Abstract
As a representative edible insect, Tenebrio molitor is rich in chitin, making it an important natural resource for chitosan production. This study established a dual-frequency ultrasound-assisted enzymatic method for green and efficient extraction of chitosan from T. molitor and evaluated its functional properties and preservation efficacy on germ-retained rice. The optimized conditions were: dual-frequency ultrasound (20 kHz +28 kHz, 120 W), deproteinization (12% enzyme, 2 h, 55 °C, solid-liquid ratio 1:15), demineralization (15% citric acid, 1 h, 45 °C, 1:10), and deacetylation (35% NaOH, 7 h, 90 °C, 1:20). Under these conditions, the chitosan yield reached 63.15%, with a deacetylation degree of 94.46%, solubility of 97.24%, and molecular weight of 1.12 × 104 kDa. Compared with the enzymatic method, dual-frequency ultrasound assistance increased yield by 14.18%, degree of deacetylation (DD) by 18.00%, solubility by 6.4%, and reduced molecular weight by 1.568 × 105 kDa, while also significantly enhancing antioxidant and antibacterial activities. The extracted chitosan extended the shelf life of germ-retained rice by more than 7 days, by inhibiting lipid degradation (reduced lipase and lipoxygenase activities, fatty acid value, and malondialdehyde), mitigating starch aging (maintained α-/β-amylase activities), and preserving protein content. This study demonstrates that the dual-frequency ultrasound-assisted enzymatic method is an efficient and green approach for chitosan extraction, and T. molitor chitosan is a promising natural preservative for food applications.
•Green and sustainable extraction of Tenebrio molitor chitosan using dual-frequency ultrasound-enzymatic method.•Optimized process achieves 63.15% chitosan yield and 94.46% deacetylation degree.•Tenebrio molitor chitosan shows excellent antioxidant and antibacterial activities.•Tenebrio molitor chitosan significantly extends germinated brown rice shelf life by over 7 days.•Provides a green, efficient chitosan production and natural food preservation, supporting edible insect valorization.
