EP2405769A1

EP2405769A1 - Fractionation of natural raw materials and separation of nutritive substances therefrom

Info

Publication number: EP2405769A1
Application number: EP10806089A
Authority: EP
Inventors: Anu Kaukovirta-Norja; Mirja Mokkila; Riitta PUUPPONEN-PIMIÄ; Pekka Lehtinen; Pirkko Forssell; Olavi Myllymäki
Original assignee: Valtion Teknillinen Tutkimuskeskus
Current assignee: Valtion Teknillinen Tutkimuskeskus
Priority date: 2009-03-11
Filing date: 2010-03-11
Publication date: 2012-01-18
Also published as: FI20095249A0; FI122664B; WO2011015706A1; FI20095249A

Abstract

The present invention relates to a method of fractioning natural raw materials and separating nutritive substances from the formed fractions, in which method the raw material is dried at a temperature of -40-50 °C and ground lightly so that the seeds of the raw material separate from the fruit flesh and skin portion without breaking, after which the seeds are separated from the dried and ground raw material and a second light grinding is carried out on the formed seedless fruit flesh and skin fraction so that the nutritive substances therein are not damaged, whereby a powder is provided, which is screened or classified, whereby the nutrient-rich skin powder fraction can be separated from the other fractions. The invention also relates to the skin fraction formed from the berry raw material.

Description

FRACTIONATION OF NATURAL RAW MATERIALS AND SEPARATION OF NUTRITIVE SUBSTANCES THEREFROM

The invention relates to a method of fractioning natural raw materials by dry methods into components that have different phenolic compositions. The invention further relates to a skin fraction that is formed by means of the method.

Berry raw material is underutilized in Finland. Plenty of berries are found in Finland and they are nutritive products that contain, among others, phenolic compounds, carbohydrates and nutritive fibre. However, enrichment of their most valuable components and their separation into medicine-like preparations or products in an economically sensible manner has not been started in Finland. Instead, an expensive adsorption process is used to prepare, from the berry raw material exported from Finland, phenolic concentrates, the phenolic compounds of which that function as natural antioxidants generally include flavonoids that are found abundantly in berries. The phenol content in these concentrates is 25-30 -fold compared with the phenol content of the starting material.

In known enrichment methods, the phenolic compounds in an acidic aqueous solution are adsorbed into a resin in industrial adsorption columns. The sugars that are not adsorbed into the resin are washed from the columns, whereby only a fraction mainly containing phenolic compounds remains attached to the surface of the resin. The phenolic compounds are detached from the resin by eluting with an aqueous ethanol solution. The ethanol is evaporated and recovered. The phenolic compounds remain in the aqueous solution of the base product, which is most typically dried into a powder using a spray drier. The operations of the method that consume the highest amount of energy include the

distillation and evaporation of ethanol as well as the drying stages. Said adsorption operations are used to prepare from the berries standardized phenol extracts, the phenol content of which normally is 25% by weight. The products are sold as medicine-like preparations.

Phenolic compounds are commonly found in berries and they contribute to the formation of the colours of the berries. For example, the colour of blueberry and highbush blueberry is mainly the result of anthocyanins, which are phenolic compounds that are found abundantly in blueberries. Raspberry, cloudberry as well as Arctic bramble,

correspondingly, contain plenty of ellagitannin and cranberry and lingonberry, in turn, contain plenty of flavonols. In addition to these berries that are abundantly found, e.g., in Finland, phenolic compounds can be enriched from grapes, particularly from dark grapes.

Blueberry contains interesting anthocyanins, mainly as delphinidins, the content of which is 0.3-0.8% of the fresh weight, depending on the growth conditions. At its simplest, such products are made by drying and grinding the berries or by concentrating and drying berry juice, whereby the achieved concentrations, at their best, are 5-10% by weight of the dry matter (WO 03084559, DE1767614).

Thus, there exists a need for a novel method, by which useful ingredients can be extracted from various berries in a simple and energy-effective manner. Brief description of the invention

An object of the present invention is to utilize gentle and simple method stages for the enrichment of nutritive substances or medicine-like substances or substances suitable as the same into specific fractions of natural raw materials, from which they can be separated.

In particular, an object of the present invention is to provide a method, by which the nutritive substances or medicine-like substances can be separated and enriched from a berry raw material by utilizing energy-effective method stages. Thus, the present invention relates to a method of fractionating natural raw materials, such as berries, into fractions and separating nutrients from the fractions formed, in which method the raw material is dried and ground.

