Malt derived proteins: Effect of protein Z on beer foam stability

Comparison of recombinant protein Z with natural protein Z derived from malt: From structure to functional properties

Protein Z (PZ) is a prominent albumin found in the endosperm of barley seeds with a molecular weight of approximately 40 kDa. Its multifaceted functional attributes, including trypsin- and thrombin-inhibiting bioactivities and superior foaming properties, have garnered significant attention in research. Considering the post-translational modifications of PZ natural in barley malt, we tried to express recombinant protein Z (rPZ) in E. coli. The present study aims to undertake a comparative analysis between natural PZ and rPZ in order to elucidate their respective characteristics. After spectral analysis, there are significant differences in their secondary and tertiary structures. In addition, rPZ showed superior foamability and foam stability. As for the serpin-like activity, the inhibition rate of rPZ is much higher than that of PZ. In contrast with the inhibition activity, the digestability of rPZ is much lower than that of PZ. As for the cargo carrier properties, rPZ showed an excellent ability to stabilize astaxanthin at 37 °C. These results suggest that rPZ is more suitable as protein carrier, due to the high foamability, serpin-like activity and low digestive stability, which not only give a brief view of recombinant protein, but also give a direction for PZ in cargo delivery.

The Influence of Barley Proteome on Hop Bitter Acid Yield during Brewing

A persistent challenge in brewing is the efficient utilization of hop bitter acids, with about 50% of these compounds precipitating with trub during wort boiling. This study aims to uncover the correlation between the barley cultivar proteome and hop bitter acid utilization during wort boiling. Therefore, comparative experiments were conducted using two cultivars, Liga and Solist, with varying proteomes to identify specific proteins' role in hop bitter acids precipitation. High-performance liquid chromatography (HPLC) was used to measure hop bitter acid content, while liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to quantify and identify proteins. The 107 protein groups, particularly enzymes linked to barley metabolic defense mechanisms, exhibited significant differences between the two cultivars. Results revealed significantly lower α- and iso-α-acid content in wort produced from the barley cultivar Liga. This study highlights the critical role of the barley proteome in optimizing process efficiency by enhancing hop utilization through barley cultivar selection.

Unlocking hot trub's potential: a simple method for extracting bitter acids and xanthohumol

BACKGROUND

Hot trub is a macronutrient- and micronutrient-rich by-product generated in the brewing industry, which is still underrated as a raw material for reprocessing purposes. In this context, this study aimed to investigate the extraction of bitter acids' and xanthohumol from hot trub as well as identify the significance of parameters for the process. The research assessed various extraction parameters, such as pH, ethanol concentration, temperature, and solid-to-liquid ratio, using a Plackett-Burman design.

RESULTS

Ethanol concentration and pH were the most significant parameters affecting extraction yield. β-acids were found to be the principal components of the bitter acids, with a maximum concentration near 16 mg g-1, followed by iso-α-acids and α-acids achieving 6 and 3.6 mg g-1, respectively. The highest yields of bitter acids were observed in the highest ethanol concentration, while pH was relevant to extraction process in treatments with low ethanol ratios. Concerning the xanthohumol extraction, the approach achieved maximum concentration (239 μg g-1) in treatments with ethanol concentration above 30%. Despite their variances, the phytochemicals exhibited comparable extraction patterns, indicating similar interactions with macromolecules. Moreover, the characterization of the solid residues demonstrated that the extraction process did not bring about any alterations to the chemical and total protein profiles.

CONCLUSION

Ethanol concentration was found to have the most significant impact on the extraction of bitter acids and xanthohumol, while temperature had no significant effect. The solid remains resulting from the extraction showed potential for use as a protein source. © 2024 Society of Chemical Industry.

