Microbiology of cooked and dried edible Mediterranean field crickets (Gryllus bimaculatus) and superworms (Zophobas atratus) submitted to four different heating treatments

Abstract

To increase the shelf life of edible insects, modern techniques (e.g. freeze-drying) add to the traditional methods (degutting, boiling, sun-drying or roasting). However, microorganisms become inactivated rather than being killed, and when rehydrated, many return to vegetative stadia. Crickets (Gryllus bimaculatus) and superworms (Zophobas atratus) were submitted to four different drying techniques (T1 = 10' cooking, 24 h drying at 60℃; T2 = 10' cooking, 24 h drying at 80℃; T3 = 30' cooking, 12 h drying at 80℃, and 12 h drying at 100℃; T4 = boiling T3-treated insects after five days) and analysed for total bacteria counts, Enterobacteriaceae, staphylococci, bacilli, yeasts and moulds counts, E. coli, salmonellae, and Listeria monocytogenes (the latter three being negative throughout). The microbial counts varied strongly displaying species- and treatment-specific patterns. T3 was the most effective of the drying treatments tested to decrease all counts but bacilli, for which T2 was more efficient. Still, total bacteria counts remained high (G. bimaculatus > Z. atratus). Other opportunistically pathogenic microorganisms (Bacillus thuringiensis, B. licheniformis, B. pumilis, Pseudomonas aeruginosa, and Cryptococcus neoformans) were also encountered. The tyndallisation-like T4 reduced all counts to below detection limit, but nutrients leakage should be considered regarding food quality. In conclusion, species-specific drying procedures should be devised to ensure food safety.

Microbiological Load of Edible Insects Found in Belgium

“…Nevertheless, this technique is known to mostly inactivate microorganisms rather than kill them, and, when rehydrated, many could return to a vegetative stage that could be harmful [29]. Consequently, some authors recommend applying a heat treatment to freeze-dried insects before consuming them [29], but no data are available on the specifications of this treatment. The freeze-drying conditions of the insects used for this study were unfortunately not available.…”

Edible Insects Processing: Traditional and Innovative Technologies

“…The vast majority of microorganisms stop growing at aw <0.65. When aw is low, microorganisms show slowed growth, and when water conditions are appropriate, they can start growing again (Grabowski & Klein, , ). A reduction of free water increases the dry matter concentration significantly without damaging the tissues or the physical appearance of foods and is an important step for food ingredient extraction (Lamidi, Jiang, Pathare, Wang, & Roskilly, ).…”

“…However, regardless of the blanching and drying treatments applied to insects, they should be reheated before consumption to eliminate residual microorganisms. Boiling dried insects for 30 min has been found to be a good approach for eliminating total bacteria, Enterobacteriaceae, Staphylococcus, Bacilli , yeasts, and molds (Graboswki & Klein, ).…”

Novel foods: a risk profile for the house cricket (Acheta domesticus)

“…Other important species, such as Salmonella spp. or Escherichia coli , have been rarely reported by plating (Caparros Megido et al., ; Grabowski and Klein, ; Osimani et al., ; Vandeweyer et al., ). Despite not being natural reservoirs for well known food‐borne bacteria, crickets might be contaminated during processing (i.e.…”