Application of ultraviolet-C light on oranges for the inactivation of postharvest wound pathogens

Germicidal effects of ultraviolet-C (UV-C) light on the postharvest wound pathogens of citrus fruits namely Penicillium digitatum and Penicillium italicum were investigated. P.digitatum and P.italicum spores were inoculated (4.00-4.50 log cfu/orange) onto Washington navel oranges (Citrus sinensis L. Osbeck cv Washington navel) by using wound and spot inoculation methods and subjected to eight different UV-C doses in the range of 0.26-15.84kJ/m2. Maximum reductions of 2.75 and 3.33 log cfu/orange of P.digitatum were obtained at the UV-C dose of 3.17kJ/m2 for spot and wound inoculation methods, respectively. P.italicum was more resistant than P.digitatum to UV-C treatments. The results suggest that UV-C treatments designed to reduce P.italicum spores will provide an adequate degree of protection against P.digitatum spores. UV-C light could be an alternative technique for the use of synthetic chemicals to reduce the development of postharvest pathogens of oranges. © 2015 Elsevier Ltd.2010 MUH 056The financial supports of Ege University Research Foundation (Project no: 2010 MUH 056 ) are gratefully acknowledged. -

Control of Clostridium perfringens germination and outgrowth by buffered sodium citrate during chilling of roast beef and injected pork

Inhibition of the germination and outgrowth of Clostridium perfringens by buffered sodium citrate (Ional) and buffered sodium citrate supplemented with sodium diacetate (Ional Plus) during the abusive chilling of roast beef and injected pork was evaluated. Beef top rounds or pork loins were injected with a brine containing NaCl, potato starch, and potassium tetrapyrophosphate to yield final in-product concentrations of 0.85, 0.25, and 0.20%, respectively. Products were ground and mixed with Ional or Ional Plus at 0, 0.5, 1.0, and 2.0%. Each product was mixed with a three-strain C. perfringens spore cocktail to obtain final spore concentrations of ca. 2.5 log10 spores per g. Chilling of roast beef from 54.4 to 7.2°C resulted in C. perfringens population increases of 1.51 and 5.27 log10 CFU/g for 18- and 21-h exponential chill rates, respectively, while chilling of injected pork resulted in increases of 3.70 and 4.41 log10 CFU/g. The incorporation of Ional into the roast beef formulation resulted in C. perfringens population reductions of 0.98, 1.87, and 2.47 log10 CFU/g with 0.5, 1.0, and 2.0% Ional, respectively, over 18 h of chilling, while 1.0% Ional Plus was required to achieve similar reductions (reductions of 0.91 and 2.07 log10 CFU/g were obtained with 1.0 and 2.0% Ional Plus, respectively). An Ional or Ional Plus concentration of 1.0% was required to reduce C. perfringens populations in roast beef or injected pork chilled from 54.4 to 7.2°C in 21 h. Cooling times for roast beef or injected pork products after heat processing can be extended to 21 h through the incorporation of 1.0% Ional or Ional Plus into the formulation to reduce the potential risk of C. perfringens germination and outgrowth

Optimization and evaluation of heat-shock condition for spore enumeration being used in thermal-process verification: Differential responses of spores and vegetative cells of Clostridium sporogenes to heat shock

To evaluate a heat-shock condition for the enumeration of Clostridium sporogenes spores, a surrogate for C. botulinum spores, we examined the heat tolerance of C. sporogenes spores and vegetative cells exposed to a heat shock at 90°C. From the D values of the spores determined in the temperature range of 113–121°C, z value (±SD) and D90°C value were estimated to be 10.16±0.90°C and 1,071.52 min, respectively, and the inactivation rates were predicted to be only approximately 2% at 90°C for up to 10 min. Meanwhile, the viable count of spores was significantly higher when activated under a heat-shock condition of 90°C for over 9 min than those activated for shorter time periods. The heat tolerance of vegetative cells was extremely low, showing a D90°C value (±SD) of 0.21±0.01 min. Finally, 3 different heat-shock conditions were compared: 70°C for 30 min, 80°C for 20 min, and 90°C for 10 min, and the experimental comparative data showed no significant differences in viable spore counts. Consequently, these results support that the heat-shock treatment at 90°C for 10 min is suitable to activate spores and to inactivate vegetative cells of C. sporogenes