Martin Zarnkow
TUM, Research Center Weihenstephan for Brewing and Food Quality, Department Member
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SummaryThe wet vacuum impregnation (WVI) was used in malting process to reduce soaking period. To implement WVI during steeping, vacuum pressure of 500 mmHg for 300 s, was applied twice on five Thai barley cultivars. The effect of WVI on... more
SummaryThe wet vacuum impregnation (WVI) was used in malting process to reduce soaking period. To implement WVI during steeping, vacuum pressure of 500 mmHg for 300 s, was applied twice on five Thai barley cultivars. The effect of WVI on germination energy, moisture content, phenolic acids, antioxidant activity (AOA) and malt quality were examined relative to Central European Commission for Brewing Analysis (MEBAK) malting condition. Moisture content in barley soaked by WVI and MEBAK steeping method were in the range of 36.1–39.9% and 39.9–47.8%, respectively with germination energy of 96–97%. The physicochemical properties of malt from steeping via WVI and MEBAK showed the malts were protein‐rich cultivars, adequate β enzyme and low α amylase activities, hence, low‐malt extract. Total fermentable sugars were relative higher in MEBAK malts than WVI malts. Nevertheless, steeping by WVI had higher free and bound phenolic acids, which led to higher AOA via ABSTS and DPPH assays in some...
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Saccharomyces pastorianus, which is responsible for the production of bottom-fermented lager beer, is a hybrid species that arose from the mating of the top-fermenting ale yeast Saccharomyces cerevisiae and the cold-tolerant Saccharomyces... more
Saccharomyces pastorianus, which is responsible for the production of bottom-fermented lager beer, is a hybrid species that arose from the mating of the top-fermenting ale yeast Saccharomyces cerevisiae and the cold-tolerant Saccharomyces eubayanus around the start of the 17th century. Based on detailed analysis of Central European brewing records, we propose that the critical event for the hybridization was the introduction of top-fermenting S. cerevisiae into an environment where S. eubayanus was present, rather than the other way around. Bottom fermentation in parts of Bavaria preceded the proposed hybridization date by a couple of hundred years and we suggest that this was carried out by mixtures of yeasts, which may have included S. eubayanus. A plausible case can be made that the S. cerevisiae parent came either from the Schwarzach wheat brewery or the city of Einbeck, and the formation of S. pastorianus happened in the Munich Hofbräuhaus between 1602 and 1615 when both wheat ...
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Public–private partnerships are subject to intense scrutiny. This is specifically the case for sensitive health-related topics such as alcohol consumption. The brewing sector and representatives of the scientific community therefore... more
Public–private partnerships are subject to intense scrutiny. This is specifically the case for sensitive health-related topics such as alcohol consumption. The brewing sector and representatives of the scientific community therefore stressed the need for specific principles for the proper and transparent governance of research and other collaborations between the brewing sector and research entities. At a 1-day seminar, a group of scientists and representatives from the brewing and food sector reached a consensus for such principles. They adhere to the following four fundamental conditions: Freedom of research, Accessibility, Contextualisation and Transparency. The points of focus in the FACT principles are open science, meaning that the methods and results are made accessible and reusable, and relationships are clearly disclosed. Actions to be taken for dissemination and implementation of the FACT Principles are, for instance, publishing them on public websites, including them in f...
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This research demonstrated an excellent potential approach for utilizing Miang fermentation broth (MF-broth), a liquid residual byproduct from the Miang fermentation process as a health-targeted beverage. One hundred and twenty yeast... more
This research demonstrated an excellent potential approach for utilizing Miang fermentation broth (MF-broth), a liquid residual byproduct from the Miang fermentation process as a health-targeted beverage. One hundred and twenty yeast strains isolated from Miang samples were screened for their potential to ferment MF-broth and four isolates, P2, P3, P7 and P9 were selected, based on the characteristics of low alcoholic production, probiotic properties, and tannin tolerance. Based on a D1/D2 rDNA sequence analysis, P2 and P7 were identified to be Wikerhamomyces anomalus, while P3 and P9 were Cyberlindnera rhodanensis. Based on the production of unique volatile organic compounds (VOCs), W. anomalus P2 and C. rhodanensis P3 were selected for evaluation of MF-broth fermentation via the single culture fermentation (SF) and co-fermentation (CF) in combination with Saccharomyces cerevisiae TISTR 5088. All selected yeasts showed a capability for growth with 6 to 7 log CFU/mL and the average ...
