TECHNICAL FIELD

This invention relates to a food composition containing phytic acid. In particular, the invention relates to a food composition fortified with iron or zinc ions that uses phytic acid to enhance the bioavailability of iron or zinc to consumers.

BACKGROUND

Nutritional mineral deficiencies in human populations, also referred as micronutrient malnutrition, are especially widespread in developing countries. Deficiencies in iron and zinc are known to be especially prevalent and are associated with a range of health problems. For example, inadequate intake of dietary iron impairs work performance, increases maternal and child mortality, and can result in poor cognitive development in children. Iron deficiency affects more than two billion people globally. Zinc deficiency is also widespread, and is considered to be the fourth most important global nutrient deficiency.

Iron and zinc deficiencies originate when physiological requirements cannot be met by mineral absorption from the diet. Dietary iron bioavailability is low in populations having monotonous plant-based diets with little meat. A major cause of the low bioavailability of iron is related to the presence of so-called anti-nutritional factors that are naturally present in cereals and legumes. These anti-nutritional factors form insoluble complexes with iron and hence iron absorption is poor.

Fortifying foods with iron or zinc is well known, but can be problematic. The major difficulty with fortifying foods with iron is caused by the incompatibility of high bioavailability and high stability of iron compounds. That is, the most bioavailable compounds (i.e., water- soluble iron) are those that are the most reactive within the food matrix. For example, ferrous sulphate, which is the reference iron compound for food fortification in humans, causes sensory changes in the food vehicle in presence of polyphenols or high amounts of lipids. On the other hand, more stable iron sources, which are typically water-insoluble (e.g. ferric pyrophosphate), have relatively low bioavailability compared to water solu ble compounds.

Encapsulated ferrous sulphate has been considered as a potential solution to this problem , i .e. using a h ighly bioavailable iron sou rce whi le maintai ning stabi lity by encapsulation in the formulation. But bioavailability is then highly dependent on the coating used, and in many cases bioavailability of the coated iron source is reduced. Additionally, the encapsulation of iron increases production costs in comparison to the use of non- encapsulated ferrous sulphate. Moreover, most coatings used for encapsulation of this type are lipid based, which means they would melt during different heat treatment stages of the manufacture of many food products.

Other techniques for improving the bioavailability of iron or zinc from foods are known. One example is described in EP 1743530 and EP 1792544 where a food product is fortified with iron or zinc in the form of iron- or zinc-containing nano-particles that have been stabilised with biopolymers. US 10/969,434 (published as US 2005-0053696) describes the iron fortification of foods and beverages using ferric EDTA (ethylenediaminetetraacetic acid) as an iron source. Ferric EDTA has good bioavailability and stability, but the use of EDTA in food products is meeting with increased consumer resistance. US 6,344,223 describes the fortification of foods with compounds prepared from iron , phosphate and ammonium compounds. Such compounds are said to possess strong iron-ligand bonds which, on the one hand, prevent the reactivity of free iron and, on the other hand, dissociate in the acidic environment of the stomach to provide a high bioavailability of iron.

There are numerous other approaches to fortifying food products with iron, but which are targeted at addressing other problems such as off-colour formation in foods caused by iron . More recent examples include those described in WO 2009/068378 and WO 2010/086192. WO 2009/068378 describes the use of a selected group of known iron compounds in bou illon cubes wh ich cause less off-colour compared with other iron compounds. WO 2010/086192 describes a dry food concentrate containing specified levels of salt, MSG, an iron compound, and an organic acid (e.g. citric acid) for reducing the off- colour effect.

As mentioned above, compounds that form insoluble complexes with iron, and hence reduce iron bioavailability, are considered anti-nutritional. Phytic acid is one such compound. It complexes iron and therefore is regarded as an undesirable component in foods. One attempt to address this problem is described in WO 2004/071218. Phytic acid, or phytate as referred to in that document, is incorporated into a food product along with cations to be delivered by the food. The cations are bound to the phytate. Phytase is added to hydrolyse the phytate-cation complexes in the gastrointestinal tract thereby releasing the cations and increasing their bioavailability.

