Study on harvest period of fresh walnut'Lipin No.2'
[Objective]In order to solve the problem of resource waste caused by the low quality of early harvest of fresh walnuts,this study explores the dynamic changes of various quality indexes of fresh walnut fruit at different growth stages.The analysis and evaluation of the comprehensive quality can clarify its growth and development law and propose a suitable fresh harvest period,which provides a reference for the timely harvest and resource utilization of fresh walnuts.[Method]In this experiment,the fresh walnut variety'Lipin No.2'from Yicheng County,Shanxi Province was used as the test material.Samples were taken at 82 d,92 d,102 d,112 d,123 d and 133 d after flowering,for a total of 6 times.The contents of postharvest fruit quality indexes were determined by spectrophotometer,Kjeldahl nitrogen analyzer,soxhlet extraction,gas chromatography,amino acid analyzer.The LSD multiple comparison method was used to test the significance of the difference between the data at different growth stages,and the quality of walnuts at different growth stages was comprehensively evaluated by principal component analysis.[Result]With the growth of the fruit,the appearance indexes include three diameter mean of green fruit,three diameter mean of nuts,fresh weight of green fruit,fresh nut weight,the dry weight of the nut,the fresh weight of the walnut kernel,the dry weight of the walnut kernel and the ratio of the diameter of the kernel all increased first and then tended to be relatively stable.The appearance quality indexes reached a relatively high level at 112 days after flowering,the fruit size and quality were basically stable.In terms of sensory quality,the evaluation scores of taking kernel difficulty,seed coat color and seed coat peeling difficulty gradually decreased,the kernel plumpness score gradually increased,the kernel aroma and flavor scores first increased and then decreased.The comprehensive score of sensory quality(2.8～4.5 points)increased first and then decreased,the highest score was 4.5 points at 112 days after flowering,and the sensory quality was the best.In terms of nutritional quality,the contents of kernel rate,fat,protein,stearic acid and oleic acid showed an overall upward trend,while the contents of water content,palmitic acid,linoleic acid and linolenic acid showed an overall downward trend.The contents of soluble sugar,fructose,total amino acids,total essential amino acids,four kinds of flavor amino acids(umami,sweet,bitter and aromatic),P,Zn and Ca elements decreased first and then increased.The content of tannin showed a trend of increase-decrease-increase,and the content of Mg and Fe elements showed a trend of decrease-increase-decrease.At 112 days after flowering,the contents of some nutrients such as protein,soluble sugar,fructose,linoleic acid,P,Mg and Zn accumulated rapidly and reached a high level.The results of principal component analysis of the comprehensive quality of fresh walnut at different growth stages showed that the score was 0.53 at 112 days after flowering,which was close to the highest score of 0.57 at 133 days after flowering,and the comprehensive quality had reached a higher level.[Conclusion]112 days after flowering is the suitable harvest time for fresh walnut of'Lipin No.2'.The visual index is that the color of inner fold wall and septum of core shell develops from white to yellowish brown,which can provide reference for fruit farmers to harvest fresh walnut.
fresh walnutqualityprincipal component analysiscomprehensive evaluationharvest time
万方数据
