Injury,Inhibition and Inactivation ofEscherichia coli O157:H7 by Potassium Sorbate and Sodium Nitrite as Affected by pH and Temperature

The effect of potassium sorbate (0–2 g litre⁻¹) and sodium nitrite (0–1 g litre⁻¹) on the growth of four strains of Escherichia coli O157: H7 in tryptic soya broth at various pH levels (pH 4·0–7·0 for sorbate, pH 5·0–8·0 for nitrite) were determined at 37°C and 4°C. Among the pH levels tested, sorbate and nitrite exhibited the highest antimicrobial activity at pH 4·0 and 5·0, respectively. At pH 5·0 and 37°C, the presence of 500 mg litre⁻¹ sorbate or 200 mg litre⁻¹ nitrite completely inhibited the growth of E coli O157: H7. While at higher pH levels, 2 g litre⁻¹ sorbate or 1 g litre⁻¹, nitrite, the highest concentration tested, did not show significant antimicrobial action against the test organisms. At 4°C and pH 5·0, the inoculated test organisms did not showed any significant growth in preservative-free control media. Different degree of inactivation and injury was observed when E coli O157: H7 strain 933 was stored in TSB (pH 5·0) containing 1 g litre⁻¹ sorbate or nitrite at 37°C. At 4°C, inactivation and injury of E coli O157: H7 cells was not observed in the medium containing sorbate or nitrite throughout the 24 h experimental period.     

Effect of Sodium Acid Pyrophosphate in Combination with Sodium Nitrite or Sodium Nitrite/Potassium Sorbate on Clostridium botulinum Growth and Toxin Production in Beef/Pork Frankfurter Emulsions

Combinations of sodium acid pyrophosphate (SAPP) with added sodium nitrite and/or potassium sorbate were tested at various pH levels to determine effectiveness in delaying Clostridium botulinum growth and toxin production in frankfurter emulsions. Formulations containing sodium nitrite (40 ppm), potassium sorbate (0.26%) and SAPP (0.4%) resulted in a greater delay of toxin production (12–18 days) than other combinations (6–12 days) having similar pH values. Treatments containing 0.4% SAPP appeared to be more inhibitory than their counterparts without SAPP, displaying less numbers of toxic samples during the 53-day storage period at 27°C. Aerobic mesophilic colony counts and residual nitrite data showed little difference among treatments.     

Sensory, Physical, and Cooking Characteristics of Bacon Processed with Varying Levels of Sodium Nitrite and Potassium Sorbate

Sensory, physical, and cooking properties were evaluated on bacon processed under commercial operations in four separate plants. Three formulations with various levels of sodium nitrite and potassium sorbate were used: (1) 0 ppm sodium nitrite, (2) 40 ppm sodium nitrite 2600 ppm potassium sorbate, and (3) 120 ppm sodium nitrite. Sliced bacon was evaluated after 10, 30, 50, and 70 days of storage. “Chemical”-like flavors, prickly mouth sensations, and “sweet aromatic” aromas were found in bacon processed with 40 ppm sodium nitrite and 2600 ppm potassium sorbate. “Microbial” flavors were found in 0 ppm sodium nitrite bacon after 50 and 70 days of storage. Bacon stored for 30 days had less cooking loss and sensory panel scores indicative of more mouth coating with fat than did bacon stored for 10 days. The degree of leanness in bacon strips had more of an influence on textural, physical, and cooking characteristics than did sodium nitrite and potassium sorbate levels.     

Sensory Attributes and Instron Measurements of Reduced-Nitrite Poultry Frankfurters With Sorbic Acid or Potassium Sorbate

Poultry frankfurters (0 and 40 ppm nitrite) with sorbic acid or potassium sorbate were studied. Flavor characteristics were influenced by nitrite but not by ascorbic acid or potassium sorbate. Frankfurters with sorbic acid were softer and those with potassium sorbate were firmer than those without. Nitrite alone increased firmness. Sorbic acid appeared to counteract that increased firmness and potassium sorbate enhanced the increase in firmness when those compounds were used in combination with nitrite in the poultry frankfurters. Simulated-teeth attachments for the Inston gave results similar to sensory firmness scores. Frankfurters with sorbic acid added had lower pH than frankfurters from other treatments.     