Interactions between humulinone derived from aged hops and protein Z enhance the foamability and foam stability

Foam is one of the important characteristics of beer, including foamability, foam stability and foam texture. Protein Z (PZ) is considered to be an important component of beer foam. In this study, the interaction between PZ and humulinone, a widespread compound in aged hops, and the effect on foam properties of PZ were investigated. The fluorescence spectra showed that the stoichiometric ratio of humulinone to PZ was 4.25 ± 0.48: 1, and the binding constant was (1.64 ± 0.17) × 105 M-1. MD and FTIR results showed that the main force of interaction between PZ and humulinone was hydrogen bond, and the possible sites were Asn-37, Ser-292, Lys-290 and Pro-395. Moreover, the addition of humulinone greatly reduced the surface tension of PZ solution, and changed the secondary structure of PZ, which is beneficial for the foam stability. Under the influence of humulinone, the foamability, foam stability and foam texture of PZ all increased.

Modification mechanism of protein in rice adjuncts upon extrusion and its effects on nitrogen conversion during mashing

The traditional production of wort with adjunct-introduced was achieved by double mashing procedure, which hindered the utilization of proteins in adjunct and led to a deficiency of nitrogen in wort. In this study, the modification mechanism of the extrusion pretreatment on the structure characterization of rice flour protein was investigated. The decoction mashing procedure was performed to enhance the nitrogen conversion of the extruded rice adjunct. Decreased solubility along with disrupted secondary and tertiary structures of rice protein were observed after extrusion. As a result, the total nitrogen, free amino nitrogen, and free amino acids content of wort with extruded rice adjunct-introduced were improved by 23.28 %, 34.67 %, and 7.33 %, respectively, which could be verified by the electrophoretic patterns of the wort protein. The application of extrusion as a pretreatment of adjuncts can promote the protein availability of adjuncts in the decoction mashing stage.

The Influence of Biomolecule Composition on Colloidal Beer Structure

Recent studies have revealed an interest in the composition of beer biomolecules as a colloidal system and their influence on the formation of beer taste. The purpose of this research was to establish biochemical interactions between the biomolecules of plant-based raw materials of beer in order to understand the overall structure of beer as a complex system of bound biomolecules. Generally accepted methods of analytical research in the field of brewing, biochemistry and proteomics were used to solve the research objectives. The studies allowed us to establish the relationship between the grain and plant-based raw materials used, as well as the processing technologies and biomolecular profiles of beer. The qualitative profile of the distribution of protein compounds as a framework for the formation of a colloidal system and the role of carbohydrate dextrins and phenol compounds are given. This article provides information about the presence of biogenic compounds in the structure of beer that positively affect the functioning of the body. A critical assessment of the influence of some parameters on the completeness of beer taste by biomolecules is given. Conclusion: the conducted analytical studies allowed us to confirm the hypothesis about the nitrogen structure of beer and the relationship of other biomolecules with protein substances, and to identify the main factors affecting the distribution of biomolecules by fractions.

Application of Mass Spectrometry-Based Proteomics to Barley Research

Barley (Hordeum vulgare) is the fourth most cultivated crop in the world in terms of production volume, and it is also the most important raw material of the malting and brewing industries. Barley belongs to the grass (Poaceae) family and plays an important role in food security and food safety for both humans and livestock. With the global population set to reach 9.7 billion by 2050, but with less available and/or suitable land for agriculture, the use of biotechnology tools in breeding programs are of considerable importance in the quest to meet the growing food gap. Proteomics as a member of the "omics" technologies has become popular for the investigation of proteins in cereal crops and particularly barley and its related products such as malt and beer. This technology has been applied to study how proteins in barley respond to adverse environmental conditions including abiotic and/or biotic stresses, how they are impacted during food processing including malting and brewing, and the presence of proteins implicated in celiac disease. Moreover, proteomics can be used in the future to inform breeding programs that aim to enhance the nutritional value and broaden the application of this crop in new food and beverage products. Mass spectrometry analysis is a valuable tool that, along with genomics and transcriptomics, can inform plant breeding strategies that aim to produce superior barley varieties. In this review, recent studies employing both qualitative and quantitative mass spectrometry approaches are explored with a focus on their application in cultivation, manufacturing, processing, quality, and the safety of barley and its related products.

