Nutritional evaluation of common (Tenebrio molitor) and lesser (Alphitobius diaperinus) mealworms in rats and processing effect on the lesser mealworm

The aim of this study was to evaluate the crude protein quality of the two mealworm species Alphitobius diaperinus (AD) and Tenebrio molitor (TM) across different processing methods of AD using the crude protein digestibility-corrected amino acid score (PDCAAS) based on rat trials. Rats (66 +/- 3 g) were kept in single enclosures and fed diets containing 10% crude protein. The eight treatments were freeze-dried TM, freeze-dried AD, defatted AD, extruded AD, formic acid hydrolysed AD, industrial-dried AD, vacuum-dried AD and addition of an enzyme blend to the freeze-dried AD product (n=6 rats). Total collection of faeces and urine was obtained daily during a 4 day sampling period. The results showed that the sulphur-containing amino acids were the limiting amino acids for all treatments. Freeze-dried AD had a better protein quality compared to freeze-dried TM (0.82 and 0.76 for PDCAAS, respectively). Addition of the enzyme blend used in this experiment did not affect PDCAAS. Defatting, extruding and industrial-drying induced a small decrease of protein quality (0.79-0.80), and vacuum drying and acid hydrolysis had more severe effects (0.77 and 0.74 for PDCAAS, respectively). In conclusion, AD is promising as food due to its high protein content of 62% dry matter and due to its high true protein digestibility (91-94% across all treatments). Furthermore, common processing methods such as defatting, industrial drying and extrusion can be applied without major effects on the product's ability to meet human dietary requirements for specific amino acids (0.79-0.82 for PDCAAS).