# Highland Barley Replaces Sorghum as Raw Material to Make Shanxi Aged Vinegar
###### Abstract  
Highland barley (HB, _Hordeum vulgare_ L. var. _nudum_ Hook. f.), also known as naked or hullness barley, is a kind of cereal crop growing at high altitudes (4200-4500 m) around the world. In this study, HB vinegar (HBV) was prepared, using Tibetan HB as the main raw material, according to the process of Shanxi aged vinegar (SAV), a famous vinegar in China, in which sorghum is usually used as the main raw material. The related main compounds, such as alcohol and acetic acid, in the alcohol and acetic acid fermentation processes were monitored and analyzed, respectively. The flavor components in the aged vinegars were analyzed by headspace solid-phase microextraction, combined with gas chromatography-mass spectrometry, and compared with sorghum vinegar (SV), which was made, using sorghum as the raw material, based on the SAV process. The results revealed that at the alcohol fermentation stage, the alcohol content of HB mash was higher than that of the sorghum mash (\(p\) < 0.05), and at the acetic acid fermentation stages of HBV and SV, the total acid contents were 6.23 and 5.81 (g:100 mL\({}^{-1}\) and \(p\) < 0.05), respectively. After aging one and a half years, the contents of non-volatile acid, volatile acid, and ester compounds in HBV were higher than those in SV. Therefore, HB can replace sorghum as the raw material for making SAV. Based on a literature search, the comparison and analysis of the main components and volatile flavor compounds of HBV and SV were not studied before.  
highland barley; Shanxi aged vinegar; flavor compounds; gas chromatography-mass spectrometry +
Footnote †: journal: Applied Sciences  
Vinegar, as a sour seasoning, is widely used in diets around the world. Due to the differences in regions, raw materials, and technologies, there are distinct varieties of vinegar in different countries and regions [15]. Generally, in Western countries such as Italy, Spain, Germany, the United States, and so on, vinegas are made mainly from fruits, including grape and apple, through liquid-state fermentation, and, thus, are called fruit vinegars [16]. In Eastern countries, such as China, Japan, and Korea, etc., vinegas are made mainly from sorghum, rice, corn, wheat or other cereals rich in starch by solid-state fermentation (SFP), and, thus, are called cereal vinegars [17]. In China, there are various kinds of cereal vinegars [18]. Among them, Shanxi aged vinegar (SAV) is one of the most famous cereal vinegars produced by SFP, and it is usually produced with sorghum as the main raw material, and bran, rice or millet husk as auxiliary materials. In the SAV process, some unique processes occur, for instance, after acetic acid fermentation (AAF), about 30% vinegar paste (called _Cupei_,  
10 days in the ceramic container, turning over the vinegar paste twice a day. Then, 30% vinegar paste is heated for 5 days, during which the temperature of the vinegar paste is gradually increased from 30 \({}^{\circ}\)C to 90 \({}^{\circ}\)C in the first 3 days, then decreased to 30 \({}^{\circ}\)C on the fifth day, resulting in a color change from light yellow to brown. Finally, the heated vinegar paste is blended with the unheated vinegar paste (about 70%), and leached with saline to obtain the new (fresh) vinegar, which is aged for one and a half years in an open pottery container, into aged vinegar.