Future food systems must provide more food produced on less land with fewer greenhouse gas emissions if the goal is to keep planetary boundaries within safe zones. The valorisation of agricultural and industrial by-products by insects is an increasingly investigated strategy, because it can help to address resource scarcities and related environmental issues. Thus, insects for food and feed have gained increasing attention as a sustainable protein production strategy in circular food systems lately. In this article, we provide an overview on by-products, which have already been fed to T. molitor (mealworms), a common edible insect species. In addition, we investigate other by-products in Austria, which can be suitable substrates for T. molitor farming. We also provide an overview and discuss different perspectives on T. molitor and link it with the circular economy concept. We identify several future research fields, such as more comprehensive feeding trials with other by-products, feeding trials with mealworms over several generations, and the development of a standardized framework for insect rearing trials. In addition, we argue that due to their ability to convert organic by-products from agricultural and industrial processes into biomass in an efficient way, T. molitor can contribute towards resource-efficient and circular food and feed production. However, several hurdles, such as legal frameworks, need to be adapted, and further research is needed to fully reap the benefits of mealworm farming.

Since the human population is continuously growing, sufficient food with low environmental impact is required. Especially, the challenge of providing proteins will deepen and insects can contribute to a more sustainable and efficient source of protein for human consumption. Tenebrio molitor larvae are highly nutritious and rearing mealworms is more environmentally friendly compared to the production of traditional livestock meat. To use T. molitor as a more sustainable alternative to conventional proteins, it is essential to apply diets from a local and sustainable source. Therefore, the objective of this study was to find local by-products or leftovers which can be used in mass production of larvae as a main substrate. Feeding trials investigating twenty-nine different substrates were conducted to evaluate larval growth performance and adult reproduction by determining development times, survival rates, biomass, and fecundity. Several suitable by-products were identified that can be used in high quantities as single component diet for T. molitor rearing, revealing a high survival rate, short development time, high mean total biomass, and successful breeding. The most successful substrate—malt residual pellets—was found to be an alternative to the most used substrate, wheat bran. Furthermore, corn germ meal, sweet chestnuts, bread remains, soybeans, sweet potatoes, and wheat germs have been discovered to be suitable diets for T. molitor. Moreover, the findings of this study contribute towards using several substrates as supplements.

As a result of the increasing focus on alternative protein sources which are ideally still sustainable, the yellow mealworm, Tenebrio molitor, has come into focus. To verify its suitability as a food source in relation to human health, an analysis of the microbiome of larvae of T. molitor is pertinent. Subsequently, the focus of this study was, on the one hand, to analyze the influence of the substrate on the microbial load of the larvae microbiome, and, on the other hand, to determine which processing methods ensure the risk-free consumption of mealworms. For this purpose, mealworms were grown on 10 different substrates derived from by-products of food production (malt residual pellets, corn germ meal, chestnut breakage and meal, wheat bran, bread remains, draff, nettle, hemp seed oil cake, oyster mushrooms with coffee grounds, pumpkin seed oil cake) and microbial loads were analyzed using different selective media. Further starvation/defecation and heating (850 W for 10 min) methods were used to investigate how the reduction of microorganisms is enabled by these methods. The results showed that there was no significant relationship between the microbial load of the substrate and the mealworm. Starvation and defecation led to a lower stock of microorganisms. Heating led to a significant microbial reduction in non-defecated mealworms. The group of defecated and heated mealworms showed no detectable microbial load. In conclusion, firstly, the choice of substrate showed no effect on the microbial load of larvae of Tenebrio molitor and secondly, heating and starvation allow risk-free consumption. This study makes an important contribution for evaluating the safety of mealworms as a sustainable protein source in human nutrition.

