Comparison of Different Processing Methods of Iron Walnut Oils (Juglans sigillata): Lipid Yield, Lipid Compositions, Minor Components, and Antioxidant Capacity

Abstract

A comparison study is performed on different processing methods of iron walnut oils (Juglans sigillata). Processing methods here include cold‐pressing (CP), roasting‐pressing (RP), n‐hexane extraction (HE), subcritical butane extraction (SBE), and supercritical carbon dioxide extraction. The lipid yield, physicochemical properties, lipid compositions, minor components, and antioxidant capacity of iron walnut oils are analyzed. Different processing methods do not affect the fatty acid compositions and triacylglycerol compositions of iron walnut oil. The lipid yields of pressing process (42.63–44.12%) is lower than that of the extraction process (48.13–63.44%). By multiple linear regression analysis, the results about the correlation between minor components and antioxidant capacity show that the RP process with high number of polyphenols (52.91 mg kg−1) indicates the highest antioxidant activity (DPPH: 574.73, FRAP: 111.80, ABTS: 498.53, ORAC: 523.34 µmol TE kg−1, respectively). Considering health and nutritional value of oil, RP can be a promising method for future iron walnut oil processing. Practical Applications: Iron walnut (Juglans sigillata) is a special walnut variety in China. In this study, five different processing methods of iron walnut oil are evaluated. The new iron walnut oil processing method is beneficial to the development of iron walnut oil. The authors show that lipid composition of tested oils is relatively stable, while their minor components contents are significantly different. Oil antioxidant capacity is mainly related to polyphenols. Roasting‐pressing can obviously improve the antioxidant activity of the iron walnut oil. This information has important directive to the nutritional value and industrial production of iron walnut oil. Iron walnut oil is obtained from Juglans sigillata by different processing methods, including cold‐pressing, roasting‐pressing, n‐hexane extraction, subcritical butane extraction, and supercritical carbon dioxide extraction. The lipid yield, physicochemical properties, lipid compositions, minor components, and antioxidant capacity (DPPH, FRAP, ABTS, and ORAC) are analyzed. Models deduced by multiple linear regression are recognized as acceptable for predicting the antioxidant capacity of the iron walnut oil.

Phytochemical Content, Minor‐Constituent Compositions, and Antioxidant Capacity of Screw‐Pressed Walnut Oil Obtained from Roasted Kernels

“…Roasting can release polyphenols from their bonds to various cellular components, thereby leading to polyphenols content increase . On the other hand, the Maillard reaction occurs in the walnut kernel due to roasting, which increased the amount of fat‐soluble phenolic compounds via the interaction of carbonyls with amines during thermal processing . Therefore, the polyphenols content in walnut oil was greatly increased.…”

Moderate Edible Oil Refining: State‐of‐the‐Art in China

“…Many other oilseeds require the customized development of operation variables (Gao et al, 2018;Liu et al, 2019;Liu et al, 2020). These include oil refining from coconut, rice bran, rapeseed, and corn germ.…”

Supercritical CO2 extraction of gurum (Citrulluslanatus var. Colocynthoide) seed oil and its properties comparison with conventional methods

“…Tocopherols of oils extracted by SFE, SP, and hexane were identified through a HPLC (LC‐20AT, Japan) using a silica column (4.6 × 250 mm, 5 μm, Jiangsu, China). Detector (SPD‐20A, Japan) set at 295 nm according to as described by Gao, Liu, Jin, and Wang (). Briefly, 1.0 g of oil was weighed and diluted by 10 mL of n‐hexane (chromatographic grade).…”

“…Phytosterols of oils extracted by SFE, SP, and hexane were identified by a GC–MS (Thermo Fisher) using a DB‐5 capillary column (Agilent, 30 m × 0.25 mm, 0.25 μm) according to procedures described by Gao et al (), and the contents of phytosterols were reported as mg/100 g.…”