Bootstrapping for Estimating the Conservative Kill Ratio of the Surrogate to the Pathogen for Use in Thermal Process Validation at the Industrial Scale.

A surrogate is commonly used for process validations. The industry often uses the target log cycle reduction for the test (LCRTest) microorganism (surrogate) to be equal to the desired log cycle reduction for the target (LCRTarget) microorganism (pathogen). When the surrogate is too conservative with far greater resistance than the pathogen, the food may be overprocessed with quality and cost consequences. In aseptic processing, the Institute for Thermal Processing Specialists recommends using relative resistance (DTarget)/(DTest) to calculate LCRTest (product of LCRTarget and relative resistance). This method uses the mean values of DTarget and DTest and does not consider the estimating variability. We defined kill ratio (KR) as the inverse of relative resistance.The industry uses an extremely conservative KR of 1 in the validation of food processes for low-moisture foods, which ensures an adequate reduction of LCRTest, but can result in quality degradation. This study suggests an approach based on bootstrap sampling to determine conservative KR, leading to practical recommendations considering experimental and biological variability in food matrices. Previously collected thermal inactivation kinetics data of Salmonella spp. (target organism) and Enterococcus faecium (test organism) in Non-Fat Dried Milk (NFDM) and Whole Milk Powder (WMP) at 85, 90, and 95°C were used to calculate the mean KR. Bootstrapping was performed on mean inactivation rates to get a distribution of 1000 bootstrap KR values for each of the treatments. Based on minimum temperatures used in the industrial process and acceptable level of risk (e.g., 1, 5, or 10% of samples that would not achieve LCRTest), a conservative KR value can be estimated. Consistently, KR increased with temperature and KR for WMP was higher than NFDM. Food industries may use this framework based on the minimum processing temperature and acceptable level of risk for process validations to minimize quality degradation.

Radiofrequency Inactivation of Salmonella in Black Pepper and Dried Basil Leaves Using In-package Steaming.

Radiofrequency (RF) heating has been extensively studied for pasteurizing low-moisture foods. Currently, bulk foods are treated with radiofrequency; potential cross-contamination may occur during packaging of pasteurized products. As an alternative, in-package RF processing was evaluated for Salmonella inactivation on black peppercorns and dried basil leaves and prevention of cross-contamination during storage postprocessing. In-package steaming refers to the process in which the samples were heated in a steam vent package to generate and retain steam during the treatment. This treatment achieved good heating uniformity which could be because of the circulation of steam within the package. One-way steam vent allowed the release of excess steam once a threshold pressure was achieved and later returned to its original position to seal the package, when the RF energy was removed. In-package RF steaming of black peppercorns and dried basil leaves for 135 s and 40 s, respectively, resulted in more than 5 log reduction of Salmonella. The steam vent remained stable posttreatment and properly sealed the package to protect the product from any external contamination. These results indicate that the use of steam vent could effectively pasteurize black peppercorns and dried basil leaves could be beneficial in preventing the potential cross-contamination postprocessing.

Thermal inactivation kinetics of Salmonella enterica and Enterococcus faecium NRRL B-2354 as a function of temperature and water activity in fine ground black pepper.

Fine ground black pepper generally consumed as a seasoning without any further processing has been associated with Salmonella enterica outbreaks. Thermal inactivation kinetics data is necessary to develop a pasteurization process for fine ground black pepper. This study investigates the influence of temperature and water activity on thermal inactivation kinetics of Salmonella in fine ground black pepper. It also assesses the suitability of Enterococcus faecium as a surrogate for Salmonella. Fine ground black pepper of varying water activities, aw (0.40, 0.55, 0.70) was subjected to isothermal treatments at different temperatures (65-80 °C) for five equidistant time points with intervals ranging from 18 s to 250 min. The survival data were used to fit two primary models (log-linear and Weibull) and two secondary models (response surface and Modified Bigelow). Results indicated that among the two primary models, the Weibull model explained the thermal inactivation kinetics better with lower RMSE (0.24 - 0.56 log CFU/g) and AICc values at all aw and temperatures. Water activity and treatment temperature significantly enhanced the thermal inactivation of Salmonella. E. faecium NRRL B-2354 was found to be a suitable surrogate for Salmonella in fine ground black pepper at all tested treatment conditions. The developed modified Bigelow model based on the Weibull model could be applied to predict the inactivation kinetics of Salmonella in black pepper and would benefit the spice industry in identifying process parameters for thermal pasteurization of fine ground black pepper.

Validation of process technologies for enhancing the safety of low-moisture foods: A review.

The outbreaks linked to foodborne illnesses in low-moisture foods are frequently reported due to the occurrence of pathogenic microorganisms such as Salmonella Spp. Bacillus cereus, Clostridium spp., Cronobacter sakazakii, Escherichia coli, and Staphylococcus aureus. The ability of the pathogens to withstand the dry conditions and to develop resistance to heat is regarded as the major concern for the food industry dealing with low-moisture foods. In this regard, the present review is aimed to discuss the importance and the use of novel thermal and nonthermal technologies such as radiofrequency, steam pasteurization, plasma, and gaseous technologies for decontamination of foodborne pathogens in low-moisture foods and their microbial inactivation mechanisms. The review also summarizes the various sources of contamination and the factors influencing the survival and thermal resistance of pathogenic microorganisms in low-moisture foods. The literature survey indicated that the nonthermal techniques such as CO2 , high-pressure processing, and so on, may not offer effective microbial inactivation in low-moisture foods due to their insufficient moisture content. On the other hand, gases can penetrate deep inside the commodities and pores due to their higher diffusion properties and are regarded to have an advantage over thermal and other nonthermal processes. Further research is required to evaluate newer intervention strategies and combination treatments to enhance the microbial inactivation in low-moisture foods without significantly altering their organoleptic and nutritional quality.