**7. Postharvest technology of Nigeria root vegetables**

Root vegetables are mainly functioning roots. Bulbs, corms, rhizomes, and tubers; they have high moisture content making them highly perishable. A moisture content of up to 52 and 72% have been reported for ginger and garlic, respectively [131], which make these root vegetables highly vulnerable to huge postharvest losses. For instance, up to 50% of onions harvested in the northern states of Nigeria were lost during storage [132]. The postharvest losses of these commodities require that they are taken through a number of postharvest operations in order to keep them wholesome for consumption and increase their utilization. There are different low-cost technologies that have been applied in Nigeria, the primary processing involves sorting, blanching, curing, splitting or peeling and drying to a moisture level of 7–12%. In some cases, pretreatments are applied to improve the quality of the final product. This step varies depending on the crop being processed. These postharvest operations will be discussed in this chapter.

### **7.1 Postharvest operations**

#### *7.1.1 Curing*

This helps to release the unique aroma of root vegetables such as ginger, garlic and tumeric that are used as spices, curing is usually done before storage by spreading the bulbs to a thickness of about 5 cm in a shaded and well-ventilated place for 3–4 days. This allows the bulbs to receive dry air which helps to maintain the quality in storage. It is important to remove the tops before curing. Garlic can also be cured by packing in jute sacks in a well-ventilated shady place [97]. The processing of ginger in Nigeria has however not been standardized. Ginger rhizomes are sorted, washed and splitted or peeled. The traditional methods vary considerably resulting in mold growth and loss of important volatile oils [133]. Curing enhances the valued yellow color and aroma of tumeric which is attributed to its curcumin content. The rhizomes must however be separated from the fingers before curing

#### *7.1.2 Peeling*

The skin of whole ginger must be peeled to allow for removal of the water content as it constitutes a barrier for evaporation during drying. Peeling is usually done with knives by scraping off the skin. The use of mechanical peeling machine is gaining popularity among ginger processors; however, the abrasion of machine is similar to hand-scrapping. The time spent during peeling is very critical as it contributes to the loss of volatile oils. In Nigeria, peeling is majorly carried out when the ginger is meant for culinary purposes [134]. Peeled ginger does not attract high prices compared to the splitted ginger and farmers consider it time consuming.
