Field of the invention

The present invention relates to a process for manufacturing an encapsulated fat-soluble vitamin, to an encapsulated fat-soluble vitamin obtainable by such process and to the use of such encapsulated fat-soluble vitamin.

Background of the invention

There is an increasing demand for industrially prepared food and feed products that comprise health promoting compounds such as vitamins. In order to avoid that vitamins react too early, i.e. during storage or manufacture of the food or feed product, with other food or feed ingredients, microencapsulation of vitamins is often applied. In this way, a barrier against chemical reactions is provided and vitamin retention is improved. Moreover, vitamins are typically used in low dosages that are difficult to distribute homogeneously throughout the food or feed products. Micro-encapsulation provides an adequate dilution of the vitamins in a form that has good distribution properties. Some vitamins, such as for example vitamin D, are extremely toxic in its undiluted form and handling such undiluted vitamins would required very stringent safety measures. Handling of micro-encapsulated vitamins requires less stringent safety measures.

One of the techniques often used for encapsulation of water-soluble vitamins such as vitamin C is dispersion of the water-soluble vitamin in molten fat or wax followed by spray-cooling or spray-chilling of the dispersion. In GB 922,697 for example, coating of water-soluble vitamin with a mixture of saturated C14-C18 fatty acids having a melting point of at least 45 °C is disclosed. The coating process involves suspension of the vitamin in the molten fatty material followed by the production of solid spheroidal particles by means of spray-chilling of the suspension.

In GB 340,580 is disclosed the preparation of vitamin D, a fat-soluble vitamin, in a form that is suitable for household purposes, in particular for providing the daily dosage of vitamin D to children in an attractive and easy way. The vitamin D is dissolved in cocoa butter and subsequently processed into chocolate or cacao products.

For fat-soluble vitamins, encapsulation in a solid fat or wax phase, such as typically done for vitamin C, was never applied for the provision of a vitamin ingredient for the industrial production of functional food or feed products. Such fat encapsulation was not seen as providing a sufficient barrier in view of the solubility of the vitamins in the fatty composition. Also, because of the high sensitivity of vitamin D to oxidation, a fat coating was not seen as sufficient protection in the further processing of vitamin D, since any downstream high temperature processing step would expose the vitamin again to oxidation conditions.

Typically, fat-soluble vitamins are encapsulated by spray-drying of an emulsion of the fat-soluble vitamin, optionally dissolved in an oil phase, in a matrix material. The matrix material is optionally coated with starch or modified starch. The matrix material typically is a protein, for example gum arabic, sodium caseinate or gelatin, in combination with a carbohydrate, for example maltodextrin, sucrose or lactose.

In US 4,389,419 for example is disclosed a process for encapsulation of oil soluble vitamins in a shape-retaining water-insoluble alginate matrix. In the process of US 4,389,419, first an emulsion consisting of a continuous phase comprising an aqueous solution of an alginate and optionally a water-soluble filler such as a polysaccharide and a dispersed phase comprising the vitamin dissolved in oil is formed. The emulsion is then formed into droplets that are immersed in an alcoholic solution of multivalent cations in order to produce the shape-retaining alginate matrix enclosing the oil droplets.

In US 2003/0170324 microencapsulation of 25-hydroxy vitamin D3 is disclosed. The vitamin D3 is first dissolved in oil and the resulting oil composition is then encapsulated in an encapsulation agent selected from starches, protein, pectin, alginate, agar, maltodextrins, lignin sulfonates, cellulose derivatives, saccharides, sugars, sorbitols, or gums.

Also, relatively expensive formulation processes like spray congealing or complex coacervation are used for encapsulation of vitamin D and other fat-soluble vitamins.

Since achieving the droplet size distribution in the matrix material required for a homogenous product is relatively complex, the above-mentioned encapsulation techniques for fat-soluble vitamins are expensive.

Summary of the invention

The present invention relates to a process for manufacturing an encapsulated fat- soluble vitamin comprising: (a) preparing a homogeneous solution of a fat-soluble vitamin in a molten fatty phase; and

(b) cooling the solution to solidify the fatty phase and form the encapsulated vitamin, wherein the fatty phase has a melting point in the range of from 45 to 90 °C.

It has been found that encapsulation of fat-soluble vitamins in a fatty phase that melts at a temperature of at least 45 °C, preferably at least 55 °C, by the process according to the invention provides fat-encapsulated vitamins that can be suitably used as ingredient in industrially produced food or feed products. The fat coating thus produced appears to be sufficiently stable to protect the encapsulated vitamins against undesired chemical reactions such as oxidation during storage and further processing into food and feed products.

In a further aspect, the invention relates to an encapsulated fat-soluble vitamin obtainable by a process as defined hereinbefore.

