Aerobic Mesophilic Plate Count Research Articles

Modeling the growth of Salmonella in raw ground pork under dynamic conditions of temperature abuse

Salmonella contamination of pork products is a significant public health concern. Temperature abuse scenarios, such as inadequate refrigeration or prolonged exposure to room temperature, can enhance Salmonella proliferation. This study aimed to develop and validate models for Salmonella growth considering competition with background microbiota in raw ground pork, under isothermal and dynamic conditions of temperature abuse between 10 and 40 °C. The maximum specific growth rate (μmax) and maximum population density (MPD) were estimated to quantitatively describe the growth behavior of Salmonella. To reflect more realistic microbial interactions in Salmonella-contaminated product, our model considered competition with the background microbiota, measured as mesophilic aerobic plate counts (APC). Notably, the μmax of Salmonella in low-fat samples (∼5 %) was significantly higher (p < 0.05) than that in high-fat samples (∼25 %) at 10, 20, and 30 °C. The average doubling time of Salmonella was 26, 4, 2, 1.5, 0.8, and 1.1 h at 10, 15, 20, 25, 30, and 40 °C, respectively. The initial concentration of Salmonella minimally impacted its growth in ground pork at any temperature. The MPD of APC consistently exceeded that of Salmonella, indicating the growth of APC without competition from Salmonella. The competition model exhibited excellent fit with the experimental data, as 95 % (627/660) of residual errors fell within the desired acceptable prediction zone (pAPZ >0.70). The theoretical minimum and optimum growth temperatures for Salmonella ranged from 5 to 6 °C and 35 to 36 °C, respectively. The dynamic model displayed strong predictive performance, with 90 % (57/63) of residual errors falling within the APZ. Dynamic models could be valuable tools for validating and refining simpler static or isothermal models, ultimately improving their predictive capabilities to enhance food safety.

Antimicrobial efficacy of a citric acid/hydrochloric acid blend, peroxyacetic acid, and sulfuric acid against Salmonella and background microbiota on chicken hearts and livers.

This study aimed at evaluating the efficacy of a blend of citric acid and hydrochloric acid (CP), peroxyacetic acid (PAA), and sulfuric acid (SA) against Salmonella and mesophilic aerobic plate counts (APC) on chicken hearts and livers. Samples were inoculated with a five-serovar cocktail of Salmonella at ca. 4.8logCFU/g and treated by immersion with a water control (90s), CP (5% v/v, 30s), PAA (0.05% v/v or 500ppm, 90s), or SA (2% v/v, 30s), all at 4°C and with mechanical agitation. Samples were vacuum packed and stored for up to 3 days at 4°C. Three independent replications were performed for each product, treatment, and time combination. The average Salmonella reductions in chicken hearts after 3 days were 1.33±0.25, 1.40±0.04, and 1.32±0.12logCFU/g for PAA, SA, and CP, respectively. For chicken livers, the values were 1.10±0.12, 1.09±0.19, and 0.96±0.27 for PAA, SA, and CP, respectively. All antimicrobials reduced Salmonella counts in both chicken hearts and livers by more than one log, in contrast to the water control. All treatments effectively minimized the growth of APC for up to 3 days of refrigerated storage, and no differences in objective color values (L, a, or b) were observed. The poultry industry may use these antimicrobials as components of a multifaceted approach to mitigate Salmonella in nonconventional chicken parts.

Microbial food safety of lettuce produced under irrigated wastewater from Onyasia River in Ghana

