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The Science of Baking: Know Your Dough

November 25, 2024

One of my absolute favorite hobbies is baking, so I wanted to not only share my experience with baking but also discuss the science behind common baking ingredients. We’re going to be exploring five different ingredients: yeast, cream of tartar, butter, baking powder, and baking soda. Let’s get started!

 

Yeast

Yeast is vital when it comes to creating a hearty loaf of bread, but yeast is incredibly temperamental. When growing yeast for bread, you have to put the yeast in lukewarm water (between 105℉ and 110℉). If the water is too hot, the yeast will die, and if the water is too cold, nothing will happen. Having a good base of yeast is the first step to creating bread, so if you mess up this first step, you might as well start over (Exploratorium, n.d.). Luckily, it usually only takes a few minutes to get the yeast to rise after feeding it some sugar, so you won’t be reset too far.

A bowl of yeast
Figure 1. The Spruce Eats / Diana Chistruga. This shows a bowl of yeast and flour after proofing.

 

Cream of Tartar

There’s a fair chance that you might not be familiar with this ingredient, so I’ll gladly explain. According to the McGill Office of Science and Society (2023), cream of tartar is a partially neutralized tartaric acid that is a byproduct of winemaking. Cream of tartar can be used for a number of purposes, but its most important use-case for baking is maintaining structure. My main experience with cream of tartar is when making macarons. You have to create a meringue during the process, and this is where cream of tartar is absolutely necessary. Cream of tartar is what allows egg whites to whip into a firm meringue and not lose its form. Using expired cream of tartar or even none at all will affect how your macarons rise, making them collapse in on themselves. For this reason, cream of tartar is crucial in delicate baking.

A container of cream of tartar.
Figure 2. All Recipes / Vanessa Greaves. Shows a container of cream of tartar.

Butter

Butter is a prominent ingredient in most baked goods, but something most people don’t realize when they’re using butter is how important the temperature is. You’ve probably read a recipe before where it says something like room temperature or melted or frozen; well, this clarification is very important. The temperature of butter when it’s being combined with other ingredients defines its role as a binding agent at different parts of the process. For example, if butter is melted, it will most likely be a part of the liquids section of a recipe, and if it is room temperature, it will most likely be with the solids. From my experience, frozen butter is usually used to prevent butter from melting too quickly and burning in an oven. All of these temperatures have specific and special roles (McCoy, 2015).

3 sticks of butter.
Figure 3. All Recipes / Kelsey Ogletree. Shows three sticks of butter.

Baking powder

You’ve most likely heard of baking powder or its counterpart, baking soda (which we’ll be talking about next), but you may not know the science behind it. According to Sorangel Rodriguez-Velazquez at American University (n.d.), baking powder is classified as a high quality chemical leavener. Baking powder is activated through moisture and heat and releases gas that moves throughout the baked good, allowing it to expand and grow in the oven. It’s very important to not use too much baking powder because it could cause your baked goods to collapse (Rodriguez-Velazquez, n.d.). Baking powder is pretty crucial to making baked goods like cakes and preventing them from becoming too dense. 

Container of baking powder.
Figure 4. Rumford Baking Powder. Shows a container of baking powder.

Baking Soda 

Now I know what you’re thinking, what is the difference between baking soda and baking powder? Well for starters, baking soda has only one ingredient, sodium bicarbonate, while baking powder contains that and two acids. The real difference when baking though is that baking soda reacts immediately while baking powder works at different stages, depending on if it’s single or double acting. Both act as leavening agents; however, since baking soda does not have acids built into it, it is only really used when there is some sort of acidic ingredient in it such as cream of tartar or buttermilk (Shipman, 2024). That’s why it’s usually baking soda in recipes involving those ingredients. 

Box of baking soda.
Figure 5. Arm & Hammer Pure Baking Soda. Shows a container of baking soda.

 

Baking is such a fun and fascinating scientific process. I hope next time you find yourself baking, you understand the ingredients you are working with better and appreciate the science that goes into every little moment.

 

 

References

Exploratorium. (n.d.). Bread Science 101. Exploratorium. https://www.exploratorium.edu/explore/cooking/bread-science

Pellegrinelli, C. (2024). What is Yeast?. The Spruce Eats. https://www.thespruceeats.com/basic-yeast-information-304312

Schwarcz, J. (2017). Cream of Tartar. McGill Office for Science and Society. https://www.mcgill.ca/oss/article/general-science-history/cream-tartar

Greaves, V. (2023). Cream of Tartar: What It Is and How to Use It [Photograph]. All Recipes. https://www.allrecipes.com/article/cream-of-tartar/

McCoy, J. (2015). Beyond Flavor: The Science of Butter. Institute of Culinary Education. https://www.ice.edu/blog/beyond-flavor-science-butter

TWOELLIS. (n.d.). [Photograph of three sticks of butter]. Getty Images. https://www.allrecipes.com/article/salted-vs-unsalted-butter-what-s-the-difference/

Rodriguez-Velazquez, S. (n.d.). 5.5: Baking Powder. American University. https://chem.libretexts.org/Bookshelves/Biological_Chemistry/Chemistry_of_Cooking_(Rodriguez-Velazquez)/05%3A_Leavening_Agents/5.05%3A_Baking_Powder

Shipman, M. (2014). The difference between baking soda and baking powder. North Carolina State University. https://phys.org/news/2014-05-difference-soda-powder.html

Berkheiser, K. & Richter, A. (2023). What’s the Difference Between Baking Soda and Baking Powder?. Healthline. https://www.healthline.com/nutrition/baking-soda-vs-baking-powder#:~:text=When%20to%20use%20which%20one,needed%20to%20produce%20carbon%20dioxide.

Light, J. (2024). Science of Baking Cover Art. STEMComm.

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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.