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Introduction:

Abstract

The antimicrobial action chitosan was investigated in this study. Chitosan was produce from snail shell, samples of okpa were prepared from chitosan (antimicrobial agent) of different concentrations (0.2, 0.6 and 0.10) and untreated okpa without chitosan was prepared and used as control. The okpa sample were packaged with cellophane, steamed for 1 hour, cooled and stored at ambient temperature (28%) for 24 hours, 48 hours, 72 hours, 96 hours. Microbial analysis of okpa sample was carried out and identified microorganism was: bacteria of the species; micrococcus, bacillus, pseudomonas, staphylococcus and enterobacter, fungi of the species; Rhizopus and yeast. The chitosan treatment inhibited the microorganisms mostly at higher concentration (0.10). The results are indicated that chitosan’s antimicrobial action is concentration dependent.

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Introduction

INTRODUCTION



Microorganisms pose significant contamination risk in food for human consumption and are the chief agent responsible for spoilage of food. The principles involved in the method of food preservation are primary based on the control of the growth and activities of these microorganisms. The microorganisms responsible for food spoilage may be classified into three broad group mold, yeast and bacteria (okaka, 2005).



Bacteria such as staphylococcus aureaus and clostridium botulinum produce toxic substances while growing in certain foods, and bring about food intoxication when consumed. Food infections result from life ingestion of pathogenic organism especially bacteria, specie of the genus salmonella which invariably multiply once consumed, producing the disease (okaka, 2005).



Food stability is a major determinant of the shelf food products. Development of processes that specifically improve food stability is needed and has been the goal of mankind throughout history. What began in an empirical way with few simple processes such as smoking and salting is now a precise science, and modern food technologists have a wide range of preservative compounds at their disposal. There are concerns; however, over the long term health effects of many foods develop novel natural antimicrobial systems for use in foods and food related applications and to reduce dependence on traditional preservation (Rhoades and Rastall, 2004).



Chitosan is a technologically important and ubiquitous polysaccharide biopolymer produced by partial alkaline N-deacetylation of chitin which is commercially extracted from shrimps and crab shells. Chitosan combines unique biological characteristics which allow for a wider range of application, including biodegradability, biocompatibility and non-toxicity. Chitosan has emerged as a new biomaterial for food, pharmaceutical, medical, Textile, Agricultural and other industries, as well as waste purification (Babel et al, 2003).



In food industry, it has been shown that chotosan posses strong antimicrobial activity against both gram positive and gram negative bacteria including the food born pathogen such as Escherichia coli, Staphylococcus aureus, and Salmonella typhemurim. Antimicrobial activity of chitosan is influenced by several factors which can be intrinsic and extrinsic. It has been noted that lower molecular weight chitosan have high antimicrobial activity than native chitosan (Takia et al 2002).



In recent years, chitosan and its derivative have attracted much attention as agents against fungi, bacteria and viruses, and as elicitors of plant defense mechanisms. In fact, a number of commercial applications of chitosan benefit from its antimicrobial activities, including its use in food preservation. Chitosan antimicrobial mode of action is more complex than assumed; it is not confined to as single molecular, but that killing results from a sequence of rather untargeted molecular events taking place simultaneously or successively (Bable et al 2003).



Okpa (Bambara groundnut), voandzeia subterranean or vigna subterranean originated in West Africa and are grown primarily for its seed, which are eaten fresh as vegetable when semi-ripe, and as a pulse when dry and mature. They may be ground into flour which is used to prepare a popular steamed product known as ‘Okpa Snack’. Okpa is referred to as a complete food because it contains carbohydrate, fat, minerals, vitamins, ploy-phenols and a major source of protein in sub-saharan are the taste, firmness of the gel and the orange yellow colour imparted to the product by the red palm oil used in its preparation (Brink et at, 2006).