Since your girls are 15 months old, you cannot reason with them much now. But as you are raising them, remember that YOU are the adult. You set the boundaries. Surely they will outgrow the screaming, but also perhaps, you can help by anticipating their food needs earlier. Don't wait until they are starving. Have structured times for meals, get food ready quickly, have something like predinner snacks that you can pull out to put before them at the first sign, before they get to the screaming stage. And babies soon discover how to impact the household by screaming, some of which is normal. And they feed off the moods of each other also, so it's not easy.
But also, at age 15 months, you can have an impact, getting their attention forcefully but calmly to teach them the word "No," if you haven't already. You can talk to them, explaining that you do not like the screaming. They are understanding quite a lot of verbalization going on around them, so it will have an impact.
Know that it is NOT normal for them to scream all the time, to scream to get their way, for once they discover that it really rattles you, they can scream to manipulate the tone in the room, or try your patience. So as soon as they begin to mature, set rules.
If you're fixing them food, and they begin to scream, and you don't want to hear it, give them a warning, one warning only, after you have explained whatever consequence there will be if they violate the rule. Stick to it. Walk away from the food-fixing...say you'll try again later when they have calmed, whatever it takes to get their attention and reeestablish dominance.
Watch SuperNanny, or the other Nanny show, or even The Dog Whisperer with Cesar Milano, to see how to set rules and enforce them. It's not rocket science, just common sense stuff of "being the pack leader".
You have the leverage on your side. You'll have things they want, and you can take away things they have. Make them believe. Let them have a screaming room, their own bedroom perhaps, and send/take them to it when they need to scream. Tell them, "I'm not going to have it in here" and make it stick! Assert yourself. You have rights too.
For now, best wishes. Not for nothing do they call this time the "terrible twos!" And even as I say that, I recall with great fondness that it is also a time of magical openness and discovery. Celebrate. It goes by very fast and then is gone.