Pomelo pectin and fiber: Some perspectives and applications in food industry

Volarisation of agricultural by-products is a potential approach to meet sustainable food ingredient production. This work investigates the extraction of pectin from pomelo albedo as well as the recovery of fiber from the residue left over from the pectin extraction process. Different peels conditions, ranging from mature and young peels with and without drying up to storage time of four months, were studied. It was found that these starting raw materials resulted in comparable yield (23.2-39.1%), ash content (3.4-5.4%), degree of esterification (56.5-78.7%) and molecular weight (213-529 kDa). All extracted pectins could be categorised as high methoxy pectins. In contrast, shear rheology of 1%w/v pectin dispersions, prepared from these extracted pectins, showed that they exhibited shearing thinning but showed relatively large variation in viscosity among these raw materials, which was likely due to the differences in their fine microstructure. Hence, the standardisation step is often required to control viscosity and gel strength in industrial pectin manufacturing process. Furthermore, the effect of peel storage time, i.e., up to four months, on the properties of pectin was insignificant, thus, providing increased strategies to manage raw materials for sustainable upscale processing. The prebiotic potential of the pomelo pectin with their abilities to promote growth of selected microbial species, especially short chain fatty acid (SCFA)-producing bacteria, were evaluated. It was found that pomelo pectin showed the ability in selective growth promotion and SCFA production of SCFA-producing bacteria, especially Eubacterium maltosivorans, while exerting no effect on the pathogenic bacterium. Therefore, the pomelo pectin could exploit its potential as a prebiotic. To achieve a zero-waste process, the residue from pectin extraction process could also be recovered as pomelo fiber. The contents of total, soluble and insoluble dietary fibers in the recovered pomelo fiber were approximately 86, 20 and 66 g/100 g, respectively. Such fiber was shown to have good water holding capacity and formed strong gel. It also exhibited strong shear thinning behaviour and could therefore be used advantageously as texture modifier in food applications. Overall, this work provides a new insight of pectin extraction as well as fiber recovery from pomelo peels that can potentially provide a new source of functional pectin and fiber for applications in food or pharmaceutical industries.