Effects of Growing Environment and Storage Conditions on Physicochemical Characteristics and Processing Suitability of Two Potato (Solanum tuberosum L.) Varieties Harvested at Different Maturity Stages

Abstract

Potato (Solanum tuberosum L) popularly referred to as a “hidden treasure” is the most consumed commodity among the non-grain foods globally and the second most important food crop after maize in Kenya. Two potato varieties namely Markies and Shangi have been certified by KEPHIS and released to potato farmers countrywide through registered seed merchants for production purposes. However, their suitability for industrial application is not sufficiently established. The objective of this study was therefore to determine the effect of growing environment on processing suitability of the two potato varieties harvested at different maturity stages, postharvest storage effects, and value addition through shelf-life extension of fresh-cut potato slices. The potatoes were obtained from Githioro and Kipipiri locations in Nyandarua county where they were all cultivated under similar conditions. Potato tuber physicochemical characteristics were evaluated at 3 stages of maturity, tuber storability was evaluated at ambient temperature of 18℃ at 85% RH in a dark room) and cold storage (5℃ at 95% RH). The effect of different treatments on the shelf life extension of the fresh potato slices was also determined. The results revealed significant (P < 0.05) effects on the physical characteristics due to the interaction between variety and maturity stages. A significant (P=0.047) difference was observed in the texture, (P= 0.035) in lightness (L*), and (P=0.004) in redness (a*) color parameters. Kipipiri location produced significantly larger tubers in size and weight (P < 0.05) at the 3rd maturity stage. There were significant (P < 0.05) differences in starch, (P=0.004) ascorbic acid, reducing sugars (P=0.003), glucose content (P=0.006), and sucrose contents (P=0.035) across the 3 maturity stages tubers harvested from Githioro location. There was a significant difference (P < 0.05) in starch, (P < 0.05) ascorbic acid, glucose content (P=0.029), and fructose content (P=0.048) in the two storage conditions. The shelf life of fresh-cut potato slices was extended for 6 weeks under cold storage at 5℃ at 95% RH in combination with vacuum sealing and ascorbic acid treatment at 2% ascorbic acid concentration. In conclusion, both varieties, Markies, and Shangi can be good sources of raw material for the potato processing industry. Variety, maturity stage, and growing environment influence the quality characteristics of the potatoes. The shelf life was extended for 6 months at 2% ascorbic acid concentration treatment being the optimum conditions for the most acceptable value-added products.