KPC Products Inc.
(US Main Office)
16 Goddard
Irvine, CA 92618
Tel: 949-727-4000
Orders: 800-KPC-8188
Fax: 949-727-3577

The vast majority of Chinese herbs derive from natural plant, animal and mineral products. Herbs, like any natural product stored for an extended period of time, become vulnerable to mold and insect infestation. It is common for mainland Chinese herbal farmers to use a sulfur-based fumigation process to control decay from insect infestation and mold occurring in herbs stored for long periods of time. It also serves to exterminate existing pathogens. Sulfur cleans the raw herbs, clearing away excess skin, even in closed, unexposed spaces. Burning sulfur for fumigation provides an efficient method to simultaneously exterminate harmful insects, bacteria, and prevent insects and mold.

However, sulfur-based fumigation produces sulfur dioxide as a chemical byproduct and produces changes within herbs. In addition to acting as an insecticide and repellent, sulfur dioxide also is a bleaching agent and is therefore well-suited for the herbs shan yao, ge gen, and gan jiang. But for high sugar-content raw herbs, the sulfur-based fumigating can make the flavor of herbs more acidic - the herb gou ji being a classic example. Also, fumigating herbs that contain fatty oils, such as tao ren, will oxidize the herb, and cause it to give off pungent oil odors. And herbs that easily change shape or color, such as chrysanthemum (ju hua), are never fumigated with sulfur dioxide because it damages the herb’s fundamental qualities.

Use of sulfur dioxide and alkali produces inorganic sulfites, and ingesting these sulfites can cause harmful health side effects in people, such as diarrhea, allergic reactions and asthma. The FDA has long designated sulfites “generally recognized as safe (GRAS)”, and it is widely used to preserve the clarity of white wine and as a preservative in fruits. But for food products containing sulfite residues exceeding 10ppm, the FDA regulates that a warning must be declared on the label.

There are a few ways to detect for sulfites, including by aerated-oxidization, iodine titration, atomic absorption spectrum and direct color comparison. KP uses the government-approved Rankine Method for residue analysis, also known as the alkali titration method. The principle behind it is to place the herbal ingredient with the acid and then distill it, absorbing the SO2 into the oxidized H202. After sulfuric acid is produced, an alkali titration method is used to detect for sulfite residues. Olive green signifies an absence of oxidized sulfur residue. A purplish-red color signifies the presence of oxidized sulfuric residue.