Surprisingly however, the inventors have found that, under certain conditions, with no enzymes added, phytic acid may be used in food or beverage compositions to deliver iron and/or zinc with good bioavailability and without adversely affecting the organoleptic properties such as for example the stability of color of the food product.

An object of the present invention is therefore to provide a food composition fortified with iron and/or zinc that at least goes part way to overcoming one or more of the above disadvantages of existing fortified foods, or at least provides a useful alternative. SUMMARY OF THE INVENTION

In a first aspect of the invention there is provided a food or beverage composition comprising:

(a) metal ions selected from ferrous iron ions; and

(b) phytic acid;

wherein some or all of the phytic acid is present in the form of a water soluble complex with some or all of the metal ions.

Preferably, the molar ratio of metal ions to phytic acid is in the range 0.1 : 1 to 5: 1 , preferably 0.1 :1 to 3:1 , more preferably the ratio is 1 :1 .

In some preferred embodiments of the invention, the metal ions further comprise zinc ions. Thereby, the food composition may include both iron and zinc ions.

It is also preferred that the food composition contains no EDTA.

The phytic acid may be obtained from any suitable source, but is preferably obtained from cereals, beans, tubers, fruit, leafy vegetables, or nuts.

The food or beverage composition preferably has a pH in the range 2 to 7, preferably in the range 2 to 6, more preferably in the range 3 to 5.

Preferably, the food or beverage composition of the invention is used as a fortificant in a food product such as a seasoning, bouillon, sauce, beverage, milk powder, milk drink, pet food, cereal, or baby food. The food or beverage composition may be a solution or suspension in water, a powder, or granules. The powder or granules are preferably soluble in water.

In a second aspect of the invention, there is provided a method for preparing a food or beverage composition containing iron and/or zinc ions, the method comprising the steps of:

- mixing phytic acid with a source of iron and/or zinc ions in water;

heating the mixture to a temperature of at least 80°C, preferably of at least 90°C, so that some or all of the phytic acid forms a water soluble complex with some or all of the metal ions;

adding the mixture to a food or beverage composition to be fortified with iron and/or zinc ions.

In a preferred method of the invention, the molar ratio of iron and/or zinc ions to phytic acid is in the range 0.1 : 1 to 5: 1 , preferably 0.1 : 1 to 3:1 , more preferably the ratio is 1 :1.

Preferred sources of iron ions include ferrous sulphate, ferric sulfate, ferrous lactate, ferrous gluconate, ferrous fumarate, ferric citrate, ferric choline citrate, or ferric ammonium citrate. Preferred sources of zinc ions include zinc chloride, zinc sulfate, zinc lactate, or zinc citrate.

The method may also include a step of removing water to give a solid product, such as powder or granules, or any other kind of particulate matter, which product is soluble in water.

In a further aspect, the invention relates to a use of a water soluble complex formed between metal ions selected from iron and/or zinc ions and phytic acid for fortifying a food or beverage composition with iron and/or zinc ions. Particularly, the invention relates to such use for improving the stability of the color of a food or beverage composition fortified with iron and/or zinc ions. Particularly, the invention also relates to a use of said water soluble complex for improving the bioavailability of iron and/or zinc ions in a subject, and particularly for a subject in need thereof.

In a still further aspect, the invention pertains to a food or beverage product fortified in iron and/or zinc ions by the addition of a water soluble complex formed between metal ions selected from iron and/or zinc ions and phytic acid. Such a food or beverage product can be a seasoning, bouillon, sauce, bottled water, milk powder, milk drink, milk based desert, a pet food, cereal, pasta or noodle product or a baby food.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a graph showing the complexation properties of phytic acid in presence of Fe ²⁺ .

Figure 2 is a graph showing the potential of phytic acid as a delivery system for minerals.

Figure 3 shows the colour stability of Fe:PA complexes (1 :1 molar ratio) in vegetable bouillon.

