Growth of Clostridium sporogenes and Staphylococcus aureus at Different Temperatures in Cooked Corned Beef Made with Reduced Levels of Sodium Chloride

Cooked corned beef made with normal (ca.2.5%) or a reduced (ca.1.5%) level of salt were inoculated with either clostridial spores or with staphylococci and incubated at temperatures ranging from 5 - 30°C. Growth of indigenous microflora, staphylococci, or clostridia was similar at both salt levels at a given incubation temperature. However, increasing the abuse temperature greatly increased the growth of all organisms. Outgrowth of clostridial spores occurred in ground cooked corned beef which contained the normal residual nitrite of 40 - 45 ppm; readdition of nitrite to 150 ppm at the time of inoculation markedly reduced growth. Gas production was not a good indicator of clostridial growth.     

Effects of Varying Levels of Chloride Salts on Clostridium Botulinum Toxin Production in Turkey Frankfurters

Inhibitory effects of sodium chloride (NaCl), potassium chloride (KCl), and magnesium chloride (MgCl₂) on C. botulinum inoculated turkey frankfurter emulsions were determined. Ionic strengths (I.S.) of 0.42, 0.55, and 0.68 were compared (equivalent to 2.5%, 3.25%, and 4.0% NaCl). Sodium nitrite levels were constant at 150 ppm. Inoculated emulsions (10³ spores/g) were incubated and maintained at 27°C. In-creasing NaCl from I.S. 0.42 to 0.68 delayed toxin production from 4 days to at least 40 days. KCl was almost as effective as NaCl at I.S. 0.42, but inferior at higher levels. MgCl₂ did not demonstrate any inhibitory effect. Fifty percent substitution of 2.5% NaCl with KCl or MgCl₂ generally reduced time for toxin production to occur.     

Effects of Sodium Chloride Reduction and Polyphosphate Addition on Clostridium Botulinum Toxin Production in Turkey Frankfurters

Mechanically deboned turkey meat emulsions were made with 1.0, 1.5, 2.0, 2.5, or 3.0% salt (NaCl), or with combinations of 1.5% or 2.0% salt with 0.4% sodium tripolyphosphate (TPP), sodium hexametaphosphate (HMP), or sodium acid pyrophosphate (SAPP). Sodium nitrite levels were constant at 150 ppm. Emulsions were inoculated with a mixture of 10 strains of C. botulinum (10³/g) and incubated at 27°C. Increasing NaCl content from 1.0% to 3.0% delayed toxin production by 3 days on the average. Toxin production was detected earlier when TPP was added, HMP had no effect, and SAPP delayed toxin production.     

Effect of Mechanically Separated Pork, Sodium Erythorbate and Sodium Nitrite Combinations on Clostridium sporogenes Survival and Growth in Liver Sausage

Liver sausage formulated with 50 or 75% mechanically separated pork (MSP), 75 or 150 ppm sodium nitrite and 0, 550 or 1100 ppm sodium erythorbate was examined for Clostridium sporogenes PA3679 survival and growth during refrigerated temperature storage (5°C, 6 days) and during subsequent exposure to elevated temperatures (22–24°C, 2 d). Sodium nitrite at 150 ppm inhibited clostridial growth in sausage held at 22–24°C, regardless of MSP content, if 550 ppm sodium erythorbate were also present. Sodium nitrite at 75 ppm combined with erythorbate at 550 and 1100 ppm did not inhibit C. sporogenes growth during simulated temperature mishandling of liver sausage. Residual nitrite decreased (P<0.05) with erythorbate addition but was unaffected by MSP.     

Antimicrobial Effect and Disappearance of Sodium Nitrite in Staphylococcus aureus Cultures

Staphylococcus aureus was sensitive to as little as 100 μg sodium nitrite (NaNO₂)/mL under strictly anaerobic conditions at pH 7.3 and was more sensitive at pH 6.0. S. aureus was less sensitive to NaNO₂ in the presence of 1.0-1.5 μg O₂/mL. NaNO₂ disappeared during growth of S. aureus. Disappearance was greater in the system containing 1-1.5 μg-O₂ than in strictly anaerobic cultures at an initial pH of 7.3 or 6.0. Nitrite reductase activity was not detected in either soluble or membrane fractions of S. aureus. Interaction of NaNO₂ with secreted metabolic products, dismutation of NaNO₂ by reduced pH and adsorption of NaNO₂ to S. aureus cells were not involved in the disappearance of NaNO₂. Nitrite, nitric oxide, nitrous oxide and ammonia were not end products of NaNO₂ disappearance.     

