Abstract:

Objective The global trade of substandard feather and down products, particularly those subjected to inadequate washing processes, poses significant challenges to customs inspection and epidemic prevention. Existing standards like GB/T 17685—2016 fail to address the identification of these substandard products, which lack sufficient hygiene and structural stability. This study aimed to establish a rapid, reliable detection method based on differential scanning calorimetry (DSC) to distinguish unwashed and inadequately washed feather and down by characterizing heat-induced keratin conformational changes, thereby providing technical support for regulatory standard revisions.

Method Thermogravimetry (TG), X-Ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) were employed to compare the thermal stability of feather and down samples. For sample preparation, unwashed samples (white/grey duck feather and down) were subjected to natural air-drying or heat treatments (80-160 ℃ for 30 min). TG was employed to quantify the mass loss across 30-800 ℃ (10 ℃/min, N₂ atmosphere) for unwashed and heat-treated (80-160 ℃, 30 min) white/grey duck feather/down. XRD (5°-25°, 5(°)/min) and FT-IR (4 000-400 cm^-1, 4 cm^-1 resolution) results were examined to analyze the crystal structure evolution and secondary structural transitions (β-sheet, α-helix, random loops). As the core technique for capturing thermal behavior details, DSC (5 ℃/min to 550 ℃, N₂ flow) played a critical role in establishing distinct thermal fingerprints for all 24 sample groups (4 types and 6 treatments), focusing on endothermic peak variations correlated with keratin denaturation. Data were processed using NETZSCH Proteus and Origin 2022, with statistical validation of structural parameters.

Results TG analysis revealed three-phase decomposition of feather and down, which are moisture evapora-tion (30-200 ℃), keratin degradation (200-400 ℃), and residual decomposition (400-800° C). For structural transitions, XRD revealed that 120 ℃ treatment increased α-helix and β-sheet diffraction intensity in white feather, while 160 ℃ reduced α-helix and β-sheet peaks in grey feather. FT-IR deconvolution showed that inadequate washing elevated β-sheet content and eliminated random loops, confirming molecular rearrangement into stable hydrogen-bonded networks. DSC results indicated that unwashed samples exhibited broad moisture evaporation peaks at (83.2-91.7)℃. After heat treatment, peak positions shifted or disappeared. 80-140 ℃ treatments induced distinct β-sheet denaturation peaks within 170-220 ℃. Specifically, 160 ℃ treatment caused structural disorder, reducing enthalpy and peak broadening. Meanwhile, grey feather displayed similar trends but varied in peak intensity due to structural differences.

Conclusion In this study, the thermochemical properties of inadequately washed and unwashed feather/down were investigated through TG, XRD, FT-IR, and DSC analysis. The study concluded that heat treatment is a key factor affecting the thermal properties of down keratin. The DSC results showed that the DSC curves of inadequately washed and unwashed feather/down are different, and unwashed and inadequately washed feather/down can be distinguished by the characteristic peaks on the DSC curves. The DSC method effectively distinguishes unwashed and inadequately washed feather/down based on thermal transition differences. This method requires minimal sample preparation (10 mg) and provides results within 1 h, offering a rapid and reliable solution for customs inspection and quality control. The findings support the revision of GB/T 17685—2016 to include thermal analysis criteria, enhancing the regulation of substandard products in the global down industry.

Key words: inadequately washed feather and down, unwashed feather and down, differential scanning calorimetry, keratin structure of feather and down, down