Why is tofu sour when fried

The sourness of tofu when fried is usually related to tofu spoilage or improper frying operations. Fresh tofu should have a bean aroma after being fried at high temperatures, and the sour taste may be caused by improper storage environment, expired tofu, low oil temperature, repeated use of oil, or abnormal fermentation process.

1. Tofu deterioration

Tofu has a high protein content and sufficient moisture. Storing it at room temperature for more than 4 hours can easily breed bacteria and lead to spoilage. When purchasing, it is necessary to observe whether the tofu is sticky or has an odor, and it should not be stored in refrigeration for more than 2 days. If the surface is found to be slippery or emits a sour odor before use, it indicates that it has deteriorated and is not edible.

2. Improper oil temperature control

When frying, it is necessary to maintain the oil temperature at 160-180 degrees Celsius. insufficient temperature can cause tofu to absorb oil and accelerate spoilage. Chopsticks can be used to test the oil temperature, and inserting them into the oil and emitting fine bubbles is the appropriate temperature. Low temperature frying will result in insufficient protective film on the outer layer of tofu, causing internal water to seep out and undergo hydrolysis reactions with oil, producing free fatty acids.

3. Oil oxidation and rancidity

Edible oil that is repeatedly used will undergo oxidative polymerization reactions, producing acidic substances such as aldehydes and ketones. It is recommended to filter the residue after each frying, and use the same batch of oil no more than 3 times. Fried seafood or meat oil is more prone to spoilage and should not be used for light ingredients such as fried tofu.

4. Fermentation process issues

In traditional brine tofu production, if the ratio of gypsum or brine is imbalanced when pouring the sauce, it will result in excessive residual lactic acid bacteria in the tofu. This tofu has a slightly sour taste before deep frying, and the acidity becomes more pronounced after high-temperature cooking. When making a purchase, priority should be given to tofu with a tight texture and smooth cut surface.

5. The influence of ingredient pairing

Some dishes intentionally add acidic seasonings such as tomatoes and lemon juice to create flavor. If the seasoned tofu is mistakenly fried twice, the sour taste will be enhanced. Suggest arranging the seasoning process after deep frying or using sweet and sour sauce to balance the taste.

It is recommended to use tender tofu or northern tofu produced on the same day for daily cooking, and use them as soon as possible after opening. Before frying, soak in salt water for 10 minutes to enhance toughness. After draining the water, put it in batches to avoid sudden drops in oil temperature. Paired with perilla leaves, salt and pepper, etc., it can neutralize the greasy feeling. If there is a persistent abnormal sour taste, it is necessary to check the freshness of the ingredients and the hygiene of the oil used. When storing fried tofu, it should be cooled and sealed for refrigeration. When reheating, using an oven instead of a microwave can maintain a crispy texture.