Do you have a budget ?
(why would I ask such a silly question ?)
Playing around with arduinos is one thing, making a food or beverage processing plant is a whole different animal, IMO, in that normally it would be sufficient to keep a count and store it in a variable but it the case of your application I would recommend you design a controls panel an implement multiple I2C (or even parallel) lcds that display the running count up or down of different processes that are under way. In addition I would recommend implementing an EMO button (the standard slap to turn off type that are available in many places, Grainger just to name one. I would recommend you use thermocouples for monitoring the temperatures and have those on dedicated displays as well. Adafruit sells an MCP31855 Breakout bd (I have one) that works reliably). You might even consider (I would recommend) some kind of hardware interlocks that are independent of the uC.
Running heaters involves levels of current that you would probably want to monitor. Sparkfun sells an INA169 current shunt that may work for your application but I don't know without seeing the schematic or specs for you heater. Additionally I would recommend the use of Light Towers to indicate process status of the different control steps. You might also consider implementing a loud piezo alarm to signal an alarm state for something seriously wrong involving heater , temperature or current.
I haven't looked at your code but I don't have a whole lot of programming experience so probably my contribution will be limited to hardware related issues/questions. I will look at it but don't expect anything.