Microwave- and ultrasoound-assisted extraction of pectin yield and physicochemical properties from lemon peel

Abstract

Taiwan produces a total of about 46,000 metric tons of lemons, and its processing by-product, lemon peel, is rich in pectin. Proper utilization of vegetable and fruit processing waste increases the value of lemons and also achieves the purpose of friendly and sustainable environmental protection. To promote the applications in industries, ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE) of pectin from lemon peel was performed and the effects of both on the yield (%), physiological, and chemical properties of lemon pectin were explored and evaluated in the present study. In addition, the response surface methodology (RSM) was also applied to optimize the extraction conditions, and the extraction was carried out with the central composite design (CCD) of three factors: UAE: time (X1, 60∼110.5 min), pH (X2, 1.0 ∼3.0), and temperature (X3, 20.8∼80.2 °C); MAE: time (X1, 1.5∼6.5 min), pH (X2, 1.0∼3.0), and wattage (X3, 113.6∼786.4 W). The results showed that the specific optimized conditions for UAE were 60 min, pH 1.0, and 55 °C. The optimal conditions for MAE were 4 min, pH 1.0, and 450 W; the optimal yields of lemon peel pectin were 37.9 % and 41.4 % respectively.

Keywords

• Pectin
• Response surface methodology
• Galacturonic acid
• Degree of esterification
• Functional group