Lesson 5 - Beer Haze SAQ

*** Not all hazes in beer are from protein and polyphenol interactions.

              a. Provide three examples of polysaccharide haze and explain what their source is and how to prevent them in the final beer.

              b. You have found that your beer has a non-polysaccharide haze. What would you check for from raw materials through to the finished product tank to identify the

                  root cause?

Response:

Other non-biological forms of haze can develop from raw materials or processing conditions.

a. Examples of polysaccharides that can cause haze include β-glucan and pentosans, which are derived from barley cell walls that have been incompletely modified during the malting process. These hazes can also be a factor when brewing with unmalted grains, such as unmalted wheat, which is part of the standard grist in a Belgian Wheat beer.

When using undermodifed malts or unmalted grains, the brewer needs to ensure the β-glucan and pentosans are sufficiently broken down during the mashing process to prevent these hazes from forming. This can be aided by including a 45 °C mash stand or by the addition of exogenous enzymes, such as β-glucanase.

Care should be taken to avoid shear in brewhouse processing, which can result in β-glucan gels forming.

Mannan haze is exclusively derived from yeast cell walls, caused by poor yeast management or handling, for example, centrifugation. The yeast handling system needs to be designed to avoid shear stress on the yeast cells, with aligned standards and practices implemented in the plant.

Starch haze (a-glucan haze) can occur from incomplete breakdown during mashing as well as retrogradation. Liquefied starch re-gelatinises on cooling, for example, after a prolonged breakdown in the mash conversion vessel.

Good mashing practices, and avoiding any cooling of converted mash, will ensure these hazes do not form. In cases of breakdown in the mash conversion version vessel, starch degrading enzymes can be used in fermenter or maturation vessel.

b. Aside from protein, polyphenol hazes and polysaccharide hazes are the cause of many hazes in beer. Determining root cause involves a systematic problem-solving approach that looks at the process flow, with its constituent inputs and outputs. Other hazes found include:

• Oxalate

• Metals

• Process aids

• Hop products

• Beer freezing

• Collapsed foam

• Filter materials

• Dead bacteria

• Invisible haze

Oxalic acid is present in malt and has a high affinity for calcium, leading to the formation of oxalate crystals that can cause haze in the final beer. To ensure that this does not occur, the brewer needs to add sufficient calcium during mashing and/or wort boiling so that the majority of oxalate is precipitated out in the brewhouse and removed in the spent grain or trub.

Metals are found concentrated in beer haze, and together with the oxygen, they catalyse the formation of permanent haze from chill haze. Iron is often derived from the brewing plant equipment or from the water supply. Analytical checks of the processes and packaged beer should be in place as a preventative measure, along with the routine tasting of waters.

Process aids such as silica gels and PGA foam stabiliser can form hazes. Packaging chain lubricant from conveyers entering bottles or cans will also form hazes and cause flavour taints. To mitigate these events, a well-developed and implemented QA plan with operator work instructions and monitoring should be. Process aids should be made up and used as per the supplier specifications. Samples of made up solutions need to be visually checked for lumps before use.

A high use of isomerised (or reduced isomerised) hop products downstream in the process can lead to higher hazes in unfiltered beers. Correctly executed work instruction along with laboratory checks of dosed beer are essential for problem-free beer.

The freezing point of beer depends on the alcohol content. If beer is physically frozen after filtration, for example, in the bright beer tank or in bottle, sediment can occur. This consists of β-glucans, oxalate, dextrin, and protein. Bits can be seen when the previously frozen beer is dispensed into the glass. To prevent freezing, regular maintenance on chillers, and temperature probe calibration, should occur. Trade outlets should be audited for temperature management.

Filter materials, both powders and particles from the support material, can make their way into the BBT. Sheet material is visible in poured beer as small fibres. In the case of a hazy BBT, the best course of action is to re-filter the beer, although this practice may be negative for both foam and flavour stability. In-line post filter haze measurement followed by BBT haze measurement will prevent hazy beer from being packaged.

Collapsed foam can occur if the bright beer tank (BBT) is purged, for example, to correct high oxygen levels. The foam collapses, leaving the solid residue in the beer. These can often be seen in the BBT outlet sightglass as flakes. It is essential that first-time, the right quality is assured in BBT, so purging is not needed.

Dead bacteria can cause beer haze. These typically are from infection of malt and are not filtered out in the beer filter.

Visually, invisible haze is bright but reads high on 90º scatter. It is caused by very small particles of <0.1 µm.