Chemistry of Cotton Candy Grapes
Hopewell Valley Student Podcasting Network
Chemistry Connections
Chemistry of Cotton Candy Grapes
Episode # 4
Welcome to Chemistry Connections, my name is Olivia, and I am your host for episode 4 called The Chemistry of Cotton Candy Grapes. Today, I will be discussing what acids are within a grape and how cotton candy grapes are made.
Segment 1: Introduction to Cotton Candy Grapes
Cotton Candy grapes are a variation of green grapes whose flavor is compared to the carnival fluffy, sweet confection cotton candy.
The process of turning a regular grocery store grape into a cotton candy grape is called hybridization. The common belief among people is that grapes are produced by injecting artificial flavoring; however, the cotton candy taste is through plant breeding. Hybridization happens between two different grape species; a type of Concord-like grape (like grapes used in Welch’s jams, jellies, and juices) and a variety of Vinis vi nif er uh, an everyday grape found at grocery stores across the country.
A Horticulturist is responsible for this process. Horticulturists are specialists with training in plant production and development who monitor and enhance the growth of high-quality food plants, decorative plants, and medicinal herbs.
These medium-sized, oval, or oblong grapes are seasonal fruit. They are also lacking seeds by default. We’ll cover everything that makes people wonder about the odd characteristics of these grapes, including their structure and sugar content.
Segment 2: The Chemistry Behind Grapes
First, let’s discuss what a grape really is. Grapes are made up of 70-80% water and are made up of acids which include tartaric, malic, and citric acid. Green grapes are more acidic (pH: 2.4). Red grapes (5.5-7) can be neutral. Acids contribute to overall acidity, giving a refreshing and tangy taste.
But what is an acid? An acid is created when substances dissolved in water increase the H+ ions in the solution. Donation of protons by acids (bronsted-Lowry) pH: range 0-14. Acids are less than 7 on a pH scale, and this is determined by H+ concentration. They also have different elements, such as their corrosive nature (ex rocks) and ability to conduct electricity (can conduct when dissolved in H2O). The H acts as a proton donor lowering pH. Acid-Base reactions (react with alkaline substances products are salts and water) (neutralization). There 7 strong acids, and these completely dissociate in H2O, while weak acids only partially dissociate (lower concentration of H+)
Grapes have a pH value that ranges from 1.9 to 4, which makes them an acidic fruit. These acids are at their highest concentration when the grapes are unripe, and acid content decreases as they mature. One of the acids in grapes, malic acid, has an ionizable hydrogen on each end of the molecule. This H dissociates and attaches to water molecules, making H3O+ which the tongue then detects as a sour taste.
Malic acid has 2 ionizable H’s, but why do only those hydrogens break off? First off, the dissociation of H in malic acid or any acid depends on acid strength. A diprotic acid (2 acidic H atoms) can dissociate in aq solution. Because this is a weak acid, and weak acids only partially dissociate, lowering the concentration. Both hydrogens have 2 different Ka values; Ka1 is larger than Ka2, so first, H dissociates faster than other.
In 2011, cotton candy grapes were first introduced to grocery stores. Vitis vinifera, sugars, and esters are responsible for giving their sweet flavor. Glucose and fructose are the main sugar compounds in the juice of grapes. At a ripening stage, the ratio of glucose to fructose is about 1:1; in overripe grapes, the concentration of fructose is greater than that of glucose.
Esters are mainly responsible for the flavoring of cotton candy grapes. An ester is a compound derived from an acid (ethyl acetate) which can be organic or inorganic. H or OH is replaced by R (organyl group), which represents any carbon or carbon chunk. Organic compounds are formed by the reaction between alcohol and acid, contributing to their flavor. Common esters in cotton candy grapes include ethyl butyrate (fruity aromma-reminscent of pineapple) and Ethyl hexanoate- sweet notes. During the ripening process, enzymes that are present in the fruit catalyze the formation of esters through alcohol molecules (naturally present). The presence of specific esters in cotton candy grapes can vary due to genetic factors, environmental conditions, and agricultural practices. Higher levels of esters in different cotton candy flavors are due to sugars and acids, which contribute to the overall taste.
Ethyl butyrate, C6H12O2, is bonded together through covalent bonding.
Pi bonds- overlap atomic orbitals, C double bond O 1 pi, 1 sigma, Sp2 hybridized orbital of O2, Unhybridized p orbital overlaps making pi bonds causing reactivity and chemical properties, allows rotation around sigma bond and behavior
Sigma bonds → C, H, O A sigma (σ) bond is a type of covalent chemical bond formed by overlapping atomic orbitals along the axis connecting the nuclei of two atoms. It is the strongest type of covalent bond and is commonly found in single bonds between atoms.
multiple bonds can be formed between atoms, such as double or triple bonds. These involve the formation of at least one sigma bond and other pi (π) bonds, which result from the parallel overlap of p orbitals. Sigma bonds are always formed first before the pi bonds.
C-c
C-H
C-O (double bonds) →Allow atoms to share electrons, makes covalent bonds
C chain is tetrahedral
C chain on the end is tetrahedral
O-C double bonds, polar. O is negative C is positive
The overall molecule is nonpolar
C-H bonds, C-C bonds, C-O, bonds, O-H bonds
Electrons around O (4)
Segment 3: Personal Connections
My favorite fruit is grapes, and I wanted to know more about the chemistry behind them. I also thought cotton candy grapes were manufactured and injected with flavoring, so I wanted to know how they were made.
Thank you for listening to this episode of Chemistry Connections. For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com.
Sources:
https://pubmed.ncbi.nlm.nih.gov/35630586/
https://en.wikipedia.org/wiki/Cotton_Candy_grapes
https://www.ncbi.nlm.nih.gov/books/NBK279408/
https://pubchem.ncbi.nlm.nih.gov/compound/malic_acid
Music Credits
Warm Nights by @LakeyInspired
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