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1.
The purpose of this study was to assess the chemical and microbial characteristics of 12 batches of artisanal Fiore Sardo, a protected designation of origin (PDO) hard cheese made from raw ewe's milk without addition of starters, during maturation. High standard deviations were observed for moisture percentage, total solids percentage and NaCl percentage content, possibly owing to differences in manufacturing processes and/or milk composition. Total mesophilic bacteria varied between 10 log10 cfu/g in 48-h-old cheese samples and 3 log10 cfu/g in 9-month-old samples. Total coliforms and staphylococci showed the highest counts at 48 h of ripening then decreased significantly, dropping to levels below 2 log10 cfu/g at 3 months of maturation. Lactic acid bacteria and enterococci were the dominant micro-organisms throughout maturation. They were mainly represented by the species Lactococcus lactis ssp. lactis, Enterococcus faecium, Lactobacillus plantarum and Lactobacillus casei group. Low levels of yeasts were detected throughout the maturation period of the cheese. Debaryomyces hansenii and Kluyveromyces lactis var. lactis were the prevalent yeast species isolated.  相似文献   

2.
We studied the microbial changes on fresh (still warm) pork carcasses immediately after electrostatic spraying of lactic acid solutions and during chilled storage. Lactic acid decontamination (LAD) included electrostatic spraying of hot (55C) solutions of 1% lactic acid for 90 s and 2%- and 5% lactic acid for 30 and 90 s. The treatments increased the carcass surface temperature from 22C to about 32–43C. The bactericidal activity of lactic acid killed mainly Gram-negative bacteria. Reductions in "total" psychrotrophic Gram-negative and Entero-bacteriaceae counts were found reliable indicators for the efficacy of LAD. Hot 2–5% LAD treatments achieved overall reductions in Gram-negative psychrotrophs ranging from 0.8 to more than 1.4 log10 cfu per cm2. Overall reductions in mesophilic Enterobacteriaceae counts ranged from approximately 1.2 to more than 1.8 log10 cfu per cm2. Treatments with 1% lactic acid achieved marginal 0.5–0.6 overall log10 reductions in these groups of organisms. Bactericidal effects after LAD occurred during a lag period of whose duration increased with the lactic acid concentration of the spray solution. The lag lasted less than 1 day on 1% LAD, 2 days on 2% LAD and 4 days on 5% LAD meat. During these lags the meat surface pH rose from pH 2.7 to 3.2 immediately after LAD to pH 4.8 to 5.2. During aerobic chilled storage after LAD the growth of Gram-negative psychrotrophs was controlled only temporarily. These organisms became the dominant group of organisms. The practical utility of electrostatic spraying of fresh pork carcasses with hot 1–5% LAD to improve the keeping quality is questionable .  相似文献   

3.
The survival of food pathogens during frozen storage of chicken hamburgers was evaluated. Hamburgers were contaminated with Escherichia coli (ECHC), Staphylococcus aureus (SAFH) and Salmonella Enteritidis (SE86), separately, and stored at −18C for 28 days. Results demonstrated reductions of 0.63 log10 cfu/g, 0.73 log10 cfu/g and 0.27 log10 most probable number/g in the populations of ECHC, SAFH and SE86, respectively. These microorganisms were also stored at −18C in 0.1% peptone water and presented significantly different reductions ( P <  0.05) when compared with frozen hamburgers, suggesting that components of chicken hamburger may exert a cryoprotective effect on microbial cells.

