A Comparative Study of Microbial and Proximate Composition of Hand Shelled and Machine Shelled Melon Seeds (Colocynthis citrullus L.) as Sold in an Abeokuta Market

Abstract

Melon (Colocynthis citrullus L.) is a widely cultivated and consumed oil-seed in West Africa. Its seeds deteriorate quickly in storage due to microbial attack introduced during the shelling stage of processing. Aim: This study investigated and compared the microbial and proximate composition of Hand shelled and machined melon seed as sold in the market in Abeokuta, Nigeria. Study Design: The total bacterial, total fungal, Staphylococcal and coliform counts of the machine shelled and hand shelled melon seeds samples were determined.  Methodology: The mould count was estimated as SFU/g and isolates (Aspergillus) were identified through spore formation, production of fruiting bodies, morphological and molecular characteristics.  The proximate and chemical compositions-Free Fatty Acid (FFA) and Peroxide Value (PV)-were determined by standard analytical methods. Data were analysed using analysis of variance. Results: There is no significant (p<0.05) difference in the proximate composition of both the hand shelled and machine shelled melon seed save the pH. The proximate compositions of hand shelled and machine shelled melon samples were within the recommended limits for Curcubitaceae, both FFA (1.88±0.02%, 1.88±0.01%) and PV(2.64±0.01 meq/kg, 2.65±0.02 meq/kg) values respectively were within the Codex Alimentarius range for oily seeds. The pH value of Hand shelled (5.57±0.09) is significantly higher than Machine shelled (6.10±0.06). The fungal count of machine shelled (92.33x108 SFU/g) was significantly higher than hand shelled (38.00x108 SFU/g). Staphylococcal count of hand shelled (59.00x108 CFU/g) was significantly higher than machine shelled (42.00x108 CFU/g). However, there is no significant difference in total bacterial and coliform counts of both melon samples. The fungal species found in hand shelled and machine shelled melon samples were mainly genus Aspergillus with  A. niger with  percentage of occurrence (30%, 22%) and A. flavus (8%, 11%) respectively. Bacillus subtilis (14%, 40%) and Staphylococcus aureus (43%, 20%) were also found in hand shelled and machine shelled melon. These organisms are of spoilage and food poisoning importance. Conclusion: The study concluded machine shelled melon harbours more spoilage microorganisms and may spoil faster than hand shelled melon seed.