CH633167A5 - Method for deacidifying a fruit or vegetable extract and deacidified extract obtained - Google Patents

Description

The present invention relates to the treatment of fruit or vegetable extracts with a view to reducing the content of acid substances, these being sometimes considered undesirable, for example for reasons of taste linked to certain consumption habits or, more prosaically, for physiological reasons. The invention relates in particular to fruit or vegetable extracts whose acidity or hyperacidity is considered to be a defect. The invention also aims to deacidify extracts which are naturally too acidic to be suitable for the preparation of drinks containing lactic proteins.

One way that comes immediately to mind to deacidify fruit or vegetable extracts is to chemically neutralize them by adding an alkaline food agent such as soda, potash, and certain carbonates and bicarbonates. But it is easy to understand that this way of doing things is not desirable when one wishes to preserve the “natural” brand image of the extracts in question. In addition, on a more technical level, a substantial increase in the saline load should be noted.

The present invention does not have these drawbacks. It relates to a process for deacidifying an extract of fruit or vegetables without the introduction of foreign products, by selective absorption using a natural material, chitosan. This process is characterized by the fact that the extract is brought into contact with chitosan in divided form and that the deacidified extract is collected after having separated it from the chitosan.

The fruit or vegetable extract can be either an extract obtained by leaching using an appropriate solvent (water, alcohol, etc.) as an extract obtained by pressing, commonly called juice. If this extract contains suspended materials, it is clarified (centrifugation for example) before contacting with chitosan, the materials thus collected can be reintroduced into the extract after deacidification. Of course, such a juice can contain alcohol, obtained for example at the end of a fermentation process (wine, cider, etc.).

Naturally, the extract must be compatible with chitosan, that is to say that it does not contain acids, in particular strong acids, in an amount such that the chitosan dissolves notably there. In this regard, lemon juice is not recommended.

Chitosan in the strict sense is a natural polyglucosamine of fungal origin, which is also found in abundance in the form of chitin (acetyl-chitosan) in the shell of crustaceans and many insects. Generally, commercial chitosan is the deacetylation product of chitin, in which usually 10 to 30% of the amino groups are still in acetylated form.

In the broad sense, which is that of the invention, the term chitosan also designates natural products, or products of natural origin, which are closely related to it and which can be defined chemically as Polysaccharides carrying free amino groups. By way of indication, mention may be made of the constituents of cell walls of gram positive bacteria, for example Bacillus subtilis.

This chitosan, which can be obtained in the form of powder or flakes, can be used as it is for deacidification, but it is generally preferred to subject it to a preliminary purification treatment. Such a treatment can in particular consist in washing the chitosan with alcohol, for example 35% aqueous isopropanol. If necessary, the chitosan can also be deodorized by vaporizing unpleasant odor residues.

The contacting of the fruit or vegetable extract and the chitosan can be carried out in various ways. One can for example percolate the extract through a column of chitosan and, in this case, the deacidified extract is recovered directly at the bottom of the column. It is also possible to suspend the chitosan in the extract and it is then necessary to provide means of separation, which can be done very simply by siphoning after decantation or by filtration.

The contact time between the chitosan and the fruit or vegetable extract, as well as various other parameters, such as the temperature at which this contact is made and the proportions of chitosan relative to the extract, depend both on the desired deacidification rate and practical methods of implementation. In general, contact times of the order of 5 to 30 min for temperatures between 10 and 80 ° C are satisfactory. It is advantageous to work with extract / chitosan proportions of between 15 and 400 ml / g.

For its part, the fruit or vegetable extract may contain, after clarification, 1 to 25% and preferably 5 to 10% by weight of soluble materials. This extract may have been previously rid of its aromas by steaming, the aromas being collected separately for later reintroduction (tomato juice for example).

It has been found that chitosan is a very selective absorbent of acidic substances and that, insofar as the starting extract was correctly clarified, the losses in solids remained always minimal. Between the untreated extract and the deacidified extract, reductions in solids of 2 to 8% can be noted, which is compatible with the amounts of acids that the extract contains before treatment.

The deacidification rate can be freely chosen according to the parameters set out above. Values between 10 and 70% can be easily reached, which corresponds, compared to the starting extract, to jumps in pH upwards of between 0.3 and 2 units, depending on the extract considered and depending how we want to use it. For example, if the deacidified extract is intended for

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be added to milk to prepare a fruity milk drink of the kind that are so popular with children, it will be advantageous to deacidify up to a pH of around 4.5 to avoid that, during storage, lactic proteins come to flocculate.

