优化蛹虫草浸提条件对金黄色葡萄球菌的控制效果

[目的]优化蛹虫草浸提液提取条件对金葡菌作用效果。[方法]在单因素实验(超声浸提、提取时间、料液比、浸提溶剂、提取温度)基础上,以液料比、浸提溶剂、提取温度为实验因素,进行3因素3水平正交实验,以控制率为指标,酶标仪检测正交实验中蛹虫草浸提条件对金葡菌作用效果及MIC值。[结果]正交实验优化最佳蛹虫草浸提条件为料液比1:30,浸提溶剂50%乙醇,浸提温度80℃;当蛹虫草浸提液浓度在0.025～0.1g/mL时,蛹虫草浸提液对金葡菌作用为杀菌作用,当浓度在12.5～25mg/mL时,虫草浸提液对金葡菌有显著的抑菌作用且MIC值为12.5mg/mL。[结论]不同液料比、浸提溶剂、提取温度获得的蛹虫草浸提液对金黄色葡萄球菌的作用效果不同,而超声和时间对提取效果影响不大。蛹虫草浸提液具有显著抑制或杀灭金黄色葡萄球菌的作用效果。     

Feasibility of using food-grade additives to control the growth of Clostridium perfringens

Previously, it was demonstrated that the combination of sucrose laurate (SL) ethylenediaminetetraacetate (E) and butylated hydroxyl anisole (B) (SLEB) was an effective antimicrobial agent against both gram-negative (aerobes) and gram-positive (facultative anaerobes) foodborne bacteria. This investigation examines the sensitivity of Clostridium perfringens to SLEB relative to: (1) the minimum inhibitory concentration (MIC) of SLEB required to inhibit the growth of C. perfringens and (2) the antibacterial effectiveness of different combination ratios of SLEB in fluid thioglycollate medium (FTM). Results indicated that the MIC of SLEB (1:1:1, v/v/v) against C. perfringens on tryptose sulfite cycloserine (TSC) agar was > 150 ppm at 37 degrees C. However, in FTM, a SLEB (1:1:1, v/v/v) concentration of > 100 ppm inhibited C. perfringens during an incubation (anaerobic) period of 196 h at 37 degrees C. The sensitivity of C. perfringens to different combination ratios was also investigated in FTM. The results showed that, when the concentrations of SL and E were held at 75 ppm in the SLEB combination, and the concentration of B increased from 0 to 75 ppm, C. perfringens growth increased initially during the first 24 h of incubation (37 degrees C) but remained constant during the next 48 h. Similarly, when concentrations of SL and E were held constant at 150 ppm in the SLEB combination and the B ratio increased from 50 to 150 ppm in FTM, C. perfringens viability decreased in all of the treated samples during 72-h incubation at 37 degrees C. The results indicated that SLEB was an effective inhibitor of C. perfringens growth activities, and the ratios of the components of SLEB can be adjusted to meet specific preservation needs.     

产气荚膜梭菌质控样品的研制

目的 产气荚膜梭菌是食品安全和环境监测中重点检测的致病菌之一。由于目前暂无成熟的市售产气荚膜梭菌质控菌株,本研究拟制备出能够满足要求的质控样品,可用于食品或环境领域产气荚膜梭菌检验工作中的质量控制试验和阳性对照试验。方法 依据CNAS-CL 03-A001: 2019能力验证提供者认可准则在微生物领域的应用说明,通过菌剂的均匀性、运输稳定性、储藏稳定性等指标对制备出的菌剂进行评价。结果 在均匀性实验中F值为3.01小于临界值,5 d内4℃、15℃、25 ℃条件下的储藏稳定性和28 d内4℃、-20℃、-80℃条件下运输稳定性t值均小于临界值。结论 制备的产气荚膜梭菌质控菌株均匀性良好,储藏稳定性和运输稳定性良好,可以作为试验室质控样品使用。     

Survival and growth of Clostridium perfringens in commercial no-nitrate-or-nitrite-added (natural and organic) frankfurters, hams, and bacon