Figure 4 shows the colour stability of Fe:Zn:PA complexes (1 : 1 : 1 molar ratio) in vegetable bouillon. Figure 5 shows the colour stability of PA: Fe Complexes obtained by the method of preparation comprising a heating or a non-heating step.

DETAILED DESCRIPTION

The invention relates to a food or beverage composition comprising ferrous iron ions and phytic acid, where some or all of the phytic acid is present in the form of a water soluble complex with some or all of the metal ions. The molar ratio of metal ions to phytic acid may be any ratio providing water soluble complex formation, for example in the range 0.1 :1 to 5:1 , preferably in the range 0.1 : 1 to 3:1 , more preferably 1 : 1 . The invention also relates to a method for preparing such a food or beverage composition. The food or beverage composition is used as a fortificant, i.e. an agent for fortifying a food product with iron or zinc (or both). The presence of soluble phytic acid complexes improves the bioavailability of the iron or zinc.

In the context of this invention, the term "phytic acid" relates to a myoinositol, i.e. from myoinositol monophosphate (InsP) through to myo-inositol hexakisphosphate (lnsP6).

In the context of this invention, the term "phytic acid" also includes any salt or ester of phytic acid capable of forming phytic acid in the food or beverage composition of the invention.

As used in this specification, the words "comprises", "comprising", and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean "including, but not limited to".

Further, any reference in this specification to prior art documents is not intended to be an admission that they are widely known or form part of the common general knowledge in the field.

The invention is based on the development of methods for making stable metal ion complexes with phytic acid that are soluble in an aqueous medium and which can be added to food products without adversely impacting on the quality of the product. The principal aspects of the methods are: 1 ) the molar ratio of phytic acid to metal ions; 2) pH conditions for the formation of the complexes; 3) temperature conditions; 4) time, and 5) ionic strength of the media. The method is especially useful for the delivery of multiple metal ion fortifying agents in a single ingredient preparation.

The invention provides a food or beverage composition containing iron or zinc ions that uses phytic acid to enhance the bioavailability of the iron or zinc in fortified food products. Historically, the use of phytic acid in food products has been avoided due to its potential for binding positively charged proteins, amino acids and multivalent cations. The resulting complexes are usually insoluble under physiological conditions, which means that digestion by humans is difficult, and the iron or zinc is therefore less available for absorption. Consequently, phytic acid has traditionally been considered anti-nutritional.

The food products that may be formed from the composition of the invention, or to which the composition of the invention can be added, include any product capable of being fortified with iron or zinc, and include, but are not limited to, dairy products such as milk powder and milk drinks, pet food , savoury products such as seasonings, bouillons and sauces, cereals, baby foods, and beverages.

The inventors have now found that, in contrast to long-held beliefs in the food area, phytic acid can be used as an effective delivery mechanism for iron and zinc. Furthermore, phytic acid can be regarded as a natural ingredient for delivering high bioavailability of iron and zinc because it can be readily obtained from natural sources. Such sources include cereals (e.g. wheat, corn, oat, barley, sorghum, millets, bran), beans (e.g. peas, lentils, white beans, soybeans), tubers (e.g. potato, yam, sweet potato, sugar beet), fruit (e.g. plantain, dates, strawberry, avocado), leafy vegetables (e.g. spinach, red cabbage, okra, cauliflower, carrots, tomato), nuts (e.g. hazelnut, walnut, almond, cashew), and other foods such as coconut, sesame seeds, and coriander.

The seasoning ingredients of the food composition may be any seasonings suitable for a desired food composition and include, without any limitation , flavour agents, salt, monosodium glutamate, spices, and herbs.

Soluble complexes may be formed between phytic acid and iron or zinc under any suitable temperature, pH, and time conditions, for example by heating together at 90-95 °C for 45 min in acidified aqueous solution (at pH 3.6) in a molar ratio in the range 0.1 -5:1 :1 iron/zinc:PA. The complexes formed can be used as an iron or zinc fortification system in food products which does not deleteriously affect the organoleptic properties of the food. It was found that complexed iron/zinc remained stable in bouillon cubes with no colour change or off -flavour production.

