Myrosinase stability in broccoli (Brassica oleracea var. italica). Influence of temperature and water activity
2010
Castelo-Branco, João Diogo Cristovão Pinto | Martins, Margarida Moldão
Mestrado em Engenharia Alimentar - Instituto Superior de Agronomia
Show more [+] Less [-]Epidemiological studies have shown that a diet rich in Brassica vegetables is associated with a decreasing risk of incidence of some types of cancer. These health promoting effects are most likely due to the breakdown products of glucosinolates formed by the action of myrosinase which catalyzes the hydrolysis of glucosinolates, found in Brassica plants. Industrial processing of food can affect the content, composition, activity and bioavailability of glucosinolates breakdown products, due to cell lysis or glucosinolates and myrosinase degradation. The aim of this thesis is to investigate the combined effect of moisture content (water activity) and temperature on myrosinase stability. The study was conducted in batches of freeze dried broccoli with different moisture contents. These batches of broccoli were then heated at different time/temperature combinations and myrosinase activity was analysed, the obtained results from these measurements were kinetically modeled. Myrosinase was shown to be much less thermo stable in higher moisture content samples than in the driest samples. Thermal stability (30-80 ºC) of myrosinase was described by a first order kinetic model. Besides showing higher myrosinase thermal stability, driest samples show lower activation energies, i.e, lower increase of degradation rate when temperature increases.
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