A Scientist’s Perspective on Why Pie is Yummy and Delicious and Deserving of Your Respect and Admiration

It is an indisputable fact that I am deeply, irreversibly, head-over-heels in love with pie. Apple. Pumpkin. Blueberry. Banana Cream. You name it, I’ll eat it.

As Thanksgiving approaches, I find myself longing for a slice of warm apple pie with a big scoop of vanilla ice cream. I also find myself contemplating the scientific majesty that is an apple pie.

What majesty, you say? Well, friend, allow me to take you on a journey — from orchard to oven, from farm to table. Prepare yourself. Cozy up. Grab your snuggie. A tall glass of hot chocolate wouldn’t hurt either. Of course you’ll need some marshmallows. Got the marshmallows? Good! Let’s begin.

There are few evolutionary success stories as impressive as the apple’s. Think about it. This fruit was able to evolve a trait so desirable (its deliciousness) that we humans have taken it from its ancestral home in the mountains of Kazakhstan to every populated continent on Earth. We have immortalized the apple in art; we have juiced them, fermented them, sliced them, bobbed for them, dipped them in caramel, engineered machines for the sole purpose of coring them and, yes, made them into delicious pies.

You might think with all its uses that the apple must be a simple, easy fruit to grow. Humans are lazy, right? Surely we wouldn’t grow a fruit like the apple so much if it weren’t an easy thing to do. Wrong. False. Incorrect. Lies!

Apples are incredibly complex. Apples are extreme heterozygotes, meaning that the genes they inherit from their parents can be radically different between one apple and another apple on the same tree. If you were to grow a tree from a seed taken from a Granny Smith apple, you would most certainly, not obtain a tree filled with Granny Smith apples. Your apple tree would likely produce “spitters” — nasty, sour apples meant only to be spit out. Every so often a sweet apple would be grown by chance, but not with consistency.

So how do we manage consistency today? How do we grow a Granny Smith apple tree? Well, in order to produce a Granny Smith apple tree, you would need to graft one. Grafting is a horticultural surgical procedure whereby the tissues from one plant are transplanted into another, allowing for asexual reproduction of the primary tissue. As a result of this process, the tissues from the donor plant fuse with the tissues of the host plant and the resulting fruits are born from the genes of the donor tissue.

Without this process, apples would never have been domesticated; planting an apple tree would be like opening a box of chocolates — you’d just never know what you’d get.  It would be an adventure, yes, but 99 times out of 100, it’d be an unhappy one. Through grafting we have become slaves to the apple, spending billions of dollars per year on pesticides aimed at keeping the sweet apples we love away from the dark precipice of extinction. And for what? For pies. And to be perfectly honest, that’s all the reason we need.

The next thing you’ll need for your pie is a crust. There are many recipes that one can use to make a pie crust. But so far as it is an indisputable fact that I am deeply, irreversibly head-over-heels in love with pie, it is also a fact that the best pie crust recipe is indisputably my great-grandmother’s recipe. But I will not be supplying you with this recipe. This is not a “how-to” guide. Get over it. I will however, confide in you, my dear reader, the identity of one crucial ingredient. It’s flour. I know. Revolutionary! But don’t tell anyone. It’s a secret. Now that you know this deep, dark secret, you probably have some burning questions. If you’re like me, the first question you are probably asking yourself is “What are the explosive properties of flour?” Lucky for you, I have the answer!

As it turns out, flour is, indeed, an explosive substance. Flour is composed primarily of starch, which is, in turn, composed primarily of glucose. Glucose is highly combustible — it reacts with oxygen to produce carbon dioxide and water. When ignited by a flame, the sugars explode! Boom! Normally, this process is highly controlled — cells convert glucose into pyruvate through glycolysis and that pyruvate is then converted to carbon dioxide and water through the citric acid cycle and oxidative phosphorylation.

Through these processes animal cells produce the energy needed for carrying on with their day-to-day metabolic processes and that’s all good and well, but it’s probably not the type of combustion you were thinking of. Where are the explosions? Where’s the excitement? Well … this is the excitement. Your cells have the ability to carry out explosive reactions in a manner so intricate and organized that they cause no harm to you whatsoever — in fact, they help you. On a second-to-second basis, your body is “exploding” sugars and harnessing their energy. So put that energy to good use. Invest it in digesting more pie.

Of course there are many other ingredients that go into making the perfect apple pie (cinnamon, nutmeg, sugar, butter), but we will not address those here. We will, instead, end our journey with a discussion on ice cream — apple pie’s obligatory sidekick. Ice cream is a dairy product, meaning it is derived from mammalian milk. Humans have been consuming milk since the Neolithic revolution, but it wasn’t until Louis Pasteur invented pasteurization that dairy products such as ice cream could be made and stored for extended periods of time. Pasteurization is the process by which milk is heated and cooled in order to reduce the amount of pathogenic microorganisms in the product. Once pasteurized the milk is free to be used as an ingredient for whatever ice cream your heart desires! But as for me and my heart, we will desire vanilla.

If you’ve stuck with me this far, congratulations, your dedication is about to pay off! How, you ask?! Why with a discussion on the colligative properties of rock salt, of course! If you wanted to make your own ice cream, you could do it by filling a bag with milk (1/2 cup), sugar (1 Tbs), and vanilla (1/2 tsp), sealing that bag, and placing it in a larger bag filled with ice (4 cups) and rock salt (4 Tbs). Gently massage your bag for 5 minutes, or so, and voila, you’ve made yourself ice cream!

Witchcraft! You exclaim. No, silly! It wasn’t witchcraft. It was science.  You see, salt has the ability to lower the freezing point of water (meaning that it enables water to remain liquid beneath its freezing point).  For your ice cream, this means your ice/salt mixture will keep your milk/sugar mixture sufficiently cool for it to freeze into ice cream despite the fact that it’s sitting in your warm, cozy hands in your warm, cozy room. It also means you have a quick, easy way to make yourself a side dish for your apple pie!

By now you’ve probably finished your tall glass of hot chocolate and are wondering what to do next. This article is almost over; you’ll soon be left on your own. What will you do? Well, if I may make a suggestion; go make an apple pie and some vanilla ice cream. Bake it. Eat it. Respect it. Admire it. After all, it came a long way to get where it is today. Also, pie is yummy and delicious.

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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.