Effect of storage on nonenzymatic browning of apple juice concentrates. Food Chem 80

Abstract Kinetics of nonenzymatic browning in Golden Delicious and Amasya apple juice concentrates during 4 months are investigated. Apple juice concentrates were at 65, 70, 75 Bx of Golden Delicious variety, stored at 5, 20, 37 C and Amasya variety, stored at 37, 50, 65 C. Colour development was measured by browning index (A 420 ) and the CIE-Lab colour system. Browning level of all apple juice concentrates increased according to a zero-order reaction kinetic. Activation energies for 65-75 Bx of Golden Delicious and Amasya apple concentrates ranged from 21.4 to 21.0 kcal/mol and 33.7 to 32.5 kcal/mol, respectively. Influence of soluble solids content on browning was negligible. HMF concentration, in Golden Delicious apple juice concentrates, was between 0.52 and 963 mg/kg, and between 0.52 and 190 mg/kg in Amasya apple juice concentrates.

Antioxidant activity of selected fruits and vegetables grown in Turkey

Antioxidant activities of different fruits (apple, quince, grape, pear and pomegranate) and vegetables (potato, onion, spring onion, red radish and red cabbage) were determined. In addition, total phenolic and flavonoid contents of those samples were assessed. Among fruits, pomegranate had the highest (62.7%) antioxidant activity, followed by quince (60.4%), grape (26.6%), apple (25.7%) and pear (13.7%). The antioxidant activity of vegetables ranged from 40.8% (red cabbage) to 12.5% (onion). Total phenolic and flavonoid contents in fruits varied from 326 to 4306 mg of catechin kg-1 and from 282 to 2115 mg of catechin kg-1, respectively. Those in vegetables ranged between 536 and 2166 mg of catechin kg-1 and between 153 and 842 mg of catechin kg-1, respectively. A high and significant correlation between antioxidant activity and total phenolic content was determined in fruits (r2 = 0.9307, P < 0.01) and vegetables (r2 = 0.9361 P < 0.05). However, flavonoid content was not significantly correlated with antioxidant activity in vegetables, while it was significantly related in fruits (r2 = 0.8316, P < 0.01). It was observed that total phenolic content is the major contributor to the antioxidant activity of fruits and vegetables