AUTHOR=Boulos Samy , Tännler Anina , Nyström Laura 

TITLE=Nitrogen-to-Protein Conversion Factors for Edible Insects on the Swiss Market: T. molitor, A. domesticus, and L. migratoria

JOURNAL=Frontiers in Nutrition

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2020.00089

DOI=10.3389/fnut.2020.00089

ISSN=2296-861X

ABSTRACT=<p>With an increasing worldwide demand for animal protein, insects are becoming a promising sustainable option for meat protein replacement. However, reported protein contents of insects are often overestimated when calculated as “crude protein” = 6.25 × nitrogen content (<italic>N</italic>), compared to true protein contents quantified from the sum of amino acid (AA) residues. In this study, the main two types of usual nitrogen-to-protein conversion factors <italic>k</italic><sub><italic>p</italic></sub> and <italic>k</italic><sub><italic>A</italic></sub> were determined on the basis of true protein/total nitrogen and true protein/protein nitrogen, respectively, with focus on the three insect species legally sold on the Swiss food market. <italic>T. molitor</italic> (mealworm larvae), <italic>A. domesticus</italic> (house crickets), and <italic>L. migratoria</italic> (locusts) from various breeders were analyzed for total and amide nitrogen, chitin, and AA composition. Careful control experiments of insect samples spiked with a protein standard were conducted to establish the recovery of true protein, which was with &gt;95% excellent. Mealworms, crickets, and locusts exhibited similar AA-profiles and true protein contents of 51, 55, and 47 g/100 g (dry weight basis), respectively. Specific conversion factors <italic>k</italic><sub><italic>p</italic></sub> showed little variability between the three insect species with 5.41, 5.25, and 5.33 for mealworms, crickets, and locusts, respectively, and confirmed an average ~17% overestimation of protein contents when using 6.25 × <italic>N</italic>. The determined average <italic>k</italic><sub><italic>p</italic></sub> of 5.33 is supported by extracted literature data and is suggested for general use instead of 6.25 × <italic>N</italic> to calculate more accurate insect protein contents, whereas the average pure protein conversion factor <italic>k</italic><sub><italic>A</italic></sub> of 5.6 is proposed for use in the case of insect protein isolates.</p>