Correction to: Scientific Reports 10.1038/s41598-024-74738-1, published online 14 October 2024
The original version of this Article contained errors in the values of the phytochemical and antioxidant analysis.
Consequently, in the Results and discussion section, under the subheading ‘Phytochemical analysis’,
“The TPC values varied across the different treatment groups, ranging from 947.95 ± 11.72 to 1304.77 ± 9.50 µg GAE/g of DM. The control group had a TPC of 1164.32 ± 15.63 µg GAE/g of DM. Most treatment groups showed an increase in phenolic content compared to the control group, with T-1 exhibiting the highest TPC at 1304.77 ± 9.50 µg GAE/g of DM, followed by T-2, T-7, T-5, T-4, T-3, T-6, and T-8 in decreasing order (Fig. 1a). In contrast, the T-9 group showed a significant decrease in phenolic content compared to the control. These results indicate that microwave parameters have a notable impact on the total phenolic content of the treated DORB samples, highlighting the importance of optimizing these parameters to enhance nutritive value. The treatment-specific influence on TPC aligns with the findings of Pokkanta et al.8 in rice bran. They reported that microwaving at 260 watts for 0.5 to 3 min and at 440 watts for 0.5 to 2.5 min resulted in a maximum increase in phenolic content, while a decrease occurred at 880 watts. This study corroborates those findings, as the highest TPC was observed with the 300 watts for 3 min treatment (T-1), while a significant reduction was seen in the 800 watts for 5 min treatment (T-9). The reduction in T-9 might be due to the degradation of phenolics caused by prolonged exposure to high temperatures. The effectiveness of the 300 watts for 3 min microwave treatment in enhancing phenolic content could be attributed to factors such as the release of bound phenolics through the breakdown of cell walls and minimal thermal damage to bioactive compounds during the process45.
The TFC varied among the different treatment groups, ranging from 482.73 ± 9.96 to 916.82 ± 16.29 µg QE/g of DM, with the control group having a TFC of 900.91 ± 11.5 µg QE/g of DM. Most treatment groups showed a significant increase in flavonoid content compared to the control. The T-6 treatment group exhibited the highest TFC, followed by T-4, T-7, T-1, T-2, T-5, and T-3 (Fig. 1b). A significant decrease in flavonoid content was observed in the T-9 group, while the TFC of T-8 was comparable to the control. The decrease in T-9, which involved treatment at 800 watts for 5 min, is likely due to the degradation of flavonoids caused by prolonged exposure to high-intensity microwaves13,46. A similar wattage-time -dependent variation in TFC in microwaved rice bran was also reported by Pokkanta et al.8 The flavonol content ranged from 6.59 ± 0.77 to 43.35 ± 0.88 µg CE/g of DM among the treated samples, whereas the control group had a much lower flavonol content of 1.87 ± 0.22 µg CE/g of DM. All treated samples exhibited a significant (p < 0.05) increase in flavonol content compared to the control, indicating that microwave treatment positively influenced flavonol levels in DORB. The highest flavonol content was observed in the T-7 group (800 watts for 1.5 min), which yielded a concentration of 43.35 ± 0.88 µg CE/g of DM, followed by T-6, T-5, T-4, T-3, T-2, T-1, T-8, and T-9 (Fig. 1c).”
