Inactivating effect of pulsed electric field on lipase in brown rice.

Abstract: Pulsed electric field (PEF) treatment was applied to brown rice grains in a treatment chamber which was surrounded by organic glass as walls around a pair of horizontally paralleled plate electrodes to investigate the feasibility of PEF on low moisture food materials. Based on a monolayer of brown rice grains the results showed that the lipase activity could be significantly inactivated by PEF. Among the PEF parameters, the voltage was the most important to the inactivating efficiency, followed by frequency and pulse width; while the time was less dominant. The interactions between voltage and pulse width and between frequency and pulse width also contributed to the lipase inactivation significantly. By using Box–Behnken design, response surface methodology was applied to optimize the process and a well fitting model was obtained with PEF parameters, voltage, frequency, pulse width, and residence time. Industrial relevance: Pulsed electric field (PEF) is a low temperature and environment friendly technology in food processing. It is promising and has received considerable attention over the years in the past. PEF has been applied to inactivate microorganisms or enzymes. However, research work regarding PEF focused almost only on liquid food processing so far. There has been no report of PEF on solid food materials. Rice bran is abundant and nutritious, but it could not be stored for a long time because enzymolysis takes place soon after it is scraped off from rice grains. If the PEF could be used for lipase inactivation in brown rice grains, the stabilized rice bran should be obtained after milling during the material convey. It would be another effective and in-line rice bran stabilization technique potential in the rice industry. Furthermore, the application scope of PEF in food industry could be widened. [Copyright &y& Elsevier]