The Department of Transport (Aviation Security Domestic Branch) has replied to my query about air travel and baby food. I asked why all baby food had to be opened at security when it was potentially dangerous (baby food should be disposed of within two hours tops). The reply says:

The liquids requirements were introduced on 6 November 2006 to comply with EU legislation and apply equally across all EU Member States as well as the USA, Canada and others.  Ready-made baby formula is not exempt from airport security checks.  Although liquid baby food or sterilised water, sufficient for the journey, may be permitted in quantities greater than 100ml, the accompanying adult will be required to verify each by tasting before they can be taken airside.  A small amount may be decanted from bottles for testing purposes.

Unfortunately, that isn’t true. The US rules are here, and in pretty much every other EU country the rules are that baby food “may” be tested – not that it *must* be tested, let alone that all of it must be tested.