Influence of storage and processing on Broccoli (Brassica oleracea L. var Italica) Glucosinolates

• Main Author: Salmasan, Regina M.
• Format: text
• Language: English
• Published: Animo Repository 2010
• Subjects: Glucosinolates; Broccoli; Broccoli industry; Chemistry
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/3864; https://animorepository.dlsu.edu.ph/context/etd_masteral/article/10702/viewcontent/CDTG004733_P.pdf
• Institution: De La Salle University

The effects of a range of storage and processing conditions on the glucosinolate content of broccoli (Brassica oleraceae L. var. italica) were investigated. Raw and blanched plant samples were frozen and stored for a 15 day trial period. Plant samples were also subjected to boiling, steaming, microwave treatment and stir frying in order to investigate the effects of common culinary processes on the glucosinolate concentration. The myrosinase activity, the presence of preformed hydrolysis products as well as the amount of hydrolysis products were also determined. Major glucosinolate content was analyzed by high performance liquid chromatography while hydrolysis products were monitored by GC MS or GC FID. A UV spectrophotometric assay method was used in the determination of myrosinase activity. Glucoraphanin, glucobrassicin and neoglucobrassicin were the major glucosinolates in broccoli florets. Boiling and microwave treatment resulted to increased glucosinolate levels due to myrosinase inactivation and cellular disruption leading to higher chemical extractability of the compounds while steaming and quick stir-frying yielded lower amounts of intact glucosinolates. Blanching prior to storage decreased enzyme activity resulting in the retention of the glucosinolates in the tissues. In general, the changes in glucosinolate levels correlated with myrosinase activity. Thermal degradation may also have influenced the effects observed. Influence of Storage and Processing on Broccoli Glucosinolates vi Although preformed degradation products were not detected, hydrolysis of defatted samples with exogenous myrosinase resulted in the production of sulforaphane and other possible hydrolysis products. Stir-fried broccoli yielded significantly higher levels of sulforaphane compared with those obtained from florets which were processed differently. As hydrolysis of glucosinolates does not exclusively give isothiocyanates, the amounts of sulforaphane obtainable from broccoli tissues may not be directly deduced from the glucoraphanin content. In general, increased sulforaphane levels were observed in processed vegetables.