The use of bacterial alkaline phosphatase assay for rapid monitoring of bacterial counts on spinach

ABSTRACT:  This study was undertaken to evaluate the applicability of bacterial alkaline phosphatase (ALP) activity for rapid monitoring of total mesophilic bacteria counts in spinach. A set of fresh and decayed spinach mixtures were tested to rapidly (10 min) monitor spinach bacterial counts. To assay ALP activity, Lumigen APS-5 was used as a substrate. Bovine ALP was reduced after heat treatment at 75 °C for 1 min; in contrast, bacterial ALP activity increased. To differentiate bacterial ALP from other ALP, heat treatment (75 °C, 1 min) was applied before measurement. As a result, a regression equation was established between the actual mesophilic aerobic bacteria count and ALP activity of spinach mixtures ( r = 0.90). The predicted total mesophilic aerobic bacterial count calculated from the fitted regression line (predicted log₁₀ CFU/g = 0.00056 × ALP values + 1.4002) showed a high correlation with the actual observed total bacterial count ( r = 0.93). The ALP assay is a simple and rapid method to utilize for estimation of existing or contaminating microorganism levels on spinach.     

Rapid and simple estimation of microbiological quality of raw milk using chromogenic Limulus amoebocyte lysate endpoint assay

A rapid chromogenic Limulus amoebocyte lysate (LAL) endpoint assay for the enumeration of total mesophilic microbial loads and coliforms was investigated as a means to assess the microbiological quality of raw milk. For experiment 1, raw milk samples (n = 25) were stored in a refrigerator (2 +/- 2 degrees C) and then analyzed at regular intervals (1, 5, 10, and 15 days). For experiment 2, fresh raw milk samples (n = 50) were tested to determine the utility of the LAL assay for fresh raw milk. The sample was diluted threefold in a 96-well microtiter plate with pyrogen-free water and assayed with a chromogenic LAL kit to find a final reaction point. The LAL results were compared with standard plate counts (SPC) and coliform counts determined by conventional plating methods. The results of the LAL assay were strongly correlated to conventional SPC (r2 = 0.93; n = 100) and were highly correlated to coliforms (r2 = 0.74; n = 100). A highly significant linear relationship (r2 = 0.82; n = 50) was also observed between the predicted SPC based on the LAL value and the actual SPC. The results of LAL testing were classified into one of seven contamination groups. The data set for SPC was effectively differentiated using the LAL technique (P < 0.01). The chromogenic LAL assay was found to be a rapid (within 16 min) and simple (not requiring specific instruments) method for monitoring microbial levels in raw milk. This method may be successfully implemented to rapidly determine highly microbial contaminated raw milk (> 3.0 log10 CFU/ml of SPC).     

Comparison of a rapid ATP bioluminescence assay and standard plate count methods for assessing microbial contamination of consumers' refrigerators

The feasibility of using an ATP bioluminescence assay for assessing microbial contamination of home refrigerators was evaluated and compared with the standard culture methods. Samples of refrigerator surfaces were collected from 123 households by swabbing an area of 100 cm2 on three locations in the refrigerator with premoisturized sterile swabs. Microbial contaminations were determined by aerobic plate count (APC; incubated at 35 degrees C for 48 h) and psychrotrophic plate count (PPC; incubated at 7 degrees C for 10 days) on plate count agar. The results were compared to the readings from the microbial ATP (mATP) bioluminescence assay. The correlation coefficient (r) between mATP and PPC (r = 0.851) was slightly higher than that between mATP and APC (r = 0.823). Our results indicated a potential discrepancy in the population of mesophilic and psychrotrophic bacteria in the refrigerator samples. Nevertheless, mATP appeared to be a reliable indication of the average of APC and PPC (r = 0.895). The mATP bioluminescence assay would provide a rapid and convenient test for researchers in field studies to assess microbial contamination in refrigerators.     

