MICROBIAL CONTAMINATION OF CUT AND EXPOSED ONIONS

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Description

CHAPTER ONE

INTRODUCTION

1.1 BACKGROUND TO THE STUDY
Onions, scientifically referred to as Allium cepa is a vegetable plant that possesses various culinary and medicinal importance. They originated from central Asia, but now have a worldwide distribution. They are consumed for the several nutritional and medicinal properties they contain. Depending on the variety, and growing conditions, the nutritional value may vary (White and Zellner, 2019). They are cholesterol free, very low in calories, fat, sodium and, a good source of vitamin B6, potassium and the flavonoid quercetin and the trace mineral chromium (White and Zellner, 2019).
Onion is one of the most commonly consumed vegetable crops in the world with China being the number one producer of onions while Japan and India are the second highest producers of green onions and dry onions respectively. Nigeria, ranks sixth amongst the top ten producers of green onion, and eleventh in terms of dry onion production. In Nigeria, onion is grown mostly in Kano, Kaduna, Jigawa, Sokoto, Plateau, Bauchi and Kebbi states. (Brewster, 2018). According to statistics and data research, Nigeria had a world share of 5.5% out of a total of 4,339,925 tons of green onions produced in 2012 and a 1.6% share of a total of 82,815,92 tons of dry onions produced around the world. In most cases the crops is grown from its bulbs which are harvested in most countries once a year and are used daily in every home for seasoning and flavouring of foods. Onion is a valuable ingredient in the diet due to its content of sugars, vitamins, minerals, electrolytes, proteins and dietary fibre. Different varieties of onions are grown in Nigeria some of which is the Red creole a brilliant red short daily variety with medium-sized flattened bulbs. It is a popular standard variety in high demand because of its good keeping quality. It produces mainly single onions from transplants and has a pungent taste (Brewster, 2018).
White Cerole is a short day onion variety it produces onions with an exceptional great keeping quality. The bulbs are firm, small to medium in size with a thick flat shape. They also have a pungent smell with dehydration. Red Tropicana FI Hybrid is a high yielding large, red, thick-flat onion with firm pungent flesh. It is a highly productive and widely adaptable hybrid that needs good management. It is resistant to common fungal diseases. It should be kept in dry well aerated conditions. “Bombay Red” is a variety for dry and warmer conditions. It is small to medium sized, globe shaped, purplish red and pungent. This is a popular short-day variety in India. It is suitable for dry and warm conditions with wide acceptance in home gardens. Bulbs are medium-large, semi round in shape and red in color-flesh, it is firm and pungent. Medium-late maturity. Green bunching is a non-bulbing spring onion. Numerous benefits have been attributed to onions including prevention of cancer and cardio-muscular disorders, reduction in the blood levels of cholesterol, reduction in osteoporosis, reduction in stomach ulcers, inhibition of the proliferation of cultured ovarian, breast and colon cancer cells, inhibition of platelets mediated thromboisis, prevention of inflammatory processes associated with asthma, treatment of fever, common cold, cough, sore throat and its use as an antimicrobial pigment (Brewster, 2018). Despite the many benefits ascribed to onions, several rumours have spread concerning the ability of cut or exposed onions to serve as a sponge for microorganisms and other disease causing agents

1.2 STATEMENT OF PROBLEM
Everyday vegetables are being consumed in massive amounts. The onion that is affected by microbes or contaminated by microbes when consumed leads to very severe health problems. These microbes that enhance this spoilage are Streptococcus pyrogenes, Esherishia coli, Pseudomonas aeroginosa, Morgorellamorgonii, Staphylococcus aureus, Staphylococcus saprophyticus, Bacillus pumilis, Bacillus lensus, Staphylococcus capilis, Streptococcus sciuri, Baciluslensus, bacillus antracis, bacillus subtilis, streptococcus equines, Mucor, Yeast, Aspergillus niger, Aspergillus flavus, Fusarium oxysporum, Penicilliumdigitatum. The proper storage of onions makes it available all year that is why this study is being carried out to minimize the spoilage of onions if possible.

1.3 JUSTIFICATION OF THE STUDY
Pathogens such as: Pseudomonas sp., Staphylococcus sp. and Erwinia sp., were identified with the crop (Dogondajiet al., 2015) and this often reduces germination, and yield of the crop. Pathogen attacks result in a decreased rate of plant photosynthesis (Kocalet al., 2018) and as a consequence yield loss (Berger et al., 2017). Pathogen infection often leads to plant death, the development of chlorotic and necrotic (Kim et al., 2010) lesions and to a decrease in photosynthetic assimilate production. Hence this study was carried out to evaluate the microbial contamination of cut and exposed onions.

1.4 AIM AND OBJECTIVES
The aim of this study is investigate the microbial contamination of cut and exposed onions

OBJECTIVES
• To cut and expose three different onions in the kitchen
• To absorb microorganisms from the atmosphere on exposed onions
• To find out the type of microorganisms involved in the spoilage of the cut and exposed onions

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