Fresh yeast is more capricious than dry yeast, as it consists of living organisms. They should be kept in a cool place where the temperature does not exceed 10 degrees. Moreover, such a product must be carefully packaged, but the wrapper itself must be “breathable”. The shelf life of live yeast, if stored properly, is no more than 6 weeks. They are 2/3 water and provide the fastest and most intense fermentation.
High-quality live yeast has a uniform grey-beige colour. Inconsistency, they resemble elastic plasticine. If you press on them, they will neither smear nor crumble. Such yeast is commercially available in a compressed form. They are similar to a bar, weighing 100 g.
When preparing the dough, a pack of yeast is finely crumbled and diluted with a litre of warm milk (water). The liquid temperature mustn’t be higher than 40 degrees; otherwise, living organisms will die, and, as a result, the dough will not work.
Compressed yeast is, in essence, cream yeast with most of the liquid removed. It is a soft solid, beige in colour, and best known in the consumer form as small, foil-wrapped cubes of cake yeast. It is also available in a larger-block form for bulk usage.[19] It is highly perishable; though formerly widely available for the consumer market, it has become less common in supermarkets in some countries due to its poor keeping properties, having been superseded in some such markets by active dry and instant yeast. It is still widely available for commercial use and is somewhat more tolerant of low temperatures than other forms of commercial yeast; however, even there, instant yeast has made significant market inroads. Wikipedia
