Quality of guava (Psidium guajava L. cv. Pedro Sato) fruit stored in low-O<inf>2</inf> controlled atmospheres is negatively affected by increasing levels of CO<inf>2</inf>

Abstract

Guava is a climacteric fruit, extremely perishable, that has a short shelf life. Controlled atmosphere (CA) and cold storage can be used to extend guava shelf life. However, few studies have been conducted to evaluate the effects of CA storage on guavas, especially with high levels of carbon dioxide (CO<inf>2</inf>). Therefore the objective of this study was to evaluate the quality changes of 'Pedro Sato' guava fruit during CA storage with atmospheres containing low concentrations of O<inf>2</inf> and increasing levels of CO<inf>2</inf>. For that, 'Pedro Santo' guavas were stored at 12.2°C for up to 28 days in atmospheres with low oxygen (O<inf>2</inf>) concentration (5kPa) and increasing level of CO<inf>2</inf> (1, 5, 10, 15 or 20kPa CO<inf>2</inf>) in order to evaluate the fruit quality changes. It was possible to identify the relationships among quality variables in response to atmosphere composition and storage duration which were related to modifications due to ripening (ratio SS/TA, TSS, RS, TA), ripening and early CO<inf>2</inf> injury modifications (pH, SS, chromaticity), and CO<inf>2</inf> injury modifications (hue angle, firmness, soluble pectin). A clear CO<inf>2</inf> injury occurred in fruit stored in 5kPa O<inf>2</inf>+15kPa CO<inf>2</inf> and 5kPa O<inf>2</inf>+20kPa CO<inf>2</inf> after 28 days at 12.2°C, with increasing pH values and soluble pectin content, which were inversely related to fruit firmness. 'Pedro Sato' guavas should be stored in atmospheres with 5kPa O<inf>2</inf> and no more than 5kPa CO<inf>2</inf> in order to prevent CO<inf>2</inf> damage. Further investigation is necessary to identify the metabolites responsible for the onset of responses to high CO<inf>2</inf> in guava fruit.