PRACTICAL APPLICATIONS


Even though Brazilian poultry meat industries present high levels of quality control, the presence of bacterial pathogens in hamburgers may occur. In Brazil, chicken hamburgers are frequently commercialized frozen, and it is well established that frozen temperatures are able to avoid microbial growth. However, frozen temperatures can also be able to inactivate part of the bacterial population, and the magnitude of its effect will vary according to the type of food and the process that it was submitted. This study evaluated the survival of Escherichia coli , Staphylococcus aureus , and Salmonella Enteritidis in frozen hamburgers, aiming to verify if this process could provide an additional margin of safety to this product.  相似文献   

4.
ABSTRACT: Contamination levels (cfu/g and cfu/cm2) of indicator microorganisms in retail broiler chicken carcasses in León (Spain) were investigated. Counts (log10 cfu/g) were 5.19, 3.04, 2.73, 3.38, and 3.16 for total aerobic counts ( TAC), Enterobacteriaceae , coliforms determined by the standard VRBA method (coliforms-VRBA), coliforms determined by the Hydrophobic Grid Membrane Filter method (coliforms-HGMF), and Escherichia coli (HGMF method), respectively. These values fit into the microbiological criteria for poultry meat consulted. A low correlation coefficient was found between TAC and Enterobacteriaceae counts (r = 0.308; P = 0.053) and between coliforms-VRBA and coliforms-HGMF counts ( r = 0.398; P = 0.048). The determination method had a significant influence on the coliform counts obtained. All broiler chicken carcasses harbored E. coli biotype I. E. coli biotype II was detected in 20% of the samples. The HGMF method was not completely specific for detecting E. coli since 11.25% of false positive colonies were found.  相似文献   

5.
ABSTRACT:  Smoked salmon contaminated with Listeria monocytogenes has been implicated in foodborne listeriosis. The objectives of this study were to model the growth characteristics and examine the growth relationship of L. monocytogenes and native microflora in smoked salmon. Smoked salmon samples with a native microflora count of 2.9 log10 CFU/g were inoculated with a 6-strain mixture of L. monocytogenes to levels of log10 1.6 and log10 2.8 CFU/g, and stored at 4, 8, 12, and 16 °C. Growth characteristics (lag phase duration [LPD, h], growth rate [GR, log10 CFU/h], and maximum population density [MPD, log10 CFU/g]) of L. monocytogenes and native microflora were determined. At 4 to 16 °C, the LPD, GR, and MPD were 254 to 35 h, 0.0109 to 0.0538 log10 CFU/h, and 4.9 to 6.9 log10 CFU/g for L. monocytogenes , respectively, and were 257 to 29 h, 0.0102 to 0.0565 log10 CFU/h, and 8.5 to 8.8 log10 CFU/g for native microflora. The growth characteristics of L. monocytogenes or the native microflora were not significantly different ( P > 0.05), regardless the initial levels of L. monocytogenes . Mathematical equations were developed to describe the LPD, GR, and MPD of L. monocytogenes and native microflora as a function of storage temperature. The growth relationship between L. monocytogenes and native microflora was modeled and showed that the LPD and GR of L. monocytogenes were similar to those of native microflora. These models can be used to estimate the growth characteristics of L. monocytogenes in smoked salmon, and thereby enhance the microbiological safety of the product.  相似文献   

6.
Calabaza (Curcubita moschata) is a tropical squash which is gaining popularity as a specialty crop for agricultural producers in the Northeast United States. It is commonly marketed by being cut in half, wrapped in plastic and may be held unrefrigerated until sold. This method of display is essential for consumer acceptance, yet unrefrigerated storage means that some potential for food safety problems exists. Experiments were conducted to determine the potential for bacterial growth during storage of cut calabaza. Freshly cut calabaza contained between 1.3 and 4.7 log10CFU/g aerobic mesophiles. By 10 h, duplicate counts from some samples exceeded 4 log10 CFU/g. After 24 h of room temperature storage, total aerobic plate counts ranged from 5.2 to 7.7 log10 CFU/g. Rapid bacterial growth on cut calabaza stored at room temperature indicates that these products are highly perishable, and may be able to support the growth of pathogenic bacteria, should they be introduced during the slicing process.  相似文献   

