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Retention of anthocyanins, phenolics, and antioxidant activity during blue corn extrusion.

M. CAMIRE (1), B. Boss (1), M. P. Dougherty (1), B. Perkins (1), B. Kim (1)
(1) University of Maine, Orono, ME, U.S.A.
Cereal Foods World 56:A17
http://dx.doi.org/10.1094/CPLEX-2011-1004-05W

Blue cornmeal is a natural source of anthocyanin water-soluble pigments. Consumption of these pigments aids health through antioxidant and anti-inflammatory activity and protection against chronic diseases. Anthocyanins are heat labile so foods containing anthocyanins are difficult to extrusion-cook for puffed snacks or breakfast cereals. Blue cornmeal was twin-screw extruded to obtain puffs with optimal anthocyanin content. Extrusion parameters included maximum barrel temperature (150 or 165°C) and 18, 21, or 24% feed moisture. Extrudates were characterized for total anthocyanins (ANC), total free phenolics (TFP), oxygen radical absorbance capacity (ORAC), physical properties, and sensory acceptability by 100 consumers using a 9-point hedonic scale. Data were analyzed by ANOVA with Tukey’s test (p ≤ 0.05). Three levels of rosemary extract were added to raw cornmeal (0, 0.1, 0.3% w/w) to improve ANC retention in one experiment; the effect of convection drying extrudates was also evaluated. Extrusion at 150°C & 21% moisture and at 165°C & 24% moisture resulted in the highest ANC, TFP, and AOX levels. Drying decreased anthocyanins 23–46%; rosemary addition had no effect. HPLC-MS revealed new anthocyanin-phenolic complexes were formed during extrusion. Drying darkened the puffs further but did not impact blue hues on the Hunter color scale. Lower temperatures and moisture in extrusion resulted in more blue color. Dried blue cornmeal puffs with 0.3% rosemary and extruded at 150°C & 24% moisture had significantly more acceptable color (7.3) and appearance (7.0) than other samples. Increased understanding of the fate of anthocyanins during extrusion cooking will lead to improved processing techniques for retaining these phytochemicals for their appearance and health benefits.