Distribution of airborne microorganisms in commercial pork slaughter processes

The objective of this research was to determine the prevalence and distribution of airborne bacterial contamination, with particular reference to Escherichia coli and Salmonella, at a number of stages in a pork slaughtering plant. Air samples (impaction and sedimentation) were recovered from seven locations before and during operations in a commercial pork processing plant. Aerobic mesophilic bacteria, E. coli counts and the incidence of Salmonella in the air were determined. Most sample locations which provided high impaction counts also provided high sedimentation counts. Before commencement of operations, there were no significant differences in aerobic mesophilic bacteria obtained from the sample locations. However, within 2 h of the commencement of operations, aerobic mesophilic bacteria in the wet room (3.14 log10 cfu/m3) were significantly higher (P < 0.05) than those in the clean room (2.66 log10 cfu/m3) and chiller (2.34 log10 cfu/m3). By the afternoon, similar aerobic mesophilic bacteria counts were recovered in the wet and clean rooms, although counts in both of these areas were significantly higher (P > 0.05) than in the chiller. In general there were no significant differences in E. coli counts between rooms (wet room, clean room and chiller) and these did not increase during the production day. Salmonella were detected at the locations of the dehairing and evisceration operations. Aerobic mesophilic bacteria in the air within the abattoir increased as production proceeded. In addition the air within the abattoir contained organisms such as Salmonella and E. coli. Positive correlations (P < 0.05-P < 0.001) between impaction and sedimentation samples were found suggesting that air may be an important source of carcass contamination.     

ATP bioluminescence assay for estimation of microbial populations of fresh-cut melon

Estimation of microbial numbers in foods by conventional microbiological techniques takes days, so there is a need for faster methods that can give results in minutes. Research was undertaken to investigate the use of bioluminescent ATP determination and a firefly luciferase assay to estimate the initial population of aerobic mesophilic bacteria on fresh-cut melons immediately after preparation and during storage at 5 or 15 degrees C for up to 12 days. Populations of aerobic mesophilic bacteria on fresh-cut cantaloupe prepared immediately from unsanitized whole melons averaged 3.42 log CFU/g, corresponding to an ATP value of 5.40 log fg/g. Populations for fresh-cut honeydew prepared from unsanitized whole melon averaged 1.97 log CFU/g, corresponding an ATP value of 3.94 log fg/g. Fresh-cut pieces prepared from cantaloupe or honeydew melons sanitized with either chlorine (200 ppm free chlorine) or hydrogen peroxide (2.5%) had similar ATP values: 3.1 log fg/g (corresponding to bacterial counts 1.7 log CFU/g) for cantaloupes and 2.6 log fg/g (corresponding to bacterial counts of 0.48 CFU/g) for fresh-cut honeydew. Positive linear correlations for ATP concentrations and microbial populations were found for fresh-cut cantaloupe (R2 = 0.99) and honeydew R2 = 0.95) during storage at 5 degrees C for up to 12 days. ATP values in fresh-cut melons inoculated with either aerobic mesophilic bacteria or yeast and mold were significantly higher (P < 0.05) than control values and parallel total plate counts on plate count agar. Results of this study indicate that the bioluminescent ATP assay can be used to monitor total microbial populations on fresh-cut melon after preparation and during storage for quality control purposes to establish specific sell-by or consume-by dates.     

Using indicator bacteria and Salmonella test results from three large-scale beef abattoirs over an 18-month period to evaluate intervention system efficacy and plan carcass testing for Salmonella