now reads:
“The TPC values varied across the different treatment groups, ranging from 1743.69 ± 3.2 to 3879.31 ± 24.67 µg GAE/g of DM. The control group had a TPC of 2082.75 ± 5.58 µg GAE/g of DM. Most treatment groups showed an increase in phenolic content compared to the control group, with T-1 exhibiting the highest TPC at 3879.31 ± 24.70 µg GAE/g of DM, followed by T-2, T-7, T-5, T-4, T-3, T-6, and T-8 in decreasing order (Fig. 1a). In contrast, the T-9 group showed a significant decrease in phenolic content compared to the control. These results indicate that microwave parameters have a notable impact on the total phenolic content of the treated DORB samples, highlighting the importance of optimizing these parameters to enhance nutritive value. The treatment-specific influence on TPC aligns with the findings of Pokkanta et al.8 in rice bran. They reported that microwaving at 260 watts for 0.5 to 3 min and at 440 watts for 0.5 to 2.5 min resulted in a maximum increase in phenolic content, while a decrease occurred at 880 watts. This study corroborates those findings, as the highest TPC was observed with the 300 watts for 3 min treatment (T-1), while a significant reduction was seen in the 800 watts for 5 min treatment (T-9). The reduction in T-9 might be due to the degradation of phenolics caused by prolonged exposure to high temperatures. The effectiveness of the 300 watts for 3 min microwave treatment in enhancing phenolic content could be attributed to factors such as the release of bound phenolics through the breakdown of cell walls and minimal thermal damage to bioactive compounds during the process45.
The TFC varied among the different treatment groups, ranging from 1946.36 ± 36.87 to 3105.45 ± 38.68 µg QE/g of DM, with the control group having a TFC of 2373.64 ± 47.20 µg QE/g of DM. Most treatment groups showed a significant increase in flavonoid content compared to the control. The T-6 treatment group exhibited the highest TFC, followed by T-4, T-7, T-1, T-2, T-5, and T-3 (Fig. 1b). A significant decrease in flavonoid content was observed in the T-9 group, while the TFC of T-8 was comparable to the control. The decrease in T-9, which involved treatment at 800 watts for 5 min, is likely due to the degradation of flavonoids caused by prolonged exposure to high-intensity microwaves13,46. A similar wattage-time -dependent variation in TFC in microwaved rice bran was also reported by Pokkanta et al.8 The flavonol content ranged from 14.30 ± 1.61 to 38.94 ± 1.94 µg CE/g of DM among the treated samples, whereas the control group had a much lower flavonol content of 10.07 ± 0.70 µg CE/g of DM. All treated samples exhibited a significant (p < 0.05) increase in flavonol content compared to the control, indicating that microwave treatment positively influenced flavonol levels in DORB. The highest flavonol content was observed in the T-7 group (800 watts for 1.5 min), which yielded a concentration of 38.94 ± 1.94 µg CE/g of DM, followed by T-6, T-5, T-4, T-3, T-1, T-2, T-8, and T-9 (Fig. 1c).”
In the same section, under the subheading ‘Antioxidant status’,
“The DPPH free radical scavenging activity varied among the treated samples, ranging from 559.64 ± 26.05 to 981.07 ± 4.52 µg AAE/g of DM, while the control group had a scavenging activity of 500.71 ± 33.70 µg AAE/g of DM. Most treatment groups showed a significant (p < 0.05) increase in DPPH free radical scavenging activity compared to the control. The highest activity was observed in treatment group T-1, with a value of 981.07 ± 4.52 µg AAE/g of DM, followed by T-2, T-3, T-7, T-4, T-6, and T-5 (Fig. 2a).”
now reads:
“The DPPH free radical scavenging activity varied among the treated samples, ranging from 397.14 ± 25.42 to 2854.29 ± 49.62 µg AAE/g of DM, while the control group had a scavenging activity of 818.57 ± 29.51 µg AAE/g of DM. Most treatment groups showed a significant (p < 0.05) increase in DPPH free radical scavenging activity compared to the control. The highest activity was observed in treatment group T-1, with a value of 2854.29 ± 49.62 µg AAE/g of DM, followed by T-2, T-3, T-7, T-4, T-6, and T-5 (Fig. 2a).”
