Impedance Based Rapid Method for Detection of Spoilage Organisms in UHT Low-Acid Foods

An impedance procedure was developed for rapid screening of low acid foods. Impedance Medium was used during the pre-enrichment step and the capacitance monitoring stage using the Bactometer®. Thermophiles and mesophiles were detected by incubating at 55°C and 35°C. Anaerobes were detected by either placing the Bactometer® in an anaerobic chamber or adding an oxygen reducing membrane fraction directly to the medium. Naturally contaminated foods containing approximately 10⁴ CFU/g resulted in detections within 8 hr. Artificially contaminated products with 10⁴ CFU/g resulted in detections within 24 hr (6 hr pre-enrichment inclusive). This procedure screened low-acid foods within 24 hr, faster than the conventional methodology.     

我国生牛乳菌落总数和体细胞数调查及其影响因素分析

目的调查我国生牛乳菌落总数和体细胞数情况,分析养殖模式与区域等因素对我国生牛乳菌落总数和体细胞数的影响。方法对17个省(市、自治区)2014—2015年连续12个月共17 527份生牛乳样品菌落总数的数据和6 633份体细胞数的数据进行研究,采用SPSS 19.0的Kruskal-Wallis秩和检验分析养殖模式和养殖区域对生牛乳菌落总数和体细胞数的影响。结果我国生牛乳中的菌落总数、体细胞数的平均值分别为3.27×10~5CFU/ml、46.0万个/ml。来自牧场、养殖小区、散户的生牛乳样品菌落总数的中位数分别为1.00×10~5、1.85×10~5、2.37×10~5CFU/ml,体细胞数的中位数分别为35.0万、73.0万、59.1万个/ml;东北内蒙古产区、华北产区、南方产区、大城市周边产区、西部产区生牛乳菌落总数的中位数分别为2.40×10~5、1.43×10~5、1.50×10~5、1.60×10~5、2.14×10~5CFU/ml,体细胞数的中位数分别为57.2万、33.0万、38.2万、56.0万、40.0万个/ml。结论生牛乳的菌落总数99%以上均可达到我国现行标准的要求,标准对菌落总数的要求有进一步提升的空间。来自大规模牧场的生牛乳菌落总数和体细胞数均较低。     

Aciduric and Heat Resistant Microorganisms in Apple Juice and Cider Processing Operations

Site visits to 15 apple juice or cider facilities were conducted in New York State. Washed apples, pulp, press juice, final product, and other samples, when appropriate, were sampled aseptically. Samples were plated on acidified potato dextrose agar, before and after heating at 70°C for 1-2 hr. For unheated samples, molds predominated in fruit, yeasts and molds in pulp, and yeasts in press and final juice samples. Average counts were 2.8 × 10⁴, 7.3 × 10⁴, 1.7 × 10⁵, and 1.4 × 10⁵/g, respectively. Heat resistant yeasts, molds, and bacteria were isolated frequently, generally at a level of less than 1 per log.     

Fate of Listeria on various food contact and noncontact surfaces when treated with bacteriophage

Study objective was to determine efficacy of a bacteriophage suspension against Listeria spp. when applied to three common types of materials used in food manufacturing facilities. Materials included two food contact materials (stainless steel and polyurethane thermoplastic belting) and one noncontact material (epoxy flooring). Coupons of each material were inoculated with a cocktail containing L. monocytogenes and L. innocua (4 to 5-log₁₀ CFU/cm²). Two phage concentrations and a control, 0, 2 × 10⁷ and 1 × 10⁸ PFU/cm² were evaluated. Treated samples were held at 4 or 20°C for 1 and 3 hr to determine the effect of temperature and treatment time. Reductions in Listeria populations ranged from 1.27 to 3.33 log₁₀ CFU/cm² on stainless steel, from 1.17 to 2.76 log₁₀ CFU/cm² on polyurethane thermoplastic belting, and from 1.19 to 1.76 log₁₀ CFU/cm² on epoxy resin flooring. Higher phage concentration (1 × 10⁸ PFU/cm²), longer treatment time (3 hr), and processing area temperature of 20°C showed a greater (p ≤ .05) reduction of Listeria on the stainless-steel and polyurethane thermoplastic belting coupons. Overall, Listeria reduction by phage treatment occurred on all three materials tested, under all conditions.     

