Publicação
In vitro production of Ganoderma lucidum mycelium from northeast Portugal: The antioxidant potential of tocopherols extract in the preservation of natural yogurt
| Resumo: | The increase in public awareness for the direct relationship between diet and health has led to concerns related to the use of commercial food additives, promoting the search for natural alternatives. Thus, natural antioxidants are among the most searched compounds nowadays, due to the issues related with the oxidative stress and its harmful effects on both food quality and human health. Tocopherols are among the most well-known and interesting natural antioxidants because its use as a food additive has multiple benefits. These are encompassed by the designation of vitamin E, which is an essential and extremely important micronutrient for human health that should be provided by the diet, being a strong wall against oxidation, especially in cooperation with vitamin C. The use of natural tocopherols at an industrial level depends on the sustained production, hence the importance and choice of the in vitro culture as an alternative to their production. The in vitro production of natural compounds allows a continuous year round availability of the demanded products in an independent way of environmental conditions and without ecological issues. In recent years, mushrooms became more and more value and exploited due to their richness on valuable compounds with biotechnological interest and to their easier and faster in vitro production compared to plants. Moreover, the in vitro production of mushrooms mycelium has been explored to improve the synthesis of antioxidants, namely tocopherols. The present work aims to evaluate the tocopherols content of the well-known medicinal mushroom Ganoderma lucidum (Curtis) P. Karst from the Northeast of Portugal, produced by in vitro culture, and comparing with its fruiting body. The tocopherol levels were determined by chromatographic techniques, namely by high performance liquid chromatography coupled to a fluorescence detector (HPLC-fluorescence). Afterwards, a tocopherol rich extract from the mycelium was incorporated in natural yogurts, and the antioxidant potential of the extract (before incorporation) and yogurts (after incorporation) was assessed, in order to study its potential as a food additive. The antioxidant activity was evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and the reducing power assays. Moreover, the effectiveness of the tocopherol rich extract as a food Abstract xi additive was evaluated for the maintenance of the nutritional properties of the studied food matrix. These studies were carried out comparing the nutritional parameters of four yogurt formulations: i) control (yogurt without any type fortifying agent); ii) yogurt with potassium sorbate - E202; iii) yogurt with α-tocopherol - E307; and iv) yogurt with G. lucidum mycelium tocopherol enriched extract. Overall, with regard to the in vitro culture, G. lucidum mycelium did not show significant differences in radial growth between the two used media. The chemical analysis showed that the in vitro produced mycelium of G. lucidum was particularly rich in -tocopherol (362±7 μg/g extract) and β-tocopherol (272±8 μg/g extract), among the total tocopherols content 717±12 μg tocopherols/g extract with relevant differences in comparison to the corresponding fruiting body. Besides, G. lucidum mycelium showed good results in the DPPH radical scavenging activity assay (EC50 = 10.4±0.2 mg/mL), but especially good in the reducing power assay (EC50 = 0.32±0.01 mg/mL). While, different results were registered in the tested yogurt formulations with the highest antioxidant activities observed in yogurts incorporated with α-tocopherol and G. lucidum extract. Besides, no particularly significant differences were observed among 0 and 7 days, especially in yogurts incorporated with tocopherol enriched extract obtained from G. lucidum mycelium. The evaluation of the interaction between the yogurts formulations (YF) and the storage time (ST) on the nutritional composition of yogurts, showed a significant impact on fat, protein and lactose, indicating that the ST influenced these parameters differently for each YF. Furthermore, the effect of YF was only significant for fat, protein, carbohydrates and lactose, resulting that the statistical classification could only be indicated for carbohydrates, which reached maximum values in yogurts prepared with potassium sorbate (5.9±0.2 g/100 g). Also, significant changes in the contents of fat, protein and lactose were registered due to the ST with higher values for fat and lactose in yogurts stored during 7 days, while the protein content did not showed any identifiable tendency. Furthermore, the fatty acids profile showed that the changes induced by ST vary according to YF in most cases and that ST did not induce significant changes in the fatty acids profile, with exception for C4:0, C8:0 and C18:1n9. Abstract xii According to the Linear Discriminant Analysis (LDA), it was possible to identify the most distinctive parameters of each YF, allowing to choose the functionalizing agent (potassium sorbate, α-tocopherol or the enriched extract in tocopherols obtained from G. lucidum mycelium), according to a specific objective (in this case preservative effect). Considering the values of the antioxidant activity, it can be concluded that the yogurt incorporated with α-tocopherol or extract enriched in tocopherols obtained from the mycelium of G. lucidum, presented a greater preservation potential. Overall, the mycelium of G. lucidum might certainly be considered as a potential source of tocopherols to be employed as food lipophilic antioxidants. |
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| Autores principais: | Amara, Khira |
