Bio-Based Lac Dyeing and Functional Finishing of Silk Using Pineapple Core Extract and Genipin-Crosslinked Cricket Protein

This study developed a bio-based approach for the natural dyeing and functional finishing of silk fabrics using pineapple core extract, lac dye, and cricket protein crosslinked with genipin (CP—GP). Pineapple core extract was used to provide an acidic dyeing environment (pH 4) favorable for the adsorption of lac dye onto silk, while CP—GP was subsequently applied as a post-treatment to improve dye durability and functional performance. Lac dyeing was conducted at 80 °C for 60 min using 10% owf. lac dye and a liquor ratio of 1:30. Post-treatment with CP—GP altered the color of the lac-dyed silk from reddish to bluish-purple, with the highest color strength (K/S = 5.31 ± 0.21) obtained at 1% CP—GP. Washing fastness remained good to excellent after treatment, while improved resistance to color change under acidic and alkaline perspiration conditions was observed for the CP—GP-treated fabrics. The treatment also enhanced UV protection, with all CP—GP-treated samples achieving UPF 50+ under both dry and wet conditions. FTIR and SEM–EDS analyses supported modification of the silk fiber surface following CP—GP treatment, and a gel content of 81.28 ± 1.23% indicated the formation of a stable crosslinked protein network. However, CP—GP treatment reduced light fastness, indicating a limitation associated with the color-forming crosslinked system. Overall, the combined use of pineapple core extract, lac dye, and CP—GP provides a promising bio-based strategy for producing multifunctional silk textiles while reducing reliance on conventional metal-based mordants.