Abstract
Abstract: China is one of the world's largest countries in potato production and consumption, and the quality of processing products was significantly affected by characteristics of raw materials. In order to research the relationship of raw materials and their processed products (potato chips, French fries and potato flakes), 44 common potato cultivars grown in domestic were collected and tested in China National Food Machinery Quality Supervision & Inspection Center and Chinese Academy of Agricultural Sciences from Sep. 2012 to Dec. 2014. Fourteen indicators including eye numbers, shape index, mean weight, reducing sugar, total sugar, starch, moisture, dry matter, ash, total soluble solids, vitamin C, protein, fat and crude fiber of raw potatoes were analyzed according to China national or industrial standards. Analysis of variance revealed significant differences and great variation among most of indicators. Three kinds of products including potato chips, French fries and potato flakes were processed using 44 cultivars collected respectively. The quality indicators of processed products were also tested in the laboratory. For potato chips, four indicators including sensory evaluation, protein, crispness and Hunter whiteness were tested. For French fries, four indicators including sensory evaluation, protein, hardness and Hunter whiteness were tested. For potato flakes, four indicators including sensory evaluation, protein, viscosity and free starch ratio were tested. Analysis of variance also revealed great variation among indicators of three kinds of processed products. Using the maximum - minimum normalized method, multiple quality indicators of potato chips, French fries and potato flakes were calculated into a one-dimensional evaluation indicator in order to establish a representative model. Each comprehensive indicator had a significant correlation with four original indicators of processed products. With stepwise regression method, significant indicators of raw materials were selected to establish the model of processed products, while insignificant indicators were eliminated to reduce the redundancy of models. Based on three calculated comprehensive indicators and 14 indicators of raw materials, comprehensive quality evaluation models of potato chips, French fries and potato flakes were established respectively. The results showed that, the comprehensive quality of potato chips were remarkably influenced by the reducing sugar, ash, protein, eye number and total soluble solids of raw potatoes; the effect of potato chips' comprehensive quality evaluation model were: the coefficient of determination R2=0.802, adjusted R2=0.776, std. error of the estimate =0.101. The comprehensive quality of French fries was remarkably influenced by the moisture, protein, reducing sugar and mean weight of raw potatoes; the effect of French fries' comprehensive quality evaluation model was: the coefficient of determination R2=0.731, adjusted R2=0.704, std. error of the estimate =0.141. The comprehensive quality of potato flakes was remarkably influenced by the starch, eye number and total sugar of raw potatoes; the effect of potato flakes' comprehensive quality evaluation model was: the coefficient of determination R2=0.705, adjusted R2=0.682, std. error of the estimate =0.170. Three comprehensive quality evaluation models with high fitting degree and small error were reliable in practical application and could be used to evaluate the comprehensive quality of potato processing products. Calculated by K-means clustering algorithm, 44 potato cultivars were divided into three categories as the most suitable, suitable and unsuitable categories; the results showed that 15 cultivars (e.g., Atlantic, Hertha) were the most suitable for processing potato chips, 10 cultivars (e.g., GLKS-58-1642.4, Zhuanxinwu) were most suitable for processing French fries and 10 cultivars (e.g., Red Gold, Liangshu 17th) were most suitable for potato flakes. The K-means clustering result which was consistent with practical application was instructive and meaningful in screening special potato cultivars for processing. Systematic research of the relationship between raw materials of different potato cultivars and their processed products (potato chips, French fries and potato flakes) is of certain referential value to promote the development and upgrading of Chinese potato processing industry.
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