And,
“The ABTS free radical scavenging activity varied among the treated samples, ranging from 360.45 ± 21.78 to 638.92 ± 7.38 µg GAE/g of DM, compared to 455.85 ± 1.45 µg GAE/g of DM in the control group. Most treatment groups showed a significant (p < 0.05) increase in ABTS free radical scavenging activity relative to the control. The highest scavenging activity was observed in the T-1 group (300 watts for 3 min), with a value of 981.07 ± 4.52 µg AAE/g of DM, followed by T-2, T-4, T-3, T-6, T-7, T-5, and T-8 (Fig. 2b). In contrast, the T-9 group displayed a significant (p < 0.05) decrease in ABTS scavenging activity compared to the control. Overall, these findings suggest that microwave treatments enhance ABTS scavenging activity in DORB, though prolonged exposure at high microwave power can negatively impact the activity, as seen in the 800 watts for 5 min treatment (T-9). This aligns with previous research showing that roasting can enhance ABTS free radical scavenging activity in maize, soybeans, and rice bran18,57,58. However, longer microwave exposures at higher wattages, such as 900 watts for 2–5 min, have been reported to reduce the scavenging activity in quinoa grains59. This indicates that the effect of microwave treatment on the antioxidant activity varies based on the feed type and specific treatment parameters used.
The total antioxidant capacity (TAC) varied among the treated samples, ranging from 1888.38 ± 11.04 to 2250.54 ± 31.03 µg AAE/g of DM, while the control group had a TAC of 2011.69 ± 23.82 µg AAE/g of DM. Most treatment groups showed a significant (p < 0.05) increase in TAC compared to the control. The highest TAC was observed in treatment group T-4, with a value of 981.07 ± 4.52 µg AAE/g of DM, followed by T-6, T-1, T-7, T-2, T-9, and T-8 (Fig. 2c). Treatment group T-3 showed a slight increase (2046.49 ± 13.40 µg AAE/g of DM), although it was comparable to the control. Prolonged exposure or higher microwave power appeared to negatively affect TAC, as seen in the lowest values obtained in treatments of 300 watts for 9 min (T-3) and 800 watts for 5 min (T-9). These findings align with previous research, which highlights the importance of optimizing microwave parameters to maximize the release of bioactive compounds and antioxidant activity in different vegetables, fruits, and grains46,60,61,62.
The ferric reducing ability varied among the treated samples, ranging from 790.18 ± 9.23 to 1175.89 ± 21.27 µg AAE/g of DM, compared to 672.32 ± 12.14 µg AAE/g of DM in the control group. Significant (p < 0.05) upregulation was observed in treatment groups T-1, T-3, T-2, T-7, T-5, and T-4 (Fig. 2d). The highest increase in ferric reducing ability was seen in T-1 (300 watts for 3 min), with a value of 1175.89 ± 21.27 µg AAE/g of DM. Treatment groups T-8 and T-6 showed slight increases, while T-9 showed a non-significant (p < 0.05) decrease in FRAP compared to the control group. Similar increases in FRAP have been reported in rice bran treated with microwaves at 600 watts, 700 watts, 800 watts and 900 watts for 2.5 min63,64. However, in this study, the 800 watts for 5 min treatment (T-9) resulted in a reduction in FRAP, suggesting that prolonged exposure to higher microwave wattage should be avoided to preserve or enhance the ferric reducing ability.
The cupric reducing antioxidant capacity (CUPRAC) ranged from 1008.64 ± 77.19 to 2004.09 ± 94.91 µg AAE/g of DM across the treatment groups. In comparison, the control group had a CUPRAC of 1638.18 ± 41.27 µg AAE/g of DM. Most treatment groups showed a significant (p < 0.05) increase in CUPRAC, with the highest value observed in the 300 watts for 3 min treatment (T-1), at 1175.89 ± 21.27 µg AAE/g of DM, followed by T-2, T-3, T-6, T-7, T-4, T-5, and T-8 (Fig. 2e). However, treatment group T-9 showed a significant (p < 0.05) decrease in CUPRAC compared to the control. These findings are consistent with several other studies, which report that microwave processing increases CUPRAC in various fruits and grains65,66,67. However, as with the other antioxidant parameters, prolonged microwave heating at higher wattages, such as the 800 watts for 5 min treatment (T-9), led to reduced values, likely due to the degradation of phytochemicals with antioxidant properties.
