30B-26 |
Changes in polyphenoloxidase activity, reducing sugars and color in potatoes stored in CO2-enriched atmospheres |
R. M. GALICIA CABRERA1, C. Saucedo Veloz2, E. Ponce-Alquicira3, and I. Guerrero Legarreta3. (1) Departamento de Biotecnlogia, Universidad Autonoma Metropolitana-Iztapalapa, Apartado Postal 55-535, Mexico City, 09340, Mexico, (2) Colegio de Posgraduados, Montecillos, Edo. de Mex., Mexico, (3) Departamento de Biotecnologia, Universidad Autonoma Metropolitana, Iztapalapa, Apartado Postal 55-535, Mexico City, 09340, Mexico Alpha is the leading potato cultivar grown in Mexico. This tuber is susceptible to enzymatic browning reactions which affect quality and consumer acceptance. Chilled storage induces reducing sugars synthesis and alters flavor and texture. Storage of fruit and vegetables in CO2-enriched atmosphere (CA) can inhibit polyphenoloxidase (PPO) activity which results in lower phenolic pigments production and, therefore, reduction of enzymatic browning. The objective of this work was to study the effect of CO2-enriched atmosphere on PPO activity and in the accumulation of ethanol in potatoes cv. Alpha. Potatos were stored in 30% CO2 atmosphere during 120 hours at 7ºC, the control was potatoes stored in air. The response variables were: PPO activity, protein concentration, soluble reducing sugars, texture, browning index and ethanol accumulation. Analysis were carried out at 0, 24, 72 and 120 hours. Results showed an inhibitory effect on PPO activity of potatoes stored in CO2-enriched atmosphere. The enzymatic activity was lower as compared to control samples. It suggested that CO2- can decrease denaturalization extent of the protein moiety of the enzyme. However, protein concentration did not show significant differences between treatment and control. Atmosphere composition and storage time had a significant effect on soluble reducing sugar formation, textural changes and browning index. These response variables had lower values in samples stored in CO2-enriched atmospheres. This was because high CO2- concentrations inhibited PPO that promotes furfural polimerization, hence reducing the amount of brown pigments. At the same time starch was converted in a lesser extent to soluble sugars. CO2-enriched atmospheres also promoted breakdown and solubilization of pectic material. Ethanol concentration had no significant difference between treated and untreated samples. CO2-enriched CA may be an option to inhibit enzymatic browning and to preserve commercial quality of this tuber.
Session 30B, Fruit & Vegetable Products: Sensory, Product Development, Fresh-Cut, and Storage
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