FIELD OF THE INVENTION

The present invention relates to a process for the preparation of a vegetable fibre material and to the vegetable fibre material thus obtained

BACKGROUND OF THE INVENTION

The processing of agricultural products is unavoidably accompanied by the generation of a waste stream. Important industries which encounter this problem are the sugar beet industry, the fruit processing industry and the starch industry. Until recently, these waste streams were discarded and therefore formed an environmental burden Nowadays, this environmental problem is being tackled by the development of methods for the recovery of useful products from these agricultural waste streams, especially from pulp The paniculate fraction of the pulp, commonly referred to as the fibres or the fibre material, is used in several applications The fibres are used in non-food applications For example, EP 680 782 discloses the conversion of dried vegetable pulp into absorbent material and a the use of such dried vegetable pulp in a method for treating animal urine and faeces.

They are also used in the feed sector. EP 0 627 887, for example, discloses a method for the conversion of potato pulp into a nutritionally valuable and stable fodder by cooking and enzymatic degradation.

It is also possible to recover useful products from these waste streams that may be used in food products for human consumption. Typically, these processes are elaborate or involve complicated techniques. See for example US 4,867,998 which discloses a 20-step process for manufacturing potato fibres from potatoes.

DISCLOSURE OF THE INVENTION

The present invention relates to a straightforward and gentle process for the preparation of a vegetable fibre material from, amongst others, the waste stream of various processing industries Production of a vegetable fibre material using the process of the invention can be economically advantageous and may alleviate the problem of

many food and food processing industries. The process of the invention comprises the steps of (i) treating a vegetable fibre-containing fraction with a water-miscible organic solvent; (n) separating off the fibre-containing fraction from the resulting mixture; and (in) drying the fibre-containing fraction. The invention also relates to a vegetable fibre material obtained by the process of the invention. This fibre can have a high water absorption capacity, be biodegradable, food-grade and neutral in taste and flavour The fibre can be used in several applications in the food and non-food industry.

The vegetable fibre is prepared by a process which comprises, (i) treating a vegetable fibre-containing fraction with a water-mi sable organic solvent; (n) separating off the vegetable fibre-containing fraction from the resulting mixture; and (in) drying the fibre-con taming fraction. This process enables the recovery of valuable vegetable fibres from waste fractions of the food and food processing industry. Examples of vegetable fibres which may be isolated using the process according to the invention include fibres from beans; beet, such as beetroot, sugar beet; Brussels sprouts, cereals, such as maize, millet, oat, rice, rye, sorghum, wheat; carrots, citrus fruits, such as orange, calamondin, citron, grape fruit, lemon, lime; onions, peas, potato and soya.

The drying process is advantageously non-denaturing and non-deforming for the fibres and the compounds it contains. Also vegetable fibres which cannot readily be prepared from wet fractions using conventional techniques without damage or loss of valuable properties, such as the storage of valuable compounds in native form and water absorption capacity, may now be obtained. This is, for example, the case with potato fibres, a waste product from the starch industry. Using the process according to the present invention, the potato fibre retains its water absorption capacity, as illustrated in one of the Examples.

In the invention, an extraction process using a water-miscible organic solvent is carried out. This has the advantage that drying may be carried out at much lower temperatures than the temperatures used in conventional drying processes.

Another advantage of using a water-miscible organic solvent is that during the process bacteria and yeast cells are killed.

Yet another advantage of the use of water-miscible organic solvent is that toxins, such as glycoalkaloids are extracted as well, yielding a product free of toxins.

The fibre-containing material which is subjected to extraction with an organic solvent may be dry or wet, but preferably a wet material is used. In a preferred embodiment of the invention, potato presspulp is used as starting material, but

vegetable fibre-containing waste streams from any food or food processing industry may be used. Examples of suitables industries include, but are not limited to the starch processing industry, the beet industry, the fruit industry, the pectin industry. The person skilled in the art will understand that the process of the invention may also be used to recover fibres from the waste stream of the feed industry, the textile industry, the pulp and paper industry, etc. In these cases, however, the fibre obtained may not be fit for human consumption. The invention is, however, not limited to waste streams. Any vegetable fibre-containing material may be used as starting material.

