## 4 Discussion
This could be attributed to the fact that, in the conventional method, it is necessary to wait until all the components are well dissolved in the medium, after which it is boiled. In contrast, in the novel microwave oven sterilization method, the medium is heated only during the microwave oven exposure time. Furthermore, it was observed that the exposure time with the best microbial growth results was 10 min for _S._ ser. Typhimurium, _E. coli_ ATCC 25922, and _P. aeruginosa_. In this medium, the darkening of the medium was also correlated with the exposure time in the microwave. In a previous study, the properties of this medium also improved with the separation of the components (agar vs. the rest of ingredients) during the autoclaving process [6]. Using the microwave method, liquid media (TSB and Sabouraud dextrose broth) were also analyzed, as they are routinely used in microbiological quality laboratories. All media sterilized in the microwave oven performed in the same way as the media sterilized in the autoclave for all micro-organisms tested. As both media contain glucose, in future studies, it is necessary to quantify the microbial growth obtained, as a lower degradation of glucose could have occurred in the media prepared in the microwave, thus favoring microbial growth. Improvement of the enrichment media is relevant, for example, in the analysis of food. In the case of the detection of _L. monocytogenes_ in food, at present, there is interest in finding alternatives to the Fraser medium. Identification of the best method for medium sterilization could also contribute to obtaining higher recovery rates. Regarding pH values, we reported that SDA particularly increased its acidification after 15 min of exposure, likely due to the thermal degradation of glucose, which is in agreement with other previous studies [7]. Regarding the study of microbial destruction using the microwave system, live bacteria (_E. coli_) and bacterial endospores (from _B. subtilis_ and _G. stearothermophilus_) were used. In the case of the spores of _G. stearothermophilus_, added at 5 \(\times\) 10\({}^{4}\) spores/bottle, complete destruction was not obtained at 7 min. It should be noted that these endospores are highly thermoresistant and used as a biological sterilization indicator [35] during autoclaving cycles. However, they are not commonly found in dehydrated culture media and germinate at temperatures higher than 45 \({}^{\circ}\)C. For these reasons, their presence at a low concentration in dehydration media would not indicate interference during the most common microbiological analysis. However, more studies should be carried out to optimize their complete elimination using this system. When the medium was contaminated with the endospores of _B. subtilis_ ATCC 6633, the time needed to reach three decimal reductions was approximately 4.5 min, with a count of 0.33 \(\pm\) 0.58 CFU remaining when the medium was sterilized in the microwave oven for 7 min. Considering that dehydrated media would not contain high concentrations of _Bacillus_ endospores, these results should not represent an issue, although more studies should be performed to optimize this destruction. Finally, as expected, complete destruction was obtained for _E. coli_ ATCC 8739 with an exposure time of 4 min, in agreement with previous studies [17]. It should be noted that, according to our experience, _Pseudomonas_ could also be found in dehydrated media. Therefore, the inclusion of this bacteria in future microbial destruction studies would be of interest. An important aspect of the microwave system is safety. The puncture of the rubber cap and the application of the sticker allows for depressurization, prevents medium contamination, and avoids medium leakage. To increase safety, other safety strategies could be added, such as the delayed opening of the door, allowing for depressurization before opening, and a polycarbonate cover for the water bath.