Views: 0 Author: Site Editor Publish Time: 2022-09-14 Origin: Site
真空包装 PK 气调包装？
Vacuum packaging PK modified atmosphere packaging?
In today's commodity society, shelf life is a frequently used term. In the food industry, this is a very important indicator, because it is the manufacturer's guarantee and commitment to the quality and efficacy of the product during the circulation period. The shelf life of food refers to the analysis from the perspective of sensory and edible safety, and the quality of food remains acceptable to consumers. storage time at the level. As the basic source of energy and nutrients necessary for people's survival, food needs to have good quality in addition to meeting people's physiological needs and nutritional hygiene requirements. Consumers have higher and higher demand for food quality, a small amount of additives and environmentally friendly Packaging to obtain food with good sensory properties, high nutritional value, health, convenience and long shelf life has become the choice target of more consumers. But all foods undergo varying degrees of deterioration during storage. Deterioration includes the reduction of sensory acceptability, nutritional value and food safety.
Essentially, shelf life is mainly determined by four factors, namely the composition of the food, processing conditions, packaging and storage conditions. These influencing factors have been incorporated into the food safety and quality control system HACCP (Hazard Analysis Critical Control Point). Food is a complex system in which biological, physical, and chemical changes occur simultaneously, which can lead to a decrease in the nutritional value of the food and the production of undesired by-products and even toxins. Similar reactions will continue to occur during storage after processing, and the reaction rate at this time depends on the intrinsic properties of the food, the type of packaging, storage and transportation conditions, etc.
1. Reasons for the deterioration of chilled meat
The main reasons for the deterioration of chilled meat can be summarized into three points:
①The reproduction of microorganisms on the surface of the flesh causes the spoilage of the meat
Its main microorganisms are mainly Pseudomonas under aerobic conditions, and mainly anaerobic and facultative anaerobic lactic acid bacteria and Enterobacteriaceae under vacuum conditions. Most of the bacteria grow on the surface of the meat. The bacteria on the surface of the meat can decompose proteins and other nutrients, so that the surface of the meat is sticky, odorous, and spoiled in a short time.
② Myoglobin in the meat is oxidatively discolored and affects the appearance color of the meat
The color change of meat is controlled by the chemical state of myoglobin and residual hemoglobin. During cold storage, muscle tissue absorbs oxygen in the air, which changes the structure of the body tissue. During the first few days of storage, myoglobin forms unstable oxymyoglobin, which gives fresh meat a bright red color, and then gradually forms stable methemoglobin, which gives fresh meat a dark red (brown) color.
③ Corruption and deterioration of meat quality due to the action of enzymes
High temperature increases the activity of various enzymes in fresh meat and microorganisms, and significantly increases the activity of enzymes secreted by microorganisms to its surroundings, which can facilitate various enzymatic reactions and make meat spoiled.
1) The influence of microorganisms on meat products
The microbial contamination of meat is affected by many aspects such as slaughtering process and subsequent storage conditions. The combination and interaction of internal and external factors determine the growth of microorganisms in meat. Under normal circumstances, the growth of these cold-adaptive bacteria is inhibited to a certain extent because the cooled meat is always in a low temperature environment of 0 to 4 °C. However, if the cold chain system is not perfect, improper control occurs during storage, transportation and sales, resulting in changes or failures of the control system to increase the temperature, microorganisms will multiply rapidly, accelerate the deterioration of fresh meat, and even pose a potential risk to public health. threat.
2) The influence of the external environment on meat products
Temperature can cause oxidation and browning of fat and fat-soluble components, resulting in quality degradation; humidity can cause food to absorb or dehumidify, causing food shrinkage and deformation; light can promote chemical reactions and changes in food color, aroma and taste; In the presence of oxygen, it promotes chemical reactions and causes changes in food quality; filling inert gas can inhibit such chemical reactions, thereby achieving the purpose of inhibiting the decline of food quality.
3) Influence of the inherent properties of meat products on it
Foods with high water-soluble components or moisture absorption will cause browning, reduced solubility and recovery, and loss of nutrients. When there are many fat-soluble components, in the presence of oxygen, light and other conditions, fat oxidation will cause discoloration, fading, flavor changes, and vitamin loss. In foods with enzymes, high moisture content or moisture absorption of foods can easily lead to enzyme activation, resulting in deterioration of food color, aroma and taste.
2. How to extend the shelf life
1) Vacuum packing Vacuum packing
①Introduction to vacuum packaging
Vacuum packaging refers to a packaging method in which the product is put into an airtight packaging container, the air inside the container is removed, and the sealed container reaches a predetermined degree of vacuum. By maintaining an oxygen-deficient environment in the packaging bag, vacuum packaging inhibits the growth of many spoilage microorganisms, slows down the oxidation of fat in the meat, and at the same time reduces the water loss of the meat, keeps the appearance clean and tidy, thereby prolonging the shelf life of meat products.