Effects of Potassium Sorbate Alone and in Combination with Sodium Chloride on the Growth of Salmonella typhimurium 7136

The effects of potassium sorbate alone and in combination with 2 or 3% sodium chloride (NaCl) on the growth of Salmonella typhimurium ATCC 7136 were examined. Growth studies were performed in tryptic soy brogh (adjusted to a final pH 6.3) at 22°C for 15 days and 35°C for 48 hr without shaking. A dual plating procedure was employed to monitor growth (tryptic soy agar) and development of injury in the cell population (Levine's eosine methylene blue agar + 2% NaCl + 0.05% sodium desoxycholate). The difference between these two plate counts served as a measure of the number of injured organisms. It was found that combinations of sorbate and NaCl were more effective in the inhibition of S. typhimurium than sorbate alone under the conditions and variables studied. No injury was observed in the cell population as determined by our assay procedure. The combination of 3% NaCl + 0.3% potassium sorbate was the most effective in inhibiting growth of S. typhimurium at either storage temperature.     

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.     

Potassium Sorbate Inhibition of Microorganisms Growing on Refrigerated Packaged Beef

The influence of potassium sorbate concentration (27–1325 ppm of sorbic acid) on the growth of natural flora in raw beef samples wrapped in plastic films of different oxygen permeability was studied at 0° and 4°C. Changes in aerobic plate counts, Pseudomonas spp., Brochothrix thermosphacta, Lactobacillus spp., Enterobacteriaceae and yeasts were monitored. Sorbate treatment effect on percentage increment of lag phase and reduction of growth rate during exponential phase for the different microorganisms were analyzed and antimicrobial action was evaluated by the Inhibition Index. A significant increase in the time to reach aerobic counts of 10^6.5 CFU/cm² was observed at low storage temperatures and pH values in vacuum packaged treated samples.     

Synergistic Effects of Potassium Sorbate and Sodium Benzoate on Thermal Inactivation of Yeasts

Experiments were conducted to evaluate and compare the combined effects of two preservatives, potassium sorbate and sodium benzoate, with heat on inactivation and injury of 12 strains of yeasts. There does not appear to be any correlation between ability to sporulate and z value or general heat sensitivity. Heat treatment caused an increase in sensitivities of 10 of the 12 strains to potassium sorbate (≤ 1000 ppm) as evidenced by inability to form colonies in the presence of the preservative in a recovery medium. Heated cells of five test strains had increased sensitivity to ≤ 1000 ppm of sodium benzoate. Whether exposed to potassium sorbate or not during heating, 100 ppm of the preservative in recovery broth severely retarded, and in some instances completely inhibited, growth of yeasts for a period of 10 hr post treatment. These results strongly suggest that yeasts possessing a wide range of physiological characteristics are subject to heat-injury and, furthermore, that postassium sorbate enhances injury during heating and retards or prevents repair of injury during recovery. Sensitivity to heat generally increased as the pH of the heating medium decreased from 7.0 to 2.5. Without exception, the presence of 500 ppm of potassium sorbate or sodium benzoate in the heating medium caused more rapid inactivation rates of yeasts compared to heating in the absence of preservatives. At comparable concentrations, sodium benzoate was less effective than was potassium sorbate, which exerted a significant (P ≤ 0.05) effect on increasing the rate of heat inactivation at concentrations as low as 50 ppm.     

Modeling the Growth Inhibition Kinetics of Baker's Yeast by Potassium Sorbate Using Statistical Approaches

Potassium sorbate is widely used as a preservative in food products. The inhibition kinetics of yeast growth by potassium sorbate was determined in order to predict the inhibition mechanism and develop an antimicrobial activity model. Linear regression resulted in uncompetitive growth inhibition using different concentrations of nutrients in liquid media containing yeast extract, malt extract (YM broth) and potassium sorbate. At 30°C, constant K_s of YM broth to yeast was 0.254%, maximum growth rate (μ_max) of yeast was 0.008 min^-1, and inhibition constant (K_i) of potassium sorbate to yeast growth was 0.324%. This statistical method could reliably determine the growth inhibition mechanism and kinetics.     

