FUTURE PROSPECTS

IV. FUTURE PROSPECTS

In a 1987 survey carried out by the Commission of the European Communities, 63 experts from 9 countries were interviewed. It was predicted that by the year 2000 about 50% of the synthetic additives would be replaced by natural additives, with the bulk being syn- thetic colors and flavors (44).

At the moment, the use of synthetic food colorants is still very much favored by most food manufacturers. One of the reasons being the high cost of natural colorants due to the low yield as compared to the synthetic food colorants. The superior properties of the latter, such as the greater tinctorial strength and stability, also contribute to the greater demand for synthetic colorants at the moment. Other major obstacles of the natural food colorants are their variability due mainly to plant variety as well as changes in weather and soil conditions and the uncertainty in their supply. Seasonal variation of the pigment sources also means that a constant supply would be difficult.

Those pigments obtained from plant materials are usually secondary metabolites produced by the plant cells. With the emergence of biotechnology, it is believed that plant tissue culture and fermentation could offer possible solutions (45,46) to the problems encountered in the production of natural food colorants. Both methods offer several advan- tages over the extraction of pigment from whole plants: They are more reliable and predict- able as the processes are not prone to seasonal variation. The quality of the pigments are improved as they are no longer affected by strain variation and changes in weather conditions.

Natural pigments obtained by tissue culture include anthocyanin, anthraquinone, and shikonin. However, until recently, commercial production via tissue culture has been plagued with several setbacks. The main obstacle being the relatively low yield by such methods, thus rendering it economically nonviable. The low yield is due mainly to the slow growth rate of the plant tissue culture and the low production potential of the parent plant (47,48). Nowadays, with better understanding of the biosynthetic pathway of these natural pigments within the plant, improved reactor design, and advances in genetic engi- neering, one can actually improve the yield of these pigments.

Currently shikonin, a red dye, is produced commercially for cosmetics use by the Japanese company Mitsui Petrochemical Ltd. by plant tissue culture. At present one can optimize plant tissue culture cells to produce 845 times more shikonin than that from the plant roots (46,49). Meanwhile, Pirt et al. developed a bioreactor that is capable of cultivat- ing large amount of microalgae for the production of beta carotene for use as a food

Table 3 Properties of Major Natural Food Colors

Solubility

Stability

Tinctorial Color (pH of solution)

Microbe Metal strength Yellow

Name of pigment

G G G VG Yellow

Gardenia yellow

VG G VP

G G P P Yellow-orange

Safflower yellow

VG G VP

G G P P Yellow-orange

Annatto

G VP

G G G G VP Yellow-orange

Carrot ( β-carotene)

VP

VG P

G G G G VP Orange (acid)-red (neutral)-red purple

VG VG VG GG VP P (alkaline) Orange (⬍3)-red

Cochineal

VG G VP

VG G G G P Orange red-red (⬍3 not soluble)

Beet root

VG G VP

G G G G VG Orange red (acid)-red (neutral)-red

Monascus red

G VG VP

VG VG VG G VP P purple (alkaline) Red (3)-red purple (4–6)-blue (8)

Lac

VG VP

G G G G VP Red (3)-red purple (4–6)-blue (8)

Cora

VG G VP

G G G G VP P Red (3)-red purple (4–6)-blue (8)

Berry

VG G VP

G G G G VP P Purple red (acid)-red purple (alkaline)

Shiso

VG G VP

VG VG VG G VP P Purple red (acid)-red purple (alkaline)

Shikon

VG —

G G G G VP P Purple red (3)-red purple (4–6)-blue (8)

Red cabbage

VG G VP

G G G G VP P Purple red (3)-red purple (4–6)-blue (8)

Grape skin

VG G VP

G G G G VP P Brown

Grape juice

VG G VP

VG VG VG G G VG Brown (.3 not soluble)

Cacao

VG G VP

VG VG VG G G VG Green (.5 brown)

Kaoliang

VG G VP

G G G G P Green (alkaline)-brown

Chlorophyll

VG G VG VP

G P VG Blue

Tumeric

VG G P

G G G G P Blue

Gardenia blue

VG P

VG P

G G G G P Notes : VG ⫽ very good; G ⫽ good; P ⫽ poor; VP ⫽ very poor.

Spirulina

VG G VP VG G VP

Table 3 summarizes the properties of major natural food colorants. It is obvious that no single colorant is stable at the whole range of food preparation and processing conditions. Industrial users would have to choose a suitable colorant based on the physical and chemical properties of the food product and the methods for processing and preserving the product.

To summarize, there is a growing trend toward the use of natural colorants for food. The shift will not occur overnight but will rather be a slow process. The major obstacle is the economics of these natural colorants. Much work is still needed especially in increas- ing the product yield, before the natural food colorants can be economically viable.