②Advantages of vacuum packaging
The main advantages of vacuum packaging are good protection, reliable sealing, high vacuum degree, and less residual air, which can effectively inhibit the reproduction of microorganisms such as bacteria, and avoid oxidative mildew and corruption of the contents.
For fresh meat, vacuum packaging has the following advantages:
(1) Prevent drying out
The packaging material provides a barrier to water vapour, preventing drying and keeping the surface of the fresh meat soft.
(2) Prevent oxidation
When vacuuming, oxygen and air are removed together, and the packaging material is shielded from the atmosphere, so that no oxygen enters the packaging bag, and oxidation is completely prevented.
(3) Prevent the loss of meat flavor.
The packaging material can effectively block the overflow of volatile aromatic substances, and also prevent the transfer of taste between different products.
(4) Avoid freezing loss.
The packaging material insulates the product from the outside world, so ice formation and air-drying during freezing minimize losses.
③Defects of vacuum packaging
The principle of vacuum packaging is relatively simple: remove oxygen in the packaging to prevent changes in the properties of the contents (such as food spoilage). Generally speaking, when the oxygen concentration is less than 1%, the growth and reproduction speed of microorganisms will drop rapidly. Vacuum-packed low-temperature meat The shelf life of products is generally more than one month. However, if the contaminating microorganisms, especially the vigorous rot-causing strains, will continue to grow and multiply, the products will often spoil during the shelf life and affect the quality of the products.
Vacuum packaging cannot inhibit the reproduction of anaerobic bacteria and the food deterioration and discoloration caused by the reaction of enzymes. Lactic acid bacteria are the main spoilage bacteria in vacuum-packed low-temperature meat products. When low-temperature meat products are vacuum-packed, in the early stage of storage, these spoilage bacteria are often not detected (<10cfu/g) by culturing, but then the product is rapidly spoiled. Such spoilage characteristics increase the spoilage rate of the product, giving Quality management has caused great difficulties and product safety has also been seriously threatened. Therefore, it is sometimes necessary to combine other auxiliary methods, such as refrigeration, high temperature sterilization, pickling, etc.
2) Modified atmosphere preservation
Modified Atmosphere Packaging
①The principle of modified atmosphere preservation
The preservation mechanism of modified atmosphere packaging is to protect food with packaging materials with good barrier properties, which means filling the packaging with a certain ideal gas component, improving the environmental components in the packaging under certain temperature conditions, inhibiting the growth of microorganisms and preventing enzymes. Corruption caused by the deterioration, to achieve the purpose of preservation and preservation, thereby extending the shelf life of the product. The gases used are usually carbon dioxide, oxygen and nitrogen or their various combinations, and each gas has a different effect on fresh meat preservation. Generally, the shelf life of fresh meat packaged by air can reach 10 to 14 days.
(1) Carbon dioxide acts as a bacterial inhibitor
Carbon dioxide is a stable compound, colorless, odorless, and has a strong inhibitory effect on the reproduction of most aerobic bacteria and molds. At the same time, it can also prolong the lag period of bacterial growth and reduce the speed of its logarithmic growth period. The bacteriostatic effect of carbon dioxide is that in the packaging bag with high concentration of carbon dioxide, carbon dioxide replaces oxygen, and the high carbon dioxide environment makes a large number of aerobic microorganisms ( Such as Pseudomonas) growth is inhibited; the second is due to carbon dioxide, soluble in water to form carbonic acid, reducing the pH value in the environment, so that some acid-intolerant microorganisms lose the necessary conditions for survival; the third is through the osmotic effect on cells , at the same temperature and pressure, the solubility of carbon dioxide in water is 6 times that of oxygen, and the rate of infiltration into cells is 30 times that of oxygen. Due to the large infiltration of carbon dioxide, it will affect the structure of the cell membrane, increase the permeability of the membrane to ions, and change the membrane The balance of internal and external metabolism, and interfere with the normal metabolism of cells, so that bacterial production is inhibited. The infiltration of carbon dioxide also stimulates the activity of mitochondrial ATPase, accelerates oxidative phosphorylation, reduces ATP, and reduces the energy required for metabolic growth of the body.
(2) The role of oxygen
The use of oxygen in modified atmosphere packaging is mainly due to the bright red color of myoglobin in the muscle after combining with oxygen molecules to become oxymyoglobin. Therefore, in order to maintain the bright red color of the meat, there must be oxygen in the packaging bag. Oxygen content in natural air is about 20.9%, so the surface of freshly cut meat is light red when exposed to the air. % oxygen), the formation of methemoglobin is more, and the oxygen must be above 5% to reduce the formation of methemoglobin. However, according to Bartkowski (1982), oxygen must be above 10% to maintain bright red, and more than 40% oxygen can maintain good color for 9d. The formation of bright red oxymyoglobin is also related to whether the surface of the meat is wet or not. If the surface is wet, the amount of dissolved oxygen is large, and it is easy to form bright red.
