Progress 09/01/04 to 09/30/09
Outputs
OUTPUTS: The project continues to be a vehicle for training MS students and providing opportunities to undergraduate researchers. Presentations have been made in many locations, to both specialist and layman audiences. In this manner, using insightful yet accessible language, key messages have been promulgated on a state, national and international basis. Audiences and locations for these presentations have been DANR - CSREES Program review, Davis CA; Google, Mountain View CA (available on-line), Sierra Nevada brewery, Chico CA: Master Brewers Association of the Americas (MBAA), Davis CA; various student Halls of Residence; Institute of Brewing and Distilling (IBD), South Africa; UC Davis Mini Medical School; Craft Brewers Conference, Boston MA; April 22 2009; International House, Davis CA; MBAA, Chico CA; Association of California School Administrators, Pleasanton, CA; Napa Valley Wine Library Association, St Helena CA; University of Nottingham UK (by videoconference; American Society of Brewing Chemists, Tucson AZ; National Home brewers Conference, Oakland CA; Culinary Institute of America, St Helena CA; Point West Rotary, Sacramento CA; UC Davis retirees, Davis CA; MBAA, Palm Springs CA; UC Berkeley; Napa Valley CA; MBAA, Columbus OH; Grace Episcopal Church , Fairfield CA; Jiangnan University, Wuxi China: Rotary, Marin CA. PARTICIPANTS: Principal investigator was Charles Bamforth. John Smythe, Troy Casey and Jonathan Goldberg were MS students. Hildegarde Heymann is fellow faculty at UC Davis. Candace Wallin is staff at UC Davis. Cluett, Heydenrych, Lamaletie, Eloff and Golob were collaborators from South African Breweries. Simon Jackson is the Chief Executive of the Institute of Brewing and Distilling. Laine Murphey is an MD in Eugene OR. TARGET AUDIENCES: Audiences are the populace of California (and beyond) of legal drinking age. Also, they are the brewing and associated industries. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The enzymology of cell wall degradation in barley during malting and brewing has been further examined and interpreted in the context of beer as a possible source of soluble fiber and prebiotics. Beer produced with entirely novel technology that would obviate the potential presence of deleterious materials and would also be hugely advantageous on an environmental basis (fewer resources, fewer co-products) has been produced and evaluated for sensory properties. Conventional beers and the raw materials and processes used in making them have been evaluated for their content of silicon, an element that has been linked to bone health. Studies have been devoted to understanding the public perception of beer. Approaches to producing beer for people suffering from celiac disease have been reported.
Publications
- Bamforth, C. (2008) Butts and Nasty Smells: effluent treatment. Brewers Guardian, 137(11), 24-26
- Bamforth, C. (2008) The ultimate enzymology: making beer. Food Science and Technology, 22(4), 12-14
- Bamforth, C.W. (2009) Producing gluten-free beer: an overview, in The Science of Gluten-Free Foods and beverages (ed E.K. Arendt & F. Dal Bello), AACC International, St Paul MN, 113-117
- Bamforth, C. (2009) Contraception, charcoal and cows: the world of brewery co-products. Brewers Guardian, 138(1), 24-27.
- Bamforth, C.W. (2009). Beer and the Quality of Life. Proc IBD Africa Convention (no page numbers).
- Smythe, J.E. and Bamforth, C.W. (2009) An evaluation of the public understanding of beer and brewing. MBAA Technical Quarterly, doi:10.1094/TQ-46-1-0316-01
- Bamforth, C. (2009) Beer: Tap into the Art and Science of Brewing. Third edition. Oxford University Press.
- Bamforth, C. (2009) For heavens sake: beer and religion. Brewers Guardian, 139(8), 32-35.
- Bamforth, C. (2009) Fiscal Froth: Beer and Government. Brewers Guardian, 138(9), 26-29
- Bamforth, C. (2009) Bashing Booze: The Anti-Alcohol Lobby. Brewers Guardian, 138(10), 40-43.
- Bamforth, C.W. (2009) Carbon footprints in breweries. MBAA TQ, MBAA TQ doi:10.1094/TQ-46-4-1112-02.
- Casey, T.R. & Bamforth, C.W. (2010) Silicon in Beer and Brewing. J Sci Food Ag, in press
- Heymann H, Goldberg, JR, Wallin CE and Bamforth CW (2010) A beer made from a bland alcohol base. J Am Soc Brew Chem, in press.
