Differences in moisture sorption characteristics and browning of lesser mealworm (Alphitobius diaperinus) ingredients

Lesser mealworm (Alphitobius diaperinus) is an insect species that can be reared on an industrial scale for human consumption. In this study, the hydration behavior of processed lesser mealworm food ingredients (whole powder, protein concentrate, textured protein) was analyzed in comparison to whey protein concentrate and tofu. Moisture adsorption isotherms were determined gravimetrically over 0.11–0.96 water activity range at 5 and 20 °C, and seven sorption models were applied to fit the experimental data. The Guggenheim-Anderson-de Boer model performed best on the isotherms of all studied samples. The determined adsorption isotherms were type III according to Brunauer classification. Mealworm protein concentrate presented the strongest hydration capacity at 20 °C, followed by whey protein concentrate and whole mealworm powder. Textured mealworm protein and tofu exhibited similar hydration behavior at 5 °C. Moreover, browning and agglomeration of mealworm protein concentrate powder were observed at water activities of 0.73 and higher, which can be explained by its composition and porous structure and were not typical for whey protein concentrate. The moisture adsorption results are important for the prediction of lesser mealworm ingredients shelf-life or prevention of undesirable quality changes during storage, but more research on microbial growth and sensory quality is needed.