Volatile compounds of perilla seed oils roasted at different temperatures (150-190°C) were analyzed by dynamic headspace gas chromatography-mass spectrometry. The headspace volatiles in roasted perilla seed oils (RPSO) were composed of thermally produced flavors and compounds originating from the raw perilla seeds. The roasting temperatures significantly affected the production of thermal reaction flavors. Oils from parilla seeds roasted below 170°C had relatively high concentrations of aldehydes, whereas pyrazines and furans were the predominant volatiles above 170°C. In all of the RPSO, the contents of both perilla aldehyde and perilla ketone remained almost constant and might be used to discriminate perilla seed oils from other roasted vegetable seed oils.Perilla seed [Perilla frutescens (L.) Britt.] is composed of 40-45% (w/w) oil with a high α-linolenic acid (n-3 fatty acid) content (1). Roasted perilla seed oils (RPSO) are widely used as condiment oils in Asian countries, especially in Korea and China, because of their roasted, nutty, and distinctive aromas, reminiscent of perilla aldehyde. Similar to sesame seed oils, RPSO are traditionally tailor-made by roasting, mechanical pressing, and simple refining from the raw perilla seeds. The roasting process may be a critical step for producing perilla seed oils because many aromatic compounds may be produced by the heat treatment that has an effect on the flavor quality of RPSO. Flavor profiles of RPSO are generally changed under different roasting temperatures (2). There have been no detailed reports yet, however, on the volatile components of RPSO. Hence, the objective of the present study was to identify the volatile compounds of RPSO and to investigate the effects of roasting temperature on the production of headspace volatile flavor components of RPSO.
MATERIALS AND METHODS
Materials.Perilla seeds were obtained from local areas in Korea. Total lipids of perilla seeds extracted with diethyl ether in a Soxhlet apparatus for 12 h were 44.5 % (w/w). Standard chemicals for identification of volatiles in gas chromatography (GC) and mass spectra were purchased from Aldrich Chemical Company (Milwaukee, WI) Sigma Chemical Co. (St. Louis, MO), and Fluka Chemie AG (Buchs, Switzerland). Iso-octane, used as a dilution solvent of standard chemicals was obtained from Fisher Scientific (Norcross, GA).Preparation of RPSO and nonroasted perilla seed oils (NPSO). Perilla seeds were washed and dried to 6.4% (w/w) moisture content prior to roasting. The seeds (400 g) were roasted at 150, 160, 170, 180, and 190°C for 3 min using a continuous and circular monolayer roasting machine (Taewhan Automatic Instrument Co., Seoul, Korea). The roasted seeds were fed into the hopper immediately to minimize heat loss and expelled with a screw-type press at 60 rpm and 500 kg/cm 2 . The barrel temperature of a press during each run was maintained at 120°C. This process produced about 120 to 125 g of oil and cakes in the form of flakes with 0.6-mm thickness. Four replications for RPSO at ea...
