The organic acids in food, particularly acids in fruits and vegetables, vary enormously. However, a few principal acids act as the key players in producing unique flavor and even contribute to an increased chance of kidney stones, so awareness is essential.

Acids in Fruits

Some of the most common organic acids in food are found within fruits. Many people are already aware that citric acid occurs in citrus fruits such as oranges, lemons and limes, but there are lesser known acids in fruits that you may not have heard of. These include malic acid, which is found in apples, and tartaric acid found in grapes.

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The pH scale is used to measure the acidity of food, with one end of the spectrum reading “acidic” and the other “alkaline.” It counts from zero to 14, with zero being the most acidic and 14 the most alkaline. Foods that rest at 7 on the scale are considered neutral, whereas foods that feature a pH less than this are considered acidic. These acids provide these fruits with that distinctive, sharp taste. The mixture of acid and sugar is what gives fruits their unique flavor, so foods will often be deliberately fermented in particular acids to retain or increase the flavor. In addition to taste, acids in fruits are also used as preservatives due to their ability to reduce the onset of bacterial degradation. High acidity helps to kill bacteria so food doesn’t spoil as quickly. Maintaining an ideal pH level within the food keeps it fresher for longer. Many of the acids in fruits can provide benefits to your body if consumed in moderation, but some of the more specific benefits of each include:

• Citric acid: Found in the highest amounts in lemons and limes, it also occurs in many other citrus fruits such as oranges and grapefruits. However, what may be surprising is that a number of berries also include citric acid, including strawberries, raspberries and gooseberries. Due to its strong, sharp taste and high acidity, it is often used independently as a flavoring in various foods and drinks. Its key role in the body is the appropriately named citric acid cycle (or Krebs cycle) which occurs in all cells and is the process of releasing energy broken down from fats, carbohydrates and sugars.

• Malic acid: Predominantly found in apples, malic acid is also in a variety of fruits with stones at their center. This includes cherries, apricots, peaches and watermelon, despite watermelon being classed as an alkaline fruit. While all acids mentioned in this list feature a sharp taste, malic acid may have the strongest — for this reason, it is actually used to flavor the sour candies that are designed to overwhelm your palate. It is also used to give salt and vinegar-flavored products that distinctive taste. Similarly to citric acid, the body uses malic acid for a variety of cellular processes and as such, salts of malic acid are found in the cells of most living things.

• Tartaric acid: Though not as common as its counterparts citric and malic, tartaric is still a common acid found in foods, particularly in grapes and avocados. As with malic acid, it is sometimes used as sharp flavoring in sour candies, but its predominant use is in wine. Manufacturers include tartaric acid in their wines to increase the tartness of the wine’s taste, thus providing it with a stronger and more distinctive flavor.

These are just three of the more predominant acids in fruits, but there are many others that play smaller roles in the body such as succinic, oxalic, benzoic, isocitric and quinic acid. A February 2018 study published in Horticulture Reviews found that fleshier fruits (such as berries, watermelon, peaches and other soft fruits) have the highest levels of key acids compared to their harder counterparts.

Acids in Vegetables

Many of the acids present in vegetables are also present in fruits — the key difference is that vegetables do not tend to be as acidic in their makeup, making them a potentially safer source of key acids if you struggle with acid reflux or high stomach acidity. There is some crossover in the organic acids found in food. Both fruits and vegetables include citric acid (found in tomatoes, cayenne peppers and even lettuce), oxalic acid and benzoic acid (the oldest known food preservative). Vegetables that are naturally low in pH acidity include:

• Asparagus
• Beans
• Corn
• Cucumbers
• Garlic
• Green beans
• Greens (lettuce, kale, collards, spinach, etc.)
• Onions
• Peas
• Pumpkins
• Squash (summer or winter varieties)

Though these vegetables naturally possess a low pH acidity, they are still high in essential amino acids due to their protein content. Oxalic acid, also known by its chemical name ethanedioic acid, is a naturally occurring acid found in a wide range of vegetables. In its purest form, oxalic acid appears as a colorless, crystalized powder. When consumed in high doses, it imparts corrosive, bleach-like properties.

