Malic acid

Some things in fruit taste sour. This sour taste comes from a special part of the fruit. It is in apples and grapes.

This sour part is found in many fruits. You can find it in peaches and plums. It is also in blueberries and cherries.

All living things make this sour part. It helps plants work. It even helps plants move water.

People use it in food too. It can make sour sweets. It is also in some potato chips.

It makes many foods taste tart. Do you like sour food?

Have you ever tasted a sour green apple? That sharp taste comes from malic acid. This is a special substance found in many fruits. It is in grapes, cherries, and blueberries. You can also find it in peaches and plums.

All living things make malic acid. It helps plants in many ways. It helps plants move water into their cells. It also helps plants make food. In some plants, it acts as a source of CO2. CO2 is a gas that plants use to grow.

People use malic acid in food too. It is a food additive. This means it is added to things like sweets. It can make candy taste very tart. It is even used in some potato chips.

Scientists first found this acid in apple juice. A man named Carl Wilhelm Scheele found it in 1785. The name comes from the Latin word for apple. This is because apples have a lot of it. Even unripe apples are very sour because of this acid.

Have you ever bitten into a tart green apple? That sharp, sour zing comes from a substance called malic acid. This organic compound is found in many different fruits and vegetables. It is the main acid in things like cherries, grapes, and blueberries. You can also find it in peaches, plums, and even blackberries. It is what makes unripe apples taste so sour.

Malic acid works in many important ways inside living things. In plants, it helps move water into cells. This happens when the acid moves into guard cells in a leaf. It often travels with potassium to keep an electrical balance. This movement helps the plant open its stomata, which are tiny holes. In some plants, malic acid also acts as a source of CO2. This gas is used in a process called the Calvin cycle.

Scientists have been studying this acid for a long time. A man named Carl Wilhelm Scheele first found it in apple juice. He did this work in 1785. At first, he wanted to call it "apple acid." Later, in 1787, Antoine Lavoisier suggested the name "acide malique." This name comes from the Latin word for apple, which is "mālum." This is the same root used for the apple genus name, Malus.

There are many interesting facts about how we use this acid. In the food industry, it is known as additive E296. People add it to sour sweets to make them taste tart. It is also used in "salt and vinegar" flavored potato chips. In wine, malic acid can be as high as 5 grams per liter. Some wine makers use a process called malolactic fermentation. This turns the sharp malic acid into a much milder lactic acid.

Today, we can make malic acid in large amounts in factories. In the year 2000, the production in America was 5,000 tons every year. Some of it is made by using a process called fermentation. This uses fumaric acid to create the natural L-form of the acid. This acid is also used to help separate other chemicals. It is a very useful tool in both nature and science.

Malic acid is a specific type of organic compound known as a dicarboxylic acid. It is found in all living organisms and plays many vital roles in biology and chemistry. You might recognize its effects through the sharp, sour taste it provides in many fruits. Because of its unique properties, it is also used widely as a food additive. In the food industry, it is identified by the E number E296.

In the world of biochemistry, malic acid is a key player in how cells function. It exists in two different forms called stereoisomers, which are known as L- and D-enantiomers. While both can be made in a lab, only the L-isomer occurs naturally in living things. This form, called L-malic acid, is a metabolic intermediate in the citric acid cycle. This cycle is a series of chemical reactions that cells use to produce energy.

Malic acid also helps plants manage their gas exchange and water levels. In the C4 carbon fixation process, malate acts as a source of carbon dioxide (CO2) for the Calvin cycle. Within plant leaves, malate is synthesized through the carboxylation of phosphoenolpyruvate in the guard cells. To maintain electrical balance, the malate anion often travels with potassium cations into these cells. This accumulation of solutes decreases the solute potential, which allows water to enter the cells. This process helps open the stomata, which are the tiny pores on a leaf.

Our understanding of this acid began with important scientific discoveries in the late 18th century. In 1785, Carl Wilhelm Scheele first isolated the acid from apple juice. He originally intended to call it "apple acid." However, in 1787, Antoine Lavoisier proposed the name "acide malique." This name is derived from the Latin word for apple, which is "mālum." This is the same root used for the biological genus name, Malus.

Malic acid is found in many different types of food and has specific concentrations in various products. It is the primary acid in fruits such as apricots, blackberries, blueberries, cherries, grapes, peaches, pears, plums, and quince. In grapes, concentrations can reach as high as 5 g/L. This acid gives wine a tart taste, though the amount decreases as the fruit ripens. In some cases, a process called malolactic fermentation is used to convert the sharp malic acid into a milder lactic acid.

Industrial production of malic acid is a significant global activity. Racemic malic acid, which is a mixture of both the L- and D-forms, is produced by the double hydration of maleic anhydride. To get the specific L-form, scientists can use the fermentation of fumaric acid. In the year 2000, the production capacity in the United States was 5,000 tons per year. This acid provides 10 kJ, or 2.39 kilocalories, of energy per gram.

Beyond food and plants, malic acid is a valuable tool in chemical research. It was essential in the discovery of the Walden inversion and the Walden cycle. In this cycle, L-malic acid is converted into (+)-chlorosuccinic acid using phosphorus pentachloride. This chemical process helps scientists understand how molecules change their structure. Malic acid is also used as a resolving agent to help separate other chemical substances like α-phenylethylamine.