The aim of the present work was to compare the effect of ultralow oxygen (ULO) with dynamic controlled atmosphere (DCA) and controlled atmosphere (CA) on the post storage quality of 'Royal Gala' and 'Galaxy' apples after long-term storage. Two experiments were carried out with 'Royal Gala' and 'Galaxy' apples, in the years 2012 and 2013, respectively. A higher internal ethylene concentration was observed in fruits stored under CA; intermediate concentration in fruits under ULO; and the lowest by fruits stored under DCA-CF (DCA based on chlorophyll fluorescence). Flesh firmness was higher in fruits stored under DCA-CF and ULO differing from CA, in the year 2012, but in 2013 fruits stored under ULO showed the highest flesh firmness, differing from CA fruits. DCA-CF is efficient in quality maintenance of 'Royal Gala' and 'Galaxy' apples. Both 'Gala' mutants stored under ULO show a similar quality maintenance to those stored under DCA-CF.

The aim of this work was to assess the profile of volatile compounds in 'Royal Gala' apples stored under controlled atmosphere (CA), with O(2) levels ranging from 1.0kPa to as low as 0.5kPa during 8months (0.5°C), followed by 7days of shelf-life at 20°C. Volatile compounds were collected via solid-phase microextraction (HS-SPME) and analysed by gas chromatography. Straight and branched-chain esters exhibited a distinct pattern. The emission of straight-chain esters decreased under extremely low O(2) (0.5kPa), while branched-chain esters were not significantly affected in such condition. 2-Methyl-butyl acetate, a significant contributor to the 'Royal Gala' aroma, was higher in intermediate O(2) concentration, suggesting that lowering the O(2) levels down to 0.7kPa does not negatively affect the volatile composition of 'Royal Gala' apples, as compared to the standard CA (1.0kPa O(2)). The remaining volatile compounds were not strongly affected by storing fruits under extremely low O(2).

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The effects of dynamic controlled atmosphere (DCA) storage based on chlorophyll fluorescence (DCA-CF) and respiratory quotient (DCA-RQ) on the quality and volatile profile of 'Royal Gala' apple were evaluated. DCA storage reduces ACC (1-aminocyclopropane-1-carboxylate) oxidase activity, ethylene production and respiration rate of apples stored for 9months at 1.0°C plus 7days at 20°C, resulting in higher flesh firmness, titratable acidity and lesser physiological disorders, and provided a higher proportion of healthy fruit. Storage in a regular controlled atmosphere gave higher levels of key volatiles (butyl acetate, 2-methylbutyl acetate and hexyl acetate), as compared to fruit stored under DCA-CF, but fruit stored under DCA-RQ 1.5 and RQ 2.0 also showed higher amounts of key volatile compounds, with increment in ethanol and ethyl acetate, but far below the odour threshold. Storage in DCA-CF reduces fruit ester production, especially 2-methylbutyl acetate, which is the most important component of 'Royal Gala' apple flavour.

RESUMO -Objetivou-se com este trabalho avaliar a qualidade da maçã 'Maxi Gala' submetida a diferentes combinações de níveis de O 2 e CO 2 , temperaturas e perda de massa durante o armazenamento. O experimento foi conduzido em um delineamento inteiramente casualisado em esquema de parcelas subdivididas, com quatro repetições de 25 frutos. Os tratamentos originaram-se da combinação de diferentes condições de atmosfera controlada (AC) em duas temperaturas (0,5 °C e 1 °C), que foram: (1) 1,2 kPa O 2 + 2,5 kPa CO 2 + 3,5% de perda de massa (PM); (2) 1,2 kPa O 2 + 2,5 kPa CO 2 ; (3) 1,2 kPa O 2 + 2,0 kPa CO 2 ; (4) 1,0 kPa O 2 + 2,0 kPa CO 2 ; (5) 0,8 kPa O 2 + 2,0 kPa CO 2 ; e (6) 0,8 kPa O 2 + 1,5 kPa CO 2 . As melhores condições para o armazenamento da maçã 'Maxi Gala' foram as pressões parciais 0,8 a 1,0 kPa O 2 associada com 2,0 kPa CO 2 ou 0,8 kPa O 2 com 1,5 kPa CO 2 na temperatura de 1 °C. Nessas condições ocorre maior manutenção da firmeza da polpa, redução na ocorrência de degenerescência senescente e a polpa farinácea. A perda de massa de 3,5% em AC com 1,2 kPa O 2 + 2,5 kPa CO 2 na temperatura de 1 °C também é eficiente na manutenção da qualidade desta maçã. Palavras-chave:Frutas. Pós-colheita. Perda de massa. Distúrbios fisiológicos.ABSTRACT -The objective of this study was to assess the quality of the 'Maxi Gala' apple under different mixtures of O 2 and CO 2 , temperature and mass loss during storage. The experiment was carried out in a completely randomised design in a system of split-plots, with four replications of 25 fruits. The treatments, derived from the combination of various conditions of controlled atmosphere (CA) at two temperatures (0.5 °C and 1 °C), were: (1) 1.2 kPa O 2 + 2.5 kPa CO 2 + 3.5% mass loss (ML); (2) 1.2 kPa O 2 + 2.5 kPa CO 2 ; (3) 1.2 kPa O 2 + 2.0 kPa CO 2 ; (4) 1.0 kPa O 2 + 2.0 kPa CO 2 ; (5) 0.8 kPa O 2 + 2.0 kPa CO 2 ; and (6) 0.8 kPa O 2 + 1.5 kPa CO 2 . The best conditions for the storage of the 'Maxi Gala' apple were those with partial pressures of 0.8 to 1.0 kPa O 2 associated with 2.0 kPa CO 2 or 0.8 kPa O 2 with 1.5 kPa CO 2 at a temperature of 1°C. Under these conditions flesh firmness is maintained for longer, with a greater reduction in flesh breakdown and mealiness. A weight loss of 3.5% in CA with 1.2 kPa O 2 to 2.5 kPa CO 2 at a temperature of 1°C is also effective in maintaining the quality of this apple.