ABSTRACT
Two experiments were conducted. The first evaluated beef smoked using different plant materials (Acacia raddiana, Eucalyptus camaldutensis, Azadirachta indica and Cocos nucifera) as source of smoke. The effect of the plant materials on the organoleptic, microbial and physicochemical properties of smoked beef was evaluated. In the second study, Suya was produced from various round muscles (Rectus femoris, Semi-tendinosus, Biceps-femoris, Semi membranosus and Vastus lateralis) and evaluated for organoleptic, microbial and physicochemical properties. Both studies were carried out in a completely randomized design. The result showed that there was no significant (P>0.05) difference among sources of fuel wood tested on the overall acceptability of smoked meat. However, organoleptic scores on a five point hedonic scale were lowest (2.50) for beef smoked with C. nucifera and highest (3.30) for beef smoked with A. raddiana (Standard check). The pH values were within the accepted limit (5.5-6.5). Percentage thermal shortening were not significantly (P>0.05) different. Percentage Water holding capacity was highest (13.6) in beef smoked with C. nucifera. Total viable counts/ Aerobic plate count, coli-form counts were all within satisfactory limits (i.e. <½ million/g). In the second study, the fat content was not significantly (P>0.05) affected by the muscle types. The score for overall acceptability indicated that the consumers preferred Biceps femoris which was significantly (P< 0.05) different from other round muscles. Water holding capacity was observed to have influence on other qualities such as the flavour, juiciness and tenderness. Product yield was lowest (70.20 %) in Vastus lateralis, indicating a good yield from all muscles. Microbial load of all suya samples fell within satisfactory limit with reference to the standard microbial load specification (i.e. <½ million/g). It was concluded that Eucalyptus camaldutensis (Turare), Azadirachta indica (Neem) and Cocos nucifera (coconut shell) are good sources of fuel wood and can be used as an alternative to Acacia raddiana for smoking beef. Furthermore, smoke had an antimicrobial and antioxidant effects as the microbial load were all within satisfactory limit. From the results of the second study, it was concluded that the prime cuts, apart from resulting in Suya with high prices are not necessarily better than Suya from less choice parts of the carcass (Semi-membranous, Semi-tendinosus, Biceps femoris, Rectus femoris and Vastus lateralis) in terms of product yield and eating qualities
TABLE OF CONTENTS
Title page ………………………………………………………..………………….
I
Declaration ……………………………..…………………………………………….
Iii
Certification……………………………………..…………………………………….
Iv
Dedication…………………………………….…………………………………….
V
Acknowledgement …………………………………………………………………
Vi
Abstract……………………………………………………………………………..
Vii
Tables of contents…………………………………………………………………..
Iix
List of tables……………………………………………………………..………….
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CHAPTER ONE
1.0 Introduction …………………………………………………………………… 1.1 Justification of the study ……………………………………………………… 1.2 Objectives of the study….…………………………………………………..… 1.3 hypothesis…… ……………………………………………………………..…
1 3 4 4
CHAPTER TWO
2.0 Literature Review …………..…………………………………………………
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2.1 Domestication of animal for meat……………………………………………..
5
2.2 Growth and development of meat animals…………………………………….
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2.2.1 Genetics………………………………………………………………………
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2.2.2 Environmental factors……………………………………………………….
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2.2.3 Nutrition……………………………………………………………………..
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2.2.4 Human Interventions…………………………………………………………
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2.3 Meat Composition…………………………………………………………….
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2.4 Biochemical Changes: from Muscle to meat …………………………………
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2.5 Acidity in Meat……………………………………………………………….
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2.6 Meat quality parameters ………………………………………………………
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2.6.1 Tenderness…………………………………………………………………
10
2.6.2 Meat Colour……………………………………………………………….
11
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2.6.3 Cooked meat …..………………………………………………………….
12
2.6.4 Effect of meat pH….……………………………………………………..
12
2.7 Meat Smoking ………………………………………………………………..
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2.7.1 Composition of Smoke ……………………………………………………
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2.7.2 Plant Materials Used for Smoking….………………………………….…
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2.7.3 Smoke House……………………………………………………………. 2.7.4 Effect of Smoking on Meat…………………………………………….. 2.7.5 Health Risk of Smoked meat……………………………………………. 2.8 Suya………………………………………………………………………… 2.8.1 Characterization of connective Tissue of Bovine Skeletal Muscle……. 2.8.2 Cuts of Beef……………………………………………………………. 2.9 Meat Spoilage………………………………………………………………. 2.9.2 Effect of Temperature on meat spoilage……………………………… 2.9.3 Effect of water Activity on meat spoilage……………………………. 2.9.4 Effect of Gas Tension on meat spoilage……………………………… CHAPTER THREE
17 18 19 20 21 23 24 25 25 26
3.0 Materials and Methods ………………………………………………………
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3.1 Study Location……………………………………………………………….
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3.2 Sample collection and preparation for Smoked Beef………………………..
