LN pigments Colorants

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Food Chemistry

Lecture topic - Colour of foods

There are a variety of issues regarding the colours of foods including:

1. Consumer perceptions that colour of foods is due to additives which are artificial and

dangerous;

2. The wide range and sources of molecules which contribute to the colour of foods;

3. Some coloured molecules can also have other functions in foods;

. The different regulatory approaches to colour additives around the world;

!. The varying stabilities of food colours during food processing; and

". #ecent developments regarding the adverse effects of artificial colorants.

MOTW $available in the folder on the %ood Chem website&

'ycopene describes the red pigment found naturally in tomatoes.

Further reading

Coultate !th edition pp 21(2" $or 3rd edition pp 13)(1**&.

%ennema+s %ood Chemistry th edition pp !*1("3, $or 3rd edition pp "!1(*22&.

-cCann / 0arrett / Cooper / Crumpler / alen '/ rimshaw / itchin 4/ 'o5 /6orteous '/ 6rince 4/ Sonuga(0ar5e 4/ 7arner 89/ Stevenson 8. 2*. %ood additives

and hyperactive behaviour in 3(year(old and ,)(year(old children in the community: a

randomised/ double(blinded/ placebo(controlled trial. 'ancet 3*:1!"(*.

Some other useful sources on colorants

sh -/ sh <. 22. =andboo5 of %ood dditives. 2nd ed. 4ndicott/ >?: Synapse <nformation

#esources. 1*)p.

0udavari S/ $editor&. 2". The -erc5 inde@: an encyclopedia of chemicals/ drugs/ and

 biologicals. 1th ed. 7hitehouse Station/ >8: -erc5 ACo. 1,1, p.

4merton B. 2,. <ngredients handboo5 food colours. 'eatherhead/ Surrey/ : 'eatherhead

6ublishing and 0lac5well 6ublishing.

Smith 8/ =ong(Shum '. 211. %ood additives data boo5. 2nd ed. 9@ford/ : 7iley(

0lac5well. 1))p.

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Colour molecules in a food product may be:

1. >aturally occurring molecules present in the ingredients used in manufacture;

2. The result of changes to coloured molecules occurring naturally;

3. dded during manufacture as approved food additives;

. -olecules formed during manufacture.

Natural pigments in food ingredients

These are often thought of as the plant pigments/ but the coloured molecules in animal tissues

are also important in many foods.

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aeme pigments

-any animal tissues contain pigments having haeme structures $also spelt heme&. 4@amples

are haemoglobin which gives the characteristic red colour of blood as well as the myoglobin

molecules which are the basis of the visual appearance of meat and flesh foods at least prior to

 processing or coo5ing. 7ith these molecules:

1. The haeme ring containing an iron ion is embedded into a protein structure;

2. The colour of the molecule depends upon the o@idation state of the iron and can be

manipulated by varying the groups co(ordinating with the iron;

3. The presence of the protein renders the molecule subDect to denaturation as a result of

conditions including heating;

. The iron is involved in various o@idation(reduction reactions which may involve

o@ygen and can therefore be controlled during processing and by appropriate pac5aging

approaches; and

!. <nteractions with nitrite added during manufacture can result in stabilisation of colour

in some foods.

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The structure of the haeme group $source; %ennema th edn p!*"&

The structure of the myoglobin molecule $source; %ennema th edn p!*"&

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Chlorophyll

The structure of the green pigments of plants resembles that of the haeme pigments and with

these molecules:

1. The metal ion is embedded into the structure is magnesium;

2. Barious forms of the molecule occur in plants/ but all function in photosynthesis;

3. Chlorophyll is associated with other plant pigment within the plant cells and these

others assist in stabilising the chlorophyll;

. Chlorophyll is relatively unstable once the plant tissues are disrupted;

!. -ildly acidic conditions result in release of the magnesium;

". Barious brea5down products are formed during food processing and these typically are

 brown and result in foods having a less attractive colour.

Structure of the chlorophyll molecule

$source; %ennema th edn p!,&

!

