This collaborative study was conducted to determine the total monomeric anthocyanin concentration by the pH differential method, which is a rapid and simple spectrophotometric method based on the anthocyanin structural transformation that occurs with a change in pH (colored at pH 1.0 and colorless at pH 4.5). Eleven collaborators representing commercial laboratories, academic institutions, and government laboratories participated. Seven Youden pair materials representing fruit juices, beverages, natural colorants, and wines were tested. The repeatability relative standard deviation (RSD_r) varied from 1.06 to 4.16%. The reproducibility relative standard deviation (RSD_R) ranged from 2.69 to 10.12%. The HorRat values were ≤1.33 for all materials. The Study Director recommends that the method be adopted Official First Action.

Replacement of artificial food dyes with natural colorants is a current marketing trend, notwithstanding the fact that neither the United States nor the European Union (EU) has defined natural with respect to food colors. Consumer groups have concerns over the safety of synthetic colorants, and in addition, many of the naturally derived colorants provide health benefits. Food scientists frequently have the assignment of replacing artificial colorants with natural alternatives. This can be challenging, as naturally derived colorants are usually less stable, and all desired hues might, in fact, not be obtainable. In this review, the chemical and physical properties, limitations, and more suitable applications for those colorants that are legally available as substitutes for the synthetic colorants are summarized. Issues and challenges for certain foods are discussed, and in addition, colorants that may be available in the future are briefly described.

Food scientists who establish quality control specifications for their product are very aware of the importance of color and appearance. While subjective visual assessment and visual color standards are still used in the food industry, objective instrumental color measurements are extensively employed. This chapter provides a brief description of human physiology of vision and an overview of the different color-ordering and color-measuring systems. Included are the CIE tristimulus system and tristimulus colorimeters, with coverage of the Hunter Lab system, the CIEL*a*b* system, and the L*C*H* system. Also covered are sample preparation and presentation to get measurements that are repeatable and that correspond to visual appearance. The chapter is limited to presenting the basic underlying principles that allow for an understanding of how color of food products should be measured.