A light backscatter technique using optical fibers to deliver and receive light was investigated for measuring the milkfat content of unhomogenized cream. Light backscatter through cream at wavelengths of 450 to 900 nm was measured for fiber separation distances from 2 to 6.5 mm and for cream containing 10 to ~40 weight percent (wt%) milkfat. Unhomogenized cream (~40 wt% milkfat) was mixed with skim milk (~0.05 wt% milkfat) to yield samples with five different milkfat levels. Three optical response models were tested for correlation with milkfat content: one using the light intensity measurement at a single separation distance, the second using the ratio of the light intensity at two distances, and a third using the light intensity as a function of separation distance based on the backscatter of light in a particulate solution. The calibration equations from all three methods were used to predict milkfat content in the evaluation samples with root mean square errors (RMSEs) of 1.5 to 2.0 wt%. Statistical analysis did not find a significant difference between the three methods. For simplicity, using the ratio of the intensities measured and two different separation distances is attractive for further sensor design.

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Published in Transactions of the ASAE, v. 45, issue 1, p. 171-176.

© 2002 American Society of Agricultural Engineers

The copyright holder has granted the permission for posting the article here.

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The financial support provided by USDA grant NRICGP 9801188 is greatly appreciated.

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The original paper (01–05–142) reports results of an investigation by the Kentucky Agricultural Experiment Station and is published with the approval of the Director.