Comparative Studies on Citrullus vulgaris, Citrullus colocynthis and Cucumeropsis mannii for Ogiri Production

Abstract

Aim: This study investigated the microbiological, physicochemical and antinutritional properties of three varieties of fermenting melon seeds namely: Citrullus vulgaris (Schrad), Citrullus colocynthis (L) and Cucumeropsis mannii (Naud) for ogiri production. Methodology: Ogiri was produced from these three varieties of melon seeds following the traditional fermentation process while online monitoring was used to evaluate microbial hazards using standard microbiological techniques. Physicochemical and antinutritional properties were determined using standard methods. Results: Bacterial counts ranged from 7.0 x 103 cfu/g to 2.4 x 104 cfu/g for Citrullus vulgaris, 3.2 x 105 cfu/g to 3.7 x105 cfu/g for Citrullus colocynthis and 8.7 x 106 cfu/g to 9.1 x 106 cfu/g for Cucumeropsis mannii. Some of the isolated microorganisms from the fermenting melon seeds include Lactobacillus species, Bacillus species, Aerococcus viridans, Staphylococcus aureus, Micrococcus luteus, Aspergillus niger, Penicillium species and Fusarium eguseti. Cucumeropsis mannii had the highest crude fibre and protein (12.7 and 38.5 mg/g) but lowest values for fat and ash while Citrullus vulgaris recorded the highest values of 35.3 and 3.4 mg/g There were no significant differences in values obtained for sodium, Cucumeropsis mannii had highest values for potassium and phosphorus (0.36 and 0.29 mg/kg). Citrullus vulgaris was outstanding in mineral content for magnesium with the highest value of 0.27 mg/kg and lowest for calcium (0.29 mg/kg) compared to 0.30 and 0.34 for Cucumeropsis mannii and Citrullus colocynthis respectively. Anti-nutrients were highest in Citrullus vulgaris and lowest in Cucumeropsis mannii. Acidic pH of 5.78 was recorded in Citrullus colocynthis but increased to 8.91 and 8.69 in Citrullus vulgaris and Cucumeropsis mannii indicating that Citrullus colocynthis may not be appropriate for ogiri production. Conclusion: Cucumeropsis mannii compares favourably with traditionally used Citrullus vulgaris resulting in higher fibre, protein, mineral contents with lower values of anti-nutrients and therefore recommended as a good substitute for ogiri production.