Aqueous extraction of pectin from sour orange peel and its preliminary physicochemical properties

Sour orange peel, a by-product of the fruit juice industry, was used as a source of pectin. The effects of temperature (75-95 degrees C), time (30-90 mm), and liquid-solid ratio (20-40, v/w) were investigated on yield, methoxylation degree (DE), and galacturonic acid content using a Box-Behnken design and response surface methodology. The highest extraction yield (17.95+/-03%) was obtained at temperature of 95 degrees C, time of 90 mm, and liquid-solid ratio of 25 (v/w). The DE values for the pectin ranged from 17% to 30.5%, indicating that the pectin was low in methoxyle. The emulsifying activity of pectin extracted under optimal conditions was 45%. The emulsions were 86.6% stable at 4 degrees C and 71.4% at 23 degrees C after 30 days of storage. The pectin exhibited Newtonian flow at low concentrations (<= 1.0%, w/v); as the concentration increased, pseudoplastic flow became dominant. (C) 2015 Elsevier B.V. All rights reserved.