Characterisation of Fiber Obtained from Pumpkin (cucumis moschata duch.) Mesocarp Through Enzymatic Treatment

Abstract

Cell wall-enriched pumpkin ( Cucumis moschata Duch.) powder was submitted to enzymatic hydrolysis by cellulase or hemicellulase in order to evaluate the performance of these cell wall-degrading enzymes on that substrate. Different enzyme-substrate ratios were evaluated and the effect exerted by the buffer on cell wall polysaccharides. Cellulase produced the release of pectin macromolecules which include homogalacturonans side chains, the rhamnogalacturonan I core and rhamnogalacturonan II, in conjunction with xylogalacturonans. The content of galacturonic acid in product obtained ranged from 545 to 781 g/kg of fiber. Hemicellulases produced intense pectin hydrolysis leading to fiber-fractions with galacturonic acid contents ranging from 390 to 444 g/kg of fiber and enriched in glucose polymers as the enzyme proportion increased. Few rhamnogalacturonan-I was present.The acidic citrate buffer (pH 5.2) used for allowing enzyme activity could per se remove noncovalent cross-links like ionic bonds. As a consequence, pectin-in-extensin entanglements, pectins joined by Ca2+-bridges through the homogalacturonan side chains, and some pectins that are originally soluble in cold water due to little or no binding to the cell wall, could be removed by this citrate buffer. Enzymatic hydrolysis as well as buffer extraction produced fiber-products with an important thickening effect of aqueous systems. This effect was smaller as the ratio enzyme-substrate was increased and, in general, the fiber fractions isolated produced an in vitro glucose diffusion retardation.

Commercial cell wall hydrolytic enzymes for producing pectin-enriched products from butternut (Cucurbita moschata, Duchesne ex Poiret)

“…Cell wallpolysaccharides suffered cleavage when powder was submitted to enzymatic treatment into 0.05 mol dm À3 -citrate buffer (pH 5.2), with the aim of getting soluble fractions essentially constituted by pectins, which can present interesting functional properties for food applications. An enzyme preparation containing cellulase (A) or hemicellulase (B), both commercially used for dough and bread improving, were applied, looking for isolation of pectin fractions with thickener performance like that observed in a previous work using enzymes for laboratory research (Fissore et al, 2007) but with a lower-cost procedure. The yields obtained with the industrial enzymes used in the present work were 4.70 g/100 g (using cellulase; A-fraction) and 6.12 g/100 g (using hemicellulase; B-fraction).…”

“…This fraction showed a starch content of 0.16 g/100 g. When purified hemicellulase (SIGMA, USA) has been previously used for the process, by the authors (Fissore et al, 2007), the starch content of fraction isolated was $17 g/100 g (unpublished results), probably due to different activities of both hemicellulases.…”

“…Some residual content of Man (0.49 mol per 100 mol of total sugars) as well as an important proportion of glucose (6.57 mol per 100 mol of total sugars) were also found (Table 1), probably indicating contamination of the isolated pectin by co-extracted galactoglucomannans, GGM (Schröder et al, 2001). Fissore et al (2007) also observed a lower molar concentration of Rha, Ara and Gal in the product obtained using hemicellulase with respect to the content observed when cellulase acted on butternut powder, being both from the same laboratory provider (SIGMA, USA); they concluded that this trend indicated poor RG-I presence in the fiber fractions obtained through hemicellulase action.…”

Pectic substances: From simple pectic polysaccharides to complex pectins—A new hypothetical model

“…Cell wall-rich pumpkin (Cucumis moschata Duch.) digestion with cellulase released pectin macromolecules which included linear HG side chains, the RG-I core and RG-II, in conjunction with XGA (Fissore, Ponce, Stortz, Rojas, & Gerschenson, 2007). Lately, polyGalA-branched HG (GaGA) complexes have been shown to be an integral part of Na 2 CO 3 -extracted tomato pectins (Round et al, 2010).…”

The hypoglycaemic effect of pumpkins as anti-diabetic and functional medicines

“…It has been demonstrated that water-extracted pumpkin polysaccharides possess superior hypoglycaemic properties compared to glibenclamide in alloxan-induced diabetic rats (Zhang, 2004). Additionally, pumpkin is rich in pectin, a type of dietary fibre (Fissore, Ponce, Stortz, Rojas, & Gerschenson, 2007), which when consumed is purported to control glycaemic levels and reduce the need for insulin when fibre-rich foods are consumed by patients with diabetes (Guillon & Champ, 2000).…”