Red cabbage extract

Dyrby, M., Westergaard, N., and Stapelfeldt, H., Light and heat sensitivity of red cabbage extract in soft drink model systems. Food Chem., 72, 431, 2001. 

When red cabbage is boiled in water, pigments called anthocyanins are extracted. These pigments can be used to indicate pH. In this laboratory exercise, you will observe the color of red cabbage extract as a function of pH, match each color with a color in the color palette of Microsoft PowerPoint, and, using Microsoft PowerPoint, present your findings to the class. You will work in groups of two or three for this activity. 

FIGURE 15.10 Red cabbage extract is a natural pH indicator. When the solution is highly acidic, the extract gives the solution a red color. As the solution becomes less and less acidic (more basic), the color changes from red to violet to yellow. 

Plant extracts. Various plants contain natural dyes which resemble acid-base indicators. Actually such extracts have little practical value because the dyes as a rule are very impure and their alkaline forms usually undergo decomposition. L. E. Wai.,-BtJM has recommended the use of red cabbage extract, which possesses an interval at 2.4 to 4.5, from red to green. 

No irrformation is given in the literature on processing and colour loss caused by convention of flavonoids, anthocyarrins and betalains. However, in the food colour industry, the colour of red cabbage extracts was stabilised by adding water-soluble antioxidants and phosphates to the extracts (Washino and Moriwaki,... 

Many natural substances are acid-base indicators. The most familiar one is litmus, an organic dye extracted from certain lichens. Litmus turns from blue to red in acidic solutions (< pH 7) and from red to blue in basic solutions ( pH 7). Some other natnral indicators include red cabbage extract, blueberry juice, black tea, beet juice, rhubarb, and tomato leaves, and flowers such as the rose, daylily, blue iris, and purple dahlia. Red cabbage extract undergoes sharp changes of color at several pH values. The deep purple color of red cabbage leaves is caused by a mixture of water-soluble... 

The pH scale is a convenient way to represent the acidity or basicity of dilute acid and base solutions. Pure water has a pH of 7 acidic solutions have pH values < 7 and basic solutions have pH values > 7. Each change of one unit of pH is a tenfold change in acidity. Acid-base indicators, such as fit-mus and phenolphthalein, can be used to measure whether a solution is acidic or basic. A natural tmiversal indicator, red cabbage extract, can be used to determine the pH within 2 pH xmits. A buffer contains equal amounts of either a weak acid and its conjugate base or a weak base and its conjugate acid. 

Furthermore, Proteggente and colleagues [13] have found that cauliflower, peas, and banana had a low total phenolic content, 30, 32, and 38 mg GAE/100 g FW, respectively, whereas red cabbage extracts showed an appreciable phenolic content (158 mg GAE/100 g FW), higher than that of some of the flavanone- and flavanol-rich fruits and vegetables (Table 4). 

The antioxidant scavenger properties of brassica extracts rich in phenolic compounds have been proved in vivo in different organism. Broccoli extracts reduced the oxidation of muscle protein and liver lipids when supply to chicken in a diet (Young et al. 2002) and reduced several oxidative stress markers in healthy hiunan beings (Murashima et al. 2004). Red cabbage extracts protects against oxidative stress provoked... 

The E163 additives (different types of plant/fruit extracts such as grape skin extracts, blackcurrant extracts, purple corn extract, and red cabbage extracts) are not strictly considered antioxidant additives however, the antioxidant properties of anthocyanin fiavonoids are already well described [42]. Anthocyanins constitute a natural pigment with functional properties [43] and they have been used in cheese manufacture [44]. 

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