More precisely, the method according to the invention is characterized by that, which is stated in the characterizing part of Claim 1.

Correspondingly, the skin fraction of berries that is formed by means of the method according to the invention is characterized by that, which is stated in the characterizing part of Claim 12, and the use of the method according to the invention is characterized by that, which is stated in Claim 15.

The invention enables a more economic utilization of berries, as a purpose of the invention is to separate the structural portions of berries or other natural raw materials into different components by dry methods. The raw material is preferably dried whole berries or, more preferably, a pressed cake that remains after juice is pressed from the berries. It is essential to carry out the pressing process and the following drying process so that the bioactive components, such as anthocyanins, are not destroyed.

By means of the invention, a fraction can be separated from the berry, the phenol

(anthocyanin) content of which per dry matter is multiple compared with the anthocyanin content of unprocessed berry. For example, according to the analysis of Latti et al., the highest anthocyanin content in freeze-dried Finnish blueberry in 2007 was 3.8% by weight. In the method, juice is pressed from the berry, after which the phenol (anthocyanin) is enriched from the dried pressed cake. Generally, the portion of pressed cake of the starting raw material is 10-20% by weight, depending on the effectiveness of the pressing process. Using the method according to the invention, a fraction can be obtained from the pressed cake, wherein the phenol (anthocyanin) content is at least 8% by weight, preferably 15- 20% by weight.

Detailed description of the invention

The present invention relates to a method of fractionating natural raw materials, such as berries, and separating nutrients from the fractions formed, in which method the raw material is dried and ground. Said drying is preferably carried out at a temperature of -40- 50⁰C, depending on the drying method and, correspondingly, said grinding is carried out lightly, so that the seeds of the berry separate from the fruit flesh and skin portion without breaking. If the moisture content in the drying is left slightly higher, i.e. 10-15%, the skin portion can be separated as large-size pieces by kneader grinding. After drying and grinding, the seeds are separated from the raw material and a second light grinding is carried out on the formed seedless fruit flesh and skin fraction, so that the nutrients therein are not damaged, whereby a fine powder is formed, which is screened or classified, whereby the nutrient-rich skin powder fraction can be separated from the other fractions. "Light grinding" refers to the fact that grinding is carried out gently using a mill that has a low grinding energy. These include, for example, mills that have a rotating rotor and a stationary stator, the distance of which can be adjusted. This preferably refers to a disc mill or the like.

The invention also relates to a skin fraction, which is formed from the berry raw material and which contains bioactive components, such as natural antioxidants, as much as 20% by weight, preferably 10-17% by weight, most preferably 12-16.5% by weight.

Berries, such as blueberry, highbush blueberry, lingonberry, black currant, raspberry, cloudberry, cranberry or Arctic bramble or a mixture thereof, are preferably used as the raw material of the invention. Dark grape is also suitable for use as the raw material of the invention.

Most generally, the pressed cake of blueberry, lingonberry or black currant or that of another equivalent berry is used as the raw material of the method according to the invention. Being the by-product of juice production, the pressed cake is an economically good starting point. Until now, the pressed cake has mainly been a waste product. Seeds, which have low phenol contents, have been separated from a part of the commercial pressed cakes. According to the present invention, however, a phenol-bearing seed fraction can also be separated from the seeds, when so desired, the fraction also containing cutin suitable for use as a nutrient. According to a preferred embodiment of the invention, the yield of the juice is increased by using enzymes. The cake thus formed contains fewer sugars with a low glass transition than whole berries do, the small amount facilitating drying and the subsequent grinding and classification operations. The sugar content that prevents a harmful separation can be reduced by washing the pressed cake with water or the aqueous solution of maltodextrin, the maltodextrin increasing the glass transition and facilitating the grinding and

classification operations. The pressed cake thus obtained is dried at a low temperature, where the sugar component is mainly in a glasslike form instead of an amorphous form. According to a second preferred embodiment of the invention, the berry raw material, which can be dried whole berry or, preferably, the pressed cake obtained as a by-product of juice pressing, is dried in a freeze-drier at a temperature of -40 ⁰C-O °C, or preferably by convective drying at a temperature of about 40 ⁰C. In addition to the freeze-drier, a suitable drier can be a fluidized-bed drier or a continuous drier or the like.

In dry methods, the raw material is most suitably the enzyme-pressed cake of blueberry or black currant or another berry. The cake is dried in a controlled manner by a pressing and drying process, which enables the preservation of the functionally valuable components of the berry material, such as the phenolic compounds, and which provides a dried product, from which the different structural components, seeds, skin portion and fruit flesh, i.e. pulp, of the berry can be separated on the basis of the grinding process and the subsequent classifications. The highest phenol content is in the skin portion, which should be separated in as pure a form as possible from the other components (Examples 1 and 2).