Effect of Sodium Acid Pyrophosphate and/or Potassium Sorbate on Staphylococcus aureus FRI-100 Growth and Toxin Production

The effect of food-grade sodium acid pyrophosphate (SAPP) alone or in combination with potassium sorbate (PS) on growth and toxin production by an enterotoxin A producing strain of Staphylococcus aureus was investigated. Growth of cultures was monitored by absorbancy readings (640 nm) at 5-hr intervals. Toxin production was determined by an Enzyme Linked Immunosorbent Assay (ELISA). SAPP (0.04%) in combination with PS (0.26%) was the most favorable treatment for inhibition of S. aureus growth. Concentration of toxin correlated with amount of growth in all treatments studied.     

生孢梭菌孢子生长与失活模型的统一化研究

为探讨预测微生物生长和失活的预测模型统一化问题,研究将生孢梭菌孢子热失活“镜像化”曲线用描述微生物生长的Gompertz 模型和Baranyi 模型进行模拟,并通过标准预测误对两种模型进行比较。实验表明：两种模型都能较好的模拟生孢梭菌孢子热失活,但t 检验分析差异不显著,标准预测误比较表明Gompertz 模型优于Baranyi 模型。建议用Gompertz 模型统一描述生孢梭菌孢子生长和失活情况。     

Effects of Reduced Sodium Chloride and Added Phosphates on Physical and Sensory Properties of Turkey Frankfurters

Turkey frankfurters containing 20 and 40% salt (NaCl) reductions were manufactured and evaluated in comparison to a standard formulation containing 2.5% sodium chloride. Additionally, either 0.4% sodium tripolyphosphate (TPP), sodium hexametaphosphate (HMP), or sodium acid pyrophosphate (SAPP) were incorporated into frankfurters containing similar salt reductions. Phosphates improved emulsion stability and yields, especially in formulas with 40% salt reductions. TPP increased frankfurter firmness compared to that provided by SAPP or HMP regardless of salt level, but TPP had a deleterious effect on freshness at the 2.0% salt level. SAPP was more effective than HMP in improving plumpness and enhancing salt flavor intensity. Overall, SAPP appeared to provide greater benefits than either HMP or TPP as a single polyphosphate for reduced salt turkey frankfurters.     

氯化钠和三聚磷酸钠添加量对蒸煮火腿品质的影响

研究不同氯化钠或三聚磷酸钠添加量对蒸煮火腿保水性、质构特性及颜色等指标的影响。结果表明：随着氯化钠添加量的减少,火腿的蒸煮损失率和二次杀菌失水率逐渐增大,而氯化钠添加量降低至1.25%以下时,火腿的硬度、咀嚼度、弹性、黏聚性及回复性极显著下降（P＜0.01）;添加0.20%～0.50%三聚磷酸钠对于保持火腿良好的保水性具有重要作用,为保持火腿良好的硬度和咀嚼度,其添加量需要控制在0.35%以上。     

国际科技资讯

<正>巴西研究采用超声波技术缩短摩泰台拉香肚蒸煮时间的可行性乳化肉制品加工过程中需要较长的蒸煮时间,蒸煮对产品品质和货架期均有显著影响,在食品工业中具有重要地位。蒸煮会通过促进肌纤维蛋白的结构和功能变化,增强乳化肉制品的稳定性。肉制品工业在产品高品质、健康、安全和长保质期等方面一直面临不断出现的新需求,相关研究显得尤其重要。研究表明,与常规加工相比,采用超声波处理能够在提升肉制品品质的同时缩短加工时间。鉴于此,巴西科学家在摩泰台拉香肚(Mortadellas,一种意大利生熏制品)蒸煮时考察超声波     

柠檬酸钠协同碳酸氢钠替代磷酸盐对法兰克福香肠品质的影响

为减少磷酸盐在肉类加工中的使用,降低乳化肉糜制品中磷酸盐的含量,开发高效的无磷保水剂正逐步成为肉品行业的研究热点.本研究在添加0.2％(w/w)碳酸氢钠的基础上,将柠檬酸钠分别以0.1％、0.15％、0.2％、0.25％和0.3％(w/w)的添加量与碳酸氢钠进行复配,利用其替代传统的磷酸盐,探究其对乳化肉糜制品(以法兰...     

