Assessment of Control Strategy for 500W Retort

A retort is a steam operated “pressure cooker” which is used in the food industry for sterilization. The 500W retort is a lab-size unit donated to the California State University, Fresno Food Processing Laboratory by the FMC Corporation in the summer of 1998. This retort was developed two decades ago and intended for small batches and versatile food containers such as jars, pouches, cans, and bottles. The unit allows Fresno State faculty to interact with industry and provides a hands-on opportunity for students. It is ideal for teaching thermal processing, sterilization, food safety, FDA regulations and food laws. Faculty may use it to conduct research for a variety of food products and for packaging effectiveness. The retort breeds new ideas for automation technology and enables faculty and students to develop insights into retort technology. Food science students have the opportunity to gain understanding of automation technology, while technology students can learn about issues regarding food safety and processing regulations and parameters. This unit was designed for manual operation and data acquisition. It is not only tedious and time consuming to collect data, but also awkward to operate. Particularly, the retort involves the use of steam; therefore it is desirable to automate the unit with modern technologies. Since there exits a broad range of automation technology with various degrees of sophistication, it is important to assess the strategies required to automate the control system for given constraints, i.e., practicality, budget, user friendliness, migration path, etc. This paper first describes the basic retort operation and provides an overview of control technology. Programmable logic controller (PLC) technology is then presented in terms of the retort application. The following section explains a popular PLC enhancement technology – HumanMachine Interface (HMI) for its ability to provide continuous monitoring on a personal computer. The implementation of retort control is assessed accordingly. Finally, the emerging embedded control technology is introduced to shed light on future food processing controls.