To develop a process for predicting the likelihood of Salmonella contamination on beef carcasses, we evaluated the influence of several possible causative factors (i.e., year, abattoir, day of week, month, and intervention system components) on the risk of Salmonella and indicator organism contamination. Hide and carcass sponge samples were collected in 2005 to 2006 in six steps at three abattoirs in the East (A), Midwest (B), and Southwest (C) United States. Each abattoir used the same intervention system. Samples were analyzed for aerobic plate counts (APCs; n = 18,990) and Enterobacteriaceae counts (EBCs; n = 18,989) and the presence or absence of Salmonella (n = 5,355). Our results demonstrated that many factors play a significant role in the level of microbial contamination of beef carcasses. Overall, Salmonella prevalence and EBC levels were significantly higher in 2006 than in 2005. APCs and EBCs were highest in abattoirs A (3.57 log CFU/100 cm2) and B (1.31 log CFU/100 cm2). The odds of detecting a positive Salmonella isolate were greatest in abattoir C and lowest in abattoir A. Across the three abattoirs, the overall intervention process effectively reduced microbiological contamination. Salmonella prevalence fell from 45% (preevisceration) to 0.47% (postchilled-lactic acid), and there were APC and EBC reductions of 5.43 and 5.28 log CFU/100 cm2, respectively, from hide-on to postchilled-lactic acid samples. At each abattoir, composites of three individual EBC-negative carcass samples yielded Salmonella-negative results 97 to 99% of the time. These results suggest the possibility of using indicator test results to accurately predict the absence of Salmonella in a beef carcass sample.     

MICROBIOLOGICAL CONDITIONS OF SHEEP CARCASSES DURING THE SLAUGHTERING PROCESS

This study was undertaken to determine the microbiological quality of sheep carcasses during different stages in the slaughtering process. A total of eleven carcasses were selected at random in an abattoir. The samples were taken by excision from four different sites; leg, brisket, shoulder and neck. The samples were collected from the same carcasses at four different stages in the slaughtering process; after dressing, after evisceration, after washing and chilling. The aerobic mesophilic bacteria, coliforms and Enterobacteriaceae recovered from each sample were enumerated. Chilling reduced the aerobic mesophilic and coliform counts of carcasses, significantly. Levels of carcass microbial load after chilling were 1.69, 0.11 and 0.11 log cfu/cm² for aerobic mesophilic counts, coliform counts and Enterobacteriaceae counts, respectively. According to data obtained in the present study, chilling of carcasses was the most important step in improving the hygienic quality of carcasses. Processing stages changed significantly both aerobic mesophilic and coliform counts of neck, therefore, among different sites of carcass, neck should be the only critical site for microbiological sampling for sheep carcasses.     

Decontamination of beef carcass surface tissue by steam vacuuming alone and combined with hot water and lactic acid sprays

Hot beef carcass surface regions (outside round, brisket, and clod) contaminated with feces spread over a 5-cm2 (1-in2) area were cleaned using a steam-vacuum spot-cleaning system alone or combined with subsequent sanitizing treatments of hot water (95 degrees C at the nozzle), or warm (55 degrees C) 2% lactic acid spray, or combinations of these two sanitizing methods. These treatments were compared for effectiveness in reducing aerobic plate counts (APC) and counts of Enterobacteriaceae, total coliforms, thermotolerant coliforms, and Escherichia coli. All treatments significantly reduced the numbers of each group of bacteria on beef carcass surfaces. However, reductions obtained by steam vacuuming were significantly smaller than those obtained by a combination of steam vacuuming with any sanitizing treatment. No differences in bacterial reductions were observed between different carcass surface regions. Steam vacuuming reduced the number of different indicator organisms tested by ca. 3.0 log cycles but also spread the bacterial contamination to areas of the carcass surface adjacent to the contaminated sites. This relocated contamination after steam vacuuming was most effectively reduced by spraying with hot water and then lactic acid. This combined treatment consistently reduced the numbers of Enterobacteriaceae, total and thermotolerant coliforms, and E. coli to undetectable levels (<1.0 log10 CFU/cm2) on areas outside the initial 5-cm2 inoculated areas.     

Catalase Activity for Rapid Assessment of High Level Total Mesophilic Microbial Load in Milk

ABSTRACT: Total mesophilic microbial load (APC) is an important index for milk quality. It takes 48 h to enumerate APC with conventional plating methods. This report presents a rapid catalase activity test for monitoring APC in milk. Most aerobic microorganisms have strong catalase activities. Catalase activity in milk was monitored with a Pasteur pipette method in 5 min. The correlation between high APC numbers (> 4.0 log CFU/ml) and catalase activities was strongly correlated with r²=0.89. Classifying the APC into eight contamination groups was found to be a sound means of utilizing the resultant catalase activities to predict APC.     