7.
In this study, the microbiological and chemical properties of Cheese helva, one of the traditional cheeses varieties produced in Turkey, was studied. This cheese is called Cheese helva since it is produced from wheat flour and milk cream. Samples were randomly collected from different villages in the Erzurum province of Turkey. The average of total aerobic mesophilic bacteria (TAMB), yeast and mould, yeast, lactic acid bacteria (LAB), proteolytic bacteria, and lipolytic bacteria were determined 4.9 × 107, 6.4 × 104, 3.5 × 103, 7.6 × 106, 4.6 × 103, and 8.6 × 103 cfu/g, respectively. 44.44% of the Cheese helva samples had no coliform; the samples that were positive for coliform showed an average of 5.1 × 103 cfu/g. Staphylococcus aureus was found < 10 cfu/g in analyzed samples. The Cheese helva was characterized by dry matter as 84.32 kg/100 kg cheese, fat as 37.44 kg/100 kg cheese, protein as 13.75 kg/100 kg cheese, NaCI as 0.58 kg/100 kg cheese, titratable acidity as 0.210%, pH as 5.30, ash as 1.49 kg/100 kg cheese, and carbohydrate as 38.56 kg/100 kg cheese. Cheese helva was found to have a high variation based on chemical composition. The microbiological tests revealed that there were high amounts of total bacteria, yeast and molds, molds, lactic acid bacteria, lipolytic bacteria, proteolytic bacteria, and coliforms.  相似文献   

8.
The microbiological status of beef carcass meat was investigated at a traditional and a semi-modern abattoir in Indonesia. Carcasses from the traditional abattoir were generally less contaminated than those from the semi-modern abattoir. The average total aerobic viable bacterial count of carcasses produced at the traditional abattoir, (log10 3.62/cm2) was found to be significantly lower (p = 0.02) at the semi-modern abattoir (log10 4.02/cm2). More than 70% of carcasses at both abattoirs were found to be positive for Escherichia coli (> 10 organisms/cm2), while Salmonellae were found on approximately 15% of carcasses at both locations.  相似文献   

9.
This study on sanitizing beef surfaces was designed to evaluate effects of mixtures of acetic, lactic, citric and ascorbic acids with individual solutions of acetic and lactic acids. Acetic acid (3%), lactic acid (3%), MA1 (2% acetic, 1% lactic, 0.25% citric and 0.1% L-ascorbic acids) and MA2 (2% lactic, 1% acetic, 0.25% citric and 0.1% L-ascorbic acids) solutions were applied to beef core samples of muscle inoculated with bacteria. Experimental variables were type, concentration and temperature of acid solutions and type of microorganisms. Overall, an increase in either acid concentration or treatment temperature decreased numbers of residual viable bacteria. Lactic acid solution was the most effective against S. typhimurium with a reduction of 2 log10 at 70°C. For enterobacteria, acetic, lactic and MA2 solutions at 70°C resulted in a 1.5 log10 reduction. MA2 was the most effective acid solution at both 45 and 70°C, whereas, lactic acid and the MA2 mixture did not differ in effectiveness at 20°C.  相似文献   

10.
西藏地区牦牛乳理化和微生物指标的检测分析   总被引:6,自引:3,他引:6  
研究了西藏地区牦牛乳的理化指标和微生物指标。从西藏3个不同地区共取48份牦牛乳样品.通过理化和微生物指标的检测及其统计分析,研究发现牦牛乳的营养成分为:脂肪7.14%(体积分数)、粗蛋白5.06%(质量分数)、干物质18.45%(质量分数)、乳糖5.00%(质量分数)和灰分0.81%(质量分数),并且不同地区各成分的质量分数也不同。牦牛乳的微生物检测结果为(对数值):细菌5.63mL^-1,芽孢菌1.76mL^-1,乳酸菌5.19mL,真菌3.03mL^-1,肠道菌3.27mL^-1,大肠杆菌2.09mL^-1和金黄色葡萄球菌3.52mL^-1,并且存在明显的地区差异性。  相似文献   

