Changes in Antioxidant Activity During Enzyme Fermentation Ⅱ
Oct 29, 2024
4.2 Results and analysis
4.2.1 Total phenol content
Starting from the early stage of fermentation, the total phenol content was measured every 10 days, and the total phenol content change curves of apple enzyme, pear enzyme and citrus enzyme at different fermentation time periods were obtained, as shown in Figure 4.1.
Fig.4.1 The variation curves of total phenolic content
As shown in Fig. 4.1, as the fermentation time increases, the total phenolic content of the enzyme solution in the experimental group and the control group shows a significant upward trend, among which the total phenolic content of the apple enzyme is the highest. From the experimental results of the three different fruits, it can be seen that the variation trend of the total phenolic content of the enzyme after artificial inoculation of bacteria during the fermentation process closely follows that of the enzyme obtained by natural fermentation. Polyphenols are the main reason for the antioxidant activity. During the fermentation process, microorganisms convert complex macromolecular phenolic substances into small molecular phenolic substances[61]. Compared with the enzyme without adding bacteria, the total phenolic content of apple enzyme increased by 15% on the 60th day of fermentation, the total phenolic content of pear enzyme increased by 10.17%, and the total phenolic content of citrus enzyme increased by 30.85%.
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4.2.2 Reducing power
Starting from the early stage of fermentation, the reducing power of the enzyme was tested every 10 days, and the reducing power change curves of apple enzyme, pear enzyme and citrus enzyme at different fermentation time periods were obtained, as shown in Figure 4.2.
Fig.4.2 The variation curves of reducing power
As shown in Fig. 4.2, the reducing power of the enzyme in the experimental group is higher than that in the control group, but the increase is not very large. Research results show that reducing power is related to a variety of antioxidant mechanisms, such as the degradation of peroxides and the scavenging of free radicals by combining with metal ion catalysts [62-63]. Compared with the case without adding bacteria, the reducing power of apple enzyme increased by 1.8%, the reducing power of pear enzyme increased by 4.90%, and the reducing power of citrus enzyme increased by 17.57% on the 60th day of fermentation.
4.2.3 Superoxide anion free radical scavenging capacity
From the beginning of fermentation, the superoxide anion free radical scavenging rate was measured every 10 days, and the variation curves of superoxide anion free radical scavenging capacity of apple enzyme, pear enzyme and citrus enzyme at different fermentation time periods were obtained, as shown in Fig. 4.3.
Fig.4.3 The variation curves of superoxide anion free radical scavenging capacity
As shown in Fig. 4.3, the superoxide anion free radical scavenging capacity of the experimental group of apple enzyme was significantly higher than that of the control group. On the 50th day of fermentation, the superoxide anion free radical scavenging rate was 45.71%, reaching the maximum value during the experiment. During the whole fermentation process, the superoxide anion free radical scavenging rate of pear enzyme and citrus enzyme did not change significantly, and the scavenging capacity of the experimental group of citrus enzyme was weak. After adding bacteria, the changes in antioxidant capacity of different types of fruits during the fermentation process were the same. Nagendra Prasad et al. have shown that phenolic compounds with free hydroxyl groups and flavonoid compounds with 3-hydroxyl or polyhydroxyl substitutions on their A or B rings can all exhibit high superoxide radical scavenging abilities[64]. The strong superoxide anion radical scavenging ability of apple enzyme may be attributed to the high content of phenolic compounds. Compared with the case without the addition of bacterial strains, on the 60th day of fermentation, the superoxide anion radical scavenging ability of apple enzyme increased by 36.55%, the superoxide anion radical scavenging ability of pear enzyme increased by 5.44%, and the superoxide anion radical scavenging ability of citrus enzyme increased by 7.46%.
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4.2.4 Hydroxyl radical scavenging ability
From the beginning of fermentation, the hydroxyl radical scavenging rate of the enzyme was measured every 10 days, and the hydroxyl radical scavenging ability change curves of apple enzyme, pear enzyme and citrus enzyme at different fermentation time periods were obtained, as shown in Figure 4.4.