A rapid molecular-based assay for direct quantification of viable bacteria in slaughterhouses

A rapid test for microbial quantification in carcass and environmental swabs that does not require enrichment and provides results in less than 4 h is described here. Steps in the assay include the rapid concentration of bacteria on sponge swabs by vacuum filtration followed by real-time PCR detection. The assay has been applied for the detection of coliforms, Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes on carcass swabs and environmental samples in a slaughterhouse-processing line. Comparison of this rapid method with standard culture techniques for coliform counts on beef and pork carcass swabs revealed higher numbers of bacteria (2- to 50-fold) by the rapid test compared with the plate counts. This was due to the detection of all bacteria (live, dead, and non-culturable forms) in the rapid assay. To allow detection of only viable bacteria, concentrated samples were treated with ethidium monoazide (EMA) prior to DNA extraction and real-time PCR detection, thereby preventing the amplification of DNA from bacteria with damaged cell walls and allowing only the DNA from bacteria with intact membranes to be detected. EMA treatment resulted in a significant reduction (P < 0.001) in the number of coliforms detected compared to real-time PCR without EMA treatment. In beef swabs, the counts obtained in EMA real-time PCR were not significantly different (P < 0.08) from the culture counts and the correlation coefficient between the two assays was 0.7385. A lower correlation coefficient (0.402) was obtained with pork swabs. The assay described herein has the potential to be applied on a routine basis to slaughterhouse lines for the detection of indicator organisms or specific pathogens.     

Microbiological status of fresh beef cuts

Fresh beef samples (n = 1,022) obtained from two processing plants in the Midwest (July to December 2003) were analyzed for levels of microbial populations (total aerobic plate count, total coliform count, and Escherichia coli count) and for the presence or absence of E. coli O157:H7 and Salmonella. A fresh beef cut sample was a 360-g composite of 6-g portions excised from the surface of 60 individual representative cuts in a production lot. Samples of fresh beef cuts yielded levels of 4.0 to 6.2, 1.1 to 1.8, and 0.8 to 1.0 log CFU/g for total aerobic plate count, total coliform count, and E. coli count, respectively. There did not appear to be substantial differences or obvious trends in bacterial populations on different cuts. These data may be useful in establishing a baseline or a benchmark of microbiological levels of contamination of beef cuts. Mean incidence rates of E. coli O157:H7 and Salmonella on raw beef cuts were 0.3 and 2.2%, respectively. Of the 1,022 samples analyzed, cuts testing positive for E. coli O157:H7 included top sirloin butt (0.9%) and butt, ball tip (2.1%) and for Salmonella included short loins (3.4%), strip loins (9.6%), rib eye roll (0.8%), shoulder clod (3.4%), and clod, top blade (1.8%). These data provide evidence of noticeable incidence of pathogens on whole muscle beef and raise the importance of such contamination on product that may be mechanically tenderized. Levels of total aerobic plate count, total coliform count, and E. coli count did not (P > or = 0.05) appear to be associated with the presence of E. coli O157:H7 and Salmonella on fresh beef cuts. E. O157:H7 was exclusively isolated from cuts derived from the sirloin area of the carcass. Salmonella was exclusively isolated from cuts derived from the chuck, rib, and loin areas of the carcass. Results of this study suggest that contamination of beef cuts may be influenced by the region of the carcass from which they are derived.     

