A friend was telling me when they have food brought in for meetings they almost need an armed guard to watch it. Once they left a food cart in the hall right outside the meeting room. The food was to be brought in after the presentation to the guests. The mayor was in attendance, the media and local celebrities. The Chairman announced at the end of the presentation that refreshments and goodies would be brought in. When they went to get it from the hallway the trays had been picked clean.
Just because there is food on a tray doesn't mean it is meant for you. Always ask before helping yourself. As in my friend's example, it could be very embarrassing to your organization.