Influence of Extraction Method and Processing Technologies on Physicochemical Properties of Pectin from Pumpkin by-Products
15th International Conference on Food Waste Recovery Technologies and Conventional Extraction (ICFWRTCE 2021): International Research Conference Proceedings 2021
Daiga Konrāde, Māra Jure, Inese Mieriņa

During food primary production up to 60-70% of different by-products, such as peel, pomace and flesh are obtained from vegetables and fruits. Pumpkin (Cucurbita spp.) by-products are promising sources of pectin, which can be further used in food, cosmetics and non-food industries as thickener and gelling agent, as well as sources of antioxidants. The aim of research was to elaborate the most effective and environmentally friendly methods for utilizing peel and flesh of pumpkin - waste products obtained in food processing. Two type by-products were used for extraction of pectin: a) fresh peel (crushed) and flesh obtained immediately after peeling or squeezing of juice, correspondingly; b) powders of conventionally dried peel and flesh (12 hrs drying at +50±2ºC). After drying materials were grinded and sifted through 1.2 mm sieve. Pumpkin peel and flesh materials were extracted 90 min at temperature 85ºC with hot acids (HCl, H2SO4, CH3COOH) or with hot water. Ratio of pumpkin by-products to distilled water was 1:6 (w/v); in case of acidic extraction two different pH values were examined: 1.50±0.02 and 2.00±0.02. Centrifugation (Sigma 4-16KS) of extracts at 7000 rpm for 20 min was used to separate precipitates. Obtained aqueous solutions were mixed with 1.5-fold volume of 96% C2H5OH and precipitated at 4°C for 18 h. Separation of pectin was performed by centrifugation at 7000 rpm for 20 min. Obtained precipitates were washed twice with 70% C2H5OH, moistened with a small amount of distilled water and freeze-dried in laboratory freeze dryer (Virtis SP Scientific Sentry 2.0). Pectin content (PC) calculated on a dry matter (DM) basis reached 1.6-5.4% in pumpkin peel samples and 2.0-6.35% in flesh samples depending from the type of material and extraction conditions. In case of acidic extraction PC increased at lower pH value, but PC was not influenced significantly (p>0.05) depending on the acid used. Extraction with hot water gave 1.9% PC in peel and 2.6% PC in flesh. High-methoxylated pectin (degree of esterification (DE) > 50%) was isolated from both pumpkin by-products: DE of peel pectin was 75-80% (the highest DE was reached using HCl for the extraction), but DE of flesh pectin was 75-90%. These results demonstrate that extraction with hot water can be effectively used as environmentally friendly method for isolation of high-methoxylated pectin from peel and flesh, obtained as by-products in pumpkin processing.


Keywords
By-products, degree of esterification, pectin, pumpkin
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Konrāde, D., Jure, M., Mieriņa, I. Influence of Extraction Method and Processing Technologies on Physicochemical Properties of Pectin from Pumpkin by-Products. In: 15th International Conference on Food Waste Recovery Technologies and Conventional Extraction (ICFWRTCE 2021): International Research Conference Proceedings, Finland, Helsinki, 19-20 July, 2021. Helsinki: Open Science, 2021, pp.74-74. e-ISSN 1307-6892.

Publication language
English (en)
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