I'm really not the guy to ask about nutrition but one thing I do know is that when you're on the rivet solid food is really hard for your body to digest. Like almost impossible, so bars are not really your friend. Calories in liquid and gel form go down best.
Based on your own body weight, power output and event duration you should be able to roughly calculate your energy requirements and consume accordingly. I don't know what you ate before the event but personally I like to get some healthy fats and a bunch of carbs a minimum of two hours before my event starts. That' way the energy fully digested and stored for use and my stomach has nothing in it to get upset when the effort comes.
That being said most people need some solid food at some point just to feel like they've eaten. Notice that pros in the peloton regularly have sandwiches at some point during the day (and fans of coke!!!) though they tend to not be hammering all day long. YMMV of course.
Also did you warm up before the start of the race? Going from rest to 42 kph is a shock to your system and will make most people hurt right out of the gate. That'll make it mentally tough to keep up the pace even if your body can handle it.