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    Home > Biochemistry News > Microbiology News > The causes of acidification and deterioration of dairy products, and the application of co2-suppressing technology in dairy products

    The causes of acidification and deterioration of dairy products, and the application of co2-suppressing technology in dairy products

    • Last Update: 2020-06-20
    • Source: Internet
    • Author: User
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    Dairy products are ideal for the broad-spectrum microbiome because of their rich nutritionThe preservation of bacteria is an important link in the storage and even the sales stage of dairy products, and acidization and deterioration are the core factors that lead to the deterioration of dairy flavor and the rising bag, and it is also a great challenge for dairy products preservation and storage technologyThe acidification and deterioration of dairy products is not only a "personal performance" of the corrupt flora, but also a joint effect of the corrupt flora and the extracellular enzymes it releasesthe main cause of dairy deterioration - micro-organismsdairy products because of the rich nutrition, so it is the ideal medium for the broad-spectrum microbiomeMost dairy products, such as bus sterilizing fresh milk, yogurt, etc., need to be stored at low temperatures to maintain their good quality and nutritional contentBut cryogenic storage does not inhibit all microorganisms, such as cold-eating bacteriaAccording to the literature, about 25% of all dairy shelf life problems are caused by heat-resistant cold-eating bacteriathe reproduction and growth of the cold-eating Gram-negative genuscan worsen the microbial environment of chilled raw materials, pasteurized milk, skimmed cheese and similar productsPseudomonas is a representative strain of hypoxia bacteria, is a Gram-negative and anaerobic type of cold-eating bacteria, this strain can not only grow in the milk, but also release a lot of biota enzymes of biodegradable milk components, mainly proteases and lipases, these two enzymes can break down proteins and fats, so that the milk produces sensory defectsThese enzymes have heat-resistant properties that affect the quality of preservation of products made from pasteurized milkother common microorganisms such as yeast and mold (ground bacteria, fan moldgens, mold, branch cell genus, penicillin), which can lead to flavor, texture deterioration and visible corruptionIn addition, the growth of heat-resistant lactic acid can reduce the pH of pasteurized milk until coagulation occursstudies show that fresh milk still leaves a certain number of microorganisms after pasteurizationThe growth of microorganisms in 7d after pasteurization of general milk is slow, but with the extension of storage time, the number of cold-osinotic bacteria mainly based on pseudomonas is growing rapidlyWhen the storage time is 10 to 12d, the number of pseudomonas can reach the peak At the same time, lactic acid streptococcus, etc began to multiply rapidly, breaking down lactose to produce lactic acid increased the milk acidity of cattle, pH continued to decline, at this time the growth of pseudomonas abstinium began to be limited After 12d, pseudomonas began to die in large numbers, and when the pH dropped to 5, the growth of streptococcus lactic acid was inhibited Because of the acid resistance of Lactobacillus lactobacillus is strong, gradually occupy the breeding advantage, and continue to produce acid, at this time, a large number of milk coagulants appear, and whey out the application of carbon dioxide inhibition technology in dairy products carbon dioxide (CO2) is the highest oxidation state of carbon atoms, at room temperature with colorless odorless gas state, slightly soluble in water Carbon dioxide is a natural antimicrobial agent that inhibits microbial growth because carbon dioxide molecules are non-polar molecules, they are easily dissolved in the lipid bimolecular layer of microbial cell membranes, and can increase membrane fluidity, exposing cytoplasm to toxic environments The cytoplasm of microorganisms contains water, while carbon dioxide and water hydrated to produce carbonic acid, resulting in a decrease in pH of the cytoplasm and increased pressure on the cells When carbon dioxide accumulates in cells, microorganisms consider it metabolic waste and consume more metabolic energy, while replacing oxygen to a minimum, and degrade reactions, disrupting the normal physiological balance of microorganisms CO2 antimicrobial technology is often used in dairy products preservation in two ways: directly add carbon dioxide relevant studies have confirmed that carbon dioxide on the Gram-positive and Gram-negative microbial growth have inhibition, the effect of this inhibitory effect mainly depends on the degree of solubility of carbon dioxide in the product, so the more soluble liquid dairy products are more suitable for direct addition of carbon dioxide the cylinders filled with liquefaction and compressed carbon dioxide are connected to the bottom of the liquid milk container using a pressure-relief valve and a catheter to fill the liquid milk with the