Relationship of Soluble Solids and Berry Weight to Airstream Grades of Natural Thompson Seedless Raisins

Abstract

In 1973, Thompson Seedless grapes were harvested on 2 dates from 7 vineyards at Davis and in Fresno and Madera Counties. Berries were sampled from each harvested cluster, weighed individually, and then crushed for total soluble solids content (9). The remaining fruit was sun-dried on trays. The raisins were graded with an airstream sorter, and the grades were correlated with fresh-fruit data using stepwise regression and correlation analyses. Mean soluble solids content (°Brix) and fresh berry weight contributed in a significant way to the correlations with raisin grades, but standard deviations did not. When the fresh-fruit data were segregated for a negative or positive relation between soluble solids and berry weight, high correlations were developed between percent B and better raisin grade (Y) and °Brix and berry weight (X). When b was positive R² = 0.998^* and Se = 1.8; when b was negative, R² = 0987^** and Se = 2.0.