Effects of fiber-degrading enzymatic treatments on structural and functional properties of pink guava (psidium guajava linn.) Wastes

Hui, Choy Yee (2020) Effects of fiber-degrading enzymatic treatments on structural and functional properties of pink guava (psidium guajava linn.) Wastes. Master dissertation/thesis, UTAR.

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Abstract

Pink guava (Psidium guajava Linn.) is a well-known tropical fruit as it is fiberrich material which contributes health-related benefits upon human consumption. There are large quantities of pink guava wastes (decanter and refiner) generated throughout pink guava puree processing. These plant-based waste materials have high portions of fiber and non-starch polysaccharides. They could not be utilized directly inclusive in one’s diet for consumption, and usually be disposed of as unutilizable wastes. Foremost, this research study aimed to hydrolyze pink guava wastes (decanter and refiner) through fiber-degrading enzymatic treatments; 150 U cellulase (150CE), 150 U xylanase (150XY) and 150 U cellulase-xylanase (150CX) have been employed to treat pink guava waste. It was aimed to analyze structural properties of untreated and enzymatic-treated pink guava wastes based on the attenuated total reflectance (ATR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The untreated and enzymatic-treated pink guava wastes were washed and extracted by using 80% (v/v) ethanol, to obtain alcohol ii insoluble solid (AIS) and alcohol soluble carbohydrates (ASC). Besides, the sugar profiles of untreated and enzymatic-treated pink guava wastes were quantified, and functional properties were determined based on glucose dialysis retardation index (GDRI) of AIS material and prebiotic activity score of ASC. The suitability of whole untreated and enzymatic-treated pink guava wastes as potential prebiotic sources in yogurts was evaluated. The cellulase-xylanase combined enzymatic treatment (2: 1) hydrolyzed synergistically and converted pink guava wastes into simple carbohydrates (rhamnose, xylose, glucose, and fructose) and increased the sugar amount significantly, which were analyzed by High Performance Liquid Chromatography (HPLC). The hypoglycemic effects of combined enzymatictreated pink guava wastes had been improved; it delayed glucose diffusion across dialysis tube. This is due to physical obstacle attributed by fiber particles towards glucose entrapment within fiber network, as evidenced with outcomes of SEM analysis. The prebiotic activity score of ASC derived from combined enzymatictreated pink guava wastes had been significantly enhanced, using Lactobacillus plantarum as a probiotic strain. About 1% (w/w) of untreated and enzymatictreated pink guava waste was added into yogurts to evaluate suitability of pink guava wastes as prebiotic sources, acidity and texture profile of yogurts. The CFU/mL of yogurts added with combined enzymatic-treated decanter and refiner was enhanced by 76.92% and 77.58%, respectively. Therefore, the synergistic hydrolytic action exerted by cellulase-xylanase enzymatic treatment is a feasible approach to hydrolyze and valorize both pink guava wastes into more value-added materials, with enhanced structural and functional properties.

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