Pulsed Electric Field as a Means to Elevate Activity and Expression of α-Amylase in Barley (Hordeum vulgare L.) Malting.

Poor quality of barley hinders badly the beer production in China. α-Amylase activity plays a very important role in malted barley (Hordeum vulgare L.) for beer production during the mashing process. Pulsed electric field (PEF) and Ca2+ in the form of CaCl2 were introduced to elevate α-amylase activity of barley malt for modifying the quality, and positive consequences emerged. The influences of PEF operating parameters on α-amylase activity were investigated, and the parameter settings were optimized based on factorial experiments, and a highly (R2 = 0.9859) correlated regression model was established using response surface methodology. An increment of about 29% for α-amylase activity was achieved at the optimal parameter settings as 8 kV of pulse voltage, 500 Hz of pulse frequency, 8 μs of pulse width, and 14 min of material residence time. The incorporation of PEF with Ca2+ demonstrated much better functions than the utilization of PEF or Ca2+ alone. The orthogonal experiment design was adopted to optimize the conditions for incorporation of PEF with Ca2+, and it showed that at 8 kV of pulse voltage, 500 Hz of pulse frequency, 7 μs of pulse width, 12 min of material residence time, and 80 mg L−1 of Ca2+ concentration, the largest increment of over 54% for α-amylase activity was obtained. Evaluations of PEF and Ca2+ on Amy6-4, the gene responsible for α-amylase in barley seed, were made to look into the mechanism how they functioned in barley malting, and it was found that the elevation of α-amylase activity was because of the significant (P < 0.05) increase of the amounts of total RNA and Amy6-4 expression. [ABSTRACT FROM AUTHOR]