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GMU:DIY Biolab “Driver’s License”/Yang Li (view source)
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1.1 anthocyanin | 1.1 anthocyanin | ||
Anthocyanins are water-soluble vacuolar pigments. In the 1664 book Experiments and Considerations Touching Colours by chemist Robert Boyle, various edible plants are reported as visual pH indicators due to pH-responsive mechanisms in their tissues [ | Anthocyanins are water-soluble vacuolar pigments. In the 1664 book Experiments and Considerations Touching Colours by chemist Robert Boyle, various edible plants are reported as visual pH indicators due to pH-responsive mechanisms in their tissues [1]. Anthocyanin is a kind of natural colorant in food and beverage industry, and has been found to possess anti-inflammatory antioxidant properties [2]. It has also been researched for use as an indicator for packaging applications to detect spoilage in pork and fish products [3]. All tissues of vascular plants contain the flavonoid anthocyanin, a pigment that changes colour under varying pH solutions. | ||
Under different pH conditions, the hydroxyl (OH) and/or methyl ether (O-CH3) groups attached to the carbon rings (figure 1) undergo reversible structural transformations and ionizations. Restructuring a molecule changes the way it ab- sorbs light, giving rise to colour changes [ | Under different pH conditions, the hydroxyl (OH) and/or methyl ether (O-CH3) groups attached to the carbon rings (figure 1) undergo reversible structural transformations and ionizations. Restructuring a molecule changes the way it ab- sorbs light, giving rise to colour changes [4]. | ||
[[File:Screen Shot 2018-01-31 at 12.08.56.png|400px]] | [[File:Screen Shot 2018-01-31 at 12.08.56.png|400px]] | ||
Figure 1 Chemical diagram of colour-changing anthocyanin pH reaction [ | |||
Figure 1 Chemical diagram of colour-changing anthocyanin pH reaction [5] | |||
1.2 red cabbage | 1.2 red cabbage | ||
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pH of expresso coffee is around 6, I add the solution (pH=8) into the original solution 1/2/3, the colour changing is more obviously. | pH of expresso coffee is around 6, I add the solution (pH=8) into the original solution 1/2/3, the colour changing is more obviously. | ||
[[File:result.jpg|400px]] | [[File:result.jpg|400px]] | ||
'''4. Discussion''' | '''4. Discussion''' | ||
The colour changing is very obviously when drop red cabbage solution into different pH solutions which are coloured transparent. However, coffee is dark, when drop red cabbage solution directly, it is hard to see the colour difference. I use the result of reversibility of colour change, add pH=8 solution into the original coffee and obtain the obviously changing. | |||
'''5. References''' | '''5. References''' | ||
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[2] Jian He and M Monica Giusti. 2010. Anthocyanins: Natural Colorants with Health-Promoting Properties. | [2] Jian He and M Monica Giusti. 2010. Anthocyanins: Natural Colorants with Health-Promoting Properties. | ||
[3] Xiahong Zhang, Sisi Lu, and Xi Chen. 2014. A visual pH sensing film using natural dyes from Bauhinia blakeana Dunn. Sensors and Actuators B: Chemical 198 (2014), 268–273. | [3] Xiahong Zhang, Sisi Lu, and Xi Chen. 2014. A visual pH sensing film using natural dyes from Bauhinia blakeana Dunn. Sensors and Actuators B: Chemical 198 (2014), 268–273. | ||
[4 | [4] Viirj Kan. 2017. Organic Primitives: Synthesis and Design of pH-Reactive Materials using Molecular I/O for Sensing, Actuation, and Interaction. Proceedings of the 2017 CHI Conference on Human Factors in Computing Systems Pages 989-1000. | ||
[5] UMass Amherst Department of Chemistry Lecture Demonstrations. | |||