Abstract

A method and calibration for estimating sulphur (S) concentration in wool using near infrared reflectance spectrometry (NIRS) is described. The NIRS measurements were calibrated against wet chemistry determinations of wool S (R² = 0.81, relative standard error ± 3.7%, n=339). The first derivative spectra with 14 partial least squares terms gave the lowest cross-validation error for the calibration using an independent set of wool samples (R² = 0.78, cross-validation error ± 0.11, n=66, mean 2.88 g S/100g wool). The correlation spectrum gave a series of approximately equally weighted peaks from about 1300 - 2400 nm, corresponding to -NH stretching and bending modes (protein). The -SH absorption between 1736 and 1746 nm could also be identified. Although scouring differences contributed to marked spectral differences in the visible region (yellowness was related to the first 3 principal component scores) these did not affect the overall S calibration. Uses for the calibration include wool S as an indicator of lifetime wool production, changes in wool composition in response to supplemented cysteine or energy intake, and the relationship between wool S and wool characteristics.

DC, Corson, W Martin, and J Lee

Proceedings of the New Zealand Society of Animal Production, Volume 58, , 281-283, 1998