Antioxidative Responses to Pre-Storage Hot Water Treatment of Red Sweet Pepper (Capsicum annuum L.) Fruit during Cold Storage

The effects of hot water treatments on antioxidant responses in red sweet pepper (Capsicum annuum L.) fruit during cold storage were investigated. Red sweet pepper fruits were treated with hot water at 55 °C for 1 (HWT-1 min), 3 (HWT-3 min), and 5 min (HWT-5 min) and stored at 10 °C for 4 weeks. The results indicated that HWT-1 min fruit showed less development of chilling injury (CI), electrolyte leakage, and weight loss. Excessive hot water treatment (3 and 5 min) caused cellular damage. Moreover, HWT-1 min slowed the production of hydrogen peroxide and malondialdehyde and promoted the ascorbate and glutathione contents for the duration of cold storage as compared to HWT-3 min, HWT-5 min, and control. HWT-1 min enhanced the ascorbate-glutathione cycle associated with ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase, but it was less effective in simulating catalase activity. Thus, HWT-1 min could induce CI tolerance in red sweet pepper fruit by activating the ascorbate-glutathione cycle via the increased activity of related enzymes and the enhanced antioxidant level.

Hot Water Treatment for Post-Harvest Disinfestation of Bactrocera dorsalis (Diptera: Tephritidae) and Its Effect on cv. Tommy Atkins Mango

Mango production and trade in sub-Saharan Africa is hampered by direct damage and the high quarantine status of B. dorsalis and the paucity of effective post-harvest phytosanitary treatments. The current study reports the development of a quarantine treatment protocol using hot water to disinfest B. dorsalis and assess its effect on cv. Tommy Atkins mango quality. We first determined the development of the eggs and all larval stages of B. dorsalis in cv. Tommy Atkins mango and used the information to establish a time–mortality relationship of the immature stages after subjecting infested fruits to a regimen of eight, time instances of hot water at 46.1 °C. Using probit analysis, we estimated the minimum time required to achieve 99.9968% mortality of each stage. Our results indicate that the egg was the least heat tolerant, followed by the first, second, and third instar. The time required to achieve 99.9968% control of the third instar in cv. Tommy Atkins mango (400–600 g) was determined to be 72.63 min (95% Cl: 70.32–74.95). In the confirmatory trials, the hot water treatment schedule of 46.1 °C/72.63 min was validated, and none of the 59,120 most heat-tolerant individuals treated survived. Further, there were no significant differences between hot water-treated and untreated mangoes recorded in weight loss, fruit firmness, pH, total soluble solids, moisture content, and titratable acidity eleven days post-treatment. These findings demonstrate an effectively optimum post-harvest disinfestation treatment against B. dorsalis in cv. Tommy Atkins mango that should be adopted commercially to facilitate access to profitable but strict export markets globally.

Effect of hot-water immersion on eggs and larvae of Anastrepha grandis (Macquart, 1846) (Diptera: Tephritidae) “in vitro” and on squash (Cucurbita moschata Duchesne, 1786)

There are risks involved in the production and exportation of fruit fly hosts due to the possible spread of tephritid pests during distribution. Anastrepha grandis attacks cucurbit fruits and is considered an A1 quarantine pest in many countries. The objective of this study was to evaluate the effect of hot water treatment on the eggs and larvae of A. grandis in vitro, and on ‘Atlas’ squash (Cucurbita moschata). The eggs and third-instar larvae of A. grandis were exposed to hot water at temperatures of 42.0, 44.0, 46.0, 46.5, 47.0, 47.5, 48.0, 49.0 and 50.0 (± 0.5) °C for durations of 0 (control), 10, 20, 30 and 60 minutes. Water temperatures of at least 44 °C affected the in vitro larval eclosion of A. grandis during all exposure times. No adults were obtained when in vitro A. grandis larvae were treated at 49 °C and 50 °C at all exposure times and, 48 °C for 30 and 60 minutes. No adults were obtained when squashes infested with A. grandis eggs or larvae were treated at temperatures of 49 °C and 50 °C during any exposure time, as well as subjected to 48 °C for 20 minutes. Anastrepha grandis larvae were slightly more susceptible to hydrothermal treatment than eggs in squashes. Hot water treatment applies at a temperature of 48 °C for 20 minutes is an effective phytosanitary treatment for squashes cv. Atlas infested with eggs and larvae of A. grandis.