Although chitosan is a cheap material, it is preferred to recycle it once it has been used, and it has been noted that the number of recycles can reach 30 to 50 times without significant loss of activity. Of course, before reuse, it should undergo a regeneration treatment, that is to say rid of the substances it has absorbed. This can be accomplished very simply by contacting with an alkaline solution and rinsing with water to the natural pH of chitosan. The chitosan thus regenerated can be directly used for a new treatment, without it being necessary to subject it to the preliminary treatments mentioned above for fresh chitosan.

According to a first preferred embodiment of the method according to the invention, regenerated chitosan is suspended in a fruit or vegetable extract previously clarified and having a dry matter content of the order of 5 to 15%. from a previous deacidification cycle, or else fresh chitosan previously washed with aqueous isopropanol and having undergone a deodorization treatment by steam entrainment. After a period of between 10 and 30 min during which the suspension is kept constantly stirred, the solids are separated from the liquid by filtration and the deacidified extract is thus recovered. The chitosan is then resuspended in water for rinsing purposes and, after separation, the rinsing waters are added to the deacidified extract. The mixture obtained is then treated according to conventional technologies in terms of fruit and vegetable extracts. If desired, it is possible to reintroduce into the deacidified extract any solid matter from which it has been freed before contact with the chitosan, in order to obtain a final deacidified extract having a ladle or pulp in suspension.

According to a second preferred embodiment, chitosan beds are used which are arranged in columns and the fruit or vegetable extract is percolated through these columns. The deacidified extract is thus directly recovered. The chitosan used must have a fairly loose structure and avoid the chitosan in fine powder, under penalty of rapid clogging of the columns.

At the end of the operations described for one or the other embodiment, the chitosan is regenerated by alkaline treatment then rinsing with fresh water. It can then be used for a new absorption cycle.

The quality of the extracts obtained is not affected by the chitosan treatment, on the contrary. Neither the intensity nor the aromatic balance of the extracts in question are affected. On the other hand, according to the tasters who prefer extracts of weakly acidic fruits or vegetables, the treatment is clearly beneficial.

The extracts can be consumed as is, for example fruit juice. They can also be used as flavoring agents in many food preparations, especially in yogurts and milk. They lend themselves moreover all the better to this last job that they are deacidified.

Of course, these extracts can be dried by atomization or lyophilization.

The following examples illustrate the implementation of the method according to the invention. First of all, the operations for preparing and regenerating chitosan are described which, optional or simply inherent in the large-scale implementation of the process according to the invention, do not however form an integral part thereof.

Examples:

Preparation of chitosan

1 kg of commercial powdered chitosan is suspended in 331 of aqueous isopropanol at 55% (crab chitosan, Biosynth. AG, particles of 0.5 to 2 mm) and the mixture is left stirring at room temperature for 30 min. . Then centrifuged to recover, on the one hand, 31.51 of aqueous isopropanol which will be recycled and, on the other hand, the washed chitosan. If it still has some odor, it is suspended in 9.91 of 0.1N KOH and the suspension is treated by steam entrainment for 1 h. Centrifugation makes it possible to separate the KOH solution, which is recycled, from the chitosan which is washed with hot water (90 ° C.) then, after centrifugation, dried with hot air (80 ° C.).

Regeneration of chitosan io One suspends in 10 kg of a 1/1 mixture of isopropanol and KOH IN, 1 kg of used chitosan, that is to say having served as absorbent, and is kept under stirring at room temperature for 15 min. Then centrifuged to recover, on the one hand, 9 kg of the liquid phase and, on the other hand, the chitosan. This is then washed with hot water (80 to 90 ° C) until the washings are neutral, then dried at 80 ° C under vacuum.

If necessary, the regeneration treatment can be completed from the washing step, the chitosan being suspended in water, by steam entrainment for 1 h. Incidentally, a little isopropanol is thus recovered. The regenerated chitosan is dried as above.

As an indication, we compare the effect of 1 batch of fresh washed chitosan and 3 batches of regenerated chitosan suspended in natural apple juice obtained by pressing, at the rate of 4 g of chitosan 25 for 200 ml of juice. There is a remarkable homogeneity since, for the 4 batches, the pH of the extract goes from 3.44 to 5.10.

