Osmotic dehydration of apple slices with CaCl2 and sucrose limits decay caused by Penicillium expansum, Colletotrichum acutatum, and Botrytis cinerea and does not promote Listeria monocytogenes or total aerobic population growth.

The interaction of Penicillium expansum Link, Colletotrichum acutatum, and Botrytis cinerea Pers.:Fr. with Listeria monocytogenes on osmotically dehydrated apple slices was evaluated. In mineral analyses of the slices, the calcium content of the peel and flesh tissues increased by 4- and 11-fold, respectively, when processed in 2% CaCl2. These slices also exhibited less decay by P. expansum, C. acutatum, and B. cinerea. Inoculation of slices with P. expansum resulted in a decrease in the pH of the flesh tissue at the infection site, while the pHs of slices infected with C. acutatum and B. cinerea increased and remained stable, respectively. Total mold population increased in wounds inoculated with P. expansum or C. acutatum. The presence of L. monocytogenes in the wounds did not significantly affect mold growth. The association of P. expansum and L. monocytogenes on apple slices resulted in a decrease in the bacterial population, whereas L. monocytogenes survived when slices were inoculated with C. acutatum. When associated with B. cinerea, there was a fourfold decrease in the L. monocytogenes population when slices were treated with 2% CaCl2. The total aerobic population was not significantly affected by the type of microorganism added to the wounds or by the osmotic treatment. These data show that osmotic dehydration with 2% CaCl2 combined with 20% sucrose limits decay of apple slices and does not promote bacterial or total aerobic population growth.

Degradation of Ochratoxin A by Acinetobacter calcoaceticus.

Microorganisms were screened for their ability to degrade ochratoxin A (OTA). Among test microorganisms, Acinetobacter calcoaceticus was found to degrade OTA. The degradation of OTA by A. calcoaceticus was studied in an ethanol-minimal salts medium with an initial OTA concentration of 10 (µg/ml at 25 and 30°C. Under these conditions, A. calcoaceticus was able to degrade OTA with an initial concentration of OTA of 10 (µg/ml. The average amounts of OTA removed by A. calcoaceticus in medium with an initial OTA concentration of 10 (µg/ml were 0.1005 and 0.0636 (µg/ml/h at 25 and 30°C, respectively. Ochratoxin A was degraded significantly by A. calcoaceticus during and after the log phase of cell growth at both incubation temperatures. It is postulated that degradation of OTA by A. calcoaceticus yielded a less toxic ochratoxin α.

Survival of Campylobacter jejuni in Modified Atmosphere Packaged Turkey Roll.

Survival of Campylobacter jejuni , inoculated into turkey roll slices and stored under seven different atmospheric mixtures, was determined. Turkey roll samples were stored at 4°C for 18 d and at 21°C for 48 h. The effects of various atmospheric mixtures on aerobic, psychrotrophic, and lactic acid bacterial populations were also determined throughout storage. Campylobacter jejuni was inactivated under all atmospheric gas mixtures tested throughout storage. Increasing CO2 concentration inside the package from 0% to 100% CO2 resulted in a lower rate of inactivation of C. jejuni at both storage temperatures. Increases in CO2 concentrations provided greater inhibition of aerobic and psychrotrophic populations as compared to low CO2 levels. The effect of CO2 on survival of C. jejuni and growth rate of aerobic, psychrotrophic, and lactic acid bacteria was more pronounced at 4°C. Campylobacter s were isolated from inoculated turkey roll held under all atmospheres by enrichment procedures on the 18th day and 48th hour of storage at 4 and 21°C, respectively, with an initial population of log 6.0 Campylobacter s/g. However, no Campylobacter s were isolated by 18 d of storage at 4°C by direct plating.

Infection of Shell Eggs With Yersinia Enterocolitica.

Shell eggs were immersed in bacterial suspensions containing 106 Yersinia enterocolitica /ml and subjected to either a temperature differential or a pressure differential inoculation technique in the presence or absence of 20 ppm iron to determine if Y. enterocolitica could penetrate and infect shell eggs. No Y. enterocolitica was detected inside eggs immediately after inoculation. After 3 d of storage at 10°C, Y. enterocolitica was detected in only one egg out of 24. After 7 d of storage at 10°C, approximately 14% of eggs from bacterial suspensions with no iron supplementation contained Y. enterocolitica . After 14 d, Yersinia counts exceeded log 6.0 CFU/ml and Yersinia were found inside 100% of eggs examined.