The fibre-containing material is first treated with a water-miscible organic solvent in a ratio of from about 1 l/kg to about 5 l/kg. Preferably, the ratio organic solvent:wet fibre is about 3 litres/kg fibre. Examples of suitable organic solvents include alcohols, such as methanol, ethanol, propanol, isopropanol, and acetone or a mixture thereof. In a preferred embodiment of the invention, acetone is used as the organic solvent. After addition of the solvent, usually a slurry is formed. This will contain the vegetable fibre, which is then separated off by any suitable means, such as centrifugation or filtration. In a preferred embodiment, the slurry is separated from the aqueous phase by filtration through a Buchner vacuum funnel. It will be understood that other filter types could be used, including a rotary filter, vacuum filter, belt filter and filter press.

Optionally, after separation, the fibres are washed with an organic solvent, preferably containing less than about 5% water. In a preferred embodiment of the invention, the same solvent used earlier for extraction is used to wash the fibre. The free solvent can then be removed, preferably under reduced pressure. In a preferred embodiment, the dry matter content of the fibres at this stage is at least 40%.

Further drying is preferably carried out in a stove or vacuum tumble drier. Suitable drying temperatures are in the range of from about 30 to about 105°C, depending on the drying means and the organic solvent used in earlier steps. Depending on the dry matter content desired, the fibre may be left to dry for a few hours. In a preferred embodiment of the invention, an aceton-treated fibre preparation is left to dry for about 16 hrs, under vacuum at 35°C.

The fibre may be used as such or it can be further formulated, e.g. into a paste, powder or liquid, depending on the purpose for which it is going to be used.

The vegetable fibre prepared can have a dry matter content of at least about 90%. It usually has neutral taste and smell and it has retained its water absorption

capacity, the value of which will depend on the vegetable starting material used. Notwithstanding its liquid absorption capacity, the fibre is not hygroscopic and will therefore remain dry during storage. The fibre prepared can be used in various food and non-food applications. The vegetable fibre of the invention can have a high water absorption capacity, be biodegradable and food-grade, and can be suitable for domestic, industrial or agricultural uses.

In this context, 'vegetable fibre' is used to indicate polymer cell wall material obtainable from plants. Plants include, fruits, vegetables, flowers and parts thereof. In a preferred embodiment, the fibre is capable of instantaneous liquid absorption and reaches at least 80% of its absorption capacity in less than 60 seconds. Preferably no heating is required for the fibre to absorb liquid. The liquid absorption capacity of the fibre is preferably at least about 10 ml/g, more preferably at least about 15 mg/l, still more preferred at least about 20 mg/l.

The vegetable fibre may be used in absorbent members alone or in combination with any absorbent or superabsorbent material which is being used, or has been proposed for use, in absorbent articles. Examples include cotton fibres, wood pulp fibres, and fibres of abaca, sisal, henequen, cantala, istle, kapok, sansevieria, broomroot, hemp, ramie, jute, rayon, cellulose acetate, alginate fibres, protein fibres, polyamide, nylon, aromatic polyamides, polyester, (poly)acrylic fibres, polyethene, polypropene fibres; and water-insoluble hydrogels, such as silica gels, polyvinyl alcohol, polyvinyl esters. In this context 'absorbent member' is used to indicate that part of an absorbent article which receives and retains liquids. This member generally contains high- absorbency materials in addition to low-absorbency materials. Examples of absorbent articles are hygienic or sanitary articles, which include nappies, sanitary napkins and pads for incontinence. The fibre allows for the production of biodegradable absorbent articles, because the vegetable fibre itself is biodegradable.

The liquid-absorbing vegetable fibre may also be used as or as part of a water source, such as a water catcher in arid regions, or on golf courses, or to supply plants with water. It may also be used for food applications such as, low-calorie chips and fibre snacks and as a basis for other low calorie food applications.

Liquids that can be absorbed incl ude all kinds of body fluids, such as blood, saliva, urine, and the like, and water or watery fluids, rain water, aqueous compositions or any other hydrophilic liquid.

Valuable high molecular -weight compounds present in the vegetable fibre are preserved. The fibre may hence function as a storage form of valuable compounds, such as proteins and vitamins. These valuable compounds may be isolated from the fibre using routine techniques. If the importance of the fibre is in its valuable compounds, it is of course also possible to use the teaching of the present invention to isolate fibres having a liquid absorption capacity lower than 10 ml/g.

The vegetable fibre may be used as low temperature gelling agent or thickener in dairy products, ice creams, confectionery, bread, cakes, pastries, jams and preserves, ready-cooked meals, instant products, meat products, sauces, salad dressings, soups, soft drinks. However, it may also be used in cosmetics, for its water holding capacity. Another application is as a destainer for the removal of stains caused by liquids on textile, such as clothes, carpets and the like.

