In terms of safety, a pH meter is used as a monitoring device for microbiological control.
The propagation and metabolism of microorganisms are influenced by factors such as nutrients, moisture, temperature, and pH.
The pH in particular plays an important role in quality preservation of food products, and pH modifier food additives (citric acid, trisodium citrate, etc.) are widely used.
There is an optimum pH level for breeding microorganisms, and the boundaries on the acidic and alkaline sides of the range where breeding is possible are different for each type of microorganism. Outside of the optimum pH range, propagation of the microorganism is inhibited.
Under the Hazard Analysis and Critical Control Points (HACCP), there are many foods with temperature, water activity, and pH as the 3 major points to monitor.
pH meters are also used for management of the fermentation process.
Whether fermentation is well promoted depends on how the normal activities of the fermentation microorganisms are manipulated.
●Bread
The water absorption of the flour and the hardness and pH of the water affect the flavor, and the water used in the dough should be a pH of between 6 and 7. When the water and flour react to one another, the lactic acid bacteria is activated and generates lactic acid, lowering the pH.
Many people agree that baked bread is the most delicious when it has a pH of around 5.
People who make bread using homemade yeast might also measure the pH of the yeast and the dough.
For example, with natural yeast, the pH must be measured when making yeast for rye sourdough or raisin bread, and the pH is usually between 3.5 and 4.5.
●Cheese
Cheese is fermented by adding starter cultures (lactic acid bacteria) to milk (pH of approximately 6.7). The lactic acid bacteria breaks up the lactose in the milk and creates lactic acid, which lowers the pH, and it also assists the rennet (enzymes that curdle the milk) in the curdling process. After the pH decreases, measuring the pH or acidity of the lactic acid is an important reference for deciding when to add the rennet. The proper pH level for adding rennet is different for different varieties of cheese: for hard cheeses, pH 5.5; for mozzarella, pH 6.5; and for camembert, pH 6.5 or lower.
●'Miso' (fermented soybean paste)
Miso is fermented by mixing 'koji' mold (Aspergillus oryzae) with the raw materials of rice, wheat, and soybeans. Through this fermentation process amino acid, vitamins, various organic acids, and lactic acid bacteria are produced, and the pH decreases due to the activities of the lactic acid bacteria.
Properly fermented miso usually has a pH of between 4.9 and 5.1.
●Soy Sauce
Just like with miso, the pH of soy sauce decreases due to the activities of the lactic acid bacteria. Soy sauce should have a pH of between 4.7 and 5.0.
● Beer
The pH level of beer during its preparation affects the quality and taste of the finished product.
During preparation, the mash (mixture of malt and hot water) should have a pH of between 5.2 and 5.6.
Managing the pH of mash is important, because a pH of higher than 5.6 can allow the enzymes to act in a way that has a harmful effect on the beer or can make it easier for tannin to form, which can cause bitterness or an unpleasant taste. A pH level of 5.0 or less can cause the malt to deteriorate or decompose.
Reference values
●'Sake' (Japanese rice wine)
The standard for the pH level of water used in the fermentation process for washing the rice and other preparations is neutral or slightly alkaline.
The final product sold in stores has a pH of between 4.2 and 4.7.
●Wine
In winemaking, keeping the pH low leads to a good product.
A pH of between 3.0 and 3.5 is suitable for wine, because a pH higher than 3.5 affects the quality of the wine by causing oxidation to progress, the color tone to become brown, and bacteria to increase.
By adding sulfite in the early stages of grape juice fermentation, the pH is kept on the acidic side and fermentation proceeds smoothly. In wine production, Brix and temperature are very important indexes, and measurement and control of pH are the keys to good winemaking.
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