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Freeze stabilty enhancement of dairy emulsions by microparticulated whey protein
Dairy emulsions exist in many sauces used in frozen meals, commonly prepared with milk or commercially available milk protein ingredients. Dairy sauces are susceptible to instability due to high temperatures and freeze abuse, resulting in protein aggregation and coalescence of dispersed fat droplets. The objective of this work was to study microparticulated whey protein (MWP) influence on stability in frozen dairy emulsions by 1) developing freezing methodology to simulate freeze abuse conditions for comparing emulsion stability; 2) examining the influence of homogenization, heat treatment, and/or salt addition on the properties of MWP suspensions; and 3) investigating the influence of MWP and polysaccharide gums on the stability of milk protein concentrate (MPC) stabilized oil-in-water emulsions. We evaluated the influence of freezing rates on the microstructure, stability and physicochemical properties of model emulsion-based sauces. Slow freezing (-0.021 °C/min) resulted in a larger mean particle size than fast freezing (- 0.132 °C/min), attributed to increased fat droplet flocculation and coalescence. The influence of various additives (salt, sugar, gums) on the properties of the sauces was also investigated. Salt (200 mmol/L NaCl) promoted droplet flocculation and phase separation whereas 150 mmol/L sucrose inhibited droplet flocculation and phase separation. Xanthan gum (0.2%) promoted flocculation, but inhibited phase separation in slow frozen emulsions. Homogenization reduced MWP particle size, increasing the lightness and sedimentation stability of MWP suspensions. Thermal treatment (70 °C) of MWP suspensions with salt (100 mM NaCl) promoted particle aggregation and sedimentation, which is attributed to an increase in hydrophobic attraction. NaCl addition (0 to 300 mM; pH 7, 23 °C) promoted sedimentation in non-homogenized suspensions. The microstructure of non-homogenized MWP dispersions was consistent (pH 3-7) regardless of salt level and at the isoelectric point (∼ pH 4.25). The addition of MWP and polysaccharide gums into homogenized emulsions with MPC, improved the emulsion freeze-thaw stability as monitored by confocal fluorescence microscopy and laser diffraction. MWP addition to the emulsions reduced protein and droplet aggregation. Gums provided additional stability to freezing. A xanthan-guar mixture (1:1) was most effective. Optimal MWP, MPC and gum levels were established to improve the freeze stability of a commercial B´chamel sauce.
Degner, Brian M, "Freeze stabilty enhancement of dairy emulsions by microparticulated whey protein" (2013). ETD collection for University of Nebraska - Lincoln. AAI3603563.