Novozymes innovation session Why a brewer must think about arabinoxylans?

Transcription

1 Novozymes innovation session Why a brewer must think about arabinoxylans? IBD 2018, Wellington

2 What is Arabinoxylan (AX)? In cereals, arabinoxylans are a major of the non starch polysaccharides (NSP). The basic structure of an AX is a linear backbone of (1 4)-linked -D-xylopyranosyl residues to which -L-arabinofuranosyl substituents are attached Ferulic acid is esterified to some arabinofuranosyl substituents Structure of arabinoxylan

3 Why Arabinoxylan is so important in brewing? Pericarp + Testa ~60% AX, 5% BG, 25% CE milling, mashing Endosperm Aleurone ~20% AX, ~70% BG, ~3% CE ~70% AX, ~26% BG, ~2% CE Spent grain micrograph (NZ Brewing) Insoluble particles = stabilizing filter-bed elements: o Husks (fragments), fragments of pericarp and testa with partly attached fragments of the aleurone. fragments of embryo fragments of endosperm (insufficient malting + milling + mashing) o Stabilizing elements high in arabinoxylan hydrolysis filter bed collapse Permeability = f (ε, di, L) = f (enzyme activity)

4 Arabinoxylan content is 5-10 times higher in commercial beer compared to beta-glucan Arabinoxylans are very hydroscopic like beta glucans AX can create high wort viscosity, reducing mash filtration speed dramatically They stick to other grain components and to filter aids and filter membranes resulting a rapid pressure build-up and faster chocking of filter. Arabinoxylans are not broken down to the same degree as beta-glucans, so viscous polysaccharides from xylans still remain in wort and beer. Malt derived β-glucanases and xylanases are not very heat stable. They are inactivated at temperatures above 50 C

5 Arabinoxylan impact on membrane clogging (from literature) SEM-micrographs illustrate quite clearly that i.e. the high molecular weight arabinoxylan (963 kda) cause a severe clogging of the membrane with consequently reducing the free filtration area NGF shifts the size distribution towards smaller polymers i.e. the fraction >805 kda is half of that obtained with Ultraflo Max Increasing the dosage of Ultraflo Max does not significantly change the fraction >805 kda but instead cause a shift in the fraction of kda towards small polymers The arabinoxylan size distribution analysis in combination with x-flow-membrane pilot trials supports strongly the hypothesis that arabinoxylans are a key parameter determining beer filtration

6 Not only β-glucan is the trouble the role of arabinoxylan Significant reduction in viscosity when endo-xylanase is applied on top of beta-glucanases Improves accessibility for beta-glucanases to beta-glucan Further hydrolysis of arabinoxylan enabled by specific arabinofuranosidase reduces wort viscosity close to minimum possible viscosity

7 But be careful - wrong choice of xylanase Wrong xylanase can de-stabilize the husk filter bed and hamper the wort separation process Sweet wort [g] Filter-beds after sweet wort filtration Time [min] Stability not impacted by xylanase activity Flow diagram-filtration Permeability = f (ε, di, L) = f (enzyme activity) De-stabilized by xylanase activity

8 Xylanase degradation products Increasing substitution of xylan backbone Increasing size of endo-xylanase hydrolysis products smaller hydrolysis products of endo-xylanases activity by GH10 reduced wort viscosity Table from: Pollet, A., Delcour, J. A., Courtin, C. M. (2010), Structural determinants of the substrate specificities of xylanases from different glycoside hydrolase families. Crit Rev Biotechnol., 30(3), Info about WAX from: Jee-Yup Han (2000), Structural characteristics of arabinoxylan in barley, malt, and beer. Food Chemistry, 70 (2),

9 Demand to enzyme solution Note: Fk-value = a performance indicator for mash filtration derived from Darcy-equation. Low Fk-value: good filtration High Fk-value: poor filtration Hydrolyse water-extractable hemicellulose ηwort = -Δ Minimise solubilisation of water-unextractable hemicellulose B = constant

10 Selecting the right candidate Permeability = f (ε, di, L) = f (enzyme activity)

11 Ultraflo Max Get the best beer filtration Ultraflo Max offers the best viscosity reduction compared to other solutions in the market. Traditionally, the levels of beta-glucans have defined the quality of filtration, but Ultraflo Max lowers arabinoxylan values in addition to decreasing beta-glucans changing the benchmark for beer filtration

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