Antimicrobial Activity and Functionality of Reduced Sodium Chloride and Potassium Sorbate in Uncured Poultry Products

Uncured turkey and chicken breast meat products, formulated with NaCl (0.65 and 1.30%) and potassium sorbate (0 and 0.26%), were tested for antimicrobial activity and functional properties. The chopped products were inoculated (Clostridium sporogenes, 10/g) in cans and in packages and abused at 20°C. Microbial growth and gas production were rapid at both NaCl levels tested. Inclusion of potassium sorbate in the formulation delayed initiation and rate of microbial growth and gas production. Potassium sorbate also reduced (P<0.05) weight losses during cooking of the low NaCl turkey product. Rates of gas production were similar in canned and vacuum packaged products. Differences in microbial growth and gas production between chicken and turkey products were minor.     

典型酚类化合物清除亚硝酸钠及对二乙基亚硝胺生成的影响

在不同酚与亚硝酸钠物质量比、温度和pH值条件下,研究5 种典型酚类化合物（苯酚、邻苯二酚、间苯二酚、对苯二酚和连苯三酚）对亚硝酸钠的清除和对二乙基亚硝胺（diethylnitrosamine,NDEA）生成的影响。结果表明：5 种酚类化合物对亚硝酸钠都具有一定的清除作用,并随酚含量增加作用增强,其清除能力从强到弱依次为间苯二酚、邻苯二酚、连苯三酚、对苯二酚、苯酚,酸性环境和升高温度有利于清除作用。连苯三酚、对苯二酚和邻苯二酚在较低的浓度下就可显著抑制NDEA生成;苯酚不但不具有抑制作用,反而促进了NDEA生成;间苯二酚在低浓度时表现为促进作用,但在高浓度时可显著抑制NDEA生成。升高温度和弱酸性环境有利于酚类化合物对NDEA的抑制作用。     

Effects of Acids on Potassium Sorbate Inhibition of Food-Related Microorganisms in Culture Media

Effects of potassium sorbate in combination with citric, lactic, phosphoric, and hydrochloric acids on the growth of six food-related microorganisms were studied. Trypticase soy broth with 0.1 or 0.2% sorbate adjusted to pH 5.5 with any of the acids was bacteriostatic to Yersinia enterocolitica 0:17. These combinations at pH 5.5 were also bacteriostatic to Salmonello group D, and extended the lag phase of Pseudomonas fluorescens for 24 hr. Combinations of either organic acid with 0.2% sorbate at pH 5.5, reduced the growth rate of Lactobacillus plantarum and an unidentified lactobacillus isolated from frankfurters. Pseudomonas aeruginosa was unaffected by any sorbate-acid combination. Organic acids, specifically citric and lactic, potentiate the antimicrobial action of potassium sorbate.     

红曲色素、乳酸链球菌素、山梨酸钾对肉毒梭状芽孢杆菌的抑制研究

试验对红曲色素、乳酸链球菌素和山梨酸钾三种物质抑制肉毒梭状芽孢杆菌的情况与ＮａＮＯ＿２抑制肉毒梭状芽孢杆菌进行了比较，证明三种物质都具有不同程度的抑制肉毒梭菌生长的能力。Ｎｉｓｉｎ和山梨酸钾的抑制作用较红曲色素更强。     

Calcium Chloride and Potassium Sorbate Reduce Sodium Chloride used during Natural Cucumber Fermentation and Storage

Cucumber fermentation characteristics and pickle quality were evaluated in brines containing equilibrium concentrations of 0-0.4% CaCl₂, 0-0.4% potassium sorbate and 0-10% NaCl. Changes in brine pH and acidity, cucumber texture and color, coliforms, lactic acid and total bacteria, yeasts and molds were followed over time. Results indicated that cucumber spoilage would eventually take place if NaCl or potassium sorbate were not present in the brine. The presence of CaCl₂ helped maintain cucumber firmness. A synergistic action between NaCl, CaCl₂ and potassium sorbate was seen, which allowed good quality pickles to be produced when moderate amounts of all three components were present in the brine (5% NaCl, 0.2% CaCl₂, 0.2% potassium sorbate).     

