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Pulsed Electric Field as a Means to Elevate Activity and Expression of α-Amylase in Barley (Hordeum vulgare L.) Malting
- Zhang, Liang, Li, Chao-Qun, Jiang, Wei, Wu, Mangang, Rao, Sheng-Qi, Qian, Jian-Ya
- Food and bioprocess technology 2019 v.12 no.6 pp. 1010-1020
- Hordeum vulgare, RNA, alpha-amylase, barley, beers, calcium, calcium chloride, electric potential difference, enzyme activity, experimental design, genes, malting, malting barley, mashing, pulsed electric fields, regression analysis, response surface methodology, China
- 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.