It is because the instant coffee is freeze dried. When the coffee is freeze dried, the water inside is frozen and then sublimates during the process. The sublimation causes pores to be formed in the coffee, which allows for ready reabsorption of water. read more
Instant coffee is the dried soluble portion of roasted coffee, which can be presented to the consumer in either powder or granule form for immediate make-up in hot water, whilst the insoluble parts, or spent coffee grounds, are left behind at the factory, for the manufacturer to dispose of. read more