Associate Professor Liu Shao Quan and his PhD student Mr Chua Jian Yong, who have an interest in sustainable food production, took on the project about a year ago. Both are from the Food Science and Technology Program at the NUS Faculty of Science.

“The traditional way of manufacturing tofu produces a large amount of whey, which contains high levels of calcium and unique soya nutrients such as isoflavones and prebiotics. Hence, disposing tofu whey is wasteful,” explains Chua. “Very little research has been done to transform tofu whey into edible food and beverage products. I had previously worked on alcohol fermentation during my undergraduate studies in NUS, so I decided to take up the challenge of producing an alcoholic beverage using the whey. The drink turned out to be tasty, which is a pleasant surprise.”

Tofu, also known as bean curd, is a popular food made from soybeans. One of the most common methods of producing tofu is by curdling freshly boiled soya milk, cooling it, and pressing it into a solid block.

During the pressing process to remove excess water, tofu whey is generated. However, when tofu whey is discarded as an untreated waste, it creates environmental pollution as the protein and soluble sugars in the whey could contribute to oxygen depletion in the waterways. In contrast, upcycling tofu whey can be a means of generating economic returns for businesses.

“The health benefits associated with soy products, coupled with changing preferences towards vegetarian diets, have fueled the growth of tofu production. As a result, the amount of tofu whey has also increased proportionally,” Liu says. “Alcoholic fermentation can serve as an alternative method to convert tofu whey into food products that can be consumed directly. Our unique fermentation technique also serves as a zero-waste solution to the serious issue of tofu whey disposal.”

Under the guidance of Liu, Chua took about three months to come up with a unique recipe to make an alcoholic beverage from tofu whey.

First, he made fresh soya milk from soybeans, and then used the soya milk to make tofu. In the course of making tofu, he collected the whey. Sugar, acid and yeast were added to the tofu whey, and the concoction was fermented to produce the alcoholic beverage.

Chua also designed a novel fermentation technique, which utilizes the tofu whey fully without generating any waste. The whole process of making the alcoholic beverage takes about three weeks.

Altering the composition of tofu whey via biotransformation methods converts its strong beany odor into a fruity, sweet flavor, and extends the shelf life of tofu whey from less than one day to about four months.

In addition, after fermentation, the bound isoflavones that were present in the tofu whey were transformed into free isoflavones that can be absorbed more easily by the human body. The result is a refreshing beverage that is a tad sweet, with fruity and floral notes, and has an alcohol content of about 7 to 8 percent.

The team has filed a patent for the novel process of making Sachi, and they are looking to collaborate with industry partners to introduce the drink to consumers.