Iron delivery from iron:phytic acid complexes was tested via in vitro digestion. Initially the complexes were formed at pH 3.6 and subsequently tested under simulated gastric and duodenal conditions. The results showed that the complexes remained stable under gastric conditions (i.e. pH 2.0) and iron was released under simulated duodenal conditions (i.e. pH 6.5). In essence, at pH 3.6, all Fe ²⁺ complexes with phytic acid, but at pH 6.5 the phytic acid releases the Fe ²⁺ making it bioaccessible. These results show the potential of phytic acid as carrier to deliver iron during its transit through duodenum.

The iron ions may be obtained from any appropriate source including, but not limited to, ferrous sulphate, ferric sulfate, ferrous lactate, ferrous gluconate, ferrous fumarate, ferric citrate, ferric choline citrate, and ferric ammonium citrate. The source of zinc ions may be zinc chloride, zinc sulfate, zinc lactate, zinc gluconate and zinc citrate, or any other suitable source.

The food or beverage composition may be in any suitable form, for example, a solution or suspension in water, or in solid form, such as a powder, granules, or any other suitable particulate matter. The food composition may be used in the preparation of any iron or zinc fortified food product.

In the method of the invention, a food or beverage composition containing iron or zinc ions, is prepared by mixing phytic acid with seasoning ingredients in water and a source of iron or zinc ions so that the molar ratio of iron and/or zinc ions to phytic acid is in the range 0.1 : 1 to 5: 1 preferably in the range 0.1 : 1 to 3: 1 , more preferably in the range 0.1 : 1 , and heating the mixture to a temperature of at least 80°C. The resulting mixture may be further processed to give the food or beverage composition or a product prepared from the food composition. Further processing may include, for example, drying to remove water by any standard drying technique such as freeze drying or spray drying. The dried product is preferably water soluble, i.e. redissolvable in water.

Those skilled in the art will understand that they can freely combine all features of the present invention disclosed herein. In particular, features described for the composition of the present invention may be combined with the method, the use and the food or beverage product of the present invention and vice versa. Further, features described for different embodiments of the present invention may be combined.

Further advantages and features of the present invention are apparent from the figures and examples.

EXAMPLES

The invention is further described with reference to the following examples. It will be appreciated that the invention as claimed is not intended to be limited in any way by these examples. Example 1: Preparation of Fe:Phytic acid complexes as fortificant for bouillon

To evaluate the colour of fortified broth, ferrous sulphate (38 mg) was mixed in 250 mL of acidified Milli-Q water (pH 3.6) in a beaker with approximately 163 mg of phytic acid (PA) to achieve a molar ration of 1 :1 iron:PA. The mixture was heated at 90 °C for 45 min under continuous mixing conditions at 300 rpm. The mixture was then placed in an ice bath for 15 min. The pH of the mixture was adjusted to different pHs in the range of 5.0 to 6.0. Vegetable bouillon (5 g) was added and the mixture boiled for 10 min. Samples containing the same amount of vegetable bouillon, but no iron, in Milli-Q water at different pHs, were prepared as positive controls. Samples containing the same amount of vegetable bouillon, as well as iron (FeS0 ₄ ), in Milli-Q water at different pHs were used as negative controls. Table 1 and Figure 3 show the results of the colour analysis. It is generally accepted that total chroma variation (ΔΕ) values >5.0 are noticeable by the naked eye.

