## 3 Results and Discussion
### Changes in VOCs in millet Huangjiu
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Compound** & **RI (ref) a** & **RI (cal) b** & **CAS** & **Odor Descriptor** & **Identification c**  \\ \hline _Esters_ & & & & & \\ Ethyl acetate & 887 & 880 & 141-78-6 & Fruity, sweet & MS, RI \\ Ethyl butanoate & 1026 & 1044 & 105-54-4 & - & MS, RI \\
3-Methylbutyl acetate & 1132 & 1121 & 123-92-2 & Banana-like, fruity & MS, RI \\ Pentyl acetate & 1175 & 1181 & 628-63-7 & Pear, overripe banana & MS, RI \\ Ethyl hexanoate & 1241 & 1232 & 123-66-0 & Fruity, pineapple-like & MS, RI \\ Ethyl lactate & 1341 & 1352 & 97-64-3 & Fruity, pineapple & MS, RI \\ Ethyl heptanoate & 1352 & 1341 & 106-30-9 & Banana, strawberry & MS, RI \\ Butyl hexanoate & 1407 & 1421 & 626-82-4 & Fruity, pineapple & MS, RI \\ Ethyl octanoate & 1441 & 1435 & 106-32-1 & Pineapple, mushroom & MS, RI \\ Ethyl nonanoate & 1526 & 1541 & 123-29-5 & Waxy, soapy, grape & MS, RI \\ Isobornyl acetate & 1582 & 1552 & 125-12-2 & Herbal, citrus nuance & MS, RI \\ Isoamyl lactate & 1619 & 1603 & 19329-89-6 & Fruity, creamy, nutty & MS, RI \\ Ethyl decanoate & 1648 & 1633 & 110-38-3 & Soapy, pear-like & MS, RI \\ Diethyl succinate & 1687 & 1669 & 123-25-1 & - & MS, RI \\ Phenethyl acetate & 1820 & 1813 & 103-45-7 & Sweet, honey, floral & MS, RI \\ Ethyl dodecanoate & 1847 & 1856 & 106-33-2 & Waxy, soapy & MS, RI \\ \(\gamma\)-Nonanolactone & 2020 & 2010 & 104-61-0 & Coconut, creamy & MS, RI \\ Ethyl tetradecanoate & 2070 & 2059 & 124-06-1 & Sweet, creamy & MS, RI \\ Ethyl pentadecanoate & 2161 & 2179 & 41114-00-5 & Honey sweet & MS, RI \\ Ethyl hexadecanoate & 2270 & 2288 & 628-97-7 & Waxy, fruity, creamy & MS, RI \\ Ethyl oleate & 2476 & 2452 & 111-62-6 & Fatty, butterery & MS, RI \\ Ethyl linoleate & 2510 & 2521 & 544-35-4 & Fatty, fruity, oily & MS, RI \\ \hline _Aldehydes_ & & & & & \\ Hexanal & 1083 & 1079 & 66-25-1 & Green, grassy & MS, RI \\ Heptanal & 1186 & 1180 & 111-71-7 & Citrus-like, fatty & MS, RI \\ (E)-2-Heptenal & 1334 & 1338 & 18829-55-5 & Green-apple-like & MS, RI \\ Nonanal & 1382 & 1379 & 124-19-6 & Citrus-like, soapy & MS, RI \\ (E)-2-Octenal & 1425 & 1430 & 2548-87-0 & Fatty, nutty & MS, RI \\ Furfurral & 1470 & 1474 & 98-01-1 & Sweet, cereal-like & MS, RI \\ Decanal & 1486 & 1485 & 112-31-2 & Fatty, orange peel & MS, RI \\ Benzaldehyde & 1533 & 1525 & 100-52-7 & Bitter-almond-like, & MS, RI \\ Undecanal & 1593 & 1611 & 112-44-7 & - & MS, RI \\
4-Methyl- benzaldehyde & 1653 & 1643 & 104-87-0 & - & MS, RI \\ \hline _Acids_ & & & & & \\ Acetic acid & 1445 & 1451 & 64-19-7 & Vinegar-like & MS, RI \\ Pentanoic acid & 1736 & 1750 & 109-52-4 & Acidic, milky, cheese & MS, RI \\ Hexanoic acid & 1861 & 1854 & 142-62-1 & Sweaty & MS, RI \\ Octanoic acid & 2082 & 2075 & 124-07-2 & Carrot-like, musty & MS, RI \\ nonanoic acid & 2164 & 2176 & 112-05-0 & Moldy, pungent & MS, RI \\ Decanoic acid & 2268 & 2284 & 334-48-5 & Soapy, musty & MS, RI \\ \hline _Ketones_ & & & & & \\
2-Octanone & 1297 & 1283 & 111-13-7 & Soapy, fruity & MS, RI \\
2-Nonanone & 1403 & 1389 & 821-55-6 & Fruity, musty & MS, RI \\ \hline _Phenols_ & & & & & \\
2-Methoxy-phenol & 1865 & 1837 & 90-05-1 & - & MS, RI \\
4-ethyl-2-methoxyphenol & 2048 & 2054 & 2785-89-9 & Smoky, gammon-like & MS, RI \\
2-methoxy-4-vinylphenol & 2180 & 2184 & 7786-61-0 & Smoky, clove-like & MS, RI \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._The use of principal component analysis (PCA) is a popular unsupervised multivariate statistical technique that reduces the dimensionality of complex multivariable data by integrating a small number of variables, known as principal components. This technique is commonly used to visualize and determine the main sources of variability in a dataset. In this study, PCA was employed to investigate the influence of protein fortification, specifically glutelin and albumin addition, on the volatile profiles of various millet Huangjiu samples.