What foods commonly contain carboxylic acids?
Why are carboxylic acids soluble (miscible) in water
carboxylic acid:
C6H5COOH. Sodium benzoate, the sodium salt of benzoic acid is used as a food preservative
Oxalic acid containing foods
The root and leaves of rhubarb contain dangerously high concentrations of oxalic acid.
Foods that are edible, but still contain significant concentrations of oxalic acid (another carbolic acid) include - in decreasing order - buckwheat, star fruit (carambola), black pepper, parsley, poppy seed, rhubarb stalks, amaranth, spinach, chard, beets, cocoa, chocolate, most nuts, most berries, and beans. The gritty feel one gets in the mouth when drinking milk with rhubarb desserts is caused by precipitation of calcium oxalate. Thus even dilute amounts of oxalic acid can readily "crack" the casein found in various dairy products.
Leaves of the tea plant (Camellia sinensis) are known to contain among the greatest measured concentrations of oxalic acid relative to other plants. However the infusion beverage typically contains only low to moderate amounts of oxalic acid per serving, due to the small mass of leaves used for brewing.
Research is being done on methods to safely reduce oxalate in food.
Apples contain malic acid, which contributes to the sourness of a green apple. Malic acid can make a wine taste tart, although the amount decreases with increasing fruit ripeness. The process of malolactic fermentation converts malic acid to much milder lactic acid. Malic acid, when added to food products, is denoted by E number E296
Sources:
http://en.wikipedia.org
http://www.wisegeek.com/what-foods-commonly-contain-carboxylic-acids.htm
http://www.chemguide.co.uk/organicprops/acids/solubility.html
Carboxylic acids are commonly found in various foods. Some examples include:
1. Citric acid: It is found in citrus fruits like lemons, oranges, limes, and grapefruits.
2. Acetic acid: It is commonly found in vinegar.
3. Lactic acid: It is present in fermented foods like yogurt, sauerkraut, and pickles.
4. Tartaric acid: It is naturally found in grapes and is also used in making cream of tartar.
5. Malic acid: It is found in apples, cherries, and other fruits.
6. Oxalic acid: It can be found in various vegetables like rhubarb, spinach, and beet greens.
Now, let's move on to why carboxylic acids are soluble (miscible) in water.
The solubility of a substance depends on its intermolecular forces. Carboxylic acids, including the ones mentioned above, are soluble in water due to their hydrogen bonding and polar nature.
Carboxylic acids contain a carboxyl (-COOH) functional group, which consists of a carbonyl group (C=O) and a hydroxyl group (OH) attached to the same carbon atom. The oxygen in the hydroxyl group can form hydrogen bonds with water molecules.
Water molecules are polar, with the oxygen atom being slightly negative and the hydrogen atoms being slightly positive. The oxygen atom in water can form hydrogen bonds with the hydrogen atoms in the carboxylic acid's hydroxyl group, while the hydrogen atoms in water can form hydrogen bonds with the oxygen atom in the carboxylic acid's carbonyl group.
These hydrogen bonds between carboxylic acid molecules and water molecules allow them to mix and dissolve in water, making carboxylic acids soluble or miscible in water.
It's important to note that the solubility of carboxylic acids can vary depending on their chain length, the presence of other functional groups, and the pH of the solution.
Foods commonly containing carboxylic acids include:
1. Citrus fruits: Citric acid is present in high concentrations in citrus fruits such as lemons, oranges, and grapefruits.
2. Vinegar: Acetic acid is the main component of vinegar, which is commonly used in cooking and food preservation.
3. Dairy products: Lactic acid is produced during the fermentation of milk, giving yogurt, cheese, and other dairy products a tangy flavor.
4. Fermented foods: Many fermented foods such as sauerkraut, kimchi, and pickles contain lactic acid, which is produced by bacteria during the fermentation process.
5. Wine: Wine contains tartaric acid, which gives it a crisp taste.
6. Berries: Fruits such as strawberries, raspberries, and blueberries contain various types of carboxylic acids that contribute to their tartness.
Carboxylic acids are soluble in water due to their ability to form hydrogen bonds with water molecules. The carboxyl group (-COOH) of carboxylic acids can bind to water molecules, allowing them to dissolve and form a homogeneous mixture. Additionally, carboxylic acids are polar molecules, which helps them to interact with the polar water molecules and dissolve easily.