The identification of a barley haze active protein that influences beer haze stability: The genetic basis of a barley malt haze active protein

Proteome-Based Analysis of Colloidal Instability Enables the Detection of Haze-Active Proteins in Beer

Colloidal haze is a serious quality defect of bright beers that considerably reduces their shelf life and is thought to be triggered by hordeins, a class of proline-rich barley proteins. In this work, the proteomes of fresh and old beers were investigated in bottled pilsners and compared to the protein inventory of haze to identify specific haze-active proteins. Haze isolates dissolved in rehydration buffer contained high concentrations of proteins and sugars but provided protein gels with weak spot signals. Consequently, a treatment for the chemical deglycation with trifluoromethanesulfonic acid was applied, which resulted in the identification of protein Z4, LTP1, CMb, CMe, pUP13, 3a, and Bwiph as constituents of the haze proteome. Because only one hordein was detectable and the proline content in haze hydrolysates was lower than those of barley prolamins, our results suggest that this class of proteins is of minor importance for haze development.

Investigation of overfoaming activities and gushing mechanisms of individual beer ingredients as model substances in bottled carbonated water

BACKGROUND

Researchers in several disciplines are interested in understanding the spontaneous and eruptive overfoaming (gushing) of carbonated beverages, as it is an essential problem of both the brewing and beverage industries. In order to understand the mechanism(s) taking place in gushing beer, several beer ingredients have been investigated as model substances in a much simpler matrix of carbonated water. For this purpose, sinapic acid, vanillic acid, ferulic acid, cinnamic acid and palmitic acid have been chosen as model beer ingredients.

RESULTS

Gushing formation of the investigated beer ingredients depends on the degree of stabilized solvated molecular carbon dioxide in water. For this purpose, functional groups capable of forming hydrogen bonds with electronegative oxygen atoms of carbon dioxide are needed. However, the solubility of the substances plays an important role in the abundance of these functional groups in undissociated form to interact with molecular carbon dioxide.

CONCLUSION

The reported data provide valuable insights into the gushing problem and help to understand its formation pathways. Each gushing-positive substance has an individual mechanism related to its structural conformation and solubility level. Therefore possible gushing mechanisms have been proposed with respect to the structural changes in model substances to clarify the differences in observed overfoaming and gushing stability levels.

Differences in grain ultrastructure, phytochemical and proteomic profiles between the two contrasting grain Cd-accumulation barley genotypes

To reveal grain physio-chemical and proteomic differences between two barley genotypes, Zhenong8 and W6nk2 of high- and low- grain-Cd-accumulation, grain profiles of ultrastructure, amino acid and proteins were compared. Results showed that W6nk2 possesses significantly lower protein content, with hordein depicting the greatest genotypic difference, compared with Zhenong8, and lower amino acid contents with especially lower proportion of Glu, Tyr, Phe and Pro. Both scanning and transmission electron microscopy observation declared that the size of A-type starch molecule in W6nk2 was considerably larger than that of Zhenong8. Grains of Zhenong8 exhibited more protein-rich deposits around starch granules, with some A-type granules having surface pits. Seventeen proteins were identified in grains, using 2-DE coupled with mass spectrometry, with higher expression in Zhenong8 than that in W6nk2; including z-type serpin, serpin-Z7 and alpha-amylase/trypsin inhibitor CM, carbohydrate metabolism, protein synthesis and signal transduction related proteins. Twelve proteins were less expressed in Zhenong8 than that in W6nk2; including barley trypsin inhibitor chloroform/methanol-soluble protein (BTI-CMe2.1, BTI-CMe2.2), trypsin inhibitor, dehydroascorbate reductase (DHAR), pericentrin, dynein heavy chain and some antiviral related proteins. The data extend our understanding of mechanisms underlying Cd accumulation/tolerance and provides possible utilization of elite genetic resources in developing low-grain-Cd barley cultivars.

Exploration of beer proteome using OFFGEL prefractionation in combination with two-dimensional gel electrophoresis with narrow pH range gradients

Two-dimensional gel electrophoresis in combination with mass spectrometry has already been applied successfully to study beer proteome. Due to the abundance of protein Z in beer samples, prefractionation techniques might help to improve beer proteome coverage. Proteins from four lager beers of different origins were separated by two-dimensional electrophoresis (2-DE) followed by tandem mass spectrometric analysis. Initially 52 proteins mostly from Hordeum vulgare (22 proteins) and Saccharomyces species (25 proteins) were identified. Preparative isoelectric focusing by OFFGEL Fractionator was applied prior to 2-DE to improve its resolution power. As a result of this combined approach, a total of 70 beer proteins from Hordeum vulgare (30 proteins), from Saccharomyces species (31 proteins), and from other sources (9 proteins) were identified. Of these, 37 proteins have not been previously reported in beer samples.

Allelic diversity of a beer haze active protein gene in cultivated and Tibetan wild barley and development of allelic specific markers

The formation of haze is a serious quality problem in beer production. It has been shown that the use of silica elute (SE)-ve malt (absence of molecular weight (MW) ∼14000 Da) for brewing can improve haze stability in the resultant beer, and the protein was identified as a barley trypsin inhibitor of the chloroform/methanol type (BTI-CMe). The objectives of this study were to determine (1) the allelic diversity of the gene controlling BTI-CMe in cultivated and Tibetan wild barley and (2) allele-specific (AS) markers for screening SE protein type. A survey of 172 Tibetan annual wild barley accessions and 71 cultivated barley genotypes was conducted, and 104 wild accessions and 35 cultivated genotypes were identified as SE+ve and 68 wild accessions and 36 cultivated genotypes as SE-ve. The allelic diversity of the gene controlling BTI-CMe was investigated by cloning, alignment, and association analysis. It was found that there were significant differences between the SE+ve and SE-ve types in single-nucleotide polymorphisms at 234 (SNP(234)), SNP(313), and SNP(385.) Furthermore, two sets of AS markers were developed to screen SE protein type based on SNP(313). AS-PCR had results very similar to those obtained by immunoblot method. Mapping analysis showed that the gene controlling the MW∼14 kDa band was located on the short arm of chromosome 3H, at the position of marker BPB-0527 (33.302 cM) in the Franklin/Yerong DH population.

Genetic mapping of quantitative trait loci associated with beta-amylase and limit dextrinase activities and beta-glucan and protein fraction contents in barley

High malting quality of barley (Hordeum vulgare L.) relies on many traits, such as beta-amylase and limit dextrinase activities and beta-glucan and protein fraction contents. In this study, interval mapping was utilized to detect quantitative trait loci (QTLs) affecting these malting quality parameters using a doubled haploid (DH) population from a cross of CM72 (six-rowed) by Gairdner (two-rowed) barley cultivars. A total of nine QTLs for eight traits were mapped to chromosomes 3H, 4H, 5H, and 7H. Five of the nine QTLs mapped to chromosome 3H, indicating a possible role of loci on chromosome 3H on malting quality. The phenotypic variation accounted by individual QTL ranged from 8.08% to 30.25%. The loci of QTLs for beta-glucan and limit dextrinase were identified on chromosomes 4H and 5H, respectively. QTL for hordeins was coincident with the region of silica eluate (SE) protein on 3HS, while QTLs for albumins, globulins, and total protein exhibited overlapping. One locus on chromosome 3H was found to be related to beta-amylase, and two loci on chromosomes 5H and 7H were found to be associated with glutelins. The identification of these novel QTLs controlling malting quality may be useful for marker-assisted selection in improving barley malting quality.