Almond milk has become a popular plant-based milk alternative, but its relatively short shelf life of 7-10 days once opened is a downside for many consumers. Understanding why almond milk spoils so quickly can help you get the most out of each carton and reduce food waste.
The Shelf Stable Nature of Unopened Almond Milk
Unopened, commercially packaged almond milk can last 5-7 days past its printed expiration date if stored properly in the fridge. This is because of the ultra high temperature (UHT) pasteurization process used by most major brands like Silk and Califia Farms. This heating method kills more bacteria and enzymes than regular pasteurization, allowing the milk to be shelf stable before opening.
The aseptic packaging used for almond milk also protects the milk from oxygen, light exposure, and contamination from opening and closing the package. Pouches, cartons, and bottles keep the milk safe and extend its shelf life until you break the seal.
Why Opened Almond Milk Expires Rapidly
Once exposed to air and light, the composition of almond milk causes it to degrade quicker than dairy milk. Here are the main reasons opened almond milk goes bad within 7-10 days:
1. Lack of Preservatives
Unlike cow’s milk, almond milk has no natural antimicrobial components like lactoferrin and lysozyme that combat spoilage. Most brands also do not add chemical preservatives. This leaves almond milk vulnerable to rapid spoilage from mold, bacteria, and other microbes entering the carton when it’s opened.
2. Low Acidity
The pH of almond milk ranges from 6.5-7.5, which is close to neutral. This low acidity provides a welcome environment for many microbes to thrive and multiply once oxygen is introduced. Fermented dairy milk has a lower pH around 4.5-4.7 that inhibits microbial growth.
3. High Nutrient Content
Almond milk contains proteins, sugars like sucrose, and trace nutrients that fungi and bacteria love to feast on. The microbes metabolize these compounds, using them for energy and growth. This leads to faster spoilage.
4. Lack of Competition from Good Microbes
Beneficial lactic acid bacteria dominate dairy milk, making it difficult for spoilage microbes to proliferate. Almond milk has very low microbial loads when packaged, so pathogenic bacteria have an open playing field once opened.
5. Oxidation of Fats
Exposure to oxygen causes the fragile unsaturated fats in almond milk to oxidize or go rancid faster than the more stable saturated fats in regular milk. Rancidification causes unpleasant taste and aroma.
Ways to Slow Spoilage of Opened Almond Milk
While almond milk only lasts about a week after opening, you can get a few more days and reduce waste by:
- Storing opened cartons at the back of the fridge furthest from the door where temperature is most stable.
- Keeping milk chilled at all times and avoiding leaving it out on the counter.
- Sealing the container tightly after each use.
- Rinsing remnants out of glasses before pouring fresh milk to avoid contamination.
- Only pouring out needed portions instead of the whole carton.
- Checking for signs of spoilage like off odors, change in color, curdling, or mold growth before consuming.
How to Tell If Almond Milk Has Gone Bad
Look for the following changes to determine if your opened almond milk has spoiled:
Smell
Rancid or sour smells indicate the fats have oxidized or lactic acid bacteria have multiplied due to spoilage.
Appearance
If you notice any clumps, curdling, separation, sliminess, or fuzzy mold, do not drink the almond milk.
Taste
Spoiled milk will taste off with a bitter, acidic, or very sour flavor.
Color
The milk may turn yellow or brown from oxidation reactions or microbial metabolites.
If your almond milk shows any of these signs of spoilage, err on the side of caution and discard it. Consuming spoiled milk can cause food poisoning and stomach issues.
How Long Can Almond Milk Be Left Unrefrigerated?
As almond milk does not contain any natural antimicrobial compounds, it should not be left out at room temperature if possible. Here are some general guidelines for how long it can be left unrefrigerated before spoiling:
- Unopened shelf stable milk: Up to 7-10 days.
- Opened refrigerated milk: Up to 2 hours.
- Opened refrigerated milk in hot environment (over 90°F): Discard after 1 hour.
Leaving almond milk out too long at warm temperatures allows microbial and enzymatic activity to accelerate, causing off flavors, curdling, and potential pathogenic bacteria growth.
Can Spoiled Almond Milk Make You Sick?
Consuming spoiled almond milk can cause food poisoning symptoms like:
- Nausea
- Vomiting
- Diarrhea
- Stomach cramps
- Fever
This is caused by dangerous levels of bacteria like staphylococcus, salmonella, E. coli, and listeria in the milk from spoilage. Their toxic waste products and metabolites also irritate the digestive tract.
Mold that grows in the milk produces mycotoxins that have immunosuppressant effects if ingested. Some people may have severe allergic reactions to these toxins.
Those with compromised immune systems like young children, the elderly, and pregnant women are at higher risk of infection and dangerous complications. Healthy adults may recover after a couple days of gastroenteritis symptoms.
Can You Extend the Shelf Life?
Unfortunately, there is no safe way to significantly extend the shelf life of opened almond milk stored in the fridge. However, you can freeze unused portions to prolong its safe use.
Freezing
Freezing unused almond milk in airtight containers can allow it to be safely stored for 3-4 months. Make sure to leave room at the top for expansion and date the containers.
Thaw frozen milk overnight in the fridge before use. Give it a shake or stir to reincorporate any separation. The texture and taste will be slightly different after thawing but still palatable.
Refreezing
Previously frozen milk should not be refrozen after thawing, as this can compromise safety and quality.
Cooking
You can extend the shelf life by a few days past 7-10 days if the milk is cooked and incorporated into baked goods, oatmeal, or other hot foods that reach at least 165°F. This helps destroy pathogens, but quality decline may still be noticeable.
Souring
Allowing the milk to ferment into a sour, yogurt-like consistency can add a few more days but also significantly alters texture and flavor. Most find it unpalatable as a beverage after souring.
Additives
Adding preservatives like potassium sorbate or herbal extracts can potentially extend shelf life by a few days but is not recommended for food safety reasons without careful pH testing and dosage calculations.
Bottom Line
In summary, commercially prepared almond milk will stay fresh for:
- 5-7 days past printed expiration date if unopened and refrigerated.
- 7-10 days once opened if continually refrigerated.
- Up to 1 hour if left out after opening.
Freezing unused portions, cooking it, and practicing proper storage hygiene lets you safely get the most shelf life from each carton. But ultimately the lack of preservatives and neutral pH of almond milk means it does not keep as long after opening compared to cow’s milk.
