(25) Characterization of Volatile Biosynthesis in `Jonagold' Apples (Malus ×domestica Borkh.) during the Ripening Process (2025)

Emission Patterns of Esters and Their Precursors Throughout Ripening and Senescence in ‘Redchief Delicious’ Apple Fruit and Implications Regarding Biosynthesis and Aroma Perception

Journal of the American Society for Horticultural Science

The volatile profile of ‘Redchief Delicious’ apple (Malus ×domestica Borkh.) fruit was evaluated at 18 time points from 3 weeks before to 8 weeks after onset of autocatalytic ethylene production to capture the dynamics associated with development from mature green to senescent fruit. Minor amounts of ester production began several days before the onset of ethylene production. Ester production rose rapidly as internal ethylene levels increased beyond 22 nmol·L−1 (0.5 µL·L−1). Peak ester production roughly coincided with maximum ethylene synthesis, declining thereafter. Ester production was further evaluated according to the acid- (alkanoate) and alcohol- (alkyl) derived portions of the ester. The maximum rate of production for a given ester tended to occur later in development as the chain length of the alcohol-derived portion declined. The production rate for many esters paralleled the rate of emanation of their respective alcohol substrates, suggesting that availability of the alco...

Factors that influence biosynthesis of volatile flavor compounds in apple fruits. HortScience

Volatile ester-synthesising capacity throughout on-tree maturation of ‘Golden Reinders’ apples

Scientia Horticulturae, 2011

Volatile compounds emitted by apple (Malus × domestica Borkh.) fruit change during maturation and ripening, and hence maturity stage at harvest is a key factor determining fruit aroma. In this work, production of aroma volatile compounds and some related enzyme activities were monitored weekly in 'Golden Reinders' apples during 7 weeks prior to commercial harvest. Three maturity stages (immature, mature unripe and ripe) could be defined by the variables studied. Esters were quantitatively prominent among the compounds identified in the volatile fraction, and in most cases their production was higher at later stages of fruit maturation. Hexyl acetate, hexyl propanoate and hexyl 2-methylbutanoate, together with ethyl 2-methylbutanoate, 2-methylbutyl acetate and butyl 2-methylbutanoate, were found to be important contributors to the characteristic aroma of 'Golden Reinders' apples. Little variations in alcohol o-acyltransferase (AAT) activity levels were found throughout the experimental period. Higher lipoxygenase and hydroperoxide lyase activities were found in the skin than in the flesh tissue, suggesting involvement of this tissue in volatile ester-forming capacity during fruit maturation. The enhancement of volatile ester production by 'Golden Reinders' apples at late maturity stages may have arisen mainly from greater availability of substrates, thus pointing out the relevance of regulating points located upstream of AAT in the pathway.

Factors that Influence Biosynthesis of Volatile Flavor Compounds in Apple Fruits

Hortscience, 1997

Changes in biosynthesis of aroma volatile compounds during on-tree maturation of ‘Pink Lady®’ apples

Postharvest Biology and Technology, 2008

The production of aroma volatile compounds and standard quality attributes, in addition to lipoxygenase (LOX), hydroperoxide lyase (HPL), pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH) and alcohol o-acyltransferase (AAT) activities, were assessed during maturation of 'Pink Lady ® ' apples. Low production of aroma volatiles was observed in early harvested fruit, which gradually increased as ripeness approached. Hexyl acetate, hexyl 2-methylbutanoate, hexyl hexanoate, hexyl butanoate, 2-methylbutyl acetate and butyl acetate were prominent within the blend of volatiles produced by fruit throughout maturation. Multivariate analysis showed these compounds had the highest influence on differentiation of maturity stages, indicating that aroma volatile emission is an important factor for definition of fruit ripeness, which suggests production of these esters might be useful as an index of maturity. No large variations in AAT activity were found throughout the experimental period despite increasing ester emission, suggesting the enhancement of ester production by 'Pink Lady ® ' apples at ripening arises mainly from greater availability of substrates. Increased LOX activity was observed at later stages of fruit development, and the possible role of this enzyme activity on enhanced capacity for aroma volatile biosynthesis in more mature fruit is discussed.

