58-12 |
Comparative kinetic study and evaluation of nutrient degradation during distribution and storage of four frozen green vegetables |
M. C. Giannakourou, Department of Chemical Engineering, National Technical University of Athens, Iroon Polytechniou 5, Athens, 15780, Greece, V. Psimouli, and P. S. TAOUKIS, Department of Chemical Engineering, National Technical University, Iroon Polytechniou 5, Athens, 15780, Greece. Current dietary guidelines promote increased uptake of green vegetables. Seasonality, perishability of green vegetables and convenience leads to consumption in processed form, primarily frozen. Changes not only at processing but mainly during subsequent handling, distribution and storage of sensitive nutrients, such as Vitamin C must be considered and quantitavely evaluated. The objective of this work was to conduct a systematic, comparative kinetic study of Vitamin C deterioration for four different frozen green vegetables, in the whole temperature range occuring in the real distribution chain of frozen foods. Frozen green peas, green beans, spinach and okra, packed in high barrier film were stored in programmable control cabinets. Isothermal (at five temperatures from -3 to -20oC) and variable temperature kinetic experiments were conducted, and Vitamin C content was measured by HPLC. In all cases, Vitamin C loss followed apparent first order kinetics. Spinach showed a significantly faster nutritional degradation at all temperatures (50% loss in 2 months at -15oC), followed by green beans and green peas, whereas, in okra, Vitamin C was well retained. Temperature dependence of Vitamin C loss was satisfactorily modeled by Arrhenius relation and estimated EA was similar for all vegetables ranging from 24 to 28 kcal/mol. The applicability of the kinetic models was validated at dynamic storage conditions based on the agreement of experimental and predicted values. A realistic assessment of the range of Vitamin C value at the consumers end was further obtained by a Monte Carlo simulation. Real data on temperature distribution throughout the frozen chill chain were used. Validated kinetic models for Vitamin C loss were shown to be useful for reliable prediction of the remaining nutrient value of frozen green vegetables at any point of their route to the consumer.
Session 58, Food Engineering: Transport processes and kinetics
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