Due to the growing global population, the need for new sources of protein is increasing. Insects are one of the promising solution. Despite their advantages, ensuring the safety of these new foods is of paramount importance. Fermentation, as one of the oldest methods of food preservation, can improve the microbiological safety of insects; however, this area is still relatively unexplored. In this master's thesis, we investigated whether lactic acid fermentation affects the microbiological safety of freeze-dried house crickets (Acheta domesticus) and mealworm larvae (Tenebrio molitor). Before fermentation insects differed the most in the number of sporogenic bacteria, enterococci, and molds, with house crickets containing more of these. We performed three different fermentations: the addition of Lb. plantarum starter culture, the addition of a meat starter culture, and spontaneous fermentation. We confirmed the fermentations by measuring pH and growth of lactic acid bacteria (LAB), where the pH drop was not significant in any of the fermentations performed, but the number of LAB increased in all samples. The results showed that there were No significant differences in the microbiological safety of fermented insects between the different fermentations, except in the case of sporogenic bacteria in house crickets, where the controlled fermentations had a more inhibitory effect on their growth. No pathogenic bacteria of Salmonella, Listeria monocytogenes, Escherichia coli, Bacillus cereus, Clostridium perfringens, coagulase-positive staphylococci, and coliform bacteria were detected in any sample. Fermentation inhibited the growth of molds, yeasts, and aerobic sporogenic bacteria in house crickets, and the growth of molds and yeasts in mealworm larvae. The total number of aerobic and anaerobic mesophilic bacteria, and enterococci increased after all three fermentations in both types of insects. Our results indicate that fermentation of freeze-dried insects can improve their microbiological safety, although further research is needed to optimize the fermentation process.
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