WO1998007333A1

WO1998007333A1 - Production of pigments and potato starch products, and coloured products thereof

Info

Publication number: WO1998007333A1
Application number: PCT/NO1997/000212
Authority: WO
Inventors: Ole Ringdal; Henning S. Egede-Nissen; Øyvind Moksheim ANDERSEN
Original assignee: Norsk Hydro Asa; Norske Potetindustrier
Priority date: 1996-08-23
Filing date: 1997-08-20
Publication date: 1998-02-26
Also published as: NO302791B1; NO963544D0; NO963544L; AU4139197A

Abstract

The invention relates to a method for production of pigments and starch products from colourful potatoes of the species Solanum tuberosum. The invention also relates to coloured starch products and their production. The potatoes are disintegrated and separated into a potato fruit juice fractions and a solid fraction comprising starch, fibers etc. The preparation of water soluble pigments is integrated with a process for manufacturing starch products. The potato fruit juice is acidified and subjected to at least one filtration step for concentration before the water soluble pigments are isolated as a pigment concentrate. The solids fraction from the initial step is subjected to preparation of starch and starch derived products and optionally isolation of lipid soluble pigments. The water soluble pigments can be isolated by means of a chromatographic column or by use of nanofiltration.

Description

PRODUCTION OF PIGMENTS AND POTATO STARCH PRODUCTS, AND COLOURED PRODUCTS THEREOF

The invention relates to a method for production of pigments and starch products from potatoes which are washed and disintegrated and then separated into a potato fruit juice fraction and a solids fraction comprising starch, fibers, lipid soluble pigments etc. The invention also comprises coloured starch and/or glucose products.

Commercial utilisation of potatoes (Solatium tuberosum) either as a vegetable or in industrial processing is based on the "white" fleshed potato. The skin of this potato variety is pigmented while the flesh is white or bright yellow. The production of potato starch products is mainly based on "white" potatoes resulting in products like potato starch, maltodextrins and glucose syrups. These products are used in a variety of food and drink products were food colorants often are added in the process to give the appropriate colour of the finished product. The manufacture of potato starch is described in a paper by A.H.A de Willigen in chapter 8 in "Starch Production Technology" J.A.Radley , Applied Sci. Publrs. Ed. 1976,p 135-154, England.

Other varieties with coloured flesh are known, these potatoes are not utilised commercially. The pigments of colourful potatoes are either carotenoids (i.e. caroten, zeaxanthin, lutein) or anthocyanins (petanin). These groups of pigments are widespread in nature, but unfortunately there are few large sources easily available for commercial utilisation. Colourful potatoes can be grown in the same manor as ordinary white potatoes. The pigment concentration of the potatoes can be increased or modified either by natural selection or by gene-modification. Optimising growing conditions like light intensity, day length and nutrients can also influence the pigment concentration. The pigment production process is integrated in the potato starch factory. A further type of potatoes are the so called sweet potatos described in chapter 11 in "Starch Production Technology" J.A. Radley, Applied Sci. Publrs. Oct 1976. The sweet potato is an enlarged root, or root section, whereas the white potato is an underground stem tuber. Being a root, there are several structural and chemical differences between the sweet potato and the white potato. Lignocellulose occurs in the skin and at the ends of the former instead of the cork like material which forms the skin of the white potato.

Pigments can be produced as the main product from sweet potatos. Thus there is described in the Japanese application JP 7227246 pigment production from violet sweet potato. The pigments are extracted with alcohol under neutral or sligthly acidic conditions. The remains are used as raw material for various food products.

Natural colorants can also be extracted from coloured animal or plant materials. The pigments represent a minor constituents of the raw material so the production of colorants usually leads to large amounts of high volume and low value by-products. These by-products are often used as components in animal feeds. Many plant pigments (carotenoids and anthocyanins) are shown to be biological active in animals and humans, in particular the antioxidant properties are in focus.

In the production of potato starch there is produced a large amount of potato juice as a by-product in the process. This potato juice from "white" potatoes has low value and represents a significant cost because of the high BOD-values in the discharge.

Thus, it is a main object of the invention to provide an effective method for production of natural colorants and potato starch products not having the above mentioned disadvantages.