In addition, the fibre may be used in extrusion processes, because of its moisture holding capacity. As a result, an extrusion is possible of a mash with a lower dry matter content than has been used in practice before now.

The vegetable fibre of the invention can be modified using both chemical and enzymatic methods known in the art, such as deesterification, acid treatment, base treatment, peroxide treatment, etc. In a preferred embodiment the fibre is thermally modified to increase its absorption capacity. The present invention will be illustrated by the following examples.

EXAMPLES

Example 1 Apple fibres from apple pulp

To an amount of 1 kg wet apple fibres (obtained from Gist-brocades, Seclin) 3 Liters acetone were added and the mixture was thoughly mixed for at least 30 min. The mixture was then left to stand for at least 1 hour and the free liquid was decanted. The acetone-wet fibres were filtered through a Buchner funnel (area 400 cm ² , vacuum 0.2- 0.6 bar). The filter cake obtained was washed twice with 1 litre 100% acetone. Next, it was transferred to a drying plate, which was placed in a vacuum drier for 16 hrs (0.1 bar) at 35°C to remove the rest of the acetone. As a result dry apple fibres were obtained.

Example 2 Beet fibres from beet pulp

To an amount of 1 kg wet beet fibres (obtained from Gist-brocades, Delft) 3 litres of acetone were added and the mixture was thoughly mixed for at least 30 mm The mixture was then left to stand for at least 1 hour and the free liquid was decanted The acetone-wet fibres were filtered, washed and dried as described before {Example 7) As a result dry beet fibres were obtained.

Example 3 Maize fibres from maize pulp

To an amount of 1 kg wet maize fibres (obtained from Gist-brocades, Delft) 3 litres of acetone were added and the mixture was thoughly mixed for at least 30 mm The mixture was then left to stand for at least 1 hour and the free liquid was decanted The acetone-wet fibres were filtered, washed and dried as described before (Example 7) As a result dry maize fibres were obtained

Example 4 Potato fibre from potato pulp To 1 kg wet potato fibre presspulp, a waste product from the potato-starch industry, 3 I acetone was added. This mixture was stirred until a homogeneous mixture was obtained This mixture was filtered, washed and dried as described before (Example 7) As a result dry potato fibres were obtained

The above examples illustrate how the process of the invention may successfully be used for the isolation of fibres from different vegetable sources

Comparative Example 5 Potato fibre from potato pulp using heat (conventionally dried fibre) 30 g presspulp was dried at 105°C in a stove at atmospheric pressure After 3 hrs, dry product was obtained. The yield was 7 45 g

Comparative Example 6 Absorption capacity of conventionally dried potato fibre

To 1 0 g of conventionally dried potato fibre material which was placed in a measuring cylinder, 20.0 ml distilled water was added The fibre material partly floated and only after thorough stirring the particles started to take up water The whole mixture was left standing for about 30 minutes, after which a remaining free water volume of about 15 ml was found This did not change overnight

Example 7 Absorption capacity of acetone-vacuum dried potato fibre I

To 1.0 g of acetone-vacuum dried fibre material from Example 4 20 ml distilled water was added, the material absorbed all the 20 ml of water to result in a "solid-like" gel. The sediment volume created in this way was 20 ml. No free water remained.

Example 8 Acetone-vacuum dried potato fibre II

Example 7 was repeated except that 100 ml distilled water was added. This time the free water volume was approximately 50 ml.

Comparative example 9 Absorption study The water-uptake, absorption-behaviour from acetone- vacuum dried potato fibre according to the invention was compared to various other natural commercially available materials.

The tested materials were:

Dicalite - (diatomeous earth) normally used to improve filtration behaviour. (Type: 4108, From: Dicalite Europe Nord S.A.)

Soyasol - (soya-flour) normally used in baking.

Wheat-flour - basis for bread.

(Type: "kolibri", From: Meneba NV)

Wood-flour - (pulverized wood-pulp) normally used as a filter-aid. (Type: Arbocel BE 600/10, From: ettenmayer)

Cellulose - used as chromatography material. (Type: CC31 , From: Whatman)

Sephadex - (polymer of dextran) used as chromatography material. (Type: G25, From: Pharmacia) Amylose - used as a thickener in food applications. (Type: Amylum Solubile, From: Brocacef)

Of these materials 1.0 g of each was weighed into a measuring cylinder and 20 ml distilled water was added. The water-uptake behaviour was observed and the results are presented in Table 1.