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6athways by which chlorophyll brea5down occurs

$source; %ennema th edn p!,1&

"

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Carotenoids

The carotenoids occur in all plants and these molecules:

1. -ay be yellow or orange colours;

2. re an integral part of the photosynthetic system;

3. -ay be classed as either carotenoids or @anthophylls;

. Carotenoids do not contain o@ygen atoms and are hydrocarbons typically containing

many double bonds in arrangements which allow for e@tended conDugated structures;

!. There are more than ! different carotenoids/ with the best 5nown including

lycopene and β(carotene;

". Some carotenoids are able to act as provitamin in the human diet;

*. Eanthophylls also contribute to the appearance of many plant based foods;

,. The carotenoids are currently the subDect of intensive research as they appear to

contribute to health through their antio@idant properties. They are able to react readily

with some of the significant free radicals formed during routine metabolism in the

human body.

Structure of lycopene

*

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!nthocyanins

1. 9ccur in most plant foods and particularly in fruits and vegetables where they bestow

dar5 red and purple colour;

2. iverse molecular structures give rise to a wide range of colours which are further

influenced by metal ions and p= of the food;

3. -any of these colours are relatively unstable.

OR

R

R

R

R

R

R

,

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"ibofla#in

N

NH

O

N

OH

OH

OH

HO

N O

Structure of the riboflavin molecule

)

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!ustralian legal re$uirements

nder the current ustralian >ew Fealand %ood Standards Code $accessible at

www.foodstandards.gov.au& colours are only permitted to be added to particular foods. <n

some cases the amount which can be added is limited. The specific standard is 1.3.1 which

covers food additives. The following schedules are ta5en from this standard:

SC%&'L% (

Colours permitted in accordance )ith *M+ in processed foods specified in Schedule ,

Numeric Listing

NS Number !dditi#e Name

1 Curcumins

11 #iboflavins

13 l5anet $A l5annin&

12 Cochineal and carmines

1 Chlorophylls

11 Chlorophylls/ copper comple@es

1!a Caramel < ( plain

1!b Caramel << ( caustic sulphite process

1!c Caramel <<< ( ammonia process

1!d Caramel <B ( ammonia sulphite process1!3 Begetable carbon

1"a Carotenes

1"c 6apri5a oleoresins

1"d 'ycopene

1"e Carotenal/ b(apo(,+(

1"f Carotenoic acid/ b(apo(,+(/ methyl or ethyl esters

1"1a %lavo@anthin

1"1b 'utein

1"1c rypto@anthin

1"1d #ubi@anthan

1"1e Biolo@anthin1"1f #hodo@anthin

1"2 0eet #ed

1"3 nthocyanins

1" Saffron/ crocetin and crocin

1*1 Titanium dio@ide

1*2 <ron o@ides

1

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SC%&'L% .

Colours permitted to a ma/imum of 01 mg2L in be#erages and 341 mg25g in foods other

than be#erages specified in Schedule ,

Numeric listing

NS Number !dditi#e name

12 TartraGine

1 Huinoline yellow

11 Sunset yellow %C%

122 Gorubine Carmoisine

12 6onceau #  

12) llura red C

132 <ndigotine

133 0rilliant blue %C%

12 reen S

13 %ast green %C%

1!1 0rilliant blac5 0>

1!! 0rown =T

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Structures of some colorants

 >

 >

 >a93S

N

N

 >a99C

S93 >a

=9

TartraGine

I>

S93

(

 >=2

C=2C=3

=2C

C=2C=3

(93S

C=2

S93

(

0rilliant 0lue %C%

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ssues in the use of artificial colorants

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Naming systems for additi#es

<n addition to a wide range of chemical names/ number codes are also applied to food colours:

Carmoisine

lternative name: aGorubine

<>S or 4 number: 122

S code: 4@t AC #ed >o 1

C< number $Colour inde@&: 1*2

 >

 >

=9

S93 >a

 >a93S

Structure of carmoisine

1

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Forms of colorants a#ailable

%or many of the artificial colorants approved for use in ustralia distinct forms can be used.

These are the free form and the la5es of the colorant.

Characteristics of la5es

Solubility/ coloration/ stability and bleeding

1!