- Bamforth, C.W. (2010) The enzymology of cell wall breakdown during malting and mashing: an overview. MBAA TQ, in press.
- Bamforth, C.W. (2009) Current perspectives on the role of enzymes in brewing. J Cereal Sci, 50, 353-357
- Bamforth, C. (2009) Brewmasters Art: The History and Science of Beermaking. Recorded Books, 7 CDs.
- Cluett, J., Heydenrych, M., Bamforth, C.W., Jackson, S., Lamaletie, B., Eloff, K. and Golob, H. (2009) Beer is food: a recipe to sustain the brewing industry in South Africa. Chemical Technology, August, 22-27.
- Bamforth, C.W. (2009) Use of exogenous enzymes in the production of alcoholic beverages. The Encyclopedia of Biotechnology in Agriculture and Food, Taylor and Francis, in press.
- Bamforth, C.W. and Murphey, L.J. (2009) Beer and Health, in MBAA Certified Beer Specialist, in press.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: The project continues to involve the training of MS students. Findings have been reported at diverse meetings and locations, notably Master Brewers Association of the Americas (MBAA), St Louis; Rotary, Sacramento, Sierra Nevada Brewery, Chico; American Academy of Pain Medicine, Orlando; Rocky Mountain Micro-brewing Symposium, Colorado Springs; Anheuser-Busch Brewing School, St Louis; Grain Processing conference, Norwich UK; Institute of Brewing and Distilling, Asia Pacific Section, Ho Chi Minh City, Vietnam; Picnic Day; MBAA Southern California, keynote, Santa Barbara; Anheuser-Busch technical HQ meeting, Scottsdale; Anchor Brewery San Francisco; various Student Halls of Residence; American Society for Mass Spectrometry, Denver, CO; Institute of Food Technologists, New Orleans; Bridgeport Brewery, Portland; Culinary Institute of Amercia, St Helena; Oakland Rotary; Sacramento Midtown Rotary; Capitola Book Cafe; World Brewing Congress Honolulu, August 2008; Harlan Conference, Davis; Point West Rotary, Sacramento; Rotary, Seattle; Rotary, Yakima; Active 20-30, Sacramento; RMI opening; Rotary, Yuba City; MBAA District Philadelphia, Milton, DE; Rotary, Hayward; IAESTE Regional Conference, Davis; Rotary, Birmingham AL, Young Scientists in Malting Brewing and Distilling meeting, Cork, Ireland; San Francisco Rotary; Rotary, Dublin CA. In this way, using entertaining yet responsible presentations, findings have been presented to a wide diversity of people in the state, nationally and internationally. PARTICIPANTS: Principal investigator was Charles Bamforth. Cale May and Stephen Russell were MS students. Paul Singh is fellow faculty at UC Davis. Dr Makoto Kanauchi is a collaborating scientist from Miyagi University, Japan and Dr Young Tack-Lee was a scientist on sabbatical in my laboratory from Kyungwon University, South Korea. TARGET AUDIENCES: Audiences are the population of California (and beyond) of legal drinking age. Audiences are also the brewing, wine-making and associated industries. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Studies have furthered our understanding of the factors impacting the levels of residual soluble fiber and putative prebiotic glucan material in beer. Opportunities for the isolation of antioxidant substances from beer using PVPP have been explored. Models have been investigated for the production of beer according to new paradigms that (inter alia) would eliminate risks of certain undesirable compounds (e.g. nitrosamines, monochloropropanols) from entering beer as well as having significant environmental advantages. Finally a critical appraisal has been made of the relative merits and de-merits of beer and wine as they pertain to human health.
