Abstract
The Kjeldahl method is the most utilized method for total protein content analysis in food. Using the universal nitrogen-to-protein conversion factor of 6.25, the protein content of insects is likely to be overestimated due to their chitin content. We have calculated nitrogen-to-protein conversion factors for two crickets, house cricket (Acheta domesticus) and field cricket (Gryllus bimaculatus), which are used for food and feed in Europe. By analyzing their nitrogen and amino acid content we were able to show that a conversion factor of 5.09 could be used for house cricket and 5.00 for field cricket in protein content calculation. Based on these results with a reservation about slight variation in farming conditions, we suggest a nitrogen conversion factor of 5.0 for both crickets.
Highlights
One of the emerging trends in European food is entomophagy, i.e., the eating of insects (Santeramo et al 2018, Patel et al 2019)
If certain food contains more non-protein nitrogen (NPN) than food in general, the universal nitrogen-to-protein conversion factor of 6.25 used in the Kjeldahl method can lead to overestimation of the calculated protein content
The current study measured the amounts of amino acids on a fresh weight basis
Summary
One of the emerging trends in European food is entomophagy, i.e., the eating of insects (Santeramo et al 2018, Patel et al 2019). The field cricket (Gryllus bimaculatus) is primarily used in Europe as feed for insectivorous animals (https://ec.europa.eu/food/safety/novel_food/authorisations/summary-applications-and-notifications_en, 5.4.2019). These crickets have traditionally been common edible insects, e.g., in Thailand, in Korea and in Mexico (Jongema 2017). If certain food contains more NPN than food in general, the universal nitrogen-to-protein conversion factor of 6.25 used in the Kjeldahl method can lead to overestimation of the calculated protein content. Janssen et al (2017) determined a nitrogen conversion factor of 4.76 in three insect larvae species. We have calculated nitrogen conversion factors for two crickets, Acheta domesticus and Gryllus bimaculatus, by analyzing their nitrogen and amino acid content
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