Progress 12/15/01 to 12/31/04
Outputs
In response to increasing concerns about microbial safety of apple cider, the FDA has mandated treatment of cider sufficient for a 5-log reduction of the target pathogen. Pasteurization has been suggested as the treatment most likely to achieve a 5-log reduction, with Escherichia coli O157:H7 as the target pathogen. Regulators and processors have need for a method to verify pasteurization, and apple cider polyphenol oxidase (PPO) activity was studied as a potential intrinsic index for thermal pasteurization. The effect of pasteurization conditions and apple cider properties on PPO activity and survival of 3 pathogens (E. coli O157:H7, Salmonella spp., and Listeria monocytogenes) was studied using a Box-Behnken response surface design. Factors considered in the design were pasteurization conditions: hold temperature (60, 68, 76 degrees C), preheat time (10, 20, 30 s), and hold time (0, 15, 30 s), as well as pH and sugar content (degrees Brix) of apple cider. Response
surface contour plots were constructed to illustrate the effect of these factors on PPO activity and pathogen survival. Reduction in PPO activity of at least 50% was equivalent to a 5-log reduction in E. coli O157:H7 or L. monocytogenes for cider at pH 3.7 and 12.5 Brix. Further studies, however, are needed to verify the relationship between PPO activity and pathogen reduction in cider with varying pH and degrees Brix. Regulators are increasingly concerned about patulin, a potent carcinogen, in apple juice products. As a result of a local outbreak, we initially evaluated the effect of the heating regimes that we had established for PPO inactivation in destroying this toxin. Due to the complexity inherent in evaluating the toxicity of patulin-breakdown products, we refocused our efforts in an attempt to evaluate the effectiveness of several chemical sanitizers against Penicillium expansum, the mold responsible for toxin production. We also wished to establish sanitizing wash treatments
which would inhibit P. expansum growth and subsequent patulin production on Empire apples destined for cider. Wash treatments included: 200 ppm NaOCl, 1% StorOx, 0.5% potassium sorbate, 300 ppm SO2, and 0-5% acetic acid. Spores of P. expansum or inoculated apple slices were dipped in sanitizing wash solution for 5 min, and mold growth and patulin production was monitored on subsequent storage. It was found that 0.5% potassium sorbate and 300 ppm SO2 did not affect mold survival or patulin production; 1% StorOx was effective against mold spores in solution (4 log MPN destruction of spores), but there was no significant reduction in spore count when the same solution was used to sanitize mold-inoculated apple discs. Washing with 200 ppm NaOCl delayed growth of P. expansum on inoculated apple discs, but failed to completely inhibit patulin production. Acetic acid solution (2-5%) was the most efficient chemical against P. expansum. A wash treatment with >2 % acetic acid for more than 1
min is recommended to completely inhibit growth of P. expansum and subsequent patulin production on apples destined for cider.
Impacts
Polyphenol oxidase, PPO, may be an intrinsic marker for adequate heat pasteurization that can be adopted by the apple cider and juice processing industries. Furthermore, in an attempt to eliminate patulin, a known carcinogen, from contaminating apple cider, processors should wash apples with at least 2% acetic acid for at least one minute to inhibit growth of Penicillium expansum and subsequent patulin production on apples destined for cider.
Publications
- Chen, L., B.H. Ingham, and S.C. Ingham. 2004. Polyphenol oxidase (PPO) activity as a potential intrinsic index of adequate thermal pasteurization of apple cider. J. Food Protection. 67:908-914.
- Chen, L., B.H. Ingham and S.C. Ingham. 2004. Survival of Penicillium expansum and patulin production on stored apples following wash treatments. J. Food Sci. October 2004 C669-75.
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Progress 01/01/03 to 12/31/03
Outputs
In response to increasing concerns about microbial safety of apple cider, the FDA has mandated treatment of cider sufficient for a 5-log reduction of the target pathogen. Pasteurization has been suggested as the treatment most likely to achieve a 5-log reduction, with Escherichia coli O157:H7 as the target pathogen. Regulators and processors have need for a method to verify pasteurization, and apple cider polyphenol oxidase (PPO) activity was studied as a potential intrinsic index for thermal pasteurization. The effect of pasteurization conditions and apple cider properties on PPO activity and survival of 3 pathogens (E. coli O157:H7, Salmonella spp., and Listeria monocytogenes) was studied using a Box-Behnken response surface design. Factors considered in the design were pasteurization conditions: hold temperature (60, 68, or 76 degrees C), preheat time (10, 20, or 30 seconds), and hold time (0, 15, or 30 seconds), as well as pH and sugar content (degrees Brix) of
apple cider. Response surface contour plots were constructed to illustrate the effect of these factors on PPO activity and pathogen survival. Reduction in PPO activity of at least 50 percent was equivalent to a 5-log reduction in E. coli O157:H7 or L. monocytogenes for cider at pH 3.7 and 12.5 degrees Brix. Further studies, however, are needed to verify the relationship between PPO activity and pathogen reduction in cider with varying pH and degrees Brix.
Impacts
Polyphenol oxidase, PPO, may be an intrinsic marker for adequate heat pasteurization that can be adopted by the apple cider and juice processing industries.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Microbial safety of fresh apple cider has become increasingly important due to several recent outbreaks of food borne illness caused by Escherichia coli O157:H7. The US Food and Drug Administration (FDA), in response to the outbreaks, requires that apple cider be treated to ensure a 5-log reduction in the target microorganism, or that the product carry a warning label. Thermal pasteurization has been proven to be an effective option for eliminating pathogens in apple cider. Currently no rapid method exists to verify adequate thermal processing. Since enzymes have been successfully used as chemical "markers" to evaluate thermal treatment in other products, we hypothesize that polyphenol oxidase (PPO) may be employed as a potential intrinsic index for thermal pasteurization validation in apple cider. Our objective is to determine if the thermal inactivation of apple PPO quantitatively reflects the thermal reduction of pathogens during pasteurization. A lab protocol has
been set up and conducted to imitate industrial scale apple cider pasteurization. Thermal kinetics of crude PPO in apple cider at various pH values and with different substrates were evaluated spectrophotometrically and compared with the thermal destruction of pathogens: Escherichia coli O157:H7, Salmonella spp. and Listeria monocytogenes. The results showed that pasteurization at 68.1 degrees C with 14sec of hold time achieved greater than 5 log reduction in pathogens (log CFU/ml): Escherichia coli O157:H7; Salmonella spp.; and Listeria monocytogenes. Meanwhile, inactivation of PPO activity was proportional to hold time under the same thermal treatment. PPO lost 77.8-83.6 percent of its original activity with 14sec hold time at 68.1 degrees C, using 4-methylcatechol or catechol as substrates. With chlorogenic acid as the substrate, PPO activity was relatively stable at 68.1 degrees C.
Impacts
These results suggest that apple PPO activity may be able to serve as an intrinsic index for thermal pasteurization in apple cider.
Publications
- No publications reported this period
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