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Factors affecting yeast fermentation

2017-05-27

1) Temperature
◆ Yeast is active at 0 ℃ -55 ℃, and gradually lose activity as temperature goes up
◆ Suitable temperature range for yeast multiplication is between 22 ℃ and 28 ℃ which is the required temperature of the dough.
◆ Suitable temperature range for dough fermentation and gas production is between 32 ℃ and 38 ℃ which is the required temperature in the prover.
◆ Yeast growth slows significantly when temperature is below 20 ℃ or above 40 ℃.
◆ When dough temperature exceeded 30 ℃, gas production speeds, but the total gas production reduces, and this affects yeast quality (fermentation not durable).

2) PH values and water quality
◆ Yeast grows best under weakly acidic conditions. Keep the PH value of the dough between 4 and 6 during operation. PH value is mostly decided by water quality.
◆ Using rigid water with more mineral content reduces the solubility of protein, hardens and toughens the dough, inhibits yeast fermentation, and the products comes in thick dough skin and rough texture.

3) Osmotic pressure
◆ Proper amount of sugar promotes yeast fermentation to produce carbon dioxide gas. But excessive content of sugar or salt (if sugar, salt and yeast diluted in water at the same time) damages the cell membrane of yeast, reduces fermentation rate, and inhibits multiplication of the yeast.
◆ Yeast can still survive and drive fermentation, and dry yeast is more adapted to high concentration environment than fresh yeast..

4) Other factors affecting yeast fermentation
◆ Alum, alkali, preservatives using, excessive or untimely fat adding affects the multiplication of the yeast.
◆ Instant dry yeast dissolves fast and is highly active, but it is oxygen sensitive and loses ferment ability once oxygen level reaches 0.5%. That’s why this type of yeast comes in foil vacuum packaging. And unused part after opening needs to be sealed and used as soon as possible.