| Ano: | 2017 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Instituto Politécnico de Bragança |
| Idioma: | inglês |
| Origem: | Biblioteca Digital do IPB |
| Resumo: | The increase in public awareness for the direct relationship between diet and health has led to concerns related to the use of commercial food additives, promoting the search for natural alternatives. Thus, natural antioxidants are among the most searched compounds nowadays, due to the issues related with the oxidative stress and its harmful effects on both food quality and human health. Tocopherols are among the most well-known and interesting natural antioxidants because its use as a food additive has multiple benefits. These are encompassed by the designation of vitamin E, which is an essential and extremely important micronutrient for human health that should be provided by the diet, being a strong wall against oxidation, especially in cooperation with vitamin C. The use of natural tocopherols at an industrial level depends on the sustained production, hence the importance and choice of the in vitro culture as an alternative to their production. The in vitro production of natural compounds allows a continuous year round availability of the demanded products in an independent way of environmental conditions and without ecological issues. In recent years, mushrooms became more and more value and exploited due to their richness on valuable compounds with biotechnological interest and to their easier and faster in vitro production compared to plants. Moreover, the in vitro production of mushrooms mycelium has been explored to improve the synthesis of antioxidants, namely tocopherols. The present work aims to evaluate the tocopherols content of the well-known medicinal mushroom Ganoderma lucidum (Curtis) P. Karst from the Northeast of Portugal, produced by in vitro culture, and comparing with its fruiting body. The tocopherol levels were determined by chromatographic techniques, namely by high performance liquid chromatography coupled to a fluorescence detector (HPLC-fluorescence). Afterwards, a tocopherol rich extract from the mycelium was incorporated in natural yogurts, and the antioxidant potential of the extract (before incorporation) and yogurts (after incorporation) was assessed, in order to study its potential as a food additive. The antioxidant activity was evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and the reducing power assays. Moreover, the effectiveness of the tocopherol rich extract as a food Abstract xi additive was evaluated for the maintenance of the nutritional properties of the studied food matrix. These studies were carried out comparing the nutritional parameters of four yogurt formulations: i) control (yogurt without any type fortifying agent); ii) yogurt with potassium sorbate - E202; iii) yogurt with α-tocopherol - E307; and iv) yogurt with G. lucidum mycelium tocopherol enriched extract. Overall, with regard to the in vitro culture, G. lucidum mycelium did not show significant differences in radial growth between the two used media. The chemical analysis showed that the in vitro produced mycelium of G. lucidum was particularly rich in -tocopherol (362±7 μg/g extract) and β-tocopherol (272±8 μg/g extract), among the total tocopherols content 717±12 μg tocopherols/g extract with relevant differences in comparison to the corresponding fruiting body. Besides, G. lucidum mycelium showed good results in the DPPH radical scavenging activity assay (EC50 = 10.4±0.2 mg/mL), but especially good in the reducing power assay (EC50 = 0.32±0.01 mg/mL). While, different results were registered in the tested yogurt formulations with the highest antioxidant activities observed in yogurts incorporated with α-tocopherol and G. lucidum extract. Besides, no particularly significant differences were observed among 0 and 7 days, especially in yogurts incorporated with tocopherol enriched extract obtained from G. lucidum mycelium. The evaluation of the interaction between the yogurts formulations (YF) and the storage time (ST) on the nutritional composition of yogurts, showed a significant impact on fat, protein and lactose, indicating that the ST influenced these parameters differently for each YF. Furthermore, the effect of YF was only significant for fat, protein, carbohydrates and lactose, resulting that the statistical classification could only be indicated for carbohydrates, which reached maximum values in yogurts prepared with potassium sorbate (5.9±0.2 g/100 g). Also, significant changes in the contents of fat, protein and lactose were registered due to the ST with higher values for fat and lactose in yogurts stored during 7 days, while the protein content did not showed any identifiable tendency. Furthermore, the fatty acids profile showed that the changes induced by ST vary according to YF in most cases and that ST did not induce significant changes in the fatty acids profile, with exception for C4:0, C8:0 and C18:1n9. Abstract xii According to the Linear Discriminant Analysis (LDA), it was possible to identify the most distinctive parameters of each YF, allowing to choose the functionalizing agent (potassium sorbate, α-tocopherol or the enriched extract in tocopherols obtained from G. lucidum mycelium), according to a specific objective (in this case preservative effect). Considering the values of the antioxidant activity, it can be concluded that the yogurt incorporated with α-tocopherol or extract enriched in tocopherols obtained from the mycelium of G. lucidum, presented a greater preservation potential. Overall, the mycelium of G. lucidum might certainly be considered as a potential source of tocopherols to be employed as food lipophilic antioxidants. |
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