5.7 PROCESS DEVELOPMENT

Process development is interwoven with product design. For example, in the Thai sausage example a standard fermentation process was chosen for the Plackett and Burnam experiments, and then in the later studies on the starter cultures, the processing variables of temperature and humidity were also studied during fermentation. The Thai sausage processing was divided into three parts: raw material preparation (mincing of meat, cooking of rice), mixing of the raw materials and stuffing into the sausage casings, and fermentation. The first two parts were kept standard throughout and only the fermentation conditions were varied.

This division of the process into its individual parts is the method used in either analysing a current process for a new product (process analysis) or for building a new process for a new product (process synthesis). The individual parts and then the connections between them are studied to give the optimal overall process. There are three aspects of studying processing: unit operations, unit processes and processing limits:

      Unit operations. These are the physical processes such as heating,
            pasteurisation, sterilisation, freezing, chilling, drying, mixing,
            emulsifying, tumbling, pumping, conveying, packing.
            They can be grouped into separation processes, assembly (or
            combining) processes, conversion processes and preservation
            processes. There are more than a hundred unit operations used
            in food processing.

      Unit processes. These are the chemical, biological and microbiological
            changes such as gelatinisation, hydrolysis, oxidation, browning,
            protein denaturation, vitamin destruction, destruction and growth
            of micro-organisms, fruit ripening and meat tenderising.
            There are a number of these reactions occurring together in a
            food process and this leads to a complicated study in design.
            In the past much of the knowledge was empirical, but gradually
            basic quantitative studies of the rates of these reactions are leading
            to more directed process design.

      Processing limits (maximum and minimum). These can be
            temperatures, rates of increase/decrease in temperature, viscosities,
            mixing speeds, shear rates and pH, as well as processing times,
            availability and cost of equipment and services such as water
            quantity and steam pressures.