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 characterization of turbid materials including foods without additives. 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 4 types of milk samples and skim milk samples spiked with either Lactobacillus acidophilus (L. acid.) or DH5α Escherichia coli (E. coli) bacteria. The spectral data has been shown to agree with the published results on milk composition. We have also found the threshold of number density for detection of E. coli in skim milk to be about 2x10 ⁴ (mm ^-3 ). These results show clearly the potential of the presented method for development of accurate, ease-of-use and cost-effective instrument for routine analysis of turbid materials by MPS.