For the last few years I've made my tomato sauces in a slow cooker ('crock pot'), or actually, in a machine that is sold as a 'plate warmer' but works great for low temperature cooking. I pre-heat the ingredients on my stove, then transfer it to the slow cooker for 10 or 14 hours to let all the flavors blend, then I puree and can the result. When I first learned this technique, I was told not to stir the sauce, because the long cooking time makes the sugars at the top caramelize and that would bring out a great sweet flavor. Indeed the top, after being in the cooker for that long, browns a bit, and the flavor is great.
However, recently I was learning a bit more about caramelization to understand my baking better, and it turns out that there are no sugars that caramelize at temperatures < 110 °C. So now I'm wondering - is this caramelization of my tomato sauce just a myth? The machine only goes up to 90 °C. I've checked the temperature at various depths in my sauce with an infrared thermometer, and indeed the temperature is nowhere higher than that. Anyone have more than anecdotal information on the chemistry of making tomato sauce?