Author

Brienne Boss

Date of Award

8-2011

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Food Science and Human Nutrition

Advisor

Mary Ellen Camire

Second Committee Member

Denise Skonberg

Third Committee Member

Beth Calder

Abstract

Blue cornmeal is a natural source of anthocyanins, which are water-soluble pigments responsible for the vibrant colors of fruits, vegetables and cereal grains. These pigments are known for their numerous health benefits which include antioxidant activity, anti-inflammatory activity, anti-cancer properties, and cardiovascular disease protection. Anthocyanins are heat-labile, thus, materials 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°C or 165°C) and 18, 21, or 24% feed moisture. Extrudates were characterized by anthocyanins (ANC), total free phenolics (TFP), antioxidant capacity (AOX), physical properties, and sensory acceptability by 100 consumers. Data were analyzed using 2-way ANOVA or General Linear Model (p ≤ 0.05) with rosemary level and processing or temperature and feed moisture as the independent variables. Three levels of rosemary were added to raw cornmeal (0, 0.1, 0.3%) to improve ANC retention. The effect of convection drying was also evaluated. Extrusion at 150°C and 21% moisture and 165°C and 24% moisture resulted in the highest ANC, TFP, and AOX. Drying decreased anthocyanins 23-46%. In undried samples rosemary increased ANC retention by 17%. However, there were no differences in free phenolics among levels of rosemary. Drying darkened the puffs further but did not impact blue hues on the CIE color scale. Lower temperatures and moisture in extrusion resulted in more blue color. Dried blue cornmeal puffs with 0.3% rosemary and extruded with low temperature and high moisture had significantly more acceptable color and appearance, with score mean values of 7.3 and 7.0 (9 being like extremely). 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.

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