In situ Inactivation of Polyphenol Oxidase in Mamey Fruit (Pouteria sapota) by Microwave Treatment

• Published in: Journal of food science Vol. 77; no. 4; pp. C359 - C365
• Main Authors: Palma-Orozco, Gisela, Sampedro, José G., Ortiz-Moreno, Alicia, Nájera, Hugo
• Format: Journal Article
• Language: English
• Published: Malden, USA Blackwell Publishing Inc 01.04.2012; Wiley; Wiley Subscription Services, Inc
• Subjects: Biological and medical sciences; Blanching; blanching treatment; Catechol Oxidase - metabolism; Catechol Oxidase - radiation effects; Cell Wall - radiation effects; Cell Wall - ultrastructure; Chemical reactions; Damage; Dietary Proteins - metabolism; Dietary Proteins - radiation effects; Enzymes; Food industries; Food Irradiation - adverse effects; Food science; Fruit - enzymology; Fruit - radiation effects; Fruit - ultrastructure; Fruit and vegetable industries; Fruits; Fundamental and applied biological sciences. Psychology; Hot Temperature - adverse effects; Inactivation; mamey; Microscopy, Electron, Scanning; microstructural analysis; Microstructure; microwave treatment; Microwaves; Microwaves - adverse effects; Pigmentation - radiation effects; Plant Proteins - metabolism; Plant Proteins - radiation effects; Polyphenol oxidase; Polyphenols; Polyphenylene oxides; Pouteria - enzymology; Pouteria - radiation effects; Pouteria - ultrastructure; Quality Control; Time Factors; Tissues; mamey; Fruit; Enzyme; In situ; Microwave; Catechol oxidase; Inactivation; microstructural analysis; Analysis; microwave treatment; polyphenol oxidase; Oxidoreductases; Blanching; blanching treatment
• ISSN: 0022-1147; 1750-3841
• DOI: 10.1111/j.1750-3841.2012.02632.x

:  Polyphenol oxidase (PPO) is the enzyme responsible for quality loss in most fruits and vegetables. Quality loss is mainly because of oxidative chemical reactions which generate the darkening of tissues. Mamey fruit (Pouteria sapota) after harvesting suffers a rapid quality decay trough activation of PPO. However, PPO may be inactivated in situ by chemical or thermal treatment. In food processing, microwave treatment (MT) has been used recently as an alternative for PPO inactivation. In this study, it was observed that mamey fruit pulp subjected to a gently MT resulted in a higher PPO activity as the generated heat induced in situ the increase in PPO activity. In contrast, PPO was completely inactivated after long MT by using a high microwave power. Temperature in mamey pulp after MT reached a maximum of 79 °C; although PPO was active up to 60 °C. PPO was completely inactivated when conventional blanching treatment was performed but required a higher temperature (92 °C/300 s). The optimum energy intensity (Eopt) for PPO inactivation by MT was 0.51 kJ/g or 937 W/165 s. Under this condition, the remaining PPO activity was inversely proportional to energy intensity (E). Interestingly, MT resulted in a negligible damage in microstructure of mamey pulp, although blanching treatment resulted in large damaging effects on tissue organization and shape. Therefore, MT is proposed as an effective way to completely inactivate PPO without causing any significant damage to fruit tissues and shape; as preservation of color, flavor, and taste would be favored.