The post-translational modification landscape of commercial beers

Abstract

Beer is one of the most popular beverages worldwide. As a product of variable agricultural ingredients and processes, beer has high molecular complexity. We used DIA/SWATH-MS to investigate the proteomic complexity and diversity of 23 commercial Australian beers. While the overall complexity of the beer proteome was modest, with contributions from barley and yeast proteins, we uncovered a very high diversity of post-translational modifications (PTMs), especially proteolysis, glycation, and glycosylation. Proteolysis was widespread throughout barley proteins, but showed clear site-specificity. Oligohexose modifications were common on lysines in barley proteins, consistent with glycation by maltooligosaccharides released from starch during malting or mashing. O-glycosylation consistent with oligomannose was abundant on secreted yeast glycoproteins. We developed and used data analysis pipelines to efficiently extract and quantify site-specific PTMs from SWATH-MS data, and showed incorporating these features into proteomic analyses extended analytical precision. We found that the key differentiator of the beer glyco/proteome was the brewery, with beer from independent breweries having a distinct profile to beer from multinational breweries. Within a given brewery, beer styles also had distinct glyco/proteomes. Targeting our analyses to beers from a single brewery, Newstead Brewing Co., allowed us to identify beer style-specific features of the glyco/proteome. Specifically, we found that proteins in darker beers tended to have low glycation and high proteolysis. Finally, we objectively quantified features of foam formation and stability, and showed that these quality properties correlated with the concentration of abundant surface-active proteins from barley and yeast.

Proteomics and metabolomics reveal an abundant α-glucosidase drives sorghum fermentability for beer brewing

“…Sorghum samples were searched against all predicted proteins from S. bicolor v3. 1 analyses was performed as previously described (33), protein abundances were re-calculated using a strict 1% FDR cut-off of (21). Normalisation was performed to either the total protein abundance in each sample or to the abundance of trypsin self-digest peptides, as previously described (29).…”

“…The abundance of peptide fragments, peptides, and proteins was determined using PeakView 2.2 (SCIEX) with settings: shared peptides, allowed; peptide confidence threshold, 99%; false 6 discovery rate, 1%; XIC extraction window, 6 min; XIC width, 75 ppm. Protein-centric analyses was performed as previously described (33), protein abundances were re-calculated using a strict 1% FDR cut-off of (21). Normalisation was performed to either the total protein abundance in each sample or to the abundance of trypsin self-digest peptides, as previously described (29).…”

The Influence of Hop Phenolic Compounds on Dry Hopping Beer Quality

“…The analysis of the multiple regression equation for non-alcoholic beer (1) showed that the most significant relationship exists between the original extract data (the amount of grain raw materials) and the concentration of nitrogenous compounds: with an increase in the amount of raw materials used, the content of soluble nitrogenous compounds are reduced, which can be explained by coagulation processes on the part of the beer matrix and high-molecular protein compounds, unstable due to molecular weight, as well as a decrease in nitrogenous compounds in the process of alcohol removal in non-alcoholic beer technology [38][39][40][41].…”

“…The beer's quality as a colloidal system is determined by the organic compounds that form its structure. The grain (malted and unmalted cultures), the plant raw material (hops and hop products), and the yeast strain ultimately determine the sensory profile of the finished beer [1]. It is confirmed that, on the one hand, the overall complexity of the beer proteome is narrow and is caused by the protein molecules of Hordeum vulgare (barley) as a primary source, and yeast, but, on the other hand, there is a large variety of posttranslational modifications (PTMs) created as a result of hydrolytic cleavage (proteolysis), glycation, and glycosylation during malting, mashing, and other technological stages of brewing.…”

“…It is confirmed that, on the one hand, the overall complexity of the beer proteome is narrow and is caused by the protein molecules of Hordeum vulgare (barley) as a primary source, and yeast, but, on the other hand, there is a large variety of posttranslational modifications (PTMs) created as a result of hydrolytic cleavage (proteolysis), glycation, and glycosylation during malting, mashing, and other technological stages of brewing. In particular, it is the protein molecules bound to non-protein components by covalent, ionic, van der Waals interactions that determine the structure and properties of beer [1,2].…”