Exogenous phytase improved the activity of hydrolases to decrease the malting time.Treatment with phytase during barley steeping increased activity of hydrolases (α-/β-amylase, proteinase, β-glucanase and xylanase) in green malt. Maximal activity was observed for α-/β-amylase, β-glucanase and xylanase with 0.8 U phytase/g and proteinase with 1.2 U phytase/g. Phytase promoted acrospire growth of green malt and reduced malting process with 0.8 U phytase/g in 96 h, which is 24 h less than the control. No significant variation of malt quality was found between control malt and malt treated with 0.8 U/g or 1.2 U phytase/g (P > 0.05), which makes application of exogenous phytase during steeping process as a good option for reducing malting time.Adding phytase during steeping process increases the activity of hydrolases, which reduces malting time without impacting on malt quality.

•Purify AXAH-I from Chinese Dan’er malt.•Determine the enzymatic characteristics of AXAH-I.•Positive effects of extra AXAH-I on filterability of Dan’er malt.•A proposal of new enzyme product for malt filterability improvement.Dan’er is a widely grown malt barley cultivar in China, but its filterability defects have severely impeded its application in beer brewing. Previous investigations have suggested that we should identify the malt filterability correlated proteins, one of which was postulated to be arabinoxylan arabinofuranohydrolase I (AXAH-I). To verify this hypothesis, we purified AXAH-I from Dan’er malt, characterised its enzyme performance, and investigated its influence on filterability by adding different amounts of purified enzyme to the mash. With 6 mU g−1 malt AXAH-I supplemented, the wort separation rate increased by 31.8%, viscosity decreased by 3.6%, and the endosperm reserve contents declined concomitantly. Unexpectedly, the wort turbidity increased with increasing AXAH-I. We also tried to optimise the use of currently available commercial enzyme products for filterability improvement in beer brewing, by supplementing them with purified AXAH-I and β-amylase. AXAH-I could be a functional component for novel commercial enzyme products in the beer industry.

•A comparative proteomic study of green malts from two barley cultivars was performed.•Differentiating proteins were detected by fluorescent difference gel electrophoresis.•These proteins were identified by tandem MS and related to malt quality differences.•One third of these cultivar-differential proteins were not found in malts.The variety of metabolic proteins theoretically reaches a peak at the end of germination in large-scale malting. In the present study, comparative proteomics based on two-dimensional fluorescent difference gel electrophoresis (2D-DIGE) was employed to quantitatively analyse the low-salt soluble proteins in green malts from cultivars of Dan’er and Metcalfe. Fifty-nine metabolic proteins with significant differences between cultivars were successfully identified using MALDI-TOF/TOF. The roles of differential proteins in malt quality discrimination were elucidated according to their functions. Among them, 18 proteins exhibited differences in the green malts but not in the malts between the two cultivars. They could be considered as supplementary contributors to the quality defects of Dan’er malt, and new markers for malt quality improvement.

The malting process is the controlled germination, followed by drying, of the barley grain. For brewing beer, the malting process is modified according to the features of the barley variety being malted. In China, there are two schedules routinely used for malting the widely grown Dan’er cultivar, processes I and II. The quality of malt produced with process II is considered to be superior to that from process I for Dan’er by maltsters and brewers. In the present study, comparative proteomic analysis was performed between Dan’er malts produced by malting processes I and II. The data showed that enzymes and proteins responsible for cell wall polysaccharide degradation and starch and protein hydrolysis were more abundant in malt produced by process II, leading to improved quality, especially for the commercially important filterability, saccharification time, and diastatic power (DP) quality traits. In addition, to verify the proteomic results, the activities of several key enzymes (α-amylase, β-amylase, and limit dextrinase) were compared between the two malts. This enabled the influence of malting process on malt quality to be determined and suggested malting process schedule changes to optimize the malting process for the Dan’er cultivar, especially for improving filterability, which is often deemed as suboptimal by maltsters and brewers.

Barley protein Z7 (BSZ7) is a well-known serine protease inhibitor that was regarded as a major effector of beer foam stability. Moreover, it has also been suggested to participate in haze formation and affect wort filterability. The present study purified BSZ7 from barley malt and characterized its secondary structure and modification, as well as its relationship with peroxidase, to elucidate the molecular base of BSZ7 that supports its multiple roles in malt and beer. It was found that after 30 min of heating, the secondary structure was not affected. BSZ7 has no inhibiting effect on nonspecific protease originated from malt, suggesting its negative role in wort filterability was accomplished by other means. Furthermore, the glycation of BSZ7 by the Maillard reaction may make some contribution to its survival during wort boiling. The interaction of BSZ7 with polysaccharides and polyphenols found by adding experiment may explain how it acts as a negative factor on wort filterability. Greater understanding of BSZ7 and other proteins of malts will lead to better improvements in brewing quality.

