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Title: Enhancing sulforaphane formation and biovailabilty in some cooked Brassica vegetables
Author: Adediran, Okunade Olukayode
ISNI:       0000 0004 7227 4094
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2016
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The glucosinolate-myrosinase system has been the subject of sustained focus and has been extensively reviewed over time. The system is characteristic of Brassicaceae. Diets rich in Brassica vegetables have been associated with a reduced risk of cancer, attributed to isothiocyanates, the degradation products of glucosinolates. Glucosinolates are water soluble sulfur rich compounds, which upon hydrolysis by endogenous myrosinase yields a variety of compounds with impact on human health and sensory attributes of these vegetables. However, the delivery of health beneficial hydrolysis products is hampered when Brassicaceae are thermally processed. This thesis was aimed at improving the formation of sulforaphane, and its bioavailability when brown mustard is added to cooked broccoli. Thermal and pressure inactivation of myrosinase enzymes extracted from black, brown and yellow mustard seeds was investigated to ascertain the stability of mustard myrosinase under processing conditions. Brown mustard had higher myrosinase activity than black and yellow mustard and the extent of enzyme inactivation increased with pressure and temperature for all the mustard seeds. However, at combinations of pressures {200-400 MPa) and high temperatures (60-80 °C), there was less inactivation. Application of 300 MPa and 70 °C for 10 minutes retained 20%, 80% and 65% activity in yellow, black and brown mustard, respectively, whereas the corresponding activity retentions when applying only heat (70 °C, 10 min) were 0%, 59% and 35%. Thus, application of moderate pressures (200-400 MPa) can potentially be used to retain myrosinase activity needed for subsequent glucosinolate hydrolysis. The impact of geographical origin on myrosinase activity and thermal inactivation in black, brown and yellow mustard seeds was studied. Mustard seeds from different geographical locations were grown under identical controlled conditions. There were significant increases in enzyme activity and protein content after cultivation. Myrosinase inactivation increased on heating the cultivated seeds. Myrosinase was stable below 60 °C in all the seeds. However, at 70 °C, activity loss was approximately 10% and over 70% loss at 90 °C. At 100 °C, only two brown seeds (China, Korea) and one yellow seed sample (France) had marginal myrosinase activity. This Implied that varietal differences in mustard myrosinase activity and thermal stability persisted after cultivation under identical controlled conditions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available