湿粉类制品蜡样芽胞杆菌污染风险及控制研究

目的 以广州市为例分析湿粉类制品蜡样芽胞杆菌污染情况和生产加工过程的风险点,提出相应的控制措施.方法 选择广州市范围生产湿粉类制品的生产单位,采集生产环节和销售环节样品及同批次产品生产使用的原料,对蜡样芽胞杆菌进行定量检测.结果 共采集32份出厂的湿粉类制品、139份市售湿粉类制品、32份原料大米、5份小麦淀粉、3份玉...     

Shelf Life of Shrimp (Penaeus merguiensis) Stored at Different Temperatures

The sensory, microbiological and biochemical changes were determined in shrimp (Penaeus merguiensis) stored at 0° to 35°C. Mean aerobic plate count of fresh shrimp, initially 5.0 × 10⁵ CFU/g, increased with time and temperature to 6.4 × 10⁹ CFU/g at 35°C after 24 hr. A total of 560 different bacteria were isolated and identified. In addition, the dominant organisms were tested for ability to reduce TMAO, produce indole and hydrolyze protein. The initial bacteria were 30% Gram + organisms but changed to predominantly Grampsychrotrophs at lower temperatures and to mesophiles at higher temperatures. Odor, texture and color qualities decreased; TMA, TVB, pH and Indole increased with time and temperature. Shelf life of shrimp ranged from 7 hr at 35°C to 13 days at 0°C.     

MICROBIAL GROWTH IN PACKAGED FRESH ASPARAGUS

The effects of storage temperature and time on the microflora of fresh, vacuum packaged, and modified atmospheres packaged asparagus (Asparagus officinalis) were analyzed. Total aerobic mesophilic, psychrophilic, lactic acid bacteria, Enterobacteriaceae, and yeast and molds were determined as a function of time. The effect of washing on the original microflora of the asparagus and the growth of the different microbial groups during the storage time were checked. From day 8, a progressive increase in the mesophile and psychrophile counts in both types of packaging was observed. At the end of the experiment (day 21), the mesophile and psychrophile counts were all 10⁷ CFU/g, for both types of packaging. In the vacuum packaging, the final enterobacteria counts (2.5 × 10² CFU/g) and yeast and molds (10 CFU/g) were lower than in the polyethylene bag packaged asparagus, which showed enterobacteria counts of 7.3 × 10⁴ CFU/g) and yeast and mold counts of 2.3 × 10⁴ CFU/g. The non-packaged asparagus showed low counts from the fourth day due to their heavy dehydration caused by the low relative humidity in the storage chamber.     

Recovery of Protein and Microorganisms From Shrimp Peeler Effluent

A study was conducted to determine the quantity and quality of proteinaceous solids recoverable from mechanical shrimp peeler effluent. Solids were recovered by HCl precipitation and centrifugation. Recovery of solids from untreated effluent was 1%-2% by weight (ca. 10% protein) and was predictable by turbidity. The precipitation/centrifugation process reduced supernatant total organic nitrogen and biochemical oxygen demand approximately 50% and turbidity by over 90% compared with untreated effluent. Total aerobic plate counts (APC) of bacteria recovered from unprocessed shrimp and precipitated solids were 10⁵-10⁶ CFU/g, approximately 1.5 log units greater than from peeled shrimp or untreated shrimp effluent. Total APC of bacteria recovered from clarified effluent was 3.2 × 10¹ CFU/mL.     

Enhancement of Biological Properties of Soymilk by Fermentation

Soymilk has attracted much interest in the food industry because of its health- promoting properties. Fermentation with lactic acid bacteria is known to provide value addition to soymilk by reducing the beany flavor and content of indigestible oligosaccharides and by enhancing the bioavailability of isoflavones, resulting in a nutritious probiotic food product. In the present study, Soymilk fermentation was studied using Lactobacillus acidophilus strain isolated from ragi, and effect of soymilk supplementation on the fermentation characteristics was also investigated. Viable count of 1.99 × 10⁹ CFU/mL sample and 630.1 U/g of β-glucosidase activity were determined in soymilk after 12 h of fermentation. Soymilk supplementation with skimmed milk powder at 5% level gave best results with viable counts of 22.9 × 10⁹ CFU/ml sample or 212.9 × 10⁹ CFU/g solids; 764 U/g of β-glucosidase activity, 1.44% la titratable acidity and pH of 3.9. Daidzein and genistein profile in fermented soymilk showed that 45.8% and 57.5% of respective isoflavones existing as aglycone form, indicating enhancement of the biological property of soymilk through improvement of health-relevant bioactive forms.     

Characterization of native microbial populations on Swiss chard (Beta vulgaris,type cicla) cultivated by organic methods

The native microflora of fresh Swiss chard (Beta vulgaris, type cicla) cultivated by organic methods was quantified and characterised. The concentration of the different microorganism groups presented less variability among different lots than results found on chard leaves produced by conventional methods. These results would indicate a greater degree of homogeneity among the different samples of chard produced by organic procedures.The microbial populations on Swiss chard leaves produced by organic methods were 6.8×10⁵ CFU/g for mesophilic microorganisms, 3.9×10³ CFU/g for psycrotrophic microorganisms, 1.4×10⁴ CFU/g for lactic acid microorganisms, 5.1×10³ CFU/g for total coliforms and 1.66×10³ CFU/g for Staphylococcus spp. Neither fecal coliforms nor human pathogens were identified. Immersion of organic Swiss chard leaves in tap water at 18°C for 4 min reduced microbial populations but did not accomplish more than 70% removal in any of the populations under study.     

Enterotoxin C2 Production by S. aureus in Entree Salads

Staphylococcus aureus strain 361 was inoculated into salads containing chicken, macaroni, potato, or artificially flavored soy product. Egg was added to some. The pH averaged 6.2 in the control made with water dressing rather than vinegar, 4.7 with home-style cooked salad dressing, and 4.9 with commercial salad dressing. Following incubation at 37°C for 8 or 24 hr, pH, total counts, and enterotoxin C₂ were determined. Enterotoxin was detected at 8 hr in all macaroni and potato dressing types. At 8 hr, enterotoxin was not detected in most soy product or chicken salads. By 24 hr the lowest levels were in the soy product salads but all products contained toxin. When the inoculum level was reduced below the 10⁵ CFU per g used in the main study, enterotoxin production was delayed but occurred at 8 hr if the inoculum level was 10³.     

SOME MICROBIOLOGICAL CHARACTERISTICS OF HERBED CHEESES

Fifty herbed cheese samples, in which herbs (Allium spp.) were used at production, were analyzed for some microbiological quality characteristics. Cheese samples were collected from different retailers in four counties of Eastern Turkey. Presumptive coliform bacteria, generic Escherichia coli, Staphylococcus aureus, lactic acid bacteria, yeast, mold and sulfite‐reducing anaerobic bacteria counts were examined as general microbiologic quality parameters, and the average bacteria counts were 2.1 × 10⁵, 3.1 × 10⁴, 1.1 × 10⁵, 2.2 × 10⁷, 6.8 × 10², 7.0 × 10⁶ and 3.2 × 10¹ cfu/g, respectively. The number of samples, in which the above selected bacteria have been detected, were 32 (64%), 29 (58%), 23 (46%), 50 (100%), 5 (10%), 46 (92%) and 9 (18%), respectively. Salmonella spp., Listeria monocytogenes and E. coli O157:H7 were targeted as foodborne pathogens, and the presence of those pathogens in samples were 10% (in five samples), 8% (in four samples) and 4% (in two samples), respectively. It was found that herbed cheeses containing foodborne pathogens raise an important risk for consumers’ health. Standardization and modernization of herbed cheese production, in which hygienic conditions and quality controls would be applicable, seems a necessity in order to prevent possible public health risks from herbed cheeses.     

Physicochemical and microbiological characteristics and mineral content of herby cacik,a traditional Turkish dairy product

Changes in the physicochemical properties, mineral and heavy metal content and microbial flora of cacik samples were studied over a storage period of 30 d. The analysis results were in the ranges as follows: dry matter content 16.45–20.76%, fat 1.45–4.30%, protein 8.14–13.87%, total ash 0.96–4.19%, salt 0.25–3.15%. There were significant differences in dry matter, fat, salt, protein and ash content of the cacik samples (P < 0.05). There were significant differences in Ca, P, Na, Mg, Cu, Fe, Zn and Mn content of the cacik samples (P < 0.05). Total aerobic mesophilic bacteria (TAMB) and enterococci reached levels above 10⁴ and 10³ CFU g^?1, respectively. Coliforms and Staphylococcus aureus were not detected in any of the cacik samples during the storage period. Lactic acid bacteria (LAB) on MRS and M17 agars were the dominant bacteria. The cacik samples had LAB counts up to 10^4.4 CFU g^?1. Copyright © 2005 Society of Chemical Industry     