As shown in Figure 4.4, the hydroxyl radical scavenging ability of apple enzyme in the experimental group was lower than that of the control group, which may be caused by the degradation of active substances by microbial strains during the fermentation process. The hydroxyl radical scavenging ability of the citrus enzyme experimental group changed more significantly than that of pear enzyme. Citrus enzyme has a higher hydroxyl radical scavenging ability. At 40 days of fermentation, the scavenging rate reached the maximum within the experimental time range, with a maximum of 74.69%. Hydroxyl radicals are considered to be highly damaging and can exert their damaging power in almost every living cell[65]. Therefore, it is necessary to improve the hydroxyl radical scavenging ability. Compared with the fermentation without bacterial strains, on the 60th day of fermentation, the hydroxyl radical scavenging ability of apple enzyme decreased by 4.27%, the hydroxyl radical scavenging ability of pear enzyme increased by 2.67%, and the hydroxyl radical scavenging ability of citrus enzyme increased by 6.26%.
4.2.5 DPPH· free radical scavenging ability
Starting from the early stage of fermentation, the DPPH· free radical scavenging rate of the enzyme was measured every 10 days, and the DPPH· free radical scavenging ability change curves of apple enzyme, pear enzyme and citrus enzyme at different fermentation time periods were obtained, as shown in Figure 4.5.
As shown in Figure 4.5, the DPPH· free radical scavenging ability of apple enzyme, pear enzyme and citrus enzyme in the experimental group with added bacteria changed significantly compared with the control group. The DPPH· free radical scavenging rate of both the experimental group and the control group reached the maximum on the 60th day of fermentation. The DPPH·free radical scavenging rate of apple enzyme in the experimental group was 80.23% on the 60th day, 59% higher than the DPPH·free radical scavenging rate of 50.3% in the control group on the same day; the DPPH·free radical scavenging rate of pear enzyme in the experimental group was 70.98% on the 60th day, 39.78% higher than the DPPH·free radical scavenging rate of 50.78% in the control group on the same day; the DPPH·free radical scavenging rate of citrus enzyme in the experimental group was 96.93% on the 60th day, 38.08% higher than the DPPH·free radical scavenging rate of 70.2% in the control group on the same day. Artificial inoculation of four strains of beneficial fermentation is of great help in improving the DPPH·free radical scavenging ability of enzymes.
4.2.6 ABTS free radical scavenging ability
From the beginning of fermentation, the ABTS free radical scavenging rate of the enzyme was measured every 10 days, and the ABTS free radical scavenging ability change curves of apple enzyme, pear enzyme and citrus enzyme at different fermentation time periods were obtained, as shown in Figure 4.6.
As shown in Figure 4.6, the change patterns of ABTS free radical scavenging ability of apple enzyme, pear enzyme and citrus enzyme are different. Apple enzyme and citrus enzyme almost increase first, then decrease, and then decrease again. Pear enzyme has been on an upward trend throughout the fermentation period presented in the experiment. Compared with the addition of strains, on the 60th day of fermentation, the ABTS free radical scavenging ability of apple enzyme increased by 3.10%, the ABTS free radical scavenging ability of pear enzyme increased by 6.84%, and the ABTS free radical scavenging ability of citrus enzyme increased by 4.76%.
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4.3 Summary of this chapter
Based on the study of the antioxidant activity of apple enzymes at different concentrations in the previous chapter, this chapter adds pear enzymes and apple enzymes, and compares the three enzymes by artificial inoculation and natural fermentation. The experimental results show that with the extension of fermentation time, the total phenol content, reducing power and free radical scavenging ability of the enzymes generally show an upward trend. Compared with the apple enzymes without added strains, the total phenol content increased by 15%, the reducing power increased by 1.8%, the superoxide anion free radical scavenging ability increased by 36.55%, the hydroxyl free radical scavenging ability decreased by 4.27%, the DPPH free radical scavenging rate increased by 59%, and the ABTS free radical scavenging ability increased by 3.10% on the 60th day of fermentation.
Compared with the unadded strains, the total phenol content of pear enzyme added strains increased by 10.17% on the 60th day of fermentation, the reducing power increased by 4.90%, the superoxide anion radical scavenging ability and hydroxyl radical scavenging ability increased by 5.44% and 2.67% respectively, the DPPH· radical scavenging rate increased by 39.78%, and the ABTS radical scavenging ability increased by 6.84%.
Compared with the unadded strains, the total phenol content of citrus enzyme added strains increased by 30.85% on the 60th day of fermentation, the reducing power increased by 17.57%, the superoxide anion radical scavenging ability increased by 7.46%, the hydroxyl radical scavenging ability increased by 6.26%, the DPPH· radical scavenging rate increased by 38.08%, and the ABTS radical scavenging ability increased by 4.76%.
