COMPARATIVE ANALYSIS OF THE MICROBIOLOGICAL AND NUTRITIONAL COMPOSITION OF RAW AND ROASTED CORN (ZEA MAYS) SOLD WITHIN AKUNGBA AKOKO

The findings of this study on the comparative microbiological and nutritional composition of raw and roasted corn sold within Akungba Akoko provide valuable insights into the influence of processing on food quality and safety. The microbiological analysis of both raw and roasted maize sold within Akungba Akoko revealed the presence of diverse bacterial and fungal isolates, reflecting the susceptibility of maize to microbial colonization during harvesting, handling, and vending. In this study the total viable counts indicated that raw maize samples harbored significantly higher microbial loads compared to roasted maize. For instance, isolates such as CSADC1 and CSADC2 from raw maize recorded colony counts up to 3.90 × 10⁸ CFU/ml and 1.53 × 10⁹ CFU/ml respectively, while roasted samples such as CSBDC1 and CSBDC4 showed much lower values of 4.65 × 10⁵ CFU/ml and 1.22 × 10⁶ CFU/ml. These differences highlight the impact of roasting in reducing microbial contamination, which is in line with the findings of Makinde et al. (2020) who reported lower microbial burdens of 1.0 x 105 Cfu/ml in thermally processed cereals. Among the bacterial isolates in this study, Bacillus subtilis, Bacillus cereus, and Bacillus megaterium were predominant. The presence of Bacillus species is not much surprising, as they are renown spore-forming bacteria known to withstand adverse conditions including heat (Ray et al., 2024). Their detection even in roasted maize indicates that although roasting reduces vegetative cells, resistant spores may survive the process. Of particular concern is Bacillus cereus, a recognized foodborne pathogen capable of producing enterotoxins that cause diarrheal 37 and emetic syndromes in humans (Ehling-Schulz et al., 2019). The survival of B. cereus spores in roasted maize therefore poses potential risks if the product is improperly stored or consumed after prolonged holding at ambient temperature which is also encouraged by the findings of Ray et al. (2024). The detection of Staphylococcus aureus in maize samples is also noteworthy. This organism is commonly associated with contamination from human handlers, suggesting poor hygiene during vending and handling processes (Samson et al., 2014). S. aureus is capable of producing heat stable enterotoxins that can cause food poisoning even when bacterial cells are inactivated by cooking (Kadariya et al., 2014). The presence of Staphylococcus spp. in roasted maize underscores the risk of post-processing contamination, which has also been reported in some studies on street-vended foods including yam, suya and maize, by Nworu et al. (2021). Similarly, Aeromonas hydrophila, another bacterial isolate detected, is an opportunistic pathogen commonly found in water and moist environments. Its occurrence in maize samples likely reflects contamination from washing or exposure to unhygienic water sources during handling. Fungal isolates were also recovered in this study including the species of Aspergillus fumigatus and Aspergillus niger, particularly in raw maize samples. These fungal isolates are known for the contamination of cereals and are also known to produce mycotoxins such as aflatoxins and fumonisins which have severe public health implications (Samson et al., 2014). The higher prevalence of Aspergillus species in raw maize compared to roasted maize confirms that roasting significantly reduces fungal loads, although recontamination during vending remains a possibility. The combined bacterial and fungal profile of maize samples from Akungba Akoko therefore suggests that raw maize poses considerable microbiological risks to consumers due to its high 38 load of pathogenic and toxigenic organisms. Roasting improves food safety by lowering viable counts, but the persistence of spore-formers like B. cereus and the detection of S. aureus emphasize the importance of hygienic practices post-roasting. This aligns with Mwove (2023), who stressed that thermal processing alone is insufficient without proper food handling to guarantee microbiological safety. In terms of nutritional composition, roasted corn showed a slight reduction in moisture content compared to raw samples, a trend commonly associated with thermal processing that reduces water activity and thereby improves shelf stability (Sruthi et al., 2021). Carbohydrate and energy values were slightly higher in roasted samples, possibly due to concentration effects from moisture loss, while certain heat-sensitive vitamins and proteins were moderately reduced, as supported by findings from Dabija et al. (2021) and Swati et al. (2024) on cereal processing. Similar nutritional variations between raw and processed maize have been highlighted by Li et al. (2022), who reported that processing methods alter fatty acid and nutrient profiles of corn. The nutritional relevance of maize as an important food crop in Africa has been widely reported, particularly in relation to its contribution to micronutrient intake (Galani et al., 2022; Epule et al., 2022). However, processing such as roasting has dual implications: while it improves safety by reducing microbial risks, it can also lead to partial nutrient loss. This aligns with the findings of Liu et al. (2022), who emphasized that food processing must balance safety, nutritional retention, and consumer acceptability. Phytochemical analysis showed the presence of tannins and phytates in both roasted and raw maize, with higher values in the latter. This agrees with the work of Otoo (2024), who demonstrated that processing methods such as roasting and boiling reduce anti-nutritional factors in cereals. Tannins are known to inhibit protein digestibility, while phytates reduce 39 mineral bioavailability, supporting the earlier reports of Terefe et al. (2021). Thus, although roasting lowers these compounds, their residual presence still poses dietary concerns. Mineral analysis revealed that maize samples contained appreciable amounts of calcium, iron, magnesium, potassium, and phosphorus. Roasted maize showed higher calcium and phosphorus values, while fresh maize contained more iron. This trend is consistent with the findings of Terefe et al. (2021), who observed variations in mineral composition of maize with different processing methods. The relatively high phosphorus content also supports its role as an energy food, as earlier reported by Nsabimana et al. (2024). These results suggest that while roasting enhances the bioavailability of some minerals, it may simultaneously reduce others, highlighting the nutritional trade-offs of thermal processing.