Soy Milk Production Line Guide: Process Steps and Yields

Key takeaways

• A standard 1:7 bean-to-water ratio yields roughly 8–9 kg of soy milk per kg of dry soybeans at about 7–8 °Brix.
• Plain soy milk typically contains about 3–3.5 g protein per 100 g, comparable to cow's milk.
• Heat treatment must inactivate trypsin inhibitors: about 90% are inactivated in 62 s at 143 °C or 29 s at 154 °C.
• Beany flavour comes from lipoxygenase; hot grinding, rapid heating and vacuum deodorization keep it under control.

How is soy milk produced industrially?

Industrial soy milk is made by cleaning and soaking soybeans, wet-grinding them with hot water, separating the insoluble fibre (okara), cooking the raw milk to inactivate enzymes and anti-nutrients, deodorizing under vacuum, blending, homogenizing, then pasteurizing or UHT-treating and filling. A typical ratio of 1 kg beans to 7 kg water gives roughly 8–9 kg of soy milk.

The same line concept, with different front-end steps, also produces almond, oat and coconut drinks. This guide focuses on soy, the most process-intensive of the common plant-based milks, and gives the numbers needed to plan capacity.

What are the steps in a soy milk production line?

The core sequence is cleaning and dehulling, soaking, hot wet grinding, okara separation, cooking, vacuum deodorization, formulation, homogenization, heat treatment and filling. Grinding and cooking decide flavour; okara separation decides yield.

1. Cleaning and dehulling: remove stones, dust and damaged beans; optional dry dehulling reduces fibre, colour and off-flavour.
2. Soaking: beans are typically soaked overnight in clean water, which hydrates and softens them for grinding. Continuous lines use soaking tanks with water circulation and temperature control to shorten the time.
3. Grinding: soaked beans are wet-ground with water, often hot, in one or two stages (coarse then fine mill) to release protein and oil.
4. Okara separation: a decanter centrifuge, screw press or vibrating screen separates the soy milk from okara, the wet fibrous residue.
5. Cooking: heat the raw soy milk, for example about 98 °C for 5 minutes in pilot practice, or by steam injection, to inactivate trypsin inhibitors and improve flavour.
6. Deodorization: a vacuum deaerator or flash vessel removes volatile beany compounds and dissolved air.
7. Formulation: add sugar, salt, stabilizers, flavours, calcium and vitamins in a mixing tank.
8. Homogenization: two-stage high-pressure homogenization stabilizes oil droplets and gives a smooth, milk-like mouthfeel.
9. Heat treatment and filling: pasteurize for chilled distribution, or UHT-treat and fill aseptically for ambient shelf life.

What yield can you expect per kilogram of soybeans?

At a 1:7 bean-to-water ratio, expect about 8–9 kg of soy milk per kg of dry soybeans at roughly 7–8 °Brix. The Northern Crops Institute pilot plant, for example, expects 16–18 kg of soy milk from 2 kg of beans ground with 14 litres of water.

Typical soy milk process figures

Parameter	Typical value	Source / note
Bean-to-water ratio	1:7 (standardized pilot method)	Northern Crops Institute
Soy milk yield	About 8–9 kg per kg dry beans	16–18 kg from 2 kg beans
Soluble solids	About 7–8 °Brix	Before formulation and dilution
Protein in soy milk	About 3–3.5 g per 100 g	NIFTEM processing guide
Cooking	About 98 °C for 5 minutes (pilot practice)	Industrial lines often use steam injection
Trypsin inhibitor reduction to 10% residual	62 s at 143 °C; 29 s at 154 °C	Liang, Kwok and Niranjan (2002)

Higher water ratios raise volume but dilute protein and solids; lower ratios give richer milk but lose more solids in the okara. Many producers grind at a lower ratio for efficient extraction and then standardize to the target brix and protein after separation.

Choosing okara separation equipment

Separation efficiency has a direct effect on yield, because every kilogram of liquid left in the okara carries dissolved protein and sugar with it. Small plants often use a screw press or vibrating screen, which are simple and inexpensive. Larger continuous lines typically use a horizontal decanter centrifuge, which produces drier okara, recovers more soluble solids and runs with less manual cleaning. Some lines add a second extraction, re-mixing the okara with water and separating again, to recover additional solids.

