Publications

The nitrogen-to-protein conversion factor K_p is widely used to estimate crude protein content in edible insect meals. However, reported K_p values vary widely across studies, raising concerns about their reliability. This study investigates using an alternative conversion factor, K_A, applied to protein-derived nitrogen, to more accurately measure the true protein content in insect meals. Ten commercial insect meals, including five cricket-based (Acheta domesticus, Gryllodes sigillatus) and five mealworm-based (Tenebrio molitor) meals marketed in Canada were analysed. The K_p and K_A factors were calculated from amino acid profiles, and nitrogen distribution was determined. The non-protein and non-chitin nitrogen (N_NP,NC) was removed through protein precipitation using trichloroacetic acid and acetone. Then, protein nitrogen (N_P) was separated from chitin-bound nitrogen (N_C) through chemical deproteinisation. While K_p values varied significantly between the commercial meals, K_A values were consistent, averaging 5.61 for cricket meals and 5.69 for mealworm meals. Protein nitrogen constituted approximately two thirds of the total nitrogen in the meals, while the N_{NP, NC} fraction represented 13-24% of the total nitrogen, and varied significantly, even among products from the same species. An additional 8-17% of the total nitrogen remained uncharacterised. Using the conventional K_P value of 6.25 resulted in a 35-46% overestimation of protein content compared with using K_A applied to N_P, while the commonly accepted insect meal-specific K_p value of 4.76 still led to a 15-29% overestimation. These findings support using K_A factors (5.61 for orthopterans, 5.69 for coleopterans) applied to protein-derived nitrogen as a more accurate approach to quantify proteins in insect-based ingredients.