Poster: Proteins and protein hydrolyzates - Structure and function - Odd
P. Gulati, D. Rose, University of Nebraska, Lincoln, NE, USA
Protein digestibility of proso millet flour has been shown to decline substantially upon cooking (raw flour: 80 ± 0.8%; cooked flour: 37 ± 1.5%). With the objective of preventing the decline in digestibility, various processing techniques (non-thermal and thermal) and the interaction of different solutes with millet proteins were tested. Millet flour was subjected to the following processing techniques: high pressure processing (200 MPa and 600MPa for 5 and 20 min); germination (48 h); fermentation (48 h); extrusion (17% moisture, 250 rpm, 115 °C); pan roasting over medium heat (dry heating); and autoclaving (121 °C, 2.5 h). To study the interaction of millet proteins with solutes, millet flour was heated with sucrose (3-7M); NaCl (2-6M); gums (guar (0.5%), xanthan (0.5%), acacia (15% w/v)); CaCl2 (0.5-3M); and ethanol (1 and 5%). Among all the mitigation strategies evaluated, only heating with kosmotropes, i.e. sucrose and NaCl, at high concentrations was found to be effective. Further analysis showed that the ability of kosmotropes to prevent the decline in protein digestibility of millet proteins was dependent on the water activity (aw) of their solutions. A negative correlation (r = -0.97) was observed between aw and protein digestibility of cooked millet flour, regardless of whether sucrose or NaCl were used. Millet flour was then cooked with honey (aw: 0.57) and maple syrup (aw: 0.85). Cooking with honey resulted in 83 ± 1.8% proteins being digested in millet flour while maple syrup was not very effective. Thus, cooking of millet flour with naturally low aw substances can be useful in promoting their consumption without a loss in digestibility.