Husk softening and kernel characteristics of three black walnut cultivars at successive harvest dates.

摘要

Eastern black walnuts were collected weekly in Sept. and Oct. to identify a method to determine the optimum harvest date, and to develop a quantifiable colour classification system for kernels. Husk hardness, measured using a durometer, decreased over a 5-wk period. During the collection periods, the highest percentage kernel for cv. Emma K, Kwik Krop and Sparrow was recorded when durometer values (i.e. force measurements) of husks were 5.2, 5.5 and 3.4 N, respectively. Husk softening was also detected using the denting method, but the perception of denting did not consistently correspond with a specific husk hardness value. Of the 3 cultivars, Kwik Krop kernels were the most difficult to visually sort into light, medium and dark colours. Kernel LCH sum (L* + chroma + hue angle values), measured using a handheld spectrophotometer, provided a reliable colour classification for all black walnut cultivars in which light kernels had LCH sums of >=150, medium kernels had sums of 149-126 and dark kernels had values of <=125.