The berry raw material that has been dried at a low temperature is suitably ground by a kneader grinder, by which the seeds of the berry are detached from the dry fruit flesh and skin portion without breaking the seeds. A suitable grinder is, e.g., the falling number mill, i.e. the KT mill (Koneteollisuus Oy, Helsinki, 0.15 kW, 2800 rpm), which has a rotating rotor and a stationary stator. The distance between the rotor and the stator, the clearance, can be adjusted. The mill provides a kneading and slightly cutting and striking effect, wherein the grinding energy is, however, not sufficient to break the seeds in the structures of the berry, but they are detached from the matrix, drifting unbroken along with the skin and fruit flesh fraction. A disc mill or an impact mill with a guided impact is preferably used, whereby a gentler grinding process is achieved. A grinder like the disc mill is most preferably used, its kneading way of grinding being the gentlest for the raw material.

The seeds are separated from the berry matrix broken using the mill, separately from the fruit flesh and the skin powder. Advantageous ways of separating the seeds from the rest of the berry matrix are air classification and screening.

The seedless fruit flesh and skin fraction thus obtained is further ground finer by a suitable mill, which is preferably a pin crusher. Due to the different beatabilities of the

physiological portions of the berry, a specific particle size distribution is obtained after the grinding, being preferably 0.050-0.75 mm, most suitably 0.100-0.350 mm. The powder is classified according to the differences in size either by screening or preferably by air classification. Suitable classifiers include, among others, a so-called channel classifier or zigzag classifier. Phenols are enriched into the skin fraction, where there are more of them than in the fruit flesh. When the particle size decreases into the said size category, the skin fraction (or skin portion) can be better separated from the fruit flesh fraction.

The skin portion, which in grinding remains in larger pieces, can be separated relatively pure from the fruit flesh portion and, in addition to the phenolic compounds, contains cutin, which is a good fibre addition and, being fine-grained, is also easy to productisize. When the juice yield is increased by means of enzymes, the portion of pressed cake is decreased, as part of the cell walls have broken and released more juice. The pressed cake mainly contains seeds, skin portion and the fruit portion attached thereto. The skin portion, to which phenolic compounds are attached, can be separated from the seeds into a fibrous fraction, which preferably contains cutin in addition to the phenolic compounds.

The present invention can be utilized, among others, in the preparation of extracts, into which phenolic compounds, such as anthocyanin, ellagitannin or flavonols or a mixture thereof have been enriched. The contents of these compounds in the extracts may be as high as 25% by weight, preferably 10-25% by weight, most preferably 15-25% by weight. Optionally, the extracts also contain plenty of fibres and other fibre-like compounds, such as cutin, preferably in a content, which is as high as 25% by weight, more preferably 10- 20% by weight, most preferably about 15% by weight. Examples

Example 1 - fractionation of raw material

Blueberries were freeze-dried, whereby in drying, the internal fruit flesh and the seeds of the blueberry were packed into a fraction that was partially separate from the skin, the skin being easy to separate from the fraction. The skin portion was separated in pure form from the fruit flesh and seeds by grinding lightly using a falling number mill and by separating the skin portion separately using an air flow, which on a table conveyed the skin portion apart from the seeds and the fruit flesh portion. The obtained anthocyanin (AC) content of the skin portion was 19.1 % by weight. Thus, the largest part of the anthocyanins of blueberry is included in the skin portion and is well preserved during drying that is carried out at a low temperature.

Example 2 - fractionation of raw material

Freeze-dried blueberries were ground by a falling number mill (KT mill) with a setting of clearance of 8. The skin of the blueberry was separated from a screen mesh of 0.750 mm pneumatically using an air flow. The anthocyanin content of the fraction was 12.6%.

Table 1. Anthocyanin contents of blueberry fractions ground using a falling number mill

When the portion of seeds is high, the anthocyanin content is, thus, low. If remained unbroken in the grinding process, the seeds can effectively be separated by screening with a screen of 355-400 μm. In a very fine-grained powder, the anthocyanin content also decreases when the pulp fraction increases.