Another object of the invention is to provide coloured starch products in order to combine a colorant function with the texture properties of the starch products.

A further object is a combined process for starch and pigrftent production were use of washing water is optimized with regard to amounts and need for purification and thereby substantially redusing the effluents from the process. During the development of the new method , it was found that by integrating the production of pigments in a potato starch process the potato juice will have an increased value due to the pigment content from water soluble pigments like anthocyanins. As a pigment production process the large amounts of "by-product" (starch) also has an increased value due to the relatively high price of potato starch product as compared to feed applications. Further, the production of potato starch products from colourful potatoes would have a potential for producing directly coloured starch products for use in coloured foods and drinks. These products can be labelled as food ingredients rather than as additives, which have a dfferent procedure of legalisation.

The starch products and the pigments produced by the invented method can be used separately or in combination in feed, food, cosmetic, nutraceutical or pharmaceutical formulations.

The basic process according to the invention comprises that the potatoes used are colourful potatoes of the species Solanum tuberosum, and that the preparation of water soluble pigments is integrated with a process for manufacturing starch products. The potato fruit juice separated from the starch fraction is acidified and then subjected to at least one filtration step for concentration before the water soluble pigments are isolated as a pigment concentrate which then can be dried. The solids fraction comprising starch etc. is subjected to preparation of starch and starch derived products. Optionally can lipid soluble pigments be separated from said solids fraction.

A special embodyment of the invention comprises that the disintegration of the potatoes is performed by rasping or grinding in a vacuum chamber whereupon the formed potato mass is pumped directly to the separation step which preferably is performed by centrifugation.

Another embodyment comprises that the fruit juice is subjected to a first filtration step for removing solids and then to an ultrafiltration step for removing macromolecules whereupon the resulting solution is subjected to nanofiltration for forming the concentrated pigment solution. The pigment solution from the initial filtration steps can also be treated in a chromo- graphic column and the pigment will then be eluted with alcohol which is removed by evaporation from the pigment solution.

Recommended drying of the pigment solution will be by spray drying.

The solids fraction comprising starch etc. is subjected to a separation step in which moist fibers, lipid soluble pigments etc . are extracted and where the remaining starch fraction is subjected to refining and drying for forming starch products.

The starch products can further be processed by acid hydrolysis, filtration and evaporation for forming grucose syrup.

Coloured starch an/or glucose products can be formed directly by mixing the isolated water soluble pigments with the starch and/or glucose products of the process.

The lipid soluble pigments can be separated from the moist fiber fraction by extraction with an organic solvent.

The invention also comprises coloured starch and/or glucose products which are mixtures of starch and glucose products derived therefrom and the pigments from an integrated process for producing pigments and starch products.

The invention is further envisaged and explained below in connectionwith the description of the figures and the examples.

Fig 1 is a simplifed flow sheet of the different steps in the process.

Fig 2 shows the integration of the starch and pigment processes.

Figure 1 is a flow sheet showing the different steps in the invented process for production of potato starch products and pigments in the same process. The flow sheet is showing a potato starch process (1a), production of water soluble pigments like anthocyanins (1b), and production of lipid soluble pigments like carotenoids (1c). Potatoes are washed before they are grinded with rasps comprising fast rotating drums equipped with sawblades. In this way starch granules and potato juice will be released from the potato cells. Sulphur dioxide is added to inhibit oxidation and microbial growth.

The next step in a conventional potato starch process is normally extraction of starch from fibres with recirculated and undiluted potato juice. In the present invention separation of the grinded potatoes is performed before the extraction process to separate most of the potato juice with minimal deterioration of the pigments.

The residual is suspended with recirculated process water to an optimal concentration. Extraction of starch can be performed in centrisieves were cell walls (fibres) are retained, while the mixture of starch and rest potato juice is washed through the rotating sieve drum with recircultated process water.

Starch and diluted potato juice are separated for instance in a nozzle separator, and residual potato juice are washed out with clean water in two separate refining steps. Further processing include dewatering of the refined starch and finally drying in a conventional drier.