28
3.3 Smoking of meat…..…………………………………………………………
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3.3.1 Construction of smoking ovens………………………………………………
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3.3.2 Meat distribution in smoke ovens…………………………………………… 3.3.3 Smoke cooking procedure………….………………………………………..
29 29
3.4 Sample preparation for Suya…………………………………………………
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3.4.1 Ingredient reparations …… ………………………………………………….
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3.4.2 Preparation of Suya……………………………………………………… 3.4.3 Roasting Process…. ………………………………………………………
31 31
3.5 Sensory Evaluation………………..…………………………….…………. 3.6 Physical Composition of smoked beef and Suya samples….……………….
32 32
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3.6.1 Determination of Percentage Cooking Loss……………………………….. 3.6.2 Determination of Percentage Moisture content……………………………. 3.6.3 Determination of Percentage Thermal Shortening………………………… 3.6.4 Determination of Water Holding Capacity………………………………… 3.6.5 pH Determination of smoked beef and suya………………………………. 3.7 Proximate Composition of smoked beef and suya ………………………… 3.8 Microbial Analysis…..…………………………………………………….. 3.8.1 Materials…………………………………………………………………… 3.8.2 Preparation of Media for Fungi Isolation………………………………….. 3.8.3 Isolation of Fungi………………………………………………………….. 3.8.4 Characterization of fungal Isolates………………………………………… 3.8.5 Bacterial counts ……………………………………………………………. 3.8.6 Bacterial isolation by selective plating…………………………………….. 3.8.7 Colony Identification………………………………………………………. 3.8.8 Biochemical Testing……………………………………………………….. 3.9 Statistical Analysis………………………………………………………… CHAPTER 4
32 31 31 33 34 34 34 34 35 35 35 35 36 36 37 37
4.0 RESULTS …………………………………………………………………
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4.1 .1 Proximate Composition of smoked beef…………..………………………
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4.1.2 Proximate Composition of Suya…………….……………….……………
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4.2.1 Organoleptic assessment of beef smoked using different plant materials…
40
4.2.2 Organoleptic assessment of suya samples.…. ………………………………
42
4.3 Physical Parameters of samples……………………………………………. 4.3.1 Physical Parameters of Smoked Beef……………………………………… 4.3.2 Physical parameters of suya……………………………………………….. 4.4 Total Viable Counts, Coli-form Counts……………………………………. 4.4.1 Total Viable Count, Coli-form counts of Smoked Beef…………………… 4.4.2 Total viable counts/ Total Aerobic and coli-form count of suya……………. 4.5 Biochemical Test Results……………………………………………………
42 43 43 46 46 46 47
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4.5.1 Biochemical Test of Salmonella in Smoked beef samples…………………. 4.5.2 Biochemical Test Results for Salmonella on Suya Samples………………. 4.5.3 Biochemical Test Results for E. coli on Smoked Beef…………………….. 4.5.4 Biochemical Test Results for E. Coli on Suya Samples…………………… 4.6 Xerophilic Fungi Isolated…………………………………………………… 4.6.1 Moulds associated with Smoked beef.……………………………………… 4.6.2 Moulds associated with Suya Samples……………………………………… Chapter 5
47 47 50 50 50 50 50
5.0 Discussion ………………………………………………..…………………
56
5.1 Proximate and Mineral Composition of Smoked Beef………………………
56
5.2 Proximate and composition of Suya from various round muscles……………
57
5.3 Mean sensory score for organoleptic parameters of smoked beef.…………..
58
5.4 Mean sensory score for organoleptic parameters of suya……………………
60
5.5 Physical parameters for smoked beef…………. …………………………….
61
5.6 Physical Changes in Suya samples…..………………………………………
61
5.7 Total Viable Counts, Coli-form counts of smoked beef ……………………
62
5.8 Total Viable counts, coli-form counts of suya………………………………
63
5.9 Biochemical test for staphylococcus, salmonella and E. coli……………….
64
5.10 Moulds associated with smoked beef samples ………………………………
64
CHAPTER SIX
6.0 Conclusions and Recommendation ………………………………………….
66
6.1 Conclusion……………………………………………………………………
66
6.2 Recommendation……..………………………………………………………
66
REFERENCES…………………………………………………………………….
