MICROBIAL BURDEN AND ANTIMICROBIAL SUSCEPTIBILITY OF ISOLATES FROM BEAN CAKES SOLD IN MINNA METROPOLIS, NIGERIA

ABSTRACT

Bean cakes are ready-to-eat deep-fried cowpea paste. It is commonly known as àkàrà (in Yoruba language) or kosai (in Hausa language) in Nigeria. The objectives of this study was to isolate and characterize the microorganisms associated with bean cake sold in Minna metropolis. Analysis of fried bean cakes was carried out to isolate and characterize the microorganisms associated with bean cakes sold in Minna Metropolis. The bacteria and fungi isolated were characterized using biochemical and molecular methods. Antibiotic susceptibility testing was carried out on the isolates to identify the antibiotic resistance profile, associated hazards and control measures were identified. The isolates identified were Aspergilus niger, Bacillus subtilis, Micrococcus roseus, Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli. The total viable bacterial counts ranged from 0.00±0.00cfu/g in Dutsen kura to 2.58±0.10cfu/g in F-layout while the coliform counts ranged from 0.00±0.00 cfu/g in Bosso and Dutsen kura to 1.75±0.11cfu/g in Kpakungu and fungal counts ranged from 0.00±0.00 in Tunga and Bosso to 2.66±0.18cfu/g in Maitumbi. Staphylococcus aureus, K, pneumoniae and M. roseus were susceptible to 45.45% of the antibiotics used while E. coli, B. subtilis and A. niger were susceptible to 31.98%, 27.27 % and 60% of the agents used. Critical control points were identified as milling and water used in mixing the paste. The results suggested that some degree of control can be exercised over the microbial hazard of kosai to prevent, eliminate or reduce microbial load to acceptable levels. There should be enlightenment campaign created amongst sellers and consumers of bean cakes.

CHAPTER ONE

1.0      INTRODUCTION

1.1      Background to the Study

Cowpea (Vigna unguiculata) is a legume popularly known as beans in West Africa (Moutaleb et al., 2017). Cowpea is nutritious and contains protein, vitamins and minerals. Cowpea has about 25% protein, making it extremely valuable for people who cannot afford proteins from animal sources such as meat and fish (Appiah et al., 2011; Oumarou et al., 2017). Cowpea can be processed as flour, paste, deep fried cake (akara) or steam bean pudding (moi moi) and bean soup eaten in several Western and Central African countries (Eke-Ejiofor and Kporna, 2019).

Bean cake known as “àkàrà” in Yoruba, “kosai” in Hausa, is a popular food in Nigeria, Ghana, Togo, Benin, Mali and Gambia (Aviara et al., 2018). It forms part of the diet of most ethnic groups in Nigeria. Nigerians usually eat it as breakfast with ‘ogi’, or lunch with ‘gari’ or even dinner with ‘eko’. Akara is a traditional African food made by deep frying cowpea paste that has been whipped and seasoned with salt, pepper, onions and other optional ingredients. The outer crust of Akara is crispy and the interior is spongy like bread. It is considered to be the most commonly consumed cowpea-based food in West Africa. Akara is made mainly from cowpea and other sources like maize, rice and flour. It can be fried with vegetable oil, palm oil, and other edible oils (Aviara et al., 2018).

Foodborne pathogens are microorganisms found in foods that are capable of causing diseases when consumed. Some foodborne microbes make people ill by forming toxins in foods that affect the gut or the neurological system. Foodborne pathogens include Salmonella typhimurium, Escherichia coli, Listeria monocytogenes, Clostridium perfringens, Bacillus subtilis, Bacillus cereus and Klebsiella pneumoniae. Foodborne pathogens associated with bean cake according to the findings of Lateef et al. (2016) are Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Citrobacter freundii, Serratia marcescens, Proteus vulgaris, Bacillus cereus, Streptococcus pyogenes, Aspergillus niger, Shigella spp and Bacillus spp.

The contamination of bean cake is largely due to post-processing operations such as unhygienic handling of bean cake with bare hands, exposing bean cake without covering it, talking when selling bean cake, using old newspapers that were not properly kept among others. These post- processing operations can be abated through the use of quality water, high level of personal hygiene and hygienic production materials (Toledo, 2018).

