Effects of roasting conditions on the physicochemical properties and volatile distribution in perilla oils (Perilla frutescens var. japonica).

Unlabelled: Perilla seeds have more than 60% of α-linolenic acid, one of omega-3 essential fatty acids. Headspace volatiles and physicochemical properties including color, fluorescence intensity, and the oxidation products in perilla oil (PO) from perilla seeds roasted at different conditions were analyzed. Roasting temperature was 150, 170, 190, and 210°C, and roasting time was 15 and 30 min at each roasting temperature. PO from higher roasting temperature and longer roasting time had lower L* values, higher a*, b*, and chroma values, more brown pigments and fluorescence intensity, and more conjugated dienoic acids. Pyrazines were major volatiles in PO, and furans, sulfur-containing compounds, and hydrocarbons were also detected by a solid phase microextraction gas chromatography/mass spectrometry. In PO, 2,5-Dimethylpyrazine and 2-furancarboxaldehyde were 2 major volatiles. The principal component analysis of volatiles showed the 1st principal component (PC1) and the 2nd principal component (PC2) express 56.64% and 22.72% of the volatile variability in PO, respectively, which can differentiate PO prepared from roasting conditions clearly. Some physicochemical properties especially brown pigment and volatiles were positively correlated with each other in PO.

Practical Application: Perilla oil (PO) from perilla seeds possesses more than 60% of α-linolenic acid, one of omega-3 fatty acids. Roasting process has been used to extract oil from perilla seeds. Understanding physicochemical properties of PO from diverse roasting conditions are important steps to produce PO in food industry. Roasting process induces darkening of color, increase of fluorescence intensity, and brown pigments in PO. Pyrazines and furans are major headspace volatiles in PO roasted above 170°C. The results of this study can help to produce PO in industrial scales with desired headspace volatiles, colors, and oxidative state.