Friday, 23 October 2015

O aceite galego, saudable e con valor diferencial


A produción de aceite en Galicia como actividade xeralizada é historicamente constatable ata o século XVIII. A partir dese momento comeza o seu declive ata case a súa desaparición. Foi a partir de ben entrada a década dos 90 cando se comezou a producir un tímido auxe da actividade oliveira na comunidade. Na actualidade por unha banda estase a fomentar a plantación de variedades principais, a arbequina e/ou picual, coa finalidade de alcanzar unha produción oleícola intensiva a curto prazo, e, doutra banda, estase a recuperar oliveiras centenarias das variedades coñecidas polos olivicultores locais como brava e mansa para elaborar aceites únicos. Para protexer e garantir este valor diferencial dos aceites elaborados con exemplares de oliveiras centenarias, a investigadora Patricia Reboredo abordou na súa tese de doutoramento unha profunda análise das súas características.

A tese, titulada Caracterización aromática e fenólica de olivas e aceites de oliva producidos en Galicia, foi realizada na Facultade de Ciencias do campus de Ourense baixo a dirección de Jesús Simal, Beatriz Cancho e Carmen González, da Área de Nutrición e Bromatoloxía do Departamento de Química Analítica e Alimentaria da Universidade de Vigo. “En primeiro lugar, o noso obxectivo foi identificar correctamente este material vexetal mediante técnicas moleculares para demostrar que non se trata de variedades de oliveiras rexistradas no Banco de Germoplasma Mundial da Oliveira (BGMO) da Universidade de Córdoba”. Como resultado, detectouse que o perfil molecular das 20 mostras avaliadas coincidiu co da variedade brava, actualmente en fase de rexistro. Unicamente o perfil de dúas mostras non puido asociarse a ningunha das variedades incluídas en devandito BGMO. "Este feito pode deberse a que sexan variedades autóctonas descoñecidas ata o momento ou ben variedades sen introducir aínda no BGMO", comenta a investigadora.

Características aromáticas
Centrándose na análise das características dos aceites galegos, Reboredo sinala que “a calidade sensorial dos aceites elaborados con variedades principais está amplamente avaliada e recoñecida. Con todo, os aceites de oliva virxe obtidos a partir de variedades non clasificadas ata o momento, como os galegos, poderían presentar características diferentes e mesmo superiores a estes”. Se esto se demostra, engade, non só se podería potenciar a elaboración de aceites monovarietais destas variedades minoritarias senón que ademais se poderían deseñar novos aceites resultantes de procesos de moenda ou mestura con outras variedades. 

Na avaliación sensorial realizada durante a investigación, feita unicamente nos aceites elaborados con olivas brava e mansa en diferentes proporcións, os atributos "amargo" e "picante" destacan sobre todo no aceite elaborado cunha maior proporción de brava, mentres que os atributos "doce", "afroitado maduro" e "folla verde" son moi similares en ambos aceites. No desenvolvemento destes novos aceites, a comoenda ou mestura de olivas brava/mansa con arbequina ou picual aumentaron significativamente as series odorantes principais que conforman o perfil sensorial dos aceites e, ao mesmo tempo, a súa funcionalidade debido ao incremento dos compostos fenólicos. 

Na categoría de saudable
En relación á funcionalidade dos aceites, Patricia Reboredo recalca que a Comisión Europea aprobou recentemente a alegación de propiedade saudable para aqueles aceites que conteñan polo menos cinco mg de hidroxitirosol e os seus derivados/por 20 gr de aceite de oliva virxe, tendo en conta que os polifenoles do aceite de oliva contribúen á protección dos lípidos fronte ao dano oxidativo. Segundo apunta a xa doutora ourensá, “os resultados obtidos a partir dun protocolo analítico sinxelo e validado demostraron que os aceites elaborados a partir das olivas brava/mansa satisfán os requisitos esixidos no marco da Unión Europea para poder indicar na etiquetaxe a declaración de propiedade saudable, superando incluso o limiar establecido na lexislación”. 

Perfil aromático non extrapolable da oliva ao aceite
Durante a tese, Reboredo Rodríguez tamén analizou se era posible extrapolar este perfil aromático único das olivas galegas ao aceite. “O aceite de oliva virxe caracterízase, entre outros atributos, polo seu aroma asociado á presenza minoritaria de compostos volátiles que se transfiren ao aceite, en gran medida, desde a moenda do froito. Comprobar se o perfil aromático das olivas se pode extrapolar ao seu correspondente aceite permitiría avaliar o potencial aromático de cada variedade previamente á elaboración do aceite”, comenta a investigadora. 

En base aos resultados obtidos, demostrouse que o perfil aromático das olivas non é extrapolable posto que a actividade das encimas endóxenas ao longo do proceso de elaboración é o principal factor que determina a síntese dos compostos volátiles máis relevantes do aroma do aceite. Na investigación, demostrou que a actividade destas encimas pódese modular variando distintos parámetros durante o proceso de elaboración, sendo a temperatura e o tempo da etapa de batido os máis importantes. “A elección da combinación temperatura/tempo de batido dependerá de se se prioriza a súa funcionalidade ou o seu aroma, ademais de estar supeditada ao rendemento da extracción”, afirma por último.

Fonte: DUvi

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