Examples of foodborne diseases caused by these organisms include; Salmonellosis and foodborne illness caused by E. coli O157:H7. Other foodborne diseases include: Amoebiasis, cholera, diarrheagenic E. coli, giardiasis, listeriosis, marine toxins shigellosis, travelers’ diarrhea, trichinosis (trichinellosis), typhoid, Vibrio parahaemolyticus and Vibrio vulnificus infection.  Symptoms  of  these  diseases  include  nausea,  vomiting,  abdominal  cramps and diarrhea.

One of the major problems associated with bean cake is its susceptibility to various types of spoilage such as staling, rancidity and ropiness, soon after its production. Bean cake starts to stale the minutes it leaves the fryer which makes its outer surface to become firm, harsh, opaque and crumblier. Bean cake has a poor shelf-life which has been attributed to its fat and high moisture content (Oumarou et al., 2017). Associated with the fat content is lipid oxidation while high moisture content in the product predisposes carbohydrate and protein in it to fermentation and putrefaction respectively causing ropiness by Bacillus subtilis (Oumarou et al., 2017).

In view of the problems associated with the consumption of bean cake, particularly if basic hygienic considerations are not observed after its production, this study was designed to evaluate the microbiological quality of bean cake from some selected sellers within Minna metropolis. The bacterial isolates were subjected to antimicrobial sensitivity test and molecular characterization with the view of establishing the public health implications of their occurrence in bean cake. In addition, the environment, raw materials and the procedure for preparing bean cake were monitored to identify sources of hazards and possible critical control points by applying the hazard analysis and critical control point (HACCP) strategy.

1.2      Statement of the Problem

The presence of microorganisms in food has always been attributed to contamination through water, soil, processing equipment, contact surfaces and the food handlers (Toledo, 2018). Improper handling of food is responsible for most cases of food borne diseases and cross contamination (Toledo, 2018). About 1 in 10 people in the world fall sick after eating food contaminated through improper farming, processing and preservation. In Nigeria, more than 200,000 persons die of food poisoning annually caused by the consumption of contaminated foods (Aviara et al., 2018).

Bean cake has a poor shelf life which can be attributed to its fat and high moisture content. Associated with the fat content is lipid oxidation while high moisture content in the product predisposes carbohydrate and protein in it to fermentation and putrefaction respectively, causing ropiness by Bacillus subtilis (Alum et al., 2016). The nutritional content of bean cake has predisposed it to microbial contamination. In 2010, in Bekwara Local Government Area of Cross River State, 2 children died and 122 people hospitalized as a result of food poisoning due to the consumption of moi-moi, a steamed cowpea paste delicacy (Alum et al., 2016).

There are multiple sources of contamination from the environment, and contaminants could enter the food during harvest, production, storage and selling of bean cake. And as such, it is imperative that bean cake, a cowpea base delicacy be examined for the presence of contaminants.

1.3      Justification for the Study

Bean cake is a common food consumed by Western and Central African countries especially in Nigeria. Several studies have reported the contamination of bean cake by pathogenic organisms  from  diverse  sources.  Lateef  et  al.  (2016)  investigated  the  microbiological examination and identification of hazards and critical control points of akara ogbomoso. Also, Ajibola and Adelekan (2017) investigated the storage stability of deep-fried cowpea products (akara) incorporated with soy-flour and Aframomum danielli, while China et al. (2019). Proximate composition and sensory assessment of beans pudding prepared using two different cooking methods and Hence, there is a great need to determine the microbial quality and identification of hazards and critical control points of bean cake sold in Minna Metropolis. Data generated will add to existing information on the microbiological quality of bean cake.

1.4      Aim and Objectives of the Study

The aim of this study was to isolate and characterize the microorganisms associated with bean cake sold in Minna metropolis.

The specific objectives of the study were to:

i.      isolate and characterize the microorganisms associated with bean cake sold in Minna metropolis.

ii.      compare the microbial quality of the bean cakes obtained from the market and the aseptically prepared bean cake in the laboratory.

iii.      investigate the susceptibility of these microorganisms to antimicrobial agents. iv.  identify the hazards and critical control points in the production of bean cakes.

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