Optimization of hot water treatment of guava fruits cv. ‘Shweta’ to prolong cold storage

Antioxidant enzymatic changes in bell pepper fruit associated with chilling injury tolerance induced by hot water

“…The products of oxidation such as ascorbic and dehydroascorbic acids are transformed newly into AsA, maintaining higher levels at the end of storage (Yahia et al, 2000). Similar results were previously reported in sweet pepper (Endo et al, 2019) and guava fruit (Killadi et al, 2021) treated with HWT at 45 and 50°C, respectively. Both temperatures presented retention and an increase in AsA content during cold storage, Therefore, the use of HWT help to maintain low levels of hydrogen peroxide during cold storage, so it is considered as an important indicator of quality and reflects tolerance to cold stress.…”

“…Control 12°C presented the lowest firmness loss, which is associated with a low water loss and a predominant membrane integrity in the fruit. The reduction of softening during cold storage in treated fruit was previously reported in sweet pepper (Raffo et al, 2007), kiwifruit (Ma et al, 2014), bell pepper (Liu et al, 2018), cucumber (Nasef, 2018) and guava (Killadi et al, 2021). Hafiz et al (2017) reported that HWT (56°C) for 1 min in rambutan was adequate to maintain the firmness of the fruit compared to the control, HWT can reduce the activity of enzymes such as polygalacturonase and pectin methyl esterase, delaying the degradation of pectin in the cell wall, inhibit the activity of enzymes such as desmolase, dehydrogenase and carboxylase, maintaining starch levels (Ullah et al, 2018), and sometimes interrupting or blocking the production of ethylene (Killadi et al, 2021).…”

“…The use of hot water treatment for 1-min in bell pepper increased significantly AsA content at the end of storage at low temperatures, which could be related to the stability provided by the immersion time that prevents the oxidation of this compound, in addition to not allowing the activation of the enzyme ascorbate peroxidase that degrade this compound (Shahkoomahally & Ramezanian, 2013). The dipping in HWT for 2-or 3-min presented a reduction in AsA content, a behavior that some authors related with the activity of enzymes that catalyze oxidation reactions such as ascorbate oxidase and ascorbate peroxidase that use AsA as substrate in response to cold stress and water loss during storage (Killadi et al, 2021;Raffo et al, 2007;Yahia et al, 2000). At the end of storage, the fruit treated with HWT presented higher AsA content than control fruit that presented significative losses in AsA, especially with the immersion for 3 min; according with Yahia et al (2000) the hot water treatment allow that AsA undergoes continuous oxidation and reduction.…”

“…Therefore, the water loss is related with loss cell membrane integrity, saturation of fatty acids, and enzymatic activity that increases physiological disorders. In previous study, bell pepper presented high susceptibility to water loss showing high ion leakage and membrane damage that was related with a strong effect on membrane integrity in the fruit during storage (Maalekuu water-treated cucumber (Nasef, 2018), orange (Shi et al, 2020), sweet pepper (Endo et al, 2019), and guava (Killadi et al, 2021) where the HWT for short time could improve the barrier functions in the membrane and cell wall-reducing water loss and susceptibility to CI. On the other hand, in bell pepper (González-Aguilar et al, 1998), mango (Osuna-Gacía et al, 2007, and rambutan (Hafiz et al, 2017), the use of HWT increased the water loss due to higher respiration and transpiration caused by increased stomal density, cell breakage, and destruction of mesocarp.…”

“…In addition, this protective effect of moderate heat stress can cause the interruption of the normal metabolic process of the fruit, inhibiting the synthesis of oxidative enzymes. In addition, the retention of these compounds during ambient temperature for HWT may be related to a reduction of enzymatic browning and interruption of normal metabolic process (Killadi et al, 2021). In this way, Shen et al (2013) reported that the use of hot water at 50°C…”