Process for the production of food fibres from carrots and fibres contained by this process.

0001The present invention relates to methods of preparing dietary fiber from carrots and to dietary fiber obtained by these methods.

0002The insoluble polysaccharide fraction of carrots is a raw material of choice for the manufacture of dietary fiber, due to its high content of pectins and hemicelluloses.

0003Up to now, the procedures allowing to isolate an insoluble fraction of the carrot aimed at producing a carrot juice of good nutritional quality (mineral content, carotene, sugars). There are also several methods of making juice according to the mode of preparation of the crushed carrot before pressing: size of the crushed particles, adjustment of the pH, type of blanching, use of enzymes (These AA Munsch, December 1980, University of Laval, Canada).

0004All these processes have been optimized in order to produce a carrot juice of good nutritional quality with a satisfactory yield. The insoluble fractions of pressing marc (hemicellulose, cellulose and possibly pectins) are partially sugar-free and have always been considered as by-products.

0005The invention relates to a process for the preparation of light-colored, odorless dietary fibers, with no carrot aftertaste, and with high water retention power, involving only water treatments, excluding any treatment with solvents or chemical bleaching agents which makes it possible to considerably reduce the volume of water used, since a fraction of the water from the juices obtained by pressing can be recycled thanks to a successive separation of the colored insoluble fraction, of the soluble fraction, then of the water solubles.

0006The subject of the invention is a process for the production of dietary fiber from carrots, characterized in that it consists:<ul id="ul0001" list-style="dash"><li>pressing carrots to separate a sugar-rich juice from a marc and resuspending the latter in an aqueous solution by repeating these pressing and suspending operations, until the sugar content by weight of the marc either less than 20%,</li><li>passing a current of air or water vapor through at least one of the marcs in order to obtain a flavorless and discolored marc and a current of air or vapor charged with aromas which are evacuates, and</li><li>to dry the flavorless and discolored marc from the last pressing.</li></ul>

0007Preferably, the method consists:<ul id="ul0002" list-style="dash"><li>to use the water from the juice of the first pressing and / or the second pressing, after having successively separated the coarse insoluble substances (greater than 500 μm) by sieving or by decantation, the fine insoluble substances (carotene concentrate) by microfiltration and sugars by evaporation or other reverse osmosis, as an aqueous solution of resuspension of marc in a resuspension operation downstream of this first and / or second pressing.</li><li>returning a juice from a pressing operation, as an aqueous solution for resuspending a marc, to a resuspension operation upstream of the one preceding this pressing operation.</li><li>drying the fiber marc at a temperature below 85 ° C and without its moisture content by weight becoming less than 10%.</li></ul>

0008The process according to the invention advantageously consists in shredding carrots into particles of dimensions between 0.2 and 2 mm, followed by a treatment making it possible to inhibit the enzymatic systems of the carrot then in subjecting the shredded carrots to repeated operations pressing, resumption in suspension by water or by an exhausted juice and repressing, until obtaining, in addition to juice, a marc of fibers having, calculated on the dry matter, a content by weight of soluble sugars of less than 20% and preferably less than 5%, then drying the fiber marc,

FIRST STAGE

0009The preliminary stage of the process involves shredding carrots. This shredding, which can be carried out by grinding, bursts the cell walls and thus makes it possible then to extract, by simple pressing, both sucrose, glucose, fructose, and the other soluble substances, as well as fine particles. insoluble including the grana rich in nitrogenous matter, in lipids, and containing in addition the carotenoid pigments. The first stage of the process can be carried out by means of a rotary grater, such as a fruit grater, a crown mill or any other equipment or combination of equipment capable of producing particles with the above-mentioned characteristics.

0010If the particle size is appreciably less than 0.2 mm, the comminuted material flows by creep through the slots of the screen of the helical screw presses and, if it is greater than 2 mm, the sugar removal is imperfect because there is not enough exploded cells,

0011During grinding, or immediately after, for example less than 30 minutes and, better still, less than 0.5 minutes or 30 seconds after, an acidifying agent is used to bring the pH to the vicinity of 4.3.

0012The acidification can be carried out by means of any acid authorized in the food industry and devoid of taste such as phosphoric, citric, ascorbic, malic acid; citric acid is preferred for its complexing capacities of calcium, which allows better release of soluble pectins.

0013Subsequently, live steam is immediately injected into the ground material in order to bring its temperature as quickly as possible to 90 ° C., followed by rapid cooling to a temperature of the order of 60 ° C. in a heat exchanger. plate heat.

