88-10 |
Modeling the effects of extrusion cooking on the degradation of anthocyanins |
K. P. LAI1, K. D. Dolan2, and P. K. W. Ng2. (1) Dept. of Agricultural Engineering, Michigan State Univ., 208 G. Malcolm Trout FSHN Bldg., East Lansing, MI 48824-1224, (2) Dept. of Food Science & Human Nutrition/Dept. of Agricultural Engineering, Michigan State Univ., 208 G. Malcolm Trout FSHN Bldg., East Lansing, MI 48824-1224 Anthocyanins are natural color pigments important due to their health benefits and can be potential functional ingredients in processed foods such as extruded products. Although it is known that anthocyanins are temperature-sensitive, few studies have investigated the effects of shear on anthocyanin stability during extrusion. The objectives of this research were to quantify and model the separate thermal and mechanical effects of extrusion cooking on anthocyanin stability. Grape pomace (anthocyanin source) mixed with wheat pastry flour (1/3 w/w) was extruded at screw speeds of 50, 100, 200, and 400 rpm and dough moisture content of 30%, at both 110° C and 125° C die temperatures. Thermal effect was investigated separately (non-isothermally) by heating the mixture in steel cells in an oil bath at 80, 105 and 145° C. Anthocyanins were extracted using acidified ethanol. Absorbance values of the extract at pH 1.0 and 4.5 were measured at 530 nm and 700 nm (corrected for light scattering). Total monomeric anthocyanins were expressed as the difference in absorbance between the two pH samples. Data from the nonisothermal study were analyzed using nonlinear regression. Anthocyanin degradation was modeled as a first-order reaction with a rate constant of 0.006 min-1 at 80° C and an activation energy of 73.280 kJ (gmol)-1. Results from extrusion at all screw speeds displayed an overall 26-38% anthocyanin loss at 110° C die temperature and 31-50% loss at 125° C die temperature. Results at 125° C die temperature showed anthocyanin loss from mechanical effects increased from 15% to 30% with increasing screw speed while that from thermal effects decreased from 30% to 10%. The results from this study indicate that a model has potential for use in predicting anthocyanin loss in extrusion. This type of predictive model can save industry time and money when developing nutraceutical products.
Session 88, Nutraceuticals & Functional Foods: General
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