GB2118566A - Anthocyanin colorant from grape pomace - Google Patents

Abstract

Grape pomace is contacted with an aqueous extraction solvent containing HSO3 ions to extract anthocyanin-(HSO3) complex. The complex is recovered by treating the liquid extract phase with a non- ionic adsorbent to adsorb the complex. Anthocyanin colorant, free of the HSO3<->, ions is recovered by elution with an acidified organic solvent for anthocyanin. The anthocyanin colorant may be provided in dry form by drying the solvent solution.

Description

SPECIFICATION Anthocyanin colorant from grape pomace TECHNICAL FIELD This invention relates to colorants suitable for use in food products, to food products containing same, and to methods of obtaining the colorants.

Colorants in foods are either natural pigments or synthetic dyes or lakes. Since the number of synthetic colors is limited, there is need to further explore natural pigments as colorants. More specifically, there is extensive research in finding suitable natural red pigments as color additives.

The present invention relates in particular to an anthocyanin colorant obtained by extraction from grape pomace. These anthocyanin colorants are well known, but conventional extraction methods result in products having a generally low color strength.

It is an object of the present invention to provide a novel method of obtaining anthocyanin colorant having a high color strength. It is a further object to provide a process for concentrating anthocyanin colorant by removing sugars, organic acids and other water-soluble non-pigmented material from the pigment material in grape pomace, thus concentrating the pigment. It is a further object to provide an anthocyanin colorant of high color strength and to provide food products colored thereby.

DISCLOSURE OF THE INVENTION The foregoing and other objects which will be apparent to those of ordinary skill in the art are achieved in accordance with the present invention by providing a method of producing an anthocyanin colorant from grape pomace which comprises: contacting grape pomace with an aqueous extraction solvent containing HSO3- ions to extract an anthocyanin-(HSO3) complex, removing said aqueous extraction solvent from said grape pomace, removing undissolved solids from said aqueous extraction solvent, contacting said aqueous extraction solvent with a nonionic adsorbent to adsorb said anthocyanin-(HSO3) complex from said aqueous extraction solvent, separating said aqueous extraction solvent and said adsorbent, washing said adsorbent with water to remove soluble sugar, organic acid and other water soluble nonpigmented material, contacting the separated adsorbent with an acidified organic eluant, said acidified organic eluant comprising an organic solvent for anthocyanins, to produce a product solution comprising anthocyanin free of said HSO3- ions dissolved in said organic eluant, and separating said product solution from said adsorbent, by providing an anthocyanin colorant produced by the foregoing process, and by providing food products colored therewith.

In accordance with the present invention, grape pomace is contacted with an aqueous extraction solvent containing HSO3- ions. Grape pomace is widely available as a waste material, particularly in wine-making regions, and is preferably de-seeded prior to extraction. De-seeding may be effected in any conventional manner such as by screening.

The de-seeded grape pomace is then subjected to extraction by contact with an aqueous extraction solvent containing HSO3- ions. The amount of HSO3- ions, expressed as weight percent SO2 based on the weight of the solids content of the grape pomace, should not exceed about 0.5% and is preferably between 0.05 and 0.2%.

The aqueous extraction solvent preferably contains one or more organic solvents miscible in water and capable of dissolving anthocyanins. Preferably, the amount of organic solvent is 25-75% by volume based on the volume of the extraction solvent. While various solvents can be used, ethyl alcohol is preferred, an the preferred extraction solvent contains 55 parts by volume water, 45 parts by volume alcohol, and HSO3- ions in an amount of up to 0.5% by weight SO2 based on the amount of grape pomace solids in contact with the extraction solvent.

It is preferred to use a minimum amount of extraction solvent and a practical minimum is about + or 1 volume of extraction solvent per volume of grape pomace treated. Larger quantities may, of course, be used, but it is preferred to use a minimum amount to minimize the cost of recovery of the pigment. In general, a suitable range is 0.5 to 5 volumes of extraction solvent per volume of grape pomace treated, and a preferred range is about 1 to 2.

The HSO3- ions can be added in any convenient manner such as by the addition of a sulfurous acid and the like. However, it is preferred to simply dissolve sodium metabisulfide into the aqueous extraction solvent.

The duration of the contact time between the grape pomace and the extraction solvent is preferably kept to a minimum for purposes of economy. A few hours is usually sufficient and a preferred minimum soak time is about two hours. For most operations, over-night soaking will be convenient and is preferred for that reason. In general, a soak time of from 2 to 1 6 hours will be suitable and a preferred range is from 2 to 8 hours.

The extract solution, which contains the anthocyanin-(HSO3) complex, is then removed from the pomace in any convenient manner such as by pressing. The extract solution is then filtered to remove undissolved solids and this is done in any convenient manner, such as in a multi-plate filter press.