Publications
- Bamforth, C. (2008) Grape versus Grain. Cambridge University Press
- Bamforth, C.W. (ed) (2008) Beer: A Quality Perspective. Handbook of Alcoholic beverages series, Elsevier
- Kanauchi, M. and Bamforth, C.W. (2008) The relevance of different enzymes for the hydrolysis of β-glucans in malting and mashing. J Inst Brew, 114, 224
- Bamforth, C.W. & May, J.C. (2008) The recovery of polyphenols from PVPP and their antioxidant capacity. MBAA Technical Quarterly, 45, 283
- Lee, Y.T. and Bamforth, C.W. (2009) Variations in Solubility of Barley β-Glucan during Malting and Impact on levels of β-Glucan in Wort and Beer. J Am Soc Brew Chem, in press
- Bamforth, C.W. (2009). Beer: Tap into the Art and Science of Brewing, Third Edition. Oxford University Press
- Russell, S.T., Singh, R.P and Bamforth, C.W. (2008) Alternative Paradigms for the Production of Beer. J. Inst. Brew., in press
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: The project has involved the training of several MS students. Findings have been reported at meetings and events in many locations including Sierra Nevada brewery, Chico CA; New York Academy of Sciences; Anheuser-Busch, St Louis; Yuba-Sutter Farm Bureau; Parc Forum, Palo Alto, CA: Special Libraries Association, Denver; Institute of Food technologists, Chicago; University College Cork, Ireland; Fiber Society, Davis CA; Tuolumne County Fram Bureau; Sacramento Rotary; Bohemian Club; Master Brewers Association, Nashville.
PARTICIPANTS: Principal Investigator was Charles Bamforth. Robert Kuntz and Christine Wright were MS students, Janel Owens a PhD student. Christine Bruhn, Hildgarde Heymann and Andrew Clifford are all faculty. All personnel were at UC Davis
TARGET AUDIENCES: Audiences are the population of California (and beyond) of legal drinking age. Audiences are also the brewing and associated industries.
Impacts
The study of the impact of processing on levels of soluble fiber in beer has continued with the study of the development of relevant enzymes during the germination of barley. In particular we have shown how encouragement of the early development of a xylanase will facilitate cell wall mobilization. Regarding the vitamin content of beer, we have shown how existing methods for the assessment of folate have probably over-estimated folate levels in beer and other products. Newer methods were developed and applied, which nevertheless show that some beers do contain significant levels of folate but that the amount probably declines duirng beer storage. An assessment of the likely impact of beer in the diet of celiac sufferers was made and it has been suggested that it is a relatively minor problem for moderate drinkers. Finally it was shown that provision of valid and meaningful information on the nutritive content and potential health impact of beer elevated its status of
acceptability in consumers, but nevertheless health and nutrition impacts are far less significant for product choice than were more hedonic aspects such as taste.
Publications
- Kuntz, R.J. and Bamforth, C.W. (2007) Time Course for the development of enzymes in Barley. J Inst Brew, 113, 196-205
- Bamforth, C.W. (2008) Producing gluten-free beer an overview
- Wright, C.A., Bruhn, C.M., Heymann, H. and Bamforth, C.W. (2008) Beer Consumers Perceptions of the Health Aspects of Alcoholic Beverages. J Food Sci, 73, in press
- Wright, C.A., Bruhn, C.M., Heymann, H. and Bamforth, C.W. (2008) Beer and Wine Consumers Perceptions of the Nutritional Value of Alcoholic and Non-alcoholic Beverages. J Food Sci, 73, in press
- Owens, J.E., Clifford, A.J. & Bamforth, C.W. (2007) Folate in beer. J Inst Brew, 113, 243-248
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Progress 01/01/06 to 12/31/06
Outputs
We have completed the study on measuring soluble fiber and putative prebiotics in beer. Some beers contain sufficient of these materials to make a worthwhlile contribution to the diet. The major focus in 2006 was on the consumer perception of the healthfulness of beer in comparison to other beverages. Red wine was considered to be the most healthful beverage. The perceived healthfulness of a beverage does not appear to be the main factor driving choice. Also, beverages that contain alcohol are perceived as more healthful than certain non-alcoholic beverages. Nutritional information does impact consumers' perceptions of the healthfulness of beverages. Consumers that are predominately beer drinkers were more heavily influenced by nutritional information than consumers who were predominately wine drinkers. The second consumer survey showed that, overall, males and females perceive red wine as the healthiest alcoholic beverage. In general, men rated alcoholic beverages as
more healthful than did women. Overwhelmingly, taste was identified as the leading driver of choice followed by location and activity. On average, consumers receive information about health and nutrition from 3.8 sources. More than half of all consumers identified their doctor as a source of nutritional and health information. In general, consumers over the age of 30 are more accurately informed about the contents of alcoholic beverages than consumers under the age of 30. The fact that beer contains carbohydrates is almost universally known. The lack of nutritional labeling allowed on alcoholic beverages may be the source of the confusion and misperceptions of consumers about the actual contents of alcoholic beverages. A large opportunity to educate consumers about the contents of alcoholic beverages exists. Overwhelmingly, consumers believe that the moderate consumption of alcohol can be good for their health. Consumers rated professionals, scientific studies, and classes or school
as the most credible sources of nutritional information about alcoholic beverages. Subjects rated the beverage industry, the internet, advertisements, and Oprah as the least credible sources of nutritional information about alcoholic beverages. Although these were considered as less credible sources than others, they were still used by consumers as sources of health and nutritional information. In general, consumers of alcoholic beverages are brand loyal, consider themselves to be following a healthy and balanced diet, and believe alcohol can be part of that healthy diet. Participants say they drink what they like and do not concern themselves with the healthfulness or nutritional value of alcoholic beverages. Nevertheless, their perception of healthfulness changed when provided with nutritional information and focus group comments indicated that attitudes toward beverages would be influenced by health information. Outreach articles on the impact of beer on cancer, beer as a source of
antioxidants, addiction and the impact of beer on sexual activity have been written.
