ABSTRACT
The study evaluated the efficiency of co-extruded
polypropylene (PP) and low density polyethylene (LDPE) in extending the
shelf-stability of unam inung
traditional meat product during storage under ambient conditions. Fresh pork
was processed, in traditional way, into unam inung meat product and stored for 6 months, under ambient
room conditions as unpackaged, clay pot packaged (traditional method), and those
packaged in polypropylene (PP), low density polyethylene (LDPE) and co-extruded
polypropylene/low density polyethylene (PP/LDPE). Samples were withdrawn at
intervals of one month for evaluation of quality changes. Results show that the
storage room temperature (25.95-27.91oC) and relative humidity
(68.25-77.42%) are suggestive of typical diurnal conditions during the
beginning of rainy season in South Eastern States of Nigeria. Relative humidity
(RH) which was 69.55% at the beginning of storage reduced to 68.29% in the 2nd
month of storage and subsequently increased thereafter to 77.42% in the 5th
month of storage. Due to increasing RH from the second month of storage, all
products increased in moisture content, consequently leading to increases in
water activity and reduction in crude protein, fat and salt content due to
dilution effect resulting from mass action. These changes were greater in the
unpackaged and clay pot packaged samples due to greater access to air and
moisture but least in the PP/LDPE coextruded film due to greater restriction to
air and moisture transmission. Owing to increasing moisture and water activity
from the second month of storage, protein hydrolysis became the dominant
protein deteriorative reaction, leading to increases in protein solubility and
pH, particularly in the unpackaged but significantly least in the PP/LDPE
co-extruded plastic film. Thiobarbituric acid reactive substances (TBARS) and
free fatty acids (FFA) results suggest that both oxidative and hydrolytic rancidity
were occurring in the samples but the extent was very low and did not lead to
detectable rancidity in any sample. The reactions of the antioxidant vitamins
(A,C and E) must have been effective in preventing detectable rancidity, as
they all have significant (p<0.05) correlations {r(Vitamin C/TBARS) =
-0.743, r(Vitamin C/FFA) = -0.586, r(Vitamin A/TBARS) = -0.882, r(Vitamin
A/FFA) = - 0.794, r(Vitamin E/TBARS) = -0.753 and r(Vitamin E/FFA) = -0.831}.
All the vitamins continued to reduce during storage. Total viable count and
mould count significantly (p<0.05) increased in the unpackaged samples
throughout storage period presumably due to greater access to moisture and air.
These counts reduced in the plastic film packages, particularly PP/LDPE package,
probably due to restricted/lower availability of oxygen and moisture. Although
all the sensory attributes slightly reduced during storage, the reductions did
not lead to significant loss of acceptability. All deteriorative
reactions/changes were more adverse in the unpackaged samples and clay pot
packaged samples compared co-extruded PP/LDPE packaged samples. Thus, unam inung packaged with co-extruded PP/LDPE plastic film
is acceptable up to 6 months of storage at ambient room conditions without much
loss in quality. On the other hand, the unpackaged and clay pot packaged
samples showed much instability and spoilage that they were discarded after
about 3 and 5 months respectively.
TABLE OF CONTENTS
List of Figures
List of Tables
Abstract
CHAPTER ONE: INTRODUCTION
1.1 Background Information
1.2 Problem Statement
1.3 Objective of the Study
1.4 Impact/Significance of the Study
CHAPTER TWO: LITERATURE REVIEW
2.1 Purpose of Packaging Processed Meat
2.2 Factors Affecting the Shelf-Life of Meat and Meat Products
2.3 Packaging Materials for Meat Products
2.4 Co-Extrusion of Films
2.5 Meat Products
2.6 Salted Meat
2.7 Analytical Frameworks
2.8 Prediction of Shelf Life
CHAPTER THREE: MATERIALS AND METHODS
3.1 Sample/Material Procurement and Processing
3.1. 1 Preparation of Samples/Raw Materials
3.2 Temperature and relative of storage room
3.3 Chemical Analysis of Sample
3.3.1 Moisture Content
3.3.2 Crude protein
3.3.3 Fat Content
3.3.4 Water Activity
3.3.5 pH Determination
3.3.6 Salt (sodium chloride) content
3.3.7 Protein solubility
3.3.8 Thiobarbituric Acid Reactive Substances (TBARS)
3.3.9 Free Fatty Acid
3.3.10 Vitamin Analysis
3.3.10.3 Vitamin
3.3.10.2 Vitamin C (Ascorbic acid)
3.3.10.1 Vitamin E
3.4 Microbial Analysis
3.4.1 Total Viable Count
3.4.2 Mould Count Determination
3.5 Sensory Evaluation of Samples
3.6 Statistical Analysis
3.7 Microstructure Characterisation
3.8 Coefficient of Friction
CHAPTER FOUR: RESULTS AND DISCUSSION
4.1 Storage Temperature and Relative Humidity
4.2 Mechanical Properties
4.3 Results on Chemical Analysis of Samples
4.4 Microbial Analysis Results
4.5 Organoleptic Characteristics
CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion
5.2 Recommendations
REFERENCES
APPENDICES
CHAPTER ONE
INTRODUCTION
1.1 Background Information
Meat products have broad categories that require different types of packaging. Selection of packaging materials will depend on product factors such as colour stability, storage conditions, microbial condition, degree of processing preservative and attractiveness of the packs (Hotchkiss, 1994; Konieczny and Bilska, 2006). The packaging film must be a barrier against environmental influence in order to protect and preserve the product. Hence, the barrier requirement depends on the type of meat. Meats which are stored at room temperature for months (example, commercially sterile meats) must be protected from oxygen ingress and loss of water. Packaging must also provide a barrier against biological, chemical and physical agents that would detract from quality or safety (Ramsbottom, 1971; Proffit, 1991).
