Fresh-keeping technology of cured meat products
Curing products refer to meat products made from salted, baked or air-dried meat raw materials. They cannot be directly imported and must be cooked before cooking. Such foods generally include sausages, bellies, hams, ducks, etc. Their health problems are mainly nitrite residues, fatty oxidative rancidity and mildew. Professor Wu Yongnian, executive director of the China Animal Products Processing Research Association, deputy chairman of the Storage and Preservation Professional Committee, and chief engineer of Nanjing Yongqing Food Preservation Technology Development Co., Ltd. believes that only the use and mechanism of various food additives and the correct food The use of additives, and the use of advanced packaging technologies, etc., can effectively guarantee the quality of the cured products, and make the additives in the cured products meet the relevant national food hygiene standards. First, the correct use of nitrite The role and harm of nitrite In the processing of cured products, nitrates are often added, including nitrates (mainly sodium salts and others) and nitrites. Prof. Wu Yongnian said that the use of nitric acid in the production process of cured products is mainly reflected in the following three aspects: (1) Hair color: Nitrate can make red products of preserved products and maintain red roses. (2) Bacteriostasis: Nitrate can inhibit the growth and reproduction of harmful microorganisms such as Clostridium botulinum. Curing products such as sausages and fragrant bellies are likely to cause anaerobic bacteria growth and reproduction due to their relative oxygen barrier, thus causing harm to the human body. Nitrates can effectively inhibit the growth and reproduction of anaerobic bacteria. (3) Contribute to the formation of the waxy taste inherent in cured products. Although nitrates have so many advantages, researchers have also discovered that when nitrates are added to meat products, they may also cause some harms, mainly in the following three aspects: (1) Acute nitrite poisoning. Some producers understand the color of nitric oxide in a one-sided manner, and believe that the more nitric acid is added and the better the color, the indiscriminate use of nitrate in the production process of cured products. Acute poisoning occurs when the nitrite intake reaches 0.3-0.5 g; 1-3 g intake can cause death. (2) The formation of carcinogenic nitrosamines. When the nitrosamine content reaches 200ppm, it can cause cancer. (3) The chemical properties of nitric acid are particularly active, and hundreds of unknown substances are formed. Nitrous acid and its decomposition products can react with almost all substances such as proteins and fats, and the resulting substances are very complicated. So far, researchers have not fully figured out whether these products are harmful and how harmful they are. This is also a major hidden danger. 2. Changes in Nitrate in Meat Products The changes in nitrates and nitrites in meat products are as follows: Nitrate, Nitric acid, Nitrite, and Nitrite幔 绦 绦 诘 诘 诘 诘 H H H H H H H H H H H H H H H H H H H H H H H H H H → Nitric oxide + myoglobin (exist in muscle) → Nitric oxide myoglobin ). In the mature period of production or long storage period, if nitrates are used in products such as fragrant ham and ham, and if the temperature is high or bacterial contamination is serious, a large amount of nitrates will be reduced to nitrite in a short time. As a result, the amount of nitrite residues was significantly exceeded. Therefore, the production of cured products is often carried out in autumn and winter. If it is produced in summer, the temperature must be controlled within 10°C. In the process of product storage, nitrite residues showed a trend of rising first and then decreasing. 3. Contradictions between national standards requirements and production (1) Consumption of nitric acid: GB2760-96 "Hygienic Standards for the Use of Food Additives" stipulates that the amount of nitrate is 0.5 g/kg, and the amount of nitrite is 0.15 g/kg. Kg. At present, China's many manufacturers of cured products will set the actual amount of nitrate as: nitrate 0.3g/kg, nitrite 0.1g/kg. (2) Residual amount: Many Chinese nitrite products have a nitrite residue of 20 mg/kg. The colorectal gland is 30 mg/kg, and the western product is 70 mg/kg. In this way, the amount of nitrite residues in the product will often exceed the allowable amount of nitrate added. 4. Common problems and treatment methods in the production process Prof. Wu Yongnian said that in the production process of cured products, if nitrates are added according to the current national standards, sometimes the nitrite content in the products will exceed the standard. The meat products produced by some large-scale well-known food enterprises in China sometimes have problems of excessive nitrite content. Therefore, production companies should take corrective measures. (1) When the amount of nitrate used exceeds the standard, and the nitrite residue level exceeds the standard, the treatment method is: store the product in the factory for a period of time, wait for the nitrite residue to drop, and then sell the product after reaching the standard. (2) If the nitrite content in the product is no longer likely to drop, or if the nitrosamine content exceeds the national standard, the manufacturer shall destroy the cured product. 