engleski

Influence of fruit content and storage time on gel strength and polyphenolic content in chokeberry low sugar pectin-gel products

The aim of this research was to investigate the influence of fruit level (20, 35, 45 and 75 %) and kind of sugar (sucrose or fructose) on polyphenolics' amount and gel strength in low sugar chokeberry pectin gel products during 6 months storage at +20°C. Pectin gel products were prepared form chokeberry purée obtained by cooking and pureeing of chokeberry fruits. Moreover, chokeberry fruits and purees were frozen and stored at -18°C during 6 months and also investigated in terms of polyphenolics. In all chokeberry products soluble solids were ranged 41.80 to 42.20 °Brix, pH from 3.06 to 3.48, and total acidity from 0.95 to 1.17 % (expressed as g citric acids per 100 g sample). Gel strength in all samples was measured by dr. D. Šulc pectinometer. Before storage gel strength of samples with fructose was slightly higher than those with sucrose, but during storage samples with sucrose showed more stable gel strength. Total phenols (TP), flavonoids (TF), and nonflavonoids (TN) were determined by Folin-Ciocalteu method. Higher amount of TP, TF and TN were observed in chokeberry purée compared to chokeberry fruit as well as in both frozen samples after 6 months storage compared to start samples. Further, TF were found in higher level than TN in all investigated samples. Further, higher amount of TP and TF was observed in all gel products with added fructose. Higher fruit level resulted with higher amount of TP, TF and TN in all samples. After 6 months storage TP, TF and TN decreased with retention of TP between 65 – 78 %. Finally, to produce more acceptable nutritive products it could be recommended to produce low sugar gel products with added fructose, and increased fruit level.

chokeberry; polyphenolics; pectin gel products; low sugar jam; gel strength

nije evidentirano