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Rye is used in some applications in the food and beverage industry and for the preparation of functional foods. It is an interesting raw material in malting and brewing due to its characteristic contribution to the beer’s color,... more
Rye is used in some applications in the food and beverage industry and for the preparation of functional foods. It is an interesting raw material in malting and brewing due to its characteristic contribution to the beer’s color, turbidity, foam and aroma. The aim of this work was to optimize the micro-malting process of a rye landrace. The response surface methodology (RSM) was applied to study the influence of three malting parameters (germination time, germination temperature and degree of steeping) on the quality traits of malted rye. Long germination times at high temperatures resulted in an increase in the extract and Kolbach index. The model for the apparent attenuation limit showed a particular pattern, whereby time and temperature inversely influenced the response. The lowest viscosities were determined in the worts produced from highly modified malts. Optimization of the variables under study was achieved by means of a desirability function and a genetic algorithm. The two ...
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Nonalcoholic beers are becoming increasingly popular, in part due to consumers’ awareness of a healthier lifestyle. Additionally, consumers are demanding diversification in the product range, which can be offered by producing nonalcoholic... more
Nonalcoholic beers are becoming increasingly popular, in part due to consumers’ awareness of a healthier lifestyle. Additionally, consumers are demanding diversification in the product range, which can be offered by producing nonalcoholic beers using non-Saccharomyces yeasts for fermentation to create a wide variety of flavors. So far, little is known about the nutritionally relevant byproducts that these yeasts release during wort fermentation and whether these yeasts can be considered safe for food fermentations. To gain insights into this, the B vitamins of four different nonalcoholic beers fermented with the yeast species Saccharomycodes ludwigii, Cyberlindnera saturnus (two strains), and Kluyveromyces marxianus were analyzed. Furthermore, a total of 16 beers fermented with different non-Saccharomyces yeast strains were analyzed for biogenic amines. Additionally, stress tolerance tests were performed at 37°C and in synthetic human gastric juice in vitro. B vitamins were found in...
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The basic step in beer production is mashing, during which insoluble starch chains, and to a lesser extent cell walls and proteins are broken down by enzymatic hydrolysis. Since the beginning of the modern brewing process there have been... more
The basic step in beer production is mashing, during which insoluble starch chains, and to a lesser extent cell walls and proteins are broken down by enzymatic hydrolysis. Since the beginning of the modern brewing process there have been empirical studies into the optimum effective temperatures of the corresponding enzymes, and mashing has been carried out accordingly. The resulting resting temperatures of proteolysis, cytolysis and amylolysis with the maltose and saccharification rest, are now rarely changed, only being adapted to the properties of the raw materials used to a limited extent. New varieties of barley and other raw materials used in breweries, as well as modern processes in malting plants, ensure better enzyme potential and optimized malt gelatinization temperatures. The aim of this paper is to determine enzyme activity in barley malt during mashing. For this purpose, isothermal mashing was used, i.e., a mashing process with a constant resting temperature over the ent...