Quality attributes for barley malt: "The backbone of beer"

Malting is the process of preparing barley for brewing through partial germination followed by drying. This process softens the grain cell wall and stimulates the production of diastatic enzymes, which convert starch into malt extract. The suitability of a barley grain for malt production depends upon a large number of quality parameters that are crucial for the identification and release of high-quality malt varieties. Maintaining tight control of these quality attributes is essential to ensure high processing efficiency and final product quality in brewery and malt house. Therefore, we have summarized the basic malting process and various physiological and biochemical quality parameters that are desirable for better malt quality. This study may provide an understanding of the process, problems faced, and opportunities to maltsters and researchers to improve the malt efficiency by altering the malting process or malt varieties.

Barley Protein Properties, Extraction and Applications, with a Focus on Brewers' Spent Grain Protein

Barley is the most commonly used grain in the brewing industry for the production of beer-type beverages. This review will explore the extraction and application of proteins from barley, particularly those from brewers’ spent grain, as well as describing the variety of proteins present. As brewers’ spent grain is the most voluminous by-product of the brewing industry, the valorisation and utilisation of spent grain protein is of great interest in terms of sustainability, although at present, BSG is mainly sold cheaply for use in animal feed formulations. There is an ongoing global effort to minimise processing waste and increase up-cycling of processing side-streams. However, sustainability in the brewing industry is complex, with an innate need for a large volume of resources such as water and energy. In addition to this, large volumes of a by-product are produced at nearly every step of the process. The extraction and characterisation of proteins from BSG is of great interest due to the high protein quality and the potential for a wide variety of applications, including foods for human consumption such as bread, biscuits and snack-type products.

Foaming of rhamnolipids fermentation: impact factors and fermentation strategies

Rhamnolipids have recently attracted considerable attentions because of their excellent biosurfactant performance and potential applications in agriculture, environment, biomedicine, etc., but severe foaming causes the high cost of production, restraining their commercial production and applications. To reduce or eliminate the foaming, numerous explorations have been focused on foaming factors and fermentation strategies, but a systematic summary and discussion are still lacking. Additionally, although these studies have not broken through the bottleneck of foaming, they are conducive to understanding the foaming mechanism and developing more effective rhamnolipids production strategies. Therefore, this review focuses on the effects of fermentation components and control conditions on foaming behavior and fermentation strategies responded to the severe foaming in rhamnolipids fermentation and systematically summarizes 6 impact factors and 9 fermentation strategies. Furthermore, the potentialities of 9 fermentation strategies for large-scale production are discussed and some further strategies are suggested. We hope this review can further facilitate the understanding of foaming factors and fermentation strategies as well as conducive to developing the more effective large-scale production strategies to accelerate the commercial production process of rhamnolipids.

DNA authentication of brewery products: basic principles and methodological approaches

Beer DNA authentication is the process of authentication by identification of barley malt Hordeum vulgare or its substitutes, as well as hops and yeast. The method is based on molecular genetic analysis of residual quantities of nucleic acids extracted from the cellular debris of the final product. The aim of the study was to analyse scientific and methodical approaches to extraction of residual quantities of beer raw materials nucleic acids and beer DNA authentication for their later application in determining brewing products authenticity. The technological level discloses the method of DNA extraction from wines, modified for extraction of nucleic acids from beer samples. The method includes the following characteristic peculiarities: stage enzymatic hydrolysis of polysaccharides and polypeptides of dissolved lyophilisate, multiple sedimentation and resursuspension of nucleoproteid complex, RNA removal followed by DNA extraction by organic solvents, and additional DNA purification by magnetic particle adsorption. This review presents the analysis of genetic targets used as molecular markers for gene identification of malting barley varieties and beer DNA authentication. We also provided the interpretation of PCR analysis of Hordeum vulgare varieties and samples of commercial beer. Data on SSR- and SNP-markers of Hordeum vulgare nuclear DNA, used for barley varieties identification and potentially suitable for beer DNA authentication, are also presented. We also analysed genetic targets used in malting barley substitute detection, as well as hops and yeast identification in beer. Data on correlation of amplified DNA targets with beer quality indicators were systematised.