Optimization of Fermentation Parameters for the Production of Concentrated Starters from Nonbitter Streptococcus lacti INIA 12

Streptococcus lactis INIA 12, a selected nonbitter strain, reached its maximum counts and its highest lactic acid production in a culture medium containing 125 g/L skim milk powder, fortified with 5 g/L yeast extract and digested with 10 ppm papain for 20 min at 65°C. Lactose added to the medium did not enhance growth rate or biomass production. A growth temperature of 32°C and the maintenance of pH at 6.80, with 10N NaOH as the neutralizer, were the optimum fermentation parameters in batch cultures. In ten 40-L fermentations carried out at 32°C and pH 6.80, with a 5% inoculum, a 0.2 kg/cm² nitrogen head space pressure and a stirring rate of 80 rpm, maximum counts of S. lactis (10¹⁰ CFU/mL) were reached after incubation for 6 hr at 32°C and pH 6.80.     

Listeria monocytogenes in genussfertigen Lebensmitteln: eine Auswertung der amtlichen Untersuchungen in der Schweiz der Jahre 2006–2008

In the years 2006–2008, 13.978 ready-to-eat foodstuffs were tested by official laboratories of food control in Switzerland for compliance with legal limits for Listeria monocytogenes. Totally, the pathogen could be detected in 67 foods (0,5 % of all samples). Most frequently, raw meat cured sausages (proportion of positive samples 3,9 %) were contaminated followed by smoked fishes (1,4 %) and semi-hard cheeses (1,1 %). For soft cheese, a rather low contamination frequency of 0,3 % was shown. Quantification of L. monocytogenes was possible in 18 ready-to-eat foods from the market and six out of them showed high counts of >1.000 CFU per gram. Concerned were a sandwich with smoked salmon and other components (250.000 CFU/g), smoked salmon (180.000 CFU/g), smoked trout (13.000 CFU/g), semi-hard cheese (9.200 CFU/g) and salami (5.500 and 1.850 CFU/g). In connection with cases of listeriosis, the highest measured count (5 × 10⁷ CFU/ml) was found in liquid cream of a private household where it was probably contaminated and not adequately stored. Surprisingly, in 931 desserts and confectioneries, in 384 ice-creams, in 3.567 pre-cooked foods and in 806 samples of raw fruits or vegetables, L. monocytogenes was never isolated and in 720 delicatessen salads only once (Celery salad with <100 CFU/g). The evaluation of a high number of laboratory data allowed identifying the current focal points of risk, an information which is important for a risk-based design of future control activities.     

Populations and potential association of Saccharomyces cerevisiae with lactic acid bacteria in naturally fermented Korean rice wine

The microbial populations focused on predominant yeast species and lactic acid bacteria (LAB) in 15 commercial makgeolli brands, where a fungal starter nuruk was used were examined. Viable yeast counts were obtained on yeast potato dextrose (YPD) and MRS agar containing sodium azide. MRS-C (0.1% cycloheximide supplemented) was used for selective counts of LAB. Saccharomyces cerevisiae was found to be predominant in the 15 samples tested, with an average count of 4.6×10⁷ CFU/mL. Contrary to the earlier studies, Lactobacillus plantarum and Weissella cibaria were shown as predominant LAB species with an average count of 1.7×10⁷ CFU/mL. Surprisingly, as many as 7 log viable cells/mL were present at the ethyl alcohol concentration of 6–7%. The data from real-time PCR also indicated that the yeast populations remains almost constant during the refrigerated storage of 12 days, while that of LAB decrease slightly first 9 days and increase after then, despite the overall increase in acidity. Data from the differential microbial counts suggest that yeast S. cerevisiae might be associated with 2 LAB species, L. plantarum and W. cibaria, under ethyl alcohol stress during the turbid rice wine fermentation.     

Inhibition of enterotoxicogenic strains Bacillus cereus GT1 and Staphylococcus aureus S1 isolated from double white cream cheese

