is the method of preparation and cleaning of the rice.

A while back there was a 2-hour special on NHK (Japan national TV) on the various ways to make rice. Tests were done with microscopes to determine a number of factors, including the cleanliness of the rice.

Random taste tests were also done with a wide variety of general public to get the most commonly approved taste.

Hundreds of rice strains and preparation methods were used. Everything from the temperature of the water used when cleaning, the method of washing, additives (sake or vinegar), pre-cook soak time, pre-cook soak temperature, water composition, speed of cooking, altitude, temperature gradient, post-cooking steeping etc. were all studied in depth, by scientists.


TL'DR version: buy a Zojirushi. You'll spend about $500.