Browsing by Author "Esteves, Vasco"
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- Impact of different diets and starvation periods on microbial load of Tenebrio molitor larvaePublication . Pereira, Inês; Carvalho, Teresa Bento de; Soares, Luís; Ribeiro, Tiago; Esteves, Vasco; Barbosa, Joana Bastos; Teixeira, PaulaIntroduction: In a world facing an environmental crisis, the growth of the world's population coupled with an increasing demand for natural resources emphasizes the importance of adopting new dietary patterns based on health and sustainability (1). The consumption of edible insects (e.g. Tenebrio molitor) offers an alternative to animal protein sources, providing a sustainable food production cycle that ensures food security with minimal environmental impact (2). The main challenges in the T. molitor production industry are the selection of an appropriate feeding regime, as this affects the growth performance, nutritional profile and microbiota of the insect, and the processing steps required to commercialize mealworm larvae for human consumption. These steps have a direct impact on safety by allowing the gut contents to be discarded, thereby reducing the microbiological load and the presence of pathogenic microorganisms (3, 4). Typically, mealworm larvae are reared in a dry, starchy substrate supplemented by a water source, such as slices of vegetables or fruit. After being reared under optimal growth conditions, the larvae are sifted and then subjected to a fasting period of at least 24 hours, as required by law. This fasting process allows the intestinal contents to be discarded and limits the microbiological load, with the fasting period being a legal requirement of at least 24 hours (3, 4). Objective: This study aimed to analyze the microbiology of Tenebrio molitor larvae subjected to various feeding regimes (substrate with water, potato, carrot, or a fresh vegetable mix) and subsequently subjected to different starvations periods (0 hours, 24 hours, 48 hours and 72 hours). Discussion and conclusions: In general, the performance of starvation is dependent on the diet to which the larvae were subjected for each microbiological parameter evaluated. A positive result is considered when, for larvae subjected to the same diet, the counts of a given parameter at a given starvation period (24 h, 48 h, 72 h) are lower than those observed in the control without starvation (0h). This was observed only for: larvae A, for anaerobic Bacillus spores after 48h, and for yeasts after 72h; larvae B, for aerobic Bacillus spores and anaerobic Bacillus spores after 24 h ,48 h and 72 h and for molds after 24 h and 72h; larvae C, for Enterobacteria and yeasts after 24h and 72h; for aerobic Bacillus spores after 24h, 48h and 72h; and for anaerobic Bacillus spores after 24 h and 48h; larvae D, for TVC, LAB and anaerobic Bacillus spores after 24, 48h, 72h; for Enterococcus after 48 h and 72 h; for Enterococcus after 48h and 72h; for aerobic Bacillus spores after 24 h and 72 h; and for yeasts after 48h. Salmonella spp. and Listeria spp. were not detected in 10 g of each sample analysed. In conclusion, these results call into question the efficacy of fasting periods in reducing the microbial load of T. molitor larvae, as previously reported in other studies, and highlight the importance of heat treatments following fasting to ensure the food safety of the final product.
- Microbiological characterization of Tenebrio molitor after different feeding regimesPublication . Pereira, Inês; Carvalho, Teresa Bento de; Soares, Luís; Ribeiro, Tiago; Esteves, Vasco; Barbosa, Joana Bastos; Teixeira, PaulaIntroduction: In a world facing an environmental crisis, the increase in world population coupled with a growing demand for natural resources emphasizes the importance of adopting new dietary patterns based on health and sustainability. The consumption of edible insects (e.g. Tenebrio molitor) offers an alternative to livestock consumption, providing a sustainable food production cycle that ensures food security with minimal environmental impact. One of the major challenges in the insect production industry is the selection of its feeding regime, since it has a direct impact on the growth performance and in nutritional profile of T. molitor, as well as on its safety, since it may lead to changes in the insect's microbiota and the presence of pathogenic microorganisms. Purpose: This study aimed to analyze the microbiology of Tenebrio molitor larvae subjected to different feeding regimes (substrate with water, potato, carrot, or a fresh vegetable mix). Results: In general, the original substrate had a lower microbial load, while initial larvae (two-weeks old) had a higher microbial load for TVC, LAB, Enterococcus, Enterobacteriaceae and yeasts. Larvae fed with potatoes had slightly higher microbial loads, especially for TVC, LAB, and Enterobacteriaceae. On the contrary larvae fed with carrot had the lower loads for TVC, LAB, aerobic and anaerobic bacillus spores and molds. Escherichia coli was only found at low levels in the substrate (1.0 log CFU/g) and B. cereus in the frass of larvae fed with potato (4.7 log CFU/g). The microbial load of the larvae and respective frass was compared. It was found that only in the potato substrate regime the microbial load was not higher in the frass. Salmonella spp. and Listeria spp. were not detected. Conclusion: This preliminary study indicates apparent differences in the microbial loads of larvae fed with different regimes. An initial substrate with potato seems to increase the microbial load of both larvae and frass. Further studies of the microbial community using culture-independent methods are an alternative to expand knowledge of the microbiota of T. molitor and to overcome the detection limits of of this technique. Although untreated larvae are not fit for human consumption, it is important to further analyze the effect of different treatments on the quality of the final product.