Example 3 - use of an enzyme-assisted pressed cake, fractionation of the raw material and separation of the skin portion

A frozen industrial pressed cake, the pressing process of which employed commercial Pectinex enzyme preparations to ensure the juice yield, was dried in a convection oven at 40 °C. For grinding the dried cake, a falling number mill (KT mill), a Frisch laboratory mill with a 1 mm screen and a Hosokawa-Alpinen 100 UPZ pin crusher at 17000 rpm were used. The fractions that penetrated the less than 1 mm screen were screened by the Buhler nest of screens. The fractions obtained by the different mills are shown in Table 1. Table 2. Distribution of fractions obtained by different mills

After gentle grinding using the falling number mill, a powder was obtained, which permeated less than 250 μm, containing 16.1% by weight of anthocyanins. The less than 250 μm fraction that contained no seeds was ground using the Frisch mill, which was provided with a 0.14 mm screen. Efforts were made to screen this fine fraction by an air jet screen. Nothing went through a 45 μm screen. The screens of 71 μm and 100 μm were penetrated by a small portion of powder, which was collected from the low-pressure chamber of the screen. The fraction that was ground using the pin crusher was of the smallest size. The fine fraction of that was classified for an analysis using the British Rema Mini Split classifier at settings of 3500 rpm/220 m³/h. The analysis results of the fractions are shown in Table 3.

Table 3. Analysis results of ground and screened fractions

As shown in the table, in the fine grinding of the fraction below 250 μm, only the air classification could separate a fraction, wherein the anthocyanin content, 13.8%, was lower than that of the starting material, 16.1%. As both the skin and the fruit flesh were ground into a fairly homogeneous powder, the differences obtained by screening were smaller. The results indicate that anthocyanin concentrates can be mechanically separated from blueberry, which has been correctly treated and in which no thermal damages occur during the process.

Example 4 - the use of a pressed cake obtained without the enzyme treatment, fractionation of the raw material and separation of the skin portion

A dried pressed cake of blueberry from a commercial jam preparation process, comprising seeds and the skin and pulp portion, was dried at about 40 °C and ground by a falling number mill (KT mill). The powder was screened using metal screens, whereby the fractions and anthocyanin contents shown in Table 4 were obtained.

Table 4. Analysis results of fractions of different size categories

The seed fraction mainly remained on the 0.475 mm screen and the finer anthocyanin concentrates could be separated therefrom.

Example 5 - enzyme-assisted formation of pressed cake, fractionation of the raw material and separation of the seeds

Blueberry was pureed. The crushed blueberry was treated with Pectinex Smash XXL L enzymes. The enzyme was added: Pectinex Smash 10 nkat/g, i.e. 0.29 ml / 1 kg of puree (active 34900 nkat/ml) and Alcalase 2.0T, and the blueberry puree was treated with enzymes for 2 hours at 45 ⁰C. The juice was pressed by a Hafico High Pressure Tincture Press H P5 presser, whereby the amount of cake obtained was 12-14% by weight of the starting material and the dry matter of the cake was as much as 40% by weight. The cake was washed with water and re-pressed. The pressed cake was dried by an Aeromatic fluidized-bed drier with an air flow at 36 ⁰C to a dry matter of 93%. The dried cake was ground using a falling number mill (KT mill) with a clearance (setting of 5), wherein the seeds were not crushed. The seeds were separated using a British Rema air classifier. The portion of coarse fraction, i.e. the seeds, remained high, i.e. about 81- 88%, and the coarse fraction still contained cell walls. The portion of fine fraction was 12.2% by weight and its anthocyanin content was 7.7 % by weight.

Accordingly, the coarse fraction of the air classification was screened using metal sieves, whereby all seeds remained on the 0.475 mm screen, where the seeds included some skin matter and the anthocyanins were enriched as particles smaller than the size of the seed (Table 5).

Table 5. Analysis results of the fractions of different size categories

The cell wall and some skin fraction were separated from the seed fraction that remained on the screens of over 0.475, which fraction was ground using a falling number mill (KT mill) and screened using a 0.250 mm screen. The anthocyanin content of the fraction remaining on the screen was 9.1% by weight. In other words, some skin portion remained with the seed fraction, from which it can be further separated using screening or air classification after such grinding of the skin fraction, which does not break the seeds.

Example 6 - fractionation of raw material and separation and analysis of different fractions

The blueberry fraction, which had been ground using a falling number mill (KT mill) and which had permeated the 0.250 mm screen, was subjected to classification by a British

Rema classifier, at 3500 rpm and with an amount of air of 220 m³/h, to classify the fine and coarse fractions (see Table 6). Table 6. Analysis results of the fine fraction and the coarse fraction

Anthocyanin is mainly enriched into the coarse fraction that contains skin fraction and, in a lesser amount, into the fine fraction that contains pulp of the seed.

