Energy prices themselves would be a completely higher order of magnitude on the impact on food prices than the carbon price itself. In fact, the increase in energy prices charged by energy producers, including those in Canada on Canadian energy charged to Canadian consumers—which has nothing directly to do with what's happening in the Middle East—means that the impact on food prices was 30 or 40 times greater than the direct impact of the carbon price.
The other point to remember is that even that 30¢ on the $100 estimate is really telling only one side of the story. That is based on tracking the carbon price through the input chain into all of the different factors that end up in the consumer's final basket, but the whole point of the carbon price is to encourage changes in behaviour, to shift towards renewable forms of energy and to conserve energy, both of which will have offsetting impacts on final prices.
Some of the studies internationally that have looked at the overall economic effects of carbon pricing on the whole price level and not just on products that use fossil fuels intensively suggest that there is no net impact on the overall consumer price index or potentially a slight deflationary impact because of the benefits of strong investments in renewable energy on energy costs and energy supply.
If anything, I think that number you threw out is probably too pessimistic and, on a net basis, the impact on food prices will be nothing, if not, in fact, negative.