Color loss

The structure—N/C-coated cellophane/polyethylene/aluminum foil/ adhesive/50ga polyester/adhesive/polyethylene—had a shelf life of over 6-9 months with no moisture, flavor, or color loss. This barrier system contained the product successfully (see Table IV). 

Weemaes, C.A. et al., Kinetics of chlorophyll degradation and color loss in heated broccoli juice, J. Agric. Food Chem., 47, 2404, 1999. 

Most published data deals with model solutions to assess the major factors influencing betalain stability, among which pH and temperature are most frequently addressed. Until recently, total color loss was assessed by spectrophotometric monitoring of the decline at the wavelength of maximum absorption. To predict color fading over time, kinetic data were derived therefrom, most often obeying first-order decay principles. 

The third group of colorants consists of the color additives used to improve appearances of food products. They reinforce the colors already present in foods and ensure uniformity of appearance from season to season and batch to batch. They also add color to virtually colorless foods such as sherbets and provide dramatic color to fun foods such as candies and hohday treats. " Color additives are also used to compensate for color loss during processing and transportation and ensure desirable appearance. ... 

On Reproduceability from the Photopolymer Plate to Paper-Mold The images in a negative film can be reproduced with good fidelity. Presently used zinc plates, because of their suspected low color loss, show a less fidelity compared with photopolymer plates, but their reproduceability are very similar as shown in Table 2. 

The comparison of reproduceability of diameters of dots in the highlight areas between the Photopolymer Plate and zinc plate from a negative film, showed 90-95% for the Photopolymer Plate and about 75% for a zinc plate because the latter showed color loss. (See Fig. 15)... 

Methods. A typical hydrogen peroxide bleaching operation consists of treatment of a 20% HPL solution in 60-75% aqueous ethanol with 25-50% hydrogen peroxide (by weight) on lignin derivative at 80°C. The reaction medium is adjusted to pH 2 by the addition of HC1, or to pH >12-13 by NaOH. Color loss is determined by UV/VIS absorbance measurements on suitably diluted samples. 

Absorbance was measured at 25 nm intervals from 325 nm to 500 nm. These values were converted to absorptivity (L g-1 cm-1) and the area under the curve was integrated from 350 nm to 500 nm using software by PolyMath Control Data ( 1984). This value was compared to corresponding values obtained with the starting material (lignin or HPL), and the color loss was calculated from... 

Similar calculations were done using seven individual wavelengths between 350 and 500 nm (i.e., at 25 nm intervals) and, using the sum of the absorp-tivities at the 7 wavelengths, color loss was computed from... 

COLOR LOSS BY INDIVIDUAL WAVELENGTH METHOD (% OF STARTING MATERIAL)... 

Figure 2. Relationship between color loss by the integration method as compared to that by the individual wavelength method selected values of several lignin types 350 nm (0) and 500 nm (A).

Figure 3. Relationship between color loss and H2O2 consumption and H2O2 charge.

Figure 4. Rate of color loss for HPL derivatives from red oak organo-solv lignin (A), aspen organosolv lignin (B), pine kraft lignin (C), hardwood kraft lignin (D), and spruce organosolv lignin (E). (ON stands for overnight.)...

Figure 5. Relationship between color loss and initial pH. (Note Conditions were 80°C, 95% H2O2 per HPL, and 30 min. reaction time.)...

An amount of 25-50% hydrogen peroxide per lignin derivative constitutes a reasonable compromise between maximum color loss and efficient peroxide use. This achieves a color loss of about 60% on lignin, if color is defined as the weighted absorptivity average in the range of 350-500 nm. 

Figure 10. Color loss of lignin derivatives in relation to method of modification and blocking of phenolic OH groups.

While more than 90% of color loss is achieved after 30 min. in homogeneous phase at 80°C with some lignin preparations, others, especially softwood lignins, take longer. 

JA Osuna-Garcia, MM Wall, CA Waddell. Natural antioxidants for preventing color loss in stored paprika. J Food Sci 62 1017-1021, 1997. 

The benefits of GA applications to lemons are a more desirable seasonal harvest pattern in relation to market demands, a larger percentage of fruit with a long storage life, and a decrease in the number of small fruit (6). Applications of GA to Clementine mandarins significantly delayed fruit coloring, loss of acid, and an increase in soluble solids (40). 

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