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Valorisation of Portuguese almond cultivars: an integrated approach
| Resumo: | Agriculture is endlessly facing new challenges, being the most pressing one the foreseen climate changes. One of the approaches to limit the effects of challenging growth conditions for plants is the use of more adapted plant cultivars, able to withstand abiotic stress, like water shortage or excess heat. Almond tree is known to be able to tolerate, to some extent, some of those stresses, but, using more adapted cultivars might be able to maintain production yield, without the need of further inputs to the crop. However, thorough characterization of those cultivars is needed to allow the best selection, increasing success of their use in future orchards. Portugal possesses favourable edaphoclimatic conditions for almond production, and a large diversity of traditional cultivars, most of them with little to none available agronomical or chemical data. Hence, this works aims at providing information about some of those cultivars (‘Amendoão’, ‘Bonita’, ‘Casanova’, ‘Molar’, ‘Pegarinhos’, ‘Refêgo’ and ‘Verdeal’), regarding not only physiological parameters of trees, but also physico-chemical characteristics of fruits. The first approach was to study leaf anatomy and water relation parameters under rain-fed conditions (Chapter 2). Inter-cultivar differences were recorded, even though some leaf characteristics were similar between samples. In cultivars already described as sensitive to water stress, lower thickness of cuticle and of palisade/spongy parenchymas were found, a trend that was reversed in less sensitive cultivars. Other adaptations of less sensitive cultivars also include reduced stomatal density, thicker cell wall and leaf density. Besides knowing leaf morphological traits, study of biochemical characteristics and gas exchange dynamics is key for understanding which cultivars might be more prone to endure water-limited growth conditions (Chapter 3). Again, differences between cultivars were found, however, for Portuguese ones, interesting characteristics to respond to water stress were recorded, namely leaf morphology (leaf mass per area or leaf density) chemical traits (Chlorophyll a/Chlorophyll b ratio, carotenoid and phenolic content) or gas exchange parameters (stomatal conductance and transpiration rate). After characterization of leaf traits, gas exchange and water relations of almond trees, fruits from Portuguese cultivars were also analysed. The first approach focused on pomological characteristics and mechanical behaviour of shell, important for processing purposes (Chapter 4). Characteristics varied greatly, has these are some of the defining traits for each cultivar. Even so, similar or higher kernel weight and shelling percentage were found for Portuguese cultivars, when compared to foreign ones. However, shell rupture force was higher for all traditional cultivars, some of them presenting large variations that might hinder automated shelling processes. Even so, characteristics of interest in some traditional almond cultivars (namely ‘Amendoão’, ‘Casanova’, ‘Pegarinhos’ and ‘Refêgo’) were found, that can be further used by the almond industry. Almond is linked to beneficial effects on health due to the presence of bioactive compounds. Hence, identification and quantification of those compounds was performed (Chapter 5). High levels of bioactive compounds were found in some Portuguese cultivars, namely the twenty phenolic compounds that were identified, although only eight found in all cultivars. Twenty-one fatty acids were identified, not all present in the studied cultivars, being the major ones oleic and linoleic acids. Lower content of saturated fatty acids was recorded in the foreign cultivars, making their consumption beneficial to the cardiovascular system. Almond are eaten raw, but also after processing, being the two most common procedures roasting and blanching. Therefore, the effects of such processing steps in almonds also have to be elucidated (Chapters 6 and 7). In Chapter 6, the effect of roasting on volatile profile of almonds was evaluated using headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). Overall, 35 compounds were identified, mainly alcohols and aldehydes. Roasting changed quantitative and qualitative volatile profile, but with different behaviours depending on cultivar, showing that some of them can be more directed to industrial uses. In Chapter 7, raw almonds were compared to roasted and blanched ones, regarding chemical and sensorial characteristics. Overall, roasting increased bioactive compounds and antioxidant activity, contrary to what was found for blanching. Fatty acid profiles were also affected by processing, with a decrease in monounsaturated and saturated fatty acids, but also in health-related lipid indexes. Sensorial characteristics were improved by processing, but differently, depending on the tested cultivar. The combined information is expected to help preservation of these neglected Portuguese almond cultivars, by providing data that can be used both by producers and industry. Knowing the characteristics of trees and fruits of a given cultivar, it can be selected for the most suitable use, which will, ultimately increase their value, thus providing incentives for their conservation. |
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| Autores principais: | Oliveira, Ivo Vaz de |
