•The novel sulphonic aromatic acid structure overcomes long-standing salt pollution in conventional pickling process.•The novel process completely avoids the using of sodium chloride in conventional pickling.•The chromium absorption rate is increased from 71.6% to 98.6%.•The chromium contents in spent tanned liquors is dropped to 45.1 mg/L.•The costs of novel process far less than conventional process, and the rate of costs reduction close by 47%.Large discharge of chromium and chloride is a severe pollution source in conventional leather-making industry, which hinders the sustainable development of leather industry and affects human life greatly. Aiming at minimizing the emissions of chromium and chloride, novel materials rich in sulfonic acid group were synthesized and optimized in salt-free pickling and less chrome tanning process. The results showed that, the novel method would improve the chromium absorption and distribution in crust leather from 71.6% to 98.6%, in comparison with conventional pickling chrome tanning, and the concentration of residual chromium in spent liquor was decreased to 45 mg/L. The SEM indicated that the resulting leather treated with novel salt-free pickling showed clean pores and well-dispersed fibrils. Further experiment proved this novel salt-free pickling and less chrome tanning method is feasible in terms of organoleptic and physical mechanical properties. The financial assessment showed that the novel method is 46.9% cheaper than conventional approach. This novel pickling chrome tanning method can successfully solve the emission of chromium and chloride as well as obtain cleaner products in leather-making industry.

•Functional sturgeon skin gelatine bioactive film incorporated with esculine was developed.•Tensile strength and UV light-barrier increased but did not significantly alter films’ thickness.•The prepared films exhibited excellent antioxidant activity.•SEM and FTIR revealed a smooth, homogeneous surface and compact structure.Bioactive film from sturgeon skin gelatine incorporated with esculine at various concentrations (0.3%, 0.6% and 0.9% w/v) was developed. The physical, mechanical and antioxidant properties of esculine sturgeon gelatine biocomposite films were investigated. The results indicated that the incorporation of esculine into gelatine films significantly increased the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging activity and reducing power in a concentration-dependent manner (p < 0.05). In terms of physical properties, films incorporated with esculine exhibited higher tensile strength (TS) and lower elongation at break (EAB) with increasing concentrations of esculine, but there was no difference in thickness compared with the control film (p > 0.05). Water vapour permeability (WVP) and solubility of esculine-containing films decreased as the amount of esculine increased (p < 0.05). Decreases in L-value and increases in b-, ΔE- and transparency values were observed when increasing amounts of esculine were added (p < 0.05). A smooth and homogeneous surface and a compact-structure were observed for the films. The present research revealed that the addition of esculine to gelatine film can be used as food and drug packaging materials for long-term preservation purposes.An edible sturgeon skin gelatine film incorporated with esculine was developed. In the present study, three different types of films with different concentrations of esculine (0.3%, 0.6% and 0.9% w/v) were investigated for their physico-mechanical and antioxidant properties. The results revealed higher antioxidant activity and better physico-mechanical characteristics for the sturgeon gelatine biocomposite films compared to the blank control. Therefore, esculine-incorporated sturgeon skin gelatine film may serve as a bioactive material that can be widely used in food packaging and pharmaceutical capsules.Download high-res image (170KB)Download full-size image