Active Dry Yeast: Lessons from Patents and Science.

In the production of fermented foods, long-term preservation of the activity of microbial starters is a critical issue. The aim of this review was to determine key challenges in the production and use of active dry yeast over time and to compare statistics on letters patent for inventions and applied scientific articles as indicators of technological evolution. The review covers 280 original patent specifications and 212 applied scientific articles issued between 1796 and 2018, not including documents in basic science or without obvious application in fermented foods. The main subject matter was baking and the other entries applied to wine and, to a lesser extent, beer and spirits. Very popular in patents granted in the 19th century until about 1935 but ignored in the scientific literature, dehydrated yeast preparations often consisted of wet biomass concentrates mixed with large amounts of water-absorbing agents. Long-term survival of dehydrated yeast cells progressively improved with specific strains, growth conditions, and, to a lesser extent, drying conditions. Since the 1990s, both inventors and scientists have mainly targeted yeast cells protection during rehydration, a most critical factor. Proper review of the scientific literature would be incomplete unless it includes patents, a much ignored but relevant source of information.