A slow food plate is simply a "plate for eating slowly"; it keeps food hot. Heat Retentive Plates are available in the US and can stay hot for more than 1/2 hour after microwaving them for only one...
The addition of preservatives, refrigeration or freezing are used to slow the spoiling of food. Salt is often used as a natural preservative for meats and fish. Sulphites are used with fruit products.
I'm not quite sure, but I think it's because you can enjoy your food more if you chew and eat slower, and also because you actually consume less calories if you chew and eat slower. Unbelievable,...