Preservation technology of the hottest cured meat

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Under the preservation technology of cured meat products

II. The harm and prevention of oxidative rancidity of fat

after long-term storage, the fat in cured products and other fatty foods will undergo hydrolysis, oxidation and rancidity reactions due to the action of light, heat, water, air, microorganisms and other substances, so that the quality of fatty foods will deteriorate, and even produce toxic and harmful substances, making these products lose their original edible value

1. hydrolysis. This is a process of adding water to fat to cause decomposition reaction. Because fat contains lipase, when there is water in the surrounding medium, fat will decompose, producing free fatty acids and glycerol. The result of hydrolysis is that the acidity and melting point of the oil increase and the smell becomes unpleasant. At the same time, due to the dissolution of glycerol in water, the weight of grease was reduced by the members of the project team who had been engaged in material development

2. Oxidation. This is a chemical reaction of oil under the action of photocatalysis, and the result will be hydroxy acid. The brief reaction process is as follows - unsaturated fatty acids are oxidized to produce peroxides; At the same time of forming peroxides, ozone often travels out, and ozone combines with saturated fatty acids to form ozonation products; Under the action of water, ozonation products will undergo carbon chain breaking reaction to form aldehydes (such as malondialdehyde) and peroxides (such as hydrogen peroxide); Some aldehydes are oxidized and turn into acids, which improves the acidity of fats

in addition, glycerin produced during the hydrolysis of oil can also be further dehydrated and decomposed to form acrolein, which makes the oil produce a strong odor and burning smell. After acrolein is oxidized, it will also form epoxy propionaldehyde

under the action of water, peroxide will transfer oxygen and form hydrogen peroxide. Hydrogen peroxide reacts with unsaturated fatty acids to produce hydroxy acids, which increase the melting point and freezing point of fat, whiten the color, harden the state, reduce the iodine value, and make the product appear special stale smell

3. Rancidity. Rancidity is a series of chain reaction processes of oxidative hydrolysis, including aldehyde rancidity and ketone rancidity. Ketation rancidity is characterized by the formation of ketones, and its reaction process is: fat is formed under the action of water β- Hydroxybutyric acid

the decomposition products of oil after rancidity include aldehydes, ketones, acids and other compounds, which have a bitter taste, are toxic, and cannot be eaten. The nature of decomposition products is also extremely unstable, and it will also destroy vitamins in food

4. The acid value exceeds the standard. Acid value is the most common hygienic index in the hygienic standard of cured products. For example, gb10147-88 hygienic standard for sausage (sausage) and sweet belly stipulates that acid value ≤ 4.0; Gb2732-88 hygienic standard for salted duck stipulates that acid value ≤ 3.0. The purpose of setting acid value index in the hygienic standard of cured products is to reflect the degree of oxidative rancidity of fat through acid value

definition of acid value: refers to the milligram of potassium hydroxide required to neutralize free fatty acids in 1g of oil. The acid value is determined by titrating the extracted oil with potassium hydroxide. The investigation shows that the acid price often exceeds the standard in the market sampling inspection, which has caused great economic losses and reputation losses to enterprises

professor wuyongnian and other experts have made a series of investigations and studies on the causes and solutions of excessive acid value in cured products, and obtained data of important guiding significance. Now we introduce two representative tests

the first experiment took Nanjing fragrant tripe as the object. The results showed that there was no significant difference in the acid value between the flavored tripe with antioxidant or deoxidized packaging and the bulk control group; Cold storage can greatly inhibit the rise of acid value. This is because, in theory, the rise of acid value has nothing to do with the content of oxygen, but only with the activity of lipase, and cold storage can inhibit the activity of lipase

