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2025-02-12
The color of flue-cured tobacco leaves is an important indicator for evaluating the appearance quality of tobacco leaves. In the national flue-cured tobacco standards, tobacco leaf color is an important grading indicator. The quality of tobacco leaf color directly affects the price of tobacco leaves as a commodity. So, how to grade tobacco leaf color? This article introduces it, and friends who are interested can learn about it!
tobacco leaf
The components that affect the color of commercial tobacco leaves can be summarized into three main categories: one is the colored pigments in the tobacco leaves (such as chlorophyll), another is the cell sap pigments (such as rutin), and another is the formation of dark-colored complexes (complexes of amino acids and sugars or polyphenols, etc.). Due to the different modulation techniques and the different contents of the original and formed substances, the modulated tobacco leaves have various shades of different shades.
If we classify tobacco leaf color by the depth of yellow, the following levels are roughly included from light to dark: greenish yellow, slightly green, lemon yellow, orange yellow, reddish brown, etc. Previous studies have shown that the basic color of tobacco leaves is closely related to the chemical composition. Due to the different colors of tobacco leaves, their chemical composition also changes significantly. The content of reducing sugar and total sugar increases with lighter color; the content of ether extract is lower in lighter colors and higher in darker colors; the content of total nitrogen and nicotine increases with darker colors. The protein content increases with the increase of green content of tobacco leaves.
The color of tobacco leaves has a certain connection with their internal quality. On the basis of similar appearance quality, as the color gradually changes from golden yellow to darker, the quality and quantity of its aroma decreases, the taste becomes stronger, and the irritation of the miscellaneous smell gradually increases. Other studies have shown that in the green-yellow to lemon-yellow area, as the yellow color deepens, the aroma quality changes from poor to good, with lemon yellow being the best; in the lemon-yellow to red-brown area, as the yellow color deepens, the aroma quality tends to deteriorate; in the green-yellow to orange-yellow area, as the yellow color deepens, the aroma quantity increases, and the orange-yellow color is the most sufficient; in the orange-yellow to red-brown area, the aroma quantity decreases as the color deepens; in the green-yellow to orange-yellow area, as the yellow color deepens, the tobacco leaf miscellaneous smell decreases, the irritation decreases, and the concentration increases. In the orange-yellow to red-brown area, as the color deepens, the miscellaneous smell increases slightly, the irritation increases, and the concentration also increases slightly.
In short, from the perspective of chemical composition and smoking quality, orange-yellow tobacco leaves are the best, lemon yellow and reddish-brown tobacco leaves are slightly inferior in quality, and green-yellow tobacco and green tobacco leaves are the worst. Since color is the most intuitive factor in evaluating the appearance quality of tobacco leaves and is closely related to the quality of tobacco leaves, in order to accurately evaluate the color of tobacco leaves and grade the color of tobacco leaves, a standard light box can be used.
Evaluation of tobacco leaf color using standard light boxes
The color of tobacco leaves is not only related to the spectral reflection (or transmission) characteristics of the object itself and the observation conditions, but also closely related to the spectral power distribution of the illuminant or light source. The same object will show different colors when illuminated by different illuminants or light sources. This factor brings great difficulties to color evaluation and communication. On the other hand, there are many types of actual lighting sources, the most important of which are sunlight and lamps. The spectral distribution of sunlight can vary significantly depending on the cloud cover, season, time of day, and location. Light is an artificial light source, and there are many types of it, and their spectral distributions vary greatly. In order to unify the standards for color evaluation and facilitate comparison and transfer, CIE recommends several standard illuminants and standard light sources for color measurement and evaluation. CIE evaluates color under the lighting body or light source it specifies. These include standard illuminants A, B, C and various illuminants D such as D50, D55, D65, D75, as well as standard light sources A, B and C. In this way, color evaluation can be carried out under the lighting body or light source specified by CIE, with a unified standard.
As a professional lighting equipment, the standard light box is equipped with a variety of standard light sources specified by CIE, including D65, CWF, TL84, U30, UV, F and other light sources.
D65 light source: The color temperature is 6500K, used to simulate the CIE standard daylight light source.
CWF light source: The color temperature is 4150K, a cold white light source commonly used in American stores and offices.
TL84 light source: color temperature is 4000K, three-primary-color fluorescent light source, commonly used lighting source in European and Japanese stores.
U30 light source: color temperature is 3000K, American commercial fluorescent lamp, mainly used for shopping mall lighting.
UV light source: Ultraviolet light source with a wavelength of 365nm, used to detect items using fluorescent and whitening dyes.
F light source: The color temperature is 2856K, also known as A light source, which is a tungsten filament lamp and is commonly used in home life and window displays.
In addition, the standard light source light box also provides a standard colorimetric and color matching environment, which can be used for two main tests. One is to test the correspondence or difference between the color of the object to be tested and the color sample in the standard colorimetric card. During the test, the corresponding standard light source is used to illuminate the standard colorimetric card and the object to be tested respectively; the other is to switch between different light source environments for metamerism detection.
When users use a standard light box to grade the color quality of tobacco leaves, they only need to follow the operating instructions of the standard light box to match the color and switch to the specified light source to accurately assess the color and then grade the color quality.
