Rheological Behaviors of Lactose Hydrolyzed and Unhydrolyzed Skim Milk Concentrates and Reconstituted Powder Samples

Lactose hydrolyzed skim milk powder has the potential to become a staple value-added ingredient in snack and frozen foods because 70% of the population suffers from lactose intolerance. However, the flow behavior of lactose hydrolyzed skim milk concentrates and their resulting products need to be understood. The aim of this study was to compare two rheological modeling methods and determine which method is best for predicting rheological behavior in lactose hydrolyzed and unhydrolyzed skim milk concentrates and reconstituted powder samples. The two methods compared are the combined temperature-concentration multiple-linear regression model and the shear rate-temperature-concentration superposition principle master curve model. Prior to fitting the data to the two models, the effect of temperature was determined via the Arrhenius relationship and the effect of concentration was determined via the Exponential relationship. The combined temperature-concentration method resulted in a single logarithmic model for each concentrate type which yields the consistency coefficient at any temperature and concentration input. The master curve method resulted in a single Power law type model for each concentrate type that describes the overall rheological behavior of the samples. When the predicted consistency coefficients from each method were compared to the raw data, both the master curve (r = 0.973, P < 0.0001) and the combined (r = 0.940, P < 0.0001) methods showed a strong correlation to the raw data. When the results were examined by concentrate type, the master curve model had a stronger fit (P < 0.01) for the reconstituted samples compared to the combined model which did not show a statistically significant correlation to the raw data (P < 0.075). The results of this study indicate that the master curve method is superior for predicting the rheological behavior of concentrated milk samples prepared from varying methods within our tested ranges.