the second experiment took Nanjing sausage as the research object. The results show that: (1) adding soybean protein can increase the rising speed of acid value and greatly reduce the rising speed of peroxide value. The reason is that soybean protein contains flavonoids, which have obvious antioxidant effect, so they can inhibit the occurrence of fat oxidation reaction; However, from the perspective of metabolic decomposition, soybean protein is also an acidic substance, which will neutralize part of potassium hydroxide in food, so as to increase the acid value of food. (2) Vacuum packaging can inhibit the increase of peroxide value and acid value of sausage in the late storage period, but has little effect on the change of acid value in the early storage period. This result is the same as the first test result, because vacuum packaging can not inhibit the activity of lipase, so it can not prevent the rise of acid value of sausage in the early stage of storage. However, in the later stage of storage, the increase of acid value of cured products is mainly caused by the formation of acid by peroxide. Therefore, using vacuum packaging to block oxygen can inhibit the rancidity of fat in the later stage of storage, so as to prevent the rise of acid value. (3) The addition of starch can speed up the rise of acid value. The reason may be that lactic acid is produced during the anaerobic fermentation of starch, which leads to the rise of acid value. (4) The addition of D-isoascorbate sodium is difficult to inhibit the rise of acid value in the early stage of storage, but it has a certain impact on the later stage. The change of peroxide value shows a trend of rapid rise in the early stage and rapid decline in the later stage when 5 kinds of adulterated elements are selected

during the deterioration process of sausage, that is, the sensory stage from normal to yellowing and rancidity, the change of peroxide value is basically consistent with the sensory results, but the acid value is not necessarily

in conclusion, acid value is no longer a specific indicator to reflect the oxidative rancidity of cured products. In measuring the degree of oxidative rancidity of cured products, it is more appropriate to use peroxide value as an index. For this reason, Professor wuyongnian once proposed to the relevant national departments to revise the national health standards for cured products, abolish the acid value index and replace it with the peroxide value index. At present, this proposal has been adopted by the Ministry of health

5. Prevention and renewal of fat oxidative rancidity. It has also been recognized as a non-volatile organic compound (1) by the U.S. Environment Agency (EPA) and the California Air Resources Board (CARB). This is a common method in the 1970s. During operation, apply sesame oil to the surface of cured products, or immerse cured products in sesame oil, in order to isolate the products from oxygen in the air. In this way, the shelf life of the products can be extended by 1-2 months. However, this method not only consumed sesame oil and increased production costs, but also took time and labor, and was gradually eliminated later. (2) Vacuum packaging. In the 1970s, vacuum packaging was gradually used in the food industry. The key point of this method is to pack food with composite plastic bags with low permeability and vacuum the bags. Vacuum packaging can greatly extend the shelf life of food, and the antioxidant effect of cured products can be maintained for more than 6 months. (3) Deoxygenation packaging. At present, deoxygenation packaging has been paid more and more attention by food enterprises. The principle of deoxidizing packaging is that deoxidizers can generally remove the oxygen in the packaging bag within 24 hours, so that the food is in a highly anoxic state, so as to inhibit or eliminate the deterioration of food caused by various adverse reactions that require oxygen. The dosage of deoxidizer can be determined according to the length of time the food needs to be stored, which is very flexible. (4) Add antioxidants. Adding antioxidants such as sodium isoascorbate can prolong the shelf life of products by about 1 month

applying sesame oil, vacuum packaging, deoxygenation packaging and other methods to the quality assurance of cured products can greatly reduce the peroxide value of the products, but it may not have a very obvious effect on the acid value

45t III. Prevention of mildew of cured products

when the storage measures of cured products are improper, such as the warehouse is wet, not ventilated or the products are piled up, mildew will often be caused. If the mold is on the surface, the mold layer can be scraped off and the rest can be reused. If the mildew has reached the deep layer, or the mildew surface cannot be scraped off, it should be discarded

mildew of cured products mostly occurs in bulk products. Products packed in vacuum will also become moldy if the seal is not tight or the packaging bag is broken

the method of mold prevention is: bulk products should be hung in a well ventilated and dry room. Open the windows for ventilation in sunny days, and close them in rainy days. Vacuum packaging and deaeration packaging can effectively prevent mold as long as they are operated according to the specified process. (text/Liang Qinghua, Qiu Desheng)

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