Effects of long-lasting cold storage on Tenebrio molitor larvae (Coleoptera: Tenebrionidae)

Abstract

Insects are an emergent source of proteins in the world nutrition, both for humans and farmed animals, moreover they represent a novel food in Europe. The interest in Tenebrio molitor (L.) has particularly grown because its larvae are very rich of high biological value proteins. Although rearing of T. molitor has lately increased, the long-time conservation of alive larvae, very useful for both production and research, needs more information. Research studies conducted so far have investigated the reactions to low temperature on mealworms pupae and adults, or on larvae at 10 °C and for no more than 48 h. The aim of this study is to test the long-term effects of different times of cold storage at 10 °C on the larval survival and on the ability to become healthy adults and to potentially reproduce normally. The insects, divided in experimental groups, were refrigerated on sterile bran (and 10% of yeast) at 10±1 °C and 63% RH for 4 different periods of storage, from 30 to 120 days. Larval survival (i.e. number of larvae alive and number of pupae, expressed as a percentage), weight gain and presence of pupae were detected at the end of each period. The ability to complete the cycle was assessed by detecting the number of hatched pupae, deformed and well-formed adults. Our research results point out the possibility to store T. molitor alive larvae for long time (at least 120 days) at low temperature without significant negative effects on their ability to survive, with a relatively small loss (15.81%) and a very small percentage of deformed adults (4.07%). Further researches will be carried out to test the fertility of the well-formed adults and their ability to reproduce.