The parmesan rind idea is cool. I never thought of that as a source of free glutamate.
I get a bit wound up about people's attitude to MSG. I took a lot of time to research it and really it's just an isolated form of naturally occurring glutamate so it's not really an artificial flavouring per say. What makes me laugh is that people who will not use MSG because it's "artificial" will use table salt which is packed with chemicals.
I think that professionally in Brighton, you'd be well advised to use something like Kombu as you can then sell your product as totally natural. The problem is catering to people who don't really know what they're consuming, just what the media tells them is good and bad. MSG and the glutamate in Kombu are chemically identical but seaweed is good, MSG is bad. These are the same kind of people who would disagree with enhanced pork but would eat Supermarket organic bacon which is errrr... enhnced pork
I personally try to research ingredients, I'm not a fan of artificial ingredients, but I try to take a measured approach. There's plenty of sources will tell you smoked food can lead to stomach cancer, so which is worse for you, the injection of phosphates or the cooking over a wood fire???? If we followed everything we read in the media we'd starve to death.