The results show that potato fibres obtained by the process of the invention using acetone extraction and vacuum drying behave completely differently than conventionally dried potato fibres. Secondly, the water absorption capacity of acetone- vacuum dried potato fibres of the invention is much better than the other natural fibrous

products tested. The potato fibre of the invention is capable of instantaneous absorption without the addition of heat.

Table 1

Acetone vacuum dried fibres vs. various other products. 20 ml of water was added to 1.0 gr of these products

Product Water uptake capacity and behaviour

Dicalite Max. absorption after less than 30 sec; remaining free water volume 16 ml.

Soyasol Initially floating; Max. absorption after approx. 5 min; remaining free water volume 14 ml.

Wheat-flour Floats and only takes up water after stirring; remaining free water volume 16 ml.

Wood-flour Floats and only takes up water after stirring; remaining free water volume 14 ml.

Cellulose Max. absorption within 1 min; remaining free water volume 15 ml.

Sephadex Max. absorption within 1 min; remaining free water volume 1 5 ml.

Amylose Max. absorption within 1 min; remaining free water volume 18 ml.

Potato fibre Max. absorption within 5 sec; remaining free water volume < of the 1 ml. invention

Example 10

Determination of water absorption capacity of fibres

Apparatus

The apparatus for determining water absorption capacity consists of a glass filter, covered with a piece of filter paper and connected to a water reservoir placed below the filter The water reservoir is connected to a pipet with a graduated scale The pipet is placed on the same height as the paper filter to avoid influences of gravity The apparatus is operated under conditions of constant temperature and pressure

Principle of measurement

On the paper filter a water meniscus is put Subsequently, the pipet is filled with water by applying a reduced pressure to one end of the pipet. Then, the water menicus is carefully removed from the filter and the sample is placed on the paper filter The water uptake of the sample is read on the pipet scale

Determination of water retention capacity

The water retention capacity under pressure was determined with a centπfugation step Water saturated matrix is put in a centrifge tube fitted with a filter in the bottom and centπfuged at 500g for 10 mm. The weight of te material is determined before and after centπfugation

Alternative solvents for drying.

Amounts of 10 gram of dried potato-fibre (Example 4) were mixed with 300 ml of distilled water To these mixtures 900 ml of respectively methanol, ethanol or 2- propanol (MERCK) was added The fibres were recovered from these mixtures by first decanting the free liquid followed by filtering, washing with the appropriate solvent and drying the fibres as described before (Example 1) Both water absorption and retention capacity were determined. The results are presented in Table 2 and show that the fibre obtained by the method of the invention has higher absorption and retention capacity than the conventionally dried fibre.

Table 2

Type of Fibre/Solvent Water Water absorption retention ml/g ml/g

Potato/Water 3.5 ± 0.5 2

Potato/Acetone 14 ± 2 6

Potato/Methanol 17 ± 2 8

Potato/Ethanol 16 ± 1.5 6

Potato/2-Propanol 16 ± 1.5 6

Table 3

Results various Modifications on Potato Fibre.

Type of modification. Water absorption Water retention ml/g ml/g

Heated (100°C) 2% Fibres 18 ± 3 7

Heated (100°C) 4% Fibres 18 ± 2 8

Heated (100°C) 6% Fibres 17 ± 2 8

Example 11 Thermal modification of the fibres. Amounts of 10 gram of dried potato-fibre (Example 4) were mixed with respectively 167, 250 or 500 ml of distilled water to obtain mixtures with respectively 6, 4 and 2% (w/v) fibres. These mixtures were left at 100°C in an oven for 4 hours and then water was added till 500 ml. The resulting heat-treated fibres were recovered by adding 3 volumes of acetone to the mixture, filtering, washing and drying the fibres as described before (Example 1). Water absorption and retention capacity were determined as described in Example 10. The results are presented in Table 3. They show that the absorption capacity of the fibre of the invention may be improved by modification.

Since the fibre may successfully be modified by thermal modification, it may also be used as an ingredient in food applications which involve heat treatment, such as pasteurisation and baking

Example 12 Water absorption in the presence of salts

Absorption experiments with potato fibre were also performed with a solution which is known in the art as synthetic urine (1 % w/v NaCI, 0 03% w/v CaCl ₂ 2H ₂ 0, 0 06% w/v MgCI ₂ 6H ₂ 0 in distilled water) It was found that the aceton-vacuum dried potato fibre's absorption capacity was not influenced by the salts This shows that there is no salt poisoning effect which is frequently seen in conventional absorbent materials