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Despite of a well kept tradition over centuries to use oat as malted raw material for wort and beer production today this brewing cereal has been displaced almost completely. Ten different oat varieties where examined for their... more
Despite of a well kept tradition over centuries to use oat as malted raw material for wort and beer production today this brewing cereal has been displaced almost completely. Ten different oat varieties where examined for their acceptability as brewing cereals and malted. The most favourable sample has even been used to brew different types of beer in pilot scale. The pilot maltings of these samples have been done in a 1 kg scale with 45 % moisture content, isotherm at 14,5 °C (8 and 9 d vegetation time) and with a kilning temperature of 80 °C/3 h. The beer was brewed either in a 1,5 kg or a 10 kg pilot plant. In both cases a lauter tun was used for solid-liquid-separation. Hot break was separated with a whirlpool. The wort was pitched at 10 °C with top fermenting wheat beer yeast (< 5 % dead cells, methylenblue-test) which was been cultivated several times in oat wort. After three days of main fermentation a maturation step at 16 °C and a two week storage time at 0 °C followed. The resulting beers have not been stabilised or filtered. The varieties differed only little. The malt with the extended malting time of one day demonstrated better levels of enzymatic activities and modification. Therefore the batch which was used for the brewing trials was malted with nine day vegetation time. All ten oat varieties had low levels of extract caused by the high level of husk material, which requires quite high proportion of water for mashing. The high portion of fatty acids was degraded only to a small amount. The low foam levels could be explained by the presence of fatty acids since they are not assimilated completely by the yeast. In addition fatty acids have a negative effect on flavour stability. In comparison to barley malt oat malt have considerably lower levels of enzymatic activity. On this account the enzymatic rests during mashing where noticeable laboured. Saccharification and lautering took place in a fast way. Main fermentation, maturation and storage ran smooth and efficient. All three beer types produced (Schank-, Voll- und Starkbier) offered a pleasant top fermenting aroma which still differ from the familiar southern german wheat beer aroma. The trials demonstrate that the cereal oat does contain a potential to produce a drinkable pleasing beer.vokMyynti MTT tietopalvelu
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The diversification of beer flavor is becoming increasingly popular, especially in the field of non-alcoholic beers, where sales are growing steadily. While flavor substances of traditional beers can largely be traced back to defined... more
The diversification of beer flavor is becoming increasingly popular, especially in the field of non-alcoholic beers, where sales are growing steadily. While flavor substances of traditional beers can largely be traced back to defined secondary metabolites, the production of non-alcoholic beers with non-Saccharomyces yeasts generates novel fruity flavors, some of which cannot yet be assigned to specific flavor substances. In a recently published study, besides pear, cool mint sweets, and banana-like flavor, distinctive red berry and apple flavors were perceived in a non-alcoholic beer fermented with the yeast strain Cyberlindnera saturnus TUM 247, whose secondary metabolites were to be elucidated in this study. The trials were carried out using response surface methodology to examine the fermentation properties of the yeast strain and to optimize the beer with maximum fruitiness but minimal off-flavors and ethanol content. It turned out that a low pitching rate, a moderate fermentati...
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In this paper, we present a constant temperature mashing procedure where grist made of Pilsner malt is mashed-in directly in the temperature regime of alpha-amylase activity, thus omitting all conventional steps, followed by constant... more
In this paper, we present a constant temperature mashing procedure where grist made of Pilsner malt is mashed-in directly in the temperature regime of alpha-amylase activity, thus omitting all conventional steps, followed by constant temperature mashing at 72 °C. The aim was to investigate an alternative mashing procedure for the production of alcohol-reduced beers. The mashing proceeds with a rapid buildup of sugars and is completed after 120 min at the latest, giving an iodine normal and clear wort. However, the distribution of the different sugars in the worts is strongly altered, in comparison to a more classical mashing procedure. The free amino nitrogen (FAN) concentration is sufficient for vivid fermentation with the bottom fermenting yeast Saccharomyces pastorianus TUM 34/70. The lag phase and initial fermentation performance of this yeast strain are comparable for conventionally and isothermally (72 °C) mashed wort. Under the given conditions the fermentation of the isother...
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The role of cult and feasting in the emergence of Neolithic communities. New evidence from Göbekli Tepe, south-eastern Turkey
Research Interests: Turkey, Dancing, Beer, Alcohol, Monumentality, and 4 moreFeasting, Epipalaeolithic, Drinking, and Congregation
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Research Interests: Engineering, Biological Sciences, Quinoa, Create healthy gluten free foods, Buckwheat, and 11 moreCHEMICAL SCIENCES, Amino Acids, Chenopodium quinoa, Amino Acid Profile, Fagopyrum Esculentum, Gluten Free, Beer-like Beverages, Saccharomyces pastorianus, Serial repitching, Successive Fermentation, and Amino acid uptake
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Research Interests: Engineering, Chemistry, Food Science, Biology, Biological Sciences, and 13 moreQuinoa, Buckwheat, CHEMICAL SCIENCES, Gluten free foods, Fermentation, Chenopodium quinoa, Fagopyrum Esculentum, Fermentable Sugars, Gluten Free, Beer-like Beverages, Saccharomyces pastorianus, Serial repitching, and Successive Fermentation
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Die Erfindung betrifft ein Verfahren zur Herstellung von Braumalz aus glutenfreien Getreidesorten (auser Reis, Malz und Sorghum bicolor), bei dem man zur Aktivierung der im Getreidekorn enthaltenen Enzyme einen Weichgrad von zwischen 48... more
Die Erfindung betrifft ein Verfahren zur Herstellung von Braumalz aus glutenfreien Getreidesorten (auser Reis, Malz und Sorghum bicolor), bei dem man zur Aktivierung der im Getreidekorn enthaltenen Enzyme einen Weichgrad von zwischen 48 bis 55% in einen Temperaturbereich wahrend Weiche und Keimung von zwischen 18 bis 30°C einstellt und dann in einem Temperaturbereich von zwischen 50 bis 130°C darrt. Die vorliegende Erfindung betrifft auch ein Verfahren zur Herstellung von glutenfreiem Bier unter Verwendung des erfindungsgemas erhaltenen Braumalzes.
