You will need to consider the different ways to go about this.
You can work with a Consultant (there is a post where their services are advertised “Need Formulating Services, Here are some Contacts.”). Working with a Consultant may offer you some increased input into the process and as a start-up, it will be helpful to own the Intellectual Property (IP). The downside of this process is that you will still need to source out packaging, graphics and manufacturing sources, but most Consultants can point you in the correct direction.
Alternatively you can work with the R&D Department of a Contract Manufacturer (CM). You may have less input as generally your interactions will be with the front office. However, if you are funded for this scenario, they will source out all the services. If owning the IP is important to you, ask the CM about this early on.
More important is doing a real inventory and evaluation of you Business model. I see far too many entrepreneurs who under estimate the cost and complexity of the R&D process. Also, if you are a Business person, your time is best spent in developing the Marketing, Sales infrastructure and Social media. You need to look at your strengths.
Also, get some real World costs in regards to the overall process. I see far too many people come in under funded. This will cause your business to fail or in a best case scenario move slowly until you have sufficient funding.
Good luck and I wish you all the luck. It can be a rewarding process.