A Novel Method of Multiparameter Spectrophotometry for Composition Analysis of and Bacterial Detection in Milk

Multiparameter spectrophotometry (MPS) provides a powerful and environmental-friendly tool for the characterization of turbid materials, including foods, without additives. The existing methods of MPS, however, lack either modeling accuracy or capacity for translation into ease-of-use instrument. We have developed a novel method of MPS to rapidly retrieve the spectral data of absorption coefficient, scattering coefficient, and anisotropy factor within the framework of radiative transfer (RT) theory without using integrating spheres. To demonstrate the feasibility of our MPS method for food analysis, the RT parameters have been determined between 500 and 1000 nm for four types of milk samples and skim milk samples spiked with either Lactobacillus acidophilus (L. acid.) or DH<inline-formula> <tex-math notation="LaTeX">$5\alpha $ </tex-math></inline-formula> Escherichia coli (E. coli) bacteria. The spectral data have been shown to agree with the published results on milk composition. We have also found the threshold of number density for the detection of E. coli in skim milk to be about <inline-formula> <tex-math notation="LaTeX">$2\times 10^{4}$ </tex-math></inline-formula> (mm−3). These results show clearly the potential of the presented method for the development of accurate, ease-of-use, and cost-effective instrument for routine analysis of turbid materials by MPS.