Effects of Microwave Cooking Conditions on Bioactive Compounds Present in Broccoli Inflorescences

Abstract

Cooking as a domestic processing method has a great impact on food nutrients. Most Brassica (Brassicaceae, Cruciferae) vegetables are mainly consumed after being cooked, and cooking considerably affects their health-promoting compounds (specifically, glucosinolates, phenolic compunds, minerals, and vitamin C studied here). The microwave cooking process presents controversial results in the literature due to the different conditions that are employed (time, power, and added water). Therefore, the aim of this work was to study the influence of these conditions during microwave cooking on the human bioactive compounds of broccoli. The results show a general decrease in the levels of all the studied compounds except for mineral nutrients which were stable under all cooking conditions. Vitamin C showed the greatest losses mainly because of degradation and leaching, whereas losses for phenolic compounds and glucosinolates were mainly due to leaching into water. In general, the longest microwave cooking time and the higher volume of cooking water should be avoided to minimize losses of nutrients.

Effects of different cooking methods on health-promoting compounds of broccoli

“…Vallejo et al(2002) reported that cooking by microwave resulted in high losses of both aliphatic and indole/aromatic glucosinolates in broccoli. The high rate of water evaporation leaching the glucosinolates from the broccoli florets might explain those dramatic losses (López-Berenguer et al, 2007), which is consistent with our findings. On the contrary, Verkerk and Dekker (2004) reported an increase (about 78%) in total glucosinolate content in red cabbage after microwave cooking and it might be an result due to an increase on the chemical extractability.…”

“…The concentration of ascorbic acid (the predominant form of vitamin C) in broccoli generally was decreased after cooking (Serrano et al, 2006). Previous studies have shown that boiling and microwaving caused a great loss of vitamin C (López-Berenguer et al, 2007;Sikora et al, 2008;Vallejo et al, 2002). Our study also shows that boiling and stir-frying/boiling caused a dramatic loss Hudson et al(1985) and Vallejo et al (2002) reported that steaming caused less loss of vitamin C than boiling and microwaving, which is consistent with our study.…”

“…The microwave cooking process presents controversial results in the literature due to the different conditions that are employed such as time, power, and the volume of added water (López-Berenguer et al, 2007). Vallejo et al(2002) reported that cooking by microwave resulted in high losses of both aliphatic and indole/aromatic glucosinolates in broccoli.…”

“…Under our cooking conditions, more than 5 min of cooking with microwave set at 1000 W would prevent the intact myrosinase from hydrolyzing glucosinolates, because these are denaturalizing conditions for this enzyme. Loss for glucosinolates was probably due to leaching into water (López-Berenguer et al, 2007); therefore, it is necessary to avoid adding excess water during cooking. Song and Thornalley (2007) reported that the glucosinolate content of Brassica vegetables including broccoli cooked by the stir-frying for 3~5 min with cooking oil pre-heated to 200 °C was not significantly changed.…”

Environmental and Genetic Variation in Essential Mineral Nutrients and Nutritional Value Among Brassica Vegetables

“…In the present study, we focused on raw materials and their variation within crops. But there are other factors affecting the mineral concentration of these crops, such as cooking including the loss in cooking water (López-Berenguer et al, 2007). Therefore, these factors will also need to be considered to determine nutritional value based on mineral content.…”