PRODUCTION PROPERTIES AND SHELF – LIFE OF INTERMEDIATE MOISTURE SNAIL MEAT

ABSTRACT

This  research  was  carried  out  to  study  the  influence  of  three  cooking  methods  (frying, smoking and roasting) on the physicho-chemical properties  and the shelf – life of snail meat (Achachatina  marginata). The snail meat was first washed using different  washing agents (lime,  alum,  salt  and  ash)  and  through  sensory  evaluation,  the  best  washing  agent  was selected and used to prepare snail meat samples for subsequent processing. The snail from the best  washing  agents  was  divided  into  4  portions  to  correspond  to  the  following  curing humectant which were used in cook-soak equilibration: salt alone, salt + glycerol, salt + k- sorbate and salt + k-sorbate  +  glycerol.  The cured samples were analyzed  for proximate composition, mineral, microbial characteristics and sensory properties. Portions of products from each curing solution were subsequently subjected to three different methods of cooking namely smoking, frying and roasting. These products were also stored at ambient conditions (280C – 320C) for 31days and analyzed at 6day interval for indices of shelf – stability which included water activity, protein solubility,  TBA values, pH and microbial  quality.  Results showed that lime – washed snail meat had the highest score for overall acceptability and had similar scores for color, odor, texture and proximate composition with samples washed with salt, alum and ash. Lime – washed snail meat was then selected for further processing. Curing with  various  humectants   did  not  lead  to  significant   differences   (p>0.05)  in  sensory characteristics except that samples cured with salt + glycerol + k-sorbate solution was judged to be tougher/harder and the color was neither liked nor disliked compared to others. Curing also reduced the moisture content due to osmotic dehydration but due to concentration effect, increased the protein, fat, ash, zinc, total pigment and pH. Among the cured products, those containing glycerol were higher in moisture content but lower in water activity. The different methods of cooking/preparation (smoking, frying, roasting) had different effects on the shelf stability  of the products. In all the 3 methods, samples containing glycerol were lower in water  activity,  protein  solubility,  lipid  oxidation  (TBA),  pH  and  total  viable  count.  The differences caused by curing humectants were maintained during storage. Products  treated with salt and those treated with salt + k-sorbate were so unstable that  incipient  spoilage, which set in caused discontinuation of storage after 1-2 weeks. Smoking caused all the cured snail meat products to be stable throughout  the thirty-day  storage. Roasted products were least stable during storage; hence, samples cured with salt alone and those cured with salt + k-sorbate spoiled in 7 days in the roasted samples.

1.1      Background Information

CHAPTER ONE

INTRODUCTION

Food security is a major problem in the developing countries of the world. Diets of an average citizen in this region is carbohydrate based with little or no protein source  with a great potential of reducing insulin level in the blood of the consumer. Moreover, consumption of animal protein, which is known to be a better source of this nutrient, is extremely low in this  region  (Omole,  1999).  Cases  of  malnutrition  are  more  prevalent  in  the  developing countries than  in other parts of the world. Consequently, thousands of children die every year of starvation and malnutrition (FAO, 1996). Animal production is faced by many problem in the  developing  countries,  for  instance,  high   cost  of  animal  feed  constitutes  a  major impediment in most projects as a result of continuous competition between man and animal for most of the ingredients (Adeyemo and Longe, 2001). Animal protein is superior to plant protein as it contains all the essential amino acids in adequate proportions (Tewe, 1997).

Low  consumption  of animal  proteins  in the developing  countries  is borne  out  of poverty and ignorance. Unavailability  and low production of livestock are indeed a  major problem. It is very clear that regular livestock can no longer meet the demands of the fast growing  population  of  the  world.  Therefore,  there  is  an  urgent  need  to  encourage  the production of   mini livestock such as snails, insects and rodents to supplement the current livestock production (Afolayan, 1992).

Snail is one of the mini livestocks with great potentials. The meat is a delicacy for many people both in the rural and urban centers of Nigeria and in many countries in Africa. It is a major source of meat to people in the rural communities where the majority cannot afford the cost of regular livestock meat (Emevbore, 1990). Snail meat has a special taste and is rich in iron, calcium and phosphorus. It is low in fat and cholesterol (Afolayan, 1992). It is high in quality protein, as it contains all the essential amino acids in adequate proportions. In fact, the amino acid profile compares favorably with those of broiler, fish and pork (Omole, 1999). This makes its consumption beneficial and safe to the consumers. This known nutritive value of the snail makes it unthinkable not to harness it for human benefits in view of acute protein shortage. Thus, the idea of its preservation comes in. This is because what is obtained from major sources of meat supply can no longer sustain the growing demand due to increases in human population. In order to bridge the gap between demand and supply of animal protein, preservation of meat is, therefore, necessary. The principles of meat preservation are mainly associated with preventing or delaying microbial spoilage and chemical actions and avoiding, as far as possible, weight loss and any change in color, taste, odor, flavor and texture (Cooper and Ledward, 1993).

Preservation methods are designed to prevent deterioration of meat and are absolutely essential  for  extending  the  keeping  quality  during  storage  of  meat  and  meat  products. Methods of preservation  include the use of infusion humectants and  curing ingredients to produce   intermediate   moisture   meats,   refrigeration,   freezing,   thermal   processing   and dehydration while including drying and smoking as well as preservation by use of chemical additives, generally recognized as safe.

Intermediate moisture meats (IMM) are semi moist shelf-stable-meat  that owe their stability to the infusion humectants  which, besides being antimicrobial,  depress  the water activity (aw) to limits (mostly 0.70-0.85) below the growth requirements  of  most bacteria. Intermediate  moisture  meats can also be defined as heterogeneous  group  of meats which resemble dry meats in their resistance to microbial deterioration but which contain too much moisture  to be considered  dry (Brockmann,  1970;  Obanu  et al. 1975b).  An intermediate moisture meat has been described as one that can be eaten directly without rehydration, and yet is shelf stable, without refrigeration or thermal processing (Kaplow, 1970). This stability of relatively moist meat is the result of depressing the aw  below the growth requirement of most spoilage and pathogenic microorganisms (Anon, 1972; Brockmann, 1970).

1.2      OBJECTIVES OF STUDY

1)  To compare shelf stability of smoked, fried and roasted snail meat pretreated   with solution containing Sodium chloride, Glycerol and Potassium sorbate.

2)  To  assess  the  physical,  chemical,  microbial  and  organoleptic   qualities  of   the intermediate moisture (IM) snail meat.

3)  To assess the quality changes under ambient room storage condition (280C – 300C ) of intermediate moisture products.

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