Instant dry yeast is a dry yeast product that maintains strong fermentation ability after being pressed, dried and dehydrated from specially cultured fresh yeast. The pressed yeast is squeezed into thin strips or small balls, and the low-humidity circulating air is used to continuously dry through the fluidized bed, so that the final fermentation moisture reaches about 8%, and the fermentation ability of the yeast is maintained.
Take active dry yeast for bread, for example.
New methods and processes for bread active dry yeast:
1. Slant culture: Preparation method of wort culture medium, use 1000 ml of Baume 7-8 degree wort, 1 gram of glucose and 2 grams of agar, boil and put the dissolved content into a test tube, use 1.1kg/cm2, sterilize Incubate for 30 minutes, then set aside.
On the purification workbench, insert the yeast strain using aseptic methods, place it at 28-30°C, and culture it for 48 hours.
2. Liquid seed culture in an Erlenmeyer flask: Put 250 ml Erlenmeyer flask with 7-8°C Baume sugar water, each bottle only contains 100 ml, sterilize it with 1.1kg/cm2 for 30 minutes, cool it to below 30℃, and use In the bacterial operation method, insert 2 to 3 needles of the slant bacterial strain, culture it below 28 to 30°C for 14 to 16 hours, and wait until a large amount of foam is generated in the bottle.
3. Liquid seed expansion culture: The liquid seed expansion culture in the Erlenmeyer flask becomes the liquid expansion strain. For every 1000 ml of sterilized Baume 7-8 degree mucilage water, 10% of the liquid seed in the Erlenmeyer flask is added. Cultivate at 28-30°C for 10-12 hours to initiate, then expand to a seed tank and cultivate for 8-10 hours.
4. Liquid fermentation in the fermentation tank: Sterilize the mussel water, wort juice, and rice koji juice at 7 to 8 degrees in Baume with 1.1kg/cm2 for 20 minutes. The fermentation tank is only filled to a depth of 40cm, and the liquid bacteria are inserted. The inoculation amount is 10% of the culture medium, the room temperature is maintained at 28-30°C, filtered air is slowly introduced into the room, and the culture is completed after 12 hours. (Both the culture room and fermentation tank should be disinfected before use).
5. Separate the yeast cells from the fermentation liquid: Send the cultured yeast liquid into a sedimentation centrifuge (speed 2000 ~ 4000 rpm; after centrifugation for 5 minutes, remove the supernatant, leaving the bacterial sediment .
6. Adsorption and solid culture fermentation, adsorbent solid culture medium: 85% soluble starch, 14% flour, 1% glucose, mix well, bake at 40°C for 2 hours and set aside.
To the sediment left after centrifugation, add sterilized mussel syrup, wort juice, and rice koji juice at a ratio of 1:1. After mixing, mix the mixed liquid into the baked adsorbent solid culture medium. The ratio of the mixed liquid to the solid material is 1.2:1, and then put it into sterilized curved plates with a thickness of 3cm. Incubate in the koji chamber at 30°C for 8 hours.
7. Shaping and drying: pass the solid fermented fermentation material through a 20-mesh sieve to form, then spread it thinly, and dry it at 40°C within 10 hours to get the finished product.
FAQ
What is the primary raw material used to feed yeast during the industrial fermentation stage, and why?
Molasses (usually derived from sugar cane or sugar beets) is the primary raw material used as the carbon and energy source. It is selected because it is rich in readily fermentable sugars (like sucrose, glucose, and fructose) and naturally contains essential minerals, vitamins (especially biotin), and organic acids that promote rapid, healthy yeast cell division. Before being fed to the yeast, the molasses is clarified, sterilized, and supplemented with nitrogen (such as ammonia or urea) and phosphorus to create the perfect nutrient broth.
How does the manufacturing process differ between Active Dry Yeast (ADY) and Instant Dry Yeast (IDY) during the drying phase?
The main difference lies in the drying speed, final moisture content, and the resulting cellular structure:
Active Dry Yeast (ADY): Dried relatively slowly in fluidized bed dryers to a moisture content of about 7–8%. This slower process allows the yeast cells to form a thick, protective outer shell of dead yeast cells. This shell protects the live core but requires the yeast to be rehydrated (“proofed”) in warm water before baking to wake the cells up.
Instant Dry Yeast (IDY): Dried much faster using advanced fluidization techniques down to a lower moisture content of roughly 5–6%. The rapid drying creates highly porous, smaller granules that absorb moisture instantly. Because it lacks the hard protective shell of ADY, it can be mixed directly with dry ingredients without prior rehydration.
