FR2485339A1 - Prodn. of syrups contg. glucose and fructose - by contacting poly:fructoside(s) with microorganisms - Google Patents

Abstract

Prodn. of syrups contg. glucose and fructose is carried out by contacting polyfructosides with microorganisms in an aq. medium. The process is esp. useful for producing fructose-rich syrups from plant extracts, e.g. extracts of Jerusalem artichokes, dahlia tubers or chicory roots. The microorganism is pref. a non-fermenting yeast contg. a beta-fructosidase, e.g. Pichia polymorpha, Debaryomyces cantarelli or D.phafii (CBS 186, 4349 and 4346 respectively). The process is pref. carried out by (a) contacting the comminuted plant material with water in a battery of diffusers; (b) treating the juice with lime and CO2; (c) adjusting the pH to 3-5; (d) percolating the juice at 20-40 deg.C through a hydrolysis reactor contg. the microorganisms immobilised on a support (esp. wood chips and/or PVC turnings); (e) demineralising the hydrolysate with cation- and anion-exchange resins; (f) concentrating the hydrolysate to 700 g/l; and (g) decolourising the concentrate with animal charcoal.

Description

The present invention relates to a process for preparing syrups rich in fructose, by hydrolysis of dep-polyfructosides of vegetable origin.

Many plants contain carbohydrate reserves made of polyfructos Glucose (Fructose) n - symbolized G (F) n - whose high molecular weight specimens form inulin (degrees of polymerization from 30 to 35).

In cert, -rines plants of the family of compounds, these carbohydrates constitute 16 to 20% of the fresh matter of the roots or tubers (dahlia, chicory, Jerusalem artichoke, etc ...) and are a potential source of fructose.

Under the name of "isomerose" syrups containing fructose and glucose are currently marketed.

They are prepared from starch, by hydrolysis and isomerization. Their fructose content remains below 50% and their cost price is relatively high.

It has also been proposed to hot extract the polyfructosans of vegetable origin, then to hydrolyze them in an acid medium and at high temperature. The acid hydrolysis leads to the formation of colored products which make the purification steps difficult due in particular to the increase in the content of the medium in mineral salts.

The process for obtaining glucose and fructose syrups according to the present invention is based on a bioconversion process. It is characterized in that it consists in bringing polyfructosides in aqueous medium into contact with microorganisms.

According to one form of the invention, the polyfructosides are extracted from plant organs (tubers of Jerusalem artichoke, dahlia or chicory roots).

According to a preferred form of the invention, the microorganisms used are yeasts, possibly devoid of fermentation metabolism and possessing a very active parietal inulinase (or an β-fructosidase activated on polyfructosides and inulin). Under very careful aeration conditions, the yeast is unable to ferment and cannot destroy the fermentable sugars - glucose and fructose - which it forms by hydrolysis. The oxygen dissolved in the juice is generally sufficient to allow the activity to be maintained and, possibly, to multiply the yeast.

Under these conditions, when the product to be treated contains 150 g of carbohydrates per liter, the consumption of sugar by the yeast is negligible: of the order of dosing errors and in any case, less than 1% of the carbohydrates present.

According to a particular form of the invention, the microorganisms are retained in a fixed bed reactor, by adsorption on a support consisting of a mixture of wood chips and poly (vinyl chloride) turnings. It is obvious that any system of adsorption, fixation or immobilization of microorganisms compatible with the production of foodstuffs can be used.

According to another form of the invention, the polyfructosides are hydrolyzed in a conventional fermenter, continuously, with stirring, without aeration, in order to avoid the metabolization of sugars by an oxidative route. The microorganisms entrained in the extracted liquid are recycled in the fermenter.

The industrial implementation of the method according to the invention requires the following steps
1) placing the vegetable organ in pods and milking
lying in a broadcast battery.

 2) treatment of the juice by calco-carbonic defecation.

3) adjusting the pH and temperature of the juice
to the desired values.

 4) passage of the juice through the hydrolysis reactor.

5) demineralization of the hydrolyzed juice by passage
on a cationic resin and a resin
anionic.

6) concentration of demineralized juice up to
700 gl
7) discoloration of the concentrated juice.

It is essential that the above steps be carried out without significant downtime in order to avoid microbial contamination in particular.

If yeast constitutes a particularly favorable material for the hydrolysis step, it is not excluded to use filamentous fungi (molds) with high inulinase activity. However, in this case, it must be ensured that the fungus does not excrete mycotoxin.

Likewise, the use of bacteria is conceivable only with germs which do not give fermentation in the absence of air and which have a low consumption of sugar without the formation of undesirable products under conditions of controlled ventilation.

On the other hand, the mutants exhibiting a depressed biosynthesis of inulinase are of great interest.

Obtaining these mutants is easy. Their use makes it possible to multiply by a factor of at least 5 the rate of hydrolysis.

The step called "calcocarbon defecation" eliminates the organic impurities "non-sugar" and ent ent not loss of carbohydrates if it is carried out before hydrolysis.

The hydrolysis step should preferably be carried out at a pH between 3 and 5 and at a temperature between 20 and 400C.

Without being limiting, the examples below will better understand the invention.

Example 1
Chicory roots put in pods are placed in a diffusion battery, in water at 700 C. A solution containing 150 g of carbohydrates is obtained. (glucose, fructose, sucrose and -polyfructosides G- (F) n of increasing degrees of polymerization).

