I was wrong, our experience with blackstrap has lead to sporadic results. We use a blended cane molasses, made at US Sugar. You just need to be careful of the source of Blackstrap.
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Purchasing Molasses from the Bulk Tank at Your Local Feed and Grain Store for Making AEM for Utility and Livestock Use
And now, a word of warning: it may be tempting to purchase cheap blackstrap molasses from the bulk tank at your local feed and grain store: my nearby feed store sells feed grade blackstrap molasses for roughly 7 cents a pound, or 79 cents per gallon (blackstrap molasses of 79.5 Brix weighs about 11.8 pounds per gallon), for example. Sometimes you can get good blackstrap molasses this way, but be warned that such bulk molasses has often been cut (usually at the shipping docks or at a distributor) with water, with preservatives, with various sulfur compounds (as a preservative), or even with cheap oils to improve flow. Each of these things can seriously interfere with your Activated EM, even if it is only intended for animal or utility use. It is sometimes very difficult to get hard, clear, clean and accurate answers from managers at feed and grain stores about exactly what is in their bulk molasses; they often simply do not know for sure. Be aware also that this bulk molasses is NEVER sold for human consumption, but only for consumption by animals. I do have plenty of friends who brew AEM for use as a human fermented antioxidant beverage using this same 7 cents per pound feed-grade blackstrap molasses (from my local Southern States Cooperative depot, see below...), but I tend to frown on that practice.
However, on the positive side, I have purchased cheap bulk feed-grade molasses (the way this works is that you bring your own bucket and lid) from my local feed and grain store (Southern States Cooperative), and it has smelled and tasted fine. I then spent the time to find out the name and contact information for the bulk supplier (Westlas), and then called them and asked some questions about their bulk molasses. I also was able to procure copies of all the actual shipping records and the guaranteed analysis for the most recent batch of bulk blackstrap molasses which my local feed store had purchased, which helped me considerably. The molasses I purchased has a Brix (SG) reading of 79.5. According to the local vendor and the distributor, there is no sulphur added, nor any other preservatives or anti-mold agents added; it is simply just pure cheap bulk molasses for animal feed. In this case, as best as I can tell, this molasses seems to be of rather high quality, and I often use it in preparing EM products for my animals (poultry) or for waste or utility use. And, as noted above.... I have neighbors who even brew up large batches of AEM for human consumption using this cheap feed-grade molasses, although I personally believe in using only human-grade blackstrap molasses for making EM brews for human consumption.
More Notes on Molasses Type and Molasses Sources, Feed Grade and Human Food Grade
Whether you are making human-grade or utility/animal-feed grade AEM or other EM brews, I want to repeat my caveat from above to use only blackstrap molasses (versus other grades of molasses), at least when first starting out and learning the ropes. Blackstrap, like all other molasses grades, is a by-product of the refining of sugar, and is the strongest and bitterest molasses, highest in minerals, and lowest in sugars, as it is from the third and final squeezing of sugar cane (or sugar beets). Some animal feed-grade bulk molasses suppliers may call blackstrap by their "internal" trade name of "Cane Molasses", and this name will often signify that there have been no substances or chemicals added such as preservatives, sulfur, anti-molding agents, propionic acid or sodium propionate, or vegetable oils (the latter is added to some grades of feed molasses to allow it to flow more easily and to keep it from caking and drying to a stiff texture on grains.)
I have done some extensive experiments with using other, lighter types of molasses, and frankly, I have not been really satisfied with any of them, although I must admit that some lines/brands of medium molasses (the second squeezing), and often sold in supermarkets labeled as a bit lighter than blackstrap, are usually workable. However, I am not at all satisfied with the results I have had with using the lighter grades of molasses from the first squeezing. These types of molasses are often marketed under the names Barbadoes (aka "Barbados") molasses, West Indies molasses, Island molasses, Jamaican molasses, and an even lighter grade is sometimes marketed in the UK as "Golden Molasses".