Advanced panel training on visual Gestalt evaluation of biocrystallization images: ranking wheat samples from different extract decomposition stages and different production systems

ABSTRACT Biocrystallization images are formed in reaction with foods; in the course of the evaporation of the water from food extracts in presence of copper chloride, crystalline structures are formed. The structures are known to reflect food quality, such as degree of decomposition. Individual expert evaluators have suggested that crystallization images of samples from organic production contain fewer signs of decomposition and that this feature can distinguish organic foods from their conventional counterparts. To further assess the scientific merits of this methodology, a panel of nine evaluators was trained in the visual assessment of biocrystallization images and asked to rank the visual Gestalt decomposition level of encoded images of wheat extracts from i) the same production system at five different decomposition stages and ii) organic production systems vs. conventional production systems aged for the same amount of time. The panel was trained by supervised classification on the basis of defined criteria and intra- and inter-personal variation was assessed. Statistical evaluation showed that the panel was highly reliable, and that the method was appropriate for ranking biocrystallization images of five different decomposition levels. Furthermore, images of samples from organic or conventional production systems could be distinguished with high agreement according to their Gestalt decomposition level with fewer signs of decomposition in the images of organic samples. The rank order between the organic systems vs. the conventional systems was significant.