Technically, there is no difference between sour and tart. Something that is has a tart taste has a sour taste. However, in some culinary circles tart flavors are differentiated from sour flavors. Generally, sour tastes from citrus, such as associated with citric acid, are described as “tart” while other sour flavors are called sour. This distinction is meaningless. Most of use think of lemons as sour. The word tart is simply a synonym. However, if you used “tart” to describe the taste of sour milk or fermented foods, it would sound strange. The answer? Just use the word sour. Taste experts and food scientist do not use the word tart. They stick to the word sour and divide sour tastes into different categories.
Different Categories of Sour Tastes
The taste we call sour comes from acids in foods. Citrus fruits have acids, primarily citric acid that is responsible for their sour flavor. Vinegar taste sour because it is acetic acid. Sour milk and yogurt get their sour taste from lactic acid. These three different sources of acid form the categories of sour used by food tasting experts and food scientists. These three categories of sour tastes are:
- Lactic sour: from lactic acid in fermented milk and dairy products like yogurt and buttermilk
- Basic sour: from citrus acids and other acids in fruits
- Acetic: from acetic acid in vinegar
Common Organic Acids in Foods Responsible for the Sour Taste
The acids we consume in foods are organic acids. These are acids that generally contain one or more carboxyl groups. The most common of these are carboxylic acids. These acids are considered weak acids. Note, however, that just because an acid is called weak does not mean it cannot be dangerous when in high concentrations. Here are some examples of organic acids that give a sour taste to foods:
- Acetic acid: found in vinegar
- Citric acid: found in citrus fruits
- Ascorbic acid: Vitamin C, found in fruits and vegetables
- Lactic acid: found in fermented or sour milk and associated dairy products
- Malic acid: found in apples
- Oxalic acid: found in spinach, rhubarb, and other vegetables
- Tartaric acid: main ingredient of cream of tartar, found in grapes, tamarind, cherries, coffee beans, and other fruits (also used to make baking powder)
- Benzoic acid: found in fruits and vegetables like cranberries, blueberries, strawberries, cinnamon, and many other common fruits, herbs, and spices
- Succinic acid: found in broccoli, rhubarb, cheese, sauerkraut, and other foods
The Importance of Sour Acids in Food
The sour taste of acids plays an important role in the sensory qualities of the foods we eat. They also help maintain nutritional value. Many naturally occurring organic acids are used as food additives to help preserve food. Benzoic acid is added to foods to prevent spoilage. Citric acid, malic acid, fumaric acid, and tartaric acid, are often used as acidity regulators or “acidulants” that can maintain or change the pH of food and thus improve the taste and safety of food. Ascorbic acid is an important food additive because it is a potent antioxidant that helps prevent oxidative decomposition of fats. 1Shi Y, Pu D, Zhou X, Zhang Y. Recent Progress in the Study of Taste Characteristics and the Nutrition and Health Properties of Organic Acids in Foods. Foods. 2022 Oct 28;11(21):3408. doi: 10.3390/foods11213408. PMID: 36360025; PMCID: PMC9654595.
Even without these functional properties, acids and thus sour tastes would be crucial to our enjoyment of food since it adds a bright and “fresh” flavor that helps balance out heavier tastes, especially fats. Acids also help stimulate saliva production which further enhances our taste perception.
