Most ideas for groundbaits came from the continent anyway. Belgium mainly and France. Using Brasem and stuff and cattle cake ground up.
I'm sure the pros go out and test them, but as always, it's a confidence thing. If you use one and you catch, you'll use it again and recommend it. If you don't catch you'll keep quiet.
Angling Times do some tests from time to time, but not sure when or if they have done groundbaits. I did read about bait flavour additives and pineapple came out well for many species except tench. Tiger nut oil also seems a popular attractant with bream although I swear by Sensas Bream 3000, red if possible, it smell to me of carrot cake so cinnamon perhaps? Also VdE Lake that smells of liquorice allsorts, perhaps some star anise in there too?
It's always interestign to try making up you own. One I'm working with is -
1 part ground fishmeal
1 part Nesquick chocolate milkshake powder
2-4 parts brown crumb whatever pleases you.
So far it's been OK, wouldn't rave about it, but bad days are always possible and unfair to judge a groundbait if the fish aren't playing.
Would also say, it's worth trying mixing soem large bargain bags of spices from supermarkets with your breadcrumbs. Turmeric is a good one (add a little to your maggots as well, esp in winter) and corriander powder is supposedly good for roach and has worked with me.