Oat milk has become an increasingly popular plant-based milk alternative in recent years. However, unlike cow’s milk that can stay fresh for weeks when unopened, oat milk tends to have a much shorter shelf life of around 7-10 days. There are several reasons why oat milk spoils faster than other types of milk.
The ingredients in oat milk
Oat milk is made by blending oats with water, then straining out the oat pulp. The main ingredients are oats and water. Unlike cow’s milk that contains lactose and casein proteins which help preserve it, oat milk does not have these compounds. Oat milk also does not contain preservatives that are commonly added to other plant-based milks like soy or almond milk to extend shelf life.
The lack of natural preservatives, proteins and sugars means oat milk is more prone to spoilage from microbial growth. The oats and water provide ideal conditions for bacteria, yeasts and molds to multiply if stored too long.
Oat milk has a nutrient profile that makes it an ideal environment for spoilage organisms to thrive:
- High moisture content – Over 90% water makes it prone to microbial growth
- Low acidity – Neutral pH around 6.4 favors bacterial growth
- Abundant nutrients – Oats contain carbohydrates, proteins, fats for microbial metabolism
The ample water and nutrients allow bacteria to rapidly flourish if the milk is not stored properly. The neutral pH does not inhibit growth of either bacteria or fungi.
Unlike commercial cow’s milk that is pasteurized at high heat to kill microbes, most oat milk is produced using a cold milling process:
- Oats are cleaned and soaked in water
- The mixture is blended then strained to extract the milk
- The raw oat milk is then bottled
This cold process maintains more nutrients but does not remove spoilage microorganisms. Relying solely on hygienic practices during production means some bacteria may remain in the finished oat milk. Even cooling and refrigerated storage will only slow microbial growth for a limited time.
Use of natural thickeners
To improve the texture and viscosity of oat milk, natural thickeners like gums or starches may be added during production:
|Gums||Guar gum, locust bean gum, gellan gum|
|Starches||Corn starch, rice starch|
While these thickeners help stabilize the oat milk, they can also serve as nutrient sources for microbial growth. The additional sugars and carbohydrates promote spoilage organism multiplication that causes oat milk to deteriorate faster.
Due to its composition, oat milk is vulnerable to contamination at multiple points during production and handling:
- Raw ingredients – Oats or water may contain bacteria from the farm
- Equipment – Blending and bottling tools can introduce microbes
- Bottling – Filling containers exposes milk to air and surfaces
- Storage – Refrigeration slows but does not prevent spoilage
- Handling – Each time container is opened allows microbial entry
Careful sanitation and cold storage helps minimize contamination risks. However, oat milk’s lack of preservatives means any bacteria, yeast or mold introduced during processing or handling can proliferate, causing it to spoil within 7-10 days.
Signs of spoilage
Oat milk will show the following signs when it has spoiled and should no longer be consumed:
- Sour, yeasty or moldy smell
- Change in appearance – separation, clumping, sliminess
- Gas bubbles or frothing
- Change in color – from white to yellow or pink
- Change in texture – becomes slimy or chunky
These changes occur once bacteria, yeast or mold growth in the oat milk reach high levels. While sensory changes are most obvious, harmful microbial metabolites may also form without significantly altering taste or texture.
Microbial spoilage agents
The microorganisms responsible for oat milk spoilage include:
|Lactic acid bacteria||Ferment lactose and carbohydrates, causing souring|
|Yeasts||Growth produces gas and alcohol, leads to frothing|
|Molds||Mycelial growth results in clumping, discoloration|
|Bacillus, Clostridia||Form slimy textures, rotting odors|
|Pseudomonas, Proteus||Create putrid, bitter flavors|
These bacteria, yeasts and molds originates from the environment, equipment, handlers, etc. Given oat milk’s susceptibility, even a few cells can grow to millions within days if temperature abused.
Preventing rapid spoilage
To extend the shelf life beyond 7-10 days, oat milk producers can take these steps:
- Sanitize equipment and bottling rooms
- Use high quality raw ingredients
- Pasteurize final product to kill microbes
- Acidify milk to inhibit bacteria
- Add preservatives like potassium sorbate
- Use aseptic filling processes
- Provide refrigerated supply chain
However, adding processing steps or ingredients may increase costs and reduce the natural image of oat milk. Ultimately milk composition and consumer handling have the biggest impact on how long oat milk stays fresh.
The bottom line
Oat milk has a short shelf stable time around 7-10 days due to its:
- High water content
- Abundant nutrients
- Near neutral pH
- Lack of preservatives
- Minimal processing
These qualities create an environment ideal for spoilage organisms like bacteria, yeasts and molds to thrive. Proper refrigeration and hygienic handling can help extend freshness. But oat milk’s composition means it has a much shorter shelf life compared to pasteurized dairy milk when unopened. The upside is oat milk retains more nutrients and flavors compared to more processed milks. But the tradeoff is it has to be consumed within about a week of production for best quality.