Fresh produce continues to be the main source of foodborne illness outbreaks, particularly in developing countries where water stress results in the use of surface wastewater all year round for irrigation of vegetables. The objective of the current study was to evaluate the microbial quality of lettuce irrigated with wastewater from Onyasia river. Lettuce and soil were sampled from selected vegetable farms on the Eastern gate of the Ghana Atomic Energy Commission land alongside surface wastewater from the Onyasia river, which is used as the main source for irrigation. Samples were analyzed for aerobic mesophilic plate counts, total coliforms count, fecal coliforms count, Salmonella counts and intestinal parasites using standard methods. Surface wastewater was found to be contaminated with mean fecal coliform counts of log 3.50 cfu/100 mL. Enterobacter cloacae, Acinetobacter baumannii, and Klebsiella pneumonia were also isolated from the wastewater samples. No intestinal parasite egg was detected in wastewater samples. While fecal coliforms and Salmonella spp were not detected, mean aerobic mesophilic plate counts (log 4.82 cfu/g) and total coliforms count (log 3.50 cfu/g) were recorded in the lettuce samples. Enterobacter asburiae, Acinetobacter baumannii, Klebsiella variicola and Citrobacter freundii were isolated from lettuce. Infective larvae of helminths were observed on lettuce samples at a density of 36/g-648/g with a mean of 342/g. Soil samples recorded a mean aerobic mesophilic plate counts of log 6.14 cfu/g, total coliforms count of log 4.90 cfu/g while fecal coliforms and Salmonella spp were not detected (<1 cfu/g) Soil samples yielded a mean infective larval count of 1941.5 larvae/g and a Strongyle count of 12 eggs/g. Even though less than 1 cfu/g of Salmonella spp were found, the study found lettuce to be contaminated with other foodborne bacteria pathogens, opportunistic bacteria pathogens, eggs and infective larvae of intestinal parasites of health importance. As a consequence, the microbial food safety risk associated with wastewater irrigated vegetables was observed to be high with possible public health implications. It is recommended that wastewater from the Onyasia River should be treated before use for irrigation of lettuce.

RAW COW MILK QUALITY: PHYSICOCHEMICAL, MICROBIOLOGICAL, AND SEASONAL VARIATION

Milk serves as a vital source of essential nutrients in human diets and must be safe for consumption. In the dairy industry, it is crucial to analyze the physicochemical and microbiological properties of raw cow milk (RCM) throughout the year to gather fundamental information, as milk quality significantly influences the final quality of dairy products. This study aimed to investigate the physicochemical and microbiological properties of 60 RCM samples collected from 15 primary milk collection centers in Qazvin, Iran, and assess the impact of seasonal variation on these properties. The study discovered that the RCM samples contained &gt;7 Log10 cfu/mL of Staphylococcus aureus, total coliform count, aerobic mesophilic plate count, and mold and yeast in 15%, 30%, 37%, and 28% of the samples, respectively. The results indicated that aerobic mesophilic plate count, mold and yeast, total coliform count, and Staphylococcus aureus were higher in warmer seasons compared to colder seasons. Furthermore, the study revealed that the average pH, freezing point, solid-not-fat, and protein content were higher in warm seasons, while the average acidity, lactose, and fat content were higher in cold seasons. The physicochemical and microbiological properties of RCM in the Qazvin region were found to be below the acceptable quality value. Although seasonal variation throughout the year affected the microbial and physicochemical quality of RCM, the differences were not statistically significant (p&gt;0.05), except for the solid-not-fat value in winter (p&lt;0.05).

Growth behavior of Shiga toxin-producing Escherichia coli, Salmonella, and generic E. coli in raw pork considering background microbiota at 10, 25, and 40 °C

