## 2 Results and Discussion  
### Changes in Polyphenols, Flavonoids and Polysaccharides during fermentation  
The total phenolic content of noni juice produced over different fermentation times is shown in Figure 1a. The total phenolic content of the fresh juice (0 day, F0) was \(168.35\pm 3.54\) mg GAE/100 mL. Over the 63-day fermentation, the total phenolic content first decreased, then increased, before decreasing again. The concentration of total phenols reached its lowest level in L56 and F21 (\(125.93\pm 12.02\) mg GAE/100 mL and \(156.02\pm 6.20\) mg GAE/100 mL, respectively). The highest total phenolic contents were 199.77 \(\pm\) 8.12 mg GAE/100 mL and 185.60 \(\pm\) 5.20 mg GAE/100 mL in L28 and F28, respectively. The contents of polyphenols showed significant changes in both the laboratory- and factory-scale fermentation process. Moreover, there were significant differences in the phenolic contents on day 7, 14, 21, 35, 49, 56 and 63 of fermentation between the laboratory- and factory-scale fermentation. As shown in Figure 1b, the flavonoid content showed an increasing trend during the 63-day fermentation of laboratory- and factory-scale fermentation processes. Compared with the fermented juice, the flavonoid content of the fresh noni juice was the lowest (\(26.07\pm 0.54\) mg RE/100 mL). The flavonoid content reached its highest value of 36.73 \(\pm\) 2.51 mg RE/100 mL on day 63 of laboratory-scale fermentation. The highest flavonoid content of factory-scale fermentation was 43.28 \(\pm\) 1.66 mg RE/100 mL on day 49, after which it decreased. During the whole fermentation process, the flavonoid content of factory-scale fermentation was commonly higher than the laboratory-scale fermentation. After 35 days of fermentation, there was a significant difference in flavonoid content between the two fermentation scales. During the fermentation of juice, the species and quantity of microorganisms contribute to the sensory quality and the transformation of bioactive components [20,21]. Microorganisms metabolize food and transform polyphenols through complex enzyme systems during juice fermentation [22]. Previous studies showed that the contents of hydroxycinnamic acids and anthocyanins were decreased and the total concentration of flavanols was increased during black current juice fermentation [23]. The total content of flavonoids was reported to increase during _Dendrobium officinal_ and banana juice fermentation by lactic acid bacteria [24]. The change of polyphenols and flavonoids content may be due to the intricate polyphenols being broken down by enzymes into simpler flavanols during fermentation [25,26]. This result is consistent with the observations of [PERSON] et al. [23], who reported an increase in flavanols and a decrease in total content of polyphenols during yeast fermentation. As shown in Figure 1c, the content of polysaccharides in fresh noni juice (day 0) was 6.45 \(\pm\) 0.71 mg/mL. The content of polysaccharide showed a downward trend during the first 42 days of fermentation and reached a low of 2.11 \(\pm\) 0.71 mg/mL on day 42, then increased to a high of 6.28 \(\pm\) 2.48 mg/mL on day 56 of the laboratory-scale fermentation. During the factory-scale fermentation, the polysaccharide content initially increased but then decreased. The polysaccharide content reached the highest value of 8.66 \(\pm\) 0.30 mg/mL on day 7 and decreased to relatively low values, at day 42 to 63, of 4.61 \(\pm\) 0.96 mg/mL-3.57 \(\pm\) 1.10 mg/mL. Polysaccharide is considered to be one of the main bioactive components of fermented noni juice [1]. Hydrolytic enzymes produced by microorganisms can degrade the insoluble pecto-cellulosic cell wall into soluble polysaccharides and break polysaccharides down into  
Figure 1: Changes in the total phenols (**a**), flavonoids (**b**) and polysaccharides (**c**) content during laboratory- and factory-scale fermentation. Different letters in the same line represent significant differences at \(p<0.05\).