5. Reasonable use of nitric acid (1) Proper use: Add nitric oxide in an appropriate amount so that the amount does not exceed the standard; Stir evenly; Control the processing temperature. (2) Add the auxiliary agent, such as sodium erythorbate in the material. (3) Use alternative substances. Second, the hazards of oxidation and rancidity of oils and fats and the prevention of foods containing fats such as curing products after long-term storage, the fats of which will be hydrolyzed, oxidized and rancid reaction due to the effects of light, heat, water, air and microorganisms. The deterioration of the quality of fat-containing foods, and even the production of toxic and harmful substances, makes these products lose their original food value. 1. hydrolysis. This is a process in which water is added to fat to initiate the decomposition reaction. Because fats contain lipase, when there is water in the surrounding medium, the fat breaks down, producing free fatty acids and glycerol. As a result of the hydrolysis, the acidity and melting point of the oil increase, and the odor becomes unpleasant. At the same time, since the glycerin is dissolved in water, the weight of the oil is reduced. 2. Oxidation. This is a chemical reaction that occurs when the oil is catalyzed by light, resulting in the production of hydroxy acids. The brief reaction process is as follows: unsaturated fatty acids are oxidized to produce peroxides; at the same time when peroxides are formed, ozone is often released, and ozone is combined with saturated fatty acids to form ozonation products; ozonation products are in water. Under the action of the reaction, a carbon chain cleavage reaction occurs to form aldehydes (such as malonaldehyde) and peroxides (such as hydrogen peroxide); some aldehydes are oxidized and become acids, thereby increasing the acidity of the fat. In addition, the glycerol produced during the hydrolysis of oils and fats can also be dehydrated and decomposed to form acrolein, which produces a strong odor and burnt smell. After the acrolein is oxidized, glycidaldehyde is also produced. Under the action of water, peroxides transfer oxygen to form hydrogen peroxide. Hydrogen peroxide reacts with unsaturated fatty acids to produce hydroxy acids that increase the melting point and freezing point of the fat, whiten the color, harden the state, lower the iodine value, and cause the product to have a special stale odor. 3. Rancid. The rancidity is a series of chain reactions of oxidative hydrolysis, including two forms of hydroformylation and ketosis. Ketoacidosis is characterized by the formation of ketones, the reaction process is: fat in the role of water, the formation of β-hydroxybutyric acid. The decomposition products of rancid oils include compounds such as aldehydes, ketones, and acids, which have a bitter taste, are toxic, and are inedible. The nature of the breakdown products is also very unstable and can also destroy the vitamins in food. 4. Acid price exceeded. The acid value is the most common hygienic indicator in hygiene standards for cured products. For example, the hygienic standard of GB10147-88 sausage (sausage) and fragrant belly stipulates: Acid price ≤4.0; GB2732-88 Hygienic standard for salted duck (salted duck) Regulation: Acid price ≤ 3.0. The acid price index is set in the hygienic standard of the cured products in order to reflect the degree of fat oxidation and rancidity through the acid price. The definition of acid value: refers to the number of milligrams of potassium hydroxide needed to neutralize the free fatty acids in 1 gram of oil. The acid value is determined by titrating the extracted oil with potassium hydroxide. The survey shows that the acid price often exceeds the standard in the random sampling of the market, causing significant economic losses and loss of reputation to the company. In view of the reasons for the excessive acid content in the cured products and the solutions, Prof. Wu Yongnian and other experts made a series of investigations and studies and obtained data with important guiding significance. Two typical representative tests are presented here. The first test was aimed at Nanjing Xiangdu. The results showed that there was no significant difference between the acid value of the incense-enough added with antioxidants or the packaged deodorant and the bulk control group, while the refrigeration could significantly inhibit the increase of the acid value. This is because, theoretically speaking, the rise in acid value has nothing to do with the amount of oxygen, and it is only related to the activity of lipase, and refrigeration can inhibit the activity of lipase. The second experiment took Nanjing sausage as the research object. The results showed that: (1) Adding soy protein can increase the rate of rise of acid value, and at the same time greatly reduce the rate of increase of peroxide