EFFECT OF GLYCERYL MONOLAURATE ON TOXIN PRODUCTION BY CLOSTRIDIUM BOTULINUM IN MEAT SLURRY

Glyceryl monolaurate when used in the proportion of 5 g per kg of meat slurry (pH 6.0–6.2) inhibited toxin production by Clostridium botulinum type A (strain 73A), type B (strain OKRA) and type E (strain RIV 2). The concentration of glycerol monolaurate required for inhibition was not reduced by addition of lactic acid to the meat slurry until the pH was lowered to pH 5.2 or below. In meat slurry (pH 6.0–6.2), potassium sorbate inhibited production of type B toxin at 32 g/kg. The addition of butylated hydroxy-anisole to glyceryl monolaurate had no effect upon the concentration needed for inhibition of botulinum toxin production.     

INHIBITION OF ASPERGILLUS PARASITICUS GROWTH AND TOXIN PRODUCTION BY GARLIC

Mycelial growth and toxin production by Asperigillus parasiticus were inhibited by garlic concentrations of 0.3–0.4%. When the fungus was grown in broth, aflatoxin B₁ production was inhibited at a garlic concentration of 0.3% while aflatoxin G₁ production was inhibited by 0.25% garlic. When growth on rice, aflatoxin B₁ was detected at garlic concentrations of up to 2.5%. Aflatoxin G₁ was detected at 1.25% garlic concentration but not above this level.     

乳酸片球菌细菌素的活性及特性的研究

试验采用TGE（trypticase glucose yeast extlact）肉汤培养基作为乳酸片球菌的培养基，培养条件为37℃过夜静止培养。利用改变pH的方法，即通过菌体对细菌素的吸附与解吸，对细菌素进行分离纯化，试验表明细菌素对植物乳杆菌，绿脓杆菌，单核细胞增多症李氏杆菌，沙门氏菌，枯草杆菌，金黄色葡萄球菌和大肠杆菌O157均有抑制作用。并且还具有耐热，耐盐的特性．     

EFFECT OF ETHANOL VAPOR ON GROWTH AND TOXIN PRODUCTION BY CLOSTRIDIUM BOTULINUM IN A HIGH MOISTURE BAKERY PRODUCT

To determine the effect of ethanol vapor on toxin production by Clostridium botulinum, studies were done in English style crumpets (a_w 0.990, pH 6.5) challenged with 500 spores/g C. botulinum types A and proteolytic B and packaged in high gas barrier bags [ethanol transmission rate (ETR) 0.21 g/m²/day @ 25 C]. Crumpets were packaged in air with either commercially available ethanol vapor generators (Ethicap® 2, 4 or 6G) or cotton wool pads saturated with 2, 4 or 6 g of 95% food grade ethanol and stored at 25C. Toxin was detected in all inoculated control crumpets (0% ethanol) after 5 days at ambient temperature (25C). Ethicap® 2G delayed toxicity for 10 days while complete inhibition (>21 days) was observed in all crumpets packaged with 4 or 6G Ethicap® or with 2, 4 or 6 g of ethanol per pad. However, all crumpets were overtly spoiled by this time. Both headspace ethanol and absorption of ethanol by crumpets increased as a function of Ethicap® size/weight of ethanol. Based on these preliminary studies, ethanol vapor would appear to be an effective additional barrier to control the growth and toxin production by C. botulinum in high moisture bakery products and ensure the safety of these products at ambient temperature.     

METABIOTIC GROWTH OF AND TOXIN FORMATION BY CLOSTRIDIUM BOTULINUM

Strains of Clostridium botulinum types A, B and F were grown aerobically in metabiotic association with several aerobic and facultative microorganisms. In unbuffered media Enterococcus faecalis and Pediococcus cerevisiae produced enough acid to prevent toxin formation by C. botulinum but in buffered media toxin was formed. Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Yersinia enterocolitica, strains of Serratia, Pseudomonas, Alcaligenes and 35 unidentified strains from mechanically deboned chicken homogenate produced conditions favorable for toxin production under aerobic conditions. The metabiotes did not inhibit spore formation nor did toxin production correlate with the appearance of spores .     

