Threshold sugar concentrations in snowden potatoes during storage

The suitability of potatoes for processing into potato chips is dependent on chip color, and internal and external defects. Concentrations of reducing sugars, and more specifically glucose, have been used as a quantitative indicator of acceptability of potato for chipping. The research reported here investigated the correlation between sugar concentrations and chip color, and the variability of sugar concentrations between samples and sample locations. Three potato storage research bins, each with an independent air handling and control system, were located inside of commercial potato storage bins. Snowden potatoes were harvested in the fall of 1992 and stored at different temperatures in the bins through late March, 1993. The potatoes were sampled bi-weekly during the storage period, and the samples were analyzed for sugar concentrations (sucrose and glucose) using a YSI model 2700 sugar analyzer.1 The results indicated that a Snowden potato sample with a glucose concentration less than 0.0075%2 (fresh weight basis) will have a 90% probability of having an acceptable Snack Food Association color score of 1.5 or lower. Lower numbers indicate whiter chips which are generally preferred by chip producers. Similarly, a sample with a glucose concentration of 0.01% will have a 90% probability of having a color of 2 or lower. Based on tubers sampled from four heights within the storage bins, samples from the top of a potato bin will provide a representative sample as long as recommended storage procedures are followed, and potato pulp temperatures are similar throughout the storage.