We eat with our eyes

S.K. Saxena

An attractive colour is associated with quality and freshness. Consumers have expectations with regards to the typical colour of certain foods. A non attractive colour makes a product look as no longer fresh and likely to be rejected

We eat with our eyes, in most cases we do not enjoy food which does not match our colour perceptions. Colour has important psychological implications it particularly true in case of food. The initial perception of food by consumers is visual. Therefore colour has a very important role and the acceptance or rejection of a food product often depends on it. An attractive colour is associated with quality and freshness. Consumers have expectations with regards to the typical colour of certain foods. A non attractive colour makes a product look as no longer fresh and likely to be rejected. The eyes also play an important role in the actual eating process. Therefore it is very important to conserve the characteristic colour of a food product as far as possible during manufacturing and storage.

One example is bread, which is generally perceived as golden brown. A golden brown crust is important visually and definately enhances flavour. Pale bread has neither the same sales nor the same appetite appeal. Colour of bread is directly related to the colour of the pans in which it is baked. Unless new pans are factory prepared, their light coloured exteriors reflect oven heat away from the dough. The result is pale, poorly flavoured bread. It is not until pans have been used repeatedly that their exteriors darken, consequently absorbing oven heat, which is immediately transmitted to the dough __ creating the right crust colour and flavour.

Colouring of food products is required:

	To replace colour lost during preparation (e.g. preserved fruits and vegetables);
	To makeup the colour of a product whose ingredients cause it to become fade (e.g. sauces and drinks);
	To ensure consistent colour of products (e.g. confectioneries and desert products);
	To render the characteristic flavour more recognizable (e.g. synthetic syrups).
	Technical Possibilities for Colouring Food Products:
	Through the addition of colourant foods (e.g. Beetroot).
	With natural colouring agents occurring in food (e.g. Beta - carotene).
	With natural colouring agents not occurring naturally in food (e.g. Caramine).
	With permitted synthetic food colours.
	With inorganic pigments.
	Colourant Foods

The main colourant foods are beetroot, paprica extract, turmeric, grape juice and juices of coloured berries etc. These colourants have weak colouring effect and can also produce undesired flavours. Finally the poor colour stability restricts their use for colouring of food products.

Natural Colouring Agents

The natural colouring agents are chlorophyll, anthocyanin, carotenoids, riboflavin, curcumin, betanin, and cochineal (obtained from Cochineal Insect). In many cases these are not sufficiently stable to heat and light and at certain pH levels.

Synthetic Dyes

These do not occur in nature and have to be manufactured artificially. These are patrochemical product that can be made in practically unlimited quantity and with a high degree of purity, intensive colour concentration and consistent quality. These are resistance to heat, light and chemical influences.

Methods of Colouring Food

If food needs to be coloured for any of the reasons mentioned above, and if this cannot be done using coloruing foods, the first step is to decide which colouring agents are allowed by law for the product in question and in what quantities. It depends on the properties of the food. The stability and possibility of interaction between colouring agent and food ingredients must also be borne in mind, as is the exposure to heat in manufacture and/or processing by the consumer, and the packaging and storage conditions, including possible light influences. At all events, preliminary experiments and stability test should be carried out. Labelling obligations should also be considered and discussed.

Food Laws in India

Prevention of Food Adulteration Act 1954 define colouring matter as under:

Rule 23: Unauthorized addition of colouring matter prohibited __ The addition of a colouring matter to any article of food except as specifically permitted by these rules, is prohibited.

Rule 24: Extraneous addition of colouring matter to be mentioned on the label - Where an extraneous colouring matter has been added to any article of food that shall be written on the label attached to any package of food so coloured a statement in capital letters as below.

Contains Permitted Colours

Rule 25: Use of caramel permitted -- Not with standing provisions of Rule 24 (and Rule 32 (c) caramel may be used without label declaration.

Rule 26: Natural colouring matters which may be used -- Except at otherwise provided in the rules the following natural colouring principles whether isolated from natural colors or produced synthetically may be used in or upon any article of food.