(3) The role of nitrogen.
Nitrogen is an inert gas, which generally does not work on the packaged material, nor is it absorbed by the food. The air permeability of nitrogen to plastic packaging materials is very low, so it can be used as a mixed gas to buffer or balance the gas in the packaging, and can prevent the collapse caused by filling carbon dioxide.
②The advantages of modified atmosphere preservation
Modified atmosphere packaging is one of the most common and effective ways to extend the shelf life of various foods, including chilled meats. Reasonable modified atmosphere packaging can not only ensure the hygienic quality of meat products, prolong the shelf life, but also have a good impact on the sensory quality of cooled meat. The most commonly used gas components in modified atmosphere packaging are mainly carbon dioxide + oxygen + nitrogen.
The use of this gas mixture is mainly from the point of view of controlling microbial growth and organoleptic quality (such as color). The fresh-keeping effect of this form of modified atmosphere packaging on fresh meat mainly depends on the initial bacterial count of the raw meat, the concentration of carbon dioxide, the presence or absence of oxygen in the packaging bag, the permeability of the packaging material, the storage temperature and the gas composition. It acts as an inhibitor of microorganisms by causing changes in bacterial synthase and enzymatic reaction rates, as well as affecting carboxylation and deamination reactions. The mixed gas is equipped with a certain proportion of oxygen to maintain the color of fresh meat and inhibit the growth of pathogenic bacteria.
The modified atmosphere packaging system is a closed system, in which two processes exist at the same time: one is the physiological serialization process of the product, that is, the metabolic respiration process; The exchange process, these two processes make the air-conditioning system a dynamic system.
The principle of modified atmosphere packaging can be summarized into two points: ① Destruction of the environment in which microorganisms grow and reproduce; ② It can maintain a certain activity of the cells inside the food and maintain a certain degree of freshness. There are two main factors affecting food storage, namely the need for Oxygen bacteria and oxidation reactions, both require oxygen. Therefore, to prolong the shelf life, it is necessary to reduce the oxygen content of the environment. Modified atmosphere packaging technology can make up for the deficiencies of vacuum packaging to a certain extent and further inhibit the spoilage of microorganisms.
③ Precautions for modified atmosphere packaging
(1) Processing of fresh meat before packaging
If the pig is cooled at 0℃-4℃ for 24h after slaughtering, the acid excretion process will occur after the ATP stops moving. The cooled meat treated in this way has far better nutrition and taste than quick-frozen meat and hot fresh meat. In addition, in order to ensure the preservation effect of modified atmosphere packaging, it is also necessary to control the hygienic indicators of fresh meat before packaging to prevent microbial contamination.
(2) Selection of packaging materials
Modified atmosphere packaging should use packaging materials with good barrier properties to prevent the leakage of gas in the packaging and at the same time prevent the infiltration of oxygen in the atmosphere. Generally, composite packaging films such as PET, PP, PA, and PVDC are used as the base material. To measure the gas barrier properties of plastic films, it is generally expressed by the air permeability coefficient: the smaller the air permeability coefficient, the better the barrier properties. In addition, most packaging materials must have sufficient mechanical strength to withstand pressure changes during vacuum. At the same time, the material is also required to have a certain stiffness so that the packaging bag can be automatically opened and inflated.
(3) Control of product storage temperature
The influence of temperature on the preservation effect comes from two aspects: one is that the level of temperature directly affects the activities of various microorganisms on the surface of the body; the other is that the barrier properties of packaging materials are closely related to temperature. The higher the temperature, the better the barrier properties of packaging materials. Low. Therefore, it is necessary to realize the temperature control of the whole process from product, storage, transportation to sales.
At present, vacuum packaging technology can inhibit the growth of microorganisms, prevent secondary pollution, slow down the rate of fat oxidation, make the meat neat and prolong the shelf life of meat products. If the cold meat is vacuum packed, it will have a certain effect on preservation, but its color will be purple. This technology is not perfect. Only modified atmosphere packaging is an ideal method to extend the shelf life of meat products. Modified atmosphere packaging technology to inhibit the growth of microorganisms, thereby extending the shelf life of meat products. Modified atmosphere packaging can not only make the meat bright red, but also inhibit the growth and reproduction of spoilage microorganisms, ensure the hygienic quality of meat products, and maintain the good sensory quality of fresh meat products, significantly extending the shelf life.