A spectrophotometric method for the evaluation of vegetable oil colors

Abstract

Summary A means for evaluating oil color on the basis of an optical density measurement at 500 millimicrons has been proposed. The amount of chlorophyll would be taken into account by present methods or an adaptation of these methods. The advantages of the proposed means of evaluating oil color are that it expresses more exactly the amount of color in the oil, provides a more accurate estimate of color removal during bleaching, and makes possible more exact evaluation of bleaching earth. Data have been presented on the color value (Optical Density × 100) of refined and bleached oils, possible variation in value obtained from different laboratories, estimation of color removed during bleaching, evaluation of bleaching earth, and relationship between color of refined and bleached oils prepared in the laboratory by the Official Method.

The Color of Olive Oils: The Pigments and Their Likely Health Benefits and Visual and Instrumental Methods of Analysis

“…Besides, the color matching by these means is rather imprecise and is very dependent on the observer. It is commonplace that different observers match the same sample differently and that the same observer matches the same sample differently when the test is repeated (Presnell 1949; Naudet and Sambuc 1955; Pohle and Tierneh 1957). On the other hand, in relation to the impact of color in the sensory analysis of olive oils, in general, a recent study concludes that the objective intended when using blue glasses for the oil tasting, which is to conceal the color so it does not influence the sensory assessment of aroma and taste, is not fulfilled.…”

“…The most serious of them is related, evidently, to the presence of a negative factor in the equation, because, when the oils are green, this is so considerable that a negative red Lovibond is obtained. Put otherwise, the oils would have an unreal color (Naudet and Sambuc 1955; Pohle and Tierneh 1957).…”

Food

“…A device for continuous measurement of ultraviolet light absorption of eluent from columns used to chromatograph a commercial food dye permits the determination of residual 2-naphthylamine (79). A measurement of absorbance at 500 µ has been proposed as a more reliable index of the color of edible oils (279). Forward-scattering at an angle of 20°with respect to the incident light beam has been shown to increase the sensitivity of the turbidity measurement on commercial sugar solutions (SOI).…”

Relation Between Visual Color Differences and Tristimulus Color Readings for Pureed Carrots, Spinach, and Pears

“…Others have developed a Z-dimensional concept (Smith and Huggins, 1952) and a 3dimensional method (Yeatman et al, 1960) of expressing colors of tomato products by a single figure. Several other formulas have been" developed for tomatoes (Kramer, 1950), apples (Francis, 1952), flour (Croes, 1961), sugar (Deitz, 1956), ~grapefruit (Lime et al, 1956)) oils (Pohle and Tierney, 1957), beer (Stone, 1954)) and many other foodstuffs.…”