In a final aspect, the invention relates to the use of the encapsulated fat-soluble vitamin defined hereinbefore as ingredient in animal feed.

Detailed description of the invention

In the process according to the invention, an encapsulated fat-soluble vitamin is manufactured by first preparing a homogeneous solution of a fat-soluble vitamin in a molten fatty phase (step (a)) and subsequently cooling the homogeneous solution thus prepared to solidify the fatty phase such that fat-encapsulated vitamin is formed (step (b))-

In order to form an encapsulated fat-soluble vitamin that has a coating that is sufficiently stable to protect the vitamin against undesirable chemical reactions, in particular oxidation, during storage and during further processing steps, the fatty phase used has a melting temperature of at least 45 °C, preferably at least 55 °C, more preferably at least 58 °C. In view of the instability of most fat-soluble vitamins, in particular vitamin D, a too high processing temperature in step (a) is preferably avoided. Therefore, the fatty phase has a melting temperature of at most 90 °C, preferably at most 80 °C, more preferably at most 72 °C, even more preferably at most 68 °C. A fatty phase with a melting temperature in the range of from 58 to 68 °C is particularly preferred.

Reference herein to the melting temperature is to the initial melting temperature of the fatty phase. In step (a) a fat-soluble vitamin is homogeneously solved in the molten fatty phase. Such homogenization is carried out at a temperature above the melting temperature of the fatty phase. Preferably, the homogenization is carried out at a temperature below 100 °C, more preferably at a temperature in the range of from 80 to 95 °C.

The preparation of the homogenous solution may be carried out in any suitable way known in the art. Typically, a molten fatty phase will first be provided and then the fat-soluble vitamin will be added to the molten fatty phase. Optionally, further ingredients such as anti-oxidants or anti-caking agents may be added to the molten fatty phase. The fat-soluble vitamin may be added in any suitable form, for example in crystalline form, in the form of a vitamin resin or dissolved in an oil or fat. After or during addition of the fat-soluble vitamin and the optional further ingredients, mixing is applied to form a homogeneous solution of the vitamin in the molten fatty phase.

Subsequent cooling step (b) may be any suitable cooling step known in the art. Cooling techniques that enable formation of the encapsulated vitamin in powder form are preferred. Preferably, the cooling is spray-cooling or spray-chilling. Spray-cooling and spray-chilling are techniques well-known in the art.

The fatty phase may comprise any food grade or feed grade fatty compound such as for example triglycerides, other esters of fatty acids, waxes or combination of two or more thereof. The fatty phase preferably comprises a hydrogenated animal fat or oil, a hydrogenated vegetable oil, a feed grade or food grade wax or a combination of two or more thereof. More preferably the fatty phase essentially consists of one or more hydrogenated vegetable oils such as hydrogenated palm kernel oil, palm oil, rape seed oil, soy oil, sunflower oil, safflower oil, coconut oil, peanut oil, corn oil, cotton seed oil, sesame seed oil, olive oil, linseed oil or castor seed oil or of a feed grade or food grade wax such as for example carnauba wax, bees wax or edible paraffin wax. Even more preferably the fatty phase is a hydrogenated vegetable oil or a food grade wax, still more preferably a hydrogenated vegetable oil.

The process according to the invention is suitable for encapsulation of any fat- soluble vitamin. The vitamin may thus be any fat-soluble vitamin such as vitamin AD, E or K, including any of its analogues. Preferably the vitamin is vitamin D or any of its analogues. Reference to vitamin D is to any one of vitamin Dl, D2, D3, D4 or D5. More preferably, the vitamin is vitamin D3 or any of its analogues. A particularly preferred vitamin is 25 -hydroxy vitamin D3, an analogue of vitamin D3.

The vitamin may be added to the molten fatty phase in any suitable amount. For vitamin D3, the vitamin is preferably added in such amount that a concentration in the range of from 0.1 to 0.8 million international units (IU) per gram of the resulting encapsulated vitamin is obtained, more preferably of from 0.2 to 0.6 million IU per gram. One million IU of vitamin D3 corresponds to 25 mg of vitamin D3.

Preferably an anti-oxidant is added to the fatty phase in step (a). Any suitable anti-oxidant may be used. Preferably, the anti-oxidant is selected from the group consisting of butyl hydroxyl toluene, tocopherol, and etoxyquin.

The encapsulated fat-soluble vitamin obtainable by the process according to the invention is preferably in powder form. Powder with an average particle size in the range of from 100 to 850 μιη is preferred. An advantage of an average particle size of at least 100 μιη is that oxidation stability is improved as compared to particles with a smaller diameter. In order to be able to mix the vitamin powder homogeneously with other food or feed ingredients, the average particle size is preferably at most 850 μιη, more preferably at most 750 μιη, even more preferably at most 500 μιη. An average particle size of at most 300 μιη is particularly preferred. It will be appreciated that the particle size can be controlled by adjusting the spray-chilling or spray-cooling conditions, in particular the flow rate of the solution through the spray-chilling or spray-cooling nozzle and the flow rate of the atomizing gas. Reference herein to the average particle size is to the average particle diameter.