Luckily, it is found only in trace amounts in vegetables, so you don’t need to worry about bleaching your stomach with a green veggie, but even in low amounts, oxalic acid forms into oxalates, which can have a distinct effect on your body. Oxalates are known for binding to almost any mineral in the body, which does not ordinarily pose an issue due to the water solubility of these compounds. However, when oxalates bind with calcium, it is nearly impossible for the body to move the calcium oxalate through the system due to its close-to-insoluble state. Oxalates build up insoluble compounds that can lead to kidney stones if precautions aren’t taken. According to the Cleveland Clinic, adjusting your diet to eat less foods high in oxalic acid is the first step for reducing the risk of adverse effects. Vegetables high in oxalic acid include:

• Cucumbers
• Potatoes
• Sprouts

The highest concentrations occur in dark, leafy vegetables such as spinach, kale and broccoli.

Acids in Dairy Products

The principal acids found in dairy products are benzoic acid, lactic acid and a variety of fatty acids which contribute to dairy products’ reputation as a high-fat food. Cow milk produces a complex range of fatty acids, with over 400 individual fatty acids comprising its unique makeup. The flavor of dairy products is directly related to its content of fatty acids, similarly to the way lemons get their distinct taste from citric acid, and sour candies are flavored with malic acid. This correlation is especially true in the fermentation process to create stronger cheeses. Despite dairy products’ potentially high-fat content, when it comes to acidity, they are not so bad. An October 2011 study published in the Journal of the American College of Nutrition found that milk and dairy products neither produce acid upon metabolism nor cause metabolic acidosis. The study also found that the consumption of dairy products does not make the body acidic as a whole.

What Kinds of Acids Does Sour Candy Have?

Sour candy is made from acids found in food. Whether you love mouth-puckering sourness or prefer a slightly sour sensation, the intense flavor of sour candy comes from organic acids. While there are at least eight different acids used in sour candy, the four most common are citric, malic, tartaric and fumaric acids. Each acid has a different level of sourness, as well as other flavor nuances of bitterness and astringency. Sour candies usually contain a mixture of two or more acids to create the desired flavor.

Citric Acid

Citric acid provides a burst of tartness. It comes from lemons, grapefruit and other citrus fruits, which makes it easy to imagine the sour tang it delivers. Berries also contain citric acid, and it’s a secondary acid in many fruits and vegetables. Food-grade citric acid is commercially produced by fermenting sugar with microorganisms. In addition to contributing sour flavor, it prevents spoilage and stabilizes color in foods and beverages. Beyond its use in candy, citric acid fills beneficial roles in your body. It works as an antioxidant, and it’s essential for energy production. Citric acid is also used to help prevent kidney stones.

Malic Acid

Malic acid delivers a smooth, mellow tartness similar to biting into an apple, where it’s the predominant acid. Apricots, cherries and tomatoes also contain malic acid. In candy, it boosts the intensity of sour flavors and enhances fruit flavors, reports food-grade chemical supplier Bartek. Like citric acid, malic acid is produced in your body, participates in the synthesis of energy and can be commercially produced through fermentation. A small study published in the Journal of Endourology in February 2014 reported that malic acid may help with calcium oxalate kidney stones.

Fumaric and Tartaric Acids

Fumaric acid is the strongest and most sour-tasting acid of the organic acids. In candy, it creates a long-lasting sour flavor because it doesn’t dissolve as easily as other acids. A small amount of fumaric acid naturally occurs in apples, beans, carrots and tomatoes. Tartaric acid tastes moderately sour and is more astringent than citric and malic acids. While it’s often found in sour candies, tartaric acid is also an essential ingredient in cream of tartar and baking powder. This organic acid is associated with grapes and wine, as well as bananas and tamarinds.

Health Concerns

While the amount of acid you’ll get from occasionally enjoying sour candy isn’t likely to cause problems, organic acids can temporarily irritate your tongue and mouth, especially if you eat multiple pieces in a short time. On the pH scale, which measures acidity and assigns a value of zero as the most acidic, sour candies have a pH between 2 and 3. This makes them acidic enough to erode tooth enamel, reports the Minnesota Dental Association. You can reduce damage from acids by limiting the amount of time you have sour candy in your mouth and rinsing with water as soon as you’re finished. Don’t brush your teeth for at least an hour, or you’ll exacerbate the acid’s damage.