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Determinação não destrutiva da qualidade interna de "Ortanique" (Citrus reticulata Blanco x Citrus sinensis (L) Osbeck)
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Advisor(s)
Abstract(s)
A tângera ‘Ortanique’ (Citrus reticulata Blanco x Citrus sinensis (L) Osbeck) é um dos
citrinos que consta da Norma ‘’Citrinos do Algarve - IGP’’ e foi escolhida para
desenvolver este estudo com vista à determinação não invasiva da sua qualidade interna.
Os frutos foram recolhidos de vinte cinco árvores georreferenciadas em dois pomares,
situados em Vale Judeu e Gambelas, em cinco amostragens que decorreram antes e depois
do período comercial. Ainda no pomar e antes da recolha dos frutos para a determinação
laboratorial dos parâmetros de qualidade através de métodos padronizados, efetuou-se a
aquisição de espetros de refletância difusa. Utilizou-se um sistema portátil, que inclui um
espetrómetro e uma sonda de interactância, para recolha dos espetros na região do visívelinfravermelho
próximo (Vis-IVP), na gama 680 – 1100 nm. Analisou-se a evolução
temporal, em termos médios, de diversos parâmetros incluindo aqueles constantes da
Norma (Acidez Titulável, Índice de Maturação, Teor de Sólidos Solúveis, Firmeza). A
georreferenciação permitiu a elaboração de mapas para os vários parâmetros de qualidade
e para os dois pomares, com vista a estudar a sua distribuição espacial, o que permitiu
localizar zonas nos dois pomares responsáveis pela maior ou menor variabilidade
biológica dos frutos. Mais, este mapeamento permitiu analisar, ainda que posteriormente,
as taxas de variação dos parâmetros se alteravam nas diversas zonas do pomar, o longo
da maturação. Definiram-se valores limite de interesse, nomeadamente os que constam
da Norma, para diversos parâmetros o que permitiu comparar a sua evolução no tempo
para os dois pomares desta mesma variedade. O método dos mínimos quadrados parciais
ou Partial Least Squares (PLS) foi o método de regressão utilizado para a construção dos
modelos de calibração dos parâmetros determinados laboratorialmente através dos
espetros recolhidos com o fruto na árvore. A existência de dois pomares permitiu efetuar,
para além da validação interna dos modelos, a validação externa com recurso à calibração
do modelo com dados de um pomar e validação com dados de outro. Foram obtidos
modelos para o índice de maturação, acides titulável, teor de sólidos solúveis, sacarose,
ácido ascórbico e firmeza. Os modelos com melhor previsão foram aqueles construídos e
validados com dados do próprio pomar. Como descrito na literatura, os modelos pioraram
o seu comportamento preditivo quando foram submetidos a amostras provenientes de
outro pomar (validação externa). No entanto, este trabalho permitiu antever o potencial
da utilização da espectroscopia de Vis-IVP como uma ferramenta valiosa na avaliação
extensiva e em tempo real do estado de maturação dos pomares de ‘Ortanique’.
Tangerine ‘Ortanique’ (Citrus reticulata Blanco x Citrus sinensis (L) Osbeck) is a Protected Geographical Indication (PGI) fruit. The specific norm stipulates several quantitative and qualitative requirements, to commercialize this variety as “Citrinos do Algarve” - IGP. The aim of this study was to determine non-invasively the internal quality of ‘Ortanique’. Fruits were assessed from twenty-five georeferenced trees in two orchards, located in Vale Judeu and Gambelas, in five samplings along ripening. In each orchard and before collecting the fruits for the laboratory standard determination of the quality parameters, diffuse reflectance spectra were acquired from fruits on-tree. A portable system, including a spectrometer and an interactance probe, were used to collect spectra in the near visibleinfrared region (Vis-NIR), in the 680-1100 nm range. Internal quality parameters, including the ones stated in the PGI commodity were analyzed by standard methods. The georeference allowed ellaborating maps for the several internal quality parameters, of both orchards and to study their spatial distribution along time. Several zones were found to induce biological variability in the orchard. Moreover, this mapping allowed to analyze which were the parameters rates of variation in the orchard, throughout ripening. Threshold values were defined, namely those present in the Standard, for several parameters, which allowed to compare their evolution in time for the two orchards and the same variety. Partial Least Squares (PLS) was used to build the calibration models of the various internal quality parameters, by correlating those determined through the standard methods, with the spectra collected from the fruits on-tree. The existence of two orchards allowed performing, in addition to the internal validation, the external validation of the models with data from one orchard and validation with data from another. Models were obtained for the maturation index, titratable acidity, soluble solids content, sucrose, ascorbic acid and firmness. The models with the best prediction performance were the ones built and validated with data from the same orchard. As described in the literature, the models worsened their predictive behavior when they were submitted to samples from another orchard (external validation). Yet, this work has shown a strong potential for the use of Vis-NIRs as a smart tool to provide an extensive and real-time assessment of ‘Ortanique’ orchards ripening stage.
Tangerine ‘Ortanique’ (Citrus reticulata Blanco x Citrus sinensis (L) Osbeck) is a Protected Geographical Indication (PGI) fruit. The specific norm stipulates several quantitative and qualitative requirements, to commercialize this variety as “Citrinos do Algarve” - IGP. The aim of this study was to determine non-invasively the internal quality of ‘Ortanique’. Fruits were assessed from twenty-five georeferenced trees in two orchards, located in Vale Judeu and Gambelas, in five samplings along ripening. In each orchard and before collecting the fruits for the laboratory standard determination of the quality parameters, diffuse reflectance spectra were acquired from fruits on-tree. A portable system, including a spectrometer and an interactance probe, were used to collect spectra in the near visibleinfrared region (Vis-NIR), in the 680-1100 nm range. Internal quality parameters, including the ones stated in the PGI commodity were analyzed by standard methods. The georeference allowed ellaborating maps for the several internal quality parameters, of both orchards and to study their spatial distribution along time. Several zones were found to induce biological variability in the orchard. Moreover, this mapping allowed to analyze which were the parameters rates of variation in the orchard, throughout ripening. Threshold values were defined, namely those present in the Standard, for several parameters, which allowed to compare their evolution in time for the two orchards and the same variety. Partial Least Squares (PLS) was used to build the calibration models of the various internal quality parameters, by correlating those determined through the standard methods, with the spectra collected from the fruits on-tree. The existence of two orchards allowed performing, in addition to the internal validation, the external validation of the models with data from one orchard and validation with data from another. Models were obtained for the maturation index, titratable acidity, soluble solids content, sucrose, ascorbic acid and firmness. The models with the best prediction performance were the ones built and validated with data from the same orchard. As described in the literature, the models worsened their predictive behavior when they were submitted to samples from another orchard (external validation). Yet, this work has shown a strong potential for the use of Vis-NIRs as a smart tool to provide an extensive and real-time assessment of ‘Ortanique’ orchards ripening stage.
Description
Keywords
"Ortanique" Espectroscopia Vis-IVP Qualidade interna "Citrinos do Algarve-IGP" Agricultura de precisão Dieta mediterrânica