COLD STERILE FILTRATION: A SMALL SCALE FILTRATION TEST AND INVESTIGATION OF MEMBRANE PLUGGING

Non-starch polysaccharides in beer and brewing: A review of their occurrence and significance

It has become apparent that beer (both alcoholic and nonalcoholic) contains appreciable amounts of non-starch polysaccharides, a broad subgroup of dietary fiber. It is worth noting that the occurrence of non-starch polysaccharides in alcoholic beer does not imply this should be consumed as a source of nutrition. But the popularity of nonalcoholic beer is growing, and the lessons learnt from non-starch polysaccharides in brewing can be largely translated to nonalcoholic beer. For context, we briefly review the origins of dietary fiber, its importance within the human diet and the significance of water-soluble dietary fiber in beverages. We review the relationship between non-starch polysaccharides and brewing, giving focus to the techniques used to quantify non-starch polysaccharides in beer, how they affect the physicochemical properties of beer and their influence on the brewing process. The content of non-starch polysaccharides in both regular and low/nonalcoholic beer ranges between 0.5 - 4.0 g/L and are predominantly composed of arabinoxylans and β-glucans. The process of malting, wort production and filtration significantly affect the soluble non-starch polysaccharide content in the final beer. Beer viscosity and turbidity are strongly associated with the content of non-starch polysaccharides.

A Glycoside Hydrolase Family 62 A-L-Arabinofuranosidase from Trichoderma Reesei and Its Applicable Potential during Mashing

Arabinoxylan is the second most abundant component in the endosperm cell wall of barley and it has been shown to have negative effects on the viscosity and filtration rate of wort and beer. In this study, a glycoside hydrolase (GH) family 62 α-L-arabinofuranosidase (AFase), termed as TrAbf62A, was purified from the culture filtrate of Trichoderma reesei CICC 41495 by a combined chromatographic method. The preferred substrates of the purified TrAbf62A were soluble, highly substituted arabinoxylan oligosaccharides and polymers, similar to the type found in barley grain. TrAbf62A exhibited activity towards oligomeric and polymeric arabinoxylans, as well as colorimetric arabinose-based substrates, thus meeting the criteria to be classified as a type B AFase. TrAbf62A released mainly arabinose and xylose from soluble wheat arabinoxylan, thus indicating a dual lytic enzyme activity. Supplementation of TrAbf62A during mashing, with a loading of 12 mU/g malt, resulted in a 36.3% decrease in arabinoxylan polymer content, a 5.6% reduction in viscosity, and finally, a 22.1% increase in filtration rate. These results revealed that TrAbf62A has a high potential value in improving lautering performance during mashing.

Tracking polysaccharides through the brewing process

Brewing is a highly complex stepwise process that starts with a mashing step during which starch is gelatinized and converted into oligo- and/or monosaccharides by enzymes and heat. The starch is mostly degraded and utilised during the fermentation process, but grains and hops both contain additional soluble and insoluble complex polysaccharides within their cell walls that persist and can have beneficial or detrimental effects on the brewing process. Previous studies have mostly been restricted to analysing the grain and/or malt prior to entering the brewing process, but here we track the fates of polysaccharides during the entire brewing process. To do this, we utilised a novel approach based on carbohydrate microarray technology. We demonstrate the successful application of this technology to brewing science and show how it can be utilised to obtain an unprecedented level of knowledge about the underlying molecular mechanisms at work.

Application and possible benefits of high hydrostatic pressure or high-pressure homogenization on beer processing: A review