11.
W.-X. Du    C.-M. Lin    A.-T. Phu    J.A. Cornell    M.R. Marshall    C.-I. Wei 《Journal of food science》2002,67(1):292-301
ABSTRACT: The effects of storage at 0,4,10, and 22°C for 0,1,3,5, and 9 d on the quality of yellowfin tuna fillets as determined by microbiological assessment, development of some biogenic amines, and sensory analysis were studied. Tuna fillets stored at 22 °C for 3 d, 10 °C for 5 d, and 4 °C for 9 d were rated unacceptable for consumption. Those stored at 22 °C for 3 d had total aerobic bacterial count of > 8 log10 CFU/g, a histamine-producing bacterial population of 7 log10 CFU/g, and 832 ppm of histamine, 35.8 ppm of putrescine, and 147 ppm of cadaverine. A comparison of the capillary electrophoresis, AOAC fluorometric method, and gas chromatography showed a very good correlation (r2 > 0.99) among these 3 methods for histamine quantitation in tuna samples. Morganella morganii, Enterobacter agglomerans, Enterobacter intermedium, Pseudomonas fluorescens, Proteins vulgaris , and Serratia liquefaciens were the decarboxylase-positive bacterial species isolated by using the Niven's medium and identified during storage, which were responsible for histamine production in test tuna fillets.  相似文献   

12.
Abstract The shelf-life of vacuum packed, sliced, cooked chicken-breast based on sensory and microbial changes as a function of temperature (2.3, 6.5, 10, 13.5 and 17.7C) was determined. Sensory evaluation and a microbiological study charted the development of lactic acid and psychotropic bacteria and of Brochothrix thermosphacta. Six different sensory methods were used to estimate product shelf-life; of these, the method based on average smell and taste was deemed the most suitable, since these parameters had a greater impact on shelf-life. From a microbiological point of view, mean shelf-life times were estimated at each temperature and compared with the estimates of the tasting panel. In the samples stored at the three lowest study temperatures (2.3, 6.5 and 10C), lactic acid and psychotropic bacteria counts of 107–108 cfu/g were not achieved; this agrees with the absence of sensory rejection at the end of the experiment. At 13.5 and 17.7C, mean shelf-life estimated microbiologically was shorter than that estimated using sensory methods. This difference, which here amounted to at least 8 days, is due to the so-called "delayed change", reported in previous experiments with cooked meat products.  相似文献   

13.
One-hundred samples of ayib, a traditional Ethiopian cottage cheese, were purchased from Awassa market and analysed for their aerobic mesophilic counts, psychrotropic counts, yeasts and molds, coliforms, spore-formers, enterococci, lactic acid bacteria, Listeria monocytogenes, staphylococci and Bacillus cereus. The majority of the samples showed counts of mesophilic aerobic bacteria, yeasts and enterococci of 108, 107 and 107 cfu/g. About 55% of the samples were positive for coliforms and faecal coliforms. Listeria spp. were not detected in any of the samples. B. cereus and S. aureus were isolated at varying frequencies but at low numbers (102–103). The pH value of the samples varied between 3.3 and 4.6 with about 40% having pH lower than 3.7.  相似文献   

14.
Four Nigerian traditionally fermented foods (wara, nono, ogi and kununzaki) were evaluated for the presence of some microorganisms of public health concern. Among the dairy foods , Staphylococcus aureus and Klebsiella sp. were isolated from wara while Escherichia coli, Salmonella sp. and Klebsiella sp. were isolated from nono. The cereal-based fermented foods (ogi and kunu-zaki) contained Bacillus subtilis, E. coli, S. aureus, Klebsiella sp. and Enterococcus faecalis. The mesophilic aerobic counts were: 5 × 105 for wara; nono, 1.53 × 107; ogi, 3.6 × 106 and kunu-zaki, 2.6 × 106 cfu/mL. The enterobacteriaceae counts on nono, wara, ogi and kunu-zaki were 1.79 × 107, 4.5 × 105, 4.0 × 105 and 1.2 × 106 cfu/mL, respectively. No Vibrio count (detection limit: <10 cfu/mL) was recorded in all the food samples considered. The yeast and mold counts ranged from 1.0 × 105– 3.31 × 107 among the food products. The antimicrobial susceptibility patterns of the organisms isolated from dairy products (nono and wara) revealed that they were resistant to ampicillin (100%) and sensitive to gentamicin (100%) and nalidixic acid (100%). Most isolates from cereal based products (ogi and kunu-zaki) were 100% resistant to penicillin, ampicillin and chloramphenicol. This work highlights the need to maintain hygienic standards in the preparation of our locally fermented cereal and dairy foods.  相似文献   