appropriate amount of carbon dioxide at a lower pressure This method has a significant effect on extending the shelf life of liquid milk, for example, pasteurized milk regular shelf life is generally about 15d, directly filled with carbon dioxide shelf life can be extended by about 7d However, direct addition of CO2 is affected by packaging material barriers packaging material is the barrier that isolates liquid milk from the outside environment, its main function is to block the oxygen that accelerates the process of oxidation and deterioration of dairy products The performance is generally characterized by the oxygen transmission rate of the packaging material - the greater the oxygen transmission rate of the package material, the more oxygen per unit time through the same area of the package material It is well known that oxygen promotes the growth and reproduction of most microorganisms, which can lead to the antibacterial effect of carbon dioxide and the effect of extending shelf life the author has used VAC-V2 pressure differential gas permeable meter to test the oxygen transmission rate of a variety of liquid milk packaging materials at different storage temperatures, as shown in Table 1, the oxygen transmission rate of the composite film is significantly lower than the PE membrane, because the composite film assembles the advantages of a variety of film materials, especially the added aluminum foil composite film, its oxygen transmission rate is only 0.05% to 0.16% of the PE membrane at the same temperature Table 1 also reflects the temperature impact of the oxygen transmission rate index of packaging materials, i.e the higher the temperature, the greater the oxygen transmission rate of the material, the less conducive to the barrier to oxygen based on the test results of Table 1, for the use of direct addition of carbon dioxide bacteria-suppressing liquid milk, it is recommended to choose multi-layer plastic composite film, aluminum plastic composite film, paper aluminum plastic composite film or aluminum-plated composite film as a packaging material, make full use of its results of synergistic bacteriobacteria Studies have shown that when carbon dioxide is injected into raw milk, packaging with high barrier materials increases its shelf life by 97.9%, while packaging with low barrier materials increases its shelf life by only 65.6% to add carbon dioxide mixture of gas MAP gas packaging technology MAP also known as gas-conditioning fresh packaging, is a kind of by regulating the content of the gas in the packaging to create a conducive to the atmosphere of the anti-bacterial fresh gas packaging form, powder dairy products because of the form is more suitable for the use of MAP gas-conditioning packaging technology MAP gas-conditioning packaging technology is a certain proportion of nitrogen and carbon dioxide mixture gas into the packaging, filled with inert gas - nitrogen can minimize the amount of oxygen residue in milk powder packaging, carbon dioxide in conjunction with nitrogen to inhibit the reproduction of oxygen-ethmotic bacteria in milk powder, thereby prolonging shelf life need to note that the anti-bacterial effect of MAP gas-conditioning packaging technology is closely related to the stability of the content of each gas component in the package If the packaging used in milk powder is poor barrier to gas, or milk powder packaging seal is poor, it is easy to change the content of nitrogen or carbon dioxide inside the packaging, which is also the milk powder gas adjustment packaging requirements for the use of high barrier to the gas packaging materials, as well as the establishment of regular detection of the content of the gas content of the daily monitoring mechanism used CLASSIC 650 top air body analyzer to test the top air composition content of the two milk powder samples, canned milk powder and aluminum-plastic composite film bag milk powder, the results are as shown in Table 2 Canned milk powder is packed with air-conditioning filled with carbon dioxide and nitrogen, and the content of each gas component is stable during the test, possibly because the mozzarel itself has excellent barrier properties for the gas Aluminum-plastic composite film bag milk powder using nitrogen-filled packaging form, from table 2 can be observed, oxygen content with the extension of storage time slowly increase, nitrogen and carbon dioxide content gradually decreased, this may be due to the aluminum plastic compound bag surface there are pinholes or creases, or there is a leak point, and thus increase the overall oxygen transmission of the packaging anti-bacterial is a permanent topic in the field of dairy storage and preservation, the microbiome mainly cold-eating bacteria in the low temperature environment still has a strong reproductive, is the most important bacteria of dairy products Carbon dioxide is a natural antimicrobial agent, has the effect of inhibiting microbial growth, can be used to directly add carbon dioxide to dairy products and filled with carbon dioxide mixture of the MAP gas to achieve the purpose of anti-bacterial preservation Source: Food Safety Guide
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