Physicochemical and physiological properties of pitaya [Hylocereus Polyrhizus (Weber) Britton & Rose] peel pectin

Physicochemical and technological properties, and the cholesterol -lowering potential of high methoxyl pectin extracted f rom pitaya peel (PP) using citric acid, microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) techniques have been reported. However, enzyme-assisted citric acid extraction and its ef fect on the yield, physicochemical, technological, in vitro bile acid binding and hypoglycemic properties, and in vivo cholesterolemic and glycemic properties of low and high methoxyl pitaya peel pectin (PPP) have not been investigated. In this study, pectin was extracted f rom PP using distilled water (DW) and dif ferent concentrations (0.5,1.0, 1.5, 2.0 %) of citric acid (CA) with the aid of cellulase (C) enzyme to obtain PPP f ractions with dif ferent degree of esterif ication (DE). Pectin yield was determined and physicochemical properties such as proximate composition, DE, galacturonic acid (GalA) content, molecular weight (Mw) and monosaccharide prof ile of the PPP f ractions were then analysed. In addition, technological properties such as water-holding capacity (WHC), oil-holding capacity (OHC), emulsifying activity (EA), emulsion stability (ES) and viscosity of the PPP f ractions were also determined. The glycaemic properties of the dif ferent PPP f ractions were measured using three dif ferent in vitro methods: glucose adsorption capacity, glucose dif fusion, and amylolysis kinetics. Meanwhile, in vitro bile acid-binding capacities (BABC) of the PPP f ractions were quantif ied using high pressure liquid chromatography (HPLC). Low methoxyl and high methoxyl PPP f ractions that resulted f rom cellulase assisted distilled water (CDW) and cellulase assisted 1.5% citric acid (C1.5CA) extractions, respectively, were used for in vivo hypoglycemic and hypocholesterolemic activities evaluation using the Sprague Dawley rats. The PPP f raction extracted with C1.5CA had the highest yield (24.63%), GalA content (62.39%), DE (50.20%), WHC (7.53 g water/g dry sample), OHC (2.17 g oil/g dry sample), EA (100%), and ES (100%). Higher viscosity and in vitro normalised BABC were observed for 2% PPP extracted with C1.5CA. Interestingly, the same f raction (PPP extracted with C1.5CA) exhibited the highest glucose dif fusion retardation index of 31.24 af ter 120 min. The in vivo results were consistent with the in vitro f indings where PPP extracted with C1.5CA demonstrated good hypoglycemic and hypocholesterolemic activities. In conclusion, cellulase assisted 1.5% citric acid (C1.5CA) extraction of pectin f rom PP resulted in an array of new and improved physicochemical and physiological properties compared to that of commercial pectins and pectin f rom PP as reported previously. Moreover, PPP extracted with C1.5CA exhibited potent antidiabetic properties. Thus, it could be a suitable alternative food ingredient for the management of Type 2 diabetes mellitus.

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