I have experienced the "rice clumps" and although I AM NOT a doctor I can share the experience with you. I contributed the situation to a few factors and modified a few behaviors and the clumps were gone. [The practice of denied-ejaculation or EDGING should be avoided - if you set out to accomplish something then you need to finish. I thought of the rice clumps as geled seminal fluid that was accumulated in the seminal ducts. It may not dry but it can conceivably "gel".
Up the water, drop the caffeine, drop the boose and talk to your doc about your current meds (even OTC's you use regularly). Cause an ejaculation either alone or with partner (intercourse always produces a greater volume of ejaculate than masturbation) - so you are flushing out the "rice". Eat fruit daily (high in "C") and vegetables. Caffeine is a dietetic - you need the water!!