Homegrown ingredients = poor food quality?

I've been wondering about this for some time, I decided to spice up my sims' meals with ingredients they have planted on their own. However, every time I do this, the quality of the food always ends up poor, and it doesn't matter if my sims' cooking skills are maxed out. Is this some sort of bug, or isn't "normal" quality on the homegrown ingredients good enough?