Alexandru Luca


Alexandru Luca
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PhD Project: Volatile organic compounds as markers for postharvest fruit and vegetable quality changes

University: Aarhus University
Department: Food Science
Supervisor: Assoc. Prof. Merete Edelenbos
Project supervisor: Assoc. Prof. Carl-Otto Ottosen
Project term: 01.08.2012-31.07.2015
Master’s degree: M. Sc. Food Engineering, Middle East Technical University (METU)


Project background:

Fresh fruit and vegetables consist of living cells although the produce is detached from the mother plant. The plant materials emit volatile organic compounds (VOC) with different molecular weight and volatility in response to species, genotype, postharvest storage conditions, internal and external stress conditions and microbial attack. There are reports that acetaldehyde and ethanol is emitted in response to restricted O2 during storage, ethylene in response to stress conditions, ripening, senescence and abscission, and ethane, pentanal and other hydrocarbons in response to senescence, cell wall degradation and fatty acid oxidation.

Fresh fruit and vegetables are treated and stored after harvest to prolong product freshness. Many attempts have been made to prolong the shelf-life and reduce the amount of postharvest waste e.g. treatment with hot water and UV light to reduce the microbial load before storage and storage under low temperature and high humidity with or without reduced O2 and/or increased CO2 atmospheres to prolong the shelf-life. It is a difficult task, however, to treat fresh fruit and vegetables in such a way that an optimum quality is obtained post-storage because fresh fruit and vegetables consist of active plant tissues that respond to the postharvest technologies. Very few studies document the impact of postharvest storage conditions on the release of VOC other than CO2 and ethylene and it is unclear how emitted VOC are related to quality changes such as aroma and flavor despite aroma and flavor are key factors in consumer preferences. It is therefore important to develop analytical methods that can monitor the immediate reaction of fresh fruit and vegetables to various postharvest treatments.



The hypothesis is that there is a relation between product quality and specific volatile organic compounds emitted from fresh fruits and vegetables after harvest.

First aim is to develop a method which can be applied in the monitoring of the release of VOCs from fresh produce. This method will be used to determine the relationship between release of VOCs and postharvest treatments. It is also planned to study the impact of VOCs on the sensory quality changes and other quality parameters during postharvest storage.


Research outline:

Firstly, a sampling method of VOCs released from Wild Rocket leaves stored in modified atmosphere packages should be developed. Analyzed samples will be stored in close systems suitable for monitoring of temperature, relative humidity and air composition and for gas sampling (VOC, ethylene, O2 and CO2). Afterwards, an analytical technique to identify and quantify these compounds should be optimized by using gas chromatography and different detectors (MS, FID, NCD, SCD). The GC-method will be simplified to be used on fresh fruits and vegetables stored under different conditions using multivariate data analysis on the data from the initial sampling of VOC.

In the next part of the project, a simplified GC-method will be used to study the changes in VOC according to type of plant material and storage conditions. Plant material can be of different cultivars and other independent parameters for it will be time of harvest and time after harvest. Different pre-storage treatments will be applied on the plant material and other changing parameters related to the storage conditions will be postharvest temperature, relative humidity and gas composition. Gas composition of the storage environment will be obtained by using packaging films with different OTR/CTR/WVTR packages.

Lastly it is aimed to find the relationships between external factors (temperature during storage, relative humidity, O2 and CO2 composition of storage environment), internal factors (time of/after harvest, cultivars), key VOCs responsible for desirable and unwanted aroma, flavor compounds, and other quality changes. The changes in quality will be investigated by standard quality measurements (GC-O) and quantitative descriptive analysis.

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