Evaluation of gelation properties of jackfruit (Artocarpus heterophyllus) waste pectin

Effect of enzymatic de-esterification and RG-I degradation of high methoxyl pectin (HMP) on sugar-acid gel properties

The influence of RG-I domains on high methoxyl pectin (HMP) sugar-acid gel properties has rarely been reported. In our work, HMP was modified by enzymatic de-esterification and degradation of RG-I domains to compare and analyze the relationship between the structure and final sugar-acid gel properties. The results showed that the degree of esterification (DE) of REP (pectin degraded by rhamnosidase) and GEP (pectin debranched by galactosidase) was the same as that of untreated HMP, whereas the DE of PMEP (pectin de-esterified by pectin methyl esterase) decreased from 59.63 % to 54.69 %. The monosaccharide composition suggested no significant changes in the HG and RG-I structural domains of PMEP. In contrast, the percentage of RG-I structural domains of REP and GEP dropped from 37 % to about 28 %, accompanied by a reduction in the proportion of the RG-I backbones and side chains. The rheological characterization of sugar-acid gels demonstrated an enhanced gel grade for PMEP and a weakened one for REP and GEP. Moreover, we constructed a correlation relationship between the fine structure of pectin and the properties of the sugar-acid gels, confirming the critical contribution of the RG-I region (especially the neutral sugar side chains) to the HMP sugar-acid gels.

Physicochemical and functional properties of pectin extracted from the edible portions of jackfruit at different stages of maturity

BACKGROUND

The physicochemical and functional properties of pectin (JFP) extracted from edible portions (including pericarp and seed) of raw jackfruit (an underutilized tropical fruit) at four different maturity stages (referred to as stages I, II, III, and IV) were characterized in terms of extraction yields, chemical composition, molecular weight, and antioxidant properties to evaluate its potential use in foods.

RESULT

The JFP yield increased from 9.7% to 21.5% with fruit maturity, accompanied by an increase in the galacturonic acid content (50.1%, 57.1%, 63.6%, and 65.2%) for stages I-IV respectively. The molecular weight increased from 147 kDa in stage I to 169 kDa in stage III, but decreased to 114 kDa in stage IV, probably due to cell-wall degradation during maturation. The JFP was of the high methoxyl type and the degree of esterification increased from 65% to 87% with fruit maturity. The functional properties of JFP were similar to or better than those reported for commercial apple pectin, thus highlighting its potential as a food additive. Although the phenolics and flavonoids content of JFP decreased with fruit maturity, their antioxidant capacity increased, which may be correlated with the increased content of galacturonic acid upon fruit development. Gels prepared from JFP showed viscoelastic behavior. Depending on the maturity stage in which they were obtained, different gelation behavior was seen.

CONCLUSION

The study confirmed the potential of pectin extracted from edible parts of jackfruit as a promising source of high-quality gelling pectin with antioxidant properties, for food applications. © 2022 Society of Chemical Industry.

Physicochemical characteristics and functional properties of high methoxyl pectin with different degree of esterification

Moderate alkali de-esterification can change the physicochemical characteristics and thus the functional properties of high methoxyl pectin (HMP). The results revealed that de-esterification could increase negative charges (Zeta potential from -21 to -31 mV), decrease molecular weight (from 448 to 136 kDa) and apparent viscosity of HMP. Homogalacturonan (HG) content decreased (from 62% to 49%) while rhamnogalacturonan Ⅰ (RG-Ⅰ) content increased (from 32% to 46%) after de-esterification. The group characteristics of HMP with different degree of esterification (DE) were similar and no obvious impact was made on degree of crystallinity by alkali de-esterification. A conformation transition of HMP molecule implied by Congo red test were occurred as the DE decreased. With the decrease of DE, the molecular structure of HMP became shorter and smaller, and the entanglement was weaker. The de-esterification caused slight decrease of thermal stability. Alkali de-esterification would weaken the gel property and the emulsifying ability of HMP.