This research explores Isothermal Titration Calorimetry as a method for measuring beta-galactosidase activity directly and continuously in milk, sweet whey, sweet whey permeate, acid whey, and acid whey permeate. Beta-galactosidase in various concentrations was injected into each of the liquid dairy products spiked with lactose to verify if the heat rate from the enzymatic reaction could be observed. In addition, a consistent concentration of beta-galactosidase was injected into various concentrations of lactose in the products, to observe the heat rates from the enzymatic reaction. There was exothermic activity that never returned to baseline demonstrated in milk, sweet whey, and sweet whey permeate with beta-galactosidase from Kluyveromyces lactis in runs done in the isothermal titration calorimeter. The baseline was approximately 3-9 uJ/s above the control's baseline at the end of the runs. The exothermic activity ranged from approximately 2-10 uJ/s and did not return to baseline when beta-galactosidase concentrations were varied and lactose concentrations remained the same. The exothermic heat rate was approximately 3-7 uJ/s when lactose concentrations were varied and enzyme concentrations remained the same. With runs with increasing lactose concentrations, there was no corresponding increase in the exothermal reaction indicating saturation of the enzyme. There was a short exothermic reaction(s), ranging from approximately 3-26 uJ/s, demonstrated when varying concentrations of beta-galactosidase from Aspergillus oryzae in acid whey and acid whey permeate were injected into a consistent concentration of lactose in acid whey and acid whey permeate. There was a pattern of increasing heat with increasing concentrations of enzyme, with some of these differences being statistically significant. There was also a short exothermic reaction(s), ranging from approximately 2-17 uJ/s, demonstrated when a consistent concentration of beta-galactosidase from Aspergillus oryzae was injected into varying concentrations of lactose. There was a pattern of increasing heat rate with increasing concentrations of lactose, with some of these differences being statistically significant. This research demonstrates that ITC is a useful method for measuring residual beta-galactosidase and/or residual lactose in liquid dairy products. This research leads to further understanding of how enzymes and substrates interact directly in the food matrix, rather than in an isolated environment.