Influence of N and K fertilizers on contents of reducing sugars and free amino acids in potatoes. Significance for acrylamide contents in potato chips.

摘要

Influence of combinations of N + K fertilizers during cultivation of otatoes on acrylamide concn. in potato chips was studied. Potatoes cv. Agria were grown using 3 K fertilizer levels (1.0, 3.0 or 5.0 g/pot as K2SO4) and 4 N levels (0.8, 1.2, 1.6 or 2.4 g/pot as NH4NO3), harvested at physiological ripeness and stored for 5.5 months at 12degC. Samples were analysed at intervals for concn. of reducing sugars, total free amino acids, asparagine and general quality characteristics. Samples from 3 of the fertilizer combinations (K/N at 1.0/2.4, 3.0/1.6 and 5.0/0.8 g/pot) were then processed into potato chips and analysed for degree of browning and acrylamide concn. Results showed that high levels of K combined with moderate levels of N fertilizers had a positive effect on many quality parameters including improved mechanical firmness, reduced catechol oxidase activity and increased citric acid contents. Contents of DM and reducing sugars decreased with increasing K fertilizer level, thus reducing risk of acrylamide formation. High levels of N fertilizer however increased concn. of both reducing sugars and asparagine in potato tubers, resulting in greater degree of browning and markedly increased concn. of acrylamide in potato chips. Increasing the K:N ratio from 0.4:1 to 1.9:1 was sufficient to reduce acrylamide concn. of potato chips from 853 mug/kg to below the current signal value of 540 mug/kg (DM basis).