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. 2024 Oct 3;13(19):3157.
doi: 10.3390/foods13193157.

Pectin Microwave Assisted Extraction from Pumpkin Peels: Process Optimization and Chemical-Physical and Rheological Characterization

Ilaria Frosi  1 , Raffaella Colombo  1 , Raffaele Pugliese  2 , Chiara Milanese  3 , Adele Papetti  1
Affiliations

Pectin Microwave Assisted Extraction from Pumpkin Peels: Process Optimization and Chemical-Physical and Rheological Characterization

Ilaria Frosi et al. Foods. .

Abstract

Recently, pectin, a versatile polysaccharide with different industrial applications, has gained significant attention as an eco-friendly and functional ingredient. This study investigates pumpkin peels (Cucurbita maxima L., Mantua variety) as a novel source of pectin, using a microwave-assisted extraction method with citric acid-acidified water as solvent. The extraction conditions were optimized using a Design of Experiments approach, considering the solvent-to-solid ratio (SSR), pH, temperature, and extraction time. The optimized conditions (94.8 °C, 5 min, pH 1.5, and 46 mL/g SSR) resulted in a pectin yield of 18.05%. A comprehensive characterization of the extracted pectin was performed, including FT-IR spectroscopy, DSC, TGA, rheological properties, and techno-functional assessments such as water holding capacity and fat binding capacity. The results indicated a high degree of esterification (56.19 ± 0.87%), classifying the pumpkin peels (PP) extract as a high methoxyl pectin. PP pectin demonstrated potential as a stabilizer and emulsifying agent, although its high methoxyl content limits its use as a carrier for targeted bioactive delivery. The findings support the viability of using agricultural by-products to obtain valuable polysaccharides, contributing to waste valorization and sustainable industrial practices.

Keywords: agrifood waste; by-products; emulsifier agent; high methoxyl pectin; pumpkin peels pectin.

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Conflict of interest statement

The authors declare no conflicts of interest. The funders had no role in the study’s design; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Response surface plot showing the effect of SSR and pH on pectin yield (PEY) at 70 °C and 10 min extraction time.
Figure 2
Figure 2
FT-IR spectrum of isolate pectin polysaccharide from pumpkin peels.
Figure 3
Figure 3
DSC (a) and TGA (b) analyses of the extracted pumpkin peels pectin.
Figure 4
Figure 4
Molar weight (Mw) distribution of pumpkin peel pectin (1 mg/mL in NaCl 0.1 M) by SEC-RID system.
Figure 5
Figure 5
Image of different emulsions prepared by using various concentration of pectin (1–3% w/v) and sunflower oil (35–60% w/v).
Figure 6
Figure 6
Rheological studies on pumpkin peel pectin: frequency-dependent oscillatory rheology (0.1–100 Hz) to test the mechanical properties.
Figure 7
Figure 7
Rheological studies on pumpkin peel pectin: flow curves to test the viscosity.
See this image and copyright information in PMC

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