University Of Gondar

Faculty of Natural and Computational Science

Department of Chemistry

Prepared By: Aschalew Fikru

2013 G.C 1

The Nature, Formation,

Prevention of Beer Hazes

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Outlines

1. Introduction 2. Colloidal stabilization of beer 2.1 The Origin of Beer Particles 2.2 Mechanism of Non biological Haze Formation 2.3 Factors Affecting Quantity of Cold Trub Produced

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2.4 Composition of Beer Haze2.5 Factors Affecting Haze Formation2.6 The Influence of other Beverage Components on Haze Formation3. A Novel Wort Clarifier and Beer Stabilizer 3.1 Follow-up of Colloidal Stability3.2 Different lag phase lengths 4. Conclusion

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1. IntroductionBeer contains about 4-5% alcohol by volume.Malt is a source for both proteins and polyphenols, whereas hops solely add the latter There are two types of yeast used in brewing: top and bottom fermenters. Ales are made from top fermenting yeast, most commonly Sacchromyces cerevisiaeLager beers are made from bottom fermenting yeasts such as Sacchromyces carlsbergensis

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2. Colloidal stabilization of beerIf a steak is an unappetizing shade of gray, it will seldom be appreciated, even if it’s delicious. It’s the same with beer; a great deal of the perception and appreciation of beer comes from the way it looksColloidal haze does not affect the taste and should not affect beer quality, but: “Most Consumers “drink with their eyes”. They are often more willing to accept a glass of beer which does not taste quite right, over a glass of beer which is hazy”

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Indeed, the brilliance of a beer is probably the most “objective” parameter.

So, most of the consumers will simply reject a beer that is not bright, that is hazy

“The degree to which a beer tastes and looks as good at the end of its shelf life as it did when it was first packaged”

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2.1 The Origin of Beer Particles Hazes can be subdivided into two main groups: biological and non-biological.Biological hazes are caused by infection of beer with wild yeasts or bacteria resulting from poor hygiene and leading to spoiling of the beer. Biological haze is irreversibleThe haze cannot be corrected. The beer should be discarded.

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Non-biological haze is defined as being either “chill” or “permanent” hazeNon-biological or Colloidal haze comprises mostly carbohydrates (starch, dextrin, glycogen, b-glucan), polyphenols-proteins, iron, Ca-oxalate,…,If non biological, the reasons are mostly due to Colloidal Haze formed by polyphenols and proteins interactions

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2.2 Mechanism of Non biological Haze Formation

Interestingly, proline is the only amino acid in wort not consumed by yeast during fermentation since it does not have a permease to allow transport into the cell

Chill haze development, the conversion of flavanols into tannoids

The malt is full of proteins and its husks are full of tannins (polyphenols).

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The driver in haze formation was the oxidation of flavanol oligomers (flavanoids) during beer storageWith further polymerization, larger polyphenol molecules (tannoids) are formed, which are more tightly bound to the haze proteins, giving rise to permanent haze. The tannoids are considered to be intermediates in the oxidation of the flavanols to true tannins.

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Model for protein–polyphenol interaction.

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Simple flavanoids (flavanols) alone are incapable of causing haze; but following oxidation and polymerization, the protein–polyphenol complexes linked by hydrogen bonds produce a chill haze (at 0°C).

The hydrogen bonds are disrupted by warming to room temperature (20°C) and the haze redissolves.

Tannoids are capable of forming additional hydrophobic and ionic interactions with acidic proteins, which are not disrupted by warming to 20°C and result in a permanent haze in the beer

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The model of chill and permanent haze development in

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Haze in beer is a natural phenomenon Biological haze incurred through yeast or bacteria is even easier to manage than colloidal haze. proteins are prized for their enzymatic contribution and their ability to provide body, mouthfeel, and head retention in the finished beer, polyphenols merely impart a perception of astringency.Polyphenols impart certain flavor characteristics and act as natural antioxidants preserving the original taste of beerProteins on their own, or polyphenols on their own, are freely soluble and do not cause a haze.

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The particle size of chill haze is up to about one micrometre

The particle size of a permanent haze is between one and ten micrometres

Chill haze is different than starch haze.

Starch haze should be present regardless of temperature.

Good mashing should prevent it by complete digestion of starch.

