44C-6 |
Polyphenol oxidase in FHIA-01 bananas |
M. MATA-MONTES DE OCA1, M. Lopez-Gomez, B. Tovar-Gomez, and H. S. Garcia4. (1) Laboratorio de Investigacion en Alimentos, Instituto Tecnologico de Tepic, Apdo. Postal 634, Tepic, Nay., 63000, Mexico, (2) UNIDA, Instituto Tecnologico de Veracruz The FHIA-01 variety of banana is a hybrid that was developed to be resistant to the Black Sigatoka. This pathogen is responsible for substantial losses in commercial banana production fields in the tropic. Previous investigations have found substantially smaller activity of polyphenol oxidase (PPO) in this variety when compared to other commercial varieties, which poses an interesting fact and technological potential. The objective was to evaluate PPO activity in peel and pulp of the FHIA-01 banana during normal post-harvest ripening. FHIA-01 bananas were obtained from the INIFAP experimental station in the state of Nayarit, México, and set to ripen at 20 °C. Every 2 days, fruits were withdrawn and PPO-a was measured in buffer (phosphates, 0.2M, pH 6) extracts of both pulp and pericarp. Cathecol (0.175M) was used as substrate measuring absorbance gain at 420 nm. Protein content, pH values, titratable acidity and soluble solids were also determined. For comparison purposes, the same determinations were performed on commercial bananas (AAA group, Cavendish subgroup cv Giant Cavendish). PPO-a in the pulp and peel of both varieties reached a maximum 8 days post-harvest, with the Giant Cavendish variety showing ca. 3.5 greater specific activity of PPO than variety FHIA-01. The peel tissue had almost 30 times less PPO specific activity than the pulp and enzyme activity in FHIA-01 bananas was smaller. During the progress of ripening, pH values were smaller and titratable acidity was higher in the FHIA-01 variety, whereas soluble solids were similar in either variety. Small differences measured in pH values and acidity can not account for the rather marked contrast in PPO activities. More research is needed to purify and fully characterize this enzyme, but the practical importance of this type of PPO activity in bananas to be used for processing is evident.
Session 44C, Fruit & Vegetable Products: Chemistry
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