The popularity of "preservative-free" foods among consumers has stimulated rapid growth of processed meats manufactured without sodium nitrite. The objective of this study was to quantify the potential for Clostridium perfringens growth in commercially available processed meats manufactured without the direct addition of nitrite or nitrate. Commercial brands of naturally cured, no-nitrate-or-nitrite-added frankfurters (10 samples), hams (7 samples), and bacon (9 samples) were obtained from retail stores and challenged with a three-strain inoculation (5 log CFU/g) of C. perfringens. Reduced inhibition (P < 0.05) was observed in seven brands of frankfurters, six brands of hams, and four brands of bacon when compared with each respective sodium nitrite-added control. In naturally cured and truly uncured commercial frankfurters, growth over time was approximately 4.7 log, while conventionally cured frankfurters exhibited growth at 1.7 log. Naturally cured ham and bacon products exhibited growth at 4.8 and 3.4 log, respectively, while their conventionally cured counterparts exhibited growth at 2.6 and 2.3 log, respectively. These products also demonstrated variation in growth response. The results indicate that commercially available natural/organic naturally cured meats have more potential for growth of this pathogen than do conventionally cured products. Natural and organic processed meats may require additional protective measures in order to consistently provide the level of safety from bacterial pathogens achieved by conventionally cured meat products, and which is expected by consumers.     

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.     

Use of natural ingredients to control growth of Clostridium perfringens in naturally cured frankfurters and hams

A major concern for processed meats marketed as natural/organic is that they do not contain nitrite in concentrations known to be most effective for inhibiting foodborne pathogens. Supplemental treatments to increase the level and consistency of antimicrobial protection in these products may be important to provide consumers with the degree of safety that they have come to expect from conventionally cured meats. Therefore, the objective of this study was to identify and test ingredients that might improve processed meat product safety without altering their natural/organic status. Eight treatments of hams and frankfurters were prepared: (A) uncured control (typical ingredients except nitrite and nitrate); (B) conventionally cured control (erythorbate, nitrite, and a lactate-diacetate blend); (C) natural nitrate cure (including starter culture containing Staphylococcus carnosus); (D) natural nitrate cure (culture and natural antimicrobial A containing a vinegar, lemon, and cherry powder blend); (E) natural nitrate cure (culture and antimicrobial B containing a cultured sugar and vinegar blend); (F) natural nitrite cure without additional antimicrobials; (G) natural nitrite cure with natural antimicrobial A; and (H) natural nitrite cure with antimicrobial B. For the hams, treatments C, D, E, and H impacted growth of Clostridium perfringens to the same extent (P < 0.05) as the conventionally cured control (approximately 2 log less growth over time than uncured control). For frankfurters, treatments D, G, and H had an effect (approximately 1 log) on growth equivalent to that of the conventionally cured control (P < 0.05). These results suggest that natural/organic cured meats have more potential for pathogen growth than conventionally cured products, but supplemental natural ingredients offer safety improvement.     

Optimizing sporulation of Clostridium perfringens

Many sporulation media have been developed for Clostridium perfringens, but none stimulates sporulation for all strains. The aim of our experiments was to develop a sporulation method using Duncan and Strong (DS) medium, which supports sporulation of a wide variety of strains. Different inoculation levels were tested, and the effects of sporulation-promoting substances and acid shock were evaluated. Furthermore, DS medium was compared with other sporulation media. Highest spore numbers in DS medium were obtained with a 10% 24-h fluid thioglycollate broth inoculum (5.0 x 10(5)/ml). Addition of theophylline and replacement of starch by raffinose increased spore yields for some strains, but most strains were not affected (average increases in log N/ml of 0.2 and 0.3, respectively). One strain was enhanced by the addition of bile, but other strains were strongly inhibited (average decrease in log N/ml of 2.5); agar did not influence sporulation. Neither short-time acid exposure nor addition of culture supernatant fluids of well-sporulating strains resulted in higher spore numbers in DS medium. None of the tested methods enhanced sporulation in general; only strain-dependent effects were obtained. Peptone bile theophylline medium was the most promising sporulation medium tested; peptone bile theophylline starch medium yielded highest spore numbers (2.5 x 10(5)/ml), but some strains failed to sporulate. In conclusion, adding theophylline to DS medium may optimize sporulation of C. perfringens, but peptone bile theophylline medium with or without starch is most suitable.     

