Apple Pomace Is a Good Matrix for Phytochemical Retention

Phytochemical content and color changes in dried apple pomace and pulp (mixture of Red Delicious and Golden Delicious varieties) were studied during 9 months storage in the water activity (a(w)) range 0.11-0.75 at 30 degrees C. Water mobility was measured at various a(w) levels by H-1 NMR. During storage, antioxidant degradation (including flavonols, flavanols, dihydrochalcones, anthocyanins, and hydroxycinnamic acids) followed first-order kinetics, whereas color changes followed zero-order kinetics. These changes were accelerated by increasing a(w). Phytochemical and color were more stable in the pomace than in the pulp over the entire a(w) range, having 2-6 times smaller degradation rates. These results were related to the lower water mobility found in apple pomace as compared to the pulp. The overall results show that apple pomace can be exploited as a food ingredient with good phytochemical retention, and may help in the development of new matrices with maximum phytochemical retention.