Influence of maltodextrin addition to thermal stability of whey protein isolate / Nuraini Mohd Yusoff

Faculty of Chemical & Natural Resources Engineering

Project Paper (Master of Engineering (Bio-Process)) -- Universiti Malaysia Pahang – 2014

Bibliography : p. 94-108

This thesis presents a thermal denaturation study of whey protein isolate (WPI) with the presence of maltodextrin (MD) during heating experiment and spray drying. Heating experiment of whey protein isolate in a closed stainless steel tube for 30 minutes at temperature of 80 °C caused a 97.3% and 67.3% denaturation of β-lactoglobulin and α-lactalbumin, respectively. Arrhenius model provides a good fit to experimental data for both α-lac and β-lg denaturation with average error around 5.85% and 5.92%. Addition of maltodextrin improved the thermal stability of β-lactoglobulin and α-lactalbumin, by increasing its order of reaction from 1.5 to 3.5 and by reducing the rate constant of denaturation by two orders of magnitude from 10-4 to 10-6. Addition of maltodextrin reduces the thermal degradation of β-lactoglobulin and α-lactalbumin up to 12.52% and 14.14%, respectively. Formulation of 9:1 WPI to maltodextrin ratio was found to give a better thermal stability for both β-lactoglobulin and α-lactalbumin, compared to the 1:1 ratio. Addition of maltodextrin to WPI solution reduces protein denaturation during spray drying. The lowest protein denaturation (~4%) was observed when a higher wall to core ratio (1:9 WPI:MD) was used, implying the mechanism of encapsulation is a homogeneous matrix structure, instead of a big single core structure. For spray drying process the optimal operating conditions to minimise denaturation where 3% solid concentrations, a WPI:MD 1:9, a nozzle size of 1 mm, and inlet temperature 140 °C. The physical properties of spray dried powder were also affected by temperature, solid concentration, nozzle size and maltodextrin to WPI ratio. Increasing temperature from 140 °C to 190 °C increased the particle size from 8.59 to 9.57 µm, due to increase in particle surface evaporation rate. The particle size obtained from the formulation consisting a higher WPI content (WPI: MD 9:1) had a bigger diameter 9.74 µm as compared to the lower WPI content (WPI: MD 1:9) 7.36 µm. The mean particle size increased from 9.72 and 20.84 µm when the total solid content increased from 1.5 to 20 wt.% due to increases in solution viscosity. The powder mean diameters increased from 9.55 µm to 11.48 µm when the nozzle size diameter increases from 0.5 mm to 1.5 mm. Surface morphology of whey protein was affected mainly by the solid concentration and maltodextrin to WPI ratio.