Low Temperature Growth of Type E Clostridium botulinum Spores. 1. Effects of Sodium Chloride, Sodium Nitrite and pH

SUMMARY— The effects of pH and the addition of sodium chloride (NaCl) or sodium nitrite (NaNO₂) to trypticase-peptone-glucose (TPGI and trypticase-peptone-sucrose-yeast extract (TPSY) media upon spore outgrowth were investigated using seven Type E Clostridium botulinum strains. An inoculum of 1.0 × 10⁵ spores/ml was used and the pH was adjusted with hydrochloric acid to cover the range of 5.2 to 6.6. To define salt tolerance, NaCl was added to the media at intervals of 0.5% in the range of 2.0 to 5.0% and at 0.1% intervals in the 4.5 to 5.0% range. The effect of NaNO₂ was investigated with the addition of 100 and 200 ppm NaNO₂ to the media. Samples were incubated at 30, 15.6, 10, 7.2, 5.0 and 3.4°C. Outgrowth of all strains tested was inhibited at pH 5.2 at 15.6°C. Inhibition occurred at higher pH at lower temperatures. None of the strains showed outgrowth with 4.87% NaCl in the media at any of the incubation temperatures used. Addition of 100 and 200 ppm NaNO₂ to the media inhibited the outgrowth of the Minneapolis, 517, 26080 and A6247 strains but not the Kalamazoo and Seattle Forks strains.     

Effect of Water Activity on the Growth Kinetics of Staphylococcus aureus in Ground Bread Crumb

The kinetics of Staphylococcus aureus (strains A, B, D) growth in bread crumb were determined as a function of water activity (A_w) from 0.836 to 0.909 at pH 5.2 to 5.5 and at 35°c. Adding glycerol to the dough or equilibrating the bread over saturated salt solutions adjusted the A_w of the bread. Growth kinetics data, plotted as enumerated colony counts versus incubation time, were fitted using the logistic function to determine maximum growth rates. Similar maximum growth rates resulted, irrespective of the method used to adjust A_w. Extrapolation of growth rate‐A_w results predicts the A_w corresponding to a zero growth rate.     

金黄色葡萄球菌生物被膜生长动力学分析

利用优化的Liu动力学方程对金黄色葡萄球菌生物被膜的附着过程进行拟合得出:培养温度、培养基p H值、细菌接种浓度都对金黄色葡萄球菌生物被膜的粘附过程有影响,大约在60 min时,金黄色葡萄球菌生物被膜达到粘附平衡。在温度为35℃,p H值为7时,附着的微生物量最大,细菌接种浓度越高,附着的微生物量越大。利用Gompertz模型对生物被膜生长、成熟过程进行拟合得出:金黄色葡萄球菌生物被膜生长曲线呈现典型的S型,具有明显的延滞期、指数期和稳定期;生物被膜生长曲线表现出的S型有别于悬浮菌的生长曲线,其指数期相对较短。金黄色葡萄球菌生物被膜粘附过程、生长和成熟过程的模型矫正拟合度R2(Adj)均在0.97之上。表明Liu动力学方程以及Gompertz模型分别适用于描述外界环境与金黄色葡萄球菌生物被膜附着,生长与成熟的关系。     

Staphylococcus aureus Growth and Enterotoxin Production in Mushrooms

An enterotoxin A (SEA) producing strain of Staphylococcus aureus was inoculated onto mushrooms and incubated under simulated pre-and post-canning conditions. S. aureus grew and produced SEA in mushrooms incubated at 25°C in 10% to 20% NaCl. Growth and SEA production occurred when mushrooms were stored in plastic bags at 37°C, but not at 25°C. Mushrooms heat-processed at 121.1°C supported S. aureus growth and SEA production. No SEA was recovered from mushrooms inoculated with 1 or 10 ng SEA/g and heated at 121.1°C for 4.5 min. At higher inoculated SEA levels (100 and 1,000 ng/g), SEA was detectable after 10 min of heating. Staphylococcal enterotoxin could be present in canned mushrooms as a result of pre-, but more likely post-processing contamination.     

