Modelling the combined effects of salt,sorbic acid and nisin on the probability of growth of Clostridium sporogenes in a controlled environment (nutrient broth)

The safe preservation of new generation foods (high moisture, low salt, high pH and shelf stable under ambient conditions) is microbiologically challenging. The growth of Clostridium botulinum in low acid foods is a hazard for consumers. In this study the combined effect of salt (sodium chloride) (0–4% w/v), potassium sorbate (0–4% w/v) and nisin (0–300 ppm) at two different pHs (5.5 and 7) on the probability of growth of Clostridium sporogenes spores, as a non-toxigenic surrogate of C. botulinum, was evaluated in nutrient broth. Nutrient broth was used as it can easily and accurately be adjusted and controlled in terms of composition, and allows more rapid growth than is observed in food. The aims of this study were to develop probability of growth models in which the logit is expressed as a function of the concentrations of the selected preservatives. The developed models fit the data adequately. The c-values models were close to 1, indicating good predictive power. This indicates the performance of models would be satisfactory. The results of this study indicated that salt, potassium sorbate and nisin had significant inhibitory effects on the growth of C. sporogenes in high moisture (>95%) and high pH conditions (pH > 4.5). Combinations of the selected preservatives were more effective than any of them individually. The inhibitory effects of all three preservatives in the current study were pH dependent. Less stringent combinations of preservative concentrations were required experimentally to stop growth at pH 5.5 compared with pH 7.     

Effects of food preservatives on Alternaria alternata growth and tenuazonic acid production

The effects of different organic acids on Alternaria alternata growth and tenuazonic acid production (TeA) were evaluated. Both TeA pure toxin solution and TeA production in solid medium were considered. Sodium benzoate, potassium sorbate and sodium propionate, all preservatives commonly used by food industry in Argentina, were tested. TeA was stable as pure toxin solution when was treated with the salts of organic acids used. A differential effect was observed when the preservatives were evaluated in relation to A. alternata growth and TeA production in solid medium. L evels above 10mg/kg of sodium benzoate and potassium sorbate produced a total inhibition of fungal development and toxin biosynthesis. Sodium propionate produced a 59% decrease in A. alternata growth and total inhibition of TeA production only at the highest concentration of preservatives used.     

高效液相色谱法同时测定食品中12种防腐剂和甜味剂

目的建立高效液相色谱法同时测定食品中12种防腐剂和甜味剂的含量。方法样品经甲醇-水(30:70,V:V)提取,经Agilent TC C_(18)色谱柱分离,以甲醇/20 mmol/L乙酸铵水溶液为流动相进行梯度洗脱,流速为1.0mL/min,采用二极管矩阵检测器进行检测,检测波长为230 nm。结果 12种防腐剂和甜味剂在0.2~20μg/mL的浓度范围内呈现良好的线性关系,r~2≥0.9992,回收率在70.9%~115.6%之间,方法的检出限为0.001~0.005 g/kg。结论该方法具有高通量、操作简便等优点,可适用于食品中12种防腐剂和甜味剂的检测。     

甘蔗糖厂压榨阶段有害菌灭菌方法的探索

在制糖过程中,蔗汁中微生物活动是影响白糖产品品质的一个重要因素。为了消除糖厂有害菌对白糖产品品质的影响,本文主要探索了常用食品防腐剂、天然食品防腐剂、其它试剂以及氯化钠水溶液低压直流电解后对甘蔗压榨过程中危害最严重的明串珠菌类微生物的抑菌效果。实验结果表明,对羟基苯甲酸乙酯钠、注射用青霉素钠、乙二胺四乙酸钠（EDTA-2Na）均能有效抑制糖厂生产中主要的有害菌,其最低有效抑菌浓度分别为0.0016、0.0096、0.0056 g/L;氯化钠水溶液在20 V 直流电压电解的抑菌效果与盐浓度的大小以及延迟时间相关,7%左右的盐溶液配合低压电解的抑菌作用最显著。     

海捕虾保鲜效果的比较

目的探索海捕虾保鲜效果好且对人体无害的保鲜剂。方法用焦亚硫酸钠、FMP-虾蟹用天然护色保鲜剂、食为鲜-虾鲜宝、植酸4种保鲜剂采用浸泡法、喷洒法和直接撒粉法3种保鲜方法对海捕虾保鲜的效果进行比较。结果焦亚硫酸钠保鲜海捕虾，用浸泡法、喷洒法和直接撒粉法在7d内均有较好的保鲜效果，但如果操作不当，二氧化硫残留会超标；FMP-虾蟹用天然护色保鲜剂、食为鲜-虾鲜宝保鲜效果较好，而植酸保鲜效果较差。比较后3种保鲜剂的浸泡法和喷洒法，在相同浓度下，浸泡法保鲜效果较好。结论从经济方面考虑，可用焦亚硫酸钠以1．5％浓度浸泡2min保鲜海捕虾，但从人体健康方面考虑，应采用天然护色保鲜剂、食为鲜-虾鲜宝各以2％浓度浸泡2min保鲜海捕虾，保鲜时间控制在7d内保鲜效果较好。     

