Refining protein quantification in cricket and mealworm ingredients: impact of killing and drying methods on K p and K A conversion factors

Abstract Inconsistent nitrogen-to-protein conversion factors ( ) reported for insect-derived products challenge the accuracy of nitrogen-based protein quantification. Conversely, the alternative factor, derived from protein-bound nitrogen (N P ), has shown greater reproducibility across studies. However, the impact of processing on the variability of and values has yet to be investigated. This study evaluated the influence of killing (freezing, blanching) and drying (freeze-drying, oven-drying, roasting) treatments on and conversion factors in ingredients (meals and protein extracts (PE)) derived from crickets ( Acheta domesticus ) and mealworms ( Tenebrio molitor ). The and factors were calculated from the amino acid profiles, alongside compositional characteristics, protein profiles and nitrogen partitioning. Crickets killed by freezing exhibited significantly lower factors (3.11–4.21) than those subjected to blanching (3.86–4.75), whereas factors remained unaffected by processing (5.64 for meals, 5.61 for PEs). Similarly, factors of mealworm-derived products varied widely with processing (4.40–5.65), while values were constant (5.73 for meals, 5.76 for PEs). Oven-drying and roasting significantly N P proportions particularly in mealworms, indicating enhanced proteolysis and progression of enzymatic browning. Protein contents calculated using recovered N P fractions and ranged from 20–37% in crickets and were aligned with the sum of total amino acids (24–48%), whereas discrepancies were observed between the two methods for mealworm products, with respective protein contents of 15–42% and 46–65%. These findings support adoption of the factor for universal protein quantification in insect matrices and highlight the need for standardisation in amino acid methodologies adapted to edible insects.