Grilled, baked, roasted or fried, sweet, sour or pickled, silken, soft, firm or extra-firm, tofu can be prepared in dozens of ways. In fact the soybean – which is what tofu is made from – has an excellent balance of fat, protein, carbohydrates, vitamins and minerals.
It’s used as a meat substitute, a base for desserts, shakes, dips and sauces. It’s also used extensively in vegetarian and vegan diets. Here we’ll give you a short history of tofu and we’ll answer the question ‘how do they make tofu?’
A Short History of Tofu
The history of tofu dates back to ancient times, meaning its true origins are largely left to myth and legend.
One such story states that tofu was created accidentally around two thousand years ago during the reign of Han dynasty prince Liu An, and quite possibly by the prince himself. During the drying, pureeing and cooking of soybeans, one fable tells that he added salt which not only added flavour to his mash, but also acted as a solidifier and formed curds. Another story suggests that the process of how tofu is made came to China from neighbours such as the Mongols or the East Indians.
Around the eighth century AD, Chinese Buddhist monks introduced the soya plant to Korea and Japan. At this time it was almost exclusively eaten in China, Japan, Korea, Singapore, Vietnam, Thailand and the surrounding regions until the soy plant was brought to the USA by immigrants in the mid-nineteenth century.
By the 1950s Asia and the USA split the global soybean market roughly down the middle. However, within four decades, America became the world’s largest producer with a market share of around 65%. This is thanks in part to an increasingly health-aware population and a rise in vegetarianism and veganism.
Let’s get down to business and answer the question ‘how is tofu produced in a factory?’
How is Tofu Produced?
The recipe for tofu is incredibly simple. All you need are soybeans, water and a coagulant. Indeed the process of how tofu is made is essentially a mechanical version of the ancient method. As well as manufacturing plants that process tofu by the tonne, there are still smaller artisan producers who might make a few kilograms each day. Regardless of the size, the process of how tofu is produced usually follows the same basic steps.
Dried soybeans arrive at the processing plant in huge sacks. They’re emptied into a vat and soaked for up to 14 hours. During the soaking the beans will double in size due to the amount of water they absorb.
Mashing & Extracting
The beans are mashed into a pulp either with traditional stone grinders from Japan or using modern machinery. The resulting slurry is boiled for between 3 – 10 minutes to neutralise a specific enzyme that is thought to hinder digestion.
Once the beans have been mashed, they’re run through a roller press to separate the milk from the pulp – usually the hulls, fibre, protein and starch – known in Japanese as okara. The pulp is then used for a variety of purposes including as feed for livestock, as an ingredient in vegetarian burgers and even in the manufacture of ice-cream.
There are a few more stages to go before we finish answering the question ‘how do they make tofu’ and the next part of the process is perhaps the most important.
The pure soy milk is then pumped into vats to be solidified. In exactly the same way milk is curdled to make cheese, soy milk must be curdled to make tofu. Curds are made by separating the solid parts (curds) from the liquid parts (whey).
Coagulation – also known as clotting which turns liquids into solids – is done by the addition of a coagulant. Traditionally, the process of how tofu is produced in a factory is with the addition of nigari, the left-over salts after sea water has been filtrated and evaporated, but coagulation can also occur by using acids and enzymes. The most commonly used salt coagulant is calcium sulphate, otherwise known as gypsum. The coagulant alters the pH balance of the liquid and curds the milk.
Next, the curds are pressed into blocks using traditional hand-turned screw or lever presses, or for factories making tofu in large-volume batches, they use centrifuges or hydraulic presses. The pressing drains off the whey and the blocks are then cut into half-kilo pieces.
The tofu is then cleaned and stored where it becomes firmer and waits until it’s ready to be packaged. This almost answers the question ‘how is tofu manufactured’.
One the tofu is ready, it’s packed into shrink-wrapped blocks or tubs and weighed, sealed and dated. Depending on the type of tofu being made, some companies add water to the packaging for a silkier, set custard-like texture. The tofu is then heated to a temperature of around 80°C which gives it a longer shelf-life – a process known as pasteurisation – and it’s then ready to be boxed and shipped out. And that’s the final step in the process of how tofu is made.