The ferrous ion chelating activity varied across the treatment groups, ranging from 404.75 ± 5.85 to 656.85 ± 8.5 µg EDTA equivalent/g of DM. In comparison, the control group had the lowest chelating activity, at 488.57 ± 7.85 µg EDTA equivalent/g of DM. All treatment groups showed a significant (p < 0.05) increase in ferrous ion chelating activity compared to the control group. The highest activity was observed in the 300 watts for 3 min treatment (T-1), with a value of 981.07 ± 4.52 µg EDTA equivalent/g of DM, followed by T-7, T-5, T-3, T-4, T-2, T-9, T-8, and T-6 (Fig. 2f). These findings are consistent with previous research, where microwaving at 900 watts for 3.5 and 5 min has been shown to enhance metal chelating activity in quinoa grains59. A similar increase in metal chelating activity has been reported in barley microwaved at 900 watts for 2 min68. The microwave-induced release of bound phenolics and the formation of melanoids may have contributed to the increase in metal chelating activity68.
The ascorbic acid content in the treated DORB groups ranged from 742.5 ± 9.68 to 1423.75 ± 40.4 µg/g of DM, while the control group having an ascorbic acid content of 1423.75 ± 40.4 µg/g of DM. All treatment groups showed an increase in ascorbic acid content compared to the control. The highest value was observed in treatment group T-6 (1423.75 ± 40.4 µg/g of DM), followed by significant (p < 0.05) increases in T-7, T-4, T-1, T-5, T-2, T-3, and T-8 (Fig. 2g).”
now reads:
“The ABTS free radical scavenging activity varied among the treated samples, ranging from 821.42 ± 3.46 to 1450.43 ± 2.37 µg GAE/g of DM, compared to 873.04 ± 6.40 µg GAE/g of DM in the control group. Most treatment groups showed a significant (p < 0.05) increase in ABTS free radical scavenging activity relative to the control. The highest scavenging activity was observed in the T-1 group (300 watts for 3 min), with a value of 1450.43 ± 2.37 µg AAE/g of DM, followed by T-2, T-4, T-3, T-6, T-7, T-5, and T-8 (Fig. 2b). In contrast, the T-9 group displayed a significant (p < 0.05) decrease in ABTS scavenging activity compared to the control. Overall, these findings suggest that microwave treatments enhance ABTS scavenging activity in DORB, though prolonged exposure at high microwave power can negatively impact the activity, as seen in the 800 watts for 5 min treatment (T-9). This aligns with previous research showing that roasting can enhance ABTS free radical scavenging activity in maize, soybeans, and rice bran18,57,58. However, longer microwave exposures at higher wattages, such as 900 watts for 2–5 min, have been reported to reduce the scavenging activity in quinoa grains59. This indicates that the effect of microwave treatment on the antioxidant activity varies based on the feed type and specific treatment parameters used.
The total antioxidant capacity (TAC) varied among the treated samples, ranging from 6246.25 ± 81.46 to 9927.50 ± 179.34 µg AAE/g of DM, while the control group had a TAC of 6059.53 ± 102.01 µg AAE/g of DM. Most treatment groups showed a significant (p < 0.05) increase in TAC compared to the control. The highest TAC was observed in treatment group T-4, with a value of 9927.50 ± 179.34 µg AAE/g of DM, followed by T-6, T-1, T-5, T-7, T-2, T-9, and T-8 (Fig. 2c). Treatment group T-3 showed a slight increase (6246.25 ± 81.45 µg AAE/g of DM), although it was comparable to the control. Prolonged exposure or higher microwave power appeared to negatively affect TAC, as seen in the lowest values obtained in treatments of 300 watts for 9 min (T-3) and 800 watts for 5 min (T-9). These findings align with previous research, which highlights the importance of optimizing microwave parameters to maximize the release of bioactive compounds and antioxidant activity in different vegetables, fruits, and grains46,60,61,62.
