Soybean milk boils at only 93°C
Soybean milk is a popular breakfast choice for many families, and some people even buy soybeans to make it at home using a juicer or a high-speed blender. However, a netizen has reminded everyone that homemade soybean milk can experience a "false boil" during heating, and consuming it at this stage can easily lead to food poisoning. So, how can you drink soybean milk safely?
Homemade soybean milk boils at 90°C
A false boil in homemade soybean milk? Recently, this post went viral on social media, claiming that soybean milk made with a soy milk machine starts to boil at around 90°C, but is not yet fully cooked. This phenomenon is called a "false boil." The media has also reported that last January, more than 10 employees at a shoe factory in Guangdong experienced vomiting and abdominal pain, and hospital tests confirmed they had suffered food poisoning from drinking incompletely cooked soybean milk.
It is understood that the most harmful substance in a false-boiled soybean milk is trypsin inhibitor. When the false boil occurs, its inactivation rate is only 40%. This substance is only completely harmless when its inactivation rate reaches 100%.
Can homemade soybean milk really have a false boil? The Evening News Laboratory prepared a thermometer and soybeans, then made a batch of pure soybean milk.
When the soybean milk was first placed in the pot, the thermometer showed 25°C. The heat was then kept at a medium-low flame. Soon, the temperature rose from 25°C to 60°C, at which time small bubbles appeared around the edge of the pot. As the temperature gradually increased, the soybean milk began to churn at around 85°C. When the temperature reached 90°C, the entire pot of soybean milk came to a boil.
At this point, many people would think the soybean milk was cooked. However, we found from the thermometer's display that the soybean milk had not yet reached 100°C.
For comparison, we prepared another batch of fruit soybean milk, made from soybeans and banana slices, and conducted the same experiment. After heating it, its changes were basically the same as the pure soybean milk; it began to boil when the temperature reached around 90°C.
Boil the soybean milk for another 5 minutes after it boils
The experiment confirms that a false boil does indeed occur when heating homemade soybean milk. So, what is the reason for this, and how should we safely make and drink soybean milk?
Professor Liu Shaowei, a food science expert from East China University of Science and Technology, explained that the false boil is caused by saponins in the soybeans. It is the saponins that create the bubbles when heated, not the soybean milk being cooked. Additionally, soybean milk contains a substance called saponin, which expands when heated to around 80°C, floats to the surface of the soybean milk to form white bubbles, and looks like the pot is boiling, creating a misconception.
In reality, when homemade soybean milk is not fully cooked, it contains residual saponins, trypsin inhibitors, and other substances, all of which are toxic. The inactivation rate of trypsin inhibitor must reach 100%. "The so-called inactivation rate is to ensure that these substances do not function in the human body," Professor Liu said. However, the false-boiled soybean milk does not meet this requirement. Drinking it can paralyze a person's nerves, leading to a toxic reaction.
So, how exactly can you safely make and drink soybean milk? Professor Liu recommends that homemade soybean milk should be boiled for about 5 minutes after it starts to boil.