22·T)R2=0.98 In this study, the relationship between temperature and oregano EO concentration in the resistance of B. coagulans spores was investigated. These particular variables were explored regarding their influence on the degree of microbial inactivation. Due to quality and sensorial reasons, it is really important to find an optimal time and temperature combination for food heating process. Addition of natural food-compatible additives could decrease optimal time and
temperature combinations ( Juneja et al., 2010 and Juneja et al., 2006). The literature suggests a positive interaction for thermochemical treatments involving heat and natural preservatives, such as essential GSK458 in vivo oils and their major molecules (Karatzas et al., 2000, Periago et al., 2006 and Somolinos et al., 2010). For instance, application of mild heat treatment at 55 °C was not enough to prevent the growth of Saccharomyces cerevisiae in non-carbonated fruit juice ( Belletti et al., 2007 and Belletti et al., 2010). However, heat treatment at 55 °C for 16 min with concentrations above see more 100 μg/g of citral, a molecule present in some essential oils, resulted in a probability of 90% of bottles not being contaminated with the fungus. As shown in Fig. 1, Fig. 2 and Fig. 3, the Weibull model fitted well to the inactivation curves. Even though the Weibull model
has an empirical nature, a connection can be made with physiological effects (van Boekel, 2002). All inactivation curves described in this study by the Weibull model had shown a downward concavity (α > 1). The shape factor larger than 1 indicates that remaining spores become increasingly damaged, and probably the continued exposure results in accumulated damage ( Peleg, 2006 and van Boekel, 2002). This also means that it takes a progressively shorter time to destroy the same fraction of B. coagulans spore survivors as the survival ratio decreases ( Aragao, Corradini, Normand,
& Peleg, 2007). IMP dehydrogenase The parameter β is usually considered a measure of microorganism resistance to treatment and decreases with temperature ( Unluturk, Atilgan, Baysal, & Unluturk, 2010). The time to reach 6 decimal reductions, a microbial reduction usually considered sufficient for pasteurization, decreases with the increase of temperature and EO concentration. The thermal inactivation at the highest temperature, 103 °C, resulted in the lowest value for the t6D. For the thermochemical inactivation at 100 °C with different EO concentration, the t6D was lower at 500 μg/g followed by oregano EO at 1000 μg/g and 400 μg/g. Even though at 400 μg/g of oregano EO the t6D was longer than at 500 and 1000 μg/g, this concentration was chosen to continue the experiments with different temperatures, because it can result in a milder sensory impact. Since at 1000 μg/g the death of spores was slower than at 500 μg/g, B. coagulans may be affected only up to a certain EO concentration.