Acorn oil extraction by high-pressure

• Autor(a) principal: Ferreira, Inês Jesus Brochado
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/30793
• topic: High-pressure assisted extraction; Emerging technology; Acorn oil; Fatty acids and antioxidant activity

In recent decades, there has been an increasing concern for consumer health, the pursuit of a well-being-oriented lifestyle and the preservation of the environment. These factors led to considering the use of green technologies. High-pressure is an emerging technology that has been highlighted for the extraction of bioactive compounds. Acorn is a very abundant fruit in Portugal, but is still sub-valorised, despite its lipid profile being very similar to that of olive oil. Thus, in this work, it is intended to valorise the acorn by extracting the oil by high pressure and subsequently evaluate the lipid profile and antioxidant activity of the oil. Several approaches were taken to improve oil extraction (solvents, methods, acorn: solvent ratios, etc.), having opted to study through a factorial experimental design the impact of pressure (0.1, 250 and 500 MPa), extraction time (5, 12.5 and 20 min) and temperature (10, 25 and 40 °C) on oil yield, the content of oleic acid, total saturated, monounsaturated and polyunsaturated fatty acids present in acorn oil. The surface response methodology was used to analyse the results, having then determined the optimal conditions predicted by the models that were properly validated. The models showed a satisfactory and adequate fit to the experimental data and the correlations of the models indicated that the models can be used to predict the results. However, the predicted and experimental results differed by more than 45%, which requires more validation tests in future. The optimum extraction condition for the yield was 394 MPa, 5 min and 40 °C, while for the other analysed parameters it was 500 MPa, 13 min and 10 °C. These extracts showed a remarkable antioxidant activity by DPPH up to 327.65 ± 33.40 µmol TE/ g oil. In addition, the main fatty acids were oleic (58-59%), linoleic (21-23%) and palmitic (14-15%). The yields obtained by high-pressure in optimal conditions were 19 e 37% lower than that obtained with Soxhlet. However, the oil extracted by high-pressure at 500 MPa, 13 min e 10°C showed a fatty acid composition similar to the oil extracted by the traditional method with the additional advantages of having been obtained 72 times faster and presenting greater oxidative stability. Acorn oils have good nutritional quality which, when conveniently recovered, can have numerous applications in different sectors, while at the same time valuing acorns. The results obtained in this study make high-pressure technology a promising process for extracting acorn oil.