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Color Changing Lemonade

September 17, 2021

Would you believe the drink above is lemonade, and the blue and purple colors are due to all natural ingredients? That’s right. The lemonade pictured is cooled with not-so-average ice cubes. These cubes are made from frozen butterfly pea flower tea. 

Butterfly Pea flower tea is a popular non-caffeinated tea from Southeast Asia. It is made simply by steeping butterfly pea flowers in boiling water. Butterfly pea flowers get their deep blue hue from a natural compound called anthocyanin. This compound is the reason for the dark blue color of the ice cubes in the video above, and is also the reason for the amazing color change that occurs when the ice cubes come in contact with the acid from the lemon juice.

Anthocyanin undergoes reversible chemical changes (shown above) when exposed to either acids or bases. The chemical change alters the chemical structure, which alters the way it absorbs different wavelengths of light. When anthocyanin is exposed to a base, it reflects green and then yellow, depending on the strength of the base. When anthocyanin is exposed to acid, it turns purple and then red, depending on the strength of the acid. Because lemons are acidic, the melted butterfly tea ice cubes turn purple!

You can make this cool color changing drink at home with butterfly pea flowers and other normal household ingredients.

Making the butterfly pea flower ice cubes is simple. Just steep about 4 to 5 butterfly pea flower tea bags, or 25 to 30 dried pea flowers, in about 2.5 cups of boiling water. You can choose to leave the teabags/flowers steeping for up to 30 minutes for concentrated color, but just 10 minutes will get you blue ice cubes that can definitely give you a beautiful color change.

All that’s left is to make the lemon mix that will turn the ice cubes purple! Mix 1 cup of lemon juice with ¾ cups of sugar and stir until the sugar is completely dissolved. You can heat up the mixture a little to speed the mixing process.

Next, take your frozen butterfly pea flower tea and put it in the blender or food processor to create shaved ice. If your blender is like mine and can only make crushed ice pieces, that’s okay, just make sure there is some melted tea in your glass to get the immediate color change effect. Fill your glass halfway with crushed or shaved butterfly pea flower ice, and then add the lemon mix! As the anthocyanin comes in contact with the acid from the lemon juice, it will turn a pretty purple color. If you have some bigger crushed butterfly pea flower ice pieces, they will stay blue and only turn purple as they melt, which will create a swirly blue/purple gradient effect. Fill the glass with your desired amount of lemon mix (I fill it about ⅓ full) and top the rest of the glass with club soda! And viola, you have your color changing lemonade!

Citations

Kodippili, D. (2020). Color Changing Lemonade Slushie (Galaxy Lemonade). The Flavor Bender. www.theflavorbender.com/galaxy-color-changing-lemonade-slushie/

Kan, Viirj & Vargo, Emma & Machover, Noa & Ishii, Hiroshi & Pan, Serena & Chen, Weixuan & Kakehi, Yasuaki. (2016). Organic Primitives: Synthesis and Design of pH-Reactive Materials using Molecular I/O for Sensing, Actuation, and Interaction. 

 

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.