Engineering is not something optional but essential to the design and construction of a food factory or for that matter everything. It is not a cost, but an investment that will save money in all the other investments in equipment and services.
To construct a new food factory, or to expand or upgrade an existing factory, is the need of your business. Engineering converts that need into a complete description of the entity and contains all the information required to build the entity. Without engineering, you will build something you don't fully understand.
The real question isn't, do I need Engineering?
Rather, am I ready to risk all of my investment just to save the cost of Engineering?
Engineering is the difference between Chaos and Excellence. If you are going to do it, you should do it right.