Recent epidemiological evidence suggests that pork products may be vehicles for the transmission of Shiga toxin-producing Escherichia coli (STEC) to humans. The severe morbidity associated with STEC infections highlights the need for research to understand the growth behavior of these bacteria in pork products. Classical predictive models can estimate pathogen growth in sterile meat. However, competition models considering background microbiota reflect a more realistic scenario for raw meat products. The objective of this study was to estimate the growth kinetics of clinically significant STEC (O157, non-O157, and O91), Salmonella, and generic E. coli in raw ground pork using competition primary growth models at temperature abuse (10 and 25 °C) and sublethal temperature (40 °C). A competition model incorporating the No lag Buchanan model was validated using the acceptable prediction zone (APZ) method where >92 % (1498/1620) of the residual errors fell within the APZ (pAPZ > 0.70). The background microbiota (mesophilic aerobic plate counts, APC) inhibited the growth of STEC and Salmonella indicating a simple one-directional competitive interaction between pathogens and the mesophilic microbiota of ground pork. The maximum specific growth rate (μmax) of all the bacterial groups was not significantly different (p > 0.05) based on fat content (5 vs 25 %) except for generic E. coli at 10 °C. E. coli O157 and non-O157 behaved similarly in terms of μmax and maximum population density (MPD). Salmonella showed a similar (p > 0.05) μmax to E. coli O157 and non-O157 at 10 and 40 °C but a significantly higher rate (p < 0.05) at 25 °C. STEC were more prone to be inhibited by APC than Salmonella at 10 and 25 °C. The μmax of O91 was lower (p < 0.05) than other STEC and Salmonella at 10 and 25 °C but similar (p > 0.05) at 40 °C. Generic E. coli showed a two- to five-times higher (p < 0.05) μmax (0.028 ± 0.011 log10 CFU/h) than other bacterial groups (0.006 ± 0.004 to 0.012 ± 0.003 log10 CFU/h) at 10 °C making it a potential indicator bacteria for process control. Industry and regulators can use competitive models to develop appropriate risk assessment and mitigation strategies to improve the microbiological safety of raw pork products.

High-pressure processing and storage temperature on Listeria monocytogenes, microbial counts and oxidative changes of two traditional dry-cured meat products

The effects of high hydrostatic pressure (HHP) processing (600 MPa, 8 min, 16 °C) and storage temperature (4 °C and 18 °C) on experimentally inoculated Listeria monocytogenes (L. monocytogenes), mesophilic aerobic plate counts (APC) and yeast and mould (YM) populations in Iberian dry-cured “salchichón” (DCS) and dry-cured loin (DCL) during 120 days of storage were studied. Tocopherol contents, fatty acid profile, instrumental colour and lipid and protein oxidation were evaluated. HHP treatment reduced L. monocytogenes population by >3 log10 in both DCS and DCL. HHP and storage temperature affected APC differently in both products, whereas YM were significantly decreased by HHP, mostly at 18 °C. Lipid and protein oxidation were promoted, mainly in DCS, and the colour was affected in a minor extent. Despite these effects on oxidation, these results suggest that HHP treatment at 600 MPa for 8 min in both products allowed to control L. monocytogenes below the microbiological limit established by the food safety regulations.

Effect of high hydrostatic pressure processing and storage temperature on food safety, microbial counts, colour and oxidative changes of a traditional dry-cured sausage

The effect of a high hydrostatic pressure (HHP) processing (600 MPa, 8 min, 16 °C) during 120 days of storage at 4 °C or 18 °C on the Listeria monocytogenes (L. monocytogenes) cells inoculated in slices of Iberian dry-cured “chorizo” was evaluated. Mesophilic aerobic plate count (APC) and yeast and mold (YM) counts, instrumental colour and lipid and protein oxidation were also evaluated. HHP resulted in a reduction of 3.2 log10 CFU/g in L. monocytogenes counts (P < 0.001). Storage at 18 °C resulted in a remarkable decrease, compared with the 4 °C, in the L. monocytogenes counts during the storage. HHP produced a significant reduction in YM and APC counts immediately after treatment and at d 30 of storage. HHP did not affect instrumental color and lipid and protein oxidation in the first 60 days of storage but increased at 120 days. Storage at 18 °C resulted in decreases in CIE L∗ and a∗ (d120) values, and higher lipid (d30 and d60) and protein oxidation (d30-d120). The use of a treatment of 600 MPa, 8 min can be effective to control L. monocytogenes in case of post-process contamination in Iberian dry-cured “chorizo” without compromise traits related to consumer sensory perceptions.

