ABSTRACT
Beef sold at retail markets can be contaminated with microorganisms which are of public health significance and impact on the shelf-life of meat. This study determined the influence of acid and alkaline decontamination interventions on the shelf-life of beef sold in retail markets in Zaria metropolis. Lactic acid (LA) and Trisodium phosphate (TSP) in two different volumes [1 liter (1L) and 2 liters (2L), respectively] were evaluated for their bactericidal effects on the bacterial population of beef sold in retail markets in Zaria. One hundred grams each of 216 beef samples were obtained from three retail markets: Samaru, Tudun-wada and Sabon gari; seventy-two samples (72) per market. Convenience sampling procedure was employed for sample collection. Twenty four out of 72 beef samples from each market, were sprayed on both sides for 10 seconds with LA (12 samples with 1L treatment and 12 with 2L treatment); a total of 24 meat samples were treated with TSP (12 samples with 1L treatment and 12 samples with 2L treatment) and another 24 samples with water (control) (12 with 1L and 12 with 2L). Sprayed samples were allowed to drip for 5mins and then maintained at 4oC. Treated meat samples were evaluated for Aerobic Plate count (APC), Total Coliform count (TCC) and the presence of E. coli on days 0, 3 and 6 of storage. Two-way ANOVA was used to compare effect of various treatments on APC, TCC and isolation rate of E. coli. Generally, the mean log reduction values (CFU/ml) between days 0 and 6 for APC and TCC either increased or decreased for all the markets sampled. There was a significant difference recorded for the 1L (p<0.05) and 2L LA (p<0.001) treatment for Tudun-wada and Sabo markets, respectively as compared to the control giving 1.3 and 2.4 log cycle reductions respectively. TSP gave no significant reductions (p>0.05) from the control. Although, treatment gave better reductions than the TSP treatment on the microbial load, other treatments with LA were not significantly different (p>0.05) from the control group. The effect of the decontaminants on the isolation rate of E. coli indicated that LA was effective against E.coli species, when compared to the control. Although, TSP treatment reduced E. coli consistently, the frequency of isolation was generally higher than what was obtained for the control and the LA-treated group on day 0 of storage. Beef samples treated with LA did not affect the aesthetic sensibilities of the consumer and a higher preference (57 %) was recorded for the treated roasted beef samples than the control (14 %) in terms of its appearance, smell and taste. Overall, the findings of this study revealed that the influence of LA and TSP treatment was not overly effective in prolonging the shelf-life of beef samples sold in retail markets in Zaria metropolis. Meat samples with LA treatments however showed lower isolation rate of E. coli thereby increasing the shelf-life. Good hygienic measures should therefore be employed during meat processing so as to increase its shelf-life and generally improve food safety.
Keywords: Lactic Acid, Trisodium Phosphate, Shelf-life, Beef, Retail markets
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of the Research Study
Meat is a nutritious and protein-rich food, which is highly perishable. It has a short shelf-life when good preservation methods are not used (Olaoye and Onilude, 2010). It is an important source of fats, vitamins and essential minerals. It is a high quality protein source that contains almost all the essential amino acids required in the human body (Lafarga and Hayes, 2014; Klurfeld, 2015), making it suitable for use as food. Meat, though considered being highly desirable and nutritious, is also highly perishable. This is because it provides the nutrients needed to support the growth of many types of microorganisms (Buncic et al., 2014). Due to its unique biological and chemical nature, meat undergoes progressive deterioration from the time of slaughter of an animal until consumption. Spoilage of meat has remained a serious challenge in developing countries, including Nigeria, for decades (Olaoye and Ntuen, 2011). This has been due to poor storage systems in such countries where necessary facilities that could help promote preservation are unavailable. Where available, unsteady power supply necessary to maintain such facilities has however constituted a serious problem, thereby rendering them to function below their maximum capacity. Furthermore, the ambient temperature in developing countries that are in tropical regions is usually about 30 oC or above. Meanwhile, most spoilage organisms have been found to have their optimum growth temperature within such range (30 OC – 45 OC) (Faid and Ahami, 2004; Olaoye and Ntuen, 2011). Meat surfaces are also known to contain several microorganisms (Bibek, 2005; Ireneous, 2008), some of which are reported to cause zoonotic diseases in humans (Norrung and Buncic, 2008). Spoilage by microbial growth is the most important factor in relation to the keeping quality of meat (Tajkarimi et al., 2010). Meat can also be a source of resistant bacteria, which could potentially be spread to the community through the food chain (Gousia et al., 2011), making decontamination imperative. Decontamination of meat carcasses is primarily aimed at the elimination of microorganisms. These organisms inevitably contaminate meat carcasses during dressing operations without irreversibly deteriorating the sensory quality. The disinfection of fresh warm carcasses prevents the spread of pathogens from contaminated meat carcasses to other sound meat carcasses in the chilling rooms, the meat environment and the initial sterile muscle meat during butchering operations. Acid or alkaline decontamination of meat carcasses exploits principally an immediate bactericidal activity, whose lactate anion slows down the growth of surviving microbes during storage (Dincer and Baysal, 2004; Siragusa, 1995). Organic acids have been of considerable value as food preservatives. They are also food ingredients and often naturally produced by microorganisms (Theron and Lues, 2007). Use of organic acids reduces bacterial counts in the meat surface layer. Lactic acid is often used because it is a natural meat compound produced during post-mortem glycolysis. Trisodium phosphate (TSP) is a highly alkaline compound which is usually applied as dip or spray of pre-chilled or chilled poultry carcasses (Capita et al., 2002; Oyarzabal, 2005). The alkalinity of TSP causes bacterial death through disruption of cell membrane (Mendonca et al., 1994; Sampathkumar and Khachatourians, 2003). It acts as a detergent that removes fat from the surface of poultry carcasses, consequently, increasing its killing action (Kim et al., 1994). Trisodium phosphate is an acceptable decontaminant because it does not affect the sensory quality (smell, colour, flavor, texture and overall acceptability) of carcass treated with its solutions, even as high as 8 and 10 % (Capita et al, 2000; Okolocha and Ellerbroek, 2005). Therefore, since there are no indications that these chemical decontaminants could in any sense endanger human health, there is a need for effective reduction of the number of contaminating microorganisms of public health significance on the surface of meat carcasses. An effective decontamination operation could also anticipate increasingly stringent demands for improved meat hygiene.
