Evaluation Technique of Astringency of Walnut Based on Protein Precipitation Spectrum Analysis
[Objective]The establishment of a comprehensive evaluation system for the astringency of walnut kernel pellicle is of great significance to the breeding of fresh walnut varieties.[Methods]In this study,a comprehensive evaluation system for astringency of walnut kernel pellicle was established through sensory evaluation,kernel pellicle water immersion and protein chemical precipitation.[Results]The astringency value of the direct taste of the 6 cultivars was 5.83-9.27,which was divided into 3 categories with significant differences.When the concentration of water extract was 10 mg/mL,according to the astrin-gency value of water extract,'Fenhe 4'and'ND-2'were classified as one class,and the other 4 cultivars were classified as one class each.When the concentration of walnut kernel pellicle extract was 20 μl/mL,the absorption value of protein precipi-tation at 222 nm was the most different.The 6cultivars could be divided into 4 categories with significant differences.The cor-relation coefficients between the light absorption value of chemical precipitation and the astringency value of direct taste and 10 mg/mL water extract of walnut kernel pellicle extract were 0.96 and 0.97,respectively,showing a very significant positive correlation.[Conclusion]Under the condition of 20μl/mL and 222 nm wavelength,the astringency of walnut kernel pellicle ex-tract can be effectively evaluated by the full spectrum scanning of protein precipitation combined with sensory evaluation.
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