Browning during

Note The colors of the chromatogram zones produced by the mandelonitrile glycosides change with time Those of the D-isomers turn steel blue within an hour, while the 1 isomers turn reddish-brown during this time. It is possible to distinguish between D-and L-forms on the basis of these typical color differences and color changes. Both isomeric forms have a dark brown color after about 24 hours. 

Colorless oily liquid that is light and moisture sensitive. Becomes brown during storage due to liberation of iodine. 

The bottom third of the tube was immersed. The reaction mixture changed color from blue-green to brown during this period. 

Urine may turn red-brown or dark brown during drug therapy... 

Figure 2. Formation of browning intermediates (Amadori compounds corresponding to peak C in Figure 1) and browning during air drying (110 "C) of carrot cubes. Key O, water content related to dry matter 0, product temperature , formation of Amadori compounds (mol %) and A, browning (excitation wavelength 420 nm).

Figure 7. Increase of browning during air drying of the carrot variety Bauer s Kieler Rote dependent on water content and air temperature. Key A, 60 °C 0, 90 °C O, 110 °C dashed line 1, limit of detectable visible browning and dashed line 2, quality limit relative to browning.

Baron, R., Mayen, M., Merida, J., and Medina, M. (1997). Changes in phenolic compounds and browning during biological aging of sherry wine.. Agric. Food Chem. 45,1682-1685. 

The preparation of reaction flavours is known to be improved by the presence of phosphate in the reaction mixture. The enhancing effect of phosphate on the rate of browning during the reaction of glycine with several hexoses has already been shown by Swimmer et al (11). 

Figure 13.1 Formation of browning intermediates and browning during air-drying of carrot cubes (air temperature = 110 °C). Reproduced from Eichner and Ciner-Doruk511 with permission from Elsevier.

I. Tosun and N. S. Ustun, Nonenzymic browning during storage of white hard grape pekmez (Zile pekmesi), Food Chem., 2003, 80, 441 143. 

Fluorides are readily translocated to the tip and margin of leaves in the transpiration stream. If atmospheric levels of HF are low enough, the intercostal injury will not develop, and the fluoride concentration will increase at the periphery of the leaf. Acute fluoride intoxication at the margin of dicotyledonous plants, according to Solberg et al. (18), is first characterized by a collapse of the spongy mesophyll and lower epidermis, followed by distortion and disruption of the chloroplasts of the palisade cells, and finally, distortion and collapse of the upper epidermis. The injured area soon turns brown during hot, dry weather, but this symptom may be delayed if the weather is cool and damp. 

Development of browning during ripening, fermentation, and/or aging process... 

Table II. Effect of phenolic compounds added to a casein solution on its browning during incubation ...

In order to retain the light colour, ascorbic acid can be added to the juice immediately after pressing. If some of the fruit used is unhealthy, the ascorbic acid should already be added in the mash, to prevent browning during processing. 

The acyl compounds (2g) are heated with a mixture of 98% formic acid (12 ml) and 30% hydrogen peroxide (6 ml) at 100°C (10-15 min). The solution changes colour to yellow or brown during this period. Dilution with water arid neutralization with concentrated ammonia solution precipitates the benzimidazole (68). Extraction of the filtrate with chloroform can increase the yield. 

The most widespread hare in North America is the snowshoe or varying hare (Lepus americana), which occurs from the low-arctic tundra, through much of the northern United States. This species is dark brown during the summer, but is a camouflaged white in winter. This species goes through more-or-less cyclic variations of abundance in northern parts of its range, which are tracked by the populations of some of its predators, such as lynx (Lynx ri s). 

In the third experiment of this series potassium (20.1 mmol) and naphthalene (3.10 mmol) in tetrahydrofuran (50 mL) were allowed to react for 4.5 hr. Coal (0.860 g) was then added. The reaction mixture immediately became brown. During the next several days the reaction mixture changed color as the reactions proceeded. Aliquots free of potassium but containing solid coal particles were withdrawn from this mixture and titrated to determine the extent of conversion of the coal to the coal polyanion. In certain instances aliquots free of potassium and solid coal particles were withdrawn from the reaction mixture and titrated to determine the extent of conversion of the solid coal to soluble anionic substances. The reaction was allowed to proceed for 5 days at ambient temperature under argon. An aliquot of the mixture was then withdrawn to establish the extent of the reaction. The results are shown in Figure 1, Curve C. 

---