Effect of Seed Size and Different Pretreatment Methods on Germination of Albizia zygia (DC.) J. F. Macbr

Albizia zygia produces valuable timber which has received some level of prominence in the international market. However, the seeds are dormant, and the tree species remain undomesticated. This study was conducted to evaluate the effect of seed size and presowing on the germination of Albizia zygia in a nursery. Seeds were grouped into four categories in regard to their length, small (≤0.5 cm), medium (> 0.5 < 0.8 cm), large (≥0.8 cm), and mixture of small, medium, and large seeds. The seeds were subjected to five main seed pretreatment methods, namely, soaking in sulphuric acid (H2SO4) for 2 minutes, mechanical scarification, soaking in hot water for 5 minutes, soaking in cold water for 24 hours, and control where seeds were sown without any treatment. The results indicate that combination of mechanical scarification and large seeds produced the highest (100%) germination. Hot water treatment was effective in large seeds producing 69.0% germination. The increased germination for mechanically scarified seeds suggests that seed dormancy in Albizia zygia is mainly due to its hard seed coat. Therefore, it is recommended to farmers to adopt use of mechanical scarification and large seeds, since it is safe and effective.

Influence of hot water treatment to quality properties of pineapple (Ananas comosus) fruit during storage

Pineapple (Ananas comosus) was a non-climacteric fruit popularly distributed in Vietnam and other tropical regions. It was highly preferred by great appearance, wonderful texture, special flavour and perfect nutritional value. Moreover, it was also a good source of minerals, vitamins and antioxidants beneficial for human health. In harvesting season, it was highly perishable under ambient storage due to its high metabolic and moisture content resulting in quality degradation. This research evaluated the possibility of hot water treatment to the retention of quality attributes during storage. Pineapple fruits were dipped in hot water at different times and temperatures 30/35 (as control), 50/45, 52/40, 54/35, 56/30, 58/25, 60/20, 62/15 (°C/s). They were drained for 30 mins and stored at the ambient condition at the relative humidity of 85-90% for 15 days. In 3 day-interval, these fruit groups were taken to evaluate weight loss, firmness, decay index, total soluble solids (TSS), ascorbic acid. Results showed that there was a significant difference between the control and 7 treated groups. Pineapple fruits treated by hot water at 56/30 (°C/s) showed the lowest weight loss (0.15±0.05 to 1.34±0.01%), the lowest decay index (1.03±0.02 to 1.63±0.02), the most firmness (19.43±0.00 to 18.63±0.03 N), the highest TSS (24.35±0.02 to 23.01±0.01oBx), the highest ascorbic acid content (18.59±0.01 to 17.79±0.02 mg/100 g). Application of hot water submergence provided an alternative to chemical treatment to extend pineapple stability during storage and improve its marketability in distribution

Advances in Postharvest Disinfestation of Fruits and Vegetables Using Hot Water Treatment Technology-Updates from Africa

Hot Water Treatment (HWT) provides adequate phytosanitary assurance that treated fruits and vegetables exported abroad are free from devastating quarantine pests. Two systems for HWT are currently available for commercial use namely the batch/jacuzzi and the continuous flow system depending on user requirements. Several protocols have been developed the world over and a few in Africa, but adoption has been lagging because of various factors chief among them lack of large scale validations of experiments to guide application at the commercial level. Mango, Bell pepper, avocado, and French beans play an important role in the livelihoods of people in Africa. However, their export is constrained by pests such as the invasive Oriental fruit fly, the false codling moth, and thrips. To circumvent this issue, disinfestation HWT protocols have been developed which seek to provide quarantine assurance to lucrative export markets. Hot Water Treatment technology has several advantages over other conventional phytosanitary treatments. It provides a triple function of cleaning, disinfesting, and disinfecting and is friendly to users, consumers of the treated commodities, and the environment. We discuss HWT in the context of its future and applicability in Africa. It is the future of postharvest treatments.