Tablel: Total chroma variation (ΔΕ) of iron-fortified vegetable bouillon

Iron Fortificant system ΔΕ (pH 5.0) ΔΕ (pH 6.0)

FeS0 ₄ 5.29 7.53

FeS0 ₄ :PA (1 :1 molar ratio) 3.43 4.09 The results presented in Table 1 show the protective effect that phytic acid has on FeS0 ₄ when used as fortificant in vegetable bouillons. Bouillons fortified with iron:PA complexes showed a better colour profile (ΔΕ<5.0) at different pH conditions than bouillon solutions fortified with FeS0 ₄ , as indicated by a lower value of ΔΕ. Overall, the off-colour observed in bouillons fortified with FeS0 ₄ was not noticed or very limited with iron:PA complexes compared to control food products resulting from vegetable bouillons without any added iron (Figure 3).

The complexing properties of phytic acid with iron are shown in Figure 1 . A control sample containing iron but no PA was also used to track the solubility of the mineral. It can be seen that phytic acid can form complexes with up to 5 moles of iron. Additional iron will remain free in solution without any possibility of complexation with phytic acid. The tested samples did not show any precipitate formation, meaning that iron was either complexed by PA or free in solution.

Example 2: Preparation of Fe:Zn: Phytic acid complexes as fortificant for bouillon

Ferrous sulphate (38 mg) was mixed in 250 mL of acidified Milli-Q water (pH 3.6) in a beaker with approximately 163 mg of phytic acid and 34 mg of zinc chloride to achieve a molar ratio of 1 : 1 :1 iron:zinc:PA. The mixture was heated at 90 °C for 45 min under continuous mixing conditions at 300 rpm. The mixture was then placed in an ice bath for 15 min. Vegetable bouillon (5 g) was added and the mixture boiled for 1 0 min . Samples containing the same amount of vegetable bouillon , but no iron , in Milli-Q water, were prepared as positive controls. Samples containing the same amount of vegetable bouillon, as well as iron, in Milli-Q water were used as negative controls. Similar to Example 1 , the sample containing the Fe: PA complexes also contain zinc in a m ola r ratio of 1 :1 :1 iron:zinc:PA. The results are presented in Figure 4. Surprisingly, no colour difference between the bouillon containing 1 :1 :1 Fe:Zn:PA complexes and the negative control was observed. Example 3: In vitro study of complex stability during digestion

Gastric conditions: 500 μΙ_ of solution containing either of Fe:PA or Fe:EDTA (1 :1 mol ratio) was diluted in 950 μΙ_ of gastric electrolyte solution and incubated at 37 °C for 2 hours at 350 rpm. A solution of FeS0 ₄ was used as a control. Free iron in solution present in the samples after the treatment was analyzed using an ion chromatography ICS 5000 Dionex following the standard procedure proposed by the supplier (Dionex Technical Note 10). The gastric electrolyte solution was prepared as follows: 51 g of stomach electrolyte solution (concentrated 10x) and 3.58 g of 1 M sodium bicarbonate solution were added to 445 g Milli- Q water. The pH of the resulting solution was adjusted to 2.0 with 1 M HCI.

Duodenal conditions: 500 μΙ_ of solution containing either of Fe:PA or Fe:EDTA (1 :1 mol ratio) was diluted in 950 μΙ_ small intestinal electrolyte solution and incubated at 37 °C for 2 hours at 350 rpm. A solution of FeS0 ₄ was used as a control. Free iron in solution present in the samples after the treatment was analyzed using an ion chromatography ICS 5000 Dionex following the standard procedure proposed by the supplier (Dionex Technical Note 10). The small intestinal electrolyte solution was prepared as follows: 21 .75 g of small intestinal electrolyte (concentrated 25x) was diluted in 478.25 g Milli-Q Water. The pH of the resulting solution was adjusted to 6.5 with NaOH 1 M.

Figure 2 shows that iron remained complexed by either PA or EDTA during gastric digestion, but is subsequently released under duodenal conditions. The values of free iron in solutions are comparable to the control containing FeS0 ₄ , which shows the potential of PA as a natural analogue of EDTA for delivering iron during its transit through the duodenum.

It is to be appreciated that although the invention has been described with reference to specific embodiments, variations and modifications may be made without departing from the scope of the invention as defined in the claims. Furthermore, where known equivalents exist to specific features, such equivalents are incorporated as if specifically referred to in this specification.