POTENTIAL CLOSTRIDIUM BOTULINUM HAZARDS ASSOCIATED WITH EXTENDED SHELF-LIFE REFRIGERATED FOODS: A REVIEW

Clostridium botulinum may pose a hazard in extended shelf-life refrigerated foods. Nonproteolytic strains ofC. botulinum, which can grow at refrigeration temperatures, may be given sufficient time to grow if the shelf-life is extensive. Proteolytic strains may grow in these products if temperature abuse occurs. Mild heat treatments and vacuum or modified atmosphere packaging may select for C. botulinum and allow toxicity to occur in organoleptically acceptable products. Multiple barriers and multifactorial experiments to generate predictive models are advocated to ensure safety of extended shelf-life refrigerated foods.     

EFFECT OF FILMS OF DIFFERENT OXYGEN TRANSMISSION RATE ON TOXIN PRODUCTION BY CLOSTRIDIUM BOTULINUM TYPE E IN VACUUM PACKAGED COLD AND HOT SMOKED TROUT FILLETS

Studies were done to determine the effect of film oxygen transmission rate (OTR) on the time to toxicity in vacuum packaged cold and hot smoked rainbow trout fillets challenged with C. botulinum type E (10² spores/g) and stored at refrigerated conditions (4C), and under mild (8C) and moderate (12C) temperature abuse conditions. While no samples were toxic at 4C, toxin was detected within 28 days at 8C for cold smoked trout fillets vacuum packaged in films with high OTR. Toxin was also detected for most vacuum packaged hot smoked trout fillets within 14–28 days at 8C, with the exception of trout fillets packaged in films with an OTR > 10,000 cc/m²/day. In most cases at 8C, spoilage, based on odor/color scores, preceded or occurred simultaneously with toxigenesis. At 12C all cold and hot smoked trout were toxic after 14–21 days and samples packaged in films with an OTR <5000 cc/m²/day became toxic before, or at the same time as, samples became spoiled. This study has shown that vacuum packaging of trout fillets in low gas barrier films, ranging in OTR from approximately 3,000 to approximately 10,000 cc/m²/day at 24C and 0% relative humidity (RH), did not prevent the growth and toxin production by C. botulinum in vacuum packaged cold and hot smoked trout fillets at 12C. Additional barriers, other than the OTR of the packaging film, need to be considered to ensure the safety of vacuum packaged trout fillets, particularly at mild to moderate temperature abuse storage conditions.     

EFFECT OF HEADSPACE OXYGEN AND FILMS OF DIFFERENT OXYGEN TRANSMISSION RATE ON TOXIN PRODUCTION BY CLOSTRIDIUM BOTULINUM TYPE E IN RAINBOW TROUT FILLETS STORED UNDER MODIFIED ATMOSPHERES

Studies were conducted to determine the effect of various levels of headspace oxygen (0–100%, balance CO₂) or film oxygen transmission rate (OTR) on the time to toxicity in modified atmosphere packaged (MAP) fresh trout fillets challenged with C. botulinum type E (10² spore/g) and stored under moderate temperature abuse conditions (12C). In all cases, trout were toxic within 5 days, irrespective of the initial levels of oxygen in the package headspace. However, spoilage preceded toxigenesis. Packaging of trout fillets in low gas barrier films, with OTRs ranging from 4,000 to 10,000 cc/m²/day at 24C and 0% relative humidity, also had no effect on time to toxicity in all MAP trout fillets. All fillets were toxic within 4–5 days and spoilage again preceded toxigenesis. This study has shown that the addition of headspace O₂, either directly to a package or indirectly by using a low gas barrier film, had no influence on the time to toxigenesis or spoilage. Additional barriers, other than headspace O₂ or film transmission rate, need to be considered to ensure the safety of MAP trout fillets, particularty at moderate temperature abuse conditions.