RELATIONSHIPS BETWEEN FRY COLOR AND SUGAR CONCENTRATION IN STORED RUSSET BURBANK AND SHEPODY POTATOES

Relationships between french fry color and sugar composition of Russet Burbank and Shepody potatoes harvested at various chemical maturities (i.e. sucrose concentrations) and exposed to various temperature regimes during 8 to 9 months storage were examined. Combined data from 3 years of study showed fry color to be more closely associated with glucose during 8 C storage for Russet Burbank (r(2)=0.65) and Shepody (r(2)=0.62) than with fructose, total reducing sugars, sucrose, or total sugars. Glucose >1.6 mg g(-1) in Russet Burbank and >1.2 mg g(-1) in Shepody resulted in fries which were too dark to be eligible for maximum bonus paid by processors for good color. Russet Burbank harvested with sucrose >3.1 mg g(-1) and Shepody harvested with sucrose >1.6 mg g(-1) and preconditioned for 14 d at 15 C before storage at 8 C accumulated enough glucose in storage to result in fries which were darker than was acceptable for maximum bonus payment. Preconditioning at 15 C for 70 d was necessary to prevent Russet Burbank with sucrose of 3.9 mg g(-1) at harvest from accumulating unacceptably high glucose during storage. Glucose determined with enzymatic test strips was in close agreement with that by HPLC for both cultivars. The test strips could be used to estimate fry color of Russet Burbank.