Modelling the Extraction of Pectin towards the Valorisation of Watermelon Rind Waste.

Watermelon is the second largest fruit crop worldwide, with great potential to valorise its rind waste. An experimental design was used to model how extraction parameters (temperature, pH, and time) impact on the efficiency of the process, purity, esterification degree, monosaccharide composition and molar mass of watermelon rind pectin (WRP), with an insight on changes in their structural properties (linearity, branching degree and extraction severity). The models for all responses were accurately fitted (R2 > 90%, lack of fit p ≥ 0.05) and experimentally validated. At optimum yield conditions, WRP yield (13.4%), purity (540 µg/g galacturonic acid) and molar mass (106.1 kDa) were comparable to traditional pectin sources but showed a higher branching degree with longer galactan side chains and a higher protein interaction. Harsher conditions (pH 1) generated purer homogalacturonan fractions with average molar masses (80 kDa) at the expense of yield, while mild extraction conditions (pH ≥ 2) produced highly branched entangled pectin structures. This study underlines novel compositional features in WRP and the possibility of producing novel customized pectin ingredients with a wider potential application scope depending on the targeted structure.

Upgrading Pectin Production from Apple Pomace by Acetic Acid Extraction.

Pectin, as one of the most widely used functional polysaccharide, can be abundantly extracted from apple pomace which is the main by-product of apple juice industry. In the case of 110 min, 10% (w/w) acetic acid (AA), and 100 °C, extraction yield of pectin reached 19.6%. Compared with mineral acid-extracted pectin, the yield, molecular weight, galacturonic acid content, and DE of the AA-extracted pectin were higher while neutral sugars were lower. Furthermore, the AA-extracted pectin solution demonstrated a higher viscosity during the shear rate increased, and a higher G″ modulus than pectin extracted with mineral acid and commercial pectin possibly because of stronger polymer chain interaction, which was reflected in gel textural properties. The green approach for the pectin production, in terms of pectin components was developed from apple pomace using AA that was highly competitive and environmentally friendly process.

Endo-xylanase and endo-cellulase-assisted extraction of pectin from apple pomace.

Pectins were extracted from apple pomace with monoactive preparation of endo-xylanase and endo-cellulase. The process was conducted for 10 h in conditions of pH 5.0 at 40 °C, with constant shaking. Endo-xylanase application resulted in the highest extraction efficiency of pectins (19.8%). The obtained polymer was characterised by a very high molecular mass, high level of neutral sugars - mainly arabinose, galactose and glucose, and very high DM (73.4). It also contained the highest level of protein and phenols. Pectin extracted with endo-cellulase had 1.5 fold lower molecular mass but contained significantly more GalA (70.5%) of a high degree of methylation (66.3%). The simultaneous application of both enzymatic preparations resulted in their cooperation, leading to a decrease of both the extraction efficiency and the molecular mass of pectin. However, this pectin was distinguished by the highest GalA (74.7%) and rhamnose contents.