Example 7 - drying and fractionation of raw material as well as separation and analysis of the different fractions

Blueberry that was obtained from a commercial process was dried at 40 °C. This dried blueberry, the anthocyanin content of which had decreased to below 0.2% by weight, was ground using a KT mill at a setting of clearance of 6 and screened using a 0.8 mm screen. The fraction that permeated the screen was ground using the falling number mill (KT mill) at a setting of clearance of 4 and air-classified using a British Rema classifier at 2500 rpm/220 m³/h. The seedless fine fraction was screened, whereby the fractions described in Table 7 were obtained, wherein the anthocyanin content was over 10-fold compared with the starting material.

Table 7. Anthocyanin contents of the fine fraction of blueberry that was ground using the falling number mill (KT mill) and air-classified thereafter

Claims

CLAIMS:

1. A method for fractioning natural raw materials and separating nutritive substances from the formed fractions, in which method the raw material is dried and ground,

characterized in that

- the drying is carried out at a temperature of -40-50 ⁰C;

- the grinding is carried out lightly so that the seeds of the raw material separate from the fruit flesh and skin portion without breaking; and

- the seeds are separated from the dried and ground raw material and a second light grinding is carried out for the formed seedless fruit flesh and skin fraction so that the nutritive substances therein are not damaged, whereby a powder is formed, which is screened or classified, whereby a nutrient-rich skin powder fraction can be separated from the other fractions.

2. The method according to Claim 1, wherein the natural raw material originates from berries, preferably it is dried whole berry or the pressed cake obtained as a by-product when pressing juice from the whole berries, preferably the pressed cake.

3. The method according to Claim 2, wherein the whole berry is blueberry, highbush blueberry, lingonberry, black currant, raspberry, cloudberry, cranberry or Arctic bramble or a mixture thereof.

4. The method according to Claim 2 or 3, wherein the pressed cake used as the berry raw material is produced by enzyme-assisted juice pressing, wherein enzymes are added to the whole berries in an amount sufficient to change the sugars in the berry to such having a low glass transition, whereby the juice yield of the pressing increases to 80-90% by weight and the formed pressed cake becomes easier to classify.

5. The method according to Claim 1 or 2, wherein the drying is carried out in a freeze- drier at a temperature of -40 °C-0 ⁰C.

6. The method according to Claim 1 or 2, wherein the drying is carried out by convection drying, preferably using a fluidized-bed drier or a continuous drier at a temperature of about 40 ⁰C.

7. The method according to any of the preceding claims, wherein the grinding of the raw material is carried out using a kneader grinder, which has a rotating rotor and a stationary stator, by means of which the seeds are detached from the skin and fruit flesh of the raw material without breaking.

8. The method according to Claim 7, wherein the seeds that have been detached from the skin and fruit flesh are separated using air classification or screening.

9. The method according to any of the preceding claims, wherein the seedless fruit flesh and skin fraction is subjected to a second grinding, preferably using a pin crusher, whereby a particle size distribution is obtained, which is preferably 0.050-0.75 mm, after which the formed powder is classified according to size differences either by screening or by air classification.

10. The method according to any of the preceding claims, wherein nutritive substances are separated from the screened or air-classified skin powder fraction, the nutritive substances including bioactive components, such as phenols, preferably anthocyanin, ellagitannin or flavonol or a mixture thereof, and preferably also cutin.

11. The method according to any of the preceding claims, wherein the content of the nutritive substances, which are to be separated, in the formed skin fraction is up to 20% by weight, preferably 10-17% by weight, most suitably 12-16.5% by weight.

12. A skin fraction formed from a berry raw material by the method according to any of Claims 1-11, characterized in including nutritive substances, which include up to 20% by weight of bioactive components.

13. The skin fraction according to Claim 12, wherein the bioactive components are phenols, preferably anthocyanin, ellagitannin or flavonol or a mixture thereof, and cutin is possibly also included.

14. The skin fraction according to Claim 12 or 13, which is produced by drying berry raw material at a temperature of -40-50 °C, by grinding the dried raw material so that the seeds of the berry are separated from the fruit flesh and skin portion without breaking, by separating the seeds from the dried and ground raw material and by carrying out a second grinding for the formed seedless fruit flesh and skin fraction, whereby a fine powder is formed, which is screened or classified to separate the skin fraction from the fruit flesh fraction.

15. The use of the method according to any of Claims 1-11 to separate nutrient-rich fractions from the berry raw material.