The aim of the project was to investigate the possibility of using by-products from Icelandic agriculture as feed for mealworms (Tenebrio molitor). Feeding experiments were conducted where mealworms were fed wheat with carrots as a control diet, wheat with cucumber leaves or wheat with tomato leaves. In addition, measurements were made of nutritional value, glycoalkaloids, heavy metals and other trace elements, pesticide residues and microorganisms in the diet and freeze-dried larvae. The results showed that the type of feed had a clear effect on the growth, survival and fertility of the mealworms. Cucumber leaves proved to be the most advantageous raw material of those tested and gave higher larval production, better growth and a higher protein content in the final product than the control diet. Tomato leaves, however, proved to be less suitable, as they were associated with lower growth, higher mortality and lower fertility. Measurements of glycoalkaloids showed that α-tomatine was present in high concentrations in tomato leaves but in much lower levels in post-harvest larvae, suggesting that the mealworms can partially, but not completely, degrade the substance. Pesticide residues were not found in the samples and heavy metal levels were generally low, although cadmium in larvae warrants continued monitoring. Listeria monocytogenes and Salmonella were not detected in the final product, but the total number of aerobic microorganisms was above the limit in all samples. The results therefore indicate that cucumber leaves are a promising raw material for mealworm feed, but that the use of tomato leaves cannot be recommended under the conditions studied in the project. It is also clear that further development of processing, handling and microbial safety is necessary before such production can be adopted on a larger scale.
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The aim of the project was to evaluate the potential of using by-products from Icelandic greenhouse horticulture as feed for yellow mealworms (Tenebrio molitor). Feeding trials were carried out using wheat supplemented with carrots as a reference feed, cucumber leaves, or tomato leaves. In addition, analyzes were performed on nutritional composition, glycoalkaloids, heavy metals and other trace elements, pesticide residues, and microbiological quality in both feed materials and freeze-dried larvae. The results showed that feed type had a clear effect on mealworm growth, survival, and fertility. Cucumber leaves were the most promising raw material tested, resulting in higher larval production, better growth, and higher protein content in the final product than the reference feed. Tomato leaves were less suitable, being associated with reduced growth, higher mortality, and lower fertility. Glycoalkaloid analyzes showed that α-tomatine was present at a high level in tomato leaves but at a much lower level in harvested larvae, indicating partial but incomplete degradation by the mealworms. No pesticide residues were detected, and heavy metal levels were generally low, although cadmium detected in the larvae indicates a need for continued monitoring. Listeria monocytogenes and Salmonella were not detected in the final product, whereas total aerobic counts were above reference limits in all samples. Overall, the findings indicate that cucumber leaves are a promising feed ingredient for mealworms, whereas tomato leaves cannot be recommended under the conditions tested in this project. Further work on processing, handling, and microbiological safety is needed before this type of production can be implemented on a larger scale.