Inhibition of Clostridium botulinum Growth from Spore Inocula in Media Containing Sodium Acid Pyrophosphate and Potassium Sorbate with or without added Sodium Chloride

The effects of sodium acid pyrophosphate (SAPP), sodium chloride (NaCl) and/or potassium sorbate (PS) on the growth from heat-activated spores of three individual strains or a mixture of ten strains of Clostridium botulinum in peptone-yeast extract-glucose broth at pH 5.55 or 5.85 were measured spectrophotometricalty at A_630nm. Growth ratios (GR = treatment/control) based on time to reach A₆₃₀= 0.35 or 0.04 were calculated and used to compare effects of additives on strains. SAPP, NaCl, PS, and pH exhibited independent significant main effects (p≦0.01) on delaying growth in most C. botulinum strains tested. Combinations of additives without NaCl consistently caused an increase in the GR and an increase in organism sensitivity to additives in the medium. Treatments containing SAPP (0.2 or 0.4%) and PS (0.13 or 0.26%) were more effective for delaying growth than other formulations tested.     

Evaluation of survival of Staphylococcus aureus and Clostridium botulinum in charqui meats

Charqui meats were prepared in laboratory conditions in order to carry out experiments to observe the possibility of development of enterotoxigenic Staphylococcus aureus and Clostridium botulinum proteolytic type B spores and their toxins. Results demonstrated that the harsh processing conditions, high salt concentration, relative high temperature, a(w) values, inhibited the growth of both bacteria. Under our experimental conditions, S. aureus would survive throughout the sequence of salting steps i.e. brine followed by rock salting and the sunshine drying step. However, at final a(w) value of 0.70-0.75 would create conditions to inhibit its development. The other experiment revealed that C. botulinum spores germination also was impaired because of these low a(w) values. Under these conditions, charqui meats revealed to be safe products in relation to toxins from both enterotoxigenic S. aureus and C. botulinum.     

金黄色葡萄球菌在广式烧腊制品中生长与控制的研究

选用广式烧腊制品为研究对象,探究了不同因素对金黄色葡萄球菌（Staphylococcus aureus）在广式烧腊制品的生长的影响。 研究了在37 ℃及10 ℃条件下,不同pH以及含盐量对叉烧、烧鹅、烧鸭液体培养基中金黄色葡萄球菌生长的影响,并探讨了不同灭菌 方式对于叉烧、烧鸭以及烧鹅中金黄色葡萄球菌的灭菌效果。 结果显示,在37 ℃条件下,金黄色葡萄球菌在pH 3.0～10.0范围内、含盐 量≤15.0%时生长;在10 ℃条件下,金黄色葡萄球菌在pH 5.0～9.0的范围内、含盐量≤5.0%时生长。 115 ℃、20 min高压灭菌可对叉烧、 烧鹅、烧鸭三类样品中含105 CFU/g、104 CFU/g及103 CFU/g的金黄色葡萄球菌彻底灭菌。     

Staphylococcus aureus Growth and Toxin Production in Imitation Cheeses

The ability of eleven imitation (or substitute) cheeses to support the growth and toxin production of Staphylococcus aureus at 26°C was evaluated. All established enterotoxin serotypes were tested by inoculating suspensions of the requisite strains into 100-g samples of cheese (about 30 staphylococci/g). Water activity (a_w) of the cheese samples ranged from 0.942–0.973; pH values ranged from 5.33–6.14. Seven cheeses supported extensive growth of S. aureus; one or more serotypes of enterotoxin were produced in six cheeses. Enterotoxin in the cheese was detected in 4 days at 3 × 10⁶ staphylococci/g. However, the ability of some cheeses to support growth and toxin production of S. aureus could not be correlated with pH, a_w, or product formulation.     

Effect of Ether Extracts from Condensed Wood Smokes on the Growth of Aeromonas hydrophila and Staphylococcus aureus

Ether extracts of smoke condensates (“liquid smokes”) from 20 different woods were screened for antimicrobial activity. Testing was done in trypticase soy broth of pH values in the range of 5.78–6.81 against three strains each of Aeromonas hydrophila (ATCC 7965, K1414, BW37) and Staphylococcus aureus (ATCC 12600, LP, S6) incubated at 35°C. There was variation in inhibition of growth among types of liquid smoke, species, and strains of microorganisms tested. Staphylococcus aureus was generally more sensitive to inhibition than A. hydrophila strains. The most inhibitory liquid smoke was derived from the sapwood of douglas fir. Other inhibitory liquid smokes were from birch, southern yellow pine, and aspen. The least inhibitory liquid smokes were derived from lodge pole pine and mesquite woods.