Relationships Among Reducing Sugar, Asparagine, and Chip Color in Wild Solanum Species

Abstract

When stored at temperatures less than 10 °C, tubers of all cultivated potatoes exhibit cold-induced sweetening (CIS) during which starch degrades to sucrose, glucose, and fructose. Upon frying at high temperatures, the reducing sugars (Fru, Glu) interact with free amino acids via the non-enzymatic Maillard reaction to form dark-colored chips that are unacceptable to consumers. In addition, scientists recently discovered that the toxic chemical acrylamide is also produced during frying. Although storage at warmer temperatures reverses CIS and circumvents dark chip production, the probability of storage loss due to shrinkage and disease increases. Wild Solanum species form the backbone of many potato-breeding programs. In this study, we evaluated 36 different plant introductions (PI) including 20 different species, grown in Madison and Rhinelander, Wis., to identify germplasm resistant to CIS for genetic analysis. After storage for 2–3 months at 4 °C, tuber sugar and amino acid content were analyzed via HPLC and slices were fried to determine chip color. Sugar and chipping data support previous research indicating CIS resistance in S. okadae, S. raphanifolium, and S. phujera. Interestingly, some germplasm selections with high reducing sugar content produced light-colored chips, indicating exceptions to the typical correlation between reducing sugar content and chip color. Genetic bases to these exceptions are under evaluation.