Raw Materials - How Clean is Clean?

Here on my farm, I grow and harvest botanicals that are used for various products for my own purposes. If not used immediately as fresh product, they’re dried and infused in oils, honey, vinegars, and alcohol or simply stored away for teas or cold infusions. This dried material looks pristine, not a speck of dirt is noted and I inspect them thoroughly. But is it? More than once, a product I designated as ‘dried and clean’ ended up with mold or some other contaminant. In my case, it doesn’t really matter. I’m not selling product and worrying about the quality for customers so my contaminated product ends up on the compost pile and I move on. But when you consider volumes of a raw material that is needed for products down line, ensuring high quality, stable, and contaminant free products is critical.

Following Good Agricultural and Collection Practices is an important first step in preventing contamination throughout harvesting, washing, cleaning, and drying. The ‘drying’ step is particularly important and defining a specification for an acceptable condition at this stage is crucial. Harvesting and hanging product to dry upside down, possibly with circulation, is fairly common for small producers with ‘dry’ occurring when the stem will snap. In humid environments, this can take days. At this point, producers may opt to pull a sample and test for microbial and other contamination, approving or rejecting the entire lot based on the results when achieving predefined test limits. This may suffice for small lots and product that’s processed further in aseptic conditions (alcohol), but for large quantities of dried product, what is acceptable?

Large lots may require additional processing to ensure the entire lot is stable and free from microbial loads, i.e. sterilization methods. Typical methods are steam sterilization, ethylene oxide exposure, and gamma radiation. Herbalists often shy away from using such products because of product degradation and toxic residues. Infrared exposure, though, may alleviate some of these fears and yet provide a superior end product that is stable and free from microbial, fungal, and viral contaminants. Following this article is an excellent table showing the comparison of these methods compiled and shared by Phil Kaeding, SRPharmS.

Last month, Sue Marshall, founder of Netzro, and I met to discuss the use of infrared sterilization technology she developed and implemented at her company in the upper Midwest. Here it’s used to process brewer’s and distiller’s mash into upcycled ingredients among other waste stream products. (Very cool concept and company!!) The sterilization chamber consists of a drum (1000 lb capacity) in which product is tumbled while exposed to intense infrared light over a relatively short time period. These operating variables are optimized based on the condition and form of incoming material. The resulting product is ‘stable’ with little degradation in phytochemicals. By stable, I’m referring to the standard 5 log kill step and acceptable water activity levels that warrant a product free from anticipated microbial growth. A 5 log kill step means that 99.999% of colony forming units (cfus) have been inactivated by this process. Water activity (aw) is a measure of the free water within a material available to support microbial growth and is a better indicator of potential problems than moisture content. A water activity value of 0.6 renders microbial growth impossible. With appropriate packaging, product undergoing a 5 log kill step with low water activity will greatly improve product shelf life. While this process can dry and sterilize within the same cycle, it can also be used for currently dehydrated products. Imagine having access to this technology for receiving international ingredients? Rather than test quality into your lots (conducting microbial tests at receiving), expose all purchased materials to a validated infrared cycle and feel confident that your ingredients are free from contamination, minimally affected by the process, and exhibit improved shelf stability.

This summer, I hope to experiment with my own harvested product by running a small study to determine the effects of infrared exposure on phytochemicals of nettles (Urtica sp.). I’ll be sure to post the results here! In the meantime, check out the amazing things happening at Netzro.

Happy Spring!

Raw Materials - How Clean is Clean?

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