Mei Yang

Pharmacological Profile of Xanthohumol, a Prenylated Flavonoid from Hops (Humulus lupulus)

The female inflorescences of hops (Humulus lupulus L.), a well-known bittering agent used in the brewing industry, have long been used in traditional medicines. Xanthohumol (XN) is one of the bioactive substances contributing to its medical applications. Among foodstuffs XN is found primarily in beer and its natural occurrence is surveyed. In recent years, XN has received much attention for its biological effects. The present review describes the pharmacological aspects of XN and summarizes the most interesting findings obtained in the preclinical research related to this compound, including the pharmacological activity, the pharmacokinetics, and the safety of XN. Furthermore, the potential use of XN as a food additive considering its many positive biological effects is discussed.

Purification and characterisation of arabinoxylan arabinofuranohydrolase I responsible for the filterability of barley malt

Daner 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 Daner 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.

Comparative proteomic analysis of Dan'er malts produced from distinct malting processes by two-dimensional fluorescence difference in gel electrophoresis (2D-DIGE).

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 Daner cultivar, processes I and II. The quality of malt produced with process II is considered to be superior to that from process I for Daner by maltsters and brewers. In the present study, comparative proteomic analysis was performed between Daner 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 Daner cultivar, especially for improving filterability, which is often deemed as suboptimal by maltsters and brewers.

Influence of ultrasound assisted thermal processing on the physicochemical and sensorial properties of beer

The aim of this study was to investigate the effect of ultrasound assisted thermal processing also known as thermosonication (TS) on selected physicochemical and sensorial properties of beer. A typical Chinese lager beer was treated by TS (24kHz frequency and 2.7W/mL volumetric power) for 2min at 40, 50, and 60°C, respectively. The main quality attributes of the beer, such as ethanol content, original extract, pH, and bitterness, were scarcely affected by three TS treatments. However, a significant increase in color value was observed after TS treatment at 60°C during storage. The protein sensitivity and colloidal haze of three TS-treated beers increased slightly. The results also revealed that the development of both yeast and spoilage bacteria (including lactic acid bacteria and aerobic bacteria) was inhibited for 12months of storage for the TS-treated samples except for the TS-treated beer at 40°C. Additionally, the TS-treated beer at 60°C resulted in a higher thermal load relative to other two TS samples (at 40 and 50°C) based on the results of oxidative stability. TS treatment at 60°C also had a minor negative effect on the volatile profile by increasing staling compounds compared with other two TS treatments. These results obtained therefore may serve as a reference of the potential application of the ultrasound assisted thermal treatment for the beer processing.

Characterization of Barley Serpin Z7 That Plays Multiple Roles in Malt and Beer

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.