The key difference between malic acid and citric acid is that the malic acid is a dicarboxylic acid that all living organisms produce whereas the citric acid is a tricarboxylic acid that is common in citrus fruits.
Both malic acid and citric acid are organic acid compounds. We categorize them as carboxylic acids because they have carboxylic groups (-COOH groups). Both these acids are responsible for the sour taste in certain fruits. Therefore, these compounds are useful as food additives as well.
CONTENTS
1. Overview and Key Difference
2. What is Malic Acid
3. What is Citric Acid
4. Side by Side Comparison – Malic Acid vs Citric Acid in Tabular Form
5. Summary
What is Malic Acid?
Malic acid is a dicarboxylic acid having the chemical formula C4H6O5. All living organisms can produce this compound. Furthermore, it is responsible for the pleasantly sour taste in some fruits. Ex: apples. Therefore, it is also useful as a food additive. There are two stereoisomeric forms of this compound; they are L-enantiomer and D-enantiomer.
Figure 01: The Chemical Structure of Malic Acid
However, only the L-enantiomer occurs naturally. When we produce this acid synthetically, we can get a racemic mixture of both forms. The IUPAC name of this compound is 2-Hydroxybutanedioic acid. The molar mass of this compound is 134.09 g/mol while the melting point is 130◦C.
What is Citric Acid?
Citric acid is a tricarboxylic acid having the chemical formula C6H8O7. This compound is common in citrus fruits. It has three carboxylic acid groups (-COOH) along with a hydroxyl group (-OH). The molar mass of this compound is 192 g/mol. Moreover, this odorless compound readily crystallizes from its solution. And these crystals appear as a white powder and it readily dissolves in water and anhydrous ethanol.
Figure 02: The Chemical Structure of Citric Acid
Furthermore, the carboxylic groups cause this compound to have strong hydrogen bonds. This acid is useful as a food additive and as a drink. In addition, it also acts as a chelating agent and an ingredient in some cosmetics.
What is the Difference Between Malic Acid and Citric Acid?
Malic acid is a dicarboxylic acid having the chemical formula C4H6O5. All living organisms produce this acid. The molar mass of it is 134.09 g/mol. It has two carboxylic groups, thus, has two replaceable hydrogen atoms. Citric acid is a tricarboxylic acid having the chemical formula C6H8O7. Citrus fruits is the common source of it. Further, the molar mass of this compound is 192 g/mol. It has three carboxylic groups, thus, has three replaceable hydrogen atoms. This is the main difference between malic acid and citric acid.
Summary – Malic Acid vs Citric Acid
Malic acid and citric acid are organic acid compounds. The difference between malic acid and citric acid is that the malic acid is a dicarboxylic acid that all living organisms produce whereas the citric acid is a tricarboxylic acid that is common in citrus fruits.
Reference:
1. “Malic Acid.” Wikipedia, Wikimedia Foundation, 25 June 2018. Available here
2. Davis, Sarah. “Side Effects & Benefits Of Malic Acid.” LIVESTRONG.COM, Leaf Group, 3 Oct. 2017. Available here
Image Courtesy:
1.’Äpfelsäure3’By NEUROtiker (talk) – Own work, (Public Domain) via Commons Wikimedia
2.’Zitronensäure – Citric acid’By NEUROtiker – Own work, (Public Domain) via Commons Wikimedia