Everyone knows that fried food is crisp and delicious, but few people know what elements will change in deep frying, and what correlation between elements and other issues. Today, we will give a brief analysis of these problems.
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The experimental results show that during deep frying, oil exposed to oxygen and water for a long time and at a higher temperature (180 C or above) will undergo obvious physical and chemical changes, such as oxidation, hydrolysis, polymerization and fission. At the same time, the contents of fatty acids and vitamins will also occur during deep frying. Change. The frying reaction depends on many factors, such as the type of frying oil, food materials, raw materials of frying pan and so on. Of course, in the frying process, there will also be some bad substances, such as polar substances, free fatty acid and trans fatty acid content, and the polar substance content is higher. Correspondingly, the content of polar substances in better quality and fresher oils is lower. It was found that the change of total polar substance content was closely related to acid value, color and frying time. Generally speaking, one of the ways to identify whether a frying oil should be discarded is to determine whether the content of polar substances is higher than 27%.
There are many kinds of frying oil, among which palm oil, olive oil and camellia seed oil are common frying oil. We take these three oils as examples to analyze and discuss the relationship between acid value and polar substance content.
The data of acid value, fatty acid and polar substances were tested through experiments (among them, the acid value was measured by Zhongtian brand acid value fast test kit, which has the advantages of convenience, rapidity and precision). The results showed that the acid value of olive oil was significantly higher than that of palm oil and camellia oil during frying, while that of palm oil was significantly higher than that of Camellia oil. At the same time, the experimental results also tell us the fact that there are water, steam, oxygen and other substances in the frying process, so there will be complex chemical reactions between frying oil and fried food, so the acid value will increase with the increase of frying times, which is also often used to uate the quality of frying oil. One of the reasons for regulatory indicators.
On the other hand, as a chemical parameter of high-temperature degradation of reactive frying oil, polar substances will increase significantly with the increase of frying cycle number again in this experiment. Experiments show that during frying, if peroxide and hydroperoxide decompose, the frying oil will eventually form short-chain carboxylic acid, aldehyde, ketone, alcohol and non-volatile products, which will lead to polar compounds in the frying oil.
The experimental analysis shows that the formation of polar compounds has a strong correlation with the occurrence of primary and secondary oxidation. In the frying process, the chemical reaction of water, steam and oxygen promotes the acid value of frying oil and fried food to increase continuously. The comparative data also show that the formation of polar substances and the increase of acid value depend on the occurrence of oxidation reaction in frying oil. The higher the content of polar substances, the higher the acid value of frying oil. The change between them is linear.
The conclusion is that there is a correlation between acid value and polar substances in frying oil. This is only a shallow analysis, if we need to get deeper research conclusions, we need to continue to conduct more in-depth experiments. I look forward to more in-depth discussions with you in the future.
(Note: Part of the content is quoted from the 11th issue of Food Industry Science and Technology, 2015-ldquo; Research and Discussion-rdquo; Author: Li Yang, Cao Liang, Ma Wenjun, Huangli, Qi Baokun, Jianglianzhou)
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