Why should you not freeze soya milk?
Soya milk, also known as soy milk, is a popular dairy-free milk alternative made from soaked and ground soybeans. It has a creamy, nutty flavor and can be used in many of the same ways as cow’s milk. However, there is an important reason why you should not freeze leftover soya milk.
Soya Milk Composition
To understand why freezing affects soya milk, it’s helpful to first look at what it’s made of. The main ingredients in soya milk are:
- Water – Making up about 90% of the milk.
- Soybeans – Usually whole beans that are soaked, blended, and strained.
- Sugar – Typically added to sweeten the naturally beany flavor.
- Salt – For flavor.
- Emulsifiers – Like lecithin to keep the proteins from separating.
- Vitamins and Minerals – Often added to fortify the milk.
The key components when it comes to freezing are the water and the soy proteins. The abundance of water makes soya milk prone to changes in texture when frozen. The proteins can be irreversibly altered by freezing as well.
Effect of Freezing on Texture
When you freeze soya milk, the first thing you’ll notice after thawing is a change in texture. The abundant water content means large ice crystals form during freezing. This damages the protein networks suspended throughout the milk, leading to graininess and separation after thawing.
Researchers have found that storing soya milk at freezing temperatures for even 7 days significantly changes the viscosity and visual properties. Softy and foaminess are reduced as the proteins lose stability. Some studies found these textural changes continued to progress during subsequent refrigerator storage as well.
| Storage Temperature | Texture Changes |
|---|---|
| -18°C (0°F) – 7 days | Increased separation, wateriness, loss of softness, decreased foam stability |
| 4°C (39°F) – 7 days | Minimal changes to texture |
This table shows how quickly freezing temperatures can damage the delicate protein networks in soya milk that give it a silky, creamy texture. Refrigeration preserves the texture much better.
Effect of Freezing on Proteins
In addition to physical changes, freezing also causes chemical changes in the soy proteins. The proteins start to unfold or denature as ice crystals form between them. These proteins include glycinin and beta-conglycinin.
Research has found irreversible changes to the tertiary structure of these proteins when frozen between -18°C and -80°C (-0°F and -112°F). The denaturation worsens as the storage time lengthens. This can result in an undesirable chalky texture.
The denatured proteins are also more likely to integrate with each other when thawed. This leads to an undesirable coagulation and gritty precipitates in the milk.
Effect of Freezing on Flavor
In addition to texture and protein changes, freezing and thawing soya milk also affects the flavor. As the proteins denature, they can interact with lipids in the soya milk leading to oxidation.
This causes an unpleasant grassy, beany flavor to develop. Some describe it as a burnt plastic taste. The original sweet, creamy flavor of the milk is lost.
| Storage Condition | Flavor Changes |
|---|---|
| Frozen for 2 months | Strong beany, grassy off-flavors |
| Refrigerated for 1 week | No significant flavor changes |
This table demonstrates how freezing soya milk causes development of undesirable flavors over time, while refrigeration maintains the original flavor.
Nutrient Loss
Finally, freezing and thawing can degrade some of the nutrients originally found in soya milk. Vitamin C and B vitamins are especially prone to destruction from freezing.
One study found losses of 25-36% of vitamin B2 and B12 after repeatedly freezing and thawing soya milk. Other water-soluble vitamins like C, B1, and B6 also declined but to a lesser extent. Fat-soluble vitamins like A, D, E, and K were more stable.
Minerals like calcium, iron, and zinc are better retained during freezing. However, the ability to absorb these minerals may decrease as the proteins they are attached to denature.
| Nutrient | Freezing Loss After 6 Months |
|---|---|
| Vitamin C | 35% |
| Vitamin B1 | 10% |
| Vitamin A | 5% |
| Calcium | No significant loss |
This table displays how water-soluble vitamins like C and B1 are lost in higher amounts than fat-soluble vitamins like A when soya milk is frozen for an extended period.
Best Storage Practices
To avoid the undesirable changes that come with freezing soya milk, it’s best to use proper storage practices:
- Purchase small containers and use within 3-4 days.
- Store opened soya milk in the refrigerator and use within 7 days.
- Keep refrigerated soya milk towards the front to ensure it gets used.
- Transfer to an airtight container if not finishing the package.
- Never freeze opened cartons of soya milk.
- Avoid storing soya milk for extended periods even in the refrigerator.
Following these tips will help you enjoy the best texture and flavor from your soya milk.
The Bottom Line
Freezing soya milk causes undesirable changes including:
- Grainy, separated texture
- Unpleasant flavors like beany, grassy, oxidized
- Irreversible protein denaturation
- Loss of water-soluble vitamins
To avoid these issues, refrain from freezing opened or leftover soya milk. Instead, purchase small containers and use within a week of opening. Properly stored refrigerated soya milk will retain the best quality and flavor.
Soya milk is a convenient, lactose-free alternative to dairy milk. But like many plant-based milks, it doesn’t hold up well to being frozen. Follow these simple tips to enjoy soya milk at its best.