Optimization of acid-extraction of pectic fraction from grape (Vitis vinifera cv. Chardonnay) pomace, a Winery Waste.

Chardonnay grape pomace was evaluated as a source of pectin. A central composite design was used in order to determine the effect of pH, extraction time (Et) and liquid: solid ratio (LS) on the yield and uronic acid (UA) content of the pectins extracted using boiling HNO3 solution. The optimized extraction condition to reach the maximum yield and UA was pH = 2.08, Et = 135.23 min and LS = 35.11 ml/g, resulting in theoretical yield of 12.8% and UA of 64.4%. The experimental yield of the pectic fraction obtained under the optimized conditions (GPOP) was 11.1% and the UA was 56.8%. GPOP had ~25% glucose. It was treated with α-amylase and amyloglucosidase, resulting in the fraction α-GPOP. The starch-free pectic fraction was composed of 63.5% UA, 7.8% rhamnose, 6.0% arabinose, 13.6% galactose and minor amounts of other neutral monosaccharides. It contained a low-methoxyl pectin (degree of methyl-esterification 18.1%) and had an average molar mass of 154,100 g/mol. It consisted of 55.7% homogalacturonan and 35.2% rhamnogalacturonan I (RG-I). NMR analyses suggest that RG-I portion of α-GPOP is highly branched by short chains or single residues of arabinose and galactose.

Investigation of cell wall polysaccharides from flour made with waste peel from unripe banana (Musa sapientum) biomass.

BACKGROUND: The peel from unripe banana biomass is an agroindustrial waste. The present study aimed: (i) to extract pectin from enzymatically-treated waste peel from unripe banana biomass (WPUBB) using a Box-Behnken design to optimize the extraction conditions (temperature, pH and extraction time) and obtain a maximum yield and (ii) to fractionate the polysaccharides from WPUBB employing sequential extractions using different solvents. RESULTS: The optimized product was obtained at 86 °C, pH 2.00, for 6 h and it presented a yield of 11.63%. The optimized product had low galacturonic acid content and a high amount of glucose (82.3%), suggesting the presence of starch (as confirmed by the bi-dimensional heteronuclear single quantum coherence NMR spectrum). All of the fractionated polysaccharides had a high glucose content. Low amounts of pectin were found in the water, chelating and diluted alkali-soluble fractions. The fractions extracted using NaOH indicated the presence of glucuronoarabinoxylans. CONCLUSION: Glucose was the main monosaccharide found in all the fractions extracted from the WPUBB. Although the present study suggests that WPUBB is still not suitable for pectin extraction using current technologies, other compounds, such as resistant starch and glucuronoarabinoxylans, were found, suggesting that WPUBB could be used in the development of food formulations. © 2019 Society of Chemical Industry.

Cell wall polysaccharides from Ponkan mandarin (Citrus reticulata Blanco cv. Ponkan) peel.

Cell wall polysaccharides from ponkan peel were investigated with the aim of gain knowledge about their potential for different applications and the use of ponkan peel as raw material for pectin extraction. The plant material was defatted using MeOH:CHCl3, pretreated with DMSO and then subjected to sequential extractions with cold and hot water, ammonium oxalate, HCl, Na2CO3, 2 M and 4 M NaOH in order to obtain polysaccharides. The polysaccharide fractions were analyzed by chemical, chromatographic and spectroscopic methods Cold and hot water-soluble pectins contained higher amounts of GalA and higher degrees of methyl-esterification (DM) than ammonium oxalate and HCl fractions. Na2CO3 extraction provided non-esterified arabinose-rich pectins which formed gel in a dialysis step. NaOH solubilized hemicelluloses, composed mainly of xyloglucans, galactomannans and galactoglucomannans. The water-soluble fraction (WSP) was purified using α-amylase and amyloglucosidase and gave rise to the subfraction named α-WSP. The α-WSP was a pectin composed of HG and RG-I domains containing side chains of arabinans and short-chains of galactans, with low DM (39.4%) and Mw of 1.615 × 105 g/mol.

Extraction of pectin from ponkan (Citrus reticulata Blanco cv. Ponkan) peel: Optimization and structural characterization.

A central composite experimental design was used to evaluate the influence of pH, extraction time and liquid:solid ratio on the yield and uronic acid content of the pectin from ponkan peel. The response surface methodology showed that the yield is positively influenced by lower pHs, longer extraction times and higher liquid:solid ratio, whereas the uronic acid content decreases with increasing extraction time. The conditions that resulted in the highest yield and highest uronic acid content were defined as pH 1.6, extraction time of 100 min and liquid:solid ratio of 36 mL/g. The pectin obtained under these conditions (PPOP) had an experimental yield of 25.6%, below the predicted theoretical value despite the good fit of the model (R2 = 0.96) and the galacturonic acid content was 84.5%, in close agreement with the predicted theoretical value. PPOP was composed mainly of a homogalacturonan with degree of methyl esterification of 85.7% and a rhamnogalacturonan I region mainly branched by galactans. In addition, PPOP had a very low degree of acetylation (0.1%) and average molar mass of 80,650 g/mol, determined by light scattering. The results showed that ponkan peel may be used as a source of citrus pectin in the regions where this species is cultivated.

Cell wall polysaccharides from pulp and peel of cubiu: A pectin-rich fruit.

To investigate the polysaccharides of cubiu (Solanum sessiliflorum D.) fruits, pulp and peel were subjected to sequential extractions using different solvents, giving rise to pectins heterogeneous with respect to their structural characteristics, xylan, arabinogalactoxyloglucans and glucomannans. Chemical, physicochemical and spectroscopic analyses were used to characterize the polysaccharides obtained. Pectins with uronic acid content of commercial grade were obtained from the peel of cubiu fruits using water (25°C and 100°C) and EDTA and from its pulp using water (100°C). The fraction with the highest yield (9.6%) and uronic acid content (79.0%) extracted from the peel using water at 100°C was chemically and structurally characterized. This fraction consists predominantly of a mixture of a homogalacturonan (degree of methyl-esterification 56.9%) and a small amount of rhamnogalacturonan I branched by type I and type II arabinogalactans. The results suggest that cubiu is a promising source of pectins with high uronic acid content extractable by cheaper and environmentally friendly method.