After filtering, the extract solution is then contacted with a non-ionic adsorbent to adsorb the anthocyanin-(HSO3) complex from the solution. Among the high surface area, non-ionic materials useful as adsorbents herein ar any of the known non-ionogenic, maeroretricular resins.

For example, there may be used the granular cross-linked polymers of this character prepared by suspension polymerization of polymerizable ethylencially unsaturated molecules comprising about 2 to 100, preferably at least 50, weight percent of at least one poly(vinyl) benzene monomer seleeted from the group consisting of divinylbenzene, trivinylbenzene, alkyldivinylben- zenes having from 1 to 4 alkyl groups of 1 to 2 carbon atoms substituted in the benzene nucleus and alkytrivinyl benzenes having 1 to 3 alkyl groups of 1 to 2 carbon atoms substituted in the benzene nucleus.Besides the homopolymers and copolymers of these poly(vinyl)benzene monomers, one or more of them may be copolymerized with up to 98%, preferably less than 50%, {by weight of the total monomer mixture) of (1) monoethylenically unsaturated monomers (e.g., styrene), or (2) polyethylenically unsaturated monomers other than the poly(vinyl)benzenes just defined (e.g., divinylpyridine), or (3) a mixture of (1) and (2). Macroreticular acrylic and/or styrene and/or divinylbenzene adsorption resins devoid of ion exchange functionality have proven particularly useful in the process of this invention.

Adsorbent resins of the aforementioned-type are known and commercially available and more fully described in U.S. Patent No. 3,531,463 to Gustafson (Rohm s Haas Company) which is hereby incorporated by reference.

Typically, the adsorbent polymer, which under most conditions is of 1 6 to 100 mesh in particle size, and may be as small as about 400 mesh, has a porosity of at least 10% (percent volume of pores in the resin body or bodies) and a surface area of at least 10 square meters per gram of the resin (up to 2,000 square meters per gram). Cross-linked resins having solubility parameters (units: calories/cc) of at least about 8.5 and up to 1 5 or more are suitable for use.

The preferred resin size is from about 40-50 mesh (U.S Standard).

Adsorption of the anthocyanin complex may be carried out in a simple batch operation, in a continuous procedure, or in various other operating modes available to those skilled in the art.

In a fixed-bed batch operation, the adsorbent may be supported in a suitable cell or vessel which in most practical operations normally takes the form of a tower or column suitably packed with the adsorbent which may be of any suitable size or mesh. The extract is passed through the adsorption bed at a suitable rate, preferably from top to bottom, so that the complex may be adsorbed.

The extract solution will normally have a solids content of 5 to 30% by weight, depending largely on the volume ratio or extraction solvent to grape pomace. When the extract contacts the adsorbent, solids will be adsorbed until the adsorbtion capacity of the adsorbent medium in the particular system is reached. When adsorption occurs in a single column, it will normally be the practice to cut off the flow of extract into the column before a significant amount of anthocyanin complex is detected exiting from the column. In this manner, a substantially anthocyanin-free extract is obtained which may be recycled for additional processing if desired.

In addition to the anthocyanin complex, various other compounds present in the extract are also adsorbed. For example, polypeptides and solubilized proteins may be present in the adsorbed material. However, the advantage of the process described herein is that the anthocyanin complex present in the aqueous extract is concentrated so that a large increase in tinctorial strength of the pigment is obtained.

The adsorption bed containing the adsorbed anthocyanin complex is rinsed with water in order to remove from the adsorbent water soluble non pigmented material, sugar, organic acid and solid particles which are merely adhered to the particle surfaces and have not, in fact, been adsorbed. In column operation, this water rinse will normally be effected by passing tap water (about 1 5 C) through the adsorbent bed.

The adsorbed anthocyanin complex is then eluted from the adsorbent with an acidified organic solvent. The preferred solvent is 100% ethanol acidified with a small amount of mineral acid. The acid functions to break the anthocyanin-(HSO3) complex such that anthocyanin-(HSO3) complex such that anthocyanin, free of HSO3 ions, is eluted from the adsorbent. Various organic solvents for anthocyanins may be used, but of these, alcohols such as methanol, ethanol, n-propanol, isopropanol, and mixtures thereof, are preferred. The elutant is preferably anhydrous, but a small quantity of water, such as that which is introduced when adding concentrated acid to acidifiy the elutant, is tolerable. Additional water is also present, of course, in the adsorbent bed. In general, the water content of the elutant as initially used is not more than about 2% by volume and preferably not more than about 1% by volume.

The acid used to acidify the elutant can be any food grade acid of sufficient acidity to effect break-up of the adsorbed complex such that the anthocyanin which is eluted is free of HSO3ions. Mineral acids are suitable and, of these, hydrochloric acid is preferred. The amount of acid can vary considerably but, in general, a sufficient amount is added to obtain a pH of less than about 3.5.

