Finings are electrically charged and attract yeast residence (Vaughan 1999). Finings are used for the clarification of cloudy beer (Andrews 2008) and most beers use finings to remove the yeast sediments from a beer (Vaughan 1999). Prior to fermentation, brewing yeast is naturally flocculent at this stage; it also carries a negative charge, other smaller particles mostly protein-polyphenol complexes, precipitates at the lower temperature and these may exhibit either a positive or negative charge at beer pH, the sedimentation of the particles exhibiting a negative charge is often enhanced by use of “isinglass” or “white finings” (Freeman et, al. 2003). Finings performance is importance for a number of reasons, the clarification time may have an effect on plant throughput by reducing the storage time needed in cold tanks, also the final clarity attained is important, since it affects the run length achieved by the beer filters and in the case of cash ales and it directly affects product quality, it is also very important that the sediment formed is as compact as possible (Freeman et al. 2003). Over the years many substances have been employed to clarify beer, including egg-white albumen and gelatin, but most efficient has proved to be isinglass (Hornsey 1999). Isinglass is the dried swin-bladder from certain species of fish (Hornsey 1999). Brewers are particular about the quality of isinglass because one type is more effective than others (Andrews 2008). The main source of isinglass are from fish caught in water 10°C either side of the equator such species as catfish, drumfish and threadfins (Hornsey 1999). To prepare finings fit for brewery use the isinglass is removed from the fish and dries naturally and if dried too rapidly the product will lose much of its clarification potential (Hornsey 1999). The finings action of isinglass is attributable to the protein collagen which is present in large quantities (Hornsey 1999). Collagen fining may be used in clarification or precipitation process for example for clarifying portable liquors such as beer and wine (Taylor 1997). On acid hydrolysis, isinglass releases individual tripe polypeptide helices of collagen, each containing numerous positively-charged sites (Hornsey 1999). The mechanism of fining is thought to be associated with electrochemical interactions between these sites on the collagen molecules and the net negative charge on the yeast all surface, thus promoting the sedimentation of large number of cells (Hornsey 1999). Although the principle component of isinglass finings is collagen, small amounts of gelatin are also present. Gelatin is a degradation product of collagen and in some parts of the world, notably the USA it represents the main means of fining beer (Hornsey 1999). The sources of gelatin are normally animal bones and hides. Gelatin has a clarification power approximately one-twentieth of that of collagen (Hornsey 1999).
The thermal stability of collagen from different exhibits great variability and this has been attributed to the amount of cross-linking between the individual helices, the higher the degree of cross-linking the greater the thermal stability however collagen from certain sources can even denature about 15°C rendering it totally impractical for brewery use (Hornsey 1999). All isinglass finings lose their integrity rapidly at temperature above 25°C and storage in the brewery in liquid from should be between 4 and 10°C (Hornsey 1999). Isinglass will also react with lipids and any negatively charge proteins within the bear and these will precipitate out with the yeast (Hornsey 1999). The reactions between finings and brewer’s yeast are seriously retarded by cations of salts, those of higher valency inhibiting more effectively the reactions. The best pH level for fining action is 4.4, but at 4.0 the reaction is almost as good. (Briggs 1999). Copper or kettle fining results in dramatic improvements in cold wort clarity compared to unfined worts and confers several significant process benefits (Leather and Ward 1995).
However some beers do not clarify satisfactory with isinglass finings, this may be due to using to little or too much or the yeast may have a relative small negative charge or concentration of yeast maybe too high, and the poor finings action may be caused by an excess in positively charged colloidal material in beer, therefore auxiliary finings are used, these can be derived from alginates, carrageenin, or silicic acid and having a negative charge, are added to the beer carefully before normal finings in order to precipitate the positively charged collodials (Briggs 1999)
References:
Freeman, Gourrieree, Patel, Dawson, Powell-Evens, Shipper, Evans, Boulton, Grimmentt (2003), Improving the effectiveness of isinglass finings for beer clarification by optimization of the mixing process Part 1 laboratory scale experiments, 109(4) 309-317.
Hornaey Spenser Ian, (1999), The Royal Society of Chemistry, Cambridge, UK.
Briggs, Hough, Stevens, Young (1999), Malting and Brewing Science, Vol 2, hopped wort and beer, second ed., Aspen Publishers, New York.
Vaughan A., (1999), Bitter Harvest, Better Beer, The impact of beer production and consumption on people and the environment, Sustain, London.
Andrews (2008), Food and Beverage Management, Tata McGraw-Hill Ltd, New Delhi.
Leather and Ward (1995), The Effect of Wort pH on Longer Fining Performance, Vol. IO, pp. 187-190, May-June.
Taylor (1997), Collagen Finings and preparation thereof, Dec.
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