Role of reducing sugars and amino acids in fry colour of chips from potatoes grown under different nitrogen regimes

Abstract

AbstractThe use of total reducing sugars to predict the fry colour of potato chips may lead to anomalous results because both sugars and amino acids are involved in the Maillard reactions responsible for the production of the colour of fried potato. To clarify the roles of both sugars and amino acids, potatoes were grown under different levels of nitrogen fertilisation to induce different levels of free amino acids and sugars. The potatoes were harvested at maturity and stored at 10°C for up to 10 months, which served to induce further changes in both sugar and amino acid content. At harvest and at intervals during the storage period, potatoes were analysed for total reducing sugars, glucose, fructose and amino acids. Chips from the potatoes were fried and their colour was scored by comparison with standard colour cards. Potatoes grown under high nitrogen had lower amounts of free sugar at all times, and consequently‐tended to have lower colour scores. However, in high nitrogen potatoes there was more colour per unit of sugar indicating that amino acids may be playing a synergistic role. Statistical analysis of the data indicated that around 90% of the variation in the colour could be accounted for by variation in the sugars but that 98% of the variation could be accounted for by including amino acids in the regression analysis.