A RESEARCH NOTE: DETECTION OF ADULTERATION IN PROCESSED TRADITIONAL MEAT PRODUCTS

Nondeclared protein addition is one of the most frequent adulterations used in meat products. Meat substitution with an unspecified specie, usually of less quality, is a fraudulent act in the industry and could have economic and health repercussions. In this study, we used an immunodiffusion assay in agar gel to identify bovine, porcine, equine and avion species in two slightly processed meat products, uncooked commercial hamburger and Mexican sausage (chorizo). Analysis of 40 samples from local food stores was performed. Undeclared equine specie was detected in 9 of the 23 of the hamburger meat samples. In Mexican sausage undeclared equine and porcine specie were also found in 5 of the 17 samples. These results showed violations in practices of the regional meat industry. It is suggested that regulatory agencies institute programs to ensure that meat products are properly labeled to protect consumers.     

DETECTION AND CHARACTERIZATION OF VEROTOXIN-PRODUCING ESCHERICHIA COLI (VTEC) ISOLATED FROM BUFFALO MEAT

The emergence of Verotoxin‐producing Escherichia coli (VTEC) as zoonotic foodborne pathogens in recent years has become a public health concern because of its life threatening human diseases. In the present investigation, out of 87 strains of E. coli, 22 (25%) belonging to 13 different serotypes isolated from raw buffalo meat and its products were found to be verotoxic as tested by Vero cell cytotoxic assay. Serotype O26 followed by O153 and O157 were the predominant VTEC. All the VTEC strains were found positive for vt genes by polymerase chain reaction (PCR). Among the vt genotypes, vt₂(77%) was most predominant followed by vt₁(14%) and both vt₁and vt₂(9%). Production of enterohaemolysin on washed sheep blood agar supplemented with CaCl₂ showed 19 (86%) VTEC strains to be positive. Presence of VTEC in cooked buffalo meat products, namely shami kabab and kabab, appears to be a matter of concern and a potential threat to public health. VTEC detection by different methods suggests that PCR can be useful to evaluate the distribution of virulence genes (vt₁or vt₂or both) in E. coli isolates from buffalo meat and its products.     

A STUDY ON SUITABILITY OF FOUR ENRICHMENT BROTHS FOR PCR-BASED DETECTION OF LISTERIA MONOCYTOGENES FROM RAW MEAT

Four enrichment broths were evaluated for their compatibility with the polymerase chain reaction (PCR) for detection of Listeria monocytogenes from raw meat after single‐step enrichment. Standardized PCR protocols for listeriolysin O (hlyA) gene were used for the species‐specific identification of L. monocytogenes. Four broths, namely, modified University of Vermont broth (MUVM), Listeria enrichment broth (LEB), Fraser broth (FB) and polymyxin, acriflavin, lithium chloride, ceftazidime, aesculin, mannitol, egg yolk broth (PALCAM) , were inoculated with L. monocytogenes. The enriched cultures were subjected for PCR. Similarly, meat samples were artificially spiked with various concentrations of L. monocytogenes, these spiked samples were enriched in the above‐mentioned four broths and subjected to PCR to determine the medium that was most compatible for PCR‐based detection of L. monocytogenes. The aliquots taken during different incubation periods were subjected to three different procedures for the concentration of the target organism for use in PCR. Results revealed that MUVM was better than other broths for the detection of L. monocytogenes by both PCR and cultural method; moreover, it was able to support the growth of as low as 10 cfu/g of meat. Concentration of the target organisms by centrifugation and washing with PCR buffer was the most suitable method for improving PCR performance for detection of L. monocytogenes. Goat (n = 67) and buffalo (n = 45) meat samples from local markets were also screened by both PCR and cultural method to validate the results obtained from the spiking studies. Both results were in agreement in spiking studies as well as screening of market meat samples.     

TEXTURAL CHARACTERISTICS OF FIVE MICROORGANISMS FOR RAPID DETECTION USING IMAGE PROCESSING

A rapid and cost-effective technique for identification and classification of microorganisms was explored using fluorescence microscopy and image analysis. After staining the microorganisms with fluorescent dyes (diamidino-2-phenyl-indole [DAPI] and acridine orange [AO], images of the microorganisms were captured using a charge-coupled device camera attached to a light microscope. Textural features were extracted from the images. Fluorescence emission from Bacillus thuringiensis is the highest compared with other microbes, and the emission from Lactobacillus brevis is the lowest. Various microorganisms can be differentiated using various textural features from images using AO or DAPI dye. Many textural features of the images obtained from the two dyes were different.

