Structural and physicochemical changes due to proteolytic deterioration of escamoles (Liometopum apiculatum) a traditional Mexican food

Abstract

Entomophagy or consumption of insects has significantly increased worldwide, either for pleasure or to satisfy the food needs in developing countries. There are approximately 2,000 species of edible insects distributed in 120 countries. From these 2,000 species, about 540 are located in Mexico; one of the most consumed are the escamoles. Escamoles are larvae and pupae of the ant Liometopum apiculatum. Escamoles are nutritious because of their high content of protein, fat, carbohydrates and vitamin. However, during storage the quality of escamoles changes rapidly which affects the acceptability by the consumer. This loss of quality is probably a result of proteolytic activity of endogenous proteases. Therefore, the objectives of this study were to identify the classes of proteases in escamoles as well as to evaluate the effect of proteolytic activity on physicochemical and structural changes during storage. Proteases identification was conducted using specific inhibitors; structural changes, texture, and proteolytic activity were monitored at different days of storage. The highest proteolytic activities (P<0.05) were observed at pH 8, 9 and 10 and at 37 and 50 °C. Proteases were mainly inhibited by iodoacetic acid and soybean trypsin inhibitor showing that cysteine and serine proteases were dominant. High proteolytic activity, significant (P<0.05) reduction in texture and weight loss was observed during storage. The deterioration of escamoles was evident in analyses of images, where initial structure was lost during storage. These results indicate that different groups of proteases are associated with rapid deterioration of escamoles.