for obtaining and storing milk, washing and disinfecting dishes.
Rapid removal of milk from the barnyard and cooling it.
Sour taste and smell
Causes of occurrence.
Storing milk in dishes that are not clean enough, especially if there is no refrigeration.
Prevention measures.
Compliance with sanitary rules for obtaining milk, washing and disinfecting dishes, equipment, cooling milk, reducing shelf life.
metallic taste
Causes of occurrence.
The use of tinned dishes with rust.
Prevention measures.
Timely tinning of dishes, proper use of detergents, drying dishes after washing.
"Sunny" taste (in combination with metallic) - sweetish, reminiscent of the taste of cabbage, turnips
Causes of occurrence.
As a result of the oxidation of the substances of the fat and protein phases of milk under the action of light, oxygen, copper.
Prevention measures.
Protect milk and dairy products from light, do not use poorly tinned copper and iron utensils, apparatus.
Rancid, salty and overly yellowish color
Causes of occurrence.
Old milk (during the last days before launch), sometimes barren milk, colostrum, milk from cows with udder inflammation.
Prevention measures.
Milk of old cows and colostrum should not be mixed with the total milk yield.
Prevent barren cows.
Timely identify and treat sick cows.
Presence of blood streaks in milk
Causes of occurrence.
Ingestion of blood from damaged nipples into milk.
Prevention measures.
Timely examination of the condition of the udder, separation and treatment of sick cows.
The presence in the milk of flakes, clots with blood, pus
Causes of occurrence.
Milk from cows with mastitis.
Prevention measures.
Identify, separate and treat sick cows.
Milk should not be mixed with the total milk yield.
Putrid taste and smell, slimy milk
Causes
I.
Infection of milk with putrefactive, mucus-forming and other harmful bacteria.
Prevention measures.
Strict observance of sanitary and hygienic requirements for milk production, washing and disinfection of dishes, filter material.
Cooling of milk, observance of terms of storage.
Oxidized taste
Causes of occurrence.
Occurs as a result of the oxidation of iron, increases under the influence of light waves.
rancid taste
Causes of occurrence.
Appears when decomposed by the enzyme lipase.
The defect occurs when milk is stored in the cold, and is aggravated by the presence of traces of copper (from dishes, inventory).
Milk and dairy products are a favorable environment for the reproduction of microorganisms that are not only beneficial for the human body, but also very dangerous for its health.
One of the main sources of microorganisms entering milk is the udder of a cow.
They penetrate into it through the openings of the nipples, are located in the folds of tissues, develop in the remnants of milk.
Interestingly, microbes are almost not found inside the udder, due to the fact that the glandular tissue of the animal inhibits their development.
You need to know that during milking, the first streams of milk wash out the microbes of the udder, while they are seeded with them to the greatest extent.
The source of abundant contamination of milk with harmful microbes is also the contaminated skin of the animal.
In order to prevent the ingress of harmful microbes into milk, it is necessary to wash the cow's udder with warm water and wipe it with a clean dry towel before milking by hand, do not use one portion of water to wash the udders of several cows, remove manure in a timely manner, and keep the barnyard clean.
Microbes also get into milk when they come into contact with insufficiently clean dishes.
For this, it is convincing to cite the following figures: for example, 6000 bacteria were contained in 1 ml of fresh milk, after filtering and pouring into another container - 92000.
Shortly before milking, it is impossible to clean the barn, cows, distribute dry food, remove manure, because. the ingress of dust into milk increases its bacterial contamination.
Washing hands with soap, clean clothes of workers who come into contact with milk are also mandatory conditions for obtaining high-quality pure milk.
Formation of the assortment and quality of drinking milk. Nutritional value consumer properties of drinking milk. Assortment and classification of drinking milk. Factors that shape the quality of drinking milk.
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High-fat milk should not have cream sludge. The taste and smell must be clean, free of foreign tastes and smells not characteristic of fresh milk. The color is white, with a slightly yellowish tint, for melted - with a creamy tint, for non-greasy - with a slightly bluish tint.
Defects of taste.
