The Quality Deterioration Of Fried Food During Storing Process

Fried food were easy to oxidize during the storage, which cause the reduction ofnutritional value and taste. The study on oxidation deterioration of the fried food wasimportant. At present, most researches of the fried food are based on single raw material orsingle processing method. However, little attention was paid on the comparative study of thefried food from different materials or different processing methods. In the other hand, theanalysis method on the evaluation of oil quality during the storage mostly focused on thetraditional methods, such as acid value, peroxide value, anisidine value, columnchromatography etc. This paper compared the oxidative degradation of fried food of differentraw materials and different processing methods. What’s more, the low field NMR techniqueswere used to study the relationship of water distribution and oxidative degradation of oil.Firstly, in order to study the isothermal moisture absorption properties of fried food, fourkinds of fried food including vacuum fried lotus seed, vacuum fried carrot chips, atmosphricfried carrot chips and atmosphric fried potato chips were employed to investigate the isothermadsorption in this thesis. The data of4kinds of fried food were fitted to the5kinds ofisothermal adsorption model, which were commonly used for the processed agriculturalproducts. The results showed that the Peleg model and GAB model were suitable to describethe isothermal moisture absorption properties of Fried food. For the Peleg model the order ofthe fitting was vacuum fried carrot chips, vacuum fried lotus seed, atmosphric fried carrotchips, and atmosphric fried potato chips. In this work the monolayer moisture content of thefour kinds of high-fat food were determined according to the GAB model. The monolayermoisture content of4kinds of fried food decreased with the increase of storage temperature.Secondly, in order to study the oxidative deterioration of fried food during storing process,four kinds of fried food were used as test materials. The changes of acid value, peroxide value,p-anisidine value, ε and the relative content of various fatty acids were discussed with thestorage time extended. The results showed that At the storage time of50days, the relativecontent of linoleic acid of the four kinds of fried food was changed as the follows: the vacuumfried lotus was decreased by10.57%, the atmospheric fried potato chips was decreased by10.63%, vacuum fried carrot chips was decreased by5.88%and atmospheric fried carrots wasdecreased by7.23%. Compared to the cellulose-rich raw material, the starch-rich material wasmore easily to oxidize. The correlation analysis between the dielectric constant and otherindexes （acid value, peroxide value, p-anisidine value） showed that there are significantpositive correlation between the dielectric constant and other chemical indexes （p<0.05）.Therefore, the dielectric constant could be used as an index to evaluate the degree ofoxidation deterioration of fried food. Finally in order to study the distribution of fat and moisture in the fried food and itsdeterioration. Three kinds of fried food vacuum fried lotus seed, atmospheric fried carrotchips, and atmospheric fried potato chips were used as the test samples. The changes of theirT2were discussed at40°C with the storage time extended. The results showed that the ratioof bound water and free water in atmospheric fried carrot chips decreased by8.55, the ratio ofbound water and free water in atmospheric fried potato chips decreased by5.85, the ratio ofbound water and free water in vacuum fried lotus seed creased from2.01to4.21and thendecreased to1.52. The relaxation time of fat existed in the form of T23and T24did not change.The trend of O/P and S₂₃/S₂₄showed a positive correlation.