Impacts
The work on fiber and prebiotics informs brewers of how to design beers that have significant levels of these materials without encountering process performance problems due to the cell wall polymers from whence they are derived. The consumer study informs brewers and those marketing beer how to deliver responsible and relevant messages concerning the health impact of beer. The outreach articles provide relevant and reliable information on various impacts that beer can have on the body.
Publications
- Bamforth, C.W. (2006) Beer and the dreaded C. Brewers Guardian, 135 (7), 24-26
- Bamforth, C.W. (2006) Radical stuff: beer as an antioxidant source. Brewers Guardian, 135 (8), 24-26
- Bamforth, C. (2006) Alcoholism and Addiction. Brewers Guardian, 135 (9), 40-42
- Bamforth, C. (2006) Please may I have some more? Thoughts on the Drinkability of Beer. Brewers Guardian, 135(10), 17-18
- Bamforth, C.W. and Gambill, S.C. (2007) Fiber and putative prebiotics in beer. J Am Soc Brew Chem, in press.
- Bamforth, C.W. (2007) Beer as liquid bread. Master Brewers Association of the Americas Technical Quarterly, in press
- Bamforth, C.W. (2007) Desire, Drive or Disappointment: Beer and Sex, Brewers Guardian, in press
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Progress 01/01/05 to 12/31/05
Outputs
Three elements of this research project have progressed substantially during the year. In addition work continues on the assimilation of material for a database on "beer and health". a. fiber and prebiotics in beer. Methods have been developed for the assay of soluble fiber and prebiotic substances in beer. One method in particular has particular utility: it uses specific enzymes for the degradation of these substances. There is substantially more low molecular weight prebiotic material than soluble fiber (high molecular weight) in beer but the combined levels are sufficent to suggest that beers can contain useful levels of these substances. A further facet of this work has been our research upstream in the process in unraveling the enzymology of cell wall digestion during the malting of barely and the mashing of malt. We have made a characterization study of esterase enzymes that cleave ferulic acid and acetic acid from the wall polysaccharides, part of the process
whereby molecules are solubilized (i.e. soluble fiber production). Other factors that impact the level of soluble fiber and prebiotics are exogenous enzymes added during mashing, and the relative efficacy of these has been explored. b. antioxidants in beer. A range of methods for assaying antioxidant levels has been explored to show that the ranking of beer in comparison to other beverages, including red wine, very much depends on the assay selected. There is clearly significant antioxidant potential in beer. One of the molecules involved is the ferulic acid released by the esterases (see a above). Other contributors are the polphenolics, and we have been examining the extent to which these are removed from beer by different stabilizing agents. c. the perception of beer. Using questionnaires and study groups, we have demonstrated that the common preconception is that beer is inherently unhealthy and certainly less beneficial in the diet as compared to beverages such as red wine.
