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Qingdao, China

He Y.,Tsingtao Brewing Ltd. | Dong J.,Tsingtao Brewing Ltd. | Yin H.,Tsingtao Brewing Ltd. | Chen P.,Tsingtao Brewing Ltd. | And 2 more authors.
Journal of the Institute of Brewing | Year: 2014

Lager yeast produces a broad range of aroma-active substances during fermentation, of which higher alcohols and volatile esters are vital for the complex flavour of beer. Lager yeast contains several genes that encode the proteins responsible for flavour production. Investigation of gene expression in the hybrid Saccharomyces pastorianus is meaningful as it combines genes from both S. cerevisiae (Sc-type) and S. bayanus (Sb-type). In this study, we developed a GeXP analyser-based multiplex polymerase chain reaction assay to simultaneously assess the transcription of BAP2, BAT1, BAT2, ATF1, ATF2, EEB1, EHT1 and IAH1, involved in higher alcohol and volatile ester biosynthesis, within the S. pastorianus genome from both sub-genomes. GeXP proved to be an effective method of performing a gene expression study by providing a continuous profile of the expression of multiplex genes. This offers the possibility of using this type of data to monitor and control fermentations. Profiles of higher alcohol and volatile ester formation, and the transcription of specific genes, indicated that the synthesis of flavour compounds appears to correlate, at least in part, to the transcription of certain genes. As well as the differential expression of various genes, the differential expression of orthologous genes was also observed during fermentation, suggesting that the Sc-type and Sb-type genes may have different functions. Our results will further the understanding and manipulation of the phenotype of commercially important lager yeasts. © 2014 The Institute of Brewing & Distilling.

Deng Y.,South China University of Technology | Deng Y.,Zhujiang Brewery Co. | Deng Y.,Guangdong Province Key Laboratory for Green Processing of Natural Products and Product Safety | Deng Y.,Tsingtao Brewing Ltd. | And 10 more authors.
International Journal of Food Microbiology | Year: 2015

Lactic acid bacteria (LAB) are the most common beer-spoilage bacteria, regardless of beer type, and therefore pose significant problems for the brewing industry. The aim of this study was to investigate the viable, but putatively non-culturable (VPNC) state of the hard-to-culture beer-spoilage species, Lactobacillus acetotolerans. Upon prolonged contact with degassed beer, L. acetotolerans was found to show decreased culturability. After 17 subcultures in beer, 100-μL aliquots of the culture were no longer culturable on MRS agar until 14days of incubation despite the presence of 105 viable cells, indicating that a large population of cells entered into a VPNC state. Furthermore, a significant reduction or even putative loss of culturability, but maintenance of viability, of L. acetotolerans could also be induced by storing the strain at 0°C for 105days. Adding catalase at a concentration of 1000U/plate enabled the VPNC cells, both induced by beer subculture treatment and cold treatment, to regain culturability with a resuscitation time of 4days and 3days, respectively. Scanning electron microscopy results demonstrated that cells decreased in size and gradually changed morphology from short rods to coccoids when they entered the VPNC state. It was concluded that the difficulty in culturing the spoilage bacterium from brewery environments could be partly attributed the hard-to-culture or the viable, but non-culturable characteristic of this organism. © 2015 Elsevier B.V.

Hao J.,Tsingtao Brewing Ltd. | Dong J.,Tsingtao Brewing Ltd. | Yin H.,Tsingtao Brewing Ltd. | Yan P.,Tsingtao Brewing Ltd. | And 6 more authors.
Journal of the American Society of Brewing Chemists | Year: 2014

A simple and sensitive headspace solid-phase microextraction (SPME) and gas chromatography with mass spectrometer detection (GC/MS) method was developed for simultaneous determination of 19 key hop derived aroma compounds at trace levels in beer. Nineteen hop derived aroma compounds were classified into four groups: esters, terpenes, terpenols, and ketones. A PDMS-coated fiber was found to be the most effective with optimum extraction temperature (50°C) and time (60 min). Degassed beer matrix was found to yield better recovery and possess greater reliability with calibration standards than a 5% ethanol/H2O solution. This method is advantageous over conventional extraction methods because it allows for lower detection limits, higher reproducibility and accuracy, and offers simple manipulation. The integration of effective enrichment, qualification, and accurate quantification of a wide variety of compounds in one injection is made possible. Thus, this method promises to be suitable for a routine beer hop-Aroma analysis and applicable for quality control of aroma hop usage and hop aroma assessment during the brewing process and finished beer. The result of evolution of them during Chinese lager brewing process suggests that the esters and free terpenols derived from the yeast metabolism and biotransformation of glycosidically bound terpenols play more important roles. © 2014 American Society of Brewing Chemists, Inc.

He Y.,Tsingtao Brewing Ltd. | Dong J.,Tsingtao Brewing Ltd. | Yin H.,Tsingtao Brewing Ltd. | Zhao Y.,Tsingtao Brewing Ltd. | And 6 more authors.
Journal of the Institute of Brewing | Year: 2014

The most significant factors influencing beer quality are the variety of aroma flavours that stem from a complex system of interactions between many hundreds of compounds. With increasing demand for flavour control and enhanced productivity, the presence of consistent and balanced amounts of higher alcohols and esters are critical aspects of process control. Extensive research has focused on the formation of flavour compounds by the brewing yeast and the factors that influence their synthesis. Fermenting wort is a complex medium from which the brewing yeast utilizes nutrients for living and growth and to where it places its metabolic by-products. Thus, changes in wort composition will greatly influence final beer aroma. The current paper reviews up-to-date knowledge on the contribution of wort composition to the flavour quality of the final product, in particular higher alcohols and esters. Different wort constituents involved in the biosynthesis of these aromatic substances, and which therefore require control during brewery fermentations, are reviewed. © 2014 The Institute of Brewing & Distilling.

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