Compressed Baker's Yeast: Mapping Patents on Post-Fermentation Processes.

In the baking industry, fresh yeast is generally available as a compressed paste containing about 70% moisture. While much literature has been published on its growth conditions in fermentation tanks, little information may be obtained on the final steps of baker's yeast production. In this review, 226 patents were found on the separation of yeast cells from spent growth media as well as its dewatering, forming, and packaging in the compressed form. The latter corresponded to 21% of 1096 unique families of patented inventions filed worldwide between 1787 and 2014 on the production of fresh baker's yeast. Patent specifications disclosed key technical information not available in scientific journals. Particularly between 1890 and 1960, highly specific equipment such as centrifugal separators, rotary vacuum filters, and extruding and cutting units were proposed. Compressed yeast may contain small amounts of processing aids, including water-absorbing agents such as starch and salt, as well as plasticizing and whitening agents. Any variation in yeast solids and moisture contents will affect its gassing power and keeping properties. Disposal and proper treatment of very large volumes of spent growth media will remain a major challenge to the baker's yeast industry.