Why can’t you freeze soya milk?
Soya milk has become a popular plant-based milk alternative for many people. It is made from soaked soybeans that are ground with water. The liquid is then strained to remove the solids. Soya milk contains protein, vitamin B12, calcium, and other nutrients found in dairy milk, but without the lactose that can cause issues for some people. Its creamy texture makes it work well in many recipes that call for regular milk. However, there is one key difference – soya milk generally cannot be frozen successfully.
What Happens When You Freeze Soya Milk
Freezing is a common way to preserve regular milk for later use. The cold temperatures slow down spoilage by preventing bacteria growth. However, the components in soya milk react differently to freezing. The main proteins in soya milk are glycinin and beta-conglycinin. Below freezing temperatures cause these proteins to denature, meaning they lose their natural structure. This results in an irreversible change in the proteins’ properties.
In particular, the proteins start to clump together when thawed after freezing. This gives the soya milk a gritty, chalky, and unpleasant texture. The liquid also tends to separate, with the fats and solids floating to the top or sinking to the bottom. While still safe to drink, the mouthfeel and appearance of frozen and thawed soya milk are significantly degraded. No amount of shaking or stirring will restore it to its original smooth and creamy state prior to freezing.
Why Does Freezing Affect Soya Milk Proteins?
The main proteins in soya milk, glycinin and beta-conglycinin, have large, complex structures. These structures are stabilized by many different types of interactions between the protein molecules. These include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals forces. Freezing causes irreversible damage to many of these stabilizing interactions:
- Hydrogen bonds are disrupted when water freezes into ice crystals.
- The increased concentration of solutes during freezing alters ionic interactions.
- Ice crystallization damages the tertiary and quaternary structures of the proteins.
- Thawing leads to aggregation of exposed protein segments.
This damage is difficult to reverse once it has occurred. While the proteins remain safe to consume, the structural changes lead to an undesirable texture and appearance.
Comparing Soya Milk Proteins to Dairy Milk Proteins
It is useful to compare the composition of soya milk and dairy milk proteins to understand the differences in how they respond to freezing. Here is a table comparing the main proteins in each type of milk:
| Milk Type | Main Proteins | Properties |
|---|---|---|
| Soya Milk | Glycinin and beta-conglycinin | – Large globular proteins – Complex quaternary structures – Stabilized by hydrogen bonds, ionic interactions |
| Dairy Milk | Casein and whey | – Smaller proteins – More flexible structures – Stabilized by hydrophobic interactions |
The major proteins in dairy milk tend to have more flexible and disordered structures. Casein micelles are held together mainly by hydrophobic interactions. And whey proteins have compact globular shapes stabilized by their well-packed hydrophobic cores. These features allow dairy milk proteins to better withstand freezing temperatures with less permanent damage to their structures. They can return to their native states more easily upon thawing.
Should You Freeze Leftover Soya Milk?
Based on the irreversible changes that occur when soya milk proteins are frozen, it is best to avoid freezing leftover soya milk. The thawed milk will be gritty and separated, and mixing cannot restore its smoothness. However, if you have excess soya milk, there are some better options for preserving it:
- Refrigerate – Store leftover soya milk in a sealed container in the fridge. It will keep for 3-4 days.
- Freeze as cubes – Pour soya milk into an ice cube tray and freeze. Use the cubes within a day or two.
- Cook into a sauce – Make a creamy sauce or gravy by cooking the milk into a starch-thickened base.
- Bake into recipes – Use extra soya milk when making muffins, breads, or other baked goods.
The impact of freezing may be reduced if the soya milk is combined with other ingredients. But for drinking, your best bet is to refrigerate unused soya milk and consume it within a few days.
Changes in Nutrient Content Upon Freezing
In addition to texture changes, freezing and thawing soya milk can also degrade some of its nutrients:
- Vitamins – Water-soluble vitamins like vitamin C and the B vitamins are sensitive to freezing damage and leaching into the liquid.
- Polyunsaturated fats – The double bonds in polyunsaturated fats can undergo lipid oxidation during freezing, forming harmful free radicals.
- Color – Freezing often causes separation of milk pigments, resulting in a lighter color.
However, freezing does help retain most minerals, monounsaturated fats, and protein quality in soya milk. Just be aware that the levels of some vitamins and polyunsaturated fats may decrease compared to fresh soya milk.
Soya Milk Alternatives That Can Be Frozen
If you want to keep a stash of milk that can be easily frozen, there are a few options that freeze better than soya milk:
| Milk Type | Freezing Notes |
|---|---|
| Coconut milk | – Shake well before and after freezing to reincorporate fats – May separate slightly upon thawing |
| Almond milk | – Works well frozen but contains less protein – Shake after thawing to remix |
| Rice milk | – Freezes fairly well but separates more than almond or coconut milk |
| Hemp milk | – Higher protein content makes it suitable for freezing – Flavor and creaminess may degrade slightly |
Each milk alternative has its pros and cons when frozen. But overall, they maintain their texture and nutritional qualities better than soya milk after being thawed. Coconut, almond, and hemp milk are good options for keeping on hand in the freezer.
What About Freezing Silken Tofu?
Silken tofu is made from soya milk, so does that also degrade when frozen? Silken tofu has a much higher protein content, usually around 6-9% compared to 3-4% in soya milk. It also contains coagulants that help the proteins set into a soft gel. These two factors mean silken tofu holds up relatively well in the freezer.
There may be some unavoidable changes in texture, such as a slightly more crumbly or spongy consistency once thawed. But the overall integrity of the tofu remains intact. Most of the time, freezing is actually recommended for silken tofu to create a more porous structure. Just make sure to freeze it in water to prevent dehydration and wrap well to prevent freezer burn.
Troubleshooting Problems With Frozen Soya Milk
If you do end up freezing soya milk, here are some tips for troubleshooting the common issues that arise after thawing:
- Grainy texture – Blend in a high-speed blender to break down some clumps. Straining through a cheesecloth can help too.
- Separation – Vigorously shake or blend to reincorporate. Adding a stabilizer like cornstarch may help bind it.
- Flat taste – Boost flavor with vanilla, cocoa powder, or sweeteners.
- Discoloration – Add a shake of turmeric or annatto powder to restore creaminess.
While frozen and thawed soya milk won’t be quite the same, these tips can improve its drinkability in a pinch. But for the best results, just avoid freezing soya milk when possible.
The Bottom Line
Freezing is not recommended for soya milk due to irreversible changes that occur in its proteins. Glycinin and beta-conglycinin undergo damaging aggregation and structural changes when frozen that cannot be reversed. This gives thawed soya milk a gritty, clumpy, and watery texture instead of its naturally smooth and creamy consistency. Some nutrients also degrade during freezing. For long-term storage, refrigerate soya milk and use within 3-4 days for the best quality. When cooking, soya milk can be incorporated into baked goods or thickened sauces before freezing. Overall, it’s best to choose a different milk variety like coconut, almond, or hemp milk if you want to keep milk in the freezer.