Beer is the most consumed beverage in the world, especially in countries such as USA, China and Brazil.It is an alcoholic beverage made from malted cereals, and the barley malt is the main ingredient, added with water, hops and yeast. High-pressure processing is a non-traditional method to preserve food and beverages. This technology has become more interesting compared to heat pasteurization, due to the minimal changes it brings to the original nutritional and sensory characteristics of the product, and it comprises two processes: high hydrostatic pressure, which is the most industrially used process, and high-pressure homogenization. The use of high pressure almost does not affect the molecules that are responsible for the aroma and taste, pigments and vitamins compared to the conventional thermal processes. Thus, the products processed by high-pressure processing have similar characteristics compared to fresh products, including beer. The aim of this paper was to review what has been investigated about beer processing using this technology regarding the effects on physicochemical, microbiology and sensory characteristics and related issues. It is organized by processing steps, since high pressure can be applied to malting, mashing, boiling, filtration and pasteurization. Therefore, the beer processed with high-pressure processing may have an extended shelf-life because this process can inactivate beer spoilage microorganisms and result in a superior sensory quality related to freshness and preservation of flavors as it does to juices that are already commercialized. However, beyond this application, high-pressure processing can modify protein structures, such as enzymes that are present in the malt, like α- and β-amylases. This process can activate enzymes to promote, for example, saccharification, or instead inactivate at the end of mashing, depending on the pressure the product is submitted, besides being capable of isomerizing hops to raise beer bitterness. As a consequence, the process may reduce steam demand and residue generation. Therefore, the use of high-pressure processing can potentially replace or be combined with heat processes usually applied to beer, thus bringing benefits to the sensory quality of the product and to the environment.

Novel Barley (1→3,1→4)-β-Glucan Endohydrolase Alleles Confer Increased Enzyme Thermostability

Barley (1→3,1→4)-β-glucan endohydrolases (β-glucanases; EI and EII) are primarily responsible for hydrolyzing high molecular weight (1→3,1→4)-β-glucans (β-glucan) during germination. Incomplete endosperm modification during malting results in residual β-glucan that can contribute to increased wort viscosity and beer chill haze. Four newly identified forms of EI and EII and the reference enzymes EI-a and EII-a were expressed in Escherichia coli, and the recombinant proteins were characterized for enzyme kinetics and thermostability. EI and EII variants that exhibited higher residual β-glucanase activity than EI-a and EII-a after heat treatment also exhibited increased substrate affinity and decreased turnover rates. The novel EII-l form exhibited significantly increased thermostability compared with the reference EII-a when activity was measured at elevated temperature. EII-l exhibited a T₅₀ value, which indicates the temperature at which 50% of β-glucanase activity remains, 1.3 °C higher than that of EII-a. The irreversible thermal inactivation difference between EII-a and EII-l after 5 min of heat treatment at 56 °C was 11.9%. The functional significance of the three amino acid differences between EII-a and EII-l was examined by making combinatorial mutations in EII-a using site-directed mutagenesis. The S20G and D284E amino acid substitutions were shown to be responsible for the increase in EII-1 thermostability.

Membrane processing technology in the food industry: food processing, wastewater treatment, and effects on physical, microbiological, organoleptic, and nutritional properties of foods

Membrane processing technology (MPT) is increasingly used nowadays in a wide range of applications (demineralization, desalination, stabilization, separation, deacidification, reduction of microbial load, purification, etc.) in food industries. The most frequently applied techniques are electrodialysis (ED), reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF). Several membrane characteristics, such as pore size, flow properties, and the applied hydraulic pressure mainly determine membranes' potential uses. In this review paper the basic membrane techniques, their potential applications in a large number of fields and products towards the food industry, the main advantages and disadvantages of these methods, fouling phenomena as well as their effects on the organoleptic, qualitative, and nutritional value of foods are synoptically described. Some representative examples of traditional and modern membrane applications both in tabular and figural form are also provided.

Impact of flavouring substances on the aggregation behaviour of dissolved barley β-glucans in a model beer

Structural polymers such as cereal β-glucan may cause various processing problems in beverage industry depending on concentration, molar size distribution and agglomeration behaviour. In this context, influences of the beer volatiles dodecanoic acid, octyl butanoate, ethyl decanoate and decyl acetate on molar mass and radii of barley β-glucan were investigated in ethanolic (4% w/w) model solution. After addition of 100mg/l ethyl decanoate and decyl acetate to the β-glucan solution, a wider-ranging molar mass distribution could be observed by means of asymmetric field-flow-fractionation. Due to agglomeration, average molar mass of β-glucan standard (MW=6.8×10(6)g/mol) increased by 2×10(6)g/mol (P<0.05) in solution containing decyl acetate. Furthermore, a significant growth (P<0.05) from 86 to 102 nm in gyration radius was measured. The obtained results elucidate the importance of fatty acid derived flavouring substance composition in beer regarding the aggregation behaviour of β-glucan.

