John J. Churey

Efficacy of UV light for the reduction of Listeria monocytogenes in goat's milk.

Certain types of goats cheeses are produced using unpasteurized milk, which increases the food safety concerns for these types of products. Popularity and consumption of goats milk products have increased, and the niche market includes gourmet goats cheeses. The U.S. Code of Federal Regulations and the Pasteurized Milk Ordinance both address the possibility for processing alternatives to heat treatment, and the use of UV light treatment may be a viable alternative that still ensures the safety of the product. Fresh goats milk was inoculated with Listeria monocytogenes (L-2289) at 10(7) CFU/ml and exposed to UV light using the CiderSure 3500 apparatus (FPE Inc., Macedon, NY). Inoculated milk was exposed to a UV dose range between 0 and 20 mJ/cm2 to determine the optimal UV dose. A greater than 5-log reduction was achieved (P < 0.0001) when the milk received a cumulative UV dose of 15.8 +/- 1.6 mJ/cm2. The results of this study indicate that UV irradiation could be used for the reduction of L. monocytogenes in goats milk.

Influence of Apple Cultivars on Inactivation of Different Strains of Escherichia coli O157:H7 in Apple Cider by UV Irradiation

ABSTRACT This study examined the effect of different apple cultivars upon the UV inactivation of Escherichia coli O157:H7 strains within unfiltered apple cider. Apple cider was prepared from eight different apple cultivars, inoculated with approximately 106 to 107 CFU of three strains of E. coli O157:H7 per ml (933, ATCC 43889, and ATCC 43895), and exposed to 14 mJ of UV irradiation per cm2. Bacterial populations for treated and untreated samples were then enumerated by using nonselective media. E. coli O157:H7 ATCC 43889 showed the most sensitivity to this disinfection process with an average 6.63-log reduction compared to an average log reduction of 5.93 for both strains 933 and ATCC 43895. The highest log reduction seen, 7.19, occurred for strain ATCC 43889 in Rome cider. The same cider produced the lowest log reductions: 5.33 and 5.25 for strains 933 and ATCC 43895, respectively. Among the apple cultivars, an average log reduction range of 5.78 (Red Delicious) to 6.74 (Empire) was observed, with two statistically significant (α ≤ 0.05) log reduction groups represented. Within the paired cultivar-strain analysis, five of eight ciders showed statistically significant (α ≤ 0.05) differences in at least two of the E. coli strains used. Comparison of log reductions among the E. coli strains to the cider parameters of °Brix, pH, and malic acid content failed to show any statistically significant relationship (R2 ≥ 0.95). However, the results of this study indicate that regardless of the apple cultivar used, a minimum 5-log reduction is achieved for all of the strains of E. coli O157:H7 tested.

Modeling of Escherichia coli Inactivation by UV Irradiation at Different pH Values in Apple Cider

This study examined the effects and interactions of UV light dose (1,800 to 20,331 microJ/cm2) and apple cider pH (2.99 to 4.41) on the inactivation of Escherichia coli ATCC 25922, a surrogate for E. coli O157:H7. A predictive model was developed to relate the log reduction factor of E. coli ATCC 25922 to the UV dose. Bacterial populations for treated and untreated samples were enumerated with the use of nonselective media. The results revealed that UV dose was highly significant in the inactivation of E. coli, whereas pH showed no significant effect at higher UV doses. Doses of 6,500 microJ/cm2 or more were sufficient to achieve a greater than 5-log reduction of E. coli. Experimental inactivation data were fitted adequately by a logistic regression model. UV irradiation is an attractive alternative to conventional methods for reducing bacteria in unpasteurized apple cider.

Inactivation of Cryptosporidium parvum oocysts in fresh apple cider by UV irradiation.

ABSTRACT This study evaluated the efficacy of UV irradiation on the inactivation of Cryptosporidium parvum oocysts in fresh apple cider. Cider was inoculated with oocysts and exposed to 14.32 mJ of UV irradiation/cm2. Oocyst viability was assessed with the gamma interferon gene knockout (GKO) mouse and infant BALB/cByJ mouse models. All GKO mice challenged with UV-treated cider demonstrated no morbidity or mortality, and infant BALB/c mice challenged with treated cider were negative for the presence of C. parvum. In contrast, the GKO mice challenged with non-UV-treated inoculated cider died and the parasite was detected in the ileums of all challenged infant mice. This study shows that UV irradiation can be used to inactivate C. parvum in fresh apple cider.

Analysis and modeling of the variability associated with UV inactivation of Escherichia coli in apple cider

Raw data from validation studies of UV tubes used for nonthermal pathogen reduction in apple cider underwent comprehensive statistical analysis. Data from each tube that demonstrated at least a 5-log reduction of Escherichia coli ATCC 25922, a surrogate for E. coli O157:H7, in each of three trials were used in the analysis. The within- and between-tube variability was calculated for 70 tubes. The mean log reductions of the tubes fit a Beta distribution (Kolmogorov-Smirnov test, 0.0246), and the between-replicate variability followed a logistic distribution (Kolmogorov-Smirnov test, 0.0305). These two distributions can be used together to model UV cider treatment as part of an overall E. coli O157:H7 in cider risk assessment. Examples of codes from @RISK and Analyticato describe these distributions, such as one would find in a quantitative risk assessment, are included.