However when individuals are alerted to the beneficial components that are found in beer, including vitamins, antioxidants, fiber and the anti-atherosclerotic impact of moderate alcohol consumption, the ranking of beer improves. Our work in exploring the importance of consumer issues such as the use of genetically-modified materials and novel processing techniques has resulted in several publications in the general press. Of particular significance has been our debunking of myths to do with beer in the context of so-called "low carb" diets
Impacts
The work on fiber and prebiotics will inform brewers in respect of strategies to design beers with substantial levels of these useful substances. It will be of value also to users of barley in the production of other foodstuffs. The work on carbohydrates generally and our reminder to brewers that it is alcohol, not carbs, that is the primary calorie source in beer, will help them in the design of genuinely low calorie beers. The work on antioxidants reinforces the understanding that these materials cannot be compared for efficacy, content in food or benefit to the body simply on the basis of a single assay, as is too often claimed. It will help people select reasonable collections of assays to make judgments on antioxidants. The psychophysics work will be of value to consumers and brewers alike in helping to clarify beer's status in the context of an acceptable diet and lifestyle.
Publications
- Mitchell, A.E., Hong, Y.-J., May, J.C., Wright, C.A. and Bamforth, C.W. (2005) A comparison of Polyvinylpolypyrrolidone (PVPP), Silica Xerogel and a Polyvinylpyrrolidone (PVP)-silica co-product for their ability to remove polyphenols from beer. J. Inst. Brew. 111, 2025.
- Scheffler, A. and Bamforth, C.W. (2005) Exogenous Beta-Glucanases and Pentosanases and their impact on mashing. Enzyme and Microbial Technology, 36, 813-817.
- Sun, A., Faulds, C.B. & Bamforth C.W. (2005). Barley contains two cationic acetylxylan esterases and one anionic feruloyl esterase. Cereal Chem, 82, 621-625.
- Bamforth, C.W. (2005). The gene dream a nightmare? Brewers Guardian, 134 (7), 24-26.
- Bamforth, C.W. (2005). Intensifying malting and brewing - does the customer care? Brewers Guardian, 134 (8), 30-32.
- Bamforth, C.W. (2005). Beer, carbohydrates and diet. J Inst Brew, 111, 259-264.
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Progress 01/01/04 to 12/31/04
Outputs
The project has commenced with an ongoing literature assessment of the current global understanding of beer in the context of health, nutrition and well-being. A large part of this body of work has been collated into a book (see Publications). Furthermore, an article detailing the status of beer in the context of society has also been published. This literature watch will continue throughout the project. A layman-targeted article on the myth of beer as a high carb foodstuff has been published, as has an article on Light beers in the same context. Bench work on the analysis of non-digestible carbohydrates (soluble fiber plus pre-biotics) has commenced, as have a psychophysical investigations of the perception of beer alongside other foodstuffs and an evaluation of various procedures for assessing the antioxidant potential of beer polyphenolic species.
Impacts
The project will provide a body of informed and reasoned data to allow realistic and fair-minded decisions to be made about the place of beer as a part of the adult diet. It will provide brewers with information on the merits and de-merits of their products and the consumer with information to allow them to make logical and thoughtful purchase decisions.
Publications
- BAMFORTH, C.W., 2004. Beer - a worthy part of the diet. Brew. Dig. 79: 29
- BAMFORTH, C.W., 2004. An ungrateful subject? Differences of opinion on beer. Brew. Guard. 133 (1): 20-23
- BAMFORTH, C.W., 2004. Beer: Health and Nutrition. Blackwell, Oxford
- BAMFORTH, C.W., 2004. The Light Fantastic. Brew. Guard. 133 (11): 24-25
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Progress 01/01/03 to 12/31/03
Outputs
When bubbled using nitrogen the polypeptides derived by controlled proteinolysis of barley hordein produced more stable foams than did hydrolyzed albumin. At lower levels of bitterness (iso-alpha-acid) addition, there is a reduction in foam stability of albumin-derived polypeptides, not seen for hordein-derived polypeptides. Higher bitterness levels in both instances lead to a stabilisation of foam. This is likely through ionic interactions to the acid anion, and involves divalent cations, because higher pH's (in the range 3.8-4.6) and the addition of zinc enhance foam stability, particularly of albumin-derived fractions. The foaming of the latter is impaired by ethanol, whereas hordein-based foams are enhanced by ethanol. When both hydrolyzed albumin and hydrolyzed hordein are present together the net foam stability is less than anticipated. It appears, therefore, that the observed foam stability of beer is not only dependent on the absolute level of individual
foam-stabilising polypeptides, but on the relative proportions of polypeptides derived from the albumin and hordein protein subsets. This work emphasises for the first time that the observed foaming performance of beer is not determined by the absolute level of one or a very few polypeptides but rather the net result of competitive interactions between polypeptides in the foam matrix, the composition of that matrix also moderating the net foam stability.
