I was wondering what everyone thought on the impact of different cooking methods on antioxidant activity of certain vegetables. Ive always microwaved my broccoli for about a minute with the thought that it was one of the best ways to preapre food while preserving its flavinoids however a little of bit googling made me a little less certain. Two conflicting studies i found were:
link to abstractAbstract
Total flavonoid and individual hydroxycinnamoyl derivative (sinapic and caffeoyl-quinic acid derivative) contents were evaluated in the edible portions of freshly harvested broccoli (cv Marathon inflorescences) before and after cooking and in the cooking water. High-pressure boiling, low-pressure boiling (conventional), steaming and microwaving were the four domestic cooking processes used in this work. The predominant sinapic acid derivatives were identified as 1,2,2-trisinapoylgentiobiose and 1,2-disinapoyl-2-feruloylgentiobiose. In addition 1,2-diferuloylgentiobiose and 1-sinapoyl-2,2-diferuloylgentiobiose were also identified in broccoli inflorescences. The results showed large differences among the four treatments in their influence on flavonoid and hydroxycinnamoyl derivative contents in broccoli. Clear disadvantages were detected when broccoli was microwaved, namely high losses of flavonoids (97%), sinapic acid derivatives (74%) and caffeoyl-quinic acid derivatives (87%). Conventional boiling led to a significant loss of flavonoids (66%) from fresh raw broccoli, while high-pressure boiling caused considerable leaching (47%) of caffeoyl-quinic acid derivatives into the cooking water. On the other hand, steaming had minimal effects, in terms of loss, on both flavonoid and hydroxycinnamoyl derivative contents. Therefore we can conclude that a greater quantity of phenolic compounds will be provided by consumption of steamed broccoli as compared with broccoli prepared by other cooking processes. Copyright © 2003 Society of Chemical Industry
and
link to abstractAbstract
Epidemiological studies have shown that consumption of Brassica vegetables decrease the risk of cancer. These associations are linked to dietary intake of glucosinolates and their metabolism to cancer preventive isothiocyanates. Bioavailability of glucosinolates and related isothiocyanates are influenced by storage and culinary processing of Brassica vegetables. In this work, the content of the 7 major glucosinolates in broccoli, Brussels sprouts, cauliflower and green cabbage and their stability under different storage and cooking conditions is examined. Glucosinolates and isothiocyanates were quantified by liquid chromatography with tandem mass spectrometric detection (LC–MS/MS). Isothiocyanates were detected with high sensitivity as the corresponding thiourea derivatives. Storage at ambient temperature and in a domestic refrigerator showed no significant difference and a minor loss (9–26%) of glucosinolate levels over 7 days. Vegetables shredded finely showed a marked decline of glucosinolate level with post-shredding dwell time – up to 75% over 6 h. Glucosinolate losses were detected partly as isothiocyanates. Cooking by steaming, microwaving and stir-fry did not produce significant loss of glucosinolates whereas boiling showed significant losses by leaching into cooking water. Most of the loss of the glucosinolates (90%) was detected in the cooking water. Increased bioavailability of dietary isothiocyanates may be achieved by avoiding boiling of vegetables.
It seems while microwaving may preserve some compounds while degrading others, steaming may be the best choice? What are your thoughts?
As a side note, I read on the linus pauling institute website that broccoli sprouts contain the same amount of sulforaphane compounds as when they a fully grown. Meaning they are a concentrated source of sulforaphane!