PRACTICAL APPLICATIONS

Conventional microbial detection methods take considerable time and are laborious. Rapid methods are required so that pathogens and spoilage microorganisms in foods and water can be identified and counted in a much shorter time. This work investigates image processing techniques particularly based on textural properties of the images of microorganisms. Images of microorganisms in samples can be captured using light microscopes after concentrating using centrifuge or membrane separation devices. This work will assist in developing a commercial method for rapid detection of microbes in food samples.     

RAPID METHOD FOR DETECTION OF SALMONELLAE ATTACHED TO CHICKEN SKIN1

A rapid, sensitive nitrocellulose membrane lifting technique was developed to identify Salmonella typhimurium attached to chicken skin. Basically, this method used a nitrocellulose membrane to remove salmonellae attached to chicken skin. The membrane with attached salmonellae was then incubated on xylose lysine deoxycholate (XLD) agar for 18 h at 37°C. Appearance of black colonies on the white membrane was considered a positive presumptive test for salmonellae. Immunostaining of colonies on the nitrocellulose membrane was then used to confirm presence or absence of salmonellae. This technique can be used to identify salmonellae contamination of chicken skin in less than 24 h and was shown to be more sensitive than presently used swabbing or washing techniques.     

A SIMPLE,RAPID METHOD FOR THE DETECTION OF SUBSPECIES OF ZYMOMONAS MOBILIS

Zymomonas strains are simply and rapidly detected after growth in a selective liquid medium by the addition of a Schiff's reagent. This dye reacts with acetaldehyde produced by Zymomonas to give a deep purple colour. The optimal conditions for the test are evaluated and it is shown to be specific for Zymomonas strains. The use of the dye reaction in routine microbiological quality control is described. A comparison is presented of the dye test and the use of an agar medium containing sulphite and lead acetate on which Zymomonas strains which produce H₂S form characteristic colonies.     

PROCESS OPTIMIZATION FOR CHICKEN PATTIES MANUFACTURED WITH A COMBINATION OF SPENT HEN AND RABBIT MEAT

ABSTRACT

A comminuted chicken patty was produced using spent hen and rabbit meats at 100:0, 95:5, 90:10, 85:15 and 80:20 ratios. The extenders/binders with whole liquid eggs (WLE) at 5, 10 and 15% and soy chunks at 3, 6 and 9%, respectively, were also used. The patties were evaluated for sensory, physicochemical and proximate quality and shelf life. The scores for all sensory attributes of patties stored at refrigerated temperature (4 ± 1C) for 20 days decreased significantly (P < 0.05) while pH, thiobarbituric acid and tyrosine values increased significantly (P < 0.05). The patties formulated with WLE and soy chunks‐added patties were acceptable up to 20 days without any spoilage. A combination of 90:10 spent hen meat and rabbit meat formulated with either 10% WLE or 9% soy chunks resulted in the most desirable patties that scored maximum for sensory attributes and had better cooking yield, emulsion stability and physicochemical characteristics over all other combinations.

PRACTICAL APPLICATIONS

Meat from spent hens is usually tough and poor in functional properties but could be beneficially utilized through formulation of comminuted processed products. The process of comminution is proven to convert relatively tough and less juicy meat into processed meat products with desirable characteristics. Rabbit meat is rich in vitamin B complex, low in fat and cholesterol content and easily digestible. The protein value of domestic rabbit meat ranked superior over meat of other species being used for human consumption. Egg is a well‐known food additive and emulsifier that possesses nutritional, functional and emulsion properties. The functional properties of egg improve the physicochemical and sensory qualities of patties. In addition, the antimicrobial and antioxidative properties of egg components have been effectively utilized in formulation of meat products.     

RAPID METHODS FOR THE DETECTION OF YEAST AND LACTOBACILLUS BY ATP BIOLUMINESCENCE

Present plating methods for the detection of potential spoilage organisms in packaged beers require 2–3 days for yeast, and 5–7 days for lactic acid bacteria. Simple and inexpensive sterility tests based on bioluminescence have been developed for the detection in broth media of small numbers of yeasts in 1 day, and lactic acid bacteria, in both normal and heat-stressed conditions, in 3 days.