value. The reason for this is that soy protein contains flavonoids, and flavonoids have a significant antioxidant effect, which can inhibit the occurrence of fat oxidation reaction; but from the perspective of metabolic decomposition, soy protein is an acidic substance. It will neutralize part of the potassium hydroxide in the food, which will increase the acid value of the food. (2) The use of vacuum packaging can suppress the increase of peroxide value of sausages and the increase of acid value at the late stage of storage, but has little effect on the change of acid value during the early stage of storage. This result is the same as that of the first test, because vacuum packaging cannot inhibit the activity of lipase, so it cannot prevent the rise of acidity during the early storage of sausages. However, during the later period of storage, the increase in the acid value of the cured products was mainly caused by peroxide-generating acids. Therefore, the use of vacuum packaging to block oxygen can inhibit the rancidity of fat in the late storage period, thereby preventing the increase in acid price. (3) The addition of starch can increase the rate of acid rise. The reason for this may be that starch produces lactic acid during anaerobic glycolysis, which causes an increase in the acid price. (4) Adding D-isoascorbate sodium, it is difficult to inhibit the rise of acidity in the early stage of storage, but it has a certain influence on the later period. The change of peroxide value shows a rapid increase in the early period and a rapid decrease in the later period. During the metamorphic process, the sausage is yellowed from the normal to the beginning, resulting in a period of catastrophic taste. The change in peroxide value is basically consistent with the sensory result, but the acid value is not necessarily. In summary, the acid price is not a specific indicator reflecting the rancidity of fat oxidation in cured products. In measuring the degree of oxidative rancidity of the cured products, the use of peroxide values ​​as indicators is more appropriate. To this end, Prof. Wu Yongnian once proposed to the relevant state authorities to amend the national hygienic standard for cured products, remove the acid price index and replace it with the peroxide value index. At present, this proposal has been adopted by the Ministry of Health. 5. Fat oxidation rancidity prevention methods and updates. (1) Apply sesame oil. This is a common method used in the 1970s. During operation, sesame oil is applied to the surface of the cured product, or the cured product is immersed in sesame oil in order to shut off the product from the oxygen in the air. Doing so can extend the shelf life of the product by 1-2 months. However, this method not only consumed sesame oil, increased production costs, but also was time-consuming and was gradually eliminated. (2) vacuum packaging. In the 1970s, vacuum packaging was gradually used in the food industry. The main point of this method is to pack foods in a low-permeability composite plastic bag and vacuum the bags. With vacuum packaging, the shelf life of foods can be greatly extended, and the anti-oxidation effect of the cured products can be maintained for more than 6 months. (3) Deoxygenation packaging. At present, oxygen-free packaging is increasingly valued by food companies. The principle of oxygen scavenging packaging is: oxygen scavenger can generally remove oxygen in the packaging bag within 24 hours so that the food is in a state of high oxygen deprivation, thereby inhibiting or eliminating various food degradation caused by adverse reactions requiring oxygen participation. . The amount of oxygen scavenger can be determined according to the length of time the food needs to be stored. It is very flexible. (4) Add antioxidants. The addition of antioxidants such as sodium erythorbate can extend the shelf life of the product for about one month. The use of sesame oil, vacuum packaging, deoxygenation packaging, and other methods for the shelf life of the cured products can result in a substantial reduction in the peroxide value of the products, but it does not necessarily have a significant effect on the acid value. Third, the prevention of moldy mildew products When the curing measures for curing products are improper, such as the warehouse is damp, not ventilated or product accumulation, often cause mildew. If mildew develops on the surface, the mildew layer can be scraped off and the rest can be reused. If mildew has reached a deep layer or the moldy surface cannot be scraped, it should be discarded. The mildew of the cured products mostly occurs in bulk products. With vacuum-packed products, mildew can also occur if the seal is not tight or the package is broken. Anti-mildew method is: bulk products should be hanging in a well-ventilated, dry room. Sunny days open the windows for ventilation and ventilation, but in the rain they close the windows. Using vacuum packaging and oxygen scavenging packaging, as long as the process according to the provisions of the operation, can effectively prevent mildew.
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