The Science of Baking Pt.2

Introduction

Welcome to Part 2 of The Science of Baking! Since this is the second installment of the series, I would recommend going back and reading part 1. This article will go through an experiment of baking a flaky pastry using two different types of fat: butter and coconut oil. There are accompanying pictures that I took myself showing in detail the two pastry doughs!

Step 1: Mix flour, salt, and sugar.

The two bowls of flour mix for each fat.
The two bowls of the flour mix and the corresponding fats in front of them.

Step 2: Break the fat up into 4 equal portions and add one portion of the fat component to flour mix.

The butter + flour mix
Coconut oil + flour

 

 

 

Step 3: Mix and add water slowly until a dough forms.

Dough with butter
Dough with coconut oil

Step 4: Roll out dough into flat sheet

The doughs rolled out into rectangles

Step 5: Break up the next portion of fat and spread along sheet of dough

One portion coconut oil dotted on dough
Butter dotted on dough

 

Step 6: Fold the end without fat over 1/3 of sheet and fold the other end over the top.

First fold
Second and last fold

Step 7: Roll out the dough exactly like in Step 4 carefully.

Rolled out dough for second time

Step 8: Repeat steps 5-7 two more times with the next two portions of fat.

Step 9: Wrap the dough in plastic wrap and chill in fridge for 30 minutes.

Wrapped up and ready to go into the oven!

Step 10: Preheat oven to 450° F and bake pastry for 8-10 minutes. 

Before baking…
Crispy, baked flaky pastry fresh out of the oven!

 

 

 

 

 

Observations

There were many, many differences between the butter pastry and the coconut oil pastry not only during the preparation, but after baking as well. Although coconut oil and butter have very similar structure at first glance, the butter was much creamier and incorporated into the flaky pastry dough much easier than the coconut oil. The oil melted super quickly, making it difficult to keep very doughy as it was getting way too wet. The coconut oil was also much harder to de-clump while the butter of course, had real clumps. Another huge difference between the doughs was their size. As seen from the photos, the coconut oil dough had a much larger size than the butter dough. My theory for this stark difference was that the butter was much thicker than the coconut oil, making the dough much more cohesive and elastic. The coconut oil pastry was clearer flatter and more spread out, due to the silky nature of the coconut oil. The butter pastry was also much taller than the flat coconut oil version; my thinking tells me the butter allowed for the pastry to rise better than the oil did.

In terms of taste, texture, and overall flakiness, both doughs performed relatively well but the butter dough definitely outshone the coconut oil. Though the butter dough was better in taste and more compact, the coconut oil pastry was also quite delicious as a substitute for butter. For any coconut lover, this is the perfect pastry substitution for fat. All in all, both doughs baked into beautiful flaky pastries with multiple light layers of crisp pastry, but the dough using the butter cooked better and tasted more like a pastry would normally taste.

The dough with butter and its nice flaky layers
Buttery, flaky layers of delicious pastry

 

 

 

 

 

 

The flatter layers of the coconut oil pastry
The coconut oil flaky pastry result

 

 

 

 

 

Conclusion

This experiment was so much fun to do considering I love to bake and have never made a flaky pastry dough before! I learned so much from the experience- not just how to make a flaky pastry but also so much new insight on how the science of baking really works together to create a magnificent dessert when heat is introduced to a couple of different ingredients. I encourage anyone reading this post who enjoys baking to try this experiment out for yourself to see if your results are the same! Not only did this experiment make me want to bake even more, but now I have an urge to try this recipe with all possible substitutes for fat like ghee, vegetable shortening, even lard. The possibilities are endless and we are just getting started!

Your journey starts here! Let’s talk!

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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.