Entomophagy is directly connected with culture, explaining why it is commonly rejected in Western countries. Due to increased meat consumption in recent years with its associated negative impacts on health and sustainability, the development of products based on alternative protein sources has become urgent. The larval form of Tenebrio molitor (mealworm) has the potential to substitute meat as it requires less resources and produces less emissions compared to other forms of meat production. Therefore, in this project we have aimed to develop pasta sauces with differing mealworm contents based on a common meat sauce and to test the acceptance with 91 consumers in Austria. Three sauces (100% mealworm, 50% mealworm and 50% meat, 100% meat) were developed and tested using a 9-point hedonic scale for acceptance, and the CATA (Check-All-That-Apply) method was integrated to also receive descriptive information. The analysis of the liking data revealed that the liking for the hybrid sauce with meat and mealworm content was comparable to the meat sauce (6.9 ± 1.8. vs. 6.5 ± 1.8, p > 0.05). Less liked was the sauce with the highest mealworm content (5.7 ± 1.8, p < 0.05). The CATA analysis demonstrated the strongest positive effects on the mean in terms of how much the products were liked for the attribute “fleshy” (0.8). On the other hand, the attributes “brownish” (−0.9) or “mushy” (−1.0) had the strongest negative effects on the mean of the liking of products. We have seen that meat cannot be substituted by mealworm immediately and completely. The results suggest a stepwise substitution and the further adaptation of products regarding the (negative and positive effecting) attributes to increase consumer acceptance.

Due to the current challenges of climate change, population growth in urban settlements and resource depletion, agri-food researchers have put an increasing emphasis on the sustainability transitions of food systems. In this regard, there has been an increasing interest in the local food supply of cities and their surrounding regions, as local food is considered to be a contributing factor toward more sustainable, resilient and just urban food systems. Based on this background, a roadmapping process was conducted to assess the status quo and to identify measures to enhance the local food supply in the city-region of Graz in Austria. We conducted semi-structured interviews with 47 stakeholders, analysed textual materials and calculated food carrying capacities. The obtained data served as input for a series of three workshops, where measures were derived. Our results suggest that cooperation among agri-food stakeholders should be facilitated by local decision makers in order to promote food from regional sources within the target area. Furthermore, smart technologies can help to scale-up local food supply schemes, and to track down food stocks and flows more efficiently. Besides, food policy councils and open food labs can help to incubate food product innovations and to support partnerships among agri-food stakeholders, including local small-scale farmers. In the future, engagement and empowerment processes with local food stakeholders should be addressed to enable transformational processes. Roadmaps can help to initiate such processes.

Since Tenebrio molitor L. was approved by the EU as novel food in 2021, food safety is paramount for both chemically and microbiologically safe products. Since T. molitor larvae are reared on substrates mainly based on cereals, mycotoxins and heavy metals may represent a serious risk. However, analyses of mycotoxins and heavy metals are complex and cost-intensive procedures, which may not be affordable for small-scale farmers on a regular basis. To provide a preliminary risk assessment and to add further insights to existing knowledge, this study used a rapid screening method based on MALDI-TOF to identify potentially mycotoxin-producing microfungi. The colony-forming units (CFU) were determined, and the isolated species identified. In addition, a_w-values of substrates and meal (four samples, nine repeats each) were determined to assess mycotoxin-related risks. Eight mycobionts were identified, including three potential mycotoxin producers: Penicillium citrinum, Aspergillus flavus, and Aspergillus brasiliensis. Very low CFU counts (<3 × 10³ CFU/g) and a_w-values (0.35–0.59) indicate minor risks. LC-MS/MS mycotoxin analysis of nine samples (varying in source and time point) confirmed concentrations below the limit of detection (LoD): 0.50 µg/kg for aflatoxins B1/B2/G1/G2; 50 µg/kg for DON/FuB1/FuB2; 20 µg/kg for HT2/T2; 150 µg/kg for NIV; 1 µg/kg for OTA; and 5 µg/kg for ZEA. Heavy metal analysis (ICP-OES/MS) of three substrates and insect meal showed that all six metals (Cd, Pb, Hg, Sb, As, Cr) were below the LoD (0.2 mg/kg), except for Cr in malt residual pellets (0.4 mg/kg).