Difference Between Bitter and Sour

The human tongue is capable of perceiving five basic tastes, namely sweet, bitter, sour, salty and savoury or umami. Each of these tastes can be detected by our taste buds utilizing specialized taste receptors for each. Bitterness is the strongest taste. It is the taste of an alkaline substance. Sourness is a milder taste and helps us perceive acidic substances.

Bitter vs Sour

The main difference between bitter and sour is in its taste or perception and the taste receptors they activate in the taste buds on the tongue. Bitter is a strong, sharp, pungent taste that is mostly not likeable, while sour is a milder acidic taste that is mostly considered pleasant.

Bitter vs Sour

Bitter is the taste of any alkaline substance meaning any substance with a pH above 7 to 14. It is the strongest taste in humans and is perceived by all the taste buds in the tongue. It is perceived by a group of taste receptors called GPC receptors, namely TAS2Rs or T2Rs.

Sour is the taste of any acidic substance meaning any substance with a pH below 7 to 0. It is perceived by all the taste buds of the tongue and is perceived by a group of taste receptors cells (TRCs) that have ion channels to communicate messages to the gustatory nerve.

Comparison Table Between Bitter and Sour

Parameters of ComparisonBitterSour
Nature of TasteAlkaline taste; sharp and pungent.It is a milder acidic taste.
SensitivityIt is the most sensitive taste for humans.It is like the other regular tastes for humans.
pH SensitivityThe taste of eatables between 7-14 is perceived as bitter by the brain.The taste of eatables between 1-7 is considered sour by the brain.
Taste ReceptorSpecialized G protein-coupled receptors in the taste bud called TAS2Rs or T2Rs.Specialized taste receptors cells communicate through ion gated channels.
LikabilityBitter is considered an unpleasant taste to witness.Sour is considered a more or less pleasant flavour in small amounts often also treated as a delicacy
Detoxification of Body CellsBitter things are known to detoxify body cells like the liver, pancreas etc.Sour foods do not have any such effect.
Stimulation of AppetiteBitter things owing to their bad taste often reduce the appetite of the consumer.Sour things are known for being served as appetizers.
ExamplesBitter chocolate, coffee, bitter gourd, vegetable and fruit peels etc.Lemons, citrus fruits or any food with known acids.

What is Bitter?

Bitter is the name used to describe the flavour of alkaline substances with high pH. This flavour is detected by guanine nucleotide-binding protein receptors that activate by coupling a bitter molecule to its active site. These are called TAS2Rs or T2Rs. This leads to conformational changes in the receptor that activates chemicals called secondary messengers that transmit the message through the gustatory nerve to our brain.

 The brain is highly sensitive to bitter substances, probably due to an evolutionary adaptation as most naturally occurring poisons and toxins are bitter in taste. It characterizes it as an unpleasant, pungent taste.

However, having bitter foods have its own advantages. For example, butter foods activate our taste buds, and this helps us taste better. They detoxify certain body cells like the liver. Chocolate is a bitter substance that is known to be good for the heart and circulation.

Some of the most common bitter foods are coffee, chocolate, bitter gourd, raw vegetables, spinach, Haldi, etc. Some bitter foods are also known to have antibacterial and antimicrobial properties like neem and haldi. Bitter food often reduces appetite and are paired with a diet for weight loss.

Quinine is a bitter substance. To compare bitterness of a substance, we measure it in terms of how bitter it is in comparison to quinine, whose level of bitterness is considered as 1.

What is Sour?

Sour is the name used to describe the flavour of acidic substances. Any acid is a substance that has a pH lower than 7. All acids taste sour. Any food that tastes sour has some form of acid in it. For example, lemons have citric acid.

This flavour is detected by specialized taste receptor cells present in the taste buds. The cells detect sourness with the help of ion gated channels in their membranes that respond to specific ions like metals or hydrogen in the case of sour food. Once the flavour is detected, the gustatory nerve transmits the message to the brain.

The brain responds accordingly. Sourness is a milder taste compared to bitterness and is almost always considered tasty. For example, lemon juice, pickles, sour candies etc., are delicacies. Sour foods increase our appetite and thus should be a part of the daily diet.

Some advantages of consuming sour foods are they help in increasing metabolism, and this weight loss triggers salivation, helps in ion absorption (malic acid), calcium intake ( lactic acid) etc. Curd is a sour food known to help in better digestion. Vinegar is known to benefit in numerous amounts of ways and is also one of the most common acids that are consumed.

Hydrochloric acid serves are the sourness index which means a comparison of sourness of food is made with hydrochloric acid whose measurement is considered as 1.

Main Differences Between Bitter and Sour

  1. Bitter is an unpleasant flavour, while sour foods tend to be delicious.
  2. Bitter taste indicated alkalinity, while sour taste indicates the acidity of the food.
  3. Bitter taste receptors are TAS2Rs or T2Rs, which are a group of GPC receptors, while sour taste receptors are ion receptive, which means they react with specific ions.
  4. The bitterness index is measured by quinine, while the sourness index is measured by hydrochloric acid. Each of whose indexes is 1.
  5. Bitter foods help in detoxifying cells, while sour foods help in weight loss.
Difference Between Bitter and Sour


Each taste bud present in our tongue has a taste pore that leads to a group of specialized cells to detect the five basic tastes, among which are bitterness and sour. Although unpleasant, bitterness is readily recognized and sensed by our brains. Sourness is known to be tasty, however, in a limited amount, after which it is disagreeable. Even the methods of their detection differ.

Each of the following tastes come from specific foods that are equally important and serve specific functions. They have their advantages, and thus both bitter and sour food items must be included in our diet for balanced nutrition intake.

Each of the following tastes come from specific foods that are equally important and serve specific functions. They have their advantages and thus both bitter and sour food items must be included in our diet for balanced nutrition intake.


  1. https://europepmc.org/article/med/16732425
  2. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1750-3841.2007.00282.x
  3. https://www.sciencedirect.com/science/article/pii/S0022532065801034
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