0014The combination of acidification at pH 4.3 with heat treatment at 90 ° C followed by rapid cooling allows effective degradation of the endogenous carrot enzyme systems of the lipoxygenase, peroxidase, polyphenoloxidase, pectinesterase, galacturonase type. degradation of natural carotenes and fibers, appearance of undesirable tastes and flavors, enzymatic browning reactions and coagulation of juices after pressing.

0015If you do not acidify carrot juice with a natural pH of 6, you must prolong the heat treatment to deactivate the enzyme systems, which accelerates the oxidation of the alpha and beta-carotenes present in the red carrot and which, moreover, can lead to coagulation of the juice after conditioning.

0016In the case of treating white carrots, this same enzyme deactivation treatment is also carried out to avoid the development of tastes, undesirable flavors as well as parasitic coloring due to enzymatic browning.

SECOND STADIUM

0017The second stage of the process, according to the invention, consists in subjecting the carrots, preferably shredded, to pressing operations and resumptions in suspension in water, until a fiber marc having a weight content of sugars is obtained. soluble (sucrose, glucose and fructose) less than 20% and, preferably, less than 5%, then dry the fiber marc.

0018It is recommended to work at a temperature below 70 ° C during the first three stages of pressing and resumption in suspension. The successive operations make it possible to eliminate, in the pressing juice, the major part (90%) of the sugar and other soluble materials and certain insoluble materials such as proteins, carotenes and lipids, all in the minimum of time, in 20 to 30 minutes for example.

0019The pressing can be carried out either with screw presses, filter presses or any other equipment allowing to express a juice from a marc.

0020It was preferred, for rapid and continuous treatment, to adopt helical screw presses with decreasing free section (from inlet to outlet) fitted with screens with transverse slits, perpendicular to the axis of the press: the width of the slits (0.160 to 0.180 mm) being smaller than the size of the smallest particles of the ground material (0.200 mm).

THIRD STADIUM

0021After the extraction of most of the soluble sugars and fine particles of insoluble matter that are found in suspension such as grana, cellular organelles, of size between 0.2 µ and 0.8 µ (Helvetica Chimica Acta 9 , 705-717, 1942), rich in proteins, lipids and carotenoid pigments, it is recommended, to obtain a product of clear color, stable, without odor or taste, to carry out a double treatment: one with hot water preferably between the third and the fourth pressing, the other with live steam after the fourth pressing. These treatments are carried out under the following conditions:

0022Regarding hot water treatment:<ul id="ul0003" list-style="dash"><li>this treatment is accompanied by heating around 70-75 ° C, then expansion to a pressure corresponding to the saturated vapor pressure of water around 70-75 ° C;</li><li>the dry matter / marc ratio is between 1/7 and 1/30, preferably between 1/10 and 1/5; below 1/7, the mixture is difficult to stir and the vapor diffuses according to preferred paths; above 1/30, the mixture is too fluid to feed a screw press;</li><li>the temperature is between 70 and 100 ° C, preferably between 70 and 75 ° C. Below 70 ° C, the marc is badly desugared and deodorized. Above 75 ° C., the fiber is "cooked", which induces a modification of the rheological behavior of the pectins which then become very plastic and this fiber can no longer be properly pressed in a screw press or a filter press and the dry matter content of the fiber is less than 15%;</li><li>the duration of treatment is between 5 and 30 minutes and preferably between 10 and 15 minutes. Shorter treatment times do not allow satisfactory desuggling. Longer durations are of no use or are detrimental to the quality of the fiber.</li></ul>

0023Regarding the steam treatment:

0024This treatment is intended to carry out a training of the terpenes constituting the essential oil of carrot present in small quantities both in the white carrot and in the red carrot and, in the latter case, to complete the oxidation of the carotenes and to lead to vapor volatile oxidation products such as beta-ionone. Indeed, both the volatile constituents of carrot essential oil (daucol, carotol) and the volatile products of carotene oxidation, such as beta-ionone are responsible for a sui generis aroma which limits the possibilities of use. carrot fiber.

0025The treatment is carried out by passing preferably dry steam (to avoid condensation of water on the fibers) superheated at 120 ° C., through a thin layer (less than 1 cm) of wet carrot fiber (20 % MS) for a period of 10 to 30 seconds.

0026This de-aromatization and deodorization operation can be carried out with a turbo-cooker, steam whitener or any other equipment making it possible to entrain, by an accumulation of air and vapor, the volatile compounds responsible for the taste and odor of the fibers.

FOURTH STADIUM

0027The last stage of the process consists in drying the fiber marc.