	Beat-carotene
	Beta-apo-8-carotenal
	Methylester of Beta-apo-8' carotenoic acid
	Ethylester of Beta-apo-8' carotenoic acid
	Canthaxanthin
	Chlorophyll;
	Riboflavin (Lactoflavin)
	Caramel
	Annorto
	Saffron
	Curcumin (or turmeric)

Rule 27: Addition of inorganic matters and pigments prohibited __ Inorganic colouring matters and pigments shall not be added to any article of food: (Provided that chewing gum may contain Titanium dioxide -- Food grade up to a maximum limit of 1 per cent.

Rule 28: Synthetic food colours which may be used -- No Synthetic food colours or a mixture thereof except the following shall be used in food.

Rule 29: Use of permitted synthetic food colours prohibited -- Use of permitted synthetic food colours in or upon any food other than those enumerated below is prohibited:

	Ice-cream, milk Iollies, frozen deserts, flavoured milk, yoghurt, ice-cream mix powder.
	Biscuits including biscuit wafers, pastries, cakes, confectionery, thread candies, sweets, savouries (dal moth, mongia, phululab, sago papad, dal biji only);
	Peas, strawberries and cheries in hermatically sealed containers, preserved or processed papaya, canned tomato juice, fruit syrup, fruit squash, fruit cordial, jellies, jam, marmalade, candied crystallized or glazed fruits;
	Non-alcoholic carbonated and non-carbonated ready-to-seve synthetic beverages including synthetic syrups, sherbets, fruit bar, fruit beverages, fruit drinks, synthetic soft drink concentrates;
	Custard powder;
	Jelly crystal and ice candy

Rule 30: Maximum limit of permitted synthetic food colours __ the maximum limit of permitted synthetic food colours or mixture thereof which may be added to any food article enumerated in rule 29 shall not exceed 100 parts per million of the final food or beverage for consumption, except in case of food articles mentioned in clause (c) of rule 29 where the maximum limit of permitted synthetic food colours shall not exceed 200 parts per million of the final food or beverage for consumption.

Rule 31: Colours to be pure -- The colours specified in Rule 28 when used in the preparation of any article of food shall be pure and free from any harmful impurities.

Food Laws in European Union:

Directive 94/36/EC on colours for use in food stuffs -- This directive was drafted as a response to the continued need for food colouring in a single marked calling for the free movement of goods and fair competition, coupled with the demand for consumer protection and health safety. It stated in particular that all unprocessed food stuffs and certain other basic foods should be free of additives, and also set out strict provisions concerning the use of additives in food for babies and small children.

The directive defines colours as substances that give or restore colour to food. It includes natural ingredients of foods and natural raw materials that are normally used neither as food stuffs nor as typical food ingredients. Preparations made from food stuffs and other natural raw materials obtained by selective physical and/or chemical extraction of the nutritional or aromatizing components of pigments are also regarded as colours within the meaning of the directive.

Foodstuffs, whether dry or in concentrated form, and flavouring substances which are added during the manufacture of food preparations for their aromatizing, flavouring or nutritional properties and which have an incidental colouring effect -- such as paprika, tumeric and saffron -- are not regarded as colours. Nor are those in parts of the food such as cheese rinds and sausage skins that are not intended for consumption.

Betanin obtained from beetroot or anthocyan extracted from red grape skin, for example, are regarded as colouring agents rather than colouring foods. The food colours permitted by the EU are shown in Table 1. The colours themselves and their aluminum lakes are treated in the same way. There are some colours in the EU list that are not contained in all national colour lists (E 128 red 2F, E129 allura red, E133 brilliant blue FCF, E154 brown FK, E155 brown HT) or that are subjected to restrictions in Germany (E102 tartrazine, E110 sunset yellow, E123 amarnath, E127 erythrosine). Some technically insignificant carotenoids no longer figure in the list.

The caramels (E 150a-d) differ in terms of manufacture and application:

	E150a plain caramel, alcohol-stable, for spirits and confectioneries
	E150b caustic sulfite caramel, alcohol-stable, for spirits
	E150c ammonia caramel, for beers, soups and sauces
	E150d sulfite ammonia caramel, acid-stable, for non-alcoholic carbonized drinks.

Additive regulations in Germany and other countries used to contain a positive list of foodstuffs that could be coloured. A product that did not figure in the list could not be coloured. Exceptions were made at the time for riboflavin, carotene, and in some cases for caramel. This special status has now been abolished. The directives in Annex II-V are very detailed and go beyond the scope of this article and are summarized below.

