Dried fruit and nuts are sometimes consumed together as “trail mix,” but that’s not the only reason to group them together. Both dried fruit and nuts are natural products that usually undergo post-harvest processing before they are sold to customers or consumers. Moisture mistakes for both these product categories are similarly painful–too much water means mold, too little means lost profit, not to mention quality issues.
Currently, most growers or buyers use moisture content to determine if tree nuts or dried fruit are too “wet”. This can cause problems. First, the moisture level that causes mold is different for every kind of nut or dried fruit. Second, loss-on-drying moisture isn’t a very precise method for measuring moisture–the answer depends on the method used.
Water activity is different. It’s a snap to identify bad batches that could mold: any product over 0.7 aw can mold, anything under that value won’t. It doesn’t matter what the product is. Using water activity as a standard can eliminate the guesswork over whose moisture meter is right. Two water activity meters measuring the same sample will give the same reading. And if you really want to know your moisture content, the AQUALAB 3 can produce both moisture content and water activity from the same reading.
Over-drying is another problem solved by water activity. Over-drying can kill profits and product texture. For a product sold on weight, even over-drying by 0.2% can add up to tens of thousands in lost profit over time. Water activity helps tightly control the moisture, keeping auditors, your customers, and your pocketbook happy.
Dried fruit and nuts last a long time on the shelf, but not forever. In the end, lipid oxidation and other chemical or enzymatic reactions make the product unpalatable. Because water activity is a measure of energy, it influences how quickly these reactions occur. Use water activity to determine–and lengthen–your shelf life.
Get the essentials of water activity condensed in this 20 minute webinar. You’ll learn:
-What water activity is
-How it’s different from moisture content
-Why it controls microbial growth
-How understanding water activity can help you control moisture in your product.
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