0028To keep all the functional and organoleptic properties of the dry fiber, the humidity of the dried fiber marc should never be less than 10% by weight, otherwise the water retention capacity of the fibers decreases significantly: from 20 to 25 g / g for a fiber with 10 to 12% moisture content, this power drops to 10 g / g for fibers with less than 5% residual moisture.

0029The temperature of the fibers should not exceed 85 ° C to avoid shriveling which has a detrimental effect on their rehydration capacity.

0030In practice, a co-current fluidized bed hot air dryer is used by mechanical internal stirring. The temperature of the marc at the inlet of the dryer is 50 to 60 ° C, the temperature of the drying air is between 110 and 160 ° C and by adjusting the air flow, we control the maximum temperature reached by the fiber.

0031The separation of steam and dry fiber is done by cycloning at a temperature higher than the dew temperature. The residence time of a fiber particle in the dryer and the cyclone is of the order of 20 to 30 seconds.

0032Given the large quantities of water required for the various suspended recoveries, it is advantageous to recycle press juices from the third and fourth stages towards the suspended recoveries produced at the outlet of the first and second pressing stages and to recover the water, necessary for the dilution of the marc from the third pressing, from the juices of the first and second pressing, previously rid of insoluble matter either by microfiltration with membranes whose pore size (0.14 to 0.2 micrometer) is less than the size of granas (0.2 to 0.8 micrometer), or by reverse osmosis, or again by distillation.

0033One of the characteristics of the process consists in recycling the juices of the first and second pressing, stripped of their color and of most of the insoluble particles and of the soluble products, by microfiltration, followed by a reverse osmosis or concentration step.

0034Thus, the process uses only the constitutional water from the carrot for the four successive suspension attempts. Excess water is eliminated in the dryer vapors, in the microfiltration and reverse osmosis retentates.

0035The appended drawing is a diagram illustrating the process according to the invention.

0036The method comprises a shredding operation 1 of the carrots brought in through a pipe 2, in the presence of citric acid brought in through a pipe 3. The shredded carrots go through a line 4 to an operation 5 of steam treatment brought in through a pipe 5a , followed by cooling in a plate exchanger with cold water (20 ° C) supplied by a line 5b. The ground product thus treated is led, via line 6, to a first pressing operation 7 making it possible to separate a sweet juice, which is rejected by a conduit 8, and a first marc which is sent, by a line 9 , to a mixer 10 in which the sweet juice coming through the pipe 20 from the pressing 19 is added via a pipe 11. From the mixer 10, the pulp obtained goes, by a line 12, to a second pressing 13 where the pulp is separated into a sweet juice which is evacuated by a conduit 14 and into a marc which is sent, by a line 15, to a mixer 16 receiving, via a pipe 17, the sweet juice coming through the pipe 28 from the pressing 27. From the mixer 16, the pulp obtained goes, by a line 18, to a third pressing operation 19 giving a sweet juice which is rejected by a conduit 20 and a marc which is sent by a line 21, to a hot water treatment operation 22 to which water is sent, coming from the microfiltration treatment then by reverse osmosis and / or evaporation of the juices 8 and 14, through a conduit 23. The marc after resuspension can undergo a first aromatization treatment 25, which consists in heating with steam supplied by a conduit 25a the product in an enclosure under a vacuum corresponding to a boiling temperature of water of 70 ° C. . The dried fibers of the conduit 33 could be more finely ground (operation 34). The mists are rejected by a conduit 25b and the pulp, resulting from operation 25, is sent, by a line 26, to a fourth pressing operation 27 where and the is separated into a juice which is rejected by a conduit 28 and in a marc which is sent, by a line 29 to a treatment operation 30 with live steam 30 brought by a conduit 30a whose vapors are evacuated by a conduit 30b; the carrot fibers thus treated are sent via a duct 31 to a drying 32 receiving steam (duct 32a) and hot air (duct 32b) and rejecting steams (duct 32c) and dietary fibers by a line 33 The juices from the pressing operations 7 and 13 coming from the conduits 8 and 14 can be treated by a sieving operation 34. Large particles (> 500 µ) are thus evacuated via a conduit 35 and the clarified juices pass through a conduit 36 ​​to undergo a microfiltration operation 37 from which a colored carotene concentrate and a colorless sweet juice are evacuated via a conduit 38 by a pipe 39. The latter undergoes a concentration operation 40 which makes it possible to recover by a pipe 41 the amount of water equivalent to that which enters through the pipe 23. The concentrated sweet juices are evacuated through line 42 to go to a distillery in order to produce alcohol.

0037The following example illustrates the invention.