Effects of Pyruvic Acid, Succinic Acid, and Oregano Essential Oil on Salmonella, Natural Microflora, and Quality of Raw Ground Chicken

ObjectivesThe growing stringency of regulations related to pathogens in raw poultry and increasing consumer demand for more natural food ingredients makes it imperative to explore alternative antimicrobial agents. The aim of this study was to assess the anti-Salmonella effect of combinations of succinate or pyruvic acid with oregano essential oil in raw ground chicken. Additionally, their effect on natural microflora and quality of ground chicken over simulated retail display was evaluated.Materials and MethodsNalidixic acid (NA) adapted Salmonella Typhimurium was inoculated on skin-on broiler breast meat pieces. The antimicrobial treatments given to meat were 2 and 3% pyruvic acid (PA) or monosodium succinate (SA) in combination with 0.5% essential oil (EO). Agar at the concentration of 0.05% was added to water used to prepare antimicrobial solutions to disperse the essential oil. Mode of antimicrobial treatment was 30 s dip. The meat was then ground and evaluated for pathogen reduction. Data were analyzed using 1-way ANOVA. Surviving Salmonella were recovered on XLT-4 with 50 ppm NA. Non-inoculated meat was similarly treated with antimicrobial dip and ground. Ground chicken was packaged in foam trays with PVC overwrap, and evaluated for mesophilic aerobic plate count (APC), psychrotrophic count (PC), pH, instrumental color (CIE L*, a*, and b*), and expressible moisture over 8 d of simulated retail display.A factorial design was assigned to the experiment with antimicrobial treatments and display days as the fixed effect factors. Data were analyzed using a mixed general linear model that considered replicates as a random effect in addition to the mentioned fixed effects. All trials were conducted in three replicates.ResultsMaximum reduction obtained in Salmonella counts from ground chicken was 1.52 log CFU/g and 0.98 log CFU/g, resulting from 3% SA + 0.5% EO, and 3% PA + 0.5% EO, respectively. Three percent SA + 0.5% EO treatment resulted in ground chicken with approximately 1.2 log CFU/g lower APC on Day 8 that was significantly lower (P &lt; 0.05) than all other treatments. This treatment also resulted in less pH variation over the entire shelf life duration and lighter color of ground meat on Day 8.ConclusionThese results indicate that combination of monosodium succinate and oregano essential oil provides effective reduction of Salmonella and improved raw quality of ground chicken. This antimicrobial combination can be employed as a clean label ingredient for raw chicken applications.

Microbiological evaluation of pork offal products collected from processing facilities in a major United States pork-producing region

Analysis of 370 offal samples from 15 US pork-processing facilities detected Yersinia enterocolitica-positive (2.4%) and Salmonella-positive (21.8%) samples and mesophilic aerobic plate counts &gt; 107 colony-forming units/g (3.2%). A risk assessment showed intestine (20%), brain (21%), liver and heart (73%), and kidney (87%) sampling batches were acceptable for human consumption.

Microbial Contamination of Organically and Conventionally Produced Fresh Vegetable Salads and Herbs from Retail Markets in Southwest Germany.

A total of 189 samples of fresh products (leafy salads, ready-to-eat mixed salads, and fresh herbs) bought in retail in Southwest Germany were investigated for their microbiological quality and the presence of pathogenic bacteria, including Salmonella spp., Listeria monocytogenes, and presumptive Bacillus cereus. Total aerobic mesophilic plate counts (TAC) ranged from 5.5 to 9.6 log colony-forming units (CFUs) per gram. Enterobacteria and pseudomonads were the predominant microorganisms and were detected in all samples with counts between 5.0 and 9.2 log CFU/g. Strains of Escherichia coli were detected in 9 salad (7.9%) and 25 herb samples (33.3%). Significant differences in bacterial counts were found between conventionally and organically-grown products: in herbs the counts of moulds were significantly higher in organically-grown products, while E. coli was only detected in conventionally-grown products. In conventionally-grown salad samples, yeast counts were significantly higher. Salmonella Enteritidis was only detected in two conventionally- and in one organically-produced salad samples (2.6%). No coagulase-positive staphylococci were detected in fresh salads as well as in herbs. High levels of B. cereus sensu lato (≥3 log CFU/g) were detected in 19 vegetable salads (16.7%) and even in 55 samples of fresh herbs (73.3%). Listeria monocytogenes could not be detected in fresh herbs; however, three L. monocytogenes strains were isolated from two conventionally-produced salad samples and belonged to PCR serogroup IIa. Although our results indicate a high microbial load in fresh salads and herbs in Southwest Germany in 2015, the incidences of human pathogenic bacteria, that is, L. monocytogenes, Salmonella spp., and coagulase-positive staphylococci strains, were low.

