Publicação
From kiwi waste to value-added compounds using biobased solvents
| Resumo: | The valorization of resources composed of high value-added compounds is one of the most relevant areas of sustainable chemistry. The waste from the kiwi industry is a potential source of bioactive compounds, such as phenolic compounds, which exhibit biological activity with potential health benefits. However, the application of volatile organic solvents for their extraction is still the preferred choice. Aiming to develop a green approach for the valorization of kiwi industry wastes, this work studied the use of biobased solvents (gamma-valerolactone (GVL), cyrene and alkanediols), with hydrotropic character, to improve the solubility, and effectively extract phenolic compounds from Actinidia deliciosa 'Hayward' kiwi peels. First, the solubility of three phenolic compounds (catechin, syringic acid and ferulic acid) in aqueous solutions of biobased solvents were evaluated. The obtained results demonstrated the potential of biobased solvents as hydrotropes for phenolic compounds, with the aqueous solutions of GVL leading to higher increments on the solubility of the phenolic compounds when compared to pure water: up to 61-fold, 99-fold, 237-fold for catechin, syringic and ferulic acid, respectively. It was also demonstrated that the hydrotropy mechanism depends on both hydrotrope and solute. The hydrotropic effect tends to be higher for more hydrophobic hydrotropes, in diluted regions; however, the increase of the hydrophobicity of biobased solvents is not always beneficial, and therefore a balance between these two effects is required. Additionally, experiments to increase the solubility of the best hydrotrope-solute pair (GVL-ferulic acid) through high pressure have shown that pressure has no effect on increasing solubility, it only allows a faster solubilization kinetics. Afterwards, the effective extraction of phenolic compounds from kiwi peels, using different mixtures of biobased solvents with ethanol and/or water was carried out, with the mixtures of GVL being the most efficient. Then, the best biobased solvent composition was optimized, being the mixture composed of GVL:ethanol in a ratio of 7:3 (wt/wt) identified with the best performance. After, a response surface methodology (RSM) was used to optimize the extraction conditions of conventional extraction (CE), ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE), with MAE being identified as the most promising technique to obtain an extract with high levels of phenolics (mainly composed of epicatechin, caffeic acid and quercetin) and antioxidant activity, in a shorter extraction time. However, an economic study demonstrated that UAE is the preferable extraction technique. In summary, the results obtained demonstrate that biobased solvents combined with alternative techniques can effectively extract phenolic compounds from kiwi peels, working as a base for the development of more sustainable, economic, and efficient extraction processes to recover natural products from food industry wastes. |
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| Autores principais: | Silva, Sandra Santos da |
| Assunto: | Solid-liquid extraction Kiwi waste Phenolic compounds Natural antioxidants Biobased solvents Optimization process |
| Ano: | 2021 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Aveiro |
| Idioma: | inglês |
| Origem: | RIA - Repositório Institucional da Universidade de Aveiro |
| Resumo: | The valorization of resources composed of high value-added compounds is one of the most relevant areas of sustainable chemistry. The waste from the kiwi industry is a potential source of bioactive compounds, such as phenolic compounds, which exhibit biological activity with potential health benefits. However, the application of volatile organic solvents for their extraction is still the preferred choice. Aiming to develop a green approach for the valorization of kiwi industry wastes, this work studied the use of biobased solvents (gamma-valerolactone (GVL), cyrene and alkanediols), with hydrotropic character, to improve the solubility, and effectively extract phenolic compounds from Actinidia deliciosa 'Hayward' kiwi peels. First, the solubility of three phenolic compounds (catechin, syringic acid and ferulic acid) in aqueous solutions of biobased solvents were evaluated. The obtained results demonstrated the potential of biobased solvents as hydrotropes for phenolic compounds, with the aqueous solutions of GVL leading to higher increments on the solubility of the phenolic compounds when compared to pure water: up to 61-fold, 99-fold, 237-fold for catechin, syringic and ferulic acid, respectively. It was also demonstrated that the hydrotropy mechanism depends on both hydrotrope and solute. The hydrotropic effect tends to be higher for more hydrophobic hydrotropes, in diluted regions; however, the increase of the hydrophobicity of biobased solvents is not always beneficial, and therefore a balance between these two effects is required. Additionally, experiments to increase the solubility of the best hydrotrope-solute pair (GVL-ferulic acid) through high pressure have shown that pressure has no effect on increasing solubility, it only allows a faster solubilization kinetics. Afterwards, the effective extraction of phenolic compounds from kiwi peels, using different mixtures of biobased solvents with ethanol and/or water was carried out, with the mixtures of GVL being the most efficient. Then, the best biobased solvent composition was optimized, being the mixture composed of GVL:ethanol in a ratio of 7:3 (wt/wt) identified with the best performance. After, a response surface methodology (RSM) was used to optimize the extraction conditions of conventional extraction (CE), ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE), with MAE being identified as the most promising technique to obtain an extract with high levels of phenolics (mainly composed of epicatechin, caffeic acid and quercetin) and antioxidant activity, in a shorter extraction time. However, an economic study demonstrated that UAE is the preferable extraction technique. In summary, the results obtained demonstrate that biobased solvents combined with alternative techniques can effectively extract phenolic compounds from kiwi peels, working as a base for the development of more sustainable, economic, and efficient extraction processes to recover natural products from food industry wastes. |
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