microstructural analysis of fresh-cut red bell pepper ( capsicum annuum l.)

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Procedure I 0 d. Procedure I 7 d. Procedure II 0 d. Procedure II 7 d. Procedure III 0 d. Procedure III 7 d. Microstructural analysis of fresh-cut red bell pepper ( Capsicum annuum L.) aiming at postharvest quality optimization. Susana C. FONSECA * Cristina L. SILVA - PowerPoint PPT Presentation

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  • Microstructural analysis of fresh-cut red bell pepper (Capsicum annuum L.) aiming at postharvest quality optimizationSusana C. FONSECA *Cristina L. SILVA F. Xavier MALCATAEscola Superior de Biotecnologia, Universidade Catlica Portuguesa, Rua Dr. Antnio Bernardino de Almeida, P-4200-072 Porto, Portugal* E-mail: scfonseca@mail.esb.ucp.pt ObjectiveApplication of SEM to evaluate microstructure of fresh-cut red bell pepper, after cutting and maintaining (for 0, 4 and 7 d) under refrigerated storage. In order to achieve such a goal, two sub-objectives were addressed: i) to optimise the sample preparation procedure prior to analysis of red bell pepper by SEM, and ii) to develop an adequate methodology to quantify SEM images.IntroductionRationalization of deterioration processes that take place during postharvest of fresh fruits and vegetables, and in particular fresh-cut ones, is essential to optimize postharvest quality and maximize shelf-life. Materials & Methods

    ResultsApparent differences were observed between preparation procedures; in Procedure III, a dendritic structure appeared during ice microcrystal formation inside the cells. Differences in microstructural effects associated with time of storage after cutting were also observed; samples cut and stored for 7 d showed a great degree of cell decompartmentation and collapse, reflected by poor definition of cell walls as compared with samples taken just after cutting. Statistical analysis of experimental data generated by the panel pertaining to SEM images indicated that there are microstructural differences between pepper samples from the distinct preparation procedures (p=0.001) and time after cutting under refrigerated storage (p=0.001); however, the interaction between these two factors was not statistically significant (p=0.051). Frozen samples presented higher cellular destruction than via the other two procedures, and no statistical significant differences were observed between these two. Red bell pepper samples stored for 4 and 7 d presented (as expected) higher degree of cellular destruction than their initial sample counterpart.This requires understanding microstructure, and relating it to macroscopic quality characteristics of the food product. Scarce work has indeed focused to date on the microstructure of fresh and fresh-cut fruits and vegetables.MicrostructuralanalysisProcedure IIProcedure IProcedure IIIfrozen by immersion in N2frozen1 d at -80 Cfreeze-dried stored at -80 C freeze-dried stored at -80 C frozen by immersion in N2stored at -80 C Fresh red bell peppersObservation by low vacuum SEMImageanalysisProductpreparationScanning electron microscopy (SEM) is an interesting technique for microstructural studies. after 0, 4 and 7 dPanellists asked to rate each image** Cellular destruction rating scale:1 = absence3 = very little5 = moderately, 7 = very much9 = extremeConclusions SEM was successfully applied in the microstructural study of fresh-cut red bell pepper; it provided a clear viewing of microstructural changes over time after cutting, under refrigerated storage. Red bell pepper samples stored for 4 and 7 d presented (as expected) higher degree of cellular destruction than samples at 0 d. Samples for SEM prepared via freeze-drying produced better quality images than frozen samples. The methodology applied, which was based on panel evaluation of SEM images, proved a valuable tool to obtain quantitative parameters. This work allowed optimization of preparation procedures of sample, and development of successful methodology for quantitative image analysis which will eventually permit application to related work in other food matrices.Scanning electron micrographs of fresh-cut red bell pepper, according to different preparation procedures and storage time:Author S. C. Fonseca acknowledges financial support by FCT (Portugal), via a PostDoc fellowship (BPD/1601/2000). The authors acknowledge financial support through Programa Operacional para a Agricultura e o Desenvolvimento Rural Project AGRO n 822 (Novas Tecnologias de Processamento de Hortofrutcolas Congelados EMERCON). 01234567Time, d123456789Degree of cellular destruction of red bell pepper over time under refrigerated storage (averagestandard deviation), according to different preparation procedures:() procedure I; () procedure II; and () procedure III. Degree of cellular destructionImage selectionPreparation of electronic evaluation sheet Delivery by e-mail to panellistsWash and dryCore removalCut in dicesStorage (2 0.5 C and 90-95% RH

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