Identiﬁcation and Characterization of Volatile Components Causing the Characteristic Flavor of Wagyu Beef (Japanese Black Cattle) Satsuki Inagaki,* Yohei Amano, and Kenji Kumazawa Ogawa & Company, Ltd., 15-7 Chidori Urayasushi, Chiba 279-0032, Japan ABSTRACT: To clarify the characteristic sweet aroma of Wagyu (Japanese Black Cattle), aroma extraction dilution analysis (AEDA) was applied to the volatile fractions of Wagyu and Australia beefs. Some 20 odor-active peaks were detected, and 17 odorants were identiﬁed or tentatively identiﬁed. Among the perceived odorants, most of them were newly identiﬁed from the Wagyu beef. The main constituents of the potent odorants were aldehydes and ketones, which are known as the degradation products of polyunsaturated fatty acids that were signiﬁcantly included in the lipids of the Wagyu. In addition, the most potent odorant was trans-4,5-epoxy-(E)-2-decenal, which is known to be the oxidation product of polyunsaturated acids, such as linoleic acid and arachidonic acid, that were signiﬁcantly included in the lipids of the Wagyu. Accordingly, these ﬁndings strongly suggested that the kind of fatty acid constituting lipids of the Wagyu plays an important role in the formation of the characteristic aroma of the Wagyu beef. KEYWORDS: Wagyu beef aroma, unsaturated fatty acid, aldehyde, aroma extract dilution analysis (AEDA)
INTRODUCTION Wagyu beef (Japanese Black Cattle) has a high popularity in Japan due to its delicious ﬂavor and is one of the domestic agricultural product brands which has become very popular overseas in recent years. Wagyu cattle are the result of improving the native cattle in Japan bred before the Meiji period (A.D. 1868) for edible meat, and they are registered by managing their certiﬁcates such as blood, breeding, and so forth. Four kinds are registered as Japanese Wagyu, which are the Japanese Black, Japanese Brown, Japanese Shorthorn, and Japanese Polled Cattle. However, more than 95% of the Wagyu is the Japanese Black Cattle. For example, the Matsusaka beef, which is a famous brand beef, belongs to the Japanese Black Cattle. The characteristics of the Wagyu beef are said to be its soft texture and a characteristic ﬂavor during eating, and it has been reported that its aroma is important to perceive this ﬂavor.1 In addition, a suitable aroma formation requires optimal conditions (high level of fat-marbling, aging in the presence of oxygen, and optimal cooking temperature).1 Therefore, to clarify the aroma components of the delicate Wagyu in this way, it is signiﬁcantly important to select the optimal analysis method. The potent odorants of Wagyu beef have already been reported, and it was believed that a lactone was the most important characteristic odorant for the Wagyu beef.2 However, this result was obtained by a simultaneous distillation extraction (SDE) method under atmospheric pressure; therefore, this sample preparation technique did not use the optimal cooking temperature. Therefore, it is still unclear as to the actual signiﬁcance of the odorants regarding the characteristic aroma of the Wagyu beef. The objective of the present investigation was to elucidate the potent odorants of the characteristic ﬂavor of Wagyu beef by a comparative aroma extract dilution analysis (cAEDA) using Wagyu beef and another kind of beef (grass-fed Australia © 2017 American Chemical Society
beef). Furthermore, the formation mechanism of the characteristic aroma of the Wagyu beef was discussed based on these revealed potent odorants.
MATERIALS AND METHODS
Materials. Three kinds of beefs were used. Matsusaka beef (a kind of Wagyu, ribeye), grass-fed Australia beef (loin), and USA beef (sirloin) were purchased from the Maruyoshi Shoji Corporation (Chiba, Japan). These beefs were matured to a suitable condition for eating and then cut into thin slices. After the purchase, the meats were stored at −25 °C and subsequently allowed to thaw overnight at 5 °C prior to the investigation. The sliced meat was vacuum packed, and then heated in a water bath at 80 °C for 2 min. The Matsusaka beef and Australia beef were used for the AEDA, and the USA beef was used for the determination of the unknown compound. Chemicals. The following compounds were synthesized according to literature procedures: 12-methyltridecanal;3 trans-4,5-epoxy-(E)-2decenal;4 and (E,Z,Z)-2,4,7-tridecatrienal.5 Compounds (Table 1) nos. 1−6, 9−11, 14, and 18 were obtained from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan); no. 8 was obtained from Sigma-Aldrich Japan (Tokyo, Japan). Isolation of the Volatiles from the Heated Beef. The heated beef (15 g) in distilled water (15 g) was homogenized in a blender to produce a slurry. The beef slurry (15 g) was extracted with diethyl ether (20 mL) at room temperature by strong shaking for 5 min. The residual substances and solvent were separated by centrifuging at 3000 rpm for 10 min at 20 °C. The internal standard solution (5 μL) prepared from 300 ppm (w/v) methyl nonanoate in methylene chloride was added to the solvent extract and then dried over anhydrous Na2SO4. To remove the nonvolatile material, the solvent extract was distilled under reduced pressure (40 °C at 5 × 10−3 Pa) using the solvent assisted ﬂavor evaporation (SAFE) technique.6 The distillate was dried over anhydrous Na2SO4; then the solvent was removed by rotary evaporation (35 °C at 550 mmHg) to Received: Revised: Accepted: Published: 8691
June 20, 2017 September 8, 2017 September 10, 2017 September 10, 2017 DOI: 10.1021/acs.jafc.7b02843 J. Agric. Food Chem. 2017, 65, 8691−8695
Journal of Agricultural and Food Chemistry Table 1. Potent Odorants Showing FD Factors (FD ≥ 4) in the Diﬀerent Kind of Beefs FD factor no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20