It is assumed that instant coffee does not require a hechsher, since coffee plants process just that and nothing else. Although there are forms of flavored instant coffees, the flavors are added at ambient temperatures after the drying process. Nevertheless, it is good and prudent practice to purchase instant coffee with a hechsher. Circumstances and processing methods are always subject to change, and require constant monitoring to confirm that these assumptions remain correct. Many years ago, Rav Yosef Eliyahu Henkin zt’l recommended that consumers purchase salt and other seemingly harmless products, with a hechsher only (see Eidus LeYisroel p. 132).
Today, instant coffee is processed one of two ways.
Spray Drying - This entails forcing an atomized spray of very strong coffee extract through a jet of hot air. The liquid evaporates leaving behind dried coffee. An interesting but little known fact is that coffee loses much of its aroma due to spray drying. As aroma is all important to the resulting flavor of the coffee, most manufacturers will spray a coffee oil on the powder to add back some of the lost aroma. This is known as aromatizing. In another attempt to make the instant coffee as much like real ground coffee as possible, the powder is put through a heating process which causes it to clump. It is then ground to resemble real ground coffee. This is called agglomeration.
Freeze Drying - Freeze dried coffee is produced by freezing liquid coffee and then placing the product under a vacuum enabling the frozen liquid to vaporize without passing through the liquid phase. This is known as sublimation. Since coffee produced through these methods is manufactured at dedicated plants, they present no kashrus problems.
All unflavored coffee is acceptable without certification.
COFFEE - 100% regular coffee requires no supervision.