Campylobacter jejuni in Vacuum Packaged Processed Turkey.

This study evaluated the effect of vacuum packaged storage at 4°C upon survival of Campylobacter jejuni in processed turkey roll and turkey ham. Turkey ham and turkey roll samples were sliced, inoculated with C. jejuni , vacuum packaged, and stored at 4°C for up to 28 d. Three different strains of C. jejuni were evaluated. After appropriate incubation, the inoculated samples were analyzed for culturable C. jejuni . Control samples were analyzed for aerobic plate count and enterococci. Culturable C. jejuni decreased significantly during vacuum packaged storage at 4°C over time (P<0.05). A significant difference in viability existed between the three test strains used (P<0.05). Higher levels of C. jejuni were detected in the turkey roll than the turkey ham. Aerobic plate counts and enterococci increased significantly during storage (P<0.05) providing competition for C. jejuni . Though survival of C. jejuni decreased over time, greater than 500 viable cells per gram were detected with some strains for up to 28 d.

Growth Characteristics of Yersinia enterocolitica in Pasteurized Skim Milk.

Experiments were undertaken to determine the growth characteristics of five strains of Yersinia enterocolitica in pasteurized milk at 4°C. Pasteurized milk was inoculated with approximately 10 or 1000 cells/ml of Y. enterocolitica , and was incubated at 4°C for 0, 3, 7, 14 and 21 d. Each sample was spread-plated in duplicate on Tryptone Soya Agar, MacConkey Agar and Cefsulodin-Irgasan-Novobiocin (CIN) agar. Plates were incubated at 25°C for 48 h or at 32°C for 24 h and enumerated for total and Yersinia plate count. All five strains of Y. enterocolitica competed very well with background microflora of pasteurized milk and reached levels of log 5.0 to 7.0/ml after 7 d at 4°C. Level of inoculation had little or no effect on the total number of Y. enterocolitica after 14 or 21 d in pasteurized milk at 4°C. Generation times at 4°C were highly strain-dependent.

Chemical and Biological Evaluation of Aflatoxin After Treatment with Sodium Hypochlorite, Sodium Hydroxide and Ammonium Hydroxide.

Aflatoxin B1 was mixed with eleven concentrations of sodium hydroxide, sodium hypochlorite and ammonium hydroxide. Aflatoxin was quantitated by fluorometric determination and toxicity of aflatoxin treated with NaOH and NH4OH was evaluated by the brine shrimp assay. Detoxified aflatoxin B1 was then screened for mutagenicity using the Salmonella /mammalian microsome mutagenicity test (Ames test). Sodium hydroxide, sodium hypochlorite and ammonium hydroxide reduced fluorescence by 92, 96, and 94%, respectively, at concentrations of 25, 11, and 875 mg per 50 g. A high negative correlation was observed between decrease in fluorescence and increase in survival of brine shrimp (r = 0.88) for aflatoxin treated with NaOH and NH4OH. Equivalent amounts of aflatoxin B1 (0.05 µg) and aflatoxin B1+ detoxified B1 (0.05 µg + 0.05 µg, respectively) were not significantly different (P>0.05) in the number of revertants resulting in the Ames test. Therefore, aflatoxin B1 in the presence of detoxified aflatoxin did not increase in mutagenicity.

Inhibition of Patulin Production with the Insecticide Naled.

Patulin is a wide spectrum biocide produced by several species of Aspergillus , Penicillium and Byssochlamys , and is a potentially important mycotoxin that may be ingested by man. The effect of the insecticide naled on fungal growth and patulin production was evaluated using three concentrations (1, 10, and 100 mg/l, ppm) and several application times both before inoculation and during growth of the fungus. If added before inoculation, naled at 100 mg/l completely inhibited mycelial growth of Penicillium urticae for 15 days and patulin production for 30 days. When the concentration was decreased to 10 mg/l, and the insecticide added at the time of inoculation, patulin production was inhibited by 59%. If 100 mg of naled/1 was added between 3 and 6 days after fungal growth was visible, patulin production was inhibited by more than 50%. If the insecticide was added at this same concentration to cultures older than 6 days, patulin production was inhibited by 25-35%. Production of patulin in apples was inhibited by 76% and tissue damage inhibited by 43% when 100 mg of naled/1 was applied to apples before their inoculation and storage at 25 C. Naled was highly effective in inhibiting patulin production and showed long-term activity. However, naled completely inhibited patulin production only when applied before growth of the fungus.