CHANGES IN TOTAL PHENOLIC AND FLAVONOID CONTENTS OF ROWANBERRY FRUIT DURING POSTHARVEST STORAGE

Abstract

ABSTRACT Postharvest storage conditions of rowanberry (Sorbus aucuparia) fruits were investigated. The influences of temperature and storage time on total phenolic content were observed. Both variables affected phenolic content of rowanberries, and their total phenolic contents significantly reduced during the 20-day storage at 4 and 22C. The loss of total phenolic was found to be almost 50% of its initial amount (3,619.8 mg/kg fresh weight [fw]) at 22C, which was higher than occurred loss (30%) at 4C. An investigation of rowanberry flavonoids showed the presence of rutin, quercetin-3-glucoside and quercetin-3-D-galactoside (Q3DG). Quantitative analysis of berry flavonoids showed Q3DG as a major compound, being 24.55 mg/kg fw. The highest reduction (86% of its initial amount) was also seen in that compound level compared with other ones. Degradation kinetics of flavonoids was studied at 22C over 16 days of storage. Checking of model adequacies indicated that their reductions followed a first-order kinetic. PRACTICAL APPLICATIONS Postharvest storage has been taken, increasing the interest of scientists because of various reasons, one of which is explained next. The presented results indicated the direct and/or indirect influence of storage conditions on the quality of berries, implying that whoever is planning to store plant and/or plant origin food products in a refrigerator or at room temperature should consider the conditions and their possible effects on the quality parameters from the aspects of economics and nutritional properties of products. In the present study, the stability of an important bioactive group, phenolics, in rowanberries and the influences of environmental conditions were examined, and additionally, degradation kinetics of major phenolic group, flavonoids, was analyzed. The results are valuable and helpful for the evaluation of the postharvest storage and its effect on rowanberries. Introduced model may be helpful for the prediction of storage time required for the degradation of phenolics up to the acceptable limit.