67
CHAPTER ONE
1.0 INTRODUCTION Meat has been defined as the flesh of animals which is suitable as food. Meat makes a valuable contribution to diets because of its high biological value and an excellent source of amino acids, vitamins and minerals (CAST, 1997). A daily intake of 100 g of meat can supply up to 50% of the recommended daily allowance for Iron, Zinc, Selenium, Vitamins B1, B2, B6, B12 and 100% of vitamin A (Biesalski and Nohr, 2009). In Nigeria there is a preferential consumption of different types of meat by communities due to a combination of factors bordering on religious belief, culture, food habits, sex of animal, age at slaughter, socio-economic factors and individual variation (Ajiboye et al., 2011). Meat being nutritious with high moisture content and nearly neutral pH is a good culture medium for many micro-organisms (bacteria, yeasts and moulds) and as such, classified among perishable foods whose contamination with spoilage organisms are almost unavoidable (Ikeme, 1990). This makes meat preservation more difficult than other types of food as it may result in oxidative rancidity, discolouration, off flavour, sliminess etc. The kind and amount of spoilage organisms in meat depends upon the availability of nutrients, presence of oxygen, temperature, pH at storage and generation interval of the spoilage microorganism under given environment etc. (Forrest et al., 2001). It is necessary to minimize deterioration in order to prolong the time during which acceptable levels of quality are maintained. This depends upon the processing and preservative method used and the inherent properties of the meat in question (Forrest et al., 2001).
Different methods of meat preservation have been used through out history. These include, the use of high temperature (e.g. roasting), Low temperature (e.g. chilling, freezing and
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pasteurization), Drying (e.g. hot air drying, wind and sun drying) and the use of Chemical preservatives. Meat smoking as a method of red meat preservation dates back to prehistoric time. Smoking involves the use of wood fuel which in turn affects product quality. Smoking improves flavor and appearance of meat (Cardinal et al., 2006), making them a delicacy in many communities. Smoking is normally used in combination with salting. The moisture content drops to 10-40 % depending on the smoking process. Preservation by smoking is achieved by dehydration and antibacterial effect of the smoke. During the smoking process, smoke components penetrate the meat to produce a stable and sensory acceptable product. Smoked meat has good shelf life unless rehydrated. Handling and storage methods are primarily concerned with minimizing microbial contamination and retarding microbial growth and activity (Benjakul and Aroonrueng, 1999).
The second phase of this study involves Suya, a spicy barbecued, smoked or roasted meat product. Suya is one of the Intermediate Moisture Meat (IMM) products that is easy to prepare and highly relished (Omojola et al., 2004). It originated from the Hausa people of northern Nigeria, where rearing of cattle is an important occupation and a major source of livelihood for the people with the preparation process carried out under largely unhygienic conditions with high risk of contamination (Abdullahi et al., 2004). The humid tropical environment encourages the breeding of flies which swarm and perch on meat displayed for sale. These constitute a major nuisance and can aid in the spread of disease agents of significant public health importance (Okoli et al. 2006). The fact that there are sporadic cases of gastroenteritis and symptoms of food infection after consumption of Suya indicate that the product indeed constitutes a food safety risk (Odusote and Akinyanju, 2003). Similarly, most of the bacteria causing diarrhoea are zoonotic (transmissible between animals and humans) and reports by FAO/WHO (2003) shows that Cholera, Salmonellosis, Campylobacteriosis, Shigellosis,
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Typhoid, Brucellosis, Poliomyelitis, and Escherichia coli infections are prevalent. Although cooking temperature kills most pathogen, a few may withstand the cooking temperatures. Moreso, suya can be re-contaminated by food handlers during processing or from the environment (Wagner, 2010). 1.1 Justification of the Study In Nigeria, exact statistics of storage losses of smoked meat is not available, but observations reveal that post processing losses of smoked meat do occur during storage. Therefore, any reduction in processing and post processing loss by simple modifications of existing methods will benefit the meat sellers as well as introduce newer varieties of meat products. If found to be effective on meat, the use of E. camaldutensis (Turare), Neem and coconut shells as wood source may ease pressure on local trees like A. raddiana (Doka) and Mangroves. Traditionally, most Suya producers use expensive cuts of meat (examples is the Longissimus dorsi muscle) resulting into high prices of the products beyond the reach of the common man. The prime cuts apart from resulting in product with high prices might not be better than cuts from less choice parts of the carcass in terms of product yield and eating qualities. Hence, the need to convert low priced meat cuts into relished processed products by meat processors. Accurate information on the prevalence and impact of foodborne disease are lacking. Thus, there is a need to determine the occurrence and load of micro-organism from smoked beef and suya.
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1.2 Objectives of the Study
1. To determine the effect of using different plant materials (Acacia raddiana (Doka), Eucalyptus camaldutensis (Turare), Azadirachta indica (Neem) and Cocos nucifera (coconut shell)) as smoke source on sensory and physical characteristics of smoked beef.
2. To determine the organoleptic properties and shelf life of beef suya made from different cut of carcass.
3. To determine the microbial and physical parameters of smoked beef and Suya.
1.3 Hypothesis This research therefore, was designed to evaluate the following null hypothesis (HO) and alternative hypothesis (Ha) Ho: Smoking of beef with different plant materials has no effect on the Organoleptic and Preservative properties of smoked beef. Ha: Smoking of beef with different plant materials has effect on the organoleptic and preservative properties of smoked beef.
Ho: Suya produced from different beef cut (round muscles) have no effect on the organoleptic and Preservative properties of Suya. Ha: Suya produced from different beef cut (round muscles) have effect on the organoleptic and preservation properties of suya.
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