Impacts
The data generated in this project will allow brewers to interpret the reasons for observed foaming performance on their beers and identify strategies for ensuring the desired extent of foam stability. The work will inform the design of beverages of all types (not only beers) that are intended to display stable foams.
Publications
- Bamforth, C.W. and Kanauchi, M. 2003. Interactions between polypeptides derived from barley and other beer components in model foam systems. J. Sci. Food Agric. 83:1045-1050
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Progress 01/01/02 to 12/31/02
Outputs
Model proteinases have been used to mimic the proteolytic events occurring in malting and brewing in respect of the foaming properties of albumin and hordein proteins from barley. Hordeins are resistant to the serine proteinase trypsin, but susceptible to the cysteine proteinases ficin and papain. It's the converse for albumins. Both protein fractions are susceptible to yeast proteinase A, explaining the detrimental impact on beer foam of yeast. Partial hydrolysis of hordein enhances its foaming properties, however any proteolysis suffered by albumins is detrimental to foam. Hydrolyzed hordein and hydrolyzed albumin behave differently in their interactions with other components of a model foaming system. Studies continue in this area, however amongst the observations made so far are that zinc and an increased pH over the range 3.5-4.5 have a more positive impact on foams from albumin. Solutions of hydrolyzed hordein are better able to withstand the negative impact of
ethanol. We have concluded our development of models to explain the nucleation of beer foam, such models highlighting the overriding significance of carbon dioxide content to the tendency for bubbles to form, with all other beer parameters (including surface tension and specific gravity) playing minor roles. To underscore the significance of the entire foam research program we have also been pursuing the psychophysics of foam perception by consumers and have established novel methodology to arrive at an appreciation of the international significance of foam to perceived beer quality.
Impacts
Our work on barley proteins is clarifying how malting and brewing operations should be conducted so as to allow stable foam on beer. It will also help commercial concerns optimize the production of whipping agents by the controlled hydrolysis of cereal-based proteins. The work on nucleation is of particular value for its impact on the appearance of beer in the glass.
Publications
- Kapp, G.R., Bamforth, C.W., Kapp, G.R. and Smythe, J.E. 2002 The foaming properties of proteins isolated from barley. J. Sci. Food Agric. 82:1276-1281
- Lynch, D.M. and Bamforth, C.W. 2002 Measurement and characterization of bubble nucleation in beer. J. Food Sci. 67:2692-2701
- Smythe, J.E., O'Mahony, M.A. and Bamforth, C.W. 2002. The impact of the appearance of beer on its perception. J. Inst. Brew. 108:37-42
- Smythe, J.E. and Bamforth, C.W. 2002. The path analysis method of eliminating preferred stimuli (PAMEPS) as a means to determine foam preferences for lagers in European judges based upon image assessment. Food Qual. Pref. In Press.
- Bamforth, C. 2002. Great brewing debates VI. Foaming polypeptides: are they precious? Brewers Guardian. In Press.
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Progress 01/01/01 to 12/31/01
Outputs
Studies have continued into the stability of beer foam and factors determining foam formation (nucleation). Both albumin and hordein proteins from barley can foam. Acid- or heat-denaturation especially of albumin increased foam stability. Foaming properties are also modified by proteolysis, which occurs during malting. Model proteases have been used. Ficin and papain had no effect on the albumin fraction, owing to the presence of an inhibitor in the latter. Hordein, though, was susceptible to proteolysis by these enzymes, with increased foam stability. Excessive proteolysis was detrimental to foam. Trypsin increased foam stability somewhat in hordein, but lessened it in albumin. Yeast Proteinase A caused severe hydrolysis in both proteins, diminishing foam potential. Foam was improved to a greater extent in hordein than in albumin when hop bitter acids were added. A method was developed for assessing nucleation under closely controlled conditions of glass, nucleation
site and environment. Carbon dioxide content was the most influential variable, while typical ranges for surface tension and density usually were not large enough to have a pronounced effect. The most influential factor in nucleation is the physical container. A critical appraisal of the use of a fluorescence marker for assessing hydrophobicity of beer polypeptides was published.
