## 3 Results and Discussion
### Effect of Thermal Processing on Total Glucosinolates in Broccoli  
The total amount of glucosinolates was significantly higher in air-fried broccoli (3.76 \(\pm\) 2.09 mg SinE/g fw) than in all other samples (Figure 2). The lowest amount was detected in pan-fried broccoli (0.14 \(\pm\) 0.10 mg SinE/g fw), which contained about 28 times less glucosinolates than air-fried broccoli. However, the amount in pan-fried broccoli was not significantly different from the amount in boiled, blanched, and steamed broccoli. Total glucosinolates were not measured in water extracts due to their low water solubility. One of the reasons why air-fried broccoli had the highest amount of glucosinolates might be the fact that at high temperatures, their degradation increases in parallel with the amount of water [63]. The high standard deviations observed in the samples may be attributed to the broccoli heads being harvested in different seasons, potentially affecting the concentration of glucosinolates. This is because myrosinase activity is regulated in response to abiotic and biotic factors such as temperature, light intensity, photoperiod, and pathogens [64], and this might significantly affect the concentration of glucosinolates in the same developmental stage in different seasons. Similar studies were conducted on Brussel sprouts, white and green cauliflower, broccoli, and curly kale, which showed a significant loss of total glucosinolates after boiling and blanching, 72.4% and 30%, respectively [65]. A decrease in glucosinolates was also observed in rutabaga, green and purple cauliflower after cooking. It was observed that indole glucosinolates are more sensitive to cooking than other types of glucosinolates [66]. A similar decrease in glucosinolates due to cooking was also found in broccoli, Brussel sprouts, cabbage, and cauliflower and the authors claim that 80% of the loss was due to leaching into water, while 20% was due to high temperature [67]. However, in broccoli, Brussel sprouts, cauliflower, and green cabbage, the loss of total glucosinolates was significantly lower during steaming, microwaving, and stir-frying than during cooking [68]. Microwaving even showed a beneficial effect on the amount of total glucosinolates in red cabbage, with an increase of 78% compared to raw vegetables [69], as well as in Brussel sprouts, with an increase of 86% [70]. One of the theories is that the inactivation of enzymes such as myrosinase occurs during prolonged cooking, which could contribute to the stability of glucosinolates [67]. However, the degradation of glucosinolates depends not only on myrosinase, but on multiple other factors [71]. Nevertheless, indole glucosinolates have been shown to be more sensitive to boiling (51% loss) than aliphatic ones (38% loss) [72]. Finally, the loss of glucosinolates during different cooking methods could be due to the presence of certain plant components which could further influence the  
Figure 1: Effect of different thermal processing techniques on hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) level in broccoli extracts. Values represent average \(\pm\) standard deviation of three biological and four technical replicates. Different letters indicate a significant difference among the values (one-way ANOVA, Duncan’s test, \(p\leq\) 0.05). fw = fresh weight; BO = broccoli boiled; BOW = water after boiling broccoli; BL = broccoli blanched; BLW = water after blanching broccoli; ST = broccoli steamed; STW = water after steaming broccoli; AF = broccoli air-fried; PF = broccoli blanched and then pan-fried.  
stability of glucosinolates depending on the cooking method, temperature, and cooking time [66].