Bacteriological Analysis of Fermented Cereal Flour Sold in Markets in Calabar Metropolis, Southern Nigeria

Introduction

Pap otherwise called “Ogi’’ or “Akamu’’ is a product of fermented maize (Zea mays) widely eaten in Africa [1]. It is also made from sorghum (Sorghum vulgare) or millet (Pennisetum typoidum) [2]. Its smooth texture is almost like that of a hot blancmange and a sour taste that reminds one of yoghurt. The colour of ogi depends on the colour of the cereal used and includes: cream colour for maize ogi, reddish- brown colour for sorghum ogi [3]. Pap is often marketed as a wet cake formerly wrapped in leaves but presently in transparent polythene bags. This pap meal is mostly served as breakfast meals for both adults and weaning food for infants especially by low income earners who are not able to afford the more expensive weaning foods [4].

Most preparation of pap meal is from cereals such as; maize, guinea corn or millet readily available in all parts of the country.

Production of pap is carried out mostly by local producers [5]. This is made from wet corn starch or other cereals by thoroughly washing the dry corn and soaking it for about 72- 96 hours to make the corn soft enough to be blended. It is then washed and blended till smooth. The blended product is further sieved using a chiffon cloth while rinsing as necessary to remove shafts that might make the paste have a rough consistency. This pap paste is mixed with water and left to settle for about 3 hours [6]. After 3 hours, it is decanted and poured into a muslin bag and left to drain completely overnight to further give it its sour taste. The solidified pap is then cut and shaped into small portions and wrapped in transparent polythene bags for sale to consumers [7].

During processing, handling, there is a high risk of bacterial contamination which often makes the food products undesirable due to the presence of these organisms that cause food poisoning, spoilage or food intoxication [5]. Preliminary studies have shown that the processing and wet storage methods of this prepared paste permit bacterial growth, including other pathogens [8]. The machines used during processing may not be properly cleaned up after each usage. Water used in washing and grinding may contain microorganisms because of the high risk of environmental pollution.

Furthermore, not only is the storage cumbersome, which involves daily changing of the water used for storing the wet flour paste, but also very unreliable because of the prevalent epileptic electric power supply in Nigeria [8]. Food poisoning and infection can lead to fatal consequences in infected individuals, and the major risk factors are attributed to contaminated raw materials, poorly controlled fermentation conditions, poor personal/environmental hygiene and post processing handling [9].

Some are capable of producing heat resistant toxins (e.g Staphylococcus aureus, Clostridium botulinum). Most pathogens are mesophilic with optimal growth temperature ranging from 20°C to 45°C. However, certain food borne pathogens (i.e psychrotrophs) such as Listeria monocytogenes, are capable of growth under refrigerated conditions or temperatures less than 10°C [10]. Street foods are ready-to-eat foods and beverages prepared and/or sold by vendors and hawkers especially in streets and other public places [11]. Street vended foods are not only appreciated for their unique flavours, convenience and the role which they play in the cultural and social heritage of societies. They have also become important and essential for maintaining the nutritional status of the populations [12].

Unsanitary handling of street foods by some vendors has been commonly found to be a source of contamination [13, 14]. The vendors can be carriers of pathogens like Escherichia coli, Salmonella, Shigella, Campylobacter and Staphylococcus aureus who eventually transfer these foods to the consumers. The hands of the food handlers have been found to be the most important vehicle for the transfer of organisms from faeces, nose and skin to the food.

The finding that Salmonella, non-typhi Salmonella, and E.coli can survive on finger tips and other surfaces for a period of time and in some cases after washing, supports the reports of contamination of street vended food with toxigenic S. aureus [15, 16]. Fermentation during pap production occurs in two distinct stages: (i) steeping of maize prior to obtaining pap gruel and (ii) souring of fermented pap [17]. During this process, the fermentation facilitates the multiplication of bacteria and their activities in softening the corn kernel [6]. During fermentation, there is an interaction of different kinds of organisms. This interaction can be beneficial to the final product by means of desirable biochemical changes like the production of aromatic compounds and other enzymatic activities.

Despite this, there is a risk of contamination of the food, as the interactions of microorganisms involved in the fermentation process may be detrimental causing spoilage [17]. More so, fermentation in the production of pap is largely done in a traditional formula and poorly controlled. This crude form of processing encourages a high level of bacterial contamination [6].

Some studies have identified some microorganisms and the level of contamination that are associated with commercially prepared fermented pap. In a study by Ekelene OE [18] in some parts of South Eastern Nigeria, the presence of bacteria isolates from the commercial and laboratory fermented ogi showed that Lactobacillus spp, and Staphylococcus spp were present in all samples while Klebsiella spp was isolated from markets varieties respectively. Therefore, this study aimed at determining the bacteriological survey of commercially prepared paps sold in markets in Calabar Metropolis, Southern Nigeria.

Discussion

This study isolated Staphylococcus aureus, non- coagulase Staphylococcus aureus and Bacillus cereus from three markets; Goldie market, Watt market and Marian market in Calabar Metropolis. Of the 80 samples analyzed, the overall prevalence of Staphylococcus aureus was 41.7%, which was higher than 5.0% prevalence of Staphylococcus aureus isolated from Uturu and Okigwe markets in Imo state, Nigeria [18]. This was also higher than the 4.2% prevalence of Staphylococcus aureus isolated in Ebonyi state, Nigeria [19]. This prevalence was lower than the 58.3% prevalence of Staphylococcus aureus isolated in Bauchi state, Nigeria [20].

The prevalence of Bacillus cereus was 27.8% and was seen to be higher than the prevalence of 8.3% of Bacillus cereus in a study on pap in Bauchi State, Nigeria [20]. Staphylococcus aureus (47.6%) had the highest prevalence found in samples from Goldie market, followed by Bacillus cereu (26.1%)s and non-coagulase Staphylococcus aureus (17.6%)with the least prevalence from both Watt and Marian market respectively. However, the difference was not statistically insignificant (P˃0.05). Goldie market is a small market located behind the University of Calabar. Students and other residents patronize this market greatly. This market is known for its poor drainage system and overpopulation due to the small size of its geographic space. The presence of a high rate of microorganisms from this market could be attributed to the poor drainage system through the environment. These findings from the study are similar to the previous studies carried out on pap samples by Ogbonnaya JA, et al. [1, 20] which reported the same microorganisms in their study.

Several authors have highlighted the importance of adequate nutritional quality and hygiene during the preparation of foods and also the link between infection and nutrition [7] reported the presence of pathogenic bacterium such as Staphylococcus aureus in pap and other food. The common storage of pap was wet storage [13]. This method of storage has a high connection to the microbial load which is due to the fact that water used for storage, most of the time, is unclean and harbours microorganisms. A good percentage of pap sellers in the market made use of community borehole water for both production and storage of pap produce. The difference between those that used community borehole and private bore holes for preparation and storage was statistically significant (P ˂ 0.05). The isolation of the microorganisms from the pap samples confirmed that it could serve as a vehicle for the transmission of potentially pathogenic microorganisms [9].

Conclusion

Staphylococcus aureus (41.7%), non-coagulase Staphylococcus aureus (23.4%) and Bacillus cereus (27.8%) were isolated from pap samples purchased from markets in Calabar Metropolis, Calabar, cross River State, Nigeria. Staphylococcus aureus (41.7%) was found to be the highest isolates from samples obtained from Goldie market the hygienic practices of those selling pap in markets was very poor.