高效液相色谱法检测4种食品中11种食品添加剂

目的 研究方便、准确并能同时测定多种食品添加剂的的高效液相色谱(High Performance Liquid Chromatography, HPLC)的方法。方法 选择糕点、辣条、饮料、酱油为基质,采用HPLC同时测定食品中11种添加剂,包括糖精钠、苯甲酸、山梨酸、脱氢乙酸、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸异丙酯、对羟基苯甲酸丙酯、对羟基苯甲酸异丁酯、对羟基苯甲酸丁酯、对羟基苯甲酸苄基。结果 该方法中11种食品添加剂线性范围良好,相关系数均大于0.999,糕点、辣条、饮料、酱油中的回收率分别为92.9 %~116.2 %、92.4 %~116.5 %、84.6 %~111.7 %、89.1 %~111.2 %;RSD（%）分别为1.1 %~7.8 %、0.8 %~8.4 %、0.7 %~7.4 %、0.9 %~8.4 %,且每种添加剂的检出限和定量限均低于国家标准,符合检测要求。结论 该方法具有简单、方便、灵敏度高等优点,能够满足多类食品中添加剂检测的需要,为食品添加剂的安全性评估提供了实用的技术手段。     

Determination of nine preservatives in processed foods using a modified QuEChERS extraction and quantified by HPLC-PDA

ABSTRACT

In this study, a new method was developed for simultaneously determining nine preservatives, that is, benzoic acid (BA), sorbic acid (SOA), dehydroacetic acid (DHA) and PHBAs (methyl p-hydroxybenzoate [PHBA-me], ethyl p-hydroxybenzoate [PHBA-et], isopropyl p-hydroxybenzoate [PHBA-ipro], propyl p-hydroxybenzoate [PHBA-npro]), isobutyl p-hydroxybenzoate [PHBA-ibut] and butyl p-hydroxybenzoate [PHBA-nbut]), in processed foods, employing liquid chromatography (LC). This procedure accelerated sample preparation and improved efficiency by employing modified quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction without clean-up. Samples were prepared with 20 mL of acetonitrile/water (1:1) with the assistance of a ceramic stone. The extract solutions were diluted 10 times or according to the detection amount and then injected into an LC-PDA. This method showed good linearity, and the LOQs were 10 mg/kg for BA, SOA and DHA and 5?mg/kg for the PHBAs. When validating this method, the recoveries of the nine preservatives were in the range 77.0–99.6%, RSD_r values were in the range 0.7–5.3% and those of RSD_wr were in the range 2.3–8.4%. These results suggest that this new method is highly reproducible.     

食品防腐剂及其分析技术新编

随着食品种类以及防腐剂品种的增加,使用范围扩大,我国准许使用的防腐剂种类已经由GB2760-1996中28个品种增加到2003年的36个品种;在GB2760-1996已制定的食品防腐剂标准检验方法包括:食品中山梨酸、苯甲酸、丙酸钠、丙酸钙、脱氢乙酸、对羟基苯甲酸酯类、水果中乙氧基喹残留量等几种测定方法。近年来食品中防腐剂的测定,特别是多组分同时测定方法发展很快,多半采用HPLC法。上述国家标准检验方法已不能完全满足当前检验工作的需要。本文重点介绍饱和硫酸铵蒸馏法食品中苯甲酸、山梨酸、脱氢乙酸、对羟基苯甲酸酯类等九种防腐剂同时测定法、柑橘类残留噻苯咪唑等五种防腐剂测定方法和HPLC法沙拉酱及干酪中纳他霉素含量测定方法。     

Chitosan coatings enriched with essential oils: Effects on fungi involved in fruit decay and mechanisms of action

BackgroundPesticides have a negative impact on the health of consumers and on the environment, and as a consequence, the use of naturally occurring antimicrobial agents have become more popular to prevent food spoilage. An alternative is the use of chitosan, because of its antimicrobial, antioxidant activities and its capacity to form films having good mechanical properties. Chitosan has been used in the preparation of films and coatings for the preservation of different food products, and the addition of essential oils have been shown to be a good strategy to improve its antimicrobial activity in situ.Scope and approachThis review compiles information related to studies and research that employ chitosan as matrix for films, coatings and nanogels with essential oils extracted from plants, as antifungal agent. A special emphasis has been addressed to the effect exerted on the most pathogenic fungi for crops, also highlighting the mechanisms of action that researchers attribute to the composite, together with inhibition data.Key Findings and ConclusionEffective natural treatments, using chitosan-essential oils films or nano-emulsions, improve the preservation of fruit in terms of fungal decay. The effect is particularly dependent on the ability to release the antimicrobial compounds from the polymer matrix, the type of essential oils, the fungal species, and the incubation temperature. Several efforts are still required to understand in detail the mechanism of degradation of perishable food, how the chitosan-essential oils composites control or inhibit food decay, the effects on other pathogenic and non-pathogenic moulds as well as on the production of mycotoxins.