| Screening for processing potato lines according to potato tuber qualities and properties from varieties and advanced lines are efficient methods under current consumptions of potatoes.As the processing indexes are required for different production purposes,potato breeding schemes have to be improved and changed to suitable for different processing standards.Cooking processing and French fry processing of potato are two important processing methods in China.The research foxed on the quality characters and the relevant indexes of these two type varieties.Especially the colour qualities and textural properties,are the basis of screening for cooking and French fry processing potato variety.Of 94 potato varieties and lines selected for the test,including 88 common cultivated interspecific hybridization advanced lines,some wild introgression advanced line,and 4 processing potato varieties,such as Atlantic,Russet Burbank,Shepody,Kexin 1,and 2 main cultivars in North-west region,such as Longshu 6,Jizhangshu 8.The characteristics with agronomic traits and tuber qualities were evaluated with the correlation analysis,PCA(principal component analysis),clustering analysis.Processing potato varieties and lines were selected for tuber cooking test and French fry processing qualities test.The effect of change of the tuber components on tubers umami,colour change and texture during the cooking and French fry processing were analyzed.The tuber colour change,the hardness and softening of the tubers from before-cooking and French fry processing to after-cooking and French fry processing were determined and analyzed.The essential cooking-processing indexes and French fry processing indexes were defined.The cooking-processing indexes and French fry processing indexes and their choosing methods were studied.The cooking-processing and French fry processing varieties were screened from the tested potato varities and lines.The following results were obtained:1.Of 15 characteristics with agronomic traits and tuber qualities of 94 potato varities were evaluated,and the results indicated that the diversity at varying degrees among different potato varieties and lines in different years and different environments were displayed,among which reducing sugar content was the most abundant among these 15 traits,with 52.16% variable coefficient,indicating that the testing materials could provide the material basis for the improvement of reducing sugar content;The measurement of PCA showed that yield per plant,dry matter content,reducing sugar content,glycosidic content,tuber length-width ratio,and main stems could be used as the major indexes to evaluate characteristics with agronomic traits and tuber qualities.2.Through the analysis of the color change and texture during the potato tuber cooking processing,the value of ?E between the cooking end and seven day later after-cooking was the important colour index in potato cooking-processing.The value of ?E after the cooking could reflect the difference of tuber color change between fresh potatoes and cooking ones.There was no significant difference when the value of ?E was less than 15 hours.The value of ?E between the cooking end and seven day later after-cooking showed the color change as a result of oxidation,and the color texture of the tuber after seven day later after-cooking was in a stable state and could reflect the color texture after the processing.The major component influencing the color change was chlorogenic acid contents,which could react with the metal iron in the tuber and generate stable compounds that made the tuber black.Citric acid and ascorbic acid were good kind of antioxidants,capable of preventing the oxidization of the fresh potatoes because of polyphenol oxidase,thus positively stablizing the color of tuber after cooking.Among 14 varieties,Russet Burbank?0724-58?0716-22 after 7 days cooking have the smallest color change.3.Through the analysis of the texture qualities during the cooking processing,the tuber softening difference was another important index of potato cooking-processing.The hardness of tuber was correlated to the contents of dry matter,fiber and pectin content,and the contents of dry matter was not the only factor to influence the hardness of the fresh potatoes.The softening of the tuber after cooking was correlated to starch dextrinization,pectin degradation,cell wall breakage and degeneration of cell membrane.The present results indicated that the varieties Russet Burbank,Shepody and lines 0724-58,0712-66 are the better softening potato varieties and lines.The potato lines 0744-8 and 0722-26 are the better hard lines.4.Through the evaluation of the color change of tubers during French fry processing,the value of ?E was consistent with the color change of French fries.The correlation analysis of the value of ?E and the tubers components indicated that the major factors influencing the color change of French fries were sucrose,glucose,and chlorogenic acid.The correlation analysis of three primary colors L?a?b and the contents of tuber components indicated that ascorbic acid was significantly correlated to the value of L,and such reducing sugar as sucrose and glucose,sucrose sugar and chlorogenic acid were most significantly correlated to the value of a,with citric acid is more extent influence on the value of a than that of b.The lowest level of ?E of the varieties of Shepody,Russet Burbank,lines 0719-32 and 0716-39 under 4 different storing places indicate that these materials have the strongest resistance to brown degeneration.5.The evaluation of the texture qualities of tubers during the French fry processing showed that both the hardness of fresh potatoes and that of the French fries were significantly correlated to the content of starch in the tuber.The major reasons accounting for the lowering hardness of fresh potatoes after long-period storing were water loss and starch degradation.The present results indicate that the varieties Russet Burbank,Shepody and lines 0724-58,0712-66 possess the highest content of dry material and starch,stronger resistance to brown degradation,and thus they are the better varieties and lines for potato processing. |
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