Abstract
The impact of conventional cooking and processing methods on total phenols, antioxidant activity, carotenoids and glucosinolates of watercress was evaluated. Boiling significantly decreases phenolic content, antioxidant activity and recoverable glucosinolates, however it increases the carotenoid concentrations of watercress as compared to the raw vegetable. Cooking by microwaving and steaming maintains the majority of phytochemicals in comparison to the fresh material, suggesting that they should be used as the preferred methods of watercress preparation. Boiling of watercress should be avoided to ensure maximum ingestion of watercress-derived beneficial phytochemicals.
Introduction
Watercress (Nasturtium officinale) belongs to the family of Brassicaceae together with broccoli, cabbage, mustard and Brussels sprouts. Epidemiological studies associate a higher intake of Brassica vegetables, such as watercress, with a reduced risk of various types of cancers (Verhoeven, Goldbohm, vanPoppel, Verhagen, & vandenBrandt, 1996). Watercress is an exceptional source of natural, bioactive compounds for which research has highlighted a favourable role in anti-genotoxic and anti-cancer processes both in vivo and in vitro (Boyd et al., 2006, Gill et al., 2007, Rose et al., 2000). The health benefits of watercress have been attributed to phytochemicals including glucosinolates, carotenoids and flavonoid compounds.
Watercress, and essentially all members of the Brassicaceae family, have been identified as a rich source of glucosinolates (Bell & Wagstaff, 2014). Glucosinolates are hydrolysed to isothiocyanates by the action of the enzyme myrosinase (β-thioglucoside glucohydrolase; EC 3.2.3.1), upon cell tissue damage such as mastication, chopping or cooking. This group of plant bioactive compounds is responsible for the characteristic pungent taste that Brassica vegetables possess. Gluconasturtiin (2-phelylethyl glucosinolate) is the most prominent glucosinolate in watercress (Boyd et al., 2006, Gill et al., 2007) with a range of aliphatic and indole glucosinolates adding to its glucosinolate profile.
what are the findings,gaps future research and where does research take place
Findings from this study suggest that conventional boiling significantly decreases the phenolic content, antioxidant activity, and recoverable glucosinolates of watercress, while increasing carotenoid concentrations compared to raw watercress. In contrast, cooking by microwaving and steaming maintain the majority of phytochemicals in comparison to the fresh material. This highlights the importance of choosing appropriate cooking methods to ensure maximum ingestion of watercress-derived beneficial phytochemicals.
One gap in the research is the lack of information on the specific mechanisms by which different cooking methods affect the phytochemical content of watercress. Further studies could explore the impact of cooking on the stability and bioavailability of specific phytochemicals in watercress.
Future research could also investigate the effects of various cooking methods on the sensory attributes and overall acceptability of watercress, as well as the potential health benefits of consuming watercress prepared using different cooking methods.
Research in this area could take place in laboratories, agricultural research centers, and nutrition institutes where the impact of cooking on the phytochemical content of watercress can be tested and analyzed. Additionally, clinical studies could be conducted to assess the bioavailability and potential health benefits of consuming watercress prepared using different cooking methods.