Annex II of directive 94/36/EC contains a list of foodstuffs that may not contain added colour, except where colouring is allowed elsewhere. The most important food categories in Annex II are "untreated foods".

Annex III contains a list of foodstuffs to which specific colours only may be added, with the applicable quantities in each case.

Annex IV lists colouring agents approved only for certain purposes.

Annex V is divided into two sections: Section 1 lists colours that may be used in foods listed in Section 2 up to quantum satis. These colours may be used in addition in all other foodstuffs not mentioned in Annexers II and III, also be used in the designated foodstuffs with the maximum quantities and special restrictions. There are also regulations on the use of colours in composite food products.

The maximum levels refer to readymade food products prepared as instructed, and to the quantities of basic colouring components in the colouring additives.

For example, E104 quinoline yellow may be used in confectioneries up to a maximum of level of 300 mg/kg. Commercial E104 quinoline yellow contains 70% pure colour, so that a maximum of 428.6 mg/kg of this agent may be used, as the thresholds refer to the colour-giving component only.

With quantum satis references there is no maximum level. It is expected, however, that the colours will only be used to the extent necessary to achieve the desired aim. The consumer may not be misled.

In Germany, C colours, e.g. methyl violet (C2), are allowed for stamping eggs and meat. All colours of this type are not fobidden. Only E155 brown HT, E133 brilliant blue FCF, E129 alua red AC, or a suitable mixture of E11 brilliant blue FCF and E129 allura red AC are allowed for labelling meat products. Only the colours listed in Annex I i.e. food coloring agents, may be used for decorating egg shells.

Colours E123 amarnath, E127 erythrosine, E128 red 2G, E154 brown FK, E160b annatto, E161g canthazanthin, E173 aluminum and E180 lithol rubine BK may not be sold directly to consumers. This is a protective measure given the low ADI (acceptable daily intake) of these substances.

Despite some weaknesses, the directive represents a major advance for European food manufacturers and considerably facilitates the exchange of coloured foodstuffs within the EU.

Labelling of food colouring agents

When labelling food coloring agents a distinction has to be made between:

	labelling of the container in which the colourant is delivered to the food manufacturer and
	labelling of colorants on food packaging.

The latter is of significance for the consumer: no distinction is made in the declaration between the use of natural, nature-identical or artificial colours. With pre-packed products the colours in the list of ingredients must be identified as such followed by their commercial name or E number. For colourant foods the commercial name is sufficient.

Colours on skins or food coverings that are not be eaten do not have to be mentioned in the list.

Unpacked and pre-packed food exempt from the requirement for an ingredient list must be indicated "with colour". If the pre-packed food comes with a list of ingredients, this indication is not required.

Quality Assurance

Suitability should be tested before colours are used on an industrial scale by comparing the appearance of a freshly coloured food sample with samples made using a different formulation and stored either in original or comparable packaging for a defined period e.g.

	next to window at room temperature
	in a warming cabinet without light at 35-40 DC
	under artificial light without heat, or
	heated close to a lamp (40-50 cm)
	Quality Control

Quality control of coloured product is often carried out by comparing a sample with standard. Spectrophotometry is used a major the color of liquid and transparent product. The measurement takes place in a visual spectrum range. For non-transparent or insoluble product colour is measured by calculating the colour coefficient on the basis of the standard light reflected from the product.

Analysis

Analysis can be performed in two ways:

Isolation of the colour from the food and subsequent investigation.
Investigation of the colour present in the product.
As identification of a food colour involves only a few substances and reference material is normally available, either in pure form or as part of mixture, simple paper or thin-layer chromatography can be used. With isolated colours it is also possible to compare their reaction with acids and alkalis, of their solubility in concentrated sulfuric acid and subsequent changes in color when diluted with water. Quantities (intensity, mixing ratio) can most easily be determined by spectrophotometry. Inorganic pigments are identified by classic reaction tests. Colour coatings are measured after dissolution in dilute hydrochloric acid.

________________
Author is assoicated with GNFC, Anand, India.

<< Subscribe PFI