The objective of this study was to obtain starch and fiber enriched oatmeal fractions through sieving, chemically modifying (phosphorylation) the starch enriched fraction, and evaluating its functional properties. Fractionation was performed using > 300, 212-300, 150-212, and < 150 µm sieve. Fractions > 300 µm and 212-300 µm were similar and had increased protein and fiber content (1.5 and 2.7 fold), but reduced starch content (0.5-0.6 fold) when compared to whole oatmeal. Fractions 212-150 µm and < 150 µm were similar and had the highest starch content (around 70%). The starch-rich fraction < 150 µm that had the highest yield during sieving (35.5%) was phosphorylated with sodium tripolyphosphate at 150-155 °C for 20 and 40 min, yielding 0.39 and 0.32% phosphorus bound, respectively. Cold water binding capacity increased (1.9-3.3 fold), while syneresis at 5 °C or after freezing/thawing was significantly reduced (6-20 and 5-6 fold, respectively) in phosphorylated starch fraction when compared to the native starch fraction. Phosphorylation reduced the increase of pasta opacity during storage at 5 °C, which indicates a lower retrogradation tendency. Thus, oatmeal sieving yielded fractions either enriched in fiber and protein or enriched in starch. Moreover, phosphorylation of the starch-rich fraction improved their functional properties, which may increase the potential applicability and economic value of this fraction in the food industry.
oat starch; sieving; starch phosphate monoester; syneresis; cold water binding capacity
