The role of water distribution, cell wall polysaccharides, and microstructure on radish (Raphanus sativus L.) textural properties during dry-salting process

Radish (Raphanus sativus L.) undergoes texture changes in their phy-chemical properties during the long-term dry-salting process. In our study, we found that during the 60-day salting period, the hardness and crispness of radish decreased significantly. In further investigation, we observed that the collaborative action of pectin methylesterase (PME) and polygalacturonase (PG) significantly decreased the total pectin, alkali-soluble pectin (ASP), and chelator-soluble pectin (CSP) content, while increasing the water-soluble pectin (WSP) content. Furthermore, the elevated activities of cellulase and hemicellulase directly led to the notable fragmentation of cellulose and hemicellulose. The above reactions jointly induced the depolymerization and degradation of cell wall polysaccharides, resulting in an enlargement of intercellular spaces and shrinkage of the cell wall, which ultimately led to a reduction in the hardness and crispness of the salted radish. This study provided key insights and guidance for better maintaining textural properties during the dry-salting process of radish.

The combined application of Arabic gum coating and γ-aminobutyric acid mitigates chilling injury and maintains eating quality of 'Kinnow' mandarin fruits

Low temperature storage of citrus generally extends the storage potential but leads to chilling injury appearance on the rind of fruits. The said physiological disorder has been found associated with changes in the metabolism of cell walls and other attributes. In this work, the influence of Arabic gum [AG (10 %)] and γ-amminobutyric acid [GABA (10 mmol L^-1)] either alone or in combined form was studied on fruits of 'Kinnow' mandarin during storage at 5 ± 1 °C for 60 days. The results exhibited that the combined AG + GABA treatment significantly suppressed weight loss (5.13 %), chilling injury (CI) symptoms (2.41 score), incidence of disease (13.33 %), respiration rate [(4.81 μmol kg^-1 h^-1) RPR] and ethylene production [(0.86 nmol kg^-1 h^-1) EPR]. In addition, AG + GABA application reduced relative electrolyte (37.89 %) leakage (REL), malondialdehyde [(25.99 nmol kg^-1) MDA], superoxide anion [(15.23 nmol min^-1 kg^-1) O₂^•-] and hydrogen peroxide [(27.08 nmol kg^-1) H₂O₂] along with lower lipoxygenase [(23.81 U mg^-1 protein) LOX] and phospholipase D [(14.07 U mg^-1 protein) PLD] enzyme activities compared with control. The AG + GABA treated 'Kinnow' group showed higher glutamate decarboxylase [(43.18 U mg^-1 protein) GAD] and lower GABA transaminase [(15.93 U mg^-1 protein) GABA-T] activity having higher endogenous GABA (42.02 mg kg^-1) content. The fruits treated with AG + GABA exhibited higher cell walls (CW) components such as Na₂CO₃-soluble pectin [(6.55 g kg^-1) NCSP], chelate-soluble pectin [(7.13 g kg^-1) CSP] and protopectin [(11.03 g kg^-1) PRP] concentrations along with lower water-soluble pectin [(10.64 g kg^-1) WSP] compared to control. In addition, 'Kinnow' fruits treated with AG + GABA showed higher firmness (8.63 N) and lower activities of CW degrading such as cellulase [(11.23 U mg^-1 protein) CX], polygalacturonase [(22.59 U mg^-1 protein) PG], pectin methylesterase [(15.61 U mg^-1 protein) PME] and β-galactosidase [(20.64 U mg^-1 protein) β-Gal] enzymes. The activity of catalase [(41.56 U mg^-1 protein) CAT], ascorbate peroxidase [(55.57 U mg^-1 protein) APX], superoxide dismutase [(52.93 U mg^-1 protein) SOD] and peroxidase [(31.02 U mg^-1 protein) POD] was also higher in combined treatment. In addition, AG + GABA treated fruits showed better biochemical and sensory attributes than the control. So, combined AG + GABA could be used for CI mitigation and storage life prolongation of 'Kinnow' fruits.