Introduction

Scores and notes are to music as flavors and aromatic molecules are to gastronomy. There is no such shared reality with flavors, yet the perception of them varies wildly from person to person.

Taste is the sensation we feel when a substance in the mouth reacts chemically with taste receptor cells located on taste buds. The human tongue is capable of perceiving five basic tastes, namely sweet, bitter, sour, salty and savoury or umami.

In this article, Pritish Kumar Halder is talking in detail about bitterness and sourness. Bitter is perhaps the most sensitive of all the tastes. Many consider bitter as an unpleasant and disagreeable taste. Sourness is an indicator of acidity. The main difference between bitter and sour is that bitter is a sharp and pungent taste whereas sour is an acidic taste. Sour refers to an acidic pH (0 to 7) and bitter refers to an alkaline pH (7 to 14). Bitter allow the taster to evaluate the foods he eats as a very primitive test of what is safe to eat versus those things which might be dangerous, like toxins and poisons.

Let us see how bitter differs from sour.

 What is Bitter?

The bitter taste, or bitterness, is one of the most sensitive among the four classic taste modalities and probably the least understood. It was originally associated with a poisonous plant source, so it considerably produces aversive reactions. As the technology advanced, so did our understanding of the bitter taste. People have started to realize that not all bitter compounds are poisonous. Bitterness is produced by several different types of chemical substances such as sulphate, quinine, morphine, caffeine, nicotine, magnesium sulphate, and so on. Bitter compounds are not only numerous but also structurally diverse.

Often perceived unpleasant by many, bitterness is commonly found in strong, earthly flavored foods such as green leafy veggies (cabbage, spinach, zucchini, bitter gourd, etc.), and spices like turmeric. A wide variety of beverages also contain bitter components that make them so unique – beverages like tea, coffee, beer, ginger ale, and some non-alcoholic beverages like soda.

What is Sour?

Sour is one of the four classic taste sensations, along with the recently determined umami (savory) and is often associated with acidity. Often found unpleasant, sourness is the result of high quantity of acids in foods such as citrus, which includes limes or lemons. Acids such as lemon juice, vinegar, and many organic acids present in fruits contribute mainly to the sour taste. Sourness is mainly detected by the taste buds along the side of the tongue, and is presumably important in regulating dietary intake of H+. In fact, the degree of sourness is proportional to the degree of dissociation of H+ from an acid.

Sour foods that can be healthy additions to our diet include fermented foods, dairy products like yoghurt, fruits like cranberry, tart cherries, processed pickles, salty cheese, lentils, maple syrup, egg whites, dried peas, etc.

Bitter vs. Sour: Comparison Table

Parameters of Comparison	Bitter	Sour
Nature of Taste	Alkaline taste; sharp and pungent.	It is a milder acidic taste.
Sensitivity	It is the most sensitive taste for humans.	It is like the other regular tastes for humans.
pH Sensitivity	The 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 Receptor	Specialized G protein-coupled receptors in the taste bud called TAS2Rs or T2Rs.	Specialized taste receptors cells communicate through ion gated channels.
Likability	Bitter 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 Cells	Bitter things are known to detoxify body cells like the liver, pancreas etc.	Sour foods do not have any such effect.
Stimulation of Appetite	Bitter things owing to their bad taste often reduce the appetite of the consumer.	Sour things are known for being served as appetizers.
Examples	Bitter chocolate, coffee, bitter gourd, vegetable and fruit peels etc.	Lemons, citrus fruits or any food with known acids.

Difference between Bitter and Sour

As humans, we develop certain taste preferences over time, which make us crave some foods while dislike a few. We take a look at two qualities of taste to see how they compare – bitter and sour.

Taste Receptor

The taste sensation is attributed to a wide variety of molecules that interact with saliva to facilitate the sense of taste through a set of specialized cells called taste receptor cells. These are basically proteins that help us recognize the different types of taste modalities. The receptors responsible for sensing the bitterness in substances are TAS2R receptors, which are coupled to G proteins and comprised roughly 25 intact receptor genes and several pseudogenes.

The cells responsible for detection of sour taste are taste receptor cells (TRCs) that express the PKD2L1 receptor, which belongs to the family of TRP (transient receptor potential).

Health Benefits of Bitter

The bitter-tasting foods have their own health benefits, which include improved digestion, healthy blood sugar level, protection against heart diseases and diabetes. Bitter foods are rich in fiber and bitter greens like kale, radicchio, endive, etc. help us manage our cholesterol level and detoxify blood. They also aid in weight reduction and detoxifying the body.

