How To Ensure Shelf-Stability in Preservative-Free Skincare?

How do we Prevent Microbial Growth in Beef Tallow Without Preservatives? This is a time-tested (and lab tested) process that's required in many industries.. But, not required for Tallow Brands. We think that's a real problem.

The answer is a simple process. But, it's something you should really know about if your using, or plan to use, all Natural Skincare products at home. 

INTRODUCTION

You'll see, "Preservative-Free!" front and center on many product labels. Tallow products, in particular. Consumers searching for Natural Skincare seek out products that are 'Free of Preservatives' - but why? 

Preservatives, while useful for preventing microbial growth, can be irritants or allergens themselves. This is even more so for folks with sensitive skin, allergic dermatitis, etc. While avoiding them can make sense... What's the downside? Stuff without preservatives tends to be... well... unpreserved. Meaning, it can go bad.

So, how do we make sure our products without preservatives will NOT go bad? We test for water activity levels, the best indicator of stability in products like tallow creams, balms, and all sorts of other cosmetics. 

Water Activity (a_w)

Description: You can’t see it, taste it, or smell it—but water activity is one of the most important indicators of whether a skincare product will stay safe and stable over time. At Rancher’s Render, we test the water activity of every single batch we make—and here’s why that matters.

What Is Water Activity?

Let’s start simple: Water activity (a_w) is a measure of how much free water is available for microbes like mold, bacteria, or yeast to grow. It’s not the same as how “wet” something feels. It’s about how much of that moisture is biologically available for spoilage organisms.

This concept was first formally introduced in the 1950s by microbiologist William James Scott, who noticed that it wasn’t just moisture content that caused food to spoil—it was the amount of water that microbes could access and use. This became a cornerstone of food preservation science.

Everyday Examples:

Why Does Bread Get Moldy… But Jam Doesn’t?

• Fresh Bread: Has high water activity (~0.95). That’s why it molds fast if left out.
• Frozen Bread: Freezing lowers the *availability* of water, even though it’s still there—so microbes can’t grow.
• Dehydrated Bread (croutons): Lower a_w means no mold. It’s shelf-stable for months.
• Jam: Surprisingly shelf-stable—thanks to sugar. Sugar binds water, lowering water activity (~0.85), keeping bacteria at bay.
• Pickles: Their high salt and acidity drop water activity and pH—two major preservation defenses.

Water Activity and Shelf Life: A Quick Comparison

Why It Matters in Skincare

Most bacteria and mold need a water activity above 0.60 to grow. At Rancher’s Render, our balms are rendered from pure suet with no added water, and we test every batch to ensure it falls well below this threshold—typically under 0.20. That’s our way of proving that our products don’t just feel clean—they are clean, microbiologically speaking.

We Test Every Batch. And You Can Check.

Each jar of Rancher’s Render balm has a batch number on the bottom. That number links back to lab records showing the exact water activity measurement for your product. We don’t just meet FDA safety standards—we verify it. Every time.

Why This Makes a Difference

In a space where many brands rely on “natural” labels without offering lab data or batch traceability, we believe in showing our work. Water activity testing is one of the most overlooked—but most meaningful—steps in ensuring your skincare is safe without relying on harsh preservatives or synthetic additives.

And now that you know about it, you’ll start seeing it everywhere—from your pantry to your medicine cabinet.

Low water activity. Long shelf life. Real transparency. That’s the Rancher’s Render difference.