Physicochemical properties of tamarillo (Solanum betaceum Cav.) hydrocolloid fractions

Abstract

Tamarillo (Solanum betaceum Cav.) is an underutilised fruit in Malaysia. The fruit, however, contains good proportions of soluble fibre, protein, starch, anthocyanins and carotenoids. Amongst the fruits, only tamarillo mesocarp contains both polar (anthocyanins) and non-polar (carotenoids) pigments. The ability to retain both polar and non-polar pigments in the mesocarp could be related to the unique properties of its hydrocolloids. To understand the pigment-hydrocolloid interaction in the fruit, information on the physicochemical characteristics of the hydrocolloids is required. Therefore, hydrocolloids from the anthocyanin-rich seed mucilage fraction of the tamarillo and its carotenoid-rich pulp fraction were extracted and characterised. Water and 1% citric acid were used to extract the seed mucilage hydrocolloid while 72% ethanol and 20mM HEPES buffer were used for pulp hydrocolloid extraction. Seed mucilage hydrocolloid was primarily composed of arabinogalactan protein-associated pectin whereas pulp hydrocolloid was composed of hemicellulosic polysaccharides with some naturally interacting proteins and neutral polysaccharides.

In vitro prebiotic activities of tamarillo (Solanum betaceum Cav.) hydrocolloids

“…To evaluate the resistance of tamarillo hydrocolloids to the digestive enzymes, the molecular weights (Mw) of the hydrocolloids before and after simulation of hydrocolloid digestion in human body were compared. The Mw of digested THC, THW, THE and THH were 3.07 × 10 5 g/mol, 1.93 × 10 5 g/mol, 2.17 × 10 7 g/mol and 2.54 × 10 7 g/mol, respectively which were not significantly different than the Mw of the hydrocolloids before the simulation of digestion (Gannasin et al, 2015) suggesting the hydrocolloids were not significantly hydrolysed by the digestive enzymes and simulated gastric and intestinal juices. Therefore, the hydrocolloids will remain indigestible when they reach the colon and will be available for fermentation by the gut microbiota.…”

“…Citric acid or water was reported for being able to extract the seed mucilage hydrocolloid from tamarillo puree while the pulp hydrocolloid can be extracted from tamarillo puree using ethanol or HEPES buffer (Gannasin et al, 2015).The citric acid and water extractions were performed based on a method described by Yuliarti et al (2008) with some modifications. For citric acid extraction, puree was extracted with 1% (w/v) citric acid (pH 2.2) using a 1:4 (w/v) puree to citric acid ratio and the extraction was carried out in a shaking water bath at 25°C for 30 min.…”

“…The ethanol extraction was performed using the same procedure as the HEPES buffer extraction except that chilled 72% undenatured ethanol replaced the HEPES buffer. The detailed procedures of all the four extractions were described by Gannasin et al (2015). Tamarillo hydrocolloids obtained from the citric acid, water, HEPES buffer and ethanol extractions were denoted THC,THW,THH, and THE, respectively.…”

“…Arabinogalactan protein-associated low methoxyl pectin which was the predominant hydrocolloid in the seed mucilage fraction (Gannasin et al, 2015) was more favourably utilised by bifidobacteria and lactobacilli than the pulp hydrocolloids most probably due to the reason that the bacteria have genes encoding carbohydrate-active enzymes (CAZymes) specific for degradation of the seed mucilage hydrocolloid. Relationship between carbohydrate structure and CAZymes and its effect on the composition of gut microbiota has been reviewed by Hamaker and Tuncil (2014).…”

“…The mesocarp contains anthocyanin (polar)-rich dark red seed mucilage and carotenoid (non-polar)-rich orangish pulp. Recently, Gannasin, Adzahan, Hamzah, Mustafa, and Muhammad (2015) discovered two types of hydrocolloids: low molecular weight arabinogalactan protein-associated pectin in the seed mucilage fraction and high molecular weight hemicellulosic polysaccharides in the pulp fraction. The hydrocolloids have different physicochemical properties and may exhibit different prebiotic activities.…”