Here are some important points of health benefits of bitter:

• 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.

Health Benefits of Sour

Sour-tasting foods are very nutritious and are rich in plant compounds called antioxidants, which provide protection from cell damage. Fermented sour foods like raw, unfiltered apple cider vinegar kill harmful bacteria and helps manage blood sugar levels and diabetes, and acts as a home remedy for many health ailments. Dairy products such as yogurt are a protein rich food which makes up for a healthy accompaniment.

Here are some important points of health benefits of sour:

• 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.

Usefulness

Being able to detect bitter substances at low concentrations is considered to be a protective function and hence is used by health researchers. Bitter tasting food is generally considered to be toxic and hence food processing techniques are used to detoxify these foods and make them more palatable. For example, Denatonium (a bitter, aversive agent) is added to toxic substances so that accidental ingestion can be avoided.

Sour taste is usually found in fruits like orange, grapes, lemon etc. Spoilt milk is also sour. People who like sour tastes can try the very popular Cry Babies, lemon drops, Shock tarts and Warheads.

Examples of bitter and sour food

Bitter Foods

Bitter green leafy vegetables include dandelion, kale, mustard, radicchio, broccoli rabe, cabbage, spinach, arugula, watercress, and so on. Bitter beverages include tea, coffee, beer, red wine, and cocktails. Other bitter things include dark chocolate, bittermelon, saffron, cranberry, cocoa, vinegar, grapefruit, cinnamon, etc.

Sour Foods

Sour taste most commonly attributes to citrus fruits, which include lemon, grapefruit, Mandarin oranges, key lime, yuzu, kumquats, etc. Acidic foods include confectioneries and cakes, white vinegar, white rice, alcoholic beverages, and so on. Sour cream, yogurt, and buttermilk are among the most common fermented dairy products that are sour in taste. Other sour foods include cranberry, tart cherries, processed pickles, salty cheese, lentils, maple syrup, egg whites, dried peas, etc.

Threshold Substances for Bitter and Sour Taste Comparisons

Taste is measured and defined using threshold substances. For example, the threshold for stimulation of bitter taste by quinine averages 0.000008 M (where M is molarity, indicative of how concentrated the solution is). Quinine is given and index of 1 and the taste thresholds of other bitter substances are rated relative to quinine. Brucine has a bitterness index of 11 implying that it is bitterer than quinine. Hence the bitterness of brucine can be detected at lower concentrations in solution. Denatonium is the bitterest substance known at a bitterness index of 1000.

 Sour taste is measured against the sourness bitterness threshold index of dilute hydrochloric acid which is 1. Hence Thus tartaric acid has a sourness index of 0.7, citric acid – 0.46 and carbonic acid – 0.06 when compared to threshold index of hydrochloric acid.

How Bitter and Sour tastes are perceived

Bitterness is perceived to be unpleasant, sharp, or disagreeable. The perception of bitter taste is facilitated by the combination of a taste receptor (Type 2) and a G protein (gustducin). The type of taste receptor, monomeric or surface bound, determines the various bitter ‘ligands’. In genetic studies for bitter taste perception, synthetic substances like phenylthiocarbamide (PTC) and PROP or 6-n-propylthiouracil are used. To ‘supertasters’ both these substances are extremely bitter.

Sourness is detected by the concentration of hydronium ions in the hydrogen ion channels. Hydronium ions are formed from water and acid. Hydrogen ions formed permeate the amiloride channels allowing for detection of sourness. Apart from these mechanisms of sour taste detection, there are other mechanisms also suggested. Among these prohibition of potassium channels by hydrogen ions leading to depolarization of cell, conversion of CO2 to bicarbonate ions facilitating weak acid transport are notable.

Summary

Nature provides us with different taste buds to help us identify the different taste sensations, including sourness and bitterness. The bitter taste is due to cations, while the sour taste is due to increase in hydrogen ion concentration (H⁺). Bitterness is probably the most sensitive among the taste sensations whereas sourness is the indicative of acid levels.

 

If you have any suggestions or queries, contact Mr. Pritish and help us to improve.

Thank You!

 

Composed by: Suma Sarker

Reference:

1. https://www.diffen.com/difference/Bitter_vs_Sour
2. http://www.differencebetween.net/science/difference-between-bitter-and-sour/
3. https://www.javatpoint.com/bitter-vs-sour
4. https://askanydifference.com/difference-between-bitter-and-sour/