91A-2 |
Changes in polyphenoloxidase activity, reducing sugars and protein content in potato extract model systems stored in CO2-enriched atmospheres |
R. M. GALICIA-CABRERA1, C. Saucedo-Veloz2, E. Ponce-Alquicira1, and I. Guerrero-Legarreta1. (1) Departamento de Biotecnología, Universidad Autónoma Metropolitana, Iztapalapa, Apartado Postal 55-535, Mexico D.F., 09340, Mexico, (2) Colegio de Posgraduados, Montecillos, Estado de Mexico, Mexico Enzymatic and non-enzymatic browning commonly occur in potatoes during storage. They considerably affect quality and consumer’s acceptance. Low temperature storage promotes reducing sugar synthesis, altering flavor and texture. In previous studies it was demonstrated that storage in CO2-enriched atmospheres reduced polyphenoloxidase(PPO) activity in potatoes cv. Alpha. Consequently, enzymatic browning and production of phenolic pigments were decreased. Reducing sugar synthesis was also lowered, diminishing non-enzymatic browning and sweetness in fried potatoes. The objective of this work was to study the effects of a CO2-enriched atmosphere on PPO activity, reducing sugars and protein concentration in a potato cv. Alpha extract model system. The model systems, at pH 4.5 and 6.5, were stored in a CO2-enriched atmosphere or air at 7°C during 120 h. Response variables were: PPO activity, reducing sugars and protein concentration. Results showed an inhibitory effect of the controlled atmosphere on PPO activity in samples at pH 6.5. Enzymatic activity was lower as compared to the control. It was assumed that the enzyme was partially denatured by CO2, although the protein concentration was not significantly different as compared to samples stored in air. The CO2-enriched atmosphere had an inhibitory effect on reducing sugar synthesis, as they consistently increased throughout the study time. Enzymatic activity was not detected in extracts at pH 4.5 stored in the controlled atmosphere nor in air, due to inhibition of PPO activity at this pH. CO2-enriched atmospheres can be an alternative to inhibit enzymatic browning and to extend the commercial life on potato extracts at pH 6.5.
Session 91A, Food Chemistry: Enzymes, vitamins and plant pigments
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