Influence of thermo-mechanical treatment and skim milk components on the swelling behavior and rheological properties of starch suspensions

This study focused on the thermal behavior of starch with and without milk proteins. The effects of two thermo-mechanical treatments: at laboratory and pilot scales were studied. Three media were used for starch pasting: NaCl aqueous solution, milk permeate and skim milk. Starch granules significantly swelled more when pasted in the pilot plant or during a longer time of thermo-mechanical treatment at laboratory scale. Moreover, whereas at laboratory scale the presence of lactose or milk proteins did not modify the swelling behavior of starch, a larger increase was obtained in presence of lactose (milk permeate) and milk proteins (skim milk) at pilot scale. At least, different dependence on starch granules diameter ratio versus relative viscosities were obtained at laboratory and pilot scales. Two complementary hypotheses on milk proteins/starch interactions were proposed to explain these results. Indeed, milk proteins could impact starch swelling through an increase of starch granules frictions during thermo-mechanical treatment but also through a modification of their surface characteristics.