Arise under the influence of bacterial processes. Sour taste appears as a result of the activity of lactic acid bacteria; bitter- during long-term storage of milk at a temperature below 10 degrees due to the development of putrefactive microorganisms; soapy aftertaste milk acquires during long-term storage, when, as a result of the development of putrefactive microflora, alkaline substances are formed that wash the fat; unpleasant aftertastes in milk can appear from feeding animals fresh nettle, sedge, cabbage, garlic, turnip, etc. salty taste formed in some diseases of the udder of animals. As a result of the vital activity of lactic acid bacteria or E. coli, milk acquires a sour taste. The bitter taste in milk is due to the activity of putrefactive peptonic bacteria, and can also be caused by the presence of wormwood in the feed. Rancid, or lipolytic, taste of milk, the most common taste defect, is a consequence of the hydrolysis of milk fat by lipases at low storage temperatures. It is more common in the milk of old milk cows.
In the presence of traces of copper at elevated temperatures, pH 6.6-6.7, unpleasant metallic and fishy aftertastes may appear. Milk acquires a metallic taste as a result of the interaction of lactic acid with the metal of the container. Under the action of light, oxygen, vitamins B2 (riboflavin) and C, as well as copper, methionine, which is part of whey proteins, is oxidized to methional, which gives the milk a sweet, reminiscent of the taste of turnips or cabbage, the so-called sunny taste. The end products of methionine breakdown can impart a burnt, malty, or starchy flavor to milk. Malty smell and taste are also formed as a result of the enzymatic breakdown of amino acids with the formation of aldehydes and ketones. A smoky taste and smell is possible in sterilized milk and packages if the paper is burned when gluing the transverse seams of the package. As a result of proteolysis of protein substances by putrefactive bacteria and E. coli, putrefactive, cheesy and musty tastes appear. Unpleasant specific flavors can appear from the presence in the diet of animals of nettle, garlic, onion, turnip, radish, field mustard, etc.
Smell vices.
Most often they are caused by specific odors of feed or occur when milk is stored in open containers in rooms where pungent-smelling products are stored. Of the discrediting smells, the most famous are bread, rotten, garlic, cheese, etc.
Consistency defects.
Formed as a result of the activity of certain microorganisms. Milk acquires a thick consistency due to the activity of lactic acid bacteria, mucous or viscous - under the action of mucus-forming microorganisms. As a result of the development of yeast, E. coli and butyric acid bacteria, foam forms in milk. When rennet-producing bacteria enter, the milk coagulates during heating even at low acidity. When freezing, the colloidal state of milk is disturbed, as a result of which it stratifies - desalinated ice forms on the walls of the container, fat floats to the surface, and protein concentrates in the central and lower parts. When thawed, flakes and lumps form in milk. The taste becomes watery and sweet. Thick or slimy milk. This is milk, which has the property of stretching with threads and acquiring this defect after a more or less short period of time after milking. If normal milk is poured into a vessel in which there was diseased milk, then it will soon acquire the same properties. The mucus (viscosity) of milk is determined by the development of mucus-forming races of lactic acid and putrefactive microbes in it. It is observed during long-term storage of milk at low temperatures, when the normal lactic acid process is delayed, and in some forms of mastitis. Such milk is subject to technical disposal and is not used for food purposes.
Color defects.
Appear under the influence of pigmenting bacteria that cause redness, blue and yellowing of milk. The reason for the change in color may also be the presence of a certain amount of blood that has entered the milk during milking due to the diseased state of the animal.
Blue milk. This phenomenon consists in the fact that freshly milked milk, which apparently does not differ from healthy milk, after some time (from 6 to 60 hours) is covered with separate blue spots, and subsequently the entire thickness of the cream is sometimes in the form of a continuous blue veil. After removing this layer of "sick" cream, the blue color appears again, and the milk acquires a nasty smell; the appearance of blue is due to the presence of special fungi, but they contribute to the decomposition of casein, with the formation of aniline blue, which turns the cream blue. Such milk therefore has highly toxic properties. Since the cause of this disease can be not only a disorder of the digestive organs of a given animal, but also an infection, then, in addition to treating a sick cow, it is also necessary to use dairy disinfection, best by fumigating with sulfur and washing walls and dishes with water and bleach.
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