New methods for high-accuracy insect chitin measurement

Background: There is a growing interest in the use of insects in poultry, swine and aquaculture feed, as well as pet food applications. All insects produce chitin-based exoskeletons. With regard to chitin content, a precise determination in agricultural applications is crucial because it has favorable functional properties, although it is also difficult to digest for some species of livestock. Three measurement methods were compared to determine the most reliable method of chitin content determination in different insects and selected Hermetia illucens products: acid detergent fiber (ADF) provides the fiber content and the acid detergent lignin (ADL) additionally considers the catecholic compounds. Acetyl group measurement relates the acetate content to the chitin content. Results: Comparing different insect species, the highest chitin value via ADF measurement was determined for the Tenebrio molitor larvae (155 g kg-1). Chitin values higher than 200 g kg-1 revealed that H. illucens residues are a much better valuable source of chitin. For the larval exoskeletons, a chitin content for all measurement methods of more than 350 g kg-1 was determined. In general, the ADF measurement is approximately 5% higher than the ADF-ADL and acetyl measurements. ADF-ADL and acetyl group determinations are approximately equivalent measurement methods. Conclusion: According to statistical analysis, ADF-ADL represents a compromise between accuracy and equipment demand and is a suitable method for determining the chitin content of both insects and their residues.