Potato starch can be converted to glucose syrups with acid or enzymatic hydrolysis. In the production of water soluble pigments like anthocyanins, fresh and undiluted potato juice is the main pigment source (figure 1b). The potato juice is first acidified with hydrochloric acid. The next step is to clarify the solution, preferably by centrifugation and filtering on a membrane filter. The remaining juice is concentrated before application. This can be performed on a column with XAD material. The anthocyanins are eluted with ethanol before drying.

In potatoes with a high carotenoid content, the pulp can be extracted by an organic solvent (i.e. CO₂ or ethylacetate) to produce a carotenoid extract (figure 1c).

The pigment can be remixed directly with the potato starch products to produce coloured powders or liquids. These coloured ingredients can be used in all products were the starch based products already are used together with colorants (i.e. soft drinks, candies, wine gums, jellies, jams etc.). Special applications for carotenoids are as pigments in feed for fish, shrimps and laying hens.

Figure 2 shows more in detail the utilisation of necessary water in the process and how some if the integration benefits of the process can be achieved. In the production line Ha colorful potatoes are first washed and cleaned in step 1 and washing water is recirculated. Then the potatoes are crushed and disintegrated in step 2 by rasping. This process is performed in a vacuum chamber. The potato mass is pumped directly to a centrifuge in step 3 where fruit juice is separated and transferred to step 14. The solids are transferred to a separation step 4 from which moist fibers are removed to step 10. The moist fiber fraction is dewatered in step 11 and the pulp is transferred to production line lie for further prosessing to lipid soluble pigments as described in connection with figure 1 or they can be used as cattle feed. The starch and remaining diluted fruit juice from step 4 are separated in step 5. The starch solution is refinned in step 7 to which water is added. Water from step 6 can be recirculated to step 4. The refinned starch is then dewatered and dried before being transferred to step 7. The starch in step 7 can be removed as a product, mixed with pigments 20 for making a coloured starch product or further processed in step 8 by acid hydrolysis and subsequent filtration and evaporation for forming glycose syrup 9 which is a product in itself or it can be mixed with pigments 20 for forming coloured glucose products.

In production line lib the potato juice from step 14 will then be used as raw material for pigment production. The juice is first prefiltered in step 15 and the solids fraction is removed while the pigment solution is subjected to ultrafiltration in step 16 where macromolecules are removed while the resulting pigment solution is subjected to nanofiltration in step 17. Alternatively pigments from this solution can be isolatd by chromatography as described in connection with figure 1. The resulting concentrated

pigment fraction 18 can be taken out as a product or then spray dried in step19 and the dry pigment can then be used as the final pigment product or mixed with the starch 7 and/or glycose syrup 9 for directly making coloured starch and/or syrup. The liquid from the dewatering step 11 goes to step 12 to which the remaining fruit juice from step 5 is added. At least part of the liquid from step 12 is recycled to step 4 and the remaining part can be concentraed by evaporation in step 12 leaving a concentrate which can be used as fertilizer.

The solids fraction from step 3 can optionally be applied as raw material for alcohol production and/or for making feed products as an alternative to starch production. Said alternative production can be performed in conventional manner and thereby utilizing most of the advantages of the basic steps of the present process.

The close integration of the production lines for starch products and pigments, respectively makes it possible to utelize water in a most efficient manner and substantially reduce the amuont of water to be purified before discharge. The integrated process will further give a flexible process with regard to product range.

Example 1

This example shows production according to the invention of starch and pigments.

100 kilo grams of coloured potatoes, (Solanum tuberosum var. 5001/5005) was washed and then 200ppm SO₂ in the form of sodium pyrosulfite were added and then hydrochloric acid was added in amounts to give a pH<3 (about 4 liters). The potatoes were disintegrated on a rasp and the resulting mass was rapidly transferred to a centrifuge. Said potato mass was centrifuged at 4000xg (where g is the constant of gravity) for 15 minutes and the fractions were then processed in the following way:

1) About 60 liters of coloured potato juice was filtered on a bag filter having pore openings of about 25μm. The juice was^'further clarified by cross flow ultra filtration on membranes having molecular weigth "cut offs" of 100000. The permeate was then transerred to an Amberlite XAD 7- column and washed with water for 1-2 hours. Adsorbed pigments were eluted with about 10 litre ethanole. The column was finally washed with water for about 30 minutes. The eluate was concentrated by evaporation at 30°C in vacuum to about 5 liters pigment solution. The ethanole was regenerated by destilation.

