Predicting whey's functional properties through synchronous front-face fluorescence spectroscopy

Whey is widely used across various food industries, and its functional properties are critical for product quality and consumer acceptance. The current study aimed to assess the feasibility of using front-face fluorescence spectroscopy (FFF) as a nondestructive technique to predict the technological functionality of whey, particularly its foaming, gel-forming, and emulsifying capabilities. Heat treatments were applied on reconstituted skim milk enriched with whey protein isolated (80°C with 7 holding times) to induce variability in all the studied functional properties. Then, whey samples were obtained by isoelectric precipitation of caseins from enriched milk. Synchronous FFF of whey was measured at an excitation of 250 to 550 nm (λ₀ = 20 nm and Δλ = 10 nm, where λ₀ = initial delta marks the first emission scan at a specific excitation; because the excitation was set at 250 nm, the first emission was at 270 nm. Δλ = delta increment is the change in wavelength for each subsequent scan). Excitation and emission wavelengths and maximum intensities were collected for 10 areas. These FFF parameters and their mathematical transformations were used in the maximum R² procedure of SAS software (version 9.4, SAS Institute Inc.) to select the predictors and obtain the best models, which were cross-validated. Excellent prediction models (R² > 0.95, ratio of performance deviation [RPD] >4) were obtained for gel-forming and emulsifying properties. However, for foam properties, the obtained models were successful for foam overrun (0.90 ≤ R² ≤ 0.95, 3 ≤ RPD ≤4) and moderately successful (0.80 ≤ R² < 0.90, 2.25 ≤ RPD <3) for foam stability. This research demonstrated that FFF spectroscopy has the potential to become a method for assessing whey functional properties, leading to improved industry process control and new products.