Influence of Cooking Methods on Glucosinolates and Isothiocyanates Content in Novel Cruciferous Foods

Abstract

Brassica vegetables are of great interest due to their antioxidant and anti-inflammatory activity, being responsible for the glucosinolates (GLS) and their hydroxylated derivatives, the isothiocyanates (ITC). Nevertheless, these compounds are quite unstable when these vegetables are cooked. In order to study this fact, the influence of several common domestic cooking practices on the degradation of GLS and ITC in two novel Brassica spp.: broccolini (Brassica oleracea var italica Group x alboglabra Group) and kale (Brassica oleracea var. sabellica L.) was determined. On one hand, results showed that both varieties were rich in health-promoter compounds, broccolini being a good source of glucoraphanin and sulforaphane (≈79 and 2.5 mg 100 g−1 fresh weight (F.W.), respectively), and kale rich in glucoiberin and iberin (≈12 and 0.8 mg 100 g−1 F.W., respectively). On the other hand, regarding cooking treatments, stir-frying and steaming were suitable techniques to preserve GLS and ITC (≥50% of the uncooked samples), while boiling was deleterious for the retention of these bioactive compounds (20–40% of the uncooked samples). Accordingly, the appropriate cooking method should be considered an important factor to preserve the health-promoting effects in these trending Brassica.

Functional Ingredients From Brassicaceae Species: Overview and Perspectives

“…Broccoli floret, the edible part, represents just 15% of the total vegetable, producing 85% (stems and leaves) of valuable by-products [83]. Other Brassica species by-products have been studied as sources of bioactive compounds, among them red radish or kale, among others [84].…”

Eat Your Broccoli: Oxidative Stress, NRF2, and Sulforaphane in Chronic Kidney Disease

“…Cooking broccoli changes the amount of SFN [ 91 , 92 ], as heat may destroy the enzyme myrosinase required for the conversion of the chemically inert glucoraphanin to the bioactive SFN [ 93 ]. Among the different cooking methods, stir frying and steaming retain more SFN than boiling [ 92 ], whereas microwaving can either increase or decrease SFN levels, depending on timing (shorter times can increase levels) and power setting [ 93 , 94 , 95 , 96 ]. Blanching and freezing broccoli to extend shelf life can also decrease the amount of SFN [ 97 , 98 ].…”

Effects of Cooking Methods on Sensory, Chemical, and Microbial Characteristics of Broccoli (Brassica Oleracea)

“…In general, most vegetables are commonly cooked before being consumed. Previous studies found that the cooking methods cause significant changes in the overall content of nutrients, chlorophylls, flavonoids, overall texture, and sensory characteristic in vegetables (Brewer et al, 1995;Vallejo et al, 2002;Lin & Chang, 2005;Cieslik et al, 2007;Sikora et al, 2008;Baenas et al, 2019;Danowska-Oziewicz et al, 2019;Wu et al, 2019). Specifically, cooking broccoli under oven with overheated steam or hot air with overheated steam decreased the contents of chlorophylls a and b (Danowska-Oziewicz et al, 2019).…”

“…Previous research (Baenas et al, 2019) reported that glucosinolates and isothiocyanates are unstable when vegetables are cooked. When heat is applied, the tissues in the plants are damaged and glucosinolates are converted to glucose, which makes the biology of the plant unstable which results in loss of nutrients (Wachtel-Galor et al, 2008;Verkerk et al, 2008;Baenas et al, 2019).…”