Protected active dried yeast

More modern forms of dried yeast are now available, known as instant active dried yeast (IADY) and protected active dried yeast (PADY). These types of yeast can be mixed directly into dry ingredients, making them more effective at gas production than ADY. 

Instant Active Dry Yeast. Instant ADY (lADY or HADY) production is similar to ADY production but requires a different strain of yeast. After pressing, the yeast is extmded into noodles 0.2—0.5 mm in diameter and 1—2 cm long and deposited on a metal screen or perforated plate in a fluid-bed air dryer. Drying time is shorter than with ADY, about 1—2 hours in practice, with a final moisture level of 4—6%. Instant active dry yeast does not require separate rehydration. It is always packaged in a protective atmosphere or under vacuum. On an equivalent soHds basis, the activity of lADY is greater than that of regular ADY, but stiU less than that of compressed yeast. 

As is shown by the MIC in Table 88., dithio-2,2 -bis(benzmethylamide) s spectrum of effectiveness covers in particular fungi, but yeasts and bacteria, too. This and the solubility properties of the microbicide make it suitable for anti-fungal protection of dry films (paints, adhesives, sealants) and for wet state preservation applications. The addition rates of a formulation containing 25% a. i. move between 0.05-0.20% for the in-can/in-tank preservation of aqueous products and 0.5-2.0% for dry film applications. The agent is active over pH range 4-12. 

Setting Up Dissolve 40 g of sucrose and 0.25 g of disodium hydrogen phosphate, which buffers the mixture to maintain an optimal pH. in 75 mL of warm (40 °C) tap water contained in an Erlenmeyer flask. Add a stirbar and one packet (8 g) of dry. active baker s yeast, and assemble the apparatus for anaerobic fermentation shown in Figure 17.15. The 3% barium hydroxide solution should be protected from atmospheric carbon dioxide by a layer of mineral oil. A precipitate of barium carbonate will form as carbon dioxide is produced during the course of the fermentation. Stir the mixture vigorously tor about 1 h in a warm location to suspend all of the yeast and to initiate the fermentation. 

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