Optothermal (OT) spectroscopy is a potential sample presentation technique for use in the near infrared (NIR). Compared to attenuated total reflectance (ATR) in the mid infrared region it offers the same advantages of ease of use but is not so sensitive to sample morphology. Using model mixtures we have shown that it provides better, linear calibrations for the fat content of milk than ATR, particularly when the fat globule size is not controlled. The potential for on-line stopped flow use is also demonstrated. We conclude OT to be a possible means of introducing NIR into the dairy and related industries.