肉牛屠宰过程中胴体表面及接触环境污染情况分析

为研究肉牛屠宰场屠宰过程中牛胴体表面污染及接触环境污染变化情况,选取某牛屠宰场采集样品共计322 份,分别在剥皮扯皮、去内脏、修整称质量、冲洗及排酸环节对牛胴体后腿、背部、胸部、前腿及颈部以及屠宰前后的工人手部及刀具进行采样,测定菌落总数、乳酸菌、大肠菌群、金黄色葡萄球菌及假单胞菌的污染情况。结果表明：胴体表面污染情况总体呈现先上升后下降的趋势,修整称质量环节污染最为严重,菌落总数可达到2.82（lg（CFU/cm2））;胸部为屠宰过程中污染最严重的部位,平均菌落总数可达到2.10（lg（CFU/cm2））;屠宰空气在冲洗时污染最为严重,空气沉降菌落总数高达271.33 CFU/皿;屠宰工人的手部及刀具也是胴体污染的主要来源。     

Microbiological quality of fresh, minimally-processed fruit and vegetables, and sprouts from retail establishments

A survey of fresh and minimally-processed fruit and vegetables, and sprouts was conducted in several retail establishments in the Lleida area (Catalonia, Spain) during 2005-2006 to determine whether microbial contamination, and in particular potentially pathogenic bacteria, was present under these commodities. A total of 300 samples--including 21 ready-to-eat fruits, 28 whole fresh vegetables, 15 sprout samples and 237 ready-to-eat salads containing from one to six vegetables--were purchased from 4 supermarkets. They were tested for mesophilic and psychrotrophic aerobic counts, yeasts and moulds, lactic acid bacteria, Enterobacteriaceae, presumptive E. coli and Listeria monocytogenes counts as well as for the presence of Salmonella, E. coli O157:H7, Yersinia enterocolitica and thermotolerant Campylobacter. Results for the fresh-cut vegetables that we analyzed showed that, in general, the highest microorganism counts were associated with grated carrot, arugula and spinach (7.8, 7.5 and 7.4 log cfu g(-1) of aerobic mesophilic microorganisms; 6.1, 5.8 and 5.2 log cfu g(-1) of yeast and moulds; 5.9, 4.0 and 5.1 log cfu g(-1) lactic acid bacteria and 6.2, 5.3 and 6.0 log cfu g(-1) of Enterobacteriaceae). The lowest counts were generally associated with fresh-cut endive and lettuce (6.2 and 6.3 log cfu g(-1) of aerobic mesophilic microorganisms; 4.4 and 4.6 log cfu g(-1) of yeast and moulds; 2.7 and 3.8 log cfu g(-1) lactic acid bacteria and 4.8 and 4.4 log cfu g(-1) of Enterobacteriaceae). Counts of psychrotrophic microorganisms were as high as those of mesophilic microorganisms. Microbiological counts for fresh-cut fruit were very low. Sprouts were highly contaminated with mesophilic (7.9 log cfu g(-1)), psychrotrophic microorganisms (7.3 log cfu g(-1)) and Enterobacteriaceae (7.2 log cfu g(-1)) and showed a high incidence of E. coli (40% of samples). Of the samples analyzed, four (1.3%) were Salmonella positive and two (0.7%) harboured L. monocytogenes. None of the samples was positive for E. coli O157:H7, pathogenic Y. enterocolitica or thermotolerant Campylobacter.     

Effects of Soaking with Natural Additives in Combinations with Vacuum or Modified Atmosphere Packaging on Microbial Populations and Shelf Life of Fresh Truffles (Chinese Tuber Indicum)

The objective of this study was to evaluate the relative effects and interactions of combined soaking treatment using citric acid (CTA) and apple polyphenol (APP) at mild heating temperatures for the inactivation of the external and internal microflora (mesophilic aerobic bacteria, mesophilic anaerobic bacteria, and fungi) in Chinese Tuber indicum, as well as to analyze the microbiological and sensory changes under modified atmosphere packaging (MAP)‐ and vacuum atmosphere packaging (VAC)‐packed Chinese T. indicum stored at 4 °C for up to 55 d. Chinese T. indicum was soaked with CTA and APP alone or in combination for 10, 20, and 30 min at 35, 45, and 55 °C. A disinfection method using CTA and APP (3% CTA + 3% APP for 20 min at 45 °C) was obtained. Under this set of combination, the experimental values of microbial counts of mesophilic aerobic bacteria, mesophilic anaerobic bacteria, and fungi were 2.31 ± 0.4 log CFU/g, <1.0 log CFU/g, and <1.0 log CFU/g, respectively. Through the analysis of sensory qualities and microbial populations for MAP‐ or VAC‐packed Chinese T. indicum, the shelf life of soaked truffles was prolonged to 45 or 40 d, respectively. The synergistic effect of CTA and APP may provide valuable insight into the reduction of microorganisms on fresh truffles.     

