| This thesis takes the low-cost pork skin as the experimental material. First degrease the pork skin clean processed in the boiling NaHCO3solution for30minutes, where the boiling NaHCO3solution is four times the quality of the pork skin. Then, wash the pork skin until pH value on its surface is seven. After cooling, process the pork skin into small pieces with5cm X3cm. Finally, make it dry pork skin in constant temperature50℃for20hours. Respectively using hot air and high temperature oil as a heat transfer medium, through the L9(33) orthogonal test to investigate the optimum of making up pork skin by hot air and by oil with color and luster, organization state, fragrance and the flexibility for sensory evaluation standard. Based on it, measure the nutrient components, the harmful things incidental3,4-Benzopyrene in these pork skins made up by above two ways, besides, assay the acid value and peroxide value in different storage location during the process of storage. Through the analysis and contrast, draw a conclusion that pork skin made up by hot air has obvious advantages than pork skin made up by oil whatever in respect to nutrients reserves, harmful generation and convenient operation. This provide the basis on the development, products and process, nutritional assessment and storage conditions of pork skin made by hot air.The orthogonal experiment results show that the best expansion process of pork skin made up by hot air like this:Firstly, roast the pork skin at an upper temperature of90℃and a bottom temperature of100℃; Then roast it until completely expanded at upper temperature and bottom temperature of both230℃. The best expansion process of pork skin made up by oil like this: First warm up it by low temperature oil for30minutes, then put it out and make the oil temperature rise to200℃, finally put the pork skin warmed up into the pot to make it expansion completely. After synthesizing each sensory evaluation of swelling pork skin and the difficulty Level of operation during swelling, draw a conclusion that pork skin made up by hot air is superior to pork skin made up by oil.The nutrition testing results show that crude protein expansion,vitamin A,content and total amino acids respectively of pork skin made up by hot air is1.25times,4.68times and2.46times as pork skin made up by oil Among them,the content of Asp,Thr,Ser, Glu, Pro,Gly, Ala,Val,Ile,Leu,Ph- e,Glu, Pro,Gly,Ala,Val,Ile,Leu,Phe,Lys,His,Arg in the pork skin made up by hot air were2.79times,3.01times,2.36times,1.99times,2.28times,2.65times,2.78times,2.31times,2.72times,3.12times,2.65times,2.75times,1.4times,2.7times as the pork skin made up by oil; The Met in pork skin made up by oil is destroyed completely. Thus it can be seen, pork skin made up by hot air retained more nutrients of pork skin, its nutritional value is higher than by oil. In addition, the content of crude fat and3,4-Benzopyrene which made up by oil were2.1times and about20times as the pork skin made up by hot air. Therefore, the grease content of pork skin made up by hot air was lower, and made less3,4-Benzopyrene in the process of expansion.It won’t cause harm to human body health.Stored pork skin made up by hot air and oil in different storage location during the same storage time. The test of rancidity results show that:the acid value from high to low is,the pork skin made up by oil which stored at room temperature in daylight increased188.37%,the pork skin made up by oil which stored in the refrigerator avoid ligh(?) conditions increased134.88%,the pork skin made up by hot air which stored at room temperature in daylight increased123.53%,the pork skin made up by oil which stored in the refrigerator avoid light conditions increased96.67%; the peroxide value from high to low is, the pork skin made up by oil which stored at room temperature in daylight increased196.77%,the pork skin made up by oil which stored in the refrigerator avoid light conditions increased160.38%,the pork skin made up by hot air which stored at room temperature in daylight increased158.06%,the pork skin made up by oil which stored in the refrigerator avoid light conditions increased135.71%. It showed that the pork skin made up by oil ranciditied more quickly than the pork skin made up by hot air with the extension of storage time in the process of preservation.And the pork skin which made up by the same method stored at room temperature in daylight ranciditied more quickly than it stored in the refrigerator avoid light conditions.That is to say the pork skin made up by hot air can stored longer,and it is better to store in the refrigerator avoid light conditions. |