The Relationship Between the Production of Volatile Aromas and the Induction of Ethylene in Apple Fruits

HortScience

The volatile aromas from the fruits of `Naganofuji No.2' apple (Malus domestica Mill.) were determined by gas chromatography (GC) and combined GC-mass spectrometry (GC-MS) after different temperature conditions. The fruits from CA storage were sealed in glass and the volatiles in the headspace were determined. Eleven compounds of four chemical classes from active carbon absorbed samples were measured and three of them—tormic acid pentyl ester, butanoic acid-1-methyl ethylester and 4-hydroxy-3-methyl-2-butanone, were identified at 20 °C, but not at °C. Under 20 °C condition, the contents of three volatiles increased from 1 hour and reached to their peaks at the 4th to 7th hour. The content of ethylene reached its peak at 4 hours and changed synchronically with the other volatiles during the experiment. The content of ethylene was significantly positively correlated with the contents of volatile aromas (r = 0.96-0.98, P ≤ 0.01). Under °C condition, the content of ethylene was sign...

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

Journal of Agricultural and Food Chemistry, 2008

Pink Lady apples were harvested at commercial maturity and stored at 1°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°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.

Profiling Fruit Volatiles in the Progeny of a ‘Royal Gala’ × ‘Granny Smith’ Apple (Malus×domestica) Cross

Journal of Agricultural and Food Chemistry, 2009

Volatile flavor compounds from the fruit of the progeny of two apple (Malus  domestica) cultivars with distinctive flavor and volatile profiles, 'Royal Gala' and 'Granny Smith', were measured by headspace gas chromatography-mass spectrometry over two fruiting seasons. Principal component analysis separated the volatile profiles into two groups according to the amounts produced of butyl, 2-methybutyl, pentyl, and hexyl acetates and of ethyl butanoate, butanol, 2-methylbutanol, and hexanol. Fruit containing the four acetate esters clustered with the 'Royal Gala' parent and were scored more similar to 'Royal Gala' than to "Granny Smith' in flavor. Fruit clustering with the 'Granny Smith' parent contained higher levels of ethyl butanoate and alcohols. Levels of acetate esters correlated to levels of their alcohol precursors, and control of this trait segregated in Mendelian fashion. The locus was mapped to the top of 'Royal Gala' linkage group 2 close to the Rvi4 (Vh4) locus for resistance to Venturia inaequalis, the causal agent of apple scab.

Development of aroma-synthesising capacity throughout fruit maturation of ‘Mondial Gala’ apples

The Journal of Horticultural Science and Biotechnology, 2008

Emission of aroma volatile compounds (AVCs) and the activity of some related enzymes were monitored during ontree maturation of 'Mondial Gala' apples. Volatile esters were quantitatively prominent among the AVCs identified throughout the experiment and, in most cases, their production increased noticeably during the later stages of fruit development. However, the activity of alcohol o-acyltransferase (AAT), the enzyme directly responsible for ester production, was detectable at almost constant levels throughout the experimental period, and therefore it was not in accordance with changes in the emission of volatile esters. Multivariate analysis indicated that the increase in the production of volatile esters during maturation arose mainly from the greater availability of substrates for esterification reactions, rather than from increased AAT activity. The role of some aroma-related enzyme activities in controlling the supply of precursors for ester production is discussed.

Volatile production, quality and aroma-related enzyme activities during maturation of ‘Fuji’ apples

Postharvest Biology and Technology, 2004

Production of volatile aroma compounds, and quality parameters, were monitored in relation to the activity of lipoxygenase, pyruvate decarboxylase, alcohol dehydrogenase and alcohol o-acyltransferase during maturation of 'Fuji' apples. Acetate esters increased during maturation and were quantitatively the most significant compounds contributing to 'Fuji' aroma. Increase in acetate ester production was associated with the availability of the necessary alcohol precursors. Principal component analysis revealed a clear separation according to sampling date, which accounted for up to 67% of total variance, and allowed 'Fuji' apples used in this study to be classified into three ripeness stages. Overall the results suggest that precursor availability for the related enzymes is a more significant factor than enzyme activity for the development of aroma during on-tree maturation of 'Fuji' apples.