IDENTIFICATION OF PRE-HARVEST BIOMARKERS IN POTATOES FOR IMPROVEMENT OF POST-HARVEST MANAGEMENT OF FRY COLOUR

Abstract

Potatoes (Solanum tuberosum) for processing of crisps and french fries have special quality demands compared to ware potatoes. A low amount of reducing sugars in the tubers is necessary to prevent the non-enzymatic Maillard reaction between sugars and free amino acids during frying. The Maillard reaction is responsible for development of undesirable dark coloured compounds with bitter taste. Moreover, it was recently discovered that intermediates in the Maillard reaction were responsible for the formation of the potential carcinogenic compound acrylamide. Large variation in suitability of potatoes for processing is often seen. Potatoes of the same cultivar from one field/lot may accumulate sugars much faster during storage than potatoes from another field/lot. Reliable biomarkers for long-term storability must be identified to improve the management of potatoes going into storage. A three-year study with the potato crisp cultivar 'Saturna' was conducted. Development in crisp colour during storage was evaluated in relation to different vine killing dates during final growth and to the variation observed between commercial fields. Samples were also taken weekly during final growth in order to characterize the physiological tuber maturity at harvest. The results showed that high benefits might be obtained at the potato processing companies if potatoes could be handled at harvest according to year specific development in fry colour during storage. Management of potatoes at harvest according to field specific development in fry colour during storage within a year showed less potential for benefits. Nitrogen status of the crop in the final part of growth period and rate of leaf senescence were identified as promising markers for fry colour of 'Saturna' during storage, while pre-harvest measurements of sugar content in the tubers were useless.