EXAMPLE 1

00381000 kg of red carrots, weighing 300 ppm by weight of total carotenes, are carefully washed, then and are crushed without adding water in a rotary grater and then in a crown crusher adjusted so as to provide a crushed material consisting of particles of sizes between 0.2 and 2 mm. In order to facilitate the deactivation of the enzyme systems, 10 liters of 50% by weight solution of citric acid are added during grating.

0039This ground product is pressed for the first time (first stage), the marc (238 kg) is re-soaked with the spent carrot juice from the third pressing stage (498 kg). It is pressed a second time (second stage), the resulting marc (207 kg) is re-soaked with spent carrot juice from the fourth pressing stage (475 kg), then it is pressed a third time (third stage - 172 kg ). The pressing is carried out in three helical screw presses and the rebimbing is carried out "continuously" in centrifugal mixers. This treatment takes 20 minutes and is carried out at a temperature between 50 and 60 ° C.

0040The marc from the third pressing stage is mixed with 250 liters of carrot juice from the first and second stages, previously microfiltered and freed of soluble sugars by treatment in reverse osmosis. It is then brought to 80 ° C. The mixture is placed in a container fitted with an efficient agitator making it possible to suspend the fiber contained in the marc, maintained under a pressure corresponding to the vapor pressure of water at 70 ° C. for at least 10 minutes and less than an hour. This operation allows a first flavoring of the carrot fiber.

0041The content of the pulper is used to feed a fourth helical screw press which provides grounds (162 kg at around 20% of total dry matter). Pressing juice is used for resuspending the marc from the second pressing stage.

0042The hot marc (50-60 ° C) is then placed in a thin layer (less than 1 cm and preferably equal to 5 mm) between two textile or metal fabrics crossed by a continuous flow of superheated steam at 120 ° C for 1 minute , then introduced into a co-current hot air dryer with a fluidized bed. The energy required for drying is provided by heating outside the dryer chamber, by steam at 12.10⁵ Pascal (160 ° C) and by hot air at 165 ° C. A carrot fiber having the composition and the characteristics given in Table 1 is collected by cycloning at 80 ° C.

0043The juices from the first and second pressing (about 1100 liters) are freed from coarse insoluble fractions (creep through the sieve). About 5% of the juice flow is thus removed with a centrifuge or a vibrating screen. The rest of the juice is directed to a micro-filtration device. This operation makes it possible to separate, with a filter with a pore size close to 0.2 μ, the sugars from the insolubles responsible for the color. The insoluble particles of carrot juice can thus be concentrated between 25 to 50 times (from 10 kg to 20 kg of concentrate). The filtered carrot juice (approximately 1000 kg) is concentrated using an evaporator until 250 liters of water have been recovered necessary for diluting the third pressing marc. The rest of the juice (about 850 kg) is used as a fermentation substrate for the production of alcohol.

0044The dietary fiber content was measured according to the official method AOAC (Association of Official Analytic Chemist, published by PROSKY. L. et al., J. Assoc. Off. Anal. Chem. (1984), 67, 1044-1052 ).

0045The water retention capacity is determined according to the following protocol:<ul id="ul0004" list-style="dash"><li>drain the sieve for 5 minutes (PO);</li><li>return the sieve to the crystallizer;</li><li>add 10 g of fiber (P);</li><li>let stand for 20 minutes;</li><li>drain the sieve for 5 minutes;</li><li>weigh (P1).</li></ul>

0046The water retention capacity (CRE) in g / g is equal to:<maths id="math0001" num=""><math display="block"><mrow><mtext>CRE (g / g) = ((P1 - PO) - P) / P</mtext></mrow></math><img file="EP0478401A2_D0001.tif" /></maths>

0047The ion exchange capacity is determined according to the following protocol:

00482.500 g of dry ground fibers are dispersed in 250 ml of 0.1 M hydrochloric acid, the mixture is stirred for 16 hours, then filtered, rinsed with 5 x 200 ml of distilled water, dried (100 ° C. for 12 hours). 1,000 g of fibers put in acid form are dispersed in 50 ml of distilled water, and the pH of the suspension is reduced to 7.0 by adding 0.1 N KOH (volume V).

0049The cation exchange capacity (CEC) in milliequivalents per gram of fibers (meq / g) is<maths id="math0002" num=""><math display="block"><mrow><mtext>CEC = V x 0.1 meq / g.</mtext></mrow></math><img file="EP0478401A2_D0002.tif" /></maths><tables id="tabl0001" num="0001"><img file="EP0478401A2_D0003.tif" /></tables>