Antimicrobial activity of bacterial isolates from different floral sources of honey

More than two thousand bacterial strains isolated from six US domestic honeys and two manuka honeys from New Zealand were screened for production of antimicrobial compounds. A high incidence of antimicrobial inhibition determined by deferred inhibition assays was observed with the bacterial isolates from all eight honey samples. In total, 2217 isolates out of 2398 strains (92.5% of total isolates) exhibited antimicrobial activity against at least one of the tested microorganisms. Antifungal activity by bacterial isolates originating from the eight honeys ranged from 44.4% to 98.0%. Bacterial isolates from manuka honey (MH1) exhibited antimicrobial activity against Bacillus subtilis ATCC 6633 and Bacillus cereus F4552, at 51.5% and 53.3% of the isolates, respectively. However, less than 30% of the bacterial isolates from the other manuka honey (MH2) and six domestic honey sources exhibited anti-Bacillus activity. Listeria monocytogenes F2-586 1053 showed higher overall rates of sensitivity to between 11 and 66% of the bacterial isolates. The high rate of antimicrobial activity exhibited by the bacterial strains isolated from different honey sources could provide potential sources of novel antimicrobial compounds.

Biosynthesis and transcriptional analysis of thurincin H, a tandem repeated bacteriocin genetic locus, produced by Bacillus thuringiensis SF361

Thurincin H, a bacteriocin produced by Bacillus thuringiensis SF361 isolated from honey, strongly inhibited the growth of Bacillus cereus F4552. The bacteriocin was purified by 65% ammonium sulfate precipitation of the culture supernatant, followed by octyl-sepharose CL-4B and reverse-phase HPLC. The molecular mass of the bacteriocin was determined to be 3139.51 Da and the 14 amino acids of the bacteriocin at the N-terminus were identified. The complete amino acid sequence of mature thurincin H was deduced from three structural genes, thnA1, thnA2, and thnA3 found in tandem repeats on the chromosome, all of which encode for the same bacteriocin, thurincin H. The genetic determinants for thurincin H biosynthesis consist of 10 ORFs, including three thurincin H structural genes. Northern hybridization elucidated that the transcription of all three bacteriocin structural genes was regulated by a putative promoter located upstream of thnA1.

Heat Treatments To Enhance the Safety of Mung Bean Seeds

Salmonella enterica serovars and Escherichia coli O157:H7 have been associated with contaminated seed sprout outbreaks. The majority of these outbreaks have been traced to sprout seeds contaminated with low levels of pathogens. E. coli O157:H7 strains can grow an average of 2.3 log CFU/g over 2 days during seed germination, and Salmonella can achieve an average growth of 3.7 log CFU/g. Therefore, it is important to find an effective method to reduce possible pathogenic bacterial populations on the seeds prior to sprouting. Our objective was to assess the effectiveness of various dry heat treatments on reducing E. coli O157:H7 and Salmonella populations on mung beans intended for sprout production and to determine the effect of these treatments on seed germination. Mung beans were inoculated with five-strain cocktails of E. coli O157:H7 and of Salmonella serovars harboring the green fluorescent protein gene and then air dried overnight. Heat treatments were performed by incubating the seeds at 55 degrees C for various periods of time. Heat-treated seeds were then assessed for the efficacy of the heat treatment and the effects of heat treatment on germination rates. After inoculation and drying, 6 log CFU/g E. coli O157:H7 and 4 log CFU/g Salmonella were detected on the seeds. Following heat treatment, pathogenic bacterial populations on the seeds were below detectable levels (<1 log CFU/g), but the germination rate of the seed was not affected. Thus, the risk of contamination and the presence of pathogens in the finished sprouts were greatly reduced via the seed heat treatment process.

Thermal inactivation of Salmonella and Escherichia coli O157:H7 on alfalfa seeds

Alfalfa seeds inoculated with five strains of Salmonella or Escherichia coli O157:H7 were subjected to dry heat at 55 degrees C for up to 8 days. Five-log reductions in Salmonella or E. coli O157:H7 on seeds were observed. No pathogens were detected on the sprouted seeds, which were initially inoculated with ca. 2 log CFU/g of Salmonella or more than 8 log CFU/g of E. coli O157:H7. The percentages of germination of the alfalfa seeds did not significantly decrease after 6 days of heating at 55 degrees C. These results showed that heat treatment of alfalfa seeds at 55 degrees C for up to 6 days was effective in enhancing the safety of alfalfa sprouts without affecting germination significantly.

Reduction of Patulin in Apple Cider by UV Radiation

The presence of the mycotoxin patulin in processed apple juice and cider presents a continual challenge to the food industry as both consumer health and product quality issues. Although several methods for control and/or elimination of patulin have been proposed, no unifying method has been commercially successful for reducing patulin burdens while maintaining product quality. In the present study, exposure to germicidal UV radiation was evaluated as a possible commercially viable alternative for the reduction and possible elimination of the patulin mycotoxin in fresh apple cider. UV exposure of 14.2 to 99.4 mJ/cm(2) resulted in a significant and nearly linear decrease in patulin levels while producing no quantifiable changes in the chemical composition (i.e., pH, Brix, and total acids) or organoleptic properties of the cider. For the range of UV doses tested, patulin levels decreased by 9.4 to 43.4%; the greatest reduction was achieved after less than 15 s of UV exposure. The method of UV radiation (the CiderSure 3500 system) is an easily implemented, high-throughput, and cost-effective method that offers simultaneous UV pasteurization of cider and juice products and reduction and/or elimination of patulin without unwanted alterations in the final product.