The ferric reducing ability varied among the treated samples, ranging from 1420.45 ± 29.87 to 3684.29 ± 96.55 µg AAE/g of DM, compared to 1574.91 ± 15.08 µg AAE/g of DM in the control group. Significant (p < 0.05) upregulation was observed in treatment groups T-1, T-3, T-2, T-7, T-5, and T-4 (Fig. 2d). The highest increase in ferric reducing ability was seen in T-1 (300 watts for 3 min), with a value of 3684.29 ± 96.55 µg AAE/g of DM. Treatment groups T-8 and T-6 showed slight increases, while T-9 showed a non-significant (p < 0.05) decrease in FRAP compared to the control group. Similar increases in FRAP have been reported in rice bran treated with microwaves at 600 watts, 700 watts, 800 watts and 900 watts for 2.5 min63,64. However, in this study, the 800 watts for 5 min treatment (T-9) resulted in a reduction in FRAP, suggesting that prolonged exposure to higher microwave wattage should be avoided to preserve or enhance the ferric reducing ability.
The cupric reducing antioxidant capacity (CUPRAC) ranged from 2694.58 ± 35.12 to 8657.08 ± 65.46 µg AAE/g of DM across the treatment groups. In comparison, the control group had a CUPRAC of 2927.92 ± 102.54 µg AAE/g of DM. Most treatment groups showed a significant (p < 0.05) increase in CUPRAC, with the highest value observed in the 300 watts for 3 min treatment (T-1), at 8657.08 ± 65.46 µg AAE/g of DM, followed by T-2, T-3, T-6, T-7, T-4, T-5, and T-8 (Fig. 2e). However, treatment group T-9 showed a significant (p < 0.05) decrease in CUPRAC compared to the control. These findings are consistent with several other studies, which report that microwave processing increases CUPRAC in various fruits and grains65,66,67. However, as with the other antioxidant parameters, prolonged microwave heating at higher wattages, such as the 800 watts for 5 min treatment (T-9), led to reduced values, likely due to the degradation of phytochemicals with antioxidant properties.
The ferrous ion chelating activity varied across the treatment groups, ranging from 527.16 ± 2.80 to 709.41 ± 4.75 µg EDTA equivalent/g of DM. In comparison, the control group had the lowest chelating activity, at 319.31 ± 9.38 µg EDTA equivalent/g of DM. All treatment groups showed a significant (p < 0.05) increase in ferrous ion chelating activity compared to the control group. The highest activity was observed in the 300 watts for 3 min treatment (T-1), with a value of 709.41 ± 4.75 µg EDTA equivalent/g of DM, followed by T-7, T-5, T-3, T-4, T-2, T-9, T-8, and T-6 (Fig. 2f). These findings are consistent with previous research, where microwaving at 900 watts for 3.5 and 5 min has been shown to enhance metal chelating activity in quinoa grains59. A similar increase in metal chelating activity has been reported in barley microwaved at 900 watts for 2 min68. The microwave-induced release of bound phenolics and the formation of melanoids may have contributed to the increase in metal chelating activity68.
The ascorbic acid content in the treated DORB groups ranged from 911.25 ± 28.64 to 2373.75 ± 16.06 µg/g of DM, while the control group having an ascorbic acid content of 817.50 ± 21.65 µg/g of DM. All treatment groups showed an increase in ascorbic acid content compared to the control. The highest value was observed in treatment group T-6 (2373.75 ± 16.06 µg/g of DM), followed by significant (p < 0.05) increases in T-7, T-4, T-1, T-5, T-2, T-3, and T-8 (Fig. 2g).”
The original Article has been corrected.