•Barley malts with filterability gaps were investigated by comparative proteomics.•Fifty-one differential protein spots were detected by 2D-DIGE.•Hydrolases and pathogen-related proteins were mainly identified by MALDI-TOF–TOF.•Differential proteins putatively responsible for filterability were proposed.•Effects of two most distinctly differential proteins on filterability were verified.Filterability is an essential quality parameter of barley malt and significantly impacts productive efficiency and quality of beer. In the study, differences of metabolic capability, rather than of initial contents of macromolecules in barleys, were found to be the main reason for malt filterability gap between the widely used cultivars Dan'er and Metcalfe in China. Comparative proteomics based on fluorescent difference gel electrophoresis (DIGE) was employed to quantitatively analyze proteins of four commercial malts belonging to the two cultivars, and 51 cultivar-differential spots were identified to 40 metabolic proteins by MALDI-TOF/TOF mass spectrometry, mainly including hydrolases and pathogen-related proteins. According to their function analysis and abundance comparison between cultivars, filterability-beneficial and -adverse proteins were putatively proposed. Two most remarkable differential proteins, β-amylase and serpin Z7, were further investigated to verify their effects on Dan'er malt filterability. These results provide biological markers for barley breeders and maltsters to improve malt filterability.Biological significanceTo the best of our knowledge, this is the first report of comprehensive investigation of metabolic proteins related to wort filterability of barley malts, and sheds light on clues for filterability improvement. Visible differences in the expression level of metabolic proteins between Dan'er and Metcalfe malts using 2D-DIGE signify a valuable tool for cultivar comparison, illustration of key proteins responsible for filterability and even other qualities of barley malts. And with these explorations on biomarkers of malt filterability and other aspects, there will be higher efficiency and quality of beer brewing, less application of exogenous hydrolases and more expending market for Chinese malting barleys. This article is part of a Special Issue entitled: Translational Plant Proteomics.

Barley malt is essential for beer production. In the present study, the nonprolamin fractions including proteins with structural functions or metabolic activities were extracted from barley malts of the widely used cultivars Gangpi and Baudin in China. The metabolic proteomes (pI 4–7) were constructed and compared using two-dimensional electrophoresis (2DE) followed by matrix-assisted laser desorption/ionization-tandem time-of-flight mass spectrometry (MALDI-TOF/TOF) identification. There were 333 and 354 spots detected in the 2DE gels of Gangpi and Baudin malts, respectively, and about 90% of these spots were shared by the two malts. For all, 377 were successfully identified to 192 proteins, most of which were enzymes and enzyme inhibitors, suggesting important roles in barley malting and the mashing stage of brewing. The Baudin malt was found to contain more spots representing amylases, pathogen-related proteins, and chaperones than the Gangpi malt. In addition, enzymes involved in glycolysis and redox pathways showed significantly different profiles between the two malts, permitting a more in-depth elucidation of the relationship between differential proteins and malt qualities.

To reveal the characteristics and formation mechanism of proteins in the secondary precipitate of soy sauce (SPSS), proteins in the supernatant of soy sauce were used as control, and SPSS was prepared by centrifugation in combination with lyophilization. The proteins in SPSS were isolated and identified by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization-time of flight/time of flight mass spectrometry. Acidic polypeptide A1a of soy glycinin G1 (32–35 kDa) and basic polypeptide B3 of soy glycinin G4 (23 kDa) were verified as the predominant proteins (95.2 %) in SPSS. The amino acid composition, average hydrophobicity (HΦavg), and the secondary structure of the proteins in SPSS were investigated by high-performance liquid chromatography and Fourier transform infrared spectroscopy. Results revealed that SPSS contained not only proteins but also free amino acids; the significantly higher average hydrophobicity and much lower contents of β-sheet and random coil were the main characteristics and reasons for the formation of proteins in SPSS.

The starter culture “wheat Qu” has been used in the fermentation of Chinese rice wine for hundreds of years. In this study, a Shaoxing rice wine, “wheat Qu” (machine-made type), extract was analysed by using the metaproteomic approach. All visible 145 separate protein spots in the two-dimensional electrophoresis gel were excised and identified by Matrix-Assisted Laser Desorption Ionisation-Time of Flight/Time of Flight Mass Spectrometry (MALDI-TOF/TOF MS) analysis. Eleven spots represent 10 proteins that originate from the secretion of fungi or bacteria, 112 spots represent 43 proteins from plants, and one spot represents protein from fauna. These proteins possess diverse functions and participate in the fermentation process of Shaoxing rice wine. This is the first reported study on the ecosystem of a traditional wine starter culture, using a novel method that is termed “metaproteomics”.Highlights► Extract of a Shaoxing rice wine “wheat Qu” was analysed using metaproteomic method. ► Within extract metaproteome 10 identified proteins originating from microorganisms. ► Within extract metaproteome 43 identified proteins originating from plants. ► Study of wine starter culture ecosystem by using metaproteomics for the first time.

Two barley varieties, Gan4 and Hamelin, were malted to investigate the evolution of phenolic compounds and antioxidant activity during malting. The antioxidant activity was evaluated with DPPH radical scavenging activity, ABTS radical cation scavenging activity, reducing power, and metal chelating activity. Results showed that malting had significant influences on individual and total phenolic contents as well as antioxidant activities of two barley varieties. The contents of some phenolic compounds and the antioxidant activities decreased significantly during steeping and the early stages of germination and then increased remarkably during the later stages of germination and subsequent kilning. The most phenolic compounds identified in barley were (+)-catechin and ferulic acid, which both changed significantly during malting. Moreover, results from the Pearson correlation analysis showed that there were good correlations among DPPH radical scavenging activity, ABTS radical cation scavenging activity, reducing power, total phenolic content and sum of individual phenolic contents during malting.