Impacts
Our work on barley proteins is clarifying how malting and brewing operations should be conducted so as to allow a stable foam on beer. It will also help commercial concerns optimize the production of whipping agents by the controlled hydrolysis of cereal-based proteins. The work on nucleation is of particular value for its impact on the appearance of beer in the glass.
Publications
- Bamforth, C.W., Kapp, G.R. and Smythe, J.E. 2001. The measurement of hydrophobic polypeptides in beer using the fluorochrome 1-anilino-8-naphthalenesulfonate. Food Chem. 75:377-383.
- Kapp, G.R. 2001 The foaming properties of albumin and hordein isolated from barley. MS Thesis, University of California, Davis. 104 pp.
- Lynch, D.M. 2001 Physicochemical factors influencing bubble nucleation in beer. MS Thesis, University of California, Davis. 57 pp.
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Progress 01/01/00 to 12/31/00
Outputs
Albumins and hordeins have been extracted from barley and subjected to breakdown using papain. They were assessed for hydrophobicity using the development of fluorescence with ANS and for foam stability using a simple shaking procedure we developed that was shown to be capable of discriminating protein solutions with less than 0.5% difference in concentration. Hordein and albumin were equally capable of generating foam, but bubble size distribution and foam stability differed markedly. The hordein had smaller, more uniform bubbles, as observed visually, with foam height lasting longer. Hordein fraction was approximately 2.5x more fluorescent than the albumin fraction, indicating greater hydrophobicity as expected. As albumins were digested, hydrophobicity increased then decreased, indicating an initial exposure of more hydrophobic regions/peptides followed by their destruction. ANS has been explored for its potential in determining the level of hydrophobic
polypeptides in beer directly; however various interfering parameters indicate this may be of limited promise. A procedure has also been devised to assess the presence of lipophilic foam-damaging materials in beer. The method depends on selective removal of these substances using lipid binding proteins. Methods were developed for differentiating beers based on their ability to produce bubbles (so-called "beading") and in turn this was related to their tendency to release carbon dioxide from solution. Factors determining the rate of this gas release from beers of similar total CO2 content are under investigation.
Impacts
The protein hydrolysis work will allow better control over levels of foaming polypeptides entering beer. The beading method will gain Q.C. use in brew labs. Understanding factors impacting on beading will allow brewers to enhance this desirable aspect of quality. The method for measuring foam-damaging materials is the first applicable method for this class of substances in beer.
Publications
- Dickie K.H., Cann C., Norman E.C., Bamforth C.W. and Muller R.E. 2001. Estimation of foam negative materials in beer using lipid binding proteins. J. Am. Soc. Brew. Chem. 59. In Press.
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Progress 01/01/99 to 12/31/99
Outputs
The impact of foam quality on consumer acceptance of beer has been evaluated. A series of photographs depicting beers differing in foam depth, stability and lacing has been used to gauge what appeals to consumers in US, UK, Germany and Japan. Even those customers claiming to consume beer directly from the container judge beer to be more acceptable when it features a stable foam. However drinkers differ in their perception of lacing: there is a split between those who prefer to see foam sticking to the glass because of its appeal and those who judge this attribute to be unpleasant. It is believed that the nature of the laced foam is at least equally as important as the quantity: the foams produced in this work were from beers bittered using reduced side-chain iso-alpha-acids and these seem to have been judged by many consumers as unpleasant. It has been shown that the method advocated elsewhere for the measurement of foaming polypeptide lacks precision and reliability.
The potential for using a fluorescence-based procedure for measuring directly the level of hydrophobic, foam-stabilizing polypeptides in beer is being explored.
Impacts
This work has confounded the myth that measurement of foam lacing encapsulates all relevant aspects of foam quality. It highlights that laboratory assessment of foam quality must embrace both assessments of foam stability and the appearance of the foam. It indicates that caution needs to be applied in the indiscriminate use of reduced side-chain iso-alpha-acids as foam stabilizing agents.
Publications
- Bamforth, C.W. 1999. Bringing matters to a head: the status of research on beer foam. Proc. Eur. Brew. Conv. Foam Symp., Amsterdam, pp. 10-23.
- Bamforth, C.W. 2000. Perceptions of beer foam. J. Inst. Brew. In press.
- Bamforth, C.W. 2000. In search of quality: 1. Foam. Brew. Guard. In press.
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