Just declare any food - have it easily available - show it without hesitation. Most things will be "OK'd" and you are on your way.
Customs are very used to flights arriving (in particular) from the countries north of Oz with "no food" declarations and then they discover all manner of things. This takes time and pushes the tolerance of Customs guys.
If you have minimal luggage and no declarables, look out for the roving Customs guys in the baggage hall. They take the load off the guys at the exits and may be able to stamp your card and hasten your exit (ie by-pass the line ups for baggage x-rays).