The juice is treated by calc-carbonic defecation adding CaO (18 g.l 1) up to pH 11.5, first carbonation up to pH 10.6 then second carbonation up to pH 9.

The juice then has a carbohydrate content close to 91.5% (by weight of dry matter).

In addition, PICHIA POLYMORPHA cells
KLOCKER (CBS 186) - grown on the previous juice - are adsorbed on a mixture (80 - 20) of wood chips - poly (vinyl chloride) turnings placed in a reactor. About 4.10 cells are retained per liter of reactor.

The juice is treated by calc-carbonic defecation, the pH of which is adjusted to 3.5 by the addition of sulfuric acid, which percolates continuously, from bottom to top, into the reactor.

The temperature is maintained at 350. The flow rate of the juice is regulated in such a way that the liquid contained in the reactor is renewed in 1 h 30 min.

The hydrolyzed juice contains a glucose fructose mixture (25-75) and about 106 cells.l ~ 1 which are eliminated by centrifugation.

The product obtained is demineralized by passage through a cationic resin (AMBERLITE IR 120) then over an anionic resin (AMBERLITE IRA 68).

"Non-sugar" materials only represent 1% of the total dry matter.

The purified juice is concentrated under vacuum to a concentration of 700 g.l -1 and it is discolored by treatment with animal charcoal.

Example 2
The procedure is the same as in Example 1, but replacing the chicory roots with Jerusalem artichoke tubers.

After the diffusion stage, the juice obtained has the composition
following sition: glucose, fructose, sucrose,, -polyfructosides G (F) n of degrees of polymerization
croissants. Its sugar content is 155 gl 1
The total hydrolysis of the juice is obtained for a time of renewal of the liquid in the reactor, of approximately 1h 40mn.

Purified juice contains glucose and fructose
(23-77) and 1.5% mineral matter.

Example 3
A diffusion juice of chicory roots prepared is treated as indicated in Example 1.

The strain used in the reactor is DEBAROMYCES
PHAFII CAPRIOTTI (CBS 4346).

We adsorbed on the same support as in Example 1
1011 cells. L 1 of reactor.

The hydrolysis, carried out at pH 3.5 and at 350 ° C., is complete for a time of renewal of the liquid in the reactor equal to 3 h.

The final product obtained contains glucose and fructose (25-75) and 1% mineral matter.

Example 4
We proceed in the same way as in Example 1 on
a diffusion juice of chicory roots.

The strain used is DEBAROMYCES CANTARELLI CAPRIOTTI (C.B.S. 4349).

2.1011 cells.l are fixed in the reactor.
The hydrolysis carried out at PH 3.5 and 350C is total for a time of renewal of the liquid of 3 h 45 min.

The final product obtained has the same composition as the product of Example 1.

The strains whose references are given in the examples can be obtained at Centraalbureau voor
Chimmelcultures - Julianalaan 67 - DELFT - Holland.

Claims (17)

1. Method for obtaining syrups containing glucose  and fructose characterized in that it consists of  contact polyfructosides in the middle  aqueous and microorganisms. 2. Method according to claim 1, characterized in  what polyfructosides are extracted from organs  plants. 3. Method according to claim 2, characterized in  what the plant organs are tubers of  Jerusalem artichoke. 4. Method according to claim 2, characterized in  what the plant organs are tubers of  dahlia. 5. Method according to claim 2, characterized in  what plant organs are roots of  chicory. 6. Method according to any one of the claims  above, characterized in that the microorganis  my contain a, '3-fructosidase parietale capa  ble to hydrolyze the 3-polyfructosides present  in the aqueous medium. 7. Method according to claim 1, characterized in  what microorganisms are unfit yeasts  at fermentation. 8. Method according to claim 7, characterized in  what yeast is a PICHIA POLYMORPH strain  KLOCKER.  9. Method according to claim 7, characterized in  what yeast is a DEBAROMYCES CANTA strain  RELLI CAPRIOTTI. 10. Method according to claim 7, characterized in  what yeast is a DABAROMYCES PHAFII strain  CAPRIOTTI. 11. Method according to claim 7, characterized in  what yeast is a depressed mutant for the  inulase biosynthesis. 12. Method according to claim 1, characterized in  what microorganisms are adsorbed on a  support. 13. Method according to claim 12, characterized in  what the support is made of wood chips  and poly (vinyl chloride) turnings (80-20). 14. Method according to any one of the claims  previous characterized in that the reac medium  tional is maintained at a pH between 3 and 5  and at a temperature between 20 C and 40 "C. 15. Method according to any one of the claims  previous characterized in that  1) the plant organs are put in pods  and treated in a battery of diffusers  with water at 70 C.  2) the juice obtained is treated by defecation cal cocarboni que.  temperature is maintained between 20 "C and 40" C.  3) the pH of the juice is adjusted between 3 and 5 and its  support.  holding one of the microorganisms adsorbed on a  4) the juice percolates in a hydrolysis reactor con  than.  a cationic resin and on an anioni resin  5) the juice obtained is demineralized by passing over  animal black.  7) the concentrated juice is discolored by passing over  700 g.l  6) the demineralized juice is concentrated until 16. Method according to claim 15, characterized in  what the hydrolysis step is done under act  tation and without ventilation. 17. Method according to claims 15 and 16, charac  confirms that the hydrolyzed juice is centrifuged  before being demineralized.