In this study three different food preservatives (sodium nitrate, sodium benzoate and sodium sorbate) were used to evaluate their effect on two enterotoxicogenic strains (Bacillus cereus GT1 and Staphylococcus aureus S1). A significant decrease in the viability and production of virulence factors was observed. Yet, obvious tolerance to increasing concentrations (from 1 to 6?g/l) of the three preservatives was recorded reflecting possible resistance mechanisms within the tested strains. The two strains were subjected to increasing doses of gamma radiation (1, 2, 3, 4, 5, 6, 7, 8, 9 and 10?kGy). Obvious correlation was observed between the initial counts of bacterial spores contaminating the products and the required dose for their complete elimination. Whereas the eliminating dose of B. cereus GT1 strain was 10?kGy only 4?kGy was sufficient to suppress the growth and virulence of S. aureus S1, reflecting its sensitivity to low doses of gamma irradiation. Also, inhibition of the two strains by probiotic strain Bacillus pumilus G4 was studied both in situ (in cheese) and in vitro (in culture media). The viable cell population of B. cereus GT1 increased from 10⁶ to 2.9?×?10⁸?CFU/g within 60?h in controls but decreased from 2.1?×?10⁶ to 2.3?×?10³?CFU/g after treatment with the probiotic strain. No viable count was observed after 60?h of incubation. Whereas, the viable cell population of S. aureus S1 increased from 10⁶ to 2.5?×?10⁸?CFU/g within 60?h in controls but decreased from 1.5?×?10⁶ to 4.3?×?10²?CFU/g after treatment with the probiotic strain. No viable count was observed after 54?h of incubation.     

Selected Microbiological Properties of Kashar Cheese Samples Preserved with Potassium Sorbate

Kashar cheese, traditionally produced, is a popular dairy product in Turkey. Kashar cheese—a hard cheese—is frequently contaminated with mould. Potassium sorbate can be used for preservation of Kashar cheese. In this article, the effect of potassium sorbate on the microbiological characteristics of Kashar cheese was studied. It was found that the microbial counts at stored at 4 ± 0.1°C for 12 and 24 hours were not different from that of fresh milk samples. The means of total aerobic mesophilic bacteria (TAMB), lactic acid bacteria (LAB), coliforms, Staphylococcus aureus, proteolytic microorganisms, lipolytic bacteria, psychrotrophic bacteria and yeast-moulds in the cheese samples were determined as 4.3 × 10⁷, 2.1 × 10⁵, 3.5 × 10, 1.2 × 10, 4.5 × 10⁵, 5.6 × 10⁴, 1.7 × 10³, and 4.8 × 10⁴ cfu/g, respectively. The addition of potassium sorbate to Kashar cheese decreased the coliform and yeast-mould counts. The yeast and mould counts of cheese samples with added dry potassium sorbate were lower than that of fluid potassium sorbate.     

Estimation of Microbial Populations in Frozen Concentrated Orange Juice using Automated Impedance Measurements

Automated impedance measurements were used to classify samples of frozen concentrated orange juice as acceptable (< 10⁴ CFU/ml) or unacceptable (> 10⁴ CFU/ml). Calibration curves relating initial microbial concentration to impedance detection time were generated for several orange juice isolates. Cut-off times of 10.2 hr for bacteria and 15.8 hr for yeasts were adopted. More than 96% of 468 retail samples were correctly classified using automated impedance measurements. This technique has several advantages over other automated systems, including lower cost and reduced demand for technician time, and it provides reliable results much quicker than does the agar plate count.     

Reproducibility of Microbiological Counts on Frozen Cod: A Collaborative Study

Reproducibility of aerobic plate count (APC), coliform and fecal coliform counts in frozen cod was examined by 14 laboratories (3 government, 4 university and 7 industry) using primarily FDA recommended procedures. In order to assure homogeneity of samples, the fish was comminuted and thoroughly mixed. The 35°C and the “room temperature” (26°C) APC on Sample A (a good quality product) were 1.3 × 10⁵/g and 2.6 × 10⁵/g, respectively, and for Sample B (a questionable quality product) the counts were 2.9 × 10⁵/g and 6.4 × 10⁵/g, respectively. Standard deviations among counts (log₁₀ values) were 0.26 and 0.32 for the 35°C counts and 0.24 and 0.40 for the 26°C counts of Sample A and B, respectively. The std. dev. were reduced to 0.19, 0.22, 0.17 and 0.25, respectively, when counts that did not show significant overlap (based on Dur can's New Multiple Range Test) were excluded from the calculations. Coliform counts on Sample A (not inoculated) ranged from <30 to 4.6 × 10⁵/100g. Coliform and fecal coliform counts for Sample B (inoculated at estimated level of 1 × 10⁴/100g) were 5.8 × 10³/100g and 5.5 × 10³/100g, with a std. dev. of 0.43 and (.37, respectively. The std. dev. for the coliform counts was reduced to 0.30 when counts from one laboratory were excluded, based on Duncan's New Multiple Range Test.