Thermal resistance of Saccharomyces yeast ascospores in beers

Milani, Elham A.; Gardner, Richard C.; Silva, Filipa

doi:10.1016/j.ijfoodmicro.2015.04.002

Cited by 26 publications

(32 citation statements)

References 39 publications

(43 reference statements)

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“…For example, the D 55°C -value of S. cerevisiae ascospores in alcohol-free beer was 34.2 min compared with 15.3 min in 7.0% alc/vol beer. [4] Moreover, thermal D 60°C -value of S. cerevisiae ascospores decreased from 6.1 min in apple juice to 1.2 min in apple juice with 6% ethanol. [52] The only HPP study on an alcoholic beverage was carried out by Mok et al [48] He demonstrated a total inactivation of S. cerevisiae vegetative cells in red wine (9% alc/vol) after 300 MPa for 20 min.…”

Section: Effect Of Carbonation and Alcohol Content On The Hpp Inactivmentioning

confidence: 93%

“…For production of ascospores, we used the sporulation method previously described by Milani et al [4] and adapted from Xiao. [54] The culture was initially streaked in the YEPG agar and, after growth, a fresh single colony was inoculated into the presporulation liquid composed of 0.8% yeast extract, 0.3% peptone, 10% glucose, and zinc sulphate 25 mg/L overnight at 28°C.…”

Section: Production Of Ascosporesmentioning

confidence: 99%

“…Ascospores are more resistant to thermal processing than vegetative cells, so inactivation of the ascospores will ensure the inactivation of the corresponding less resistant vegetative cells. [4] The industrial production of beer ends with a process of thermal pasteurization, which aims to stabilize the beer and increase its shelf-life. However, thermal pasteurization of beer alters the flavour.…”

Section: Introductionmentioning

confidence: 99%

“…[5,6] From our previous thermal results with ascospores of DSMZ 1848 S. cerevisiae (the most heat-resistant brewing yeast among the four strains investigated), 15 min at 60°C (= 15 PU) is equivalent to 1.34 log reductions of DSMZ 1848 ascospores. [4] Given that beer is carbonated, contains alcohol and is bittered with hops, which are all natural antimicrobials, a mild pasteurization is effective for its stabilization at room temperature. [7,8] However, the beer industry applies a more severe thermal pasteurization process (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…[13,14] The increase in thermal inactivation of yeast ascospores and other microorganisms with alcohol is well known. [4,52] Hence, the study of the effect of beer alcohol content on the HPP inactivation of yeast ascospores is also important. Beverage carbonation is another parameter that can affect yeast inactivation.…”

Section: Introductionmentioning

confidence: 99%

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Nonthermal pasteurization of beer by high pressure processing: modelling the inactivation ofsaccharomyces cerevisiaeascospores in different alcohol beers

Milani

Silva

2016

High Pressure Research

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The industrial production of beer ends with a process of thermal pasteurization. In this research, the nonthermal pasteurization of beer by high pressure processing (HPP) was carried out. First, the effect of alcohol content on Saccharomyces cerevisiae ascospore inactivation at 400 MPa was studied. The number of ascospores in 0.0%, 4.8%, and 7.0% alc/vol beers for 10 min processing time decreased by 3.1, 4.9, and ≥ 6.0 log, respectively. The Weibull model fitted the ascospore inactivation by HPP in 0.0%, 4.8%, and 7.0% alc/vol beers. At 400 MPa, 7.2 s could ensure the minimum pasteurization of beers and for 600 MPa 5 s were enough for ≥ 7 log reductions. The overall flavour of HPP vs. untreated beers was evaluated for a lager and an ale, with no significant differences between the untreated and HPP beers. Thus, nonthermal HPP is a feasible technology to pasteurize beer with different alcohol contents without heat. ARTICLE HISTORY

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Section: Effect Of Carbonation and Alcohol Content On The Hpp Inactivmentioning

confidence: 93%

Section: Production Of Ascosporesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nonthermal pasteurization of beer by high pressure processing: modelling the inactivation ofsaccharomyces cerevisiaeascospores in different alcohol beers

Milani

Silva

2016

High Pressure Research

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Challenging the assumptions around the pasteurisation requirements of beer spoilage bacteria

et al. 2018

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Current recommendations for beer pasteurisation are based on the study in 1951 by Del Vecchio and coworkers. In this work, 14 beer spoilage bacteria were screened for their ability to grow or survive in ale and stout together with the determination of their thermo tolerance at 60°C. Using a capillary tube method, the D‐value (decimal reduction time) and z‐value (temperature resistance coefficient) of the three thermo tolerant bacteria (Acetobacter pasteurianus, Lactobacillus brevis and Lactobacillus hilgardii) were determined. Validation of pasteurisation at a range of pasteurisation units (PU) in packaged product were performed in a tunnel pasteuriser. This study showed that eight of the 14 microorganisms were able to grow in both beer styles, whilst different thermo tolerances were observed amongst the spoilage bacteria. Effective pasteurisation of the selected microorganisms was achieved at significantly lower PU values than those recommended by the European Brewery Convention Manual of Good Practice. In package pasteurisation conducted at 1.6 PU resulted in greater than an 8‐log reduction in viable cell numbers, resulting in ‘commercial sterility’. Although this study demonstrated that successful pasteurisation was achieved for vegetative cells at significantly lower PU values than those recommended, further studies are required to demonstrate the optimal level of pasteurisation for spore forming bacteria and for yeast. © 2018 The Institute of Brewing & Distilling

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Heat resistance of yeast ascospores and their utilisation for the validation of pasteurisation processes for beers

2021

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Beers and other low pH beverages are often stabilised by pasteurisation. There is a lack of guidance as to how many pasteurisation units are required for effective treatment of novel products so as to avoid over‐pasteurisation. Yeast are common spoilers of such beverages and some species can produce heat resistant ascospores. As ascospores are more heat tolerant than vegetative cells they are ideal marker organisms for validating the effectiveness of beverage pasteurisation processes. In this study, 63 yeast strains were screened for their ability to produce spores with 30 strains showing different spore configurations. The rate of ascospore development during incubation on sporulation medium was also determined. It was found that the heat resistance of the ascospores of different species/strains varied widely with Saccharomyces species producing some of the most heat tolerant spores. Ascospores of Saccharomyces cerevisiae BRYC 501 were the most heat resistant with significantly more (over 6–16 times) heat resistance than heat tolerant lactic acid bacteria. The D‐ and z‐values of Saccharomyces cerevisiae BRYC 501 ascospores were determined in alcoholic and non‐alcoholic versions of two lager beers (American and German). The spores were over 14–18 times more heat tolerant in the non‐alcoholic beers and, accordingly, higher PUs need to be applied. Interestingly, at the same/similar alcohol concentration and pH the yeast ascospores were significantly more heat resistant (1.9–2.5 times) in the American than the German beer which may suggest that bitterness contributed to their heat resistance. © 2021 The Institute of Brewing & Distilling

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Thermal resistance of Saccharomyces yeast ascospores in beers

Cited by 26 publications

References 39 publications

Nonthermal pasteurization of beer by high pressure processing: modelling the inactivation ofsaccharomyces cerevisiaeascospores in different alcohol beers

Nonthermal pasteurization of beer by high pressure processing: modelling the inactivation ofsaccharomyces cerevisiaeascospores in different alcohol beers

Challenging the assumptions around the pasteurisation requirements of beer spoilage bacteria

Heat resistance of yeast ascospores and their utilisation for the validation of pasteurisation processes for beers

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