1.2 Statement of Research Problem
Contaminated raw meat is one of the major sources of food-borne illness (Bhandare et al., 2007; Podpecan et al., 2007). Poor meat handling, transportation and sales practices subject meat to contamination leading to poor quality and exposure of human consumers to health risks (Adeyemo et al., 2009). The levels of contamination in traditional/retail meat shops are significantly higher than found in abattoir (Bhandare et al., 2007). In most developing countries including Nigeria, the absence of the existing hygienic practices in slaughtering, transportation and marketing has been found to be one of the major causes of meat contamination by pathogenic and non-pathogenic microorganisms (FAO, 2004). In Zaria, high microbial load have been seen for meat purchased at retail markets for minimum counts of the microbial load exceeding even the allowed permissible value having counts as high as 6.0 log10 and 4.7 log10 for the Aerobic Plate Counts and Total Coliform Counts respectively (Lawan et al., 2011). This microbial surface contamination has been repeatedly reported to have a significant effect on the meat shelf-life. Moreover, healthy-food producing animals can be carriers of important bacterial pathogens causing human illness (EFSA/ECDC, 2014). Such pathogens might enter the food chain by direct or indirect faecal contamination if good hygiene practices are not warranted thereby spreading such diseases as salmonellosis, cholera, E. coli food poisoning and listeriosis caused by meat contamination. This constitutes a serious public health concern (Neil et al., 2002; Zweifel et al., 2014).
1.3 Justification
Microbial food safety is also of increasing public health concern worldwide. Raw beef sold at retail outlets in Nigeria undergo a considerable amount of handling and contacts with microbes of different sources (Umoh, 2002). Unhygienic processing of carcasses is a common practice in Nigeria, resulting in carcass contamination and isolation of microorganisms from meat and slaughtering facilities (Umolu et al, 2006; Ojo et al, 2009). Bacterial organisms such as E. coli increase or decrease during processing depending on the level of faecal contamination of live cattle, efficiency of evisceration and hygienic practices in the abattoir (Rigobelo et al., 2006). Due to the poor environmental conditions of abattoirs and slaughter slabs, there is a very high risk of contamination of these carcasses during preparation (James et al., 2000). By reducing the primal surface contamination and limiting the microbial growth, the shelf-life of beef can be considerably prolonged, as well as, improve food safety (James et al., 2000). The meat retail market is one of the supply chains of the beef industry. It is a critical and very vital point of the supply chain because meat are retailed to consumers at affordable prices. It is the central point where most consumers purchase their meat. In Nigeria, fresh beef forms a significant proportion of meat intake (Olaoye and Onilude, 2010). It is either eaten cooked or processed into other forms to avoid associated spoilage. Means of controlling or even improving the safety of food products is to decontaminate the meat during or at the end of the production line. The decontamination of beef can help to reduce human food-borne infection (Dincer and Baysal, 2004). It can also help to prolong its shelf-life and enhance its keeping quality in situations where refrigeration is poor due to unstable power supply as observed in Nigeria. There is paucity of information on the control of pathogenic organisms associated with fresh beef obtained from retail markets in Zaria as regards decontamination. Hence, investigations are required in order to extend meat shelf-life and promote the health and safety of consumers of fresh beef.
1.4 Aim of the Study
The aim of the study was to determine the influence of lactic acid and trisodium phosphate treatments on the shelf-life of beef obtained from retail markets in Zaria metropolis, Nigeria.
1.5 Objectives of the Study
The specific objectives of the study were to determine the:
- Effect of lactic acid and trisodium phosphate on the microbial quality of beef bought from retail markets in Zaria metropolis.
- Effect of lactic acid and trisodium phosphate on coli contaminated beef sold in retail markets in Zaria.
- Acceptability or otherwise of the treated beef samples using sensory analyses.
1.6 Research Questions
- What is the effect of trisodium phosphate on the microbial load of beef sold in retail markets in Zaria metropolis?
- What is the effect of lactic acid treatment on the microbial load of beef sold in retail markets in Zaria metropolis?
- Are treatments with trisodium phosphate effective against coli contamination on beef sold in the retail markets in Zaria metropolis?
- Are treatments with lactic acid effective against coli contamination on beef sold in the retail markets in Zaria metropolis?
- Do the treatments with trisodium phosphate have effect on the sensory qualities of beef sold in retail markets in Zaria metropolis?
- Do the treatments with lactic acid have effect on the sensory qualities of beef sold in retail markets in Zaria metropolis?