Assessment of Microbiological Safety and Quality of Marinades Used To Treat Beef and That Were Collected over a 12-Month Period from Specialty Retailers Near Raleigh, North Carolina

In total, 115 marinade samples (58 fresh marinades and 57 spent marinades) were collected over 12 months from specialty retailers (four individual stores) near Raleigh, NC. These marinades were screened for total mesophilic aerobic plate count (M-APC), total psychrotrophic aerobic plate count (P-APC), and Enterobacteriaceae. These marinades were also screened for the seven regulated serogroups of Shiga toxin-producing Escherichia coli. Stores A and B used immersion to marinade raw beef cuts, whereas stores C-1 and C-2 used vacuum tumbling. In general, marinade temperatures at the stores ranged from 1.8 to 6.6°C, and beef cuts were marinated from a few minutes to up to 3 days. Regardless of the process used to marinade meat, levels of M-APC and P-APC in fresh marinades ranged from 3.4 to 4.7 and 1.4 to 1.8 log CFU/mL, respectively, whereas Enterobacteriaceae were not detected in any fresh marinades, even after enrichment. However, levels of M-APC, P-APC, and Enterobacteriaceae in spent marinades collected from stores C-1 and C-2 (ca. 3.6 to 7.1 log CFU/mL) were significantly higher (P < 0.05) compared with levels of these same types of bacteria enumerated from spent marinades collected at stores A and B (ca. ≤0.7 to 4.9 log CFU/mL). None of the 115 marinade samples tested positive for Shiga toxin-producing E. coli by using a BAX system real-time PCR assay. No significant (P > 0.05) association was observed between microbial levels (i.e., M-APC, P-APC, and Enterobacteriaceae) and the temperature or duration of the marination process. Levels of M-APC, P-APC, and Enterobacteriaceae in spent marinades were significantly affected by the marination method (P < 0.05), with levels, in general, being higher in marinades used for tumbling. Thus, retailers must continue to keep marinade solutions and meat at a safe temperature (i.e., ≤4°C) and to properly and frequently sanitize the equipment and environment in both the processing area and deli case.

Changes on biogenic, volatile amines and microbial quality of the blue swimmer crab (Portunus pelagicus) muscle during storage.

Biogenic amines (BAs) are a group of substances with low molecular weight organic compounds such as aliphatic, aromatic or heterocyclic structures that are naturally present in animal tissues. The aim of this study was to investigate the changes on the formation of biogenic amine, bacterial load and biochemical characteristics in blue swimmer crab (Portunus pelagicus) at different storage temperatures (4 and 20°C) up to 96h. From seven BAs only four biogenic amines (tryptamine, putrescine, histamine, and tyramine) were detected while, the cadaverine, spermidine and spermine were absent in all investigated samples. Histamine was the major biogenic amine formed during the storage times and reached the highest concentration of 7.55±0.46mg/100g and 17.68±1.30mg/100g after 96h at 4 and 20°C, respectively. This level of histamine exceeded the maximum tolerance level of 5mg/100g. However, the proper icing procedure retarded the histamine effects, resulting only 7.55mg/100g after 96h of ice storage. Spoilage indicator putrescine was only detected after 24-96h of storage at 4 and 20°C, respectively. The total volatile base nitrogen and the trimethylamine-nitrogen concentrations were considered to be reliable indicators of freshness index in blue swimmer crab. An aerobic mesophilic plate count of 6.68 and 7.31 log CFU/g were noted for crab stored in ice and ambient temperature after 96h storage, respectively. It could be concluded that the biogenic amine forming bacteria and other susceptible perishing factors responsible for the biogenic amine formation could be prevented by continuous storage of P. pelagicus at low temperature.