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。     

培根生产工艺研究

通过滚揉类产品腌制剂与自制调味对改善烟熏培根口味与口感品质的研究探讨,从而提升了培根类产品品质纯正性,并且简化了生产加工工艺,提高了产品出品率。     

High pressure thermal processing for the inactivation of Clostridium perfringens spores in beef slurry

The spores of Clostridium perfringens can survive and grow in cooked/pasteurized meat, especially during the cooling of large portions. In this study, 600 MPa high pressure thermal processing (HPTP) at 75 °C for the inactivation of C. perfringens spores was compared with 75 °C thermal processing alone. The HPTP enhanced the inactivation of C. perfringens spores in beef slurry, resulting in 2.2 log reductions for HPTP vs. no reductions for thermal processing after 20 min. Then, the HPTP resistance of two C. perfringens spore strains in beef slurry at 600 MPa was compared and modeled, and the effect of temperature investigated. The NZRM 898 and NZRM 2621 exhibited similar resistance, and Weibull modeled well the log spore survivor curves. The spore inactivation increased when HPTP temperature was raised from 38 to 75 °C. The results confirm the advantage of high pressure technology to increase the thermal inactivation of C. perfringens spores in beef slurry.Industrial relevanceC. perfringens spores may cause food/meat poisoning as a result of improperly handled and prepared foods in industrial kitchens. Thermal processes at 100 °C or higher are generally carried out to ensure the elimination of these pathogenic spores. High pressure processing (HPP) is a food pasteurization technique which would help to maintain the sensorial and nutritional properties of food. Preservation of foods with HPP in conjunction with mild heat (HPTP) would enhance the spore inactivation compared to thermal processing alone at the same temperature, due to a known germination–inactivation mechanism. This technology, together with the application of Good Manufacturing Practices, including rapid cooling, is a good alternative to the traditional methods for producing safe processed meat and poultry products with enhanced sensory and nutritional quality.     

培养条件对金黄色葡萄球菌生物被膜生长的影响

以常见的食源性病原菌金黄色葡萄球菌为研究对象,采用微孔板检测法对其生物被膜形成过程中的不同影响因素进行了研究。结果表明：在37℃下,采用1．6％胰酶大豆肉汤（TSB）培养时,金黄色葡萄球菌易形成大量生物被膜;添加低浓度的单糖及双糖可以大大提高金黄色葡萄球菌形成生物被膜的能力;添加氯化钠对金黄色葡萄球菌形成生物被膜影响显著。     

Inhibition of Clostridium perfringens by Naphthoquinones

The minimum inhibitory concentrations (MICs) of several naphthoquinones (NQ) were determined in the presence or absence of nitrite (NO₂^?) against various strains of Clostridium perfringens. In fluid thioglycollate medium, MICs ranged from 70–100 ppm for 2-methyl-1,4-NQ (menadione), 200–280 ppm for 1,4-NQ, 180–250 ppm for 1,2-NQ, >500 ppm for several water-soluble derivatives and 100–300 ppm for NO₂^?. Using a type B strain in homogenized meat medium, MICs were 670 ppm for menadione, 620 ppm for 1,4-NQ and 770 ppm for NO₂^?. Nitrite, menadione and 1,4-NQ exhibited comparable and additive rather than synergistic inhibition. Some NQ compounds may have potential as partial nitrite substitutes subject to safety evaluation.     

Clostridium perfringens in Dehydrated Soups and Sauces

SUMMARY– Fifty-five samples of nationally advertised dehydrated sauce and gravy mixes, soup mixes, spaghetti sauce mixes, and cheese sauce mixes were examined for the presence of Clostridium perfringens. The organism was found in 18.2% of the samples. Spaghetti sauce mixes had the highest incidence of C. perfringens and the soup mixes had the lowest incidence. One strain possessed heat-resistant spores that were able to withstand boiling at 97.4°C for one hour prior to isolation. The presence of preservatives in the food products did not influence the presence of C. perfringens in these food preparations. No common ingredient was detected as the source of contamination. The general presence of this organism in dehydrated soups and sauces may have epidemiological significance in C. perfringens food poisoning, especially since these products are exposed to short besting periods.     