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2.3 Factors Affecting Quantity of Cold Trub ProducedThe actual amount cold trub of produced in a given wort depends on numerous factors such as malt modification, mashing program, wort temperature, and the presence of hops or adjunctsWort produced using finely milled malt contains a large quantity of cold trub because the finely ground husks allow greater polyphenol extractionThe extent to which a beer requires colloidal stabilization depends on the raw materials, Process, required shelf life and storage conditions.

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2.4 Composition of Beer HazePolyphenols can be classified into two groups: haze-active and non-haze active polyphenols. They are classified by the number of binding sites per molecule.The hydrophilic molecules tend to be proteins whilst the hydrophobic molecules tend to be tannins.Iron and copper are the metal ions most involved in the formation of metal-containing hazes. This arises from the contact of the mash and the wort with containers made of iron, copper or bronze.

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Oxalate can arise from malt or by simple oxidation of carbohydrates by micro-organisms.

since calcium oxalate separates from beer during fermentation and storage and is the major constituent (50 to 65%) of the beer stone

Tannins may conveniently be divided into three classes. The first class is simple phenols

These compounds principally arise from malt but are also present in small amounts in hops.

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The second class is flavonols which have more complex structures than simple phenols and are principally derived from hops.

The third class consists of anthocyanogens and are important in the formation of polyphenols.

monomeric polyphenols have little effect on haze formation but that dimers and trimers strongly accentuate haze formation

well modified malts tend to form less chill hazes.

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2.5 Factors Affecting Haze Formation

Place of growth also has an effect with maritime barley malts giving better colloidal stability than continental barley malts.Blending different types of malt was not helpful, it was found to be better to use one malt of average modification rather than a blend of well and poorly modified malts.Brews with least mineral additions gave beers with poorest colloidal stability

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CaCl2 and CaSO4 reduce the mash PH. A "haze index" has been defined for hops which is the ratio of polyphenols to alpha acid content.

This ranges from 0.15 to 1.71 with an index less than 0.4 showed good colloidal stability

Use fresh hops, preferably those which have been vacuumed packaged and stored in the dark below 0oC.

Acidifying salts have a beneficial effect on colloidal stability

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2.6 The Influence of Other Beverage Components on Haze Formation The highest sparging temperatures gave the lowest colloidal stability.Avoid use of very weak wort (<1.5°P).Both PVPP & Silicagel have the advantages of being insoluble in water and beer and are classified as process aids

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3. A Novel Wort Clarifier and Beer Stabilizer

Polyclar Brewbrite provides wort clarification and beer stabilization with a single addition to the kettle about 10 min before the end of boiling.A better solid– liquid phase separation in the whirlpool The key objective is to increase the shelf life of the beer and, using this simple procedure, a shelf life of 6 months or more can be achieved without the need for capital investment in the brewery.

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Formation of beer haze

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Summary of the most widely used stabilizing agent for preventing chill and permanent haze development in beer

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Molecular Mechanisms for Haze Formation in Beer

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3.1 Follow-up of Colloidal Stability

Lag phase: No haze increase Increase phase: Linear haze increaseStationary phase: No more haze increase

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Typical curve

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3.2 Different lag phase lengths

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don’t forget the beer after it leaves the brewery!

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4. CONCLUSIONS1. Avoid use of very weak wort (<1.5°P).2. Minimize oxygen pickup throughout the brewing process (<0.1 ppm of dissolved O2 in beer ex-fermenter and into package).3. Cold store, transfer, and filter beer at 0°C or below.4. Wort and beer clarity are important—optimize finings, centrifugation, and filter aid use.

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5. Ensure that the tannoids are removed from fresh beer and polymerized flavanols reduced—use PVPP.6. Balanced stabilization is efficient and cost effective—also use silica gel or a combined stabilizer, such as Polyclar Plus 730.7. Consider beer transport and storage conditions. 45

ACKNOWLEDGMENT It is a pleasure to place on record my gratitude to Gondar University Organic Chemistry teachers especially my advisor Dr.Getachew G/mariam who give me a guide line to prepare and present ,beloved masters Organic chemistry students and my friends; Dereje, Asmamaw,Nesiradin, and Mulalem for their sustained support and encouragement. And at last but not the least, I remain grateful to my wife (Azeb) for constant framework to prepare this seminar.

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