Does electrolyzed water have different sanitizing effects than sodium hypochlorite on different vegetable types?

PurposeThe purpose of this paper is to examine the efficacy of microbial elimination using different sanitizers in raw vegetables (cherry tomatoes, spring onions, Chinese chives, and chicory) and to analyze the efficacy of Escherichia coli O157:H7 reduction by type of sanitizer and vegetable.Design/methodology/approachTo assess the sanitizing effects of microbial elimination by variety of vegetable, the samples were grouped into four different washing methods: control (no sanitizer), 100 ppm chlorine, 100 ppm electrolyzed water, and 200 ppm electrolyzed water after prewashing. Subsequently, quantitative microbiological experiments were conducted to assess aerobic mesophilic plate count (APC), coliform, E. coli, and Bacillus cereus, and sensory changes of the sanitized vegetables were tested. Thereafter, measurement of the sanitizing effects on bacterial reduction after inoculation with E. coli O157:H7 was conducted.FindingsThe microbial levels of four types of vegetables ranged from 3.37 to 5.24 log CFU/g for APC, 2.41 to 5.57 log CFU/g for E. coli, 0.25 to 5.40 log CFU/g for coliform, and 0.83 to 5.44 log CFU/g for B. cereus. After three types of sanitizing treatments, microbial reduction effects showed 0.94-1.84 log CFU/g for APC, 0.56-1.00 log CFU/g for E. coli, 0.18-1.26 log CFU/g for coliform, and 0.56-1.23 log CFU/g for B. cereus (p<0.05). In sensory evaluation, there were no significant differences in taste and flavor between with and without sanitizing treatments. Regarding bacterial reduction after inoculation with E. coli O157:H7, the microbial reduction on vegetables was shown to be in the range of 0.27-1.57 log CFU/g with 100 ppm sodium hypochlorite, 0.66-3.07 log CFU/g with 100 ppm electrolyzed water, and 0.79-2.55 log CFU/g with 200 ppm electrolyzed water. Chicory, cherry tomato, and spring onion showed significant reduction levels of E. coli O157:H7 after sanitation (p<0.05).Originality/valueThis study revealed that different sanitization methods are required for different types of vegetables. Electrolyzed water treatment (100 ppm) is a more effective and safe method of washing raw vegetables. Given that the main purpose of sanitizing fresh-cut produce is to maximally reduce microorganism levels, different methods of sanitizing fresh-cut produce with an adequate washing method should be used according to vegetable type.

Chemical and microbiological studies on Kenyan and Gabali Egyptian tea

The present study was designed to compare the quality of Gabali Egyptian tea and Kenyan tea locally cultivated in Egypt. Gabali, black and green Kenyan teas were laboratory processed, then analyzed chemically and microbiologically for their quality evaluation. Representative results show that all samples of the 3 types were contaminated with aerobic mesophilic plate counts of the tea types varied from 6.1x103 to 2.2x108 cfu/g, spore-forming bacteria 1.1x102 to 1.6x104 cfu/g, coliforms (MPN) 0.36- 1.5 x101 cell/g, molds 2.3x102 to 3.0x104 and yeasts 1.2x102 to 5.8x103 cfu/g, in which gabali tea was the highest and black Kenyan tea was the lowest microbial count. Pathogenic bacteria were not in detectable level. The black Kenyan tea had the highest antibacterial activity followed by the green Kenyan tea with all solvents, but extraction of Gabali tea had antibacterial activity only by distilled water and water reflux. Total aflatoxin in concentration range of 6.1, 9.8 and >50 μg/kg in black and green Kenyan tea and Gabali tea, respectively. Phytochemical analysis of the tea samples revealed the presence of tannin in high level in black Kenyan tea (14.33%). Considering the results obtained, only black and green Kenyan tea had acceptable levels for all microbial factors in comparison with the Egyptian standards. It was concluded that Gabali tea may be high risk product and therefore, more studies are necessary to find methods of decontamination.

