Methods for estimating the chitin content of edible insects: Advantages and challenges

The proper assessment of the nutritional value of insects requires an accurate estimation of their chitin content. Conventional methods are based on recovery and gravimetric determination of chitin; despite its common use, however, this approach fails to provide a reliable approximation of the actual chitin content. Indeed, structural and physicochemical characterization of the extracted chitin usually reveals the presence of impurities, resulting in e.g. a C/N ratio significantly different from that of pure chitin (6.86) or a degree of deacetylation >100 %. Alternative analytical methods to estimate insect chitin include indirect measurement via estimation of the fiber content and spectrometric methods for the estimation of D-glucosamine. The present review aims to provide a critical discussion of these methods while discussing their advantages and limitations. A comprehensive evaluation of these methods was performed based on their selectivity, accuracy, requirements in time and lab infrastructure and applicability to a variety of insect species and insect-based products. Spectrometric methods, which exhibit high accuracy and selectivity were selected as the most appropriate, with chromatography improving their accuracy. Indirect methods based on the estimation of fibers and acetate were discouraged as they exhibit lower selectivity, although their lab requirements are significantly lower.