2) The solid phase containing the starch, fibre and some fruit juice was transferred directly to an excisting production line for potato flour, subsequent to the disintegration step. Further treatment was according to conventional procedure, i.e. fiber exstraction, subsequent reffining and drying. Calculated yield of starch from blue potato was 18 kilo grams potato flour (80% dry matter) for each 100 kilo gram blue potato.

Example 2

This example follows the same procedure as in example 1 , but with a modification of the treatment of potato juice for isolating the pigments.

1. About 60 litres of coloured potato juice was filtered on a bag filter having pore openings of about 25μm. The juice was further clarified by cross flow ultrafiltration on membranes having molecular weigth "cut off" of 100000. The permeate was then concentrated on a nanofilter membrane with "cut off" of 3000 to a pigment solution of about 5 litres..

Example 3

This example shows a modified treatment of the potatoes before the main treatment of the juice.

1. 100 kilo grams of coloured potatoes (Solanum tuberosum var. 5001/5005) was washed and then transferred to a rasp in a vacuum chamber. The chamber was evacuated and then the potatoes were disintegrated on the rasp. The resulting potato mass was pumped directly to a decanter centrifuge and separated into two fractions in modified gas atmosphere comprising nitrogen or carbon oxide. The potato juice was immediately acidified with hydrochloric acid to pH<3. Further treatment of the fractions could then be performed as described in example 1 and 2.

By applying the above modified procedure it will not be necessary to add SO₂ in the initial treatment step as described in example 1.

By the present invention an efficient and flexible process for integrated production of starch products and pigments has been obtained. The economic of the new process will be far better than for common separate starch and pigment processes. The problems related to wast products from such separate processes are substantially reduced by the new integrated process. More than 70% of the water soluble pigments present in the colourful potatoes are reclaimed. A further advantage is the reduced consumption of water comparred to conventional starch processes.

Claims

1. Method for production of pigments and starch products from potatoes which are washed and disintegrated and then separated into a potato juice fraction and a solids fraction comprising starch, fibers, lipid soluble pigments etc, characterized in that the potatoes used are colourful potatoes of the species Solatium tuberosum, and that the preparation of water soluble pigments is integratd with a process for manufacture of starch products , and that the potato fruit juice is acidified and then subjected to at least one filtration step for concentration before the water soluble pigments are isolated as a pigment concentrate which then can be dried, and that the solids fraction from the initial separation step is subjected to preparation of starch and starch derived products and that optionally lipid soluble pigments are separated from said solids fraction.

2. Method according to claim 1 , characterized in that the disintegration of the potatoes is performed by rasping or grinding in a vacuum chamber whereupon the formed potato mass is pumped directly to the separation step which preferably is performed by centrifugation.

3. Method according to claim 1 , characterized in that fruit juice is subjected to a first filtration step for removing of solids and then to a ultrafiltration step for removing macromolecules whereupon the resulting pigment solution is subjected to nanofiltration for forming a concentrated pigment solution.

4. Method according to claim 1, characterized in that the pigment solution from the initial filtration steps is treated in a chromatographic column and the pigments are eluted with alcohol which is removed from the pigment solution with evaporation.

5. Method according to claim 1, characterized in that the pigment solution is subjected to spray drying.

6. Method according to claim 1, characterized in that the solids fraction comprising starch etc. is subjected to a separation step in which moist fibers, lipid soluble pigments etc.are extracted and that the remaining starch fraction is subjected to refining and drying for forming starch products.

7. Method according to claim 1, characterized in that the starch products are further processed by acid hydrolysis, filtration and evaporation for forming glucose syrup.

8. Method according to claim 1 , characterized in that coloured starch and/or glucose products are formed directly by mixing the water soluble pigments with the starch and/or glucose products of the process..

9. Method according to claim 1 , characterized in that the lipid soluble pigments are separated from the moist fiber fraction by an organic solvent. Coloured potato products comprising pigments and starch and/or glucose products, characterized in that the potato products are mixtures of starch and/or glucose, derived from the starch, and pigments from an integrated process for producing pigments and starch products.