Microbiological Load and Quality Characteristics of Irradiated Chicken Meat

The present study was conducted to evaluate the combined effect of gamma irradiation and refrigeration on the microbiological, chemical and sensorial characteristics of raw chicken meat. Chicken meat was irradiated at doses of 0, 2, 4 and 6 kGy of gamma irradiation, and kept in a refrigerator (1-4oC). General composition, microbial, chemical and sensory evaluation of chicken meat was done. Results showed that, all used doses of gamma irradiation reduced the total mesophilic aerobic plate counts (TPCs) and total coli forms of chicken meat. Shelf-life extension periods estimated on the basis of a limit of 6 log CFU/g for TPCs were 2, 4, 9, and more than 13 weeks for samples irradiated at 0, 2, 4, and 6 kGy, respectively. Irradiation had little or no effect on general composition (moisture, protein, and fat contents), total acidity, lipid peroxide and total volatile basic nitrogen. Sensory evaluation showed no significant differences between irradiated and non-irradiated chicken meat

Effect of inoculation of lactic acid bacteria on proteolytic activity of psychrotrophic Gram-negative bacteria in fresh farmed sea bass (Dicentrarchus labrax) fillets during storage at 4 °C under vacuum-packed conditions

The effect of two strains of lactic acid bacteria (LAB) (Lactococcus lactis and Carnobacterium piscicola) on the proteolytic activity of four strains of Psychrotrophic Gram-negative bacteria [Psy G(−)] (Pseudomonas fluorescens, Aeromonas hydrophila, Pseudomonas putida and Photobacterium damselae) has been determined using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), in fresh vacuum-packed farmed sea bass (Dicentrarchus labrax) fillets artificially contaminated, during 21 days of chilled storage. The profiles of sarcoplasmic (SP) and myofibrillar (MP) proteins indicated that the major changes were produced with Pseudomonas fluorescens, Aeromonas hydrophila, and Pseudomonas putida starters. The results also showed that LAB strains presented a weak proteolytic activity against MP and SP proteins in muscle of fresh sea bass. In fact, we noted the less pronounced degradation of protein fractions in samples inoculated with LAB combination. Moreover, a significant bacteriostatic effect of LAB strains was demonstrated against all microflora, particularly mesophilic aerobic plate counts (MAPC) and psychrotrophic bacterial counts (PBC), with fillets remaining unspoiled until the end of storage, against values of 7 and 8 log CFU/g, respectively; control fish fillets exceeded the upper acceptability limit.

Effect of steam and lactic acid treatments on the survival of Salmonella Enteritidis and Campylobacter jejuni inoculated on chicken skin

Campylobacteriosis and salmonellosis are the most frequently reported zoonotic infectious diseases. The present work evaluated the effectiveness of steam treatment at 100°C for 8s, a 5% lactic acid treatment for 1min and their combination for inactivating Salmonella Enteritidis and Campylobacter jejuni inoculated on chicken skin. The impact of each treatment on the total aerobic mesophilic bacteria and the effect of rinsing after contact with lactic acid were also evaluated. Residual bacteria were counted immediately after treatment or after seven days of storage at 4°C.Results demonstrated the immediate efficiency of the steam and the combined treatments with reductions of approximately 6 and 5 log cfu/cm2 respectively for S. Enteritidis and C. jejuni. They also showed significant reductions (equal to or >3.2 log cfu/cm2) in the total aerobic mesophilic plate count. Lactic acid had a persistent effect on pathogen growth during storage which was significantly higher when the skin was not rinsed, reaching reductions of 3.8 log cfu/cm2 for both S. Enteritidis and C. jejuni. Only the combined treatments significantly reduced the recovery of the total aerobic mesophilic bacteria during storage.The significant reductions in both pathogens and total aerobic mesophilic bacteria on treated chicken skins are possible ways to improve the safety and shelf life of the product although high levels of indigenous non-pathogenic bacteria may be beneficial due to their protective effect against potential re-contamination of chicken skin.

