The Blocking Factors Of High-Corn-Starch-Ratio Wort Filtration And Improvement Of The Lautering Process

In recent years, beer brewing technoloty is characterised by high-gravity brewing technology, high-adjunct-ratio brewing technology, high-gravity liquefing technology in China. In order to save the cost and reduce energy consumption, corn starch is widely used as the adjunct and high-gravity liquefing technology is often applied. However, the application of increasing ratio of corn starch will cause mash filtration blocking problem, which extend wort filtration time and spent grain sparging time, reduce the production efficiency. In contrast, high proportion of rice adjunct does not cause filtration blocking problem. To study the factors causing blocking and solve the problem, liquefied corn starch, high-adjunct-wort filtration and the blocking factors were analyzed, a combinational application of enzyme preparations was also optimised.During corn starch liquefaction, some special yellow substances were found to float on the surface of liquefied corn starch, and they are intuitively considered as the factor causing wort filtration blocking. To determnine if it is yellow substance that blocks filtration, components, cause of formation and its effect on filtration were studied. The results show that yellow substance is a kind of aggragate mixed with saccharides(70±5%) mostly and small amount of protein(5±1%) and lipid(13±1%), its density is lower than water. The factors that affects the formation of yellow substance are water ratio, liquefaction time and boiling. The mechanism how it forms maybe that: when water content decreaes, liquefaction time is extended or boiling, water evaporate excessively, so the liquefied corn starch become denser, some dextrin interact with part of protein and lipid, forming the aggragate with low density, floating on the surface of liquefied corn starch. It is proved that yellow substance is not the factor that blocks filtration.To further analyze the factors causing filtration blocking, permeability of spent grain layer was dicussed. In this study, a visual filter device was designed. By using the device, the formation process of spent grain layer and wort filtration process can be observed. The result show that it is incompletely degraded corn starch particles that block filtration. These corn starch partiles remain in spent grain and on the surface of spent grain layer, forming dense, viscous and layered spent grain layer, greatly weaken the permeability of spent grain filter layer. To analyze the reason why corn starch cannot be completely degraded, three aspects including water ratio, resistant starch and amylopectin content were discussed. The result show that water ratio is the main influencing factor, when material-to-water ratio increase from 1:2.5 to 1:7, residual corn starch decreases by 80%, from 15.5% to under 3%. Resistant starch and molecule structure are not the main factors.To improve filtration rate, enzyme preparations are used in breweries. In this study, to improve wort filtration blocking problem during high-corn-starch-ratio brewing process, enzymatic solution was optimized and an optimal combinational enzyme preparations was obtained through orthoganal test: thermostable α-amylase 0.3 mg·g-1, β-glucanase 0.1 mg·g-1, xylanase 0.2 mg·g-1, barley β-amylase 0.6 mg·g-1. By using the optimal enzymes, wort filtration rate is improved by 20.1% than before. By boiling in liquefaction, wort filtration rate is improved by 21.2% than before. Moreover, in order to improve filtration efficiency, more than 1:5 of the material-to-water ratio and under 30% of corn starch proportion are suggested.