In-line Optical Measurements for Process Control in Food Industry

Process control requires measuring the status of the parameters that determine the output of the procedure in order to integrate those actions required to maintain the process within the limits that ensure the desired output. There has been a push to access to reliable and cheap sensor techniques that provide the required information to feed the process control, fleeing from the laborious off-line analysis that usually are costly, time consuming and, in many cases, inefficient. In-line measurements allow for a fast actuation in the process to optimize it and/or keep it under control. There are many physical, electrochemical, or optical sensors in the market that can provide continuous readings of relevant parameters that are linked directly or indirectly with the efficiency of the process or the quality of the final product, but many other critical processing parameters are calling for development of adequate and efficient in-line sensor technologies capable of providing the required information for either process optimization of control.
In this talk we will review the advantages of optical methods that are suitable for in-, on- or at-line monitoring, do not require sample preparation and are sensitive enough. These process analytical technologies (PAT) can be applied to estimate quickly and accurately any deviation from the specified values, allowing for the rapid action/decision-making at real time processing. Some optical parameters based on light scatter, transmission, and fluorescence spectrometry, measured at different spectral regions, can be used during food processing to measure the concentration of key chemical compounds, or correlating with the technological parameters of interest through different chemometric tools. Quantitative and qualitative applications developed by Professor´s Castillo team include methods for the prediction of curd cutting time and firming, both for rennet and acid induced milk coagulation, modelling the syneresis of the curd to optimise the whey drainage process, or characterise the thermal load of a pasteurized/sterilized milk. More recently, the research scope has opened to include optical sensor applications on meat and food emulsions.