I initially read madeofpalk's comment (https://news.ycombinator.com/item?id=14940680) as it seems that you might have, so that it seemed to say that the supposed security agent was not actually a security agent; but a second reading suggests that the meaning is instead that, in addition to being a security agent, the person in question was a Regular Person, and had a sense of humour.
Repeated readings still do not reveal whether an Australian security agent referring to something as his "bread and bitter" is a typo or intentional. :-)
It's derived from the continental "existentialist breakfast" of a black coffee, cigarette, and Aspirin–but had to be adapted due to the bad availability of commercial products in the past, as well as the higher activity levels the Australian bush requires and the resulting danger of a breakfast completely devoid of calories.
But the joke is most definitely not "on you". As in: It wasn't meant to expose anybody's shocking lack of knowledge of arcane Australian trivia.
Turns out the security officer was just a Regular Person, claimed deodorant cans are his "bread and bitter" and had a little chuckle as he found it in my toiletries bag.