Difference between Bitter and Sour

There are five basic tastes that can be sensed or detected by our tongue: salty, sweet, bitter, sour and umami (savory). A taste is a sensation felt by us when we eat something and it reacts chemically with the taste receptor cells located on the taste buds. Sour refers to an acidic pH (0 to 7) and bitter refers to an alkaline pH (7 to 14). Let us see how bitter differs from sour.

Bitter:

Bitterness is the most sensitive of the five basic tastes and is often perceived as an unpleasant taste by the people. It is generally found in the food with earthy flavour like green leafy vegetables (spinach, kale, green cabbage etc), other vegetables (bitter gourd, egg plant, zucchini etc), and herbs, spices, tea, coffee, and certain fruits like olives, cocoa, etc. The bitterness found in the bitter foods is sensed by G protein coupled receptors.

Furthermore, a large number of toxic substances also taste bitter. It is believed that the ability to detect bitterness is evolved as a way to protect us from toxic plants and substances which often taste bitter. Bitterness is also found in many of our favorite foods and drinks like chocolate, beer, coffee and more.

Health Benefits of Bitter Foods:

Help cleanse and detoxify the liver
Rich source of vitamins and minerals
Helps reduce food cravings which helps lose weight
Activates taste buds that stimulate enzyme production and bile flow which improve digestion.

Sour:

Sourness is often associated with acidity. This taste is usually found in the foods that are rich in organic acids such as lemons, lime, oranges, tamarind, grapefruit, etc. Some food items or drinks also develop a sour taste after they are spoiled such as milk, wine etc.

The sourness in the foods is caused by one or more types of organic acids (hydrogen ions) present in the foods. The more organic acid a food contains, the sourer it will be. The sourness is sensed by ion channels present on the surface of cells in the tongue. Although people usually do not like sourness, it offers various health benefits.

Health Benefits of Sour Foods:

According to Ayurveda, the sourness triggers the salivary glands, which stimulates the appetite
Organic acids found in sour foods promote nutrient absorption in the body, e.g. citric acid improves iron absorption; lactic acid helps maximize calcium intake and more.
Malic acid, which is found in sour cherries and apples, in combination with magnesium helps treat fibromyalgia and chronic fatigue syndrome
Yogurt, buttermilk, kefir benefit digestion and boosts the immune system
Raw unfiltered apple cider vinegar helps lower sugar levels, improve good gut bacteria, etc.
Tart cherry juice is believed to reduce post exercise muscle soreness.

Based on the above information, some of the key differences between bitter and sour are as follows:

Bitter	Sour
It is a sharp, pungent taste.	It is an acidic taste.
It is often considered to be an unpleasant flavour.	It is not considered an unpleasant taste.
It is found in bitter foods like bitter gourd, olives, citrus peel, coffee etc.	It is found in sour foods like lime, oranges, grapefruit, unripe grapes etc.
Food with bitter taste helps detoxify body.	Food with sour taste helps improve body's ability to absorb minerals, cleanse body tissues etc.
It is sensed by G protein coupled receptors.	It is sensed by ion channels.
It is caused by chemical compounds such as quinine.	It is caused by organic acids present in the sour foods.