Hygienic requirements for edible fats and oils
作者：admin 点击次数：139 发布时间：2025-06-11
(1) Oil processing and quality
The commonly used methods for oil processing include pressing, smelting, leaching and centrifugation. The pressing method is often used for the extraction of vegetable oil, and there are two types: cold pressing and hot pressing. The smelting method is often used in the processing of animal fat, and often assisted by the pressing method, the lipase and oxidase in the animal tissue are completely destroyed after boiling, even if there is a small amount of residue oil, it will not be rancid due to the action of oxidase, which is a more common processing method in hygiene, but the temperature is too high will increase the content of free fatty acids in the oil. The leaching method is to extract the oil in the tissue with organic solvent, which is often used in the production of soybean oil in China, and the oil produced by this method almost does not contain residue, the oil is not easy to rancidity, but the solvent is not easy to be completely removed, and toxic compounds such as benzene and polycyclic aromatic hydrocarbons often have residues. Centrifugation is often used for cream separation, but also for auxiliary processing of purified edible oils, which can reduce the content of grease residues. In short, the main health problems in edible oil processing are to prevent or reduce the retention of animal and plant tissue residues, try to avoid microbial contamination, and pay attention to the purity and residue of solvent in the production of oil by leaching method. In production, it is necessary to select appropriate methods and pay attention to the combination of various methods to improve the hygienic quality of products.
(2) Rancidity and prevention of oils and fats
1. Causes of rancidity in oils
There are two causes of rancidity of oils and fats: one is the biological hydrolysis process, that is, the hydrolysis caused by the residues of animal and plant tissues and enzymes produced by microorganisms; The second is the chemical changes that occur under the action of air, water, sunlight, etc., including the hydrolysis process and the automatic oxidation of unsaturated fatty acids. The auto-oxidation of fats is the main cause of rancidity in fats and fat-rich foods. Under the action of sunlight and air, catalyzed by copper and iron, unsaturated fatty acids are first oxidized into peroxides, and then decomposed into odorous aldehydes and aldehyde acids. In the process of rancidity of oils and fats, biological hydrolysis and chemical oxidation often occur at the same time, and may also be mainly manifested as one.
2. Consequences of rancidity of oils and fats, after rancidity of oils, strong unpleasant tastes and odors are produced, which change the sensory properties of oils; The content of free fatty acids increases, and the acid value increases; The peroxide content increases and the peroxide value increases; The content of aldehydes and ketones increased, and the carbonyl valence increased. Rancidity reduces the nutritional value of fats, such as the oxidation and destruction of unsaturated fatty acids, and the destruction of fat-soluble vitamin A, vitamin D, and vitamin E. The oxides produced after rancidity have a destructive effect on the body's enzyme system, such as succinate oxidase and cytochrome enzyme. In addition, long-term consumption of rancid oil in animals can cause symptoms such as weight loss, developmental disorders, and liver enlargement, and some rancid oils and fats can cause acute poisoning and tumors in animals.
3. Measures to prevent rancidity of oils and fats
Rancidity of oils and fats is related to its own purity, various environmental factors in the processing process and storage, and the prevention of rancidity is the primary problem to ensure the hygienic quality of oils and fats, and runs through the whole process of processing, storage and eating. In the process of oil processing, the purity should be ensured, animal and plant residues should be removed, microbial contamination should be avoided as much as possible, and enzyme activity should be inhibited or destroyed; Water can promote microbial reproduction and enzymatic activities, and the moisture content should be controlled below 0.2%. High temperature will accelerate the automatic oxidation of unsaturated fatty acids, low temperature can inhibit microbial activity and enzyme activity to inhibit automatic oxidation, and oil should be stored at low temperature as much as possible. Sunlight and air have an important impact on the deterioration of grease, ultraviolet, purple, blue and other rays can accelerate the oxidation of grease, and long-term oil storage should be sealed, oxygen, and shading containers. Metal ions such as iron, copper, and manganese can catalyze fat oxidation, and contact with metal ions should be avoided during processing and storage. The application of antioxidants can effectively prevent rancidity of oils and fats, prolong the storage period, and commonly used are vitamin E, butyl hydroxyanisole (BHA), dibutyl hydroxytoluene (BHT) and propyl gallate, but attention should be paid to control. (3) Edible oil pollution and the natural harmful substances contained therein
1. Mycotoxins
When the seeds are contaminated with mold and its toxins, the oil produced also contains toxins. Peanuts are most susceptible to Aspergillus flavus contamination, as can other oilseeds, cottonseeds and rapeseeds. Aflatoxins can contain thousands of micrograms per kilogram of aflatoxins in oil from heavily contaminated peanuts. The more effective detoxification method is alkali refining and adsorption, alkali refining method consumes more oil, the operation is cumbersome and easy to rancidity, and the adsorption with white clay or activated carbon consumes less oil and has no effect on the edible value. China stipulates that the content of aflatoxins in corn and peanut oil shall not exceed 20u/kg, and other vegetable oils shall not exceed 10wg/kg.
2. Polycyclic aromatic hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs) are mainly caused by the smoking and drying of oil seeds, solvent residues when lubricating oil is mixed or leached during pressing, high-temperature thermal accumulation of repeated oil and industrial pollution during crop growth.
3. Gossypol
Gossypol is a toxic substance in the pigment gland of cottonseed, including free gossypol, gossypol purple, phenol green 3, long-term consumption of raw cottonseed oil can cause chronic poisoning, manifested as skin burning, no sweat, dizziness, heart, skin flushing, shortness of breath, but also affect reproductive function. The free gossypol content of cottonseed oil produced by cold-pressing method is high, so it is not suitable for direct consumption; The content of free gossypol in the oil of the hot method is greatly reduced, and it is generally only 1/10~1/20 of the cold pressing method. Gossypol can form water-soluble sodium under alkaline conditions and be removed, alkali refining or refining can reduce gossypol content to 0.015%, China stipulates that the free gossypol content in cottonseed oil does not exceed 0.02%.
4. Glucoside glucoside is commonly found in cruciferous plants, and the content is higher in rape. Glucosinoside is decomposed into thiocyanate, isothiocyanate and nitrile under the action of glucoglucosobylase in plant tissues, which is very toxic and can inhibit animal growth. Thiocyanide can block the absorption of iodine by the thyroid gland and has a goiterogenic effect, which can generally be removed by its volatile heating.
5. Erucic acid
Erucic acid is a docosanic monounsaturated fatty acid, rapeseed oil contains 20%~50%. Animal experiments have shown that erucic acid-containing oils can accumulate fatty acids in animal myocardium, cause myocardial monocyte infiltration, and cause fibrosis of myocardial cells, and also affect animal growth, development and reproductive function. The European Community stipulates that the erucic acid content of edible oils shall not exceed 5%. 6. Toxicity of high-temperature heating oil
The toxicity of oils and fats after heating at high temperatures is generally believed to be mainly caused by various polymers produced by unsaturated fatty acids. The dimer formed by the polymerization of two unsaturated fatty acids can be absorbed by the body and is highly toxic, which can cause growth arrest, liver enlargement, and reproductive dysfunction in animals. Glycerol pyrolysis forms compounds such as acrolein, which have a foul smell and irritating effect on mucous membranes.
In order to prevent the harm of high-temperature heating grease to the body, the temperature should be avoided as much as possible ...