Flavor of beer

Beer taste can be spoiled by contaminating bacteria or yeasts. The most common bacteria are lactic and acetic acid producers and T ymomonas. Wild yeasts can be anything other than the intended strain S. uvarum is considered a contaminant of ale fermentations and S. cerevisiae a contaminant of lager fermentations. The common wild yeast contaminants are S. diastaticus and species of Picbia, Candida and Brettanomjces. It may be noted that the flavor of beer may be improved by the ability of yeast to adsorb bitter substances extracted from hops, such as humulones and isohumulones. 

Bisulfite addition products are readily formed at wine pHs (1, 23, 24). The bisulfite addition product is thought to be a more sensory-neutral compound and may be exploited by winemakers as a means of decreasing the aldehydic character of wines (1). Bisulfite addition has also been used to mask the stale flavor of beer which is thought to be largely due to the formation of trans-l-noneml (25). Kaneda et al. (25) used HPLC with fluorescent detection of an o-phthalaldehyde derivative to quantitate and identify individual aldehyde-bisulfite products, however, only acetaldehyde-bisulfite adducts were observed in commercial beers with this method. Hydrolysis of the adducts occurs at pHs greater than 8, therefore by adjusting the pH prior to analysis, total aldehydes (free plus bisulfite bound) can be estimated. At low pHs accurate estimation of free aldehydes is complicated however, by analysis conditions which alter the equilibrium between bound and free forms (temperature, dilution, solvent extraction, analysis time, etc.). 

Reports continue in the 1970s on the ascorbic acid treatment of beer (658-669). Use of ascorbic acid with sulfites shows favorable results on beer quality as described by Scriban and Stienne (662) and Master et al. (669). Analyses of imported beer indicate addition of ascorbates even if not so labeled (665). Kormomicka (667) reported 3 g/hL addition of ascorbic acid extended beer quality 89 days 5 g/hL, 108 days. Baetsle (666), on an industrial scale, found 2 g/hL preserved color and flavor of beer during storage for 66 days. 

C H, o02, Mr 150.18, bp. 224 °C, mp. 9 -10 C (57 °C). Yellowish oil or crystals with a smell like cloves, olfactory threshold 10 ppb V. forms by fermentation or thermally from ferulic acid and other phenol carboxylic acids and is a constituent of the flavors of beer, bread, coffee, popcorn, wine, tar and smoked food. Lit. Arctander, No. 1891 Biochim. Bittphys. Acta789,111 (1984). Maarse, p. 515. - [CAS 7786-61-0]... 

F Gunst, M Verzele. On the sunstmek flavor of beer. J Inst Brewing 84 291-292, 1978. 

Humulone The most prevalent of the three alpha acids present in hops. It is responsible for the bitter flavor of beer. 

In flavor formulations, vanillin is used widely either as a sweetener or as a flavor enhancer, not only in imitation vanilla flavor, but also in butter, chocolate, and aU. types of fmit flavors, root beer, cream soda, etc. It is widely acceptable at different concentrations 50—1000 ppm is quite normal in these types of finished products. Concentrations up to 20,000 ppm, ie, one part in fifty parts of finished goods, are also used for direct consumption such as toppings and icings. Ice cream and chocolate are among the largest outlets for vanillin in the food and confectionery industries, and their consumption is many times greater than that of the perfume and fragrance industry. 

The effect of sunlight, ie, the sunstmck flavor in beer, is caused by the formation of mercaptans. The portion of sunlight that is photochemicaHy active is the blue-green region of the visible spectmm (420—520 nm). 

Water. The character of the water has a great influence on the character of the beer and the hardness of water (alkalinity) manifests itself by the extent of its reaction with the weak acids of the mash. Certain ions are harm fill to brewing nitrates slow down fermentation, iron destroys the colloidal stabihty of beer, and calcium ions give beer a purer flavor than magnesium or sodium ions (Table 7). 

Wine and beer industry Polyphenols can alter color and flavor of products such as wines. There are many aggressive ways of removing polyphenolic compounds, such as using polyvinylpolypyrrolidone (PVPP) or sulfur dioxide. However, polyphenol removal should be selective to avoid the undesirable alteration of the wine s organoleptic characteristics. For this reason, one option is to use laccases that polymerize the polyphenolic compounds during the wine-making process and then to remove these polymers by clarification (Morozova and others 2007). Several papers have reported that laccase is able to remove undesirable polyphenols and produce stable wines with a good flavor. 

This technique can be used to measure low aldehyde levels in beer and to assess the role aldehydes play in the loss of beer flavor with aging. 

We are currently exploring additive or synergistic effects among these aldehydes to explain the stale flavor of aged beer. 

Carbonyl compounds, particular aldehydes, are considered to play an important role in the deterioration of beer flavor and aroma during storage. 

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