Complex sentence: Maltodextrin is a highly processed food substance typically derived from hydrolized corn starch, so if a processor leaves the gluten in (only way for MSG to enter the mix), the hydrolyzing creates amino acids (including glutamate) in trace quanitities.
Split into simpler sentences: Maltodextrin is a highly processed food substance typically derived from hydrolized corn starch. The only way for MSG to enter the mix would be if the corn starch contains trace proteins which also get hydrolyzed, creating amino acids like glutamate in trace quanitities.