The Influence of the Used Bleaching Earth on the Content of Natural Dyes in Hemp (Cannabis sativa L.) Oils

Abstract

Cold-pressed hemp oils are characterized by an intense color, which is undesirable when used directly. Therefore, research was undertaken on removing chlorophyll and carotenoids effectively. This publication presents the results of tests that verified the adsorption properties of seven bleaching earths (BE1–BE7) in two doses (2.5% and 5.0%) in the low-temperature bleaching process of hemp oils. These oils were obtained by cold and hot pressing of the seeds of three varieties of hemp (Cannabis sativa L.): Finola, Earlina 8FC, and Secuieni Jubileu. The color change and the content of carotenoid and chlorophyll pigments in the bleached oils were verified using the colorimetric method (CIE-Lab). The BEs used had different abilities to reduce the content of natural dyes connected with oil decolorization. The conducted research allowed us to characterize the influence of BEs on the organoleptic properties of the tested oils. Hemp oil obtained from the Secuieni Jubileu CP and HP hemp variety should be bleached with unmodified magnesian bentonite at 2.5%. Unmodified attapulgite clay is not recommended for this variety, as it strongly adsorbs carotenoids from the oil.