Abstract #W142

# W142
Improved heat stability of whey protein isolate by dry-heating with inulin.
Yue He1, Bongkosh Vardhanabhuti*1, 1University of Missouri, Columbia, MO.

Dry-heating whey protein with reducing saccharides via Maillard reaction has been shown to improve heat stability. Selecting proper saccharides that offer technological and nutritional benefits could create new protein ingredients that have better functional properties and are more attractive to the consumers. The aim of this study was to develop heat stable whey protein ingredients by dry-heating with inulin, a non-digestible carbohydrate with known health and technological benefits. The effects of biopolymer ratio and heating conditions on heat stability, physicochemical properties, and nutritional qualities of the conjugates were determined. Whey protein isolate (WPI) and inulin at weight ratios of 1:1 to 6:1 were dissolved in deionized water, freeze-dried, and incubated at 70 to 80°C for 12 – 72 h without or with controlled relative humidity (RH) at 44 or 80%. Heat stability was measured by heating 6% w/w protein solutions, pH 6.0 at 85°C for 15 min and the absorbance was measured at 630 nm. Particle size, zeta potential, rheological properties, and lysine content were determined. WPI or mixed WPI-inulin (no dry-heating) turned very opaque after heating. Dry-heating of WPI-inulin clearly increased heat stability as shown by a significant reduction (P < 0.05) in turbidity (e.g., from A630 of 1.9 for WPI control to 0.8 for 12 h dry-heated 6:1 WPI-inulin) and particle size (from 160 nm in z-average diameter to 107 nm). Decreasing WPI:inulin weight ratio and increasing dry-heating temperature, incubation time, as well as RH resulted in increased heat stability; however, brown color intensity also increased. Rheological analysis revealed that all samples maintained Newtonian behavior with no significant difference in flow behavior index and consistency index. Dry-heated WPI-inulin had higher surface charge compared with WPI. The loss of lysine content ranged from 2.6% in 6:1 WPI-inulin after 12 h dry-heating to 19.2% in 2:1 WPI-inulin after 72 h dry-heating. In conclusion, dry-heating WPI with inulin creates new ingredient with improved heat stability. The new ingredient has great potential to be used in high protein beverages or other applications that require heat stability.

Key Words: whey protein, inulin, heat stability