Microbial and Fungal Contamination of Different Dried Cocoyam Flakes during Storage

Abstract

Background: Contamination of food by microorganisms from the processing to the consumption stage has become a major health concern in this era, where a better approach for the elongation of food shelf life is explored. This study aims to evaluate the microbial and fungal contamination of different dried cocoyam flakes during storage.
 Methods: The cocoyam (Colocasia esculenta) samples were properly cooked, peeled, sliced into thin shapes, and dried to constant weights. The drying methods used were sun, hot-air oven, and Nigerian Stored Products Research Institute (NSPRI) multi-crop dryer; samples were divided into three groups A, B, and C, respectively, and the dried samples were stored for three months. Moisture Content (MC) was conducted using the standard method. Colonial morphology, Gram staining, and biochemical test were used to identify and characterize microorganisms. Statistical analyses were performed using SPSS 20.0.
 Results: There was a significant increase in the MC of all the samples after the storage duration. The sun-dried sample had the highest MC (13.60%) while the oven-dried sample had the lowest MC (10.82%). The sun-dried samples had the highest viable bacteria count (7.2×105 Colony Forming Unit (CFU)/g) and the oven-dried sample had the lowest count (5.1×105 CFU/g). The four bacterial isolates identified were Bacillus subtilis, Pseudomonas aeruginosa, Micrococcus luteus, and Staphylococcus aureus. The heterotrophic fungal number was the highest (0.5×103 CFU/g) regarding sun-dried samples, whereas the samples dried with NSPRI multi-crop dryer and oven-dried samples had the same value (0.3×103 CFU/g). Aspergillus flavus, A. niger, Rhizopus, Penicillium, and Mucor were isolated from the samples. Rhyzopertha dominica was identified in sun-dried samples.
 Conclusion: The increase of MC and the nature of the storage material may have contributed to high bacterial and fungal counts of stored dried cocoyam flakes, especially sun-dried ones, thereby exposing consumers to potential health risks.