Prospection and identification of bioactive compounds in the products of the soybean oil ethanolic extraction

• Ano de defesa: 2019
• Autor(a) principal: Borges, Larissa Braga Bueno
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Antioxidantes; Antioxidants; Biodiesel; Estabilidade oxidativa; Ethanol extraction; Extração com etanol; Isoflavonas; Isoflavone; Oil refining; Oxidative stability; Refino de óleo; Soja; Soybean
• Link de acesso: http://www.teses.usp.br/teses/disponiveis/11/11141/tde-16082019-164037/

Soybean oil is commercially obtained through an extraction process using hot commercial hexane. This toxic solvent, derived from petroleum, must be subsequently evaporated before the oil can be submitted to refining steps prior to storage and transportation or directly moving to biodiesel synthesis. Extraction of soybean oil with ethanol, a renewable, low-toxicity solvent, results in the production of an oil-rich miscella that can be directly esterified to produce ethyl esters (biodiesel) without the need for oil-refining steps and evaporation of the solvent. This extraction also generates an oil-poor miscella that has been successfully reinserted in further extractions as the solvent. The theoretical bases of the ethanolic extraction of soybean oil have been established by the works of many authors, focusing on the insurance of high oil yields. However, the effects of the ethanolic extraction of vegetable oils on the antioxidant profile and oxidative stability of the extraction products have not yet been addressed. This study aimed to increase the knowledge on the antioxidant composition of the rich and poor miscella derived from the extraction of soybean oil using ethanol as solvent. Results showed that although the rich miscella presents lower amounts of tocopherols in comparison to oils extracted with hexane, it contains antioxidant compounds of polar character with high affinity to ethanol, which would not be found in soybean oils extracted with hexane. Among these compounds isoflavones have been identified and quantified. The reuse of the poor miscella in subsequent extractions promotes an increase in the oxidative stability of the rich miscella, possibly, by adding antioxidant compounds with high affinity to ethanol. This effect was also observed in the use of the oil-poor miscella in liquid-liquid washings with waste cooking oil, resulting increase of the induction period. However, consecutive extractions of soybean oil have shown that the increase in the induction period of the oil-rich miscella reaches a limit. This phenomenon may be an indication of pro-oxidant effects, resulting from the increase in the content of the compounds present in the rich-miscella. For this reason, the study of the interactions between different classes of antioxidant compounds present in the soybean ethanolic extraction products may be an excellent way to understand the mechanisms involved in the oxidative stability of complex lipid systems.