Example 4: Color stability of PA:Fe complexes

Fe:Phytic acid complex formation (method of preparation with heating step):

I n a 1 L Duran bottle equipped with magnetic stirrer, dodecasodium Phytate (A&Z Food additives, 734.4 mg, 0.80 mmol) was diluted with MilliQ water (800 mL), and the pH adjusted to 3.6. In parallel, FeS0 ₄ heptahydrate (Dr Paul Lohmann GmbH Germany, 180.1 mg, 0.65 mmol) or Fe(lll)CI ₃ (Sigma Aldrich, 175.7 mg, 0.65 mmol) was dissolved in MilliQ water (200 mL) previously buffered at pH 3.6 with 0.1 M HCI. The two solutions we mixed together under stirring and then heat treated at 125 °C for 12 minutes to give a colourless solution. Negative results of the ferrozine method indicated completed formation of the complex.

Fe:Phvtic acid complex formation (method of preparation with no heating step according to Morris and Ellis, J Nutr, vol 106 no.6, 1976, pages 753-760):

In a 1 L Duran bottle equipped with magnetic stirrer, dodecasodium Phytate (A&Z Food additives, 734.4 mg, 0.80 mmol) was diluted with MilliQ water (800 mL), and the pH adjusted to 3.6. In parallel, FeS0 ₄ heptahydrate (Dr Paul Lohmann GmbH Germany, 180.1 mg, 0.65 mmol) or Fe(lll)CI ₃ (Sigma Aldrich, 175.7 mg, 0.65 mmol) was dissolved in MilliQ water (200 mL) previously buffered at pH 3.6 with 0.1 M HCI. The two solutions we mixed together under stirring for 10 minutes to give a final colourless solution. Positive results of the ferrozine method indicated incomplete formation of the complex. pH adjustment of the Fe: Phytic acid complex:

In order to use the Fe:PA complexes in a food preparation (i.e., chicken bouillon) the pH of the solution was adjusted to the value of 5.5-6.0 using 1 M NaOH. The results are presented in figure 5 and the table below:

Fe:PA complex preparation

Heated sample: Non-heated sample:

L ^* :82 L ^* :80.3

a ^* :-0.7 a ^* :-1.1

b ^* :3.3 b ^* :13.7

AEab ^* = 10.6

The color analysis was carried out using the CI E Lab ^* notation . I n the I nternational Commission on Illumination (CIE), a color is represented by a point in a color space. The coordinates of such a point are: the luminosity L (L=0: black, L=100: white), a* the amount of red and green (a ^* positive: red, a ^* negative: green), and fe* the amount of yellow and blue (b ^* positive: yellow, b ^* negative: blue). The Color analysis was registered using a computer controlled digital camera system (DigiEye, Verivide) with a D65 light source.

While the heated solution remained transparent, the non-heated, had a significant colour change AEab ^* = 10.6, indicating that non-bound FeS0 ₄ was present in solution. The change in colour is likely to be due to the oxidation reaction fromFe ²⁺ to Fe ³⁺ due to the increase of pH. The solutions formed using Fe(lll) did not show any sign of colour change while the pH was adjusted.

Influence of the fortificant on the colour aspect of reconstituted bouillon

Standard bouillon was prepared by adding the dehydrated powder (10 g) to boiling water

(500 mL). The reconstituted bouillon was stirred to have uniform powder dispersion.

Control bouillon was prepared by adding the dehydrated powder (10 g) to and ferrous pyrophosphate (FePP) into boiling water (500 mL). The reconstituted bouillon was stirred to have uniform powder dispersion.

Sample tests bouillon were prepared by prepared by adding the dehydrated powder (10 g) to boiling complex solutions (500 mL) previously described. The reconstituted bouillon was stirred to have uniform powder dispersion. Samples were compared through colour measurements. Data are reported in the table below:

From this table, smallest colour variations were observed in trial 1 and 3, where the complex was formed by adding the heating step in the preparation process.