Quality and Shelf-Life Assessment of Pasteurized Trout Soup During Refrigerated Storage

The aim of this study was to investigate the quality changes of pasteurized soup prepared from smoked trout trimmings during 8 months of refrigerated storage at 3°C. Thiobarbituric acid (TBA, mg malonaldehyde/kg), total volatile content (TVB-N, mg N/100 g), total aerobic mesophilic plate count, pH value, color measurement, and sensory evaluation were used to determine quality changes. After 8 months of storage, TBA values reached 0.83 ± 0.09 mg malonaldehyde/kg. Despite a marked increase in the TBA value at Month 8, the soup was still of acceptable quality. The TVB-N value was close to the European Commission limit on fresh fish at Month 4, and further increase was not significant (p > 0.05). Total aerobic mesophilic count reached a maximum value of 4.15 ± 0.23 log cfu/g at Month 2 with 3.20 ± 0.02 log cfu/g at Month 8. The soup had an overall acceptability score of 7.16 ± 0.68 (“like moderately” on a 1- to 9-point hedonic scale). Results suggest that smoked trout trimmings can be used to maximize the value of co-products by producing a ready-to-eat soup.

High pressure pasteurization of apple pieces in syrup: Microbiological shelf-life and quality evolution during refrigerated storage

The inactivation of Candida lipolytica LMM02.68 and Escherichia coli LMM1010 on 1-cm apple cubes in acidified glucose solution (12.5 or 25.0% d-glucose) by high pressure treatment at 200–650 MPa for 10 min at 25 or 40 °C was investigated. At 25 °C and in all solutions, a 6-log reduction of C. lipolytica and E. coli was achieved at 400 and 600 MPa, respectively. Subsequently the shelf-life of HP-treated packaged apple pieces in 25.0% acidified glucose solution was studied during refrigerated storage (7 °C) in a pilot-scale study with 306 packages containing 200 g of product. The microbiological shelf-life of the product, defined as the time when the aerobic mesophilic plate count or mold and yeast count first exceeded 7 log CFU/g, was extended from 15 days at 7 °C for the untreated product to at least 90 days after treatment at 450 MPa at 10 °C for 10 min. HP treatment had no measurable effect on the hardness of the apple pieces, but to prevent browning during the entire storage period, addition of sodium metabisulfite was necessary. This work demonstrates that HP treatment is well suited to preserve fruit pieces in syrup for extended periods with maximal quality retention.

Microbial Performance of Food Safety Management Systems Implemented in the Lamb Production Chain

The actual microbial status of the lamb production chain at three slaughterhouses, one processing plant, and five butcher shops selling whole or cut lamb carcasses to consumers was assessed with a previously developed microbial assessment scheme. All studied establishments had a food safety management system (FSMS) that was implemented according to legislative requirements. Microbial safety level profiles were constructed for each establishment and provided clear indications of which pathogens, hygiene indicators, or utility parameters required attention to improve the performance of the microbiological control protocols of the implemented FSMS. The highest contamination was found in the slaughterhouses in samples taken from the meat products (aerobic mesophilic plate counts [AMPs] of 3.40 to 6.63 log CFU/cm(2) and Enterobacteriaceae counts of 1.00 to 4.62 log CFU/cm(2)), contact surfaces (AMPs of 2.44 to 8.92 log CFU/cm(2)), and operators' hands and/or gloves (AMPs of 2.84 to 8.09 log CFU/cm(2)), especially after hide removal and evisceration. The microbial assessment scheme is a useful tool for providing insight into the actual microbiological results achieved with an FSMS implemented in establishments at various stages along the lamb production chain.