**4. Benefits of HWT**

The biggest benefit of HWT is that it has a triple function of cleaning, disinfecting [86], and disinfesting [19, 20, 37]. During the treatment process, dirt, debris, and any extraneous material are removed which could potentially affect fruit or vegetable quality. Most systems incorporate a hot water brushing and rinsing station where fruits are scrubbed and rinsed dry by cool air [87]. This stage is absent for example in VHT and fungicides are easily applied if need be at this stage. The technology is relatively uncomplicated, uses clean water from conventional water sources, and is purely a non-chemical postharvest disinfestation process [88]. The cost of setting up a HWT facility is considered far much less (10%) than setting a similar VHT facility [89]. Treatment by VHT often causes scalding if vapor is not uniformly distributed, while a simple water pump can easily distribute heat uniformly in immersion HWT. Compared to irradiation and chemical treatments, HWT does not use chemicals, hence leaves no residues on treated commodities ([88] and references thein). When chemicals are used in the disinfestation of fruits e.g. the use of methyl bromide fumigation, residues are left on the fruits which pose health risks to consumers. Consumerism is increasing all over the world and consumers are becoming aware of their rights and continuously demand to be served healthy food.

Hot water treatment slows down ripening in fruits thus increasing shelf life [90]. Shelf life is very important as fruits and vegetables are perishable [74]. From harvest to consumption there is a huge lag that requires that fruits be kept in good quality to enable transportation and storage before reaching consumer tables. Experiments have also shown that HWT can confer tolerance of low temperature (chilling injury) in some fruits such as avocado [72]. Short treatments of fruits before cold treatment have been shown to reduce injury caused by excessive cold. Subjecting fruits to HWT before the actual treatment (particularly cold) is becoming more applicable because of the positive benefits.

#### **5. Prospects**

Hot water treatment may be the future of sustainable postharvest treatment of fruits and vegetables in Africa. Thus more investment into precision equipment is required. Equipment with state-of-the-art sensors, heating, and circulation

apparatus. This will ensure that research is conducted in commercial facilities allowing large-scale validations to be performed. Many deformities, injuries, and effects on sensory parameters are results of poor equipment being used. Research at the molecular level is required to determine heat regimes that are not detrimental to finer qualities at the micro and macro protein levels. Combination treatments must be explored especially for heat susceptible fruits and vegetables. The combination treatments must be relatively affordable. With the wider acceptance of insects for food, the use of chitin in coating to increase shelf life must be explored [91].

It is imperative to develop specific protocols that consider variety, size, maturity, and other factors than use blanket treatments that produce horrible results. This may be costly initially but very profitable in the long run. Standards will eventually have to be developed, so that uniformity in operations is maintained. The whole system requires a Multi-stakeholder approach than lone attempts in such a global village. In such a case, customization and harmonization of protocols become feasible resulting in cost-saving especially in instances where fruit varieties/cultivars are similar and there are no significant differences in size and other physical and physiological characteristics.
