Physicochemical properties of Eri pupae flakes and their antibacterial activity against Salmonella sp., Escherichia coli and Staphylococcus aureus

Abstract

Aims: The objective of this study was to evaluate the physicochemical properties of Eri silkworm ( Samia cynthia ricini ) pupae flour, specifically the pH value, water activity, water content, fat value, ash value and protein value. The study was also aimed to determine the antibacterial activity of Eri silkworm pupae flour against Salmonella sp., Escherichia coli and Staphylococcus aureus . Methodology and results: Pupae meal is a flour made from the extract of the Eri silkworm pupae used as a flour substitute in producing pupae flakes. Pupae meal had two particle size treatments, 60 and 80 mesh, whereas pupae flake had three pupae meal substitution treatments of 0%, 4% and 8%. The physicochemical properties, antioxidant activity and microbiology of pupae meal and flake were analyzed. The results showed that Eri pupae flour met the Indonesia National Standard for Cereals (SNI 01-4270-1996) requirements for food ingredients regarding pH value, water activity, water content, fat value and protein value. The flour also exhibited antibacterial activity against all three bacterial species tested, with S. aureus being the most susceptible. Antioxidant activity and capacity increased as the percentage of pupae meal in the pupae flakes increased. The IC 50 value of pupae meal, 68 µg/mL, was included in the strong category. Salmonella sp. were not found in the pupae meal and flake. Total plate count, E. coli and S. aureus numbers remained within food tolerance limits based on the Indonesia National Standard in both pupae flour and pupae flakes. Conclusion, significance and impact of study: The particle size of pupae flour did not affect its physicochemical properties or antioxidant activity, and microbiologically, it met the Indonesia National Standard for flour. Moreover, The flakes product with pupae flour substitution influenced its physicochemical properties, with the best level at 8% pupae flour for the highest protein content and increased the flakes product's activity and antioxidant capacity. Based on the microbiological analysis of pupa flakes products, The microbial content in the pupa was still within safe limits for human consumption. Research findings suggest that pupae flakes are in accordance with the Indonesia National Standard for Cereal and are a good alternative as a functional food.