Impact of drying method on the nutritional value of the edible insect protein from black soldier fly (Hermetia illucens L.) larvae: amino acid composition, nutritional value evaluation, in vitro digestibility, and thermal properties

Abstract

Black soldier fly (BSF, Hermetia illucens L.), an insect with high protein, has been proposed as a sustainable protein resource alternative for both food and feed for their nutritional composition and ease of rearing. The amino acid composition, nutritional value, in vitro digestibility, morphologies, and thermal properties of the BSF larvae proteins (BSFLP) based on two drying methods were investigated. Experimental results showed that their amino acid score could reach the requirement of FAO/WHO (dietary protein quality evaluation in human nutrition. Report of an FAO expert consultation. Food and nutrition paper no. 92. Food and Agriculture Organization and the World Health Organization, Rome, 2013) for indispensable amino acids for older children, adolescents, and adults. The proportion of essential amino acids to total amino acids (E/T) of both conventional dried BSFLP (CD-BSFLP) and microwave dried BSFLP (MD-BSFLP) was more than 40%. Lysine and valine were found to be the first limiting amino acid for CD-BSFLP and MD-BSFLP, respectively. Both of the in vitro digestible indispensable amino acid score (DIAAS) values of the BSFLP were more than 75%. The results of scanning electron microscopy, thermo-gravimetric analysis, and differential scanning calorimetry of the samples showed that microwave drying polymerized the protein particles and made them harder to digest. In conclusion, the BSFLP prepared by conventional drying (60 °C) had higher DIAAS and better digestibility. Moreover, the amino acid composition and high DIAAS (> 75%) indicated that the BSFLP could be utilized as a good source of animal protein for human nutrition.