At the same time, the effect of the same batch of chitosan regeneration after regeneration, suspended in the apple juice above, is compared, again at the rate of 4 g of chitosan per 200 ml of juice. There is a remarkable consistency in the pH of the treated juice which is always around 5.10, even after 15 successive regenerations. This means that chitosan can be recycled multiple times.

Examples 1 to 15:

Fresh or regenerated chitosan is suspended in a fruit or vegetable juice, sometimes fermented, as indicated in the table below and the mixture is stirred at room temperature for 15 min. The phases are then separated by centrifugation and the liquid phase is collected, which constitutes the deacidified juice.

(See table at the end of the patent)

The juices of Examples 1 to 13 are natural juices, as they are obtained by pressing, possibly clarified by centrifugation before contact with chitosan if they contain suspended solids.

Other remarks:

J0 Examples 1,2, 4,5,6,10 to 14:

The deacidified extracts can in particular be added to milk, without the latter coagulating, to constitute a very pleasant milk drink.

5S Example 2:

Release of C02 on contact with chitosan.

Example 11:

Under the same conditions as those which appear in the table, the 60 pH of the deacidified pineapple juice is 5.30 after 30 min of contact with chitosan and 5.95 after 45 min; this extract can be added to milk, which is not possible for the starting extract which causes coagulation.

65 Example 13:

Under the same conditions as those which appear in the table, the pH of the deacidified orange juice is 4.80 after 5 min of contact with the chitosan and 5.00 after 8 min.

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Example 14:

The orange juice in this example is a concentrated orange juice with 15% dry matter.

Example 15:

The wine is white wine of poor quality, considered too acidic. After treatment, this wine is considered to be frankly improved.

Example No

Nature of juice

Extract volume (ml)

Dilution weight (g)

pH of the extracts before treatment after treatment (15 min)

1

Apple

200

4

3.44

5.10

2

Pear

200

4

3.85

5.40

3

Cassis

200

10

3.12

3.71

4

strawberry

200

8

3.38

5.22

5

carrot

200

2

4.25

5.10

6

tomato

200

4

4.13

5.20

7

elderberry

200

8

3.65

4.36

8

morello cherry

200

8

3.22

4.08

9

currant

200

8

3.13

4.00

10

blueberry

200

8

3.03

4.68

11

pineapple

100

2.5

3.60

4.80

12

grape

100

2

3.27

4.67

13

orange

100

2

3.80

5.30

14

orange

50

2

3.75

5.10

15

White wine

50

1

3.40

5.40

4

Example 16:

40 g of chitosan are placed in a column and a natural apple juice obtained by pressing and clarification is percolated through it 21. The juice which comes out at the bottom of the column is deacidified and its

5 pH is 4.85. This juice can be used to flavor milk.

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Claims (13)

633167 1. A process for deacidifying an extract of fruit or vegetables, characterized in that the extract is brought into contact with chitosan in divided form and that the deacidified extract is collected after having separated it from the chitosan . 2. Method according to claim 1, characterized in that the extract is brought into contact with the chitosan for 5 to 30 min. 2 3. Method according to claim 1, characterized in that the extract is brought into contact with the chitosan at a temperature between 10 and 80 ° C. 4. Method according to claim 1, characterized in that the extract and the chitosan are brought into contact in extract / chitosan proportions of between 15 and 400 ml / g. 5. Method according to claim 1, characterized in that the deacidification is carried out in an amount of 10 to 70%. 6. Method according to claim 1, characterized in that the deacidified fruit or vegetable extract has a pH greater than 0.3 to 2 units than the pH of the extract before contacting with chitosan. 7. Method according to claim 1, characterized in that the chitosan is suspended in the fruit or vegetable extract. 8. Method according to claim 1, characterized in that the fruit or vegetable extract is pereolated through a column packed with chitosan. 9. Method according to claim 1, characterized in that, before contacting with the fruit or vegetable extract, the chitosan is washed with 35% aqueous isopropanol. 10. Method according to claim 1, characterized in that, before being brought into contact with the fruit or vegetable extract, the chitosan is deodorized by steam entrainment of the odoriferous residues in an alkaline medium. 11. Method according to claim 1, characterized in that, after being brought into contact with the fruit or vegetable extract, the chitosan is regenerated by treatment with an alkaline medium. 12. Deacidified fruit or vegetable extract obtained by the process according to claim 1. 13. Use of the extract according to claim 12 in the preparation of milk drinks.