Development of innovative techniques for the shelflife extension of eggplant fruits (Solanum intergrifolium)

Even though eggplant fruits (garden eggs) play a very important role in the diet of a majority of Ghanaians, no simple, modern and cost effective method of preservation of this perishable commodity exists. This study was undertaken with the aim of developing simple technique(s) that will appreciably improve the storage life of two cultivars of eggplant fruits commonly grown in Ghana (Solanurn intergrifolium cvs. Fanti and Improved Fanti), to reduce ripening rate, reduce microbial spoilage, and maintain overall consumer acceptance characteristics. Experiments were carried out to study the effects of curing, ethanol pretreatment, edible coating of gum arabic, and packaging of perforated low density polyethylene (LDPE) bags vis-a-vis storage in an evaporative cooling chamber (ECC) and storage under ambient conditions on eggplant fruits. Treatments stored in the ECC were labeled CST and CNS whereas those stored under ambient conditions were labeled BST, BNS and CON (Control). The % moisture content, % weight losses, total soluble solids, pH, titratable acidity, microbial load and some colour attributes (Value - L*, Hue - a*, Chroma - b*) were monitored over a 14 day storage period. It was initially established that stalk (calyx) removal of eggplant fruits significantly reduced the rates of moisture and weight losses (P < 0.05). With the exception of treatments coated with gum arabic there were no significant differences in Titratable acidity, pH and total soluble solids (TSS) among all treatments (P < 0.05). Rates of moisture and weight losses were further reduced by storage in the ECC and most significantly reduced by storage of the fruits in perforated low density polyethylene bags. As low as 2.94% weight loss was recorded for CNS after day 14. In this study TSS, pH and titratable acidity decreased while microbial load increased with time (Days). However, there were significant differences in microbial load between COr and other treatments. CST and CNS treatments also had highly significant microbial load compared to their corresponding treatments BST and BNS respectively (P < 0.05). Gum arabic coating did not significantly reduce moisture and weight losses but rather increased microbial load, as well as enhancing spoilage. As much as 56.45% of the CNS treatments were spoilt at the end of 14 day storage period as against 6% of CON. The gum arabic served to enhance the gloss of the products. Storage of all the treatments in LDPE bags except CON resulted in extended sheiflife of the fruits. There was a highly significant difference between CNS and CST treatments and between BNS and BST treatments (P < 0.05). Stalk removal, pretreatment with ethanol, and packaging in LDPE film bags coupled with low temperature storage significantly reduced the moisture and weight losses and enhanced the maintenance of overall consumer acceptance characteristics (P <0.05). Microbial load was significantly lower than the control (P < 0.05). Value - Hue - a*, and Chroma - b* for CST and CNS were significantly different from BST, BNS and CON (P < 0.05). In conclusion, pretreatment of eggplant fruits reduces microbial spoilage whilst the combined use of stalk removal and low temperature storage significantly reduces shriveling due to moisture and weight losses. The sheiflife is further extended beyond 14 days of storage with little or no shriveling when unstalked fruits are pretreated and stored in perforated LDPE films.

Source: KNUST