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Effect of roasting conditions on the composition and antioxidant properties of defatted walnut flour
Joana Santos1, Manuel Alvarez-Ortí2, Estela Sena-Moreno2
1LAQV/REQUIMTE, Departamento de Ciências Químicas, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal.
Background:
Walnut oil extraction by pressure systems produces a press cake as a by-product, with many of the beneficial walnut properties. The objective of this work was to evaluate the composition and antioxidant properties of walnut flours submitted to different roasting protocols (50, 100 and 150 °C during 30, 60 and 120 min).
Results:
All walnut flours had about 42% protein and a significant amount of dietary fibre (17%), not being affected by the roasting process. Nonetheless, the fat content increased around 50% in walnuts flours subjected to longer and higher roasting temperatures (150 °C). The lipid fraction showed a good nutritional quality with a high vitamin E content (mainly γ-tocopherol) and fatty acid profile rich in linoleic and linolenic acids. The high phenolic content also provides great antioxidant capacity to the flours.
Conclusion:
Mild roasting of walnuts did not affect the quality of the flours that could be used as a functional ingredient in the food industry. © 2017 Society of Chemical Industry.