金黄色葡萄球菌生物被膜的控制方法研究进展

金黄色葡萄球菌是一种重要的食源性病原菌.金黄色葡萄球菌能够形成生物被膜,使其更加难于根除.文中对金黄色葡萄球菌生物被膜的控制方法进行了全面综述,包括去除已形成的生物被膜、杀灭生物被膜中的金黄色葡萄球菌和抑制生物被膜的形成3个主要方面,旨在为食品工业领域生物被膜的控制提供借鉴.     

Inactivation of Staphylococcus aureus by high pressure processing: An overview

Food safety is a major concern of consumers, food industry and governments, with 25 million foodborne diseases occurring annually worldwide. Staphylococcus aureus, is an extremely versatile opportunistic pathogen being responsible for staphylococcal food poisoning due to enterotoxic strains. With increasing demands for safer food, new food preservation technologies are increasingly gaining interest. In the last two decades, high pressure processing (HPP) appeared as an alternative non-thermal food preservation method promoting inactivation of some spoilage and pathogenic microorganisms, while maintaining food characteristics. Factors that modulate its efficiency will be revised, firstly based on the state-of-the art described for bacteria in general and afterwards, when studies exist, for S. aureus specifically. S. aureus inactivation by HPP, like in other microorganisms, is conditioned by cell structures and biomolecules, matrix, HPP processing conditions, the use of antimicrobials and is also dependent of the strain and growth phase. Cell membrane is the most pressure sensitive structure of S. aureus, being the lipids and proteins the most important target molecules. However, monomeric proteins such as staphylococcal enterotoxins (SE) are not affected by HPP, and strains with SE appear to be more efficiently inactivated than those without. Other phenotypic and genotypic characteristics of S. aureus strains, such as pigmentation and the presence of σ^B factor are extremely important factors determining the efficacy of HPP treatments. Inactivation of S. aureus by HPP to ensure food safety still remains a current challenge regarding the understanding of its particular barotolerance and its inactivation kinetics profile that often deviates from the simpler first order decay. Thus, this review provides state-of-the-art information for researchers interested in studying HPP inactivation of S. aureus.Industrial relevanceThis review gives an insight on the importance of Staphylococcus aureus as a foodborne versatile opportunistic pathogen and its importance from the food safety point, its barotolerance and the main reasons for this resistant behavior to high pressure processing and the mechanisms of S. aureus inactivation by HPP.     

BAX Q7系统快速检测食品中金黄色葡萄球菌效果验证

目的验证BAX Q7全自动病原菌检测系统快速检测食品中金黄色葡萄球菌的效果,以强化食品检验机构对金黄色葡萄球菌的快速检测能力和推进快速检测技术的有效应用。方法通过BAX Q7全自动病原菌检测系统和GB 4789.10-2010《食品安全国家标准-食品微生物学检验-金黄色葡萄球菌检验》2种方法同步检测定量污染的样品,比较2种方法的检测结果的符合率和灵敏度。结果采用2种方法对24份样本检测的结果基本一致,金黄色葡萄球菌检测符合率均为100%,但BAX Q7实时荧光定量PCR法相比国家标准方法检出时间缩短4～6 h,具有更高的灵敏度,而且操作简便快速。结论 BAX Q7实时荧光定量PCR系统能在食品安全突发事件中快速锁定病原菌,为溯源调查指明方向,应用于食品中金黄色葡萄球菌的快速检测合理可行。     

腌制条件对咸肉色泽的影响

探讨腌制条件对咸肉色泽的影响。通过对影响咸肉色泽的因素进行研究,以a*值、b*值、L*值为指标,初步得出影响产品复水率的各因子(食盐添加量、腌制温度和腌制时间)最佳取值范围。结论如下:食盐添加量为17%,腌制温度为16℃,腌制时间为25d。