15.
Microbiological and sensory changes of vacuum-packaged ‘gravad’ rainbow trout slices were studied during storage at 3 and 8 °C. At the time of spoilage, after 27 and 20 days of storage at 3 and 8 °C, respectively, both mesophilic viable counts (MVC) and psychrotrophic viable counts (PVC) reached 106–107cfu/g at 3 °C and 107–108 cfu/g at 8 °C. H2S-producing bacteria constituted a high proportion of the PVCs and lactic acid bacteria (LAB) counts were lower than the other determined bacterial counts. Sensory scores decreased with increasing MVC and PVC. The judges considered samples unfit for human consumption at MVC and PVC levels exceeding 106 and 107 cfu/g for samples stored at 3 and 8 °C, respectively. At respective levels of 107 and 108 cfu/g, most of the samples were deemed unfit. The main reasons for sensory rejection at both storage temperatures were the lack of the typical product odour or an ammonia off-odour and colour change to dark violet. The shelf-lives of the rainbow trout slices based on microbiological and sensory analyses were 20 days and 18 days at 3 and 8 °C, respectively.  相似文献   

16.
广西水牛原料乳微生物和理化指标分析   总被引:4,自引:0,他引:4  
按不同种群从广西取80个水牛原料乳样品,通过理化和微生物指标检测,对水牛乳营养价值和安全性进行了分析比较.主要理化检测结果如下:脂肪7.32%,蛋白质4.71%,乳糖4.67%。固形物18.42%,灰分0.84%(均为质量分数),pH值为652,密度1.030g/mL。纯种河流型水牛摩拉和尼里-拉菲的脂肪、蛋白质、固形物、灰分舍量显著低于(P〈0.05)河流-沼泽型杂交水牛。微生物检测结果如下(对数值):细菌总数5.69mL^-1,茅孢菌3.03mL^-1,乳酸菌4.79mL^-1,真菌1.80mL^-1,大肠菌群2.48mL^-1,大肠杆菌1.83mL^-1,金黄色葡萄球菌1.80mL^-1,所有样品中李斯特氏苗均未检出。地区间微生物指标差异较大。微生物含量均在可接受范围之内,但是致病菌的出现说明需要建立相关的卫生质量标准.  相似文献   

17.
The effects of pulsed electric fields (PEF) on the inactivation of Salmonella Enteritidis inoculated into liquid whole egg (LWE) and on the physical properties and the shelf-life of LWE were studied. PEF processing conditions were 1.2 mL/s flow rate, 200 pps frequency, 2.12 μs pulse duration, 25 kV/cm electric field strength, and 250 μs total treatment time. The PEF processing caused up to 1 log10 cfu/mL reduction in S. Enteritidis population in LWE. The PEF-treated samples were subjected to heat at 55C for 3.5 min to inactivate the remaining bacteria without denaturing the LWE. The combination of PEF and heat treatments led to a 4.3 log10 cfu/mL reduction in S. Enteritidis population (P < 0.05 ) and caused no significant change in viscosity, electrical conductivity, color, pH, and Brix, relative to control samples (P > 0.05 ). The PEF + 55C treated LWE samples presented significantly longer shelf-life at 4C compared with the control and heat treated samples (P < 0.05 ).  相似文献   

