A Comparative Study of Pectin Green Extraction Methods from Apple Waste: Characterization and Functional Properties

Abstract

Traditional methods of pectin extraction led to drop quality, yield, functional properties, and excessive time. The objective of our research is to produce high-quality pectin from apple pomace as food processing by-product. Four nonconventional methods of extraction (microwave, ultrasound, citric acid, and organic acid mixture (citric acid, ascorbic acid, and acetic acid)) were compared to conventional extraction of pectin in terms of yields, thermal behavior, functional groups, antioxidant activity, and functional properties. Citric acid extraction method gave the highest yield (22%) compared to other methods. The extraction of pectin by organic acid mixture maximized the galacturonic acid index to 87.58%;. Also, it was changed from structural into: compacted, multilaminated, and flaky surface compared to the other samples (more porous and hollow opening structural) as well as increased stability of pectin particles in colloids as a result of increasing the charge on particles to -59.42, beside its higher thermal stability of pectin behaviors, which reflected on improving all functional properties compared to the other methods. On the other side, microwave-extracted pectin had the highest antioxidant activity (3-4 times) compared to other extraction methods. In conclusion, extraction using organic acids, microwave, and ultrasonic led to improve the pectin quality and could be used in high-temperature food products, like bakery products.

Towards Valorization of Food-Waste-Derived Pectin: Recent Advances on Their Characterization and Application

“…Also for apple pomace pectin extraction, the main advantages deriving with the use of innovative techniques instead of the traditional methods are mainly higher yields; less time and time/energy consumption, especially for MAE, which is also less solvent-consuming, thus avoiding matrix depolymerization problems; and finally low equipment corrosion [46]. This pectin, which represents 14% of commercial pectin, is characterized by HMP with a DM of 50%, pointing out its suitability as a potential gelling agent; in addition, it also fits the quality standard of commercially available food-grade pectin (GA 65 g/100 g) recommended by the Joint Expert Committee on Food Additives (JECFA) [22,49]. In recent years, tropical-fruit-derived waste such as mango [13,25,50], jackfruit [27,51], banana [14,26], papaya [52], custard apple [53], and passion fruit peels [54] have been proposed as interesting sources of pectin.…”

“…Pectin extraction from discharged apple pomace using food-grade organic acids (tartaric, malic, citric, and generally recognized as safe-GRAS) could represent an eco-friendly and safe protocol leading to a yield (6-7%) similar to that obtained using 0.1 M HCl, widely used in the pectin manufacturing industry with additional toxic chemical waste production. Moreover, the extraction process with citric acid resulted in high-viscosity apple peel pectin [22,47]. Nevertheless, a good apple pomace pectin yield (about 10%) was also obtained using MAE and radiofrequency-assisted extraction (RFAE) [23], differently from what was obtained using CE, probably due to the prolonged time and high temperature applied, which caused the de-esterification of polygalacturonic chains.…”