The growing interest in non-alcoholic and low alcohol beers (NABLAB) has fuelled research into innovative production methods. One means to produce NABLAB is through limited fermentation by non-Saccharomyces yeasts which have a naturally... more
The growing interest in non-alcoholic and low alcohol beers (NABLAB) has fuelled research into innovative production methods. One means to produce NABLAB is through limited fermentation by non-Saccharomyces yeasts which have a naturally low fermentative capacity in cereal-based wort substrates. At the same time, adjunct brewing, the partial replacement of barley malt on the grain bill, enjoys growing popularity. In this study, 13 cereals, pseudocereals, and pulses were investigated for their suitability to produce a wort with limited amounts of fermentable sugars. Subsequently, the fermentation performance of two non-Saccharomyces yeast strains, namely Cyberlindnera subsufficiens C6.1 and Lachancea fermentati KBI 12.1, in the produced worts was investigated and compared to that of a brewers’ yeast strain. The worts were produced by harnessing endogenous amylolytic enzyme activity or the addition of an external amylase and analysed for their sugar composition and free amino acids (FAA) profile. All alternative substrates without endogenous β-amylase activity were found to be suitable for producing worts with a high proportion of unfermentable sugars. However, the extract yield was low for the pulses and most worts exhibited a low and/or unbalanced FAA profile. The ethanol production was limited and mostly dependent on the sugar spectrum of the worts and the sugar utilization characteristics of the applied yeast strains. The (partial) substitution of barley with alternative substrates when producing NABLAB by non-Saccharomyces yeast can be a means to alter the sugar and FAA profile of the wort, but must be considered in concert with the yeast strains’ characteristics.
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Beer filterability is strongly related to the amount and molar mass distribution of β-glucan. Different commercial quantification methods yield different β-glucan concentrations and beer filterability. In order to acquire detailed... more
Beer filterability is strongly related to the amount and molar mass distribution of β-glucan. Different commercial quantification methods yield different β-glucan concentrations and beer filterability. In order to acquire detailed information on the measureable molar mass and its impact on beer filtration, six high-throughput methods were developed and analysed. These methods involve three calibration standards (Skandinavisk Bryggeri Laboratorium standard, SBL; Megazyme standard for continuous flow analyser, CFA; and 650 kDa standard) and two dyes (Calcofluor and Congo red). Significant correlation was observed between cellulose nitrate membrane filtration and fluorometrically determined β-glucan content (SBL calibration: r = 0.604, P < 0.001; CFA calibration: r = 0.687, P < 0.001). However, no correlation was observed with the colorimetric methods. Polyethersulphone membrane filtration correlated significantly with specific viscosity (r = 0.710, P < 0.001) and fluorometrically determined β-glucan content (CFA calibration: r = 0.586, P < 0.001). However, there was no correlation between the filtration performance of diatomaceous earth and the established beer properties. No correlation between the developed colorimetric and fluorometric methods was found using the SBL and CFA standards. However, a significant correlation was observed with the 650 kDa standard (r = 0.836, P < 0.001). A wide variation, especially between the dyes, was observed in the measurable β-glucan molar mass distribution determined using field-flow fractionation. Our results demonstrate the impact of method parameters on β-glucan concentration. Thus, known β-glucan thresholds regarding filterability must be reconsidered. We conclude that a valid β-glucan quantification method can provide reliable information on beer filterability.
