Colours, Flavours and Organic acids
Besides macro-molecules and micro-molecules that constitute the food there are many other substance or compounds that are found in food. These compounds possess different functions. These may include colours, flavours and organic acids. These are the food components other than the major food constituents such as micro-molecules and macro-molecules. The function of colours is to enhance the attraction of a consumer for the food and it is also an indicator of the food freshness. Flavour defines the food taste. Flavours make the food tasty and enhance the palatability of food. Moreover, organic acids may act as preservative or flavor enhancer. These may also increase the food palatability. In this article, all these three food constituents that colour, flavour and organic acids will be discussed.
Colour is an important component of the food. It is the first thing that is usually taken by your senses into consideration. Colour is an indicator of the food spoilage, ripeness and freshness thus contributing towards the healthy eating. Colour is a natural constituent of food but can also be added artificially on commercial level to enhance the food attraction and palatability.
Functions of colours:
Colours in food may have the following functions:
- Colours usually appeal the eyes of the consumer thus triggering the attraction
- Colour usually makes the food attractive
- These can provide certain vitamins e.g beta-carotene and minerals e.g magnesium
- It is also an indicator of the food quality e.g ripeness in fruits and vegetables
Types of colours:
There are usually two types of colours:
- Natural colours
- Synthetic colours
Natural colours may include the following pigments:
Pigments with poryphyrin ring:
Haeme, bile pgments and chorophyll are those pigments that contain poryphyrin ring structures. Chlorophylls are green in colour and are associated with the photosynthesis. This green colour usually deteriorates with undergoing food processing or storage. When the vegetables are exposed to light, due to photo-oxidation the green colour is faded up. It can also be reduced through feezing the product.
Haeme pigments are red and brown in colour. These are usually present in meat and fish and are structurally similar to the chlorophyll but in these pigments central element is iron as compared to magnesium in the chlorophyll. In meat, the colour deterioration process is reversible with the changing of the myoglobin (pinkish-haeme in meat known as myoglobin) into the oxyhaemoglobin (red) and metmyoglobin with brownish colour.
Bile pigments are usually the breakdown products of old haemoglobin (RBC’s) in the liver and may impart colour to the stool.
These are usually present in all red or yellow coloured vegetables, fruits and flowers. These are usually carotenoids and also present in cow’s milk. These are usually the precursors of the vitamin A in the form of beta-carotene. Animals must take these pigments that are carotenes to have vitamin A production in their body. Besides beta-carotene, lycopene is also another example of carotenoids. Lycopene gives red colour to tomatoes and water melon (in which it is about 95%) but is not responsible for vitamin A production. Lycopene is activated when heated with fats but may contribute in the production of one of the fat soluble vitamins. In foods containg carotenes, beta-carotene is the most abundant one about constituting the 85% of carotenoids.
The beetroot varieties contain the red beta-cyanin and betanin. This is an intense colour usually sronger than the synthetic colours. Beetroot juice is used as food ingredients that are pasteurized, centrifuged and concentrated to give a viscous and thick liquid concentrated with approximately 70% of sugar and 0.5% betanin.
These are present in fruits like figs, mulberry, red blood oranges and many other vegetables. Benzo-pyran structures usually give orange, red or blue colours to plants. These usually have no particular function except imparting colour. These are usually Anthocyanins that are water insoluble compounds. They further react with ascorbic acids that cause the destruction of both compounds.
Caramels are produced by the controlled heating of sugars. These are usually important in syrups, confectionery and making bread. This colouring is also used in custurds, ice-cream and beverage products. They are usually responsible for the appealing brown colour of bread crust, sweets, toffees, beverages and syrups.
They are usually the products of Maillard reaction that occur in mostly milk and milk products when the basic nitrogenous compounds react with reducing sugars. As a result of the Maillard reactions, melanoidins the brown nitrogenous polymers are produced along with copolymers and destruction of the essential amino acids.
Synthetic or artificial colours:
Artificial colours are produced artificially on the industrial level to impart colouration to food in cheap manner. These are not etracted from natural products as it is a very expensive process and the product gain is too small to meet the demands. There are usually two types of synthetic colours:
Lakes: These are usually fat soluble and impart colour on dispersion.
Dyes: These are usually water soluble and are synthesized from coal tar. It gives colour when it is dissolved.
Flavour is the parameter that usually denotes the taste of the food along with odour. Flavouring substances are usually the aromatic compounds that are usually taken by the taste and odour both by the mouth and nose.
These may have the following functions:
- Provide pleasure to the consumer
- Make the food tasty and enhance the satisfaction
- Act as an indicator of stability
All food compounds usually contain the natural flavours of their own. Natural flavouring substance may include; herbs, spices, essential oils and plant extracts. There are many flavouring compounds that include:
Acetic acid is the acid of vinegar that has a sour and penetrating taste. Butyric acid is present in rancid butter giving an unpleasant odour.
The low molecular weight alcohols e.g methanol and ethanol have spirit like odour and are soluble in water that may be due to hydrogen bonding.
Esters usually give many fruity flavours e.g butyl acetate. Iso-amyl acetate is famous for its banana-like aroma. Their characteristic is same as alcohol with respect to flavour.
As flavours, unsaturated aldehydes are usually important. Acrolein is an unsaturated low molecular weight aldehyde with an irritating odour and is used in foods prepared with fats mostly the fried foods.
These are the alcohols usually derived from acyclic terpenes. Its example is Geraniol that is found in many essential oils and also in those of lemon and orange.
Ketones that have 7 carbon atoms are important with respect to flavouring. Diacetyl is present in sour cream, buttermilk and cultured butter.
These are usually present in milk and milk products. Delta lactones are the most important one in milk and milk products particularly in butter.
Eugenol is an important compound found in the oil of cloves responsible for their aroma. Thymol is found in other spices, is also another example of it.
These substances are usually present in coffee as methyl mercaptan, furyl mercaptan and dimethyl sulphides. Oil of garlic is prepared by allyl sulphide, allyl propyl disulphide and other compounds.
These are such type of compounds that don’t give any flavor by themselves but enhance or intensify the flavor of already present compounds in the food. These may include:
- Monosodium glutamate
- 5’-nucleotides; common examples
Monosodium glutamate is soluble in water, being a white crystalline compound. It is prepared from wheat gluten and is salty in taste. These are usually important for their use in gravies, meat, sauces and the protein rich foods. In Pakistan, it is used for cooking chinese dishes.
|Citric acid||Citrus fruits|
|Tartaric acid||Grapes and tamarind|
|Lactic acid||Sour milk|
Organic acids may also give a flavour but mainly act as the preservative compounds. These are naturally present in plants and animals. Some of them may include:
The functions of organic acids may include:
- Give sourness to foods and beverages
- Enhance the food palatability
- Prevent browning in food
- Act as preservatives
- Intensify the flavours
- Change the food texture due to their reaction with food components
So, in a nutshell colours, flavours and organic acids are the important food constituents in enhancing the palatability and food attraction with performing many other functions such as by giving a pleasanr odour and a desirable colour appealing to the eyes.