Light backscatter of milk products for transition sensing using optical fibers

Transition sensors are needed, particularly in the dairy industry, for dete cting transitions in pipe flow systems from product-to-water or product-to- product (such as from chocolate to vanilla ice cream mix). Transition infor mation is used to automatically sequence valves to minimize product waste. Optical fibers were used to measure light backscatter between 400 and 950 n m as a function of milk concentration in water and milkfat concentration in milk. The normalized response (100% for product and 0% for water) as a fun ction of product concentration in water was approximately logarithmic for s kim milk between 400 and 900 nm and approximately linear for milk containin g 1, 2, and 3.2% milkfat. The backscatter ratio (response relative to that for skim milk) as a function of milkfat in milk was wavelength dependent wi th longer wavelengths being more sensitive. The backscatter ratio at 900 nm for milk containing 3.2% homogenized fat was nearly four times that for sk im milk. Backscatter ratio saturated (minimal response with increased milkf at) at 8% milkfat for homogenized cream and 16% milkfat for unhomogenized c ream. Light backscatter for near infrared wavelengths around 900 nm was fou nd ideally suited for transition sensing of dairy products and was found pa rticularly sensitive to milkfat content. Light backscatter was found less s uitable for discriminating between high milkfat products.