**1. Introduction**

Food quality, especially the taste of food, is affected by numerous chemical components. Metabolomic analysis has been used to select biomarkers from numerous metabolites. Therefore, the relationship between metabolomic profiling and food quality has been investigated to identify quality-related components. Previous reports showed that the metabolomic profiles of foods such as fermented alcoholic beverages [1], soybeans [2], and tomatoes [3], strongly affect their taste.

Metabolomic analyses of meat have also been conducted to identify quality-related components. The relationships between metabolomic profiles and processing conditions of hams [4], the muscle type of pork [5], and the sensory perceptions of pork [6] have been reported. In addition, metabolome studies of beef have shown that metabolomic profiles were affected by geographical origin [7], breed [8,9], storage conditions [10], and aging periods [11].

Japanese Black cattle, also called Wagyu, are characterized by their grea<sup>t</sup> capacity for intramuscular adipose tissue accumulation [12,13]. The high intramuscular adipose tissue content of beef, called marbling, improves the texture, juiciness, and tenderness of Wagyu beef [13]. In sensory tests, Wagyu beef had significantly higher sensory characteristic scores than beef from other cattle breeds [14,15]. Interestingly, Wagyu beef has a characteristic sweet aroma and sweet taste that are not detected in other cattle breeds in sensory tests [15–17]. Previous reports indicated that the sweet aroma of Wagyu beef was affected by the lactone and decenal components [18,19]. However, the metabolomic biomarkers discerning the breed differences in beef, especially the characteristic sweet taste of Wagyu beef, have remained unclear. Holstein cattle are categorized as a dairy breed, and Holstein beef is characterized as lean meat [20,21]. Previous sensory test results have indicated breed differences between sensory characteristic scores of Wagyu and Holstein beef [14,15]. Therefore, to elucidate the breed differences in beef taste, a comparison of Wagyu and Holstein is thought to be the optimal model. In the present study, we conducted a metabolomic analysis of longissimus muscle (sirloin) samples from Wagyu and Holstein cattle to identify the metabolomic biomarkers characterizing the breed di fferences in beef taste.