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Water-extractable arabinoxylans (WEAX) are an interesting component of malted cereals for two reasons. On the one hand, they have beneficial attributes for the colonic and overall health of consumers and are a fermentable component of... more
Water-extractable arabinoxylans (WEAX) are an interesting component of malted cereals for two reasons. On the one hand, they have beneficial attributes for the colonic and overall health of consumers and are a fermentable component of dietary fiber in the human diet. On the other hand, they have a negative impact on the production process of malt-based beverages. In this study, the influence of the malting parameters germination temperature, germination time, and moisture content on the resulting WEAX content of malts produced from wheat (Triticum aestivum), rye (Secale cereale), and spelt wheat (T. aestivum spp. spelta) was investigated. The malting parameters were varied according to a design of experiment (DOE) approach (central composite design), and their influence on WEAX content was analyzed using a DOE software package (Design-Expert 7). WEAX levels ranged from 2.38 to 2.92 g/100 g (dry weight basis [dwb]) in malted rye (R2 = 0.914), 0.76 to 1.28 g/100 g (dwb) in malted spelt wheat (R2 = 0.823), and 1.13 to 1.58 g/100 g (dwb) in malted wheat (R2 = 0.815). In rye and wheat, WEAX correlated negatively with wort viscosity, and a negative tendency was observed for spelt wheat.
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The detection of direct archaeological remains of alcoholic beverages and their production is still a challenge in the archaeological sciences, as most of the markers known up to now are either not durable or diagnostic enough to be used... more
The detection of direct archaeological remains of alcoholic beverages and their production is still a challenge in the archaeological sciences, as most of the markers known up to now are either not durable or diagnostic enough to be used as secure prove. The current study addresses this question by experimental work reproducing the malting processes and subsequent charring of the resulting products under laboratory conditions in order to simulate their preservation (by charring) in archaeological contexts and to explore the preservation of microstructural alternations of the involved cereal grains. The experimentally germinated and charred grains showed clearly degraded (thinned) aleurone cell walls. The histological alternations of the cereal grains were observed and quantified using reflected light and scanning electron microscope as well as corresponding morphometric and statistical software. In order to verify the experimental observations of histological alternations, amorphous charred objects (ACO) containing cereal remains originating from five archaeological sites dating to the 4th millennium BCE were considered: Two of these sites are archaeologically recognisable brewing installations from Predynastic Egypt, while the three roughly contemporary central European lakeshore settlements lack such specific context of the analysed cereal-based food remains. The aleurone cell wall thinning known from food technological research and observed in our own experimental material was indeed also recorded in the archaeological finds. The Egyptian materials derive from beer production with certainty, supported by the ample contextual and artefactual data. The Neolithic lakeshore settlement finds currently represent the oldest traces of malting in central Europe, while the bowl-shaped bread-like object possibly even points towards early beer production in central Europe. One major further implication of our study is that the cell wall breakdown in the grain’s aleurone layer can be used as a general marker for malting processes with relevance for a wide range of charred archaeological finds of cereal products.
Research Interests: Archaeology of Beer and Cereal Fermentation, Multidisciplinary, Predynastic and Early Dynastic Egypt, Central and Eastern Europe, Germany, and 10 moreCereal Processing Technology, Brewing, Late Neolithic, Wheat, Switzerland, Barley, PLoS one, Pile Dwellings, Alcoholic Beverages, and UNESCO world heritage
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Alcohol-free beer (AFB) is no longer just a niche product in the beer market. For brewers, this product category offers economic benefits in the form of a growing market and often a lower tax burden and enables brewers to extend their... more
Alcohol-free beer (AFB) is no longer just a niche product in the beer market. For brewers, this product category offers economic benefits in the form of a growing market and often a lower tax burden and enables brewers to extend their product portfolio and promote responsible drinking. Non-Saccharomyces yeasts are known for their flavor-enhancing properties in food fermentations, and their prevailing inability to ferment maltose and maltotriose sets a natural fermentation limit and can introduce a promising approach in the production of AFB (≤0.5% v/v). Five strains isolated from kombucha, Hanseniaspora valbyensis, Hanseniaspora vineae, Torulaspora delbrueckii, Zygosaccharomyces bailii and Zygosaccharomyces kombuchaensis were compared to a commercially applied AFB strain Saccharomycodes ludwigii and a Saccharomyces cerevisiae brewer’s yeast. The strains were characterized for their sugar utilization, phenolic off-flavors, hop sensitivity and flocculation. Trial fermentations were an...