# Volatile Compounds, Sensory Profile and Phenolic Compounds in Fermented Rice Bran
## 3 Discussion  
Phenolic compounds are widely found in plant products and they have antioxidant properties [10]. Our results showed that an increase in RSA was related to an increase in TPC, suggesting that TPC is responsible for antioxidant activities. _R Rhizopus oligosporus_ have been reported to be able to produce enzymes such as \(\beta\)-glucosidase, amylase, cellulase, chitinase, inulinase, phytase, xylanase, tanase, esterase, invertase or lipase that can enhance bran cell wall degradation, thus producing more free phenolic compounds. In addition, several studies have reported that phenolic acids, flavonoids, anthocyanins and others also contribute to the antioxidant activity of RB [27; 28; 29]. Another study showed that during  
Figure 3: (**a**) Hierarchical Clustering Map; (**b**) Preference Mapping; and (**c**) Overall Acceptance (frequency panelist) of fermented and non-fermented rice bran. 534: Benchmark (Control), 192: CIF, 736: CINF, 298: IPR30F, and 375: IPR30 NF. ferentation, there was an increase in the content of chlorogenic acid, p-hydroxybenzoic acid, gallic acid, and ferulic acid vanillin in RB [10]. In this study, ethanol was significantly higher in most of the fermented RB. Ethanol is mainly formed from the fermentation process, and is derived from pyruvate through acetyl-CoA, whereas it is derived from the pentose phosphate pathway of glucose [23]. 3-methyl-3-buten-1-ol and 2-ethyl-1-hexanol contribute to sweaty, fruity, citrus, and oily aromas, respectively. Linalool was only found in CI non-fermented RB and contributed to citrus, greeny, and waxy aromas. Benzyl alcohol are formed via reduction of benzoic acid during fermentation through the glycolysis pathway [30] was higher in fermented RB. Phenylethyl alcohol are formed via hydrolysis of phenylethyl acetal and phenylethyl ester contributed to aroma floral and slightly rose [31; 32]. Eugenol was found in all samples of fermented and non-fermented RB. Eugenol contributed to a sweet, clove-like, green aroma [33]. 2,3-butandiol, 3-methyl-3-butenol, benzyl alcohol and 2-furanmetanol are the main alcohol compounds and were formed in both IPR30 and CI fermented RB, including in CI non-fermented RB. Acids are formed through the pentose phosphate pathway and the TCA cycle [34]. Furthermore, the acid group in this study was probably derived from aldehyde oxidation and lipid hydrolysis [35]. The present study showed that acetic acid produced a sour aroma in RB (Table 2). Hexanoic and octanoic acids contributed to sweaty and cheesy aromas (Table 2), while nonanoic acid contributed to greeny and fatty aromas (Table 2) [22; 36]. The relative area of acetic acid is seen at higher levels in IPR30 non-fermented and CI fermented RB (Table 2). Acetic acid is also known to originate from the oxidation of acetaldehyde [34]. Ketones were detected in fermented RB, such as butenone, 4-hydroxybutan-2-one, 1-(1H-pyrrol-2 yl) ethanone, 2-pyrrolidinone, and 6,10,14-trimethyl-2-pentadecanone. Ketones can give a pleasant aroma [37]. They can produce caramel, nutty, walnut, bready, oily, and herby aromas (Table 2), and are formed from fatty acids by enzymatic oxidative decarboxylation [21; 22]. Esters, which have a fatty, waxy, and oily aroma (Table 2), are formed by esterification between alcohols and acids in fermentation [22]. The current study determined four esters, methyl tetradecanoate, hexadecanoic acid methyl ester, methyl (E)-octadec-9-enoate, and methyl (9Z,12Z)-octadec-9,12-dienoate, in the fermented RB samples (Table 2), although they were present at low concentrations. The compounds of methyl (E)-octadec-9-enoate, and methyl (9Z,12Z)-octadec-9,12-dienoate were not detected in CI non-fermented RB. An interesting finding of the present study was that 2-pentylfuran, which has a greeny, beany, and buttery aroma (Table 2), has been reported as one of the odor-active compounds in various rice cultivars [22]. This compound was only detected in non-fermented IPR30.