Title: Op naar een snelle analyse van aardbei vluchtige componenten: Ontwikkeling en implementatie.
Other Titles: Towards Fast Analysis of Strawberry Volatiles: Development and Implementation.
Authors: Vandendriessche, Thomas
Issue Date: 10-Sep-2012
Abstract: <w:latentstyles suitable<br not therefore and consuming time very however, is, method This spmeGC-MS). (hs="" spectrometry="" mass="" –="" chromatography="" gas="" micro-extraction="" phase="" headspacesolid="" is="" evaluation="" volatile="" for="" technique="" analytical="" preferred="" the="" <w:lsdexceptionlocked="false" semihidden="false" priority="0" locked="false" The cultivated strawberry (Fragaria x ananassa Duch. ex Rozier), the “Queen of berries”, is one of the world’s most important soft fruits characterized by its typical flavor and nutritional value. Nevertheless, consumers often criticize the sensory quality of commercial cultivars. The poor sensory quality is the result of genetic erosion because past strawberry breeding programs have been mainly focusing on fruit characteristics such as firmness, size, disease resistance and postharvest handling. Present breeding projects, however, try to develop new strawberry cultivars with enhanced aroma quality to satisfy consumers’ expectations. To do so, the industry needs high-throughput techniques for strawberry volatile analysis that can be easily implemented in the selection process. The main objective of this thesis was, therefore, to study the potential of new fast high-throughput instrumental methods for the analysis of strawberry volatiles. To achieve this objective, three sub-objectives were addressed; (i), the optimization of novel fast techniques for high-throughput analysis of strawberry volatiles; (ii), the evaluation of the performance of these new techniques; and (iii), the application of proper multivariate data analysis tools to select aroma enriched strawberry cultivars during breeding.The preferred analytical technique for volatile evaluation is headspace solid phase micro-extraction gas chromatography – mass spectrometry (HS SPME GC-MS). This method is, however, very time consuming and therefore not suitable to implement in breeding programs requiring high-throughput techniques. By making use of narrow-bore capillary columns and a modular accelerated column heater, conventional HS SPME GC-MS analysis could be speed up from 30-60 min to HS SPME fast GC-MS with a run time of 8 min without loss of resolution and data information. The parameters influencing SPME extraction were optimized, resulting in an incubation time of 10 min, an extraction time of 30 min and an incubation/extraction temperature of 40 &#176;C while a 50/30 µm DVB-CAR-PDMS fiber proved to be the best fiber of choice. Special attention was also paid to sample preparation. Storage of the samples at -80 &#176;C prior to analysis, did not affect the volatile profile. However during blending and elevated temperature, changes in volatile composition have to be taken in consideration. Finally, it was found that the intensities of the volatiles change according to the strawberry tissue type. As proof of principle, HS SPME fast GC-MS was incorporated in an instrumental platform to evaluate strawberry quality during ripening as well as to highlight inter-cultivar differences. With this technique it was possible to follow changes in volatile composition through strawberry ripening and to indicate which volatile compounds are characteristic for unripe (1-penten-3-ol) and ripe strawberries (methyl butanoate, pentyl acetate and methyl hexanoate). In addition, nine strawberry cultivars could be differentiated from each other and biomarkers for each cultivar identified.HS SPME fast GC-MS was then combined used in combination with chemometrics to establish a new workflow for cultivar selection. The proposed method, allows the evaluation of the full volatile profile at once rather than the classical approaches in which every volatile compound is analyzed separately. Besides time-saving, the coherence of the volatile profile is not lost preventing the loss of important information. Furthermore, defining a target aroma based on prior consumer expectations concerning the ‘ideal’ strawberry aroma enables the breeder to direct the breeding process towards this target from the early beginning. Finally, the potential of another high-throughput technique for strawberry volatile analysis, multi-capillary column chromatography – ion mobility spectrometry (MCC-IMS), was evaluated and compared to HS SPME fast GC-MS. MCC-IMS showed to have potential as a tool for monitoring changes in volatiles during strawberry shelf life. Both techniques were evaluated as detection tools for early Botrytis cinerea infections through changes in the volatile profile. Although the prediction is not ideal, both techniques were able to determine the changes in volatiles as function of a progressing infection as determined by an enzyme-linked immunosorbent assay. In addition, with the information obtained from the HS SPME fast GC-MS analysis, potential volatile biomarkers specific for B. cinerea being 3-methylbutanal, cis-4-decenal, 2-methyl-1-butanol, 2-methyl-1-propanol, 1-octen-3-one and 1-octen-3-ol, were identified.In conclusion, two high-throughput analytical techniques have been optimized and evaluated for strawberry volatile analysis. Both techniques performed well and proved, in combination with multivariate data analysis, to be powerful tools. Therefore, these techniques have potential to be used in high-throughput screening of novel strawberry cultivars as well as in many postharvest applications.
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Division of Mechatronics, Biostatistics and Sensors (MeBioS)
Division of Crop Biotechnics

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