Roasting treatments affect oil extraction rate, fatty acids, oxidative stability, antioxidant activity, and flavor of walnut oil

Huankang Li; Jiajia Han; Zhongkai Zhao; Jinhu Tian; Xizhe Fu; Yue Zhao; Changqing Wei; Wenyu Liu

doi:10.3389/fnut.2022.1077081

Roasting treatments affect oil extraction rate, fatty acids, oxidative stability, antioxidant activity, and flavor of walnut oil

Front Nutr. 2023 Jan 4:9:1077081. doi: 10.3389/fnut.2022.1077081. eCollection 2022.

Authors

Huankang Li¹, Jiajia Han¹, Zhongkai Zhao², Jinhu Tian³, Xizhe Fu¹, Yue Zhao¹, Changqing Wei^{1

4}, Wenyu Liu¹

Affiliations

¹ School of Food Science and Technology, Shihezi University, Shihezi, China.
² College of Life Sciences and Technology, Xinjiang University, Ürümqi, China.
³ College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, China.
⁴ Key Laboratory of Xinjiang Phytomedicine Resource and Utilization of Ministry of Education, Shihezi University, Shihezi, China.

Abstract

Introduction: The quality of pressed walnut oil can be improved by moderate roasting treatment.

Methods: This study compared physicochemical characteristics and antioxidant ability of walnut oils pressed from differently roasted pretreated walnuts, analyzed the correlation among these indicators by using Pearson correlation coefficient and correlation coefficient heatmap, and evaluated the volatile organic compounds (VOCs) of walnut oil under optimal pretreatment roasting conditions using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS).

Results: Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were able to remarkably distinguish walnut oil produced by different roasting processes. In addition, correlation analysis showed that there was a significant impact among indicators. There were 73 VOCs were identified in the optimum roasted treated walnut oil, consisting of 30 aldehydes, 13 alcohols, 11 ketones, 10 esters, 5 acids, 2 oxygen-containing heterocycles, 1 nitrogen-containing heterocycle and 1 other compound. GC-IMS results showed that aldehydes contributed significantly to the volatile flavor profile of walnut oil, especially (E)-2-heptenal, (E)-2-pentenal and hexenal.

Discussion: The properties of walnut oil based on varying roasting pretreatment of walnut kernels were significantly differentiated. Roasting at 120°C for 20 min is a suitable pretreatment roasting condition for pressing walnut oil. Roasting at 120°C for 20 min is a suitable pretreatment roasting condition for pressing walnut oil.

Keywords: HS-GC-IMS; antioxidant capacity; correlation analysis; physicochemical characteristics; roasting treatment; volatile organic compounds; walnut oil.