Fonseca, Susana C.

Malcata, F. Xavier

Silva, Cristina L. M.

English

Repositório Institucional da Universidade Católica Portuguesa

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 Católica Portuguesa, Rua Dr. António Bernardino de Almeida, P-4200-072 Porto, Portugal* E-mail: scfonseca@mail.esb.ucp.ptObjectiveApplication 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.Introduction● Rationalization 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 & MethodsResults●Apparent 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 I Procedure 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 SEMImageanalysisProductpreparation● Scanning 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 ofmicrostructural changes over time after cutting, under refrigerated storage. Red bell pepper samples stored for 4 and 7 dpresented (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 quantitativeparameters.● This work allowed optimization of preparation procedures of sample, and development of successful methodology forquantitative image analysis – which will eventually permit application to related work in other food matrices.Scanning electron micrographs offresh-cut red bell pepper,according to different preparationprocedures and storage time:Procedure I0 dProcedure I7 dProcedure II0 dProcedure II7 dProcedure III0 dProcedure III7 dAuthor S. C. Fonseca acknowledges financial support by FCT (Portugal), via a PostDoc fellowship (BPD/1601/2000). Theauthors acknowledge financial support through Programa Operacional para a Agricultura e o Desenvolvimento Rural – ProjectAGRO nº 822 (Novas Tecnologias de Processamento de Hortofrutícolas Congelados – EMERCON).0 1 2 3 4 5 6 7Time, d123456789Degree of cellular destruction of red bell pepper over time under refrigerated storage (average±standard 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 dry Core removal Cut in dicesStorage (2 ± 0.5 C and 90-95% RH

Microstructural analysis of fresh-cut red bell pepper (Capsicum annuumL.) aiming at postharvest quality optimization

https://repositorio.ucp.pt/bitstream/10400.14/6272/1/com-int_2005_ESB_1294_Silva_Cristina_179.pdf.pdf

Microstructural analysis of fresh-cut red bell pepper (Capsicum annuumL.) aiming at postharvest quality optimization

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Repositório Institucional da Universidade Católica Portuguesa