| Assunto: | Prunus dulcis traditional cultivars leaf traits gas exchange fruit characteristics chemical composition antioxidant activity sensory analysis |
| Ano: | 2024 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Trás-os-Montes e Alto Douro |
| Idioma: | inglês |
| Origem: | Repositório da UTAD |
| Resumo: | Agriculture is endlessly facing new challenges, being the most pressing one the foreseen climate changes. One of the approaches to limit the effects of challenging growth conditions for plants is the use of more adapted plant cultivars, able to withstand abiotic stress, like water shortage or excess heat. Almond tree is known to be able to tolerate, to some extent, some of those stresses, but, using more adapted cultivars might be able to maintain production yield, without the need of further inputs to the crop. However, thorough characterization of those cultivars is needed to allow the best selection, increasing success of their use in future orchards. Portugal possesses favourable edaphoclimatic conditions for almond production, and a large diversity of traditional cultivars, most of them with little to none available agronomical or chemical data. Hence, this works aims at providing information about some of those cultivars (‘Amendoão’, ‘Bonita’, ‘Casanova’, ‘Molar’, ‘Pegarinhos’, ‘Refêgo’ and ‘Verdeal’), regarding not only physiological parameters of trees, but also physico-chemical characteristics of fruits. The first approach was to study leaf anatomy and water relation parameters under rain-fed conditions (Chapter 2). Inter-cultivar differences were recorded, even though some leaf characteristics were similar between samples. In cultivars already described as sensitive to water stress, lower thickness of cuticle and of palisade/spongy parenchymas were found, a trend that was reversed in less sensitive cultivars. Other adaptations of less sensitive cultivars also include reduced stomatal density, thicker cell wall and leaf density. Besides knowing leaf morphological traits, study of biochemical characteristics and gas exchange dynamics is key for understanding which cultivars might be more prone to endure water-limited growth conditions (Chapter 3). Again, differences between cultivars were found, however, for Portuguese ones, interesting characteristics to respond to water stress were recorded, namely leaf morphology (leaf mass per area or leaf density) chemical traits (Chlorophyll a/Chlorophyll b ratio, carotenoid and phenolic content) or gas exchange parameters (stomatal conductance and transpiration rate). After characterization of leaf traits, gas exchange and water relations of almond trees, fruits from Portuguese cultivars were also analysed. The first approach focused on pomological characteristics and mechanical behaviour of shell, important for processing purposes (Chapter 4). Characteristics varied greatly, has these are some of the defining traits for each cultivar. Even so, similar or higher kernel weight and shelling percentage were found for Portuguese cultivars, when compared to foreign ones. However, shell rupture force was higher for all traditional cultivars, some of them presenting large variations that might hinder automated shelling processes. Even so, characteristics of interest in some traditional almond cultivars (namely ‘Amendoão’, ‘Casanova’, ‘Pegarinhos’ and ‘Refêgo’) were found, that can be further used by the almond industry. Almond is linked to beneficial effects on health due to the presence of bioactive compounds. Hence, identification and quantification of those compounds was performed (Chapter 5). High levels of bioactive compounds were found in some Portuguese cultivars, namely the twenty phenolic compounds that were identified, although only eight found in all cultivars. Twenty-one fatty acids were identified, not all present in the studied cultivars, being the major ones oleic and linoleic acids. Lower content of saturated fatty acids was recorded in the foreign cultivars, making their consumption beneficial to the cardiovascular system. Almond are eaten raw, but also after processing, being the two most common procedures roasting and blanching. Therefore, the effects of such processing steps in almonds also have to be elucidated (Chapters 6 and 7). In Chapter 6, the effect of roasting on volatile profile of almonds was evaluated using headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). Overall, 35 compounds were identified, mainly alcohols and aldehydes. Roasting changed quantitative and qualitative volatile profile, but with different behaviours depending on cultivar, showing that some of them can be more directed to industrial uses. In Chapter 7, raw almonds were compared to roasted and blanched ones, regarding chemical and sensorial characteristics. Overall, roasting increased bioactive compounds and antioxidant activity, contrary to what was found for blanching. Fatty acid profiles were also affected by processing, with a decrease in monounsaturated and saturated fatty acids, but also in health-related lipid indexes. Sensorial characteristics were improved by processing, but differently, depending on the tested cultivar. The combined information is expected to help preservation of these neglected Portuguese almond cultivars, by providing data that can be used both by producers and industry. Knowing the characteristics of trees and fruits of a given cultivar, it can be selected for the most suitable use, which will, ultimately increase their value, thus providing incentives for their conservation. |
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