Many consumer studies have shown that visual acceptance is extremely important when making choices in foods. Food color is so influential it can even change the way people perceive taste and quality in foods. Color analysis is done in different steps in the process from the ripeness of a crop, during on-line process monitoring to final product quality analysis.
Since visual color judgments can be affected by a wide variety of factors, from plant lighting conditions and angle of observation to individual differences in color perception, a spectrophotometer to measure color provides a subjective and consistent method of color quality control.
Opaque foods, such as fruit, crackers, corn flakes, cheese puffs, flour, tomato juice, cheese and meat, are seen wholly by reflected light. The most difficult aspect of color sampling of opaque foods is the presentation of the sample to the light path. Often readings are taken at different angles and then averaged out.
Translucent foods such as fruit juices, jams and custards are seen partially by reflected light and partially by transmitted light. Translucent foods are typically in liquid or semi-solid form and sampling requires special handling. The color of a translucent sample will change when the light path length through is changed. Thus, the path length must be fixed with a fixed white background.
Transparent foods are typically liquids or semisolids such as clear juices, tea, wines, jellies, gelatins, vegetable oil and soft drinks are seen wholly by transmitted light. The products are poured into a transmission cell for sampling. The sample cell is then placed against the sphere port in the transmission compartment of an instrument.