Microbial shelf life determination of vacuum-packaged fresh beef treated with polylactic acid, lactic acid, and nisin solutions.

The effectiveness of polylactic acid, lactic acid, nisin, and combinations of the acids and nisin on extending the shelf-life of raw beef was determined. Fresh beef pieces (5 by 5 by 2.5 cm) were dipped in a solution of 2% low molecular weight polylactic acid (LMW-PLA), 2% lactic acid (LA), 200 IU of nisin per ml, or the combinations of nisin in either 2% LMW-PLA or 2% LA. The samples were then drip-dried, vacuum-packaged, and stored at 4 degrees C for up to 56 days. The beef surface pH values and numbers of psychrotrophic aerobic bacteria, psychrotrophic and mesophilic Enterobacteriaceae, Pseudomonas, and Lactobacillus were determined weekly for 56 days. The average surface pH values of the beef samples treated with 2% LMW-PLA or the combination of 200 IU of nisin per ml and 2% LMW-PLA were significantly reduced to 5.19 and 5.17, respectively, at day 0 (P < or = 0.05), while those decontaminated with 2% LA or 200 IU of nisin per ml in 2% LA solution were significantly decreased from 5.62 to 4.98 and 4.96, respectively. The 2% LMW-PLA, 2% LA, or the combinations of each acid and nisin showed immediate inhibitory effects on psychrotrophic aerobic bacteria (1.94, 2.36, 2.59, and 1.76 log reduction, respectively), psychrotrophic Enterobacteriaceae (1.37, 1.86, 1.77, and 1.35 log reduction, respectively), mesophilic Enterobacteriaceae (1.00, 1.00, 0.82, and 0.68 log reduction, respectively), and Pseudomonas (1.77, 1.57, 1.76, and 1.41 log reduction, respectively) on fresh beef (P < or = 0.05). The reduction was evident up to 56 days as seen by the numbers of Enterobacteriaceae and Pseudomonas (P < or = 0.05). Because there was no interaction between treatments and storage times, the data in each period were combined and presented as effect of treatments on overall microbial counts of fresh beef. It was found that 2% LMW-PLA, 2% LA, and the combinations of each acid and nisin significantly lowered the population of the above organisms compared with the untreated control, water, or nisin alone (P < or = 0.05).     

Salmonella prevalence and total microbial and spore populations in spices imported to Japan

A total of 259 samples of 40 types of spices were tested for Salmonella prevalence and total microbial and spore populations. Salmonella enterica serotypes Weltevreden and Senftenberg were isolated from a black- and red-pepper sample, respectively. Because Salmonella was not detected by the most-probable-number method, it indicated that at least one cell of the microorganism was present in 25 g of sample. The mean aerobic bacterial count was greater than 5.39 log CFU/g in turmeric, garam masala, curry powder, and paprika. The mean bacterial spore counts were greater than 4.33 log CFU/g in turmeric and curry powder. The mean aerobic bacterial count in the two Salmonella-isolated samples was 6.93 log CFU/g. These results indicate that spices can be a source of contamination in the products where they are used as ingredients, and methods to reduce the microbial load in spices should be used.     

