I typically use feed grade cane black strap molasses and always ensure it has no added preservatives (eg. sulphur). I often have upwards of 50 gallons in 5 gallon pails on site and have had them in storage over a year with no issues. I don't know why anyone would use a preservative besides a fungicide like sulphur in molasses, which is used itself as a preservative in some materials. Fish hydrolysate on the other hand must be preserved with phosphoric or sulphuric acid or it ruptures. I've experienced this.