Recovery of the anthocyanin from the elutant can be accomplished in any convenient manner such as by evaporation, distillation, spray drying, freeze drying, and the like. Preferably, recovery is accomplished by evaporation to effect concentration of the solution followed by spray drying with a suitable carrier such as dextrin.

BEST MODE FOR CARRYING OUT THE INVENTION EXAMPLE 1 De-seeded grape pomace is soaked with an equal volume of extracting solvent which contains approximately 0.075% w/v HSO3-, 40% v/v ethanol and 60% v/v water. After overnight soaking, the pomace is pressed to extract the solvent containing an anthocyanin-(HSO3) complex. After filtering to remove undissolved solids, the extract phase is passed through a fixed bed (2.5 cm diameter by 120 cm high) of a nonionic, high surface area, macroreticular, styrenedivinylbenzene copolymer, prepared by suspension polymerization of a monomer fraction containing in excess of 80% by weight divinylbenzene.This adsorbent polymer is employed in the form of 20 to 50 U.S. mesh size beads and is available from Rohm and Haas Co., Philadelphia, PA 1 9105 under the commercial designation "Amberlite XAD-4." Thereafter, 2 bed volumes of water, at about 15"C, are passed through the resin bed at the rate of 1 bed volume per hour to remove water soluble non pigmented material, sugar, organic acids and the non-adsorbed solids. The adsorbent bed is then eluted with a solution of 100% ethanol containing 0.1% by weight of concentrated hydrochloric acid. The elutant, which contains anthocyanin free of HSO3- ions is then evaporated in a rotary evaporator and spray dried with a dextrin carrier.The dried product contains about 60% grape solids and 40% dextrin carrier and the overall yield of grape solids based on the solids content of the pomace is about 10%. The colorant is many times stronger in color than colorants obtained by conventional extraction methods. The strong coloration of the present product is believed to be due at least in part by the fact that sugars, organic acids and other non-pigmented materials are separated from the anthocyanin colorant during the process.

EXAMPLE 2 The grape colorant of Example 1 is used to color a dry beverage mix having the following formula: Malic Acid 3.1 5 grams Monocalcium Phosphate 2.65 grams Cherry Flavor (IFF 1354G603) 0.32 grams Grape Process of Example 1 0.41 grams Vitamin C 0.08 grams FDBC Blue #1 0.0002 grams When admixed in 2 quarts of water, the beverage is comparable in color to a beverage made from the same mix in which FD and C Red &num;40 is used in an amount of 0.1 4 grams.

Claims (10)

1. A method of producing an anthocyanin colorant from grape pomace which comprises: contacting grape pomace with an aqueous extraction solvent containing HSO3- ions to extract an anthocyanin-(HSO3) complex; removing said aqueous extraction solvent from said grape pomace; removing undissolved solids from said aqueous extraction solvent; contacting said aqueous extraction solvent with a non-ionc adsorbent to adsorb said anthocyanin-(HS03) complex from said aqueous extraction solvent; separating said aqueous extraction solvent and said adsorbent; contacting the separated adsorbent with water to remove water soluble non pigmented material;; contacting the separated adsorbent with an acidified organic eluant, said acidified organic eluant comprising an organic solvent for anthocyanins, to produce a product solution comprising anthocyanin free of said HSO3- ions dissolved in said organic eluant; and separating said product solution from said adsorbent.

2. A method according to claim 1 further comprising the step of removing said organic eluant from said product solution to provide a product comprising anthocyanin pigment.

3. A method according to claim 2 wherein at least a portion of said organic eluant is removed by evaporating said product solution.

4. A method according to claim 2 wherein a portion of said organic solvent is removed by evaporation to provide a concentrated product solution and a further portion is removed by spray drying said concentrated product solution to provide a dry, particulate anthocyanin pigment.

5. A method according to any one of claims 1 to 4 wherein the HSO3- ions are present in said aqueous extraction solvent in an amount of up to .05% expressed as weight percent SO2 based on the wieght of the solids content of the grape pomace.

6. A method according to any one of claims 1 to 5 wherein said aqueous extraction solvent comprises 25-75% by volume of an organic solvent miscible in water and capable of dissolving anthocyanins.

7. A method according to any one of claims 1 to 6 wherein said non-ionic adsorbent comprises a macroreticular resin.

8. A method according to any one of claims 1 to 7 wherein said acidified organic eluant comprises an organic alcohol, a mineral acid, and not more than about 2% water.

9. A method of producing an anthocyanin colorant substantially a hereinbefore specifically described with particular reference to the Examples.

10. An anthocyanin colorant when produced by a method as claimed in any one of claims 1 to 9.