Reduction of the spoilage-related microflora in absorbent pads by silver nanotechnology during modified atmosphere packaging of beef meat

Silver-based antibacterial hybrid materials have been developed by in situ reduction of silver nitrate (1%) adsorbed on cellulose fibers by thermal and UV treatments. Microscopy revealed that the silver nanoparticles were dispersed and regular in shape. Migrated silver ions achieved 60 ppm in beef meat exudates. The ability of the silver-loaded absorbent pads to lower microbial contamination of exuded fluids was studied during storage of beef meat in modified atmosphere packaging. Cellulose-silver hybrid materials reduced the levels of the major microbial groups (total aerobic bacteria, lactic acid bacteria, Pseudomonas spp., and Enterobacteriaceae) present in the absorbent pads by an average of 1 log CFU/g during the entire storage period. The levels of total aerobic bacteria and Pseudomonas spp. were significantly reduced in the presence of silver ions, whereas lactic acid bacteria were less sensitive and not significantly affected. Enterobacteriaceae levels remained under the detection limit when silver was present. Neither the color of the meat nor the microbial loads were markedly affected by the presence of the silver-based antimicrobial hybrid materials.     

Direct quantification and distribution of tetracycline-resistant genes in meat samples by real-time polymerase chain reaction

The evolution of antimicrobial-resistant bacteria has become a threat to food safety and methods to control them are necessary. Counts of tetracycline-resistant (TR) bacteria by microbiological methods were compared with those obtained by quantitative PCR (qPCR) in 80 meat samples. TR Enterobacteriaceae counts were similar between the count plate method and qPCR (P= 0.24), whereas TR aerobic mesophilic bacteria counts were significantly higher by the microbiological method (P < 0.001). The distribution of tetA and tetB genes was investigated in different types of meat. tetA was detected in chicken meat (40%), turkey meat (100%), pork (20%), and beef (40%) samples, whereas tetB was detected in chicken meat (45%), turkey meat (70%), pork (30%), and beef (35%) samples. The presence of tetracycline residues was also investigated by a receptor assay. This study offers an alternative and rapid method for monitoring the presence of TR bacteria in meat and furthers the understanding of the distribution of tetA and tetB genes.     

AQUEOUS GARLIC EXTRACT AND MICROBIOLOGICAL QUALITY OF REFRIGERATED POULTRY MEAT

The antibacterial effect of garlic extract (5, 10 and 15%) was investigated on poultry carcasses obtained from a slaughterhouse, stored under refrigeration, and evaluated at selected time intervals. The effect of the garlic extract on the microbial contaminants of the poultry carcass surface – Salmonella, strict and facultative aerobic, mesophilic, and total and fecal coliforms – was evaluated. The garlic extract exhibited a concentration‐dependent reduction of microbial contamination. Garlic extract concentrations of 10 and 15% were the most effective. The bacteriostatic action of garlic extract against mesophilic microbiota can be observed until the third storage day. The count of total and fecal coliforms remained low during the storage period. Chicken feed was the apparent source of Salmonella contamination, and the aqueous garlic extract was not effective against Salmonella.     

Combined effect of natural essential oils, modified atmosphere packaging, and gamma radiation on the microbial growth on ground beef

Selected Chinese cinnamon, Spanish oregano, and mustard essential oils (EOs) were used in combination with irradiation to evaluate their ability to eliminate pathogenic bacteria and extend the shelf life of medium-fat-content ground beef (23% fat). Shelf life was defined as the time when the total bacterial count reached 10(7) CFU/g. The shelf life of ground beef was determined for 28 days at 4 degrees C after treatment with EOs. The concentrations of EOs were predetermined such that sensory properties of cooked meat were maintained: 0.025% Spanish oregano, 0.025% Chinese cinnamon, and 0.075% mustard. Ground beef samples containing EOs were then packaged under air or a modified atmosphere and irradiated at 1.5 kGy. Ground beef samples (10 g) were taken during the storage period for enumeration of total mesophilic aerobic bacteria, Escherichia coli, Salmonella, total coliforms, lactic acid bacteria, and Pseudomonas. Mustard EO was the most efficient for reducing the total mesophilic aerobic bacteria and eliminating pathogenic bacteria. Irradiation alone completely inhibited the growth of total mesophilic aerobic and pathogenic bacteria. The combination of irradiation and EOs was better for reducing lactic acid bacteria (mustard and cinnamon EOs) and Pseudomonas (oregano and mustard EOs). The best combined treatment for extending the shelf life of ground beef for up to 28 days was EO plus irradiation (1.5 kGy) and modified atmosphere packaging.