![]() The lids should not be tightly sealed so as to allow gaseous exchange. The simplest way to store yeast is to mix it with chilled sterile water and store it in 1 – 2 gallon containers with lids in a refrigerator. It is therefore important to decrease the temperature of the yeast, which will be skimmed at about 21☌ to 2° – 4☌ as soon as possible. Yeast will rapidly deteriorate if kept at too high a temperature. The way in which yeast is stored after skimming is of the upmost importance if it is to remain in top condition. The longer the yeast head is kept at ambient temperatures, exposed to air, the greater the possibility of aerial infection.In addition if the yeast head is allowed to remain too long on the beer it may result in yeast off flavours, due to the products of autolysis.This will result in a decrease in yeast cell viability, which could cause, slow, problematic subsequent fermentations. It is possible that autolysis may occur due to overheating from ambient temperatures.If the yeast is allowed to remain on the surface of the beer until the end of fermentation a number of things may occur. The aim when skimming is to remove the yeast head at a point in the fermentation where there is still sufficient activity to keep the head on the surface and to leave just sufficient yeast in suspension to complete the fermentation and form a thin but stable cover over the surface of the beer for protection. If the temperature is too low, the fermentation will be sluggish, resulting in an increased opportunity for infection. In addition to this, and probably more importantly a higher growth temperature will change the yeasts metabolism producing a different range of by products which can have a major effect on flavour. This can have an effect on subsequent conditioning. If the temperature is too high, yeast growth will be too vigorous, producing an excessive demand on nutrients and resulting in beer depleted in these nutrients. This will also affect the rate of growth of the yeast. The yeast crop will not be “healthy” and will die more readily on storage.Poor flocculation, leading to cloudy beer and a poor yeast crop.Oxygen is essential to produce certain fatty substances used in making the yeast cell membrane. Lack of oxygen will have a number of consequences: This growth is affected by the availability of nutrients of which oxygen is crucial. This is important to produce the mass of cells necessary to rapidly convert wort sugars to alcohol. When one looks at the growth curve for yeast during a typical fermentation one sees that there is an initial lag phase, whilst the yeast adjusts to its new environment, followed by a period of rapid growth. One cannot over-emphasise the importance of oxygen. The missing nutrient and in many ways the most important one is Oxygen. A) Yeast NutritionĪ good quality wort will contain all (but one) of the essential nutrients for yeast growth sugars, nitrogen source, vitamins etc. ![]() Yeast Health The factors which affect yeast health are:ĭ) Storage conditions. Yeast is usually “recycled” from brew to brew, the crop from one brew forming the inoculum for the next. ![]() Having chosen your yeast you need to look after it properly – it is a valuable resource! In order to brew good beer it is essential that your yeast is healthy and free from infection. Is sufficiently flocculent to enable it to be easily separated from the beer at the end of the fermentation. ![]() To those commencing brewing the first aspect of good yeast management is the selection of a good yeast. As the means by which wort is converted into beer, yeast is clearly of fundamental importance to brewing.
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