Identification of two key genes controlling chill haze stability of beer in barley (Hordeum vulgare L)

Background

In bright beer, haze formation is a serious quality problem, degrading beer quality and reducing its shelf life. The quality of barley (Hordeum vulgare L) malt, as the main raw material for beer brewing, largely affects the colloidal stability of beer.

Results

In this study, the genetic mechanism of the factors affecting beer haze stability in barley was studied. Quantitative trait loci (QTL) analysis of alcohol chill haze (ACH) in beer was carried out using a Franklin/Yerong double haploid (DH) population. One QTL, named as qACH, was detected for ACH, and it was located on the position of about 108 cM in chromosome 4H and can explain about 20 % of the phenotypic variation. Two key haze active proteins, BATI-CMb and BATI-CMd were identified by proteomics analysis. Bioinformatics analysis showed that BATI-CMb and BATI-CMd had the same position as qACH in the chromosome. It may be deduced that BATI-CMb and BATI-CMd are candidate genes for qACH, controlling colloidal stability of beer. Polymorphism comparison between Yerong and Franklin in the nucleotide and amino acid sequence of BATI-CMb and BATI-CMd detected the corresponding gene specific markers, which could be used in marker-assisted selection for malt barley breeding.

Conclusions

We identified a novel QTL, qACH controlling chill haze of beer, and two key haze active proteins, BATI-CMb and BATI-CMd. And further analysis showed that BATI-CMb and BATI-CMd might be the candidate genes associated with beer chill haze.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1683-1) contains supplementary material, which is available to authorized users.

Impact of low hydration of barley grain on β-glucan degradation and lipid transfer protein (LTP1) modifications during the malting process

One of the objectives of the malting industry is to reduce the energy cost during kilning without major effect on malt quality. In this study, the impact of a low hydration steeping process on lipid transfer protein (LTP1) modifications and β-glucan breakdown was evaluated in low (LH) and high (HH) hydrated malts. LTP1 modifications analyzed by MS/MS revealed acylation, glycation, and disulfide bond breakage in both LH and HH malts. LTP1 free amine content measurement and fluorescence of Maillard protein adducts revealed no significant difference between LH and HH malts. Immunolabeling of LTP1 during malting highlighted the diffusion of the protein from the aleurone layer to the endosperm at the end of steeping in both LH and HH malts. By contrast, a significant higher amount of β-glucans was measured in LH malts after five days of germination, whereas no significant difference between LH and HH malts was revealed through immunostaining of β-glucans or evaluation of the endosperm integrity after seven days of germination. The possibility to reduce the effects of a low hydration steeping process on β-glucan hydrolysis by increasing germination time was discussed.

The influence of barley malt protein modification on beer foam stability and their relationship to the barley dimeric alpha-amylase inhibitor-I (BDAI-I) as a possible foam-promoting protein

The foam stability of beer is one of the important key factors in evaluating the quality of beer. The purpose of this study was to investigate the relationship between the level of malt modification (degradation of protein, starch, and so on) and the beer foam stability. This was achieved by examining foam-promoting proteins using two-dimensional gel electrophoresis (2DE). We found that the foam stability of beer samples brewed from the barley malts of cultivars B and C decreased as the level of malt modification increased; however, the foam stability of cultivar A did not change. To identify the property providing the increased foam stability of cultivar A, we analyzed beer proteins using 2DE. We analyzed three fractions that could contain beer foam-promoting proteins, namely, beer whole proteins, salt-precipitated proteins, and the proteins concentrated from beer foam. As a result, we found that in cultivar A, some protein spots did not change in any of these three protein fractions even when the level of malt modification increased, although the corresponding protein spots in cultivars B and C decreased. We analyzed these protein spots by peptide mass finger printing using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. As a result, all of these spots were identified as barley dimeric alpha-amylase inhibitor-I (BDAI-I). These results suggest that BDAI-I is an important contributor to beer foam stability.