Within Food R&D scientists, chefs and engineers aim to develop natural fruit and vegetable based soups with optimal flavour, texture, appearance and health benefits whilst maintaining product safety. The colour and appearance has a major influenceon the perceived quality (e.g. nutrition and freshness). This paper describes a methodfor the determination of the colour of soups containing vegetable particles. Digitalimages were made under controlled lighting using a DigiEye imaging system. It allowsdocumenting the appearance by making colorimetrically accurate images which aresuitable for the measurement of colour uniformity, size and shape. The uniformity of thelight under diffuse and directional illumination was investigated using different targetsand soup samples. For accurate colour analysis the images have to be corrected fornon-uniform illumination and the colour has to be measured at a fixed location outsidethe centre of the lighting cabinet. Directional illumination (angled light with additionalmirrors) was used to introduce gloss resulting in images matching the actual appearanceof soups and vegetable particles very closely. Imaging glossy soups under diffuseillumination resulted in dull images with dark spots. No significant difference was foundbetween the colours of soups analysed under diffuse or directional illumination. Underdirectional illumination a better repeatability was observed. Additionally, for 36 differentsoups, the measured results from the DigiEye system were compared to two differentcolorimeters (0°/45° and diffuse/0° geometry). Linear relations were found betweenthe CIE Lab values measured by the DigiEye system and those measured by two differentcolorimeters. Best correlations were obtained between DigiEye and 0°/45° colorimeter(r2=0.980-0.996). The short term precision of the DigiEye system is somewhat betterthan those of the colorimeter.
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