Why does some almond milk not need to be refrigerated?

Almond milk has become an increasingly popular plant-based milk alternative in recent years. With its creamy texture and nutty flavor, almond milk can be used in many of the same ways as traditional dairy milk – in cereal, coffee, smoothies, baking, and more. While most almond milks on the market need to be stored in the refrigerator after opening, some shelf-stable varieties allow for unrefrigerated storage. This allows for greater convenience and portability. But why is it that some almond milks can last unrefrigerated, while others require chilling? The answer lies in how the different products are processed and packaged.

The Two Main Types of Almond Milk

There are two main types of commercially produced almond milk: refrigerated almond milk and shelf-stable almond milk. Here is a comparison:

Refrigerated Almond Milk Shelf-Stable Almond Milk
  • Found in the refrigerated dairy case
  • Needs to be refrigerated after opening
  • Spoils within 7-10 days of opening
  • No preservatives added
  • Higher protein and calcium content
  • Found on the shelf in aseptic packaging
  • Can be stored unopened at room temperature
  • Lasts unrefrigerated for several months after opening
  • Contains preservatives
  • Lower protein and calcium content

As you can see, the key difference lies in how the two types are processed and packaged to allow for different storage requirements. Next, let’s look at this in more detail.

How Refrigerated Almond Milk is Made

Refrigerated almond milk is designed to closely mimic the taste and nutritional profile of fresh dairy milk. To make it, almonds are first soaked in water to soften. Then, the almonds are ground into a pulp and strained to separate out the nut milk. The nut pulp is discarded and the milk is homogenized for consistency. Finally, nutrients like calcium, vitamin D and vitamin E may be added to enrich the milk’s nutritional value. Refrigerated almond milk often contains a higher percentage of almonds, typically around 2-3%. This gives it a richer, creamier texture.

As refrigerated almond milk does not undergo high-temperature processing or have preservatives added, it is highly perishable. Once opened, it must be stored in the refrigerator and used within 7-10 days. After this point, spoilage organisms like yeasts, molds and bacteria will start to multiply, making it unsafe to drink. Refrigeration helps slow the growth of these organisms significantly, giving refrigerated almond milk a decent shelf life if handled properly.

How Shelf-Stable Almond Milk is Made

Shelf-stable or aseptic almond milk undergoes a much different manufacturing process that allows it to be stored unopened at room temperature for months. Here are the key steps:

  1. Almonds are ground into a pulp and strained to extract the nut milk, similarly to refrigerated almond milk. However, a lower ratio of almonds is used, typically around 1-2%.
  2. The milk is supplemented with viscosity agents like gellan gum, guar gum or carrageenan. This gives the milk more body despite the lower nut content.
  3. The milk is homogenized for consistent texture and mouthfeel.
  4. The milk undergoes ultra high-temperature (UHT) processing. It is heated to temperatures between 275-300°F for 2-4 seconds using steam injection. This kills any bacteria present while preserving nutrients.
  5. After UHT processing, an aseptic filler pumps the milk into sterile Tetra Pak cartons. The cartons have been sterilized with hydrogen peroxide beforehand. Filling occurs in a sterile closed system to prevent recontamination.
  6. Preservatives like potassium sorbate may be added as an extra guard against microbial growth.
  7. The Tetra Pak cartons are sealed and can sit at room temperature until opened by the consumer.

Thanks the the UHT treatment and aseptic packaging, shelf-stable almond milk can resist spoilage without refrigeration. Its higher processing temperatures do result in slightly greater nutrient degradation compared to refrigerated varieties. However shelf-stable options still retain many of almond milk’s nutritional benefits.

Why Refrigeration is Still Needed After Opening

Once opened, both refrigerated and shelf-stable almond milk need to be stored in the refrigerator. This is because the opening compromises the product’s isolation from outside microbes and oxygen. Although shelf-stable almond milk has been heat treated and contains preservatives, it is still perishable once exposed to air.

Here are some of the potential sources of microbes that can enter the milk after opening:

  • Air – There are many yeasts, molds and bacteria floating in the air that can contaminate the milk.
  • Utensils – Any spoon or cup that touches the milk could introduce microbes.
  • Fingers and hands – Simply dipping your fingers into the milk while pouring adds new bacteria.

Once contaminated, the nutrients in almond milk become an ideal environment for rapid microbial growth. Refrigeration helps slow this growth down by reducing microbial enzyme activity and multiplication rates. However, refrigerated shelf life is still limited. Even refrigerated, opened almond milk should be consumed within about a week for safety.

Comparison of Opened Shelf Life

Type Refrigerated after Opening Unrefrigerated after Opening
Refrigerated Almond Milk 7-10 days 1-2 days
Shelf-Stable Almond Milk 7-10 days 5-7 days

As you can see, even the shelf-stable varieties are only good for about a week without refrigeration after opening. The shelf-stable milk lasts a few days longer unrefrigerated thanks to its preservatives. However, for optimal safety and quality, storage in the fridge is still required regardless of the type of almond milk.

Signs Your Opened Almond Milk Has Spoiled

How can you tell if your opened almond milk has gone bad and needs to be discarded? Here are a few signs of spoilage:

  • Sour smell & taste: Fresh almond milk smells and tastes slightly sweet and nutty. Spoiled milk will smell and taste sour or bitter.
  • Clumps or curdling: Microbial growth can cause proteins and fats to cluster together in clumps or curdles.
  • Gas bubbles: Gas produced by microbial fermentation may create bubbling or foamy appearance.
  • Mold growth: If you see fuzzy mold growing in the milk, it should be discarded.
  • Change in color: The milk may shift from creamy white to a yellow or brownish hue.

If you notice your almond milk exhibits any of these traits, it is best to throw it out. Consuming spoiled milk can potentially lead to foodborne illness.

Maximizing the Shelf Life of Opened Almond Milk

To get the most out of your opened almond milk and minimize waste, be sure to follow proper storage guidelines:

  • Transfer to a clean airtight container and refrigerate immediately after opening.
  • Check the “use by” date – don’t use after this timeframe even if refrigerated.
  • When refrigerated, use opened milk within 7-10 days.
  • When pouring, don’t let the spout touch the glass to avoid contamination.
  • Keep your refrigerator set below 40°F.
  • Don’t return unused milk back to the container – this can introduce bacteria.
  • Make sure to wash any utensils or containers that contact the milk.

Following these tips will help inhibit microbial growth and extend the usable life of your refrigerated almond milk.

Shelf-Stable Varieties Offer Convenience, But Refrigeration Still Matters

In summary, shelf-stable almond milk provides convenience thanks to its ability to be stored unrefrigerated while sealed. However, once opened it still requires refrigeration to stay safe and fresh. While the higher heat processing of shelf-stable milk gives it a slightly longer unrefrigerated shelf life after opening, it will still spoil rapidly if left out too long. Refrigeration inhibits microbial growth, so keeping opened almond milk chilled remains important, regardless of the type. Checking for signs of spoilage and observing proper “use by” dates is also essential. With the proper storage and handling, both refrigerated and shelf-stable varieties can be enjoyed safely and to their fullest potential.

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