Among the physical properties of a food product, colour certainly is one of the key visual attributes that most influence the acceptance of a product by most consumers. Moreover, this property is often related to other specific characteristics, such as texture. Based on the above, the importance of real-time access to information concerning these parameters during the production process is quite obvious. Over the last years, computer-controlled vision systems have been proposed as rapid, low-cost and non-destructive technique in an increasing number of applications, especially in the food industry. In a recent study, performed by a group of Iranian researchers (Adbollahi Moghaddam et al. 2015), this technology was used to test the kinetics of colour (by means of the parameters L*a*b*), and porosity changes in cookies of a specific type (made of wheat flour, sunflower oil, sugar and fresh cow cheese) during deep-fat frying. Even other quality parameters of the product were assessed in this study, including hardness and crust thickness; then they were correlated to the colour measurements obtained from digital images. The results show that during deep-fat frying, the colorimetric value L* (brightness) decreases, whereas the value DE /global colour change, crust thickness, internal porosity and product hardness increase. Furthermore, it was observed that changes of the variable L* and hardness followed a first-order change, while other parameters had zero-order kinetics. The activation energy of these reactions was found to be in the range of 21.20-92.86 kJ/mol, for temperatures comprised between 150 and 180°C. A good correlation was found between kinetics of colour and physical attributes (especially hardness and crust thickness). In conclusion, hence, the researchers point out that the proposed computerised vision system can reliably be used for monitoring not only the colour, but also the main physical properties of cookies during the difficult steps of their production process, as for example deep-fat frying.
References M.R. Abdollahi Moghaddam et al., Journal of Food Processing and Preservation, 39, 2015, 91-99