Many fruit juices contain ultraviolet absorbing phenolic substances. The uv-vis absorbance spectrum of an alcohol clarified solution of orange juice is shown in Figure 10. Absorbances at the key wavelengths 280, 325 and 443 nm, due to flavanoids, psoralins and carotenoids respectively, can be used to detect dilution of orange juice with sugar. The sum of these absorbances is typically in the range of 2.0-3.0. Reduced absorbance sums can indicate dilution of the juice.
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