Confidence Intervals for Modeling Anthocyanin Retention in Grape Pomace during Nonisothermal Heating

Authors

  • D.K. Mishra,

    1. Authors Mishra and Dolan are with Dept. of Biosystems and Agricultural Engineering, Michigan State Univ., 219 Farrall Hall, East Lansing, MI 48824, U.S.A. Author Dolan is with Dept. of Food Science and Human Nutrition, Michigan State Univ., 135 Trout Food Science Building, East Lansing, MI 48824, U.S.A. Author Yang is with Dept. of Statistics and Probability, Michigan State Univ., East Lansing, MI 48824, U.S.A. Direct inquiries to author Dolan (E-mail: dolank@msu.edu).
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  • K.D. Dolan,

    1. Authors Mishra and Dolan are with Dept. of Biosystems and Agricultural Engineering, Michigan State Univ., 219 Farrall Hall, East Lansing, MI 48824, U.S.A. Author Dolan is with Dept. of Food Science and Human Nutrition, Michigan State Univ., 135 Trout Food Science Building, East Lansing, MI 48824, U.S.A. Author Yang is with Dept. of Statistics and Probability, Michigan State Univ., East Lansing, MI 48824, U.S.A. Direct inquiries to author Dolan (E-mail: dolank@msu.edu).
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  • L. Yang

    1. Authors Mishra and Dolan are with Dept. of Biosystems and Agricultural Engineering, Michigan State Univ., 219 Farrall Hall, East Lansing, MI 48824, U.S.A. Author Dolan is with Dept. of Food Science and Human Nutrition, Michigan State Univ., 135 Trout Food Science Building, East Lansing, MI 48824, U.S.A. Author Yang is with Dept. of Statistics and Probability, Michigan State Univ., East Lansing, MI 48824, U.S.A. Direct inquiries to author Dolan (E-mail: dolank@msu.edu).
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Abstract

ABSTRACT:  Degradation of nutraceuticals in low- and intermediate-moisture foods heated at high temperature (>100 °C) is difficult to model because of the nonisothermal condition. Isothermal experiments above 100 °C are difficult to design because they require high pressure and small sample size in sealed containers. Therefore, a nonisothermal method was developed to estimate the thermal degradation kinetic parameter of nutraceuticals and determine the confidence intervals for the parameters and the predicted Y (concentration). Grape pomace at 42% moisture content (wb) was heated in sealed 202 × 214 steel cans in a steam retort at 126.7 °C for > 30 min. Can center temperature was measured by thermocouple and predicted using Comsol software. Thermal conductivity (k) and specific heat (Cp) were estimated as quadratic functions of temperature using Comsol and nonlinear regression. The k and Cp functions were then used to predict temperature inside the grape pomace during retorting. Similar heating experiments were run at different time–temperature treatments from 8 to 25 min for kinetic parameter estimation. Anthocyanin concentration in the grape pomace was measured using HPLC. Degradation rate constant (k110 °C) and activation energy (Ea) were estimated using nonlinear regression. The thermophysical properties estimates at 100 °C were k = 0.501 W/m °C, Cp= 3600 J/kg and the kinetic parameters were k110 °C= 0.0607/min and Ea= 65.32 kJ/mol. The 95% confidence intervals for the parameters and the confidence bands and prediction bands for anthocyanin retention were plotted. These methods are useful for thermal processing design for nutraceutical products.

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