54F-17 |
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D. Van Eylen, I. Indrawati, A. Van Loey, and M. HENDRICKX. Laboratory of Food Technology, Katholieke Universiteit Leuven, Dept. of Food and Microbial Technology, 22 Kasteelpark Arenberg, Heverlee, B-3001, Belgium Brassicaceae contain high concentrations of glucosinolates. After hydrolysis by myrosinase (EC 3.2.1.147) products are formed that have a possible health promoting effect. During conventional thermal processing myrosinase is inactivated and can not transform the glucosinolates into the beneficial products. High pressure in combination with elevated temperatures could be an alternative to thermal processing since vegetative micro organisms can be inactivated under conditions that only have a limited effect on some enzymes. The objective was to study the effect of high pressure on the stability and activity of myrosinase purified from mustard seeds (Sinapis alba). Mustard seed myrosinase was purified by anion-exchange chromatography. The stability of myrosinase was determined by treating the myrosinase at isobaric/isothermal conditions for a certain time and measuring the residual myrosinase activity afterwards. Myrosinase activity during isobaric/isothermal conditions was determined by measuring the amount of glucose formed after treatment of a solution of myrosinase and the substrate sinigrin. Our study showed that mustard seed myrosinase was thermolabile but very pressure stable since 80% of the initial myrosinase activity was retained after a treatment of 50 min at 750MPa and 50° C. The activity study showed that myrosinase was more active at pressures up to 300 MPa than at atmospheric pressure. The optimal temperature shifted from 60° C at atmospheric pressure to 40° C at elevated pressure. The highest enzyme activity was found at 200 MPa and 40° C. These results indicate that high pressure processing may be a valuable alternative for thermal processing, for instance to blanch the product, if one wants to retain the myrosinase activity for optimal beneficial effect of the glucosinolate breakdown products. Moreover, during a high pressure treatment up to 300 MPa myrosinase will not only retain its activity, it will be more active than at atmospheric pressure and so enhance the health promoting effect.
Session 54F, Nonthermal Processing: General I
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |