title: Optimization of heat and relative humidity conditions to reduce Escherichia coli O157:H7 contamination and maximize the germination of radish seeds.
abstract: We previously reported that a combination of heat and relative humidity (RH) had a marked bactericidal effect on Escherichia coli O157:H7 on radish seeds. Here, response surface methodology with a Box-Behnken design was used to build a model to predict reductions in E. coli O157:H7 populations based on three independent variables: heating temperature (55 °C, 60 °C, or 65 °C), RH (40%, 60%, and 80%), and holding time (8, 15, or 22 h). Optimum treatment conditions were selected using a desirability function. The predictive model for microbial reduction had a high regression coefficient (R(2) = 0.97), and the accuracy of the model was verified using validation data (R(2) = 0.95). Among the three variables examined, heating temperature (P < 0.0001) and RH (P = 0.004) were the most significant in terms of bacterial reduction and seed germination, respectively. The optimum conditions for microbial reduction (6.6 log reduction) determined by ridge analysis were as follows: 64.5 °C and 63.2% RH for 17.7 h. However, when both microbial reduction and germination rate were taken into consideration, the desirability function yielded optimal conditions of 65 °C and 40% RH for 8 h (6.6 log reduction in the bacterial population; 94.4% of seeds germinated). This study provides comprehensive data that improve our understanding of the effects of heating temperature, RH, and holding time on the E. coli O157:H7 population on radish seeds. Radish seeds can be exposed to these conditions before sprouting, which greatly increases the microbiological safety of the products.
authors.affiliation: Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, South Korea.
authors.forename: M K
authors.initials: MK
authors.lastname: Song
authors.affiliation: Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, South Korea.
authors.forename: H W
authors.initials: HW
authors.lastname: Kim
authors.affiliation: Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, South Korea. Electronic address: rheems@korea.ac.kr.
authors.forename: M S
authors.initials: MS
authors.lastname: Rhee
mesh_terms: D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D003666:Decontamination / Q000379:methods; D003890:Desiccation; D019453:Escherichia coli O157 / Q000254:growth & development*; D005516:Food Microbiology; D018525:Germination; D006358:Hot Temperature; D006813:Humidity; D031224:Raphanus / Q000033:anatomy & histology / Q000254:growth & development* / Q000382:microbiology*; D012639:Seeds / Q000254:growth & development / Q000382:microbiology*
keywords: Desirability function; Heat and relative humidity; Optimization; Response surface methodology; Seed decontamination