Research On Quality Variation Of Fried Stolephorus Commersonnii And Its Mixture Of Frying Oil

Stolephorus commersonnii is a marine fish,is a kind of rich in coastal areas of aquatic small fish,with high protein,low fat,unique taste and low price advantages,it is usually used as raw materials for processing into recreational fish products.At present,most of the industrial processing is deep-fried operation.The deep-fried process can not only improve the appearance and color of products,but also make them more crisp and delicious and increase the appetite.However,the long-term intake of high-fat food has been questioned by researchers,and the cost of industrial frying oil remains high.Therefore,this thesis studied the effects of frying process parameters and pretreatment methods on the quality of dried fish?especially the oil absorption rate?,and explored the deterioration trend of soybean oil to explore the appropriate process operation.Finally,through the combination of different oils,the frying oil could be used more efficiently and safely.The details are as follows:?1?The effects of frying temperature and time on the mass transfer dynamics and quality of Stolephorus commersonnii were studied.Dried Stolephorus commersonnii is best fried until the moisture content is 24.0%,and at 200?,180?and 160?,it was necessary to fry100s,180 s and 307s,respectively.The exponential equation based on fick's second law and first-order kinetic equation perfectly fit the water loss and oil absorption in the process of frying Stolephorus commersonnii.The change curve of the central temperature showed that the central temperature of the Stolephorus commersonnii was more than 100?due to the oil permeating into the fish during the latter stage of frying,and the oil temperature was lower than 20??30?in the frying balance.The low-field NMR results showed that the changes of free water,adsorbed bound water,protein bound water,and the degree or content of oil and material were consistent with the curves of water loss and oil absorption.When frying to optimum moisture content of 24.0%,the?E value of Stolephorus commersonnii is 28.6?32.1,the hardness is 28100?34500 g,the chewiness is 18500?20700,the surface hardness is1080?1360 g,the toughness is 1212?1466 g·s.?2?The effects of specific surface area,frying temperature,frying time,initial moisture,type of coating film,variety of oil and oil quality on the moisture content and oil content of fried Stolephorus commersonnii were studied through response surface design and BP neural network model.The results showed that the Box-Behnken test showed a very significant negative correlation between water content and oil content?P=-0.899?.The specific surface area of the Stolephorus commersonnii,the type of coating and the initial moisture content all had a great influence on the moisture content and oil content of the product.BP neural network is trained and the 7-7-2 network model structure is established with the highest prediction accuracy.The order of the comprehensive influence of various factors was as follows:specific surface area?100%?>coating type?49.8%?>initial moisture?37.6%?>frying time?29.8%?=frying temperature?29.8%?>oil quality?28.1%?>oil variety?16.0%?.The neural network model was used to simulate the orthogonal design data,the results showed that reducing the specific surface area of the Stolephorus commersonnii,reducing the initial water content,and preapplying 0.5%sodium alginate could significantly reduce the oil content,the variety and quality of the oil had no obvious influence on the oil content.The analysis of simulation results is highly consistent with the analysis of actual response surface data,indicating that the neural network model can be applied to the analysis of index prediction.?3?The effect of different frying temperature and time on the deterioration of soybean oil was studied,on this basis,soybean oil,high oleate rapeseed oil and palm oil were used as the base to prepare the mixture.The frying life of soybean oil was evaluated by chemical index:in the group of 200?,15 h;in the group of 180?,21 h;and in the group of 160?,28h.Combined with the mass transfer kinetics curves of fried Stolephorus commersonnii at three temperatures,it was concluded that the yield of fried Stolephorus commersonnii at200?was the highest and the comprehensive cost of oil was the lowest.Visible absorption spectrum shows that the higher the frying temperature and the longer the frying time are,the larger the initial value of the spectrum is and the steeper the decline slope is,the spectral curve changes from exponential attenuation type to anti-s type.Low field NMR,according to the results of each group of relaxation spectra of frying oil were detected by two relaxation peaks,and the parameters T₂₁1 and S₂₁1 and fry in the process of soybean oil is closely related of quality deterioration.The smoke points of soybean oil,high oleate rapeseed oil and palm oil were all higher than 210?,indicating the feasibility of frying at 200?.The thermal stability of palm oil was much higher than that of other common vegetable oils,and soybean oil had the worst thermal stability.Comprehensive evaluation of frying life of each grease?200??:palm oil was fried for 30 h,soybean oil was fried for 15 h,and high oleate rapeseed oil was fried for 21 h.The regression equations of OSI and three oils were obtained through mixing design,and the relationship between SFA,MUFA,PUFA and oxidation rate of the complex oils and their components were obtained according to their fatty acid composition and binding literature.According to the“programming solution”in the computer,the complex oils with a balanced composition of seven fatty acids were obtained?T₁?T₇?,which satisfied the oxidation stability index of the oil at no less than 4.5 h,the content of saturated fatty acids at no more than 25%,the content of monounsaturated fatty acids at no less than 40%,and the oxidation rate at no more than 49.42.Four compound oils with better oxidation stability and thermal stability?T2,T4,T5 and T7?were finally screened out.Finally,the frying experiment was carried out on four selected compound oils,which showed that the frying stability of the four compound oils was significantly better than that of soybean oil,and the T₄ compound oil with the best frying performance was selected comprehensively.Its composition was soybean oil:high oleate rapeseed oil:Palm oil=6.99%:49.56%:43.45%.