Colour value

Colour value of wash liquor Fastness to washing... 

Colour value given by 1000 E/d, where E is extinction at the peak wavelength (W nm) and d mm is the cell thickness... 

The discovery in 1979 of the benzodifuranone chromogen (1.14) and its exploitation in red disperse dyes for polyester fibres [23,24] emerged from ICI research towards new chromogens of high colour value, brightness and substantivity to overcome the relative weakness of anthraquinones and dullness of monoazo alternatives in the red disperse dye area. A striking improvement in build-up properties was found by introducing asymmetry... 

Table V. Hunterlab colour values (L=lightness a= +red, -green b +yellow, -blue) of flours, dry and wet processed products from dehulled field pea and fababean.

The aqueous reagent is stable at room temperature and the reaction proceeds quickly without requiring heat. The method is approximately ten times more sensitive than the ninhydrin method and is particularly useful when the quantitation of many amino acids is being carried out using amino acid analysers or HPLC. However, the fluorescent yield of individual amino acids varies and fluorescence values must be determined for quantitative work in the same manner as the colour values for ninhydrin. 

The content of colouring matter reduces during storage. Under the most careful storage, the ground paprika loses from its colour value 0.1 g/kg per month. This process can be delayed if the product is stored at or below a temperature of +5°C. 

Species Colour values of raw material Colour values of oleoresins Remarks... 

After extraction of the whole paprika, including seed and stems, the obtained colour-value of the extract is relative low, about 350 to 500 ASTA, but the extraction yield can reach 15 to 17 wt.%. High-quality Hungarian paprika species like Sweet Paprika Excelsior give an extract with a colour value between 1,500 and 1,800 ASTA, and a good flavour profile. 

Paprika pericarp from Spain or South Africa have initial colour values of 200 to 240 ASTA, and extracts with 2,500 ASTA and more can be obtained. 

With CO2 extraction it is possible to produce colour extracts up to 3,000 AST A from Indian chili. These extracts still contain 2 to 2.5 wt.% capsaicin, which can be removed in a second CO2 extraction step, if desired. The result is a high concentrated colour extract with a colour value up to 5,000 AST A and more, and a highly pungent fraction containing capsaicin up to 20 wt.%. Such extracts are produced, for example, in a multi-purpose plant at Novo Agritech near Hyderabad, India. 

As can be seen from Fig. 9.6-10 low pressure gives a poor yield, especially of capsanthin, the coloured fraction of paprika. The colour value is only about 1,370 ASTA (54,800 CU), or about 48% of initial capsanthin content. A higher extraction pressure like 500 bar allows a depleting yield of capsanthin. 

With a two-step separation it is possible to enrich the colour fraction in the first step, and to obtain most of the aroma fraction in the second separator, with a colour value of about 200 to 300 ASTA. The conditions in the first separator should be 220 to 230 bar and 40°C. 

Sankari et al. (2000) conducted a study on the per se performance of individual progenies of F3 generations of the cross Ramanathapuram Local X Jalapeno hot pepper with respect to oleoresin and related constituents. Oleoresin content ranged from 9.1 to 11.5%, with a mean value of 10.6%, along with variability in colour value. 

The colour value of the extract is mainly dependent on raw material. Between 400 and 700 bar we got the same colour value for the same raw material, but the extraction time or the C02 throughput can be reduced up to 50% with increased extraction pressure. 

Species Colour values Raw material colour values Oleoresins Remark... 

Table 2. shows extract colour values obtained from different raw materials... 

All raw materials were extracted between 500 bar and 700 bar, with an extraction temperature of 60°C for all paprika tests. After an extraction time of two hours a colour value of 20 - 25 ASTA remains in the residual, whereat this value was nearly independent from extraction pressures. 

Figs. 5—8 show the effect of the change in centrifugation efficiency for the time of centrifugation unchanged (2 minutes) on residual colour values and aggregated coagulant ratio a. ... 

To plot colour values on a two-dimensional system it is necessary to have only two co-ordinates. With a tristimulus combination this can only be achieved when the values add up to unity so that if X and Y are defined the value of Zis 1 — (.iV-l- T). The proportions of the imaginary stimuli in a colour can be made to add up to one by converting them into the so-called chromaticity co-ordinates ( , y, and z) by the following treatment ... 

The dominant wavelength is determined by extending a line drawn from the point of equienergy white, through the situation of the colour value, until it reaches the spectral loci curve, when the point at which it crosses... 

From a consideration of the colour solid it is apparent that there is a maximum possible luminous reflectance or transmission for any specific colour value. The gamut of possible colour values diminishes as the Y value approaches 1, and a few discontinuous steps in the relationship between chromaticity and maximum luminance with standard source Sc are shown in Fig. 26.18. An interesting feature is that the highly saturated reds, yellows, and oranges situated near the spectrum loci boundary in the... 

All grades have a colour value (Hazen) of 20, by ASTM D1209, an acid number (AN) of 0.03, by ASTM D974, a water content, ppm, of 40, by ASTM1744, and a Conradsen residue (percentage residue) of < 0.01, by ASTM D189. 

Colour fading from pigment oxidation in fresh meat, the effect of illrrmination on the appearance of orange juice, the effects of varying coffee and milk concentration on coffee appearance and measuring breakfast cereals by grinding to a defined particle size are given as examples of the types of problems encountered in food colour appearance measurement. The effect of the illuminant on the calculated CIELAB colour values for a variety of food spectra is also presented. 

On-line use of colour measurement is likely to increase especially where the colour values obtained by the instrument can be incorporated automatically into... 

It can be seen that, in all except the last two cases, the colour values of the standards are traceable, via the working and master standards, back to the primary standard. 

The choice of the remaining instramental factors, such as measuring geometry and the relative sizes of the specimen viewing area and the illuminated areas, are very much influenced by the optical classification of the specimen. In order to determine the colour values of a product, therefore, it is necessary to... 

The effects of some of these preparative factors - dilution, test temperature and time, presence or absence of a black cover - on the colour values of tomato pastes have been discussed by Brimelow (1987). As already noted, MacDougall... 

---