Factors Affecting the Color and Clarity of Casein Plastics

Abstract

Summary 1. Equipment is described and procedures are given for converting casein into plastic test strips that are suitable for accurate color and clarity measurements. 2. By extracting a rennet casein of good quality with alcohol or acetone at 140 to 150° F. it is possible to make a plastic from it with very low color and high transparency. 3. Fat contained in the casein is largely responsible for the opacity of the plastic. Fat also contributes to the color. 4. The inclusion of buttermilk in making casein is detrimental to the color and clarity of the plastic due to the increased fat content contributed by the buttermilk. 5. Riboflavin held by the casein is largely responsible for the yellow color of the plastic, especially if the casein was poorly washed. 6. Alum additions in making the plastic increase its opacity and accentuate its color. Formaldehyde curing of the plastic causes some increase in opacity. 7. Excessive heating of the skim milk from which the casein is made increases both the color and the opacity of the plastic. 8. High acidity in the skim milk from which the casein is made is detrimental to the color and clarity of the plastic, due to the poorer washing qualities of the casein, greater fat retention by the casein, and, in part, probably due to the lower ash content of the casein. 9. The incorporation of coagulated whey proteins increased the opacity of the plastic. 10. Prolonged drying or exposure of the casein to excessive temperatures are detrimental to the color and clarity of the plastic, especially so if the casein was poorly washed. 11. Incipient putrefaction of the casein prior to drying was not detrimental to the color or clarity of the plastic, but in some cases led to gas holes in the plastic. 12. The method of making rennet casein with agitation applied during the coagulation produced some improvement in the color and clarity of the plastic due to the better washing qualities of the casein and its lower fat content. The time for making the casein is reduced by this method, but there is a slight loss in yield. 13. Extraneous matter may be a source of color and opacity in the plastic.