Extraction of low methoxylated pectin from pea hulls via RSM

• Published in: Food hydrocolloids 2020-05, Vol.102, p.105609, Article 105609
• Main Authors: Gutöhrlein, Friederike, Drusch, Stephan, Schalow, Sebastian
• Format: Article
• Language: English
• Subjects: Citric acid; Extraction; Nitric acid; Pea hulls; Pectin
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2019.105609

Nowadays, low methoxylated pectin (LMP) is generated in a multi-step process from high methoxylated pectin using fruit by-products as a raw material. In this study, we prove that LMP may be directly extracted from pea hulls. Extraction was conducted according to a central composite design (CCD) and evaluated via response surface methodology (RSM). The influence of different parameters (pH, temperature, time) on yield and composition of the extracted pectic polysaccharides (PPS) was investigated using nitric acid and citric acid as extraction media. Citric acid yielded higher amounts of PPS (3.5–9.8%) compared to nitric acid (1.4–8.0%). However, there is a conflict of aims between a high yield and the purity of the extracted PPS. Composition analysis suggests that under ‘mild’ extraction conditions (pH 2, 70 °C) PPS consist of homogalacturonan, xylogalacturonan and rhamnogalacturonan with arabinose and galactose side chains (RG-I). With increasing temperature (90°), yield is maximised due to an increased solubilisation of cell wall polysaccharides. Under “harsh” conditions (pH 1, 90 °C) the purity of PPS increases in terms of a relatively higher content of uronic acids, but yield decreases. This is attributed to a cleavage of non-GalA components and an ongoing depolymerisation of the pectic galacturonan. PPS extracted under these conditions is characterised by a low degree of acetylation (4%) and a relatively high protein content (7%). [Display omitted] •Extraction with nitric or citric acid generates low methoxylated pectin.•Pea hull pectin is low acetylated and rich in xylose and protein.•Increasing temperature and decreasing pH promote pectin purity but reduce yield.•Citric acid extraction increases yield due to a higher amount of neutral sugars.•Prolonged extraction with nitric acid at increased pH and temperature is recommended.