Packaging materials can be classified into metal, paperboard laminates, plastic and glass. Metal and glass are ideal materials for packaging meat; both have absolute barrier against molecular diffusion and provide good protection of the packed product according to the reliable hermetic seal and firmness of the container, but they require high packaging costs and are not flexible. Paperboard laminates and plastic containers reduce packaging cost considerably and are extensively flexible. Therefore, they are most frequently used in packaging systems, but do not have perfect barrier against matter and energy (Hotchkiss, 1994).
Plastics used now are petroleum derivatives, mainly thermoplastic resins. The four most economic plastics are polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP) and polystyrene (PS) (Dean, 1996). Plasticizers, colourants or anti-fog compounds may be added in their fabrication (USDA-FSIS, 2002). Thermoplastic films have gained a dominating position in the field of packaging over several decades, but in the last few years there has been a growing interest in co-extruded materials. The co-extrusion process enables the properties of different polymer resins to be combined in one film, since the requirements of a package cannot always be met by a single film. Co-extrusion of containers have the advantage of glass (Clarity, retortability and barrier properties) coupled with the advantages of safety (impact resistance), low weight, ease of shaping and printing. These have led to the opening of new markets in both food and medical disciplines (Fox, 1990; Mc Cormick and Tas, 2005). With advances in co-extrusion technologies,
The excellent gas, odour and water vapour properties of barrier materials have resulted in co-extruded products with a widespread market acceptance in a variety of end uses. These new developments in high barrier plastics are in line with the main objectives of packaging developments in today’s demanding world (Groof, 1993; SPI, 2005). The major increase in the use of multi-layer co-extruded films for packaging applications in the last few years is in the high barrier film area, particularly for products with high fat content (Fox, 1990). Consequently, this technique can be used to package some of our traditional meats like unam inung. Unam inung is a ready-to-eat pork product that is very popular in the South-South states of Nigeria. The product is traditionally prepared by heavily salting sliced pork which is then sun dried and packed in dry clay pot. It is most commonly served with cassava chips or boiled yam and plantain. The traditional production techniques especially in packaging have not been improved to cope with modern scientific requirements and with increasing demand (Hui, 2007).
1.2 Problem Statement
The demand for protein of animal origin in a developing country like Nigeria far outstrips the supply. An average Nigerian, for instance, consumes only about 10g per day of the minimum daily intake of 35g recommended by Food and Agricultural Organisation (FAO, 1992). The fast growth rate and the high prolific nature of pigs can close the gap of protein shortage. If pork products are made readily available at affordable cost, animal protein shortage will be alleviated (Ani and Okorie, 2004; Oboh et al., 2004).
Meat, traditionally preserved by drying, is made available sometimes in packaged linen bags, baskets or pottery to facilitate storage and transport and to provide some kind of protection against dirt, insects, etc. With teeming population of consumers, however, this traditional system now becomes outmoded because more time is needed between slaughtering and ultimate consumption. Meat frequently has to be stored, transported, prepared and distributed through a retailer or butcher of which is considerably time-consuming. In order to safeguard fresh meat during this extended time, certain methods of preservation have to be applied. Refrigeration is a type of solution, but this is expensive and therefore frequently not available in Nigeria. To extend the shelf-life of meat and meat products, proper packaging has an important part to play especially due to absence of refrigeration......
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