Tryptophan front-face fluorescence and functional properties of whey: A preliminary study

This study investigated the potential of front-face fluorescence spectroscopy to predict the functional properties of whey. Whey has a commercial interest due to its excellent nutritional value and versatile functional properties. However, its attributes depend dramatically on heat treatment, which may alter its suitability for different food applications. Tryptophan front-face fluorescence of whey and its functional properties, i.e., foaming, gel-forming, and emulsifying properties, were evaluated after milk heat treatment (at 80 °C with seven holding times) to detect correlations between tryptophan fluorescence and functional parameters and generate predictive models. Whey samples were obtained by isoelectric precipitation of caseins from reconstituted skim milk powder enriched with whey protein isolate. As expected, heat treatments induced an increase in whey protein denaturation, as well as a decrease in total whey protein concentration and tryptophan fluorescence intensity. Gel-forming and emulsifying properties of whey significantly correlated with the maximum intensity of tryptophan (P < 0.001). Concerning foaming properties, only the foam stability index revealed a weak correlation with tryptophan maximum intensity (P < 0.05). Consequently, models presented strong significances (P < 0.001). Specifically, using only tryptophan fluorescence allowed successful prediction of emulsifying properties but was not enough for foaming and gel forming properties.