18.
Vacuum-packaged fresh meat products held at refrigeration temperatures have limited shelf-life expectancies, often due to growth of anaerobic lactic acid-producing bacteria. Agents that can suppress the growth of this group are beneficial. Fresh pork sausage, formulated to contain 0%, 1%, 2%, or 3% sodium lactate (SL), was vacuum packaged and stored at 4C for 0, 10, 17, 24, and 31 days. A trained sensory panel evaluated pork, salty, sour, and bitter flavors. Aerobic total plate counts (APC), anaerobic total plate counts (AnPC), aerobic lactic acid producers (ALC), anaerobic lactic acid producers (AnLC), TBA values, and pH were determined. SL depressed APC, AnPC, and AnLC. Addition of 1% SL extended shelf-life of vacuum-packaged fresh pork sausage by 1 week compared to controls; samples containing 2% and 3% SL had not reached spoilage level (log10 7.0 CFU/g) at the conclusion of this study. Addition of SL increased salty taste and prevented loss of pork flavor over time, but had no effect on sour or bitter flavors.  相似文献   

19.
ABSTRACT:  The present study evaluated the effect of modified atmosphere packaging (MAP, 5% O2/50% CO2/45% N2; treatment M), the addition of oregano oil (0.1%, v/w; treatment AO) as a natural preservative, as well as their combination (treatment MO) on the quality and shelf life extension of fresh Mediterranean swordfish fillets during a refrigerated storage (4 °C) period of 18 d. Simultaneously, swordfish fillets were stored under aerobic conditions (control treatment A, 4 °C) and on ice (usual commercial method of preservation, treatment I, 0 °C). Among the 5 treatments examined in the present study, the most effective one to inhibit the microbial and sensory spoilage proved to be the MO treatment, achieving a shelf life extension of 8 to 9 d. The dominant bacteria in the microflora of swordfish, irrespective of treatment, were the Pseudomonads and the H2S-producing bacteria, while both lactic acid bacteria (LAB) and the Enterobacteriaceae produced the lowest populations in swordfish samples kept on ice. Among the chemical indices examined, thiobarbituric acid (TBA) values showed no specific trend of lipid oxidation for swordfish, irrespective of treatment. Final trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) values for treatments, A, AO, M, and MO ranged between 1.33 and 14.29 mg N/100 g and 14.11 to 55.52 mg N/100 g, respectively, whereas for I samples they remained almost unchanged during storage. Sensory analysis (taste attribute) correlated well with microbiological analysis, indicating a shelf life of approximately 5 to 6 d for control, 10 to 11 d for AO, 12 d for I, 13 d for M, and 14 d for MO samples.  相似文献   

20.
Kunun-zaki production was monitored at six sites for the evaluation of microbiological quality, potential hazards and identification of critical control points, with the aim of setting critical limits for process optimization. Samples were collected at various stages of production and examined microbiologically for potential pathogens, before and after optimization. Critical limits were established for the critical control points identified, and two producers were selected for testing the effectiveness of corrective actions in an optimized process. Samples of kunun-zaki recorded total viable counts ranging from 3.84 to 4.80 log10 cfu/mL. Bacillus cereus, salmonellae and staphylococci were isolated in samples at 0.00–0.01, 0.57–0.76 and 1.70–2.04 log10 cfu/mL, respectively. The application of corrective measures, such as hand-washing practices, washing of processing areas and utensils, hygienic handling of materials during processing and pasteurization of final product proved effective in significantly reducing (up to 80%) the microbiological hazards associated with kunun-zaki.

PRACTICAL APPLICATIONS


The findings of this study have shown that with minimum hygienic food-handling practices, the incidence of food-borne pathogens in local foods and drinks can be reduced if not eliminated, even at household level of production. The work itself is practicable at the current level of kunun-zaki production and holds application for pilot-scale processing. The results can be used to set national standards for this and other related drinks. It also provides baseline data for standardization of kunun-zaki production, the focus of ongoing research by the authors.  相似文献   

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