María L. López

Long-Term Storage of Pink Lady Apples Modifies Volatile-Involved Enzyme Activities: Consequences on Production of Volatile Esters

Pink Lady apples were harvested at commercial maturity and stored at 1 degrees C and 92% relative humidity under either air or controlled atmosphere conditions (2 kPa O 2:2 kPa CO 2 and 1 kPa O 2:1 kPa CO 2) for 27 weeks. Data on the emission of volatile compounds and on the activity of some related enzymes in both skin and flesh tissues were obtained during subsequent shelf life at 20 degrees C. Major effects of storage atmosphere and poststorage period were observed on the emission of volatile esters and their precursors. Changes in the production of volatile esters were partly due to alterations in the activity of alcohol o-acyltransferase, but the specific esters emitted by fruit after storage also resulted largely from modifications in the supply of the corresponding substrates. Samples stored under air were characterized by higher availability of acetaldehyde, whereas those stored under CA showed enhanced emission of the alcohol precursors ethanol and 1-hexanol (2 kPa O 2) and 1-butanol (1 kPa O 2), with accordingly higher production of ethyl, hexyl, and butyl esters. Multivariate analysis revealed that a large part of the observed differences in precursor availability arose from modifications in the activity of the enzymes considered. Higher pyruvate decarboxylase activity in air-stored fruit possibly accounted for higher acetaldehyde levels in these samples, while storage under 1 kPa O 2 led to significantly decreased lipoxygenase activity and thus to lessened production of 1-hexanol and hexyl esters. Low acetaldehyde availability together with enhanced hydroperoxide lyase and alcohol dehydrogenase levels in these fruits are suggested to have led to higher emission of 1-butanol and butyl esters.

Shelf-life of 'Golden Reinders' Apples after Ultra Low Oxygen Storage: Effect on Aroma Volatile Compounds, Standard Quality Parameters, Sensory Attributes and Acceptability

The aim of this work was to estimate shelf-life potential and understand quality characteristics of ‘Golden Reinders’ apples during ripening after storage under ultra low oxygen (ULO) atmosphere. Fruits, corresponding to two different maturity stages (147 and 155 dafb), were kept at 1 °C in ULO atmosphere (1 kPa O2: 1 kPa CO2) for seven months and subsequently kept at 1 °C in regular air for up to 28 days. Sub-batches were removed weekly and transferred to 20 °C, so that the shelf-life periods at room temperature were 28, 21, 14, 7, and 0 days. Fruit from both maturity stages showed firmness and soluble solids content (SSC) values above the minimum commercial requirements for this variety throughout the post-storage ripening period. However, only earlier harvested fruit maintained high levels of titratable acidity (TA). Production of aroma volatile compounds was low for shorter ripening periods, though it increased progressively as ripeness advanced. Principal component analysis showed the variables that positively influenced acceptability were: octyl acetate, hexyl octanoate, butyl propanoate, propyl pentanoate, and 6-methyl-5-hepten-2-one as aroma volatile compounds; SSC, TA, firmness, and epidermis colour (Hue) as physicochemical parameters; and sourness and sensory firmness as sensory attributes. From a general overview, the optimum shelf-life period for ‘Golden Reinders’ apples would be between 7 and 14 days for both maturity stages.