Agriculture & Food, Volume 10, 2022

Abstract: Pumpkin (Cucurbita spp.) – a tropical fruit in the family Cucurbitaceae is widely grown worldwide – including Northern Europe region. During pumpkin processing by-products – pumpkin pulp and peel remain, still containing pectin which has a unique chemical structure and physical properties. Ultrasonic (US), microwave (MW), conventional hot water/ acid (HW) was used to determine the most efficient pectin extraction method. Pectin yield (PY) calculated on a dry matter (DM) basis reached 3.8% – 16.2 % in pumpkin by-product samples. Galacturonic acid (Gal A) content reached 75.34 g 100 g -1, methoxy (ME) content - 9.55 %, equivalent weight was from 685 – 745, moisture content ≤10%, ash of extracted pectin ≤10 %. Glucose was the predominantly in pectin samples – in pectin from pumpkin peel - 31.65±9.11 g 100 g -1. Fucose was found in small amounts in all pectin samples – 0.14 – 0.87 g 100 g -1, Rhamnose 2.59 – 7.48 g 100 g -1, Arabinose – 1.82 – 7.58 g 100 g -1, Galactose, 2.42 – 17.11 g 100 g -1, Xylose 0.23 - 2.23 g 100 g -1, Mannose 0.24 – 1.38 g 100 g -1, Glucuronic acid (GlcA) – 0.32 – 1.01 g 100 g -1. The gelling properties and gel forming was different according to method of extraction and methoxy content in pectin samples - better gel forming was detected for pectin gels with pectin obtained from pumpkin pomace with US and MW. The results demonstrate that extraction without acid, assisted with microwaves and ultrasound can be effectively used as environmentally friendly methods for isolation of high-methoxylated pectin with high content of galacturonic acid (>50 %) from by-products after pumpkin processing. Pectin from pumpkin by-products further can be used as thickener, gelling agent, cation-binding agent for food and cosmetics industries.