Associate Professor Kitasato University Towada, Aomori, Japan
Objectives: Edible insects are increasingly recommended as alternative food resources to meet the nutritional needs. Edible insects contain protein, fat, and others. However, their nutritional properties are different among insect species because of differences in their life stages, foods, and living environment. In this study, nutritional properties of some edible insects (migratory locust (ML, adult), crickets (CRs, adult), and silkworm (SW, pupa)) were clarified.
Methods: Powdered insects (ML, CRs, SW) without excipients in a Japanese market were used. In lipid analyses, insect lipids were extracted by chloroform-methanol mixture (2:1) and triglyceride (TAG) and phospholipid (PL) fractions of each extract were enzymatically quantified. PLs were quantified by using PL type-specific enzymes. Fatty acid (FA) compositions of each lipid fraction were determined by thin-layer-chromatography and gas-chromatography analyses. In protein analyses, constructed amino acid (AA) composition of each insect powder was analyzed and each AA score was calculated by using the AA scoring pattern widely used. Furthermore, digestive properties of ML proteins were evaluated by the SDS-PAGE analyses in vitro and in vivo.
Results: Tested insect powders contained total lipids (145-423 mg/g dry powder), TAG (11-117), choline-binding PLs (17-35). ML and CRs contained high amounts of PLs as well as TAG, and SW contained high amounts of TAG. Particularly, PLs contented in edible insect powders were equal to or greater than those in conventional food materials such as soybean, fish, and meat. Phosphatidylcholine was dominant in total PLs in insect powders. Lipids in ML and SW consisted of n-3 linolenic acid, whereas lipids in CRs consisted of n-6 linoleic acid. Nutritional AA scores of ML, SW, and CRs were 63, 94, and 84-87, respectively, which were lower than those of conventional protein resources. Proteins from ML were resistant to pepsin digestion but can be digested by trypsin and pepsin-trypsin mixture (in vitro). Also in vivo, proteins from the ML could not be degraded in gut but could be degraded to smaller molecules in small intestines of rats.
Conclusions: Tested edible insect powders are appropriate for additional and functional food resources because polyunsaturated lipids and digestible proteins were contained.