Nisin、山梨酸钾复合抑制尹家鸡翅中腐败菌的研究

应用Nisin和山梨酸钾复合控制尹家鸡翅中的腐败菌。采用微生物学方法分离鸡翅中腐败菌,利用牛津杯打孔法对腐败菌进行抑制研究,应用复合制剂对产品进行保鲜作用研究。从腐败的尹家鸡翅中分离获得30株腐败菌,初步鉴定大多数为革兰氏阳性杆菌和球菌。Nisin在0.48 g/mL抑制28株腐败菌的生长,山梨酸钾在0.48 g/mL抑制27株腐败菌的生长,0.16 g/mL Nisin和0.16 g/mL山梨酸钾对30株腐败菌均有抑菌作用。应用0.24 g/mL Nisin和0.24 g/mL山梨酸钾在尹家鸡翅中保鲜作用较好,在第7天时,细菌菌落总数比对照组下降4个数量级且具有较好的感官评定,鸡翅中复合剂含量符合国家标准。尹家鸡翅中添加复合浓度0.24 g/mL的Nisin和山梨酸钾可使产品的货架期延长至7 d。     

响应面优化甲烷氧化菌素、苯甲酸钠和山梨酸钾复配剂抑菌效果

在单因素试验的基础上,利用响应面试验研究甲烷氧化菌素、苯甲酸钠和山梨酸钾复配剂对白色葡萄球菌抑菌圈直径的影响,模拟得出了抑菌圈直径的回归方程,利用Design-Expert软件分析表明：当甲烷氧化菌素-苯甲酸钠-山梨酸钾质量浓度最佳配比为0.330∶0.309∶0.144时,最大抑菌圈直径的理论值为34.99 mm,实际值为34.7 mm,此时最佳复配剂对白色葡萄球菌最小抑菌浓度为0.05 mg/mL。     

次氯酸钠、山梨酸钾、丙酸钙三因素对板栗贮藏性的研究

采用三元二次正交旋转组合设计,研究了次氯酸钠、山梨酸钾、丙酸钙在常温下对板栗好果率的影响,建立并分析了板栗好果率对三因素的函数模型。结果表明,三因素对板栗好果率的影响大小依次为丙酸钙〉山梨酸钾〉次氯酸钠;常温贮藏一个月要达到55％以上的好果率,三因素的最佳组合为次氯酸钠的浓度11．4％-19．5％,山梨酸钾的浓度2．67％-3．99％,丙酸钙的浓度1．09％-2．71％。     

Potassium Sorbate Diffusivity in American Processed and Mozzarella Cheeses

The diffusivity of potassium sorbate in cheeses was determined by using diffusion models and computer programming for examining the residual surface concentration and the penetration of surface-applied potassium sorbate into cheese. To determine diffusivity, the concentration of potassium sorbate in sliced cheese was measured by penetration time and distance from surface. The diffusivity was calculated by nonlinear regression with experimental data based on Fick's law. The diffusivity of potassium sorbate through American processed cheese was 1.31∞10^-6 cm²/sec and for Mozzarella cheese 6.74∞10^-7 cm²/sec. This indicated that Mozzarella cheese would maintain surface concentration of potassium sorbate above the critical fungistatic level two times longer than American processed cheese.     

Packaging Film Permeability in Conjunction with Sodium Nitrite, Potassium Sorbate or Lactic Acid Starter Culture for Control of Clostridium sporogenes (PA3679) Growth in Sliced Bologna

A sliced bologna was prepared and inoculated with Clostridium sporogenes (PA3679), packaged in films ranging in oxygen permeability from 0.1 cc/m²/24 hr to 120 cc/m²/24 hr and stored at 5°C, 15°C or 25°C. Subsequent bologna preparations included either 156 ppm sodium nitrite, 0.26% potassium sorbate or a lactic acid starter culture. Water activity, pH, TBA number and PA3679 counts were monitored during 28 days of storage. TBA numbers increased in packages with over 60 cc/m²/24 hr permeability but PA3679 counts did not change as a function of packaging film. Nitrite and sorbate were equally effective as inhibitors. At 15°C and 25°C, the lactic acid culture allowed the least PA3679 growth. Oxygen permeability did not alter any inhibitory effects even when increased TBA numbers resulted from using an oxygen-permeable film.