In case the encapsulated fat-soluble vitamin manufactured is in the form of a powder, an anti-caking agent is optionally added to the powder formed in step b). Any suitable anti-caking agent may be used. Preferred anti-caking agents are silicon dioxide, tri calcium phosphate and magnesium aluminium silicate.

The encapsulated fat-soluble vitamin according to the invention is particularly suitable for use as ingredient in food products or in animal feed, in particular in animal feed. It has been found that the encapsulated vitamin can suitably be processed at a temperature in the order of 80-90 °C, a temperature commonly used in the manufacture of animal feed. Examples

The invention will be further illustrated in a non-limiting way by the following examples.

EXAMPLE 1 (according to the invention)

An amount of 480 grams of fully hydrogenated rape seed oil (ex Unimills,

Zwijndrecht, The Netherlands) was melted by heating it to a temperature of 95 °C. To the molten hydrogenated rape seed oil was added 16.7 grams of a solution of vitamin D3 resin in soy bean oil comprising 15 MlU/g vitamin D3, and 3.8 grams of butyl hydroxy toluene. The mixture was homogenized in a laboratory homogenizer at 400 bar. The thus-obtained homogeneous solution of vitamin D3 in the molten fat phase was spray-chilled by pumping it (40 rpm, approximately 30 g/min) through heated tubing (95 °C) to a two-fluid nozzle (diameter 2.0 mm) and spraying it with nitrogen gas into liquid nitrogen to form particles with a particle size ranging from 100 to 650 μιη. By varying the pumping rate of the vitamin solution and the nitrogen pressure the particle size could be adjusted.

The homogeneity and the stability of the encapsulated vitamin was determined. For determining the homogeneity, five samples of 10 grams each were taken from the entire batch and analysed with respect to vitamin D3 content. The average vitamin D3 content appeared to be 0.507 million IU per gram with a standard deviation of 0.003 million IU per gram. After storage for three months at 40 °C and a relative humidity of 75%, the vitamin D3 content of samples appeared to be at the same level as just after manufacture. This shows that no oxidation or other degradation reaction had occurred. EXAMPLE 2 (according to the invention)

The experiment of EXAMPLE 1 was repeated, but now with palm stearin (Prifex 300, ex Unimills, Zwijndrecht, The Netherlands) instead of hydrogenated rape seed oil.

As in Example 1, the homogeneity and the stability of the encapsulated vitamin was determined. The average vitamin D3 content appeared to be 0.504 million IU per gram with a standard deviation of 0.003 million IU per gram. After storage for three months at 40 °C and a relative humidity of 75%, the vitamin D3 content of samples appeared to be at the same level as just after manufacture. This shows that no oxidation or other degradation reaction had occurred.

EXAMPLE 3 (according to the invention) The experiment of EXAMPLE 1 was repeated, but now with carnauba wax (ex Paramelt, Alkmaar, The Netherlands) instead of hydrogenated rape seed oil.

After storage of the vitamin powder for three months and for six months at 40°C and 75% relative humidity, the vitamin D3 content of the samples was determined and appeared to be at the same level as just after manufacture. This shows that no oxidation or other degradation had occurred.

EXAMPLE 4 (according to the invention)

An amount of 1000 kg of fully hardened palm oil (UmFeed®131, ex Unimills, Zwijndrecht, The Netherlands) was melted and kept at 70°C (+/- 5°C). Then 183 kg of butyl hydroxy toluene (ex Merck, Darmstadt, Germany) was added to the molten phase and subsequently 750 kg of a warm solution (60°C) of 15 MlU/g vitamin D3 in soy bean oil. After homogenization, this mixture was added to 18375 kg of molten fully hardened palm oil (UmFeed®131, ex Unimills, Zwijndrecht, The Netherlands) and further homogenized at 70°C (+/- 5°C).

Subsequently the material was sprayed into a large scale spray chiller at a rate of 500 kg/h to form particles with an average particle size of 250 μιη. Samples were taken after each 500 kg of product. The average vitamin D3 content was 0.57 MlU/g for all samples with a standard deviation of 0.01 MlU/g.

Samples of the vitamin powder were stored at three different conditions: 25°C and 60% relative humidity; 30°C and 65% relative humidity; and 40°C and 75% relative humidity.

After storage of the vitamin powder samples for three months and for six months, the vitamin D3 content of the samples was determined and appeared to be at the same level as just after manufacture. This shows that no oxidation or other degradation had occurred.