State of the art of nonthermal and thermal processing for inactivation of micro-organisms

Abstract

Despite the constant development of novel thermal and nonthermal technologies, knowledge on the mechanisms of microbial inactivation is still very limited. Technologies such as high pressure, ultraviolet light, pulsed light, ozone, power ultrasound and cold plasma (advanced oxidation processes) have shown promising results for inactivation of micro-organisms. The efficacy of inactivation is greatly enhanced by combination of conventional (thermal) with nonthermal, or nonthermal with another nonthermal technique. The key advantages offered by nonthermal processes in combination with sublethal mild temperature (<60°C) can inactivate micro-organisms synergistically. Microbial cells, when subjected to environmental stress, can be either injured or killed. In some cases, cells are believed to be inactivated, but may only be sublethally injured leading to their recovery or, if the injury is lethal, to cell death. It is of major concern when micro-organisms adapt to stress during processing. If the cells adapt to a certain stress, it is associated with enhanced protection against other subsequent stresses. One of the most striking problems during inactivation of micro-organisms is spores. They are the most resistant form of microbial cells and relatively difficult to inactivate by common inactivation techniques, including heat sterilization, radiation, oxidizing agents and various chemicals. Various novel nonthermal processing technologies, alone or in combination, have shown potential for vegetative cells and spores inactivation. Predictive microbiology can be used to focus on the quantitative description of the microbial behaviour in food products, for a given set of environmental conditions.

Effects of cold plasma, gamma and e-beam irradiations on reduction of fungal colony forming unit levels in medical cannabis inflorescences

“…There have been many reports regarding the efficacy of different non-thermal treatments for food and herb sterilization, especially the utilization of gamma irradiation (Guerreiro et al 2016;Jeong et al 2015;Sádecká 2007). Alternatively, e-beam (beta irradiation) and cold plasma, are effective for food sterilization and are safe for human consumption (Jeong et al 2015;Misra et al 2019;Moreno et al 2007;Van Impe et al 2018). Even though these methods have been applied or suggested for decontaminating MC inflorescences to safeguard its use by immunocompromised patients, there is a lack of knowledge in regards to their efficacy in eliminating deleterious microorganisms.…”

Potential Applications of Non-thermal Plasma in Animal Husbandry to Improve Infrastructure

“…NTP has been introduced as an effective treatment for this purpose by previous studies. They have shown the ability of NTP to decontaminate food and extend the shelf-life of food (98)(99)(100)(101)(102). NTP also inactivates thermophilic bacteria which cannot be destroyed by conventional methods.…”

Two Nonthermal Technologies for Food Safety and Quality—Ultrasound and High Pressure Homogenization: Effects on Microorganisms, Advances, and Possibilities: A Review

“…The key findings on NTT, reported by Van Impe et al (137), can be summarized as follows: (i) NTTs are effective on vegetative cells, whereas the inactivation of spores can be achieved by combining multiple hurdles; (ii) NTTs result in higher inactivation rates in model systems than they do in foods; and (iii) NTTs are effective in liquid foods. Figure 1 shows the most important NTTs and the main approaches they are based on (physical and chemical).…”

“…This global threat is generally counteracted by food preservation (FP). According to Lado and Yousef (78) and Van Impe et al (137), FP aims to disturb homeostasis; if microorganisms cannot obtain homeostasis and respond to stress, they either are unable to grow or they die. The core of FP is to create a stress or an unfavorable condition and to reversibly or irreversibly modify homeostasis and to thereby achieve microbial inhibition or inactivation.…”

“…Thus, consumer demands for safety and minimally processed foods with high-quality attributes have encouraged the food industry and scientific researchers to design alternative nonthermal technologies (NTTs) to produce foods with a minimum of changes induced by the technologies themselves (16,21,71). Definitions for NTT can be found in the articles of Tiwari et al (130) and Van Impe et al (137): NTTs are approaches that are effective at sublethal or ambient temperatures and that lead to minimal or no impacts on key nutritional and quality food parameters.…”