When you are asked (on a piece of paper or on a screen) if you have any food, fruit/veg, plants or their parts, say yes. Same for meat. When you reach the person, you will be asked in a very bored voice "What food do you have?" (I know because I ticked yes to that after having visited a farm the previous day, and that's what I was asked, leading to a lot of confusion.)
The officer will then make a decision and either take your food or let it through. Beef is generally taken including roast beef sandwiches and beef jerky. But not all food will be taken. On another occasion there were a whole pile of apples abandoned just before the pre-clearance and I asked about it. "I don't have an apple," I told the officer, "but are they banned?" "Nope." [this was years ago and they might be now, not the point.] "So why are there all those apples out there?" "People think they are banned and ditch them. They don't come in here and ask me."
If you fail to declare food, especially meat, when entering either Canada or the US, you could be fined hundreds of dollars. Declare it. Alternatively, buy yourself some cleared and legal food in the airport after pre-clearance.