Protein binding assays for an accurate differentiation of vitamin B12 from its inactive analogue. A study on edible cricket powder

•Microbiological assays overestimate the vitamin B12 in insect food products.•A convenient protocol with the protein intrinsic factor accurately quantifies B12.•The specificity is further improved by using a newly-developed correction coefficient.•A low level of vitamin B12 is found in edible cricket powder: 0.75–2.2 μg/100 g.•In contrast, excessive nonfunctional B12-analogues are present: 40–60 µg/100 g. Inactive analogues of vitamin B12 (cobalamin, Cbl) can mimic the active Cbl in food if using the traditional microbiological measurements. Thus, overestimated Cbl was recently revealed in edible insects employing immunoaffinity adsorption, HPLC-separation and mass spectrometry (https://doi.org/10.1016/j.foodchem.2021.129048). Here we demonstrate the utility of a convenient binding assay to evaluate Cbl in edible cricket powders. The assay employed the Cbl-specific protein intrinsic factor (IF) and the analogue-detecting protein haptocorrin. The excessive analogues had a weak affinity for IF, resulting in a modest overestimate of Cbl. This overestimate was corrected by a novel mathematical procedure, based on the ratio of analogue/Cbl in the sample and their relative affinities for IF. We found that 100 g of cricket powders contained 40–60 µg of analogues and 0.75–2.2 μg of Cbl. This result was confirmed by HPLC. A correct approach to Cbl-measurements is essential for nutritional assessment of any analogue-containing food.