In Japan artificial colors and pigments can be used for food packages if they are processed so that the artificial color or pigment will not be eluted to contaminate food. Ten samples of cardboard and five samples of wrapping paper were subjected to the elution test. One hundred cm2 of cardboard or paper was immersed in water at 40 C and held for 30 min. Artificial color was eluted from all samples of whole cardboard and, when it was divided into three parts (surface, inner part and reverse side) to do the elution test separately, artificial color was eluted from all parts except with one sample when color was eluted only from inner part. By comparing Rf values on a paper chromatogram as well as its maximal absorbance with color standards, the eluted color was identified to be croceine orange. Congo red and croceine orange were eluted each from one sample of wrapping paper.

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