Maria Carmen Tan, Richard Anthony Galian, Danielle Ashley Sobremonte and Marissa Noel

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THE INFLUENCE OF DOMESTIC COOKING TECHNIQUES AND STORAGE ON GLUCOSINOLATES, MYROSINASE ACTIVITY, AND ISOTHIOCYANATES FROM Raphanus sativus L. 

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Abstract 

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Raphanus sativus cv. are edible roots used as garnishing or in vegetable preparations that come from the botanical family Brassicaceae and are native to Southeast Asia. To investigate the content of beneficial glucosinolates, isothiocyanates, and the enzyme myrosinase, tubers of different cultivars were analyzed after subjecting to different culinary techniques such as boiling, steaming, juicing, and pickling. Furthermore, an examination on the fluctuations of the constituents upon specific storage durations was performed. Sinigrin (1) 1,2-dihydroxy-2-phenylethyl glucosinolate (2), 4-hydroxyglucobrassicin (3), glucoraphasatin (4), and 4-methoxyglucobrassicin (5) in red radishes (RR) and 1 and 4 in white radishes (WR) were probed by HPLC-UV and LC-ESI-MS. GC-FID and GC-MS were employed to ascertain the concentration of the aglucone derivative, 4, 4-methylthio-3-butenyl isothiocyanate (6). Myrosinase activity was monitored using an UV-Vis spectrophotometer. Constituents 1and 4 detected in WR increased progressively with boiling for up to 30 minutes. GLSs in steamed radishes were observed after 10 minutes, where levels of 4 in WR and 1 in RR rose sharply. GLS concentrations were enhanced in the juice than in the pulp for both WR and RR.  Gas chromatography exhibited 6 was present in the juices of the cultivars. Myrosinase - mediated hydrolysis in processed samples exhibited elevated levels of 6 correlating to the precursor 4. Compound 6 was found in pickled samples even after prolonged storage. The optimal cooking method for radish tubers was boiling up to 30 minutes and steaming for up to 10 minutes to achieve the highest levels of bioactive agents.

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