Abstract
With the growing public interest in edible insects, breeders are forced to increase the volume of production and shorten the life cycle of farmed insects. The exact composition of the feed is the know-how of each manufacturer. The aim of this work was to determine the general impact of individual conventional types of feed (bran, whey, raw ware potatoes) on the life cycle rate of Tenebrio molitor (TM), larval mortality and the content of fats, fatty acids and nitrogenous substances in larvae and their excrements. For the reasons of sustainability of the state of nature and waste disposal, polystyrene foam was added to the experiment as feed. The experiment was performed in two phases—rearing for 21 weeks and 5 weeks. The nitrogen content was determined using the Kjeldahl method (ISO 1871: 2009), the fat content by the Soxhlet method and the fatty acid profile using a gas chromatograph with a flame ionization detector (FID). The results of the work show that the basis of the TM feed is wheat bran, not only due to the observed low larval mortality (45% over 21 weeks) and their optimal nutritional value (nitrogenous substances 53.6% DM, fat 37.1% DM, the highest total fatty acid content) but also due to the higher speed of TM development. Lower larval mortality during rearing was found when feeding dried whey and raw ware potatoes, but the development cycle rate was low. This confirmed that the bran as a feed allowed a fast life cycle with good larval nutritional parameters. From a nutritional and reproductive point of view, TM appeared to be a suitable alternative to animal production. Polystyrene as a feed, tested for biodegradation by TM larvae, caused the highest larval mortality (75% in 21 weeks). However, the content of nitrogenous substances in the larvae increased to 69.77%, in the excrement, it even increased to 82.68%, and there was no cannibalism among the larvae. The work thus demonstrated the possibility of biodegradation of polystyrene using TM larvae with an increase in nitrogenous substances in both larvae and excrement.
Highlights
Edible insects are one of the oldest animal foods in the human diet
After calculating the total sums of individual types of fatty acids, the results showed the smallest share was in the sample fed potatoes (10–12%), in polystyrene (11–13%)
The quality of rearing of the larvae of Tenebrio molitor is a basic indicator of the quality and safety of edible insects
Summary
Edible insects are one of the oldest animal foods in the human diet. More than 2 billion people consume edible insects [1], there has been a rather negative attitude. Sustainability 2021, 13, 12992 towards insect consumption in developed countries in Europe and America. At present, this attitude is gradually changing. Organization (FAO), insects are important as food due to rising animal protein cost, food insecurity, environmental pressures, population growth and growing protein demand. The FAO suggests that insects could become an alternative source of protein that is comparable to other animal proteins. Insects are a good source of food high in fats, proteins, fiber and some vitamins and minerals. The environmental benefits of insect farming are significant, based on the high efficiency of insect conversion for feed, lower greenhouse gas emissions, less use of water and arable land and the use of insect-based bioconversion as a tradable solution to reducing food waste [2,3,4]
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