Changes Occurring in the Volatile Constituents of Flaxseed Oils (FSOs) Prepared with Diverse Roasting Conditions

The roasting process is the most significant factor in forming the final flavor character of FSO. A wide variety of volatile constituents in FSO prepared from flaxseeds that were roasted at different temperatures are evaluated by head‐space solid phase micro‐extraction (HS‐SPME) coupled with GC‐MS. There are 69 volatile constituents that are tentatively identified, and the sensory variance analysis indicates that all of the FSO samples gives comparable intensity values for the “oily” and “herbaceous”aroma descriptors, and the odor profiles of the FSO samples differed significantly with regards to the “roasted” and “almond” aromas ( p < 0.05). The principal component analysis (PCA) of the volatiles showed the first principal component (PC‐1) and the second principal component (PC‐2) express 84 and 9% of the volatile component variability in the FSO, respectively, which can clearly differentiate FSOs prepared from different roasting conditions. Additionally, the loadings plot further shows that the RFSO correlated more with three groups of volatile constituents according to the degree of roasting (with the total numbers and numbers of specific compounds between brackets): aldehydes (19:2, (E, E)‐2,4‐pentadienal, (E, E)‐2,4‐heptadienal), ketones (9:3,2‐hexanone, (E)‐3‐octen‐2‐one, 5‐methyl‐2(5H)‐furan‐one), and heterocyclic compounds (11:4, 2,3‐dimethylpyrazine, trimethylpyrazine, 2‐ethyl‐furan, 2‐ethyl‐6‐methylpyrazine). Practical Applications : Monitoring of the roasting process is an unavoidable task to obtain the desired volatiles and taste to ensure RFSO quality constant at an industrial level. In general, the most adopted indicator to control the degree of roasting in industry is visual inspection, which may not be accurate for the quality evaluation because RFSO presented the same average color value although they are derived from different roasted degree. Different resources will imply in variable volatile constituents for the same type of flaxseeds. It is therefore known that FSOs produced from different roasting processing may be differentiated by their volatile constituents. The results show that the major volatile constituents can be used as chemical markers to distinguish different processed RFSO by the PCA method. The roasting process contributes the most in forming the final flavor character of flaxseed oils (FSOs). By increasing the roasting temperature, the color of FSOs changed gradually from light yellow (0–40 min) to brown (40 min) and finally to deep‐brown (50 min). A wide variety of volatile compounds in FSOs are evaluated and compared with those of unroasted FSO by HS‐SPME‐GC‐MS and sensory variance. The sensory variance analysis indicates that the odor profiles of FSO samples differed significantly with regards to the “roasted” and “almond” aromas ( p < 0.05). PCA analysis can clearly differentiate FSOs prepared from different roasting conditions.