Pulsed Electric Field Enhances The Activity Of Beer Malt Amylase

Malt is the major used for beer brewing and its quality plays an important role on the production,quality and cost in beer industry.Some characteristics of domestic barley cultivars is inferior to imported barley,such as enzyme activity,solubility and filtration properties.The quality of domestic made barley malt is eager to improve.Pulse electric field?PEF?and Ca²⁺treatments are the effective means to regulate physiological changes in plants and promote their growth and development.In this paper,we choose the barley malt extensively demanded in the beer industry as the research object.PEF and PEF combined with Ca²⁺ were used in the process of barley malt preparation,in order to understand its effects on barley germination index and malt physicochemical properties.The growth effects of malt amylase activity were taken as the investigation index to optimize the conditions of malting.The mechanism of its action is preliminarily studied.The main results are as follows:?1?PEF treatment was beneficial to improve the germination activity of barley.The germinating barley was treated with the pulsed electric field at the voltages of 3 kV,6 kV,9 kV,12 kV and 15 kV.There are significant differences?P<0.05?between the treated barley and the control group in the eight macroscopic indexes and the six microscopic indexes,especially in the germination energy?38.96%?,the root length?43.33%?,p-glucanase activity?21.46%?,a-amylase activity?26.48%?,and ?-amylase activity?23.57%?.The results of the principal component analysis of 14 indexes showed that when the voltage was 9 kV and 12 kV,the pulse electric field had the best effect on the germination of barley.?2?PEF treatment was beneficial to improve the activity of a-amylase.The growth rate of malt ?-amylase was significantly affected?P<0.05?by pulsed voltage,material residence time,pulse frequency and pulse width.The regression equation obtained by the response of surface optimization design had a high degree of correlation?R2=0.9859?.The optimum conditions were as follows:voltage 8 kV,material residence time 14 min,pulse frequency 500 Hz,pulse width 8?s;under this condition,the activity of a-amylase and the saccharifying power increased by 29.26%and 10.54%in comparison with the untreated group.?3?The amylase activity was activated more effectively by PEF+Ca²⁺ than PEF treatment and Ca²⁺ treatment alone.Ca²⁺ treatment was divided into two kinds,Ca²⁺ culture medium and Ca²⁺ seed soaking.The parameters for improving the ?-amylase activity under the combination treatment of PEF and Ca²⁺ culture medium was as follows:Ca²⁺ concentration 60 mg/L,voltage 8 kV,material residence time 14 min,pulse frequency 500 Hz,pulse width 8 ?s;under this condition,the activity of a-amylase and the saccharifying power increased by 44.17%and 20.65%in comparison with the untreated group.The optimum conditions for improving the malt?-amylase activity under the combination treatment of PEF and Ca²⁺ soaking was as follows:Ca²⁺ concentration 80 mg/L,voltage 10 kV,material residence time 12 min,pulse frequency 500 Hz,pulse width 7 ?s;under this condition,the activity of a-amylase and the saccharifying power increased by 54.02%and 12.65%in comparison with the untreated group.The optimum conditions for improving the malt ?-amylase activity under the combination treatment of PEF and Ca²⁺ seek soaking were as follows:Ca²⁺ concentration 80 mg/L,voltage 10 kV,material residence time 14 min,pulse frequency 600 Hz,pulse width 8 ?s;under this condition,the activity of ?-amylase and the saccharifying power increased by 34.82%and 28.44%in comparison with the untreated group.?4?PEF and Ca²⁺ induced the expression of barley Amy6-4 gene.After the treatment of PEF combined with Ca²⁺,the RNA yield of malt root and sprout increased by 51.59%and 42.71%,and the expression of Amy6-4 gene encoding a-amylase was greatly improved.The expression of Amy6-4 genes in sprout tissue was significantly improved by applying PEF?voltage 8 kV,pulse frequency 500 Hz,pulse width 8 ?s,material residence time 14 min?.