Converting bean intake to line capacity

Line capacity follows directly from yield. A plant processing 1 tonne of dry beans per day at 8.5 kg milk per kg produces about 8,500 kg of base soy milk. Over 16 effective hours, that is about 530 kg/h, so a 600–1,000 L/h homogenizer and heat-treatment unit leaves room for dilution, added ingredients and growth.

How do you control beany flavour in soy milk?

Beany flavour forms when the enzyme lipoxygenase oxidizes soybean oil as soon as beans are crushed in the presence of water and oxygen. Control it by inactivating the enzyme before or during grinding with hot water or steam, minimizing air contact, and removing volatile compounds by vacuum deodorization.

• Hot grinding or blanching: India's NIFTEM processing guide describes soaking beans briefly in hot water at 70 °C before grinding, and notes that grinding soy into water at 80 °C forms a slurry without generating off-flavour compounds.
• Bean pre-treatment: a 2019 study in the Journal of Food Science and Technology reduced lipoxygenase activity by about 66% by treating beans with superheated steam at about 120 °C for 9.5 minutes before soaking.
• Deaerated water and closed grinding: less oxygen means less oxidation.
• Vacuum deodorization: flashing hot soy milk into a vacuum vessel strips residual volatiles.

Should soy milk be pasteurized or UHT-treated?

Pasteurized soy milk must be refrigerated and suits local distribution, while UHT treatment, in the same 135–150 °C range used for long-life dairy, with aseptic filling gives months of ambient shelf life. Either way, total heat load must also inactivate trypsin inhibitors for good protein digestibility.

Pasteurized versus UHT soy milk

Factor	Pasteurized	UHT + aseptic
Storage	Chilled	Ambient
Shelf life	Days to a few weeks	Several months
Packaging	Bottles, pouches, gable-top cartons	Aseptic cartons, PET with aseptic filler
Capital cost	Lower	Higher
Market reach	Local / regional	National and export

Research by Liang, Kwok and Niranjan modelled trypsin inhibitor inactivation in soy milk between 121 and 154 °C and found that 90% inactivation took 62 seconds at 143 °C and 29 seconds at 154 °C. This is why soy lines often combine an earlier cooking step with the final UHT treatment rather than relying on a few seconds at UHT temperature alone.

How do almond, oat and coconut lines differ?

Almond and other nut milks skip the long cooking step but need blanching, fine grinding and efficient separation; oat drinks add enzymatic hydrolysis to break down starch; coconut milk starts from grated kernel and requires careful fat emulsification. Homogenization, heat treatment, filling and CIP stay largely the same.

Because the back end is shared, one well-designed line can switch between bases if the front-end modules are planned from the start.

What should you specify when buying a soy milk line?

• Daily dry-bean intake and target product brix and protein.
• Grinding method (hot or cold, one or two stages) and okara separation equipment.
• Cooking and deodorization method and the total heat load for trypsin inhibitor control.
• Homogenizer pressure and capacity, matched to the heat-treatment unit.
• Pasteurized or UHT product, and the filler format.
• Okara handling: storage, drying or sale as feed or food ingredient.
• CIP coverage, since soy protein fouls heated surfaces quickly.

When we engineer a plant-based milk line, we size every module from the bean intake and the target protein, then leave room for an almond or oat front end. Send us your daily volume and product idea, and our engineers can propose a process flow and equipment list.

Frequently asked questions

Sources

1. Northern Crops Institute / USSEC – Soymilk and Tofu Quality Analysis
2. NIFTEM – Processing of Soya Milk (PMFME)
3. Liang, Kwok & Niranjan (2002) Mathematical modelling of the heat inactivation of trypsin inhibitors in soymilk at 121–154 °C, J. Sci. Food Agric.
4. Chong et al. (2019) Thermal inactivation of lipoxygenase in soya bean using superheated steam, J. Food Sci. Technol.
5. Tetra Pak Dairy Processing Handbook – Long-life dairy products