What was the pan made of that you simmered this in?

reactive metals

With Worcestershire sauce & soy sauce, it seems very normal color to me. I would be surprised if it comes out redder.

dcarch

-rob, just a regular stainless steel pot.

-dcarch, so you think just a splash of the two would cause the color?? It was still bright red after I first added them to the tomato sauce. Do you think they built up color as it simmered?

CMK

You said that in the past, the sauce has been redder.... So you used the same recipe in the past? What exactly was changed this time? Same ingredients plus same process should yield same results, that's why we call them recipes. But any changes you make will alter your end result.

I can think of a lot of things that would darken if I simmered them for an hour or more...

If you had added nothing to the tomato sauce, it would still turn brown after simmering for a long time. I think Carol got it right.

I thought this was an intriguing question. It's not the soda. I think the extent of the brownness comes from all the brown things, as Dcarch said, but there's also the thing where tomato sauces go from a bright red to a dark one after simmering a long time as Carol and Donna said. I couldn't find anything easily online that said why, however. Some talked about the sugars in the tomato caramelizing, but those sounded like guesses rather than authoritative.

I've read things about interactions with the pan, too, as Rob alluded to, but I've had barbecue sauce go brownish in enamel. A much redder brown, but I didn't have all the brown ingredients you do (W sauce, soy sauce, honey, smoke). From a painter's point of view, those ingredients cooked enough to really combine with the tomatoes add up to the nutty brown in the picture.

Did you simmer longer than you did before?

Thanks to all that commented.

It isn't a recipe set in stone...I alter according to how much I am cooking. But all the ingredients remained approximately the same except for the baking soda, which I added a lot more of this time (hence my question of whether the SS, W sauce, etc would be enough to turn it darker since they didn't before. It very well could be the fact I simmered them all a bit longer (thought not by too much).

-plllog, thanks for looking around online for me. ;-)
CMK

Certainly cooking for a longer period of time and reducing it further will darken the sauce. I also wonder about the Stevia (I never use artificial anything as I taste the difference). And as an aside: if you're just adding a "dash" of Stevia, why wouldn't you just use nat'l sugar instead? Certainly the calories couldn't be the issue when making a decent size portion of sauce.

Stevia hasn't added color to anything I have used prior. Due to health reasons I refrain from eating sugar as much as possible...only thing I have on hand for sweetening is stevia and honey.

CMK