FR2813010A1 - PROCESS FOR THE MANUFACTURE OF AN EXTRACT OF PECTIN-RICH CITRUS, AND EXTRACT OBTAINED BY THIS PROCESS - Google Patents

Abstract

The invention concerns a method for continuous production of citrus fruit extracts rich in soluble pectins, which consists in: eliminating the outer part of the peel consisting of the zest; heating the core citrus at a temperature less than 110 DEG C; subjecting in less than three seconds, the heated citrus fruit to a reduced pressure; finally, treating the resulting product so as to produce an extract more or less rich in pulp.

Description

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The invention relates to a process for the production of a citrus extract rich in pectin. It also relates to the extract capable of being obtained by said process. It also extends to drinks incorporating the extract.

In the following description and in the claims, the term citrus fruit designates in particular, but is not limited to, fruits of the oranges, lemons and pomelo type. The document FR-A-2 731 588 describes a composition for stabilizing drinks based on fruits, including especially orange juice. Indeed, the latter contains a certain amount of pulp which tends to sediment over time, making a composition called unstable. This is the reason why it is necessary to give the juice all its aroma as well as to standardize its appearance, to stir the fruit juice before consumption. The stabilizing agent proposed consists of a composition based on pectins and alginates which is added to the orange flavor during the preparation of the drink thus allowing the pulp to be kept in suspension. This solution therefore has the drawback of requiring an external stabilizing agent of non-natural origin, which must be added extemporaneously during the preparation of the drink.

WO 99/47008 tends to solve the problem of the origin of the stabilizing agent. It starts with the observation that the skin of citrus fruits is very concentrated in pectins. It is further indicated that pectins have stabilizing properties of solid particles. Consequently, this document describes a process according to which a mixture of parts of citrus fruits and in particular of skin, juice and core, is subjected to an aqueous extraction resulting in the obtaining of an aqueous extract containing solid particles. The extract is then separated from its large particles so as to obtain a liquor comprising up to 15%, preferably between 1 and 5% of pulp by weight. The liquor is then subjected to the action of a pectolityque enzyme allowing the molecular weight of the pectins present in the liquor to be reduced to make them soluble and surfactant. We then proceed to a pasteurization and centrifugation step. If this process makes it possible to improve the retention in suspension of the pulp present in the liquor, the pectin content (10,000 to 20,000 mg / liter) is still too low to obtain satisfactory stability at

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 long-term composition. In addition and above all, the aqueous extraction does not make it possible to directly dissolve the pectins so that it is necessary to carry out a subsequent enzymatic treatment.

The problem which the invention proposes to solve is therefore to develop a process for manufacturing citrus extract which makes it possible to directly extract the soluble pectins and this, in significant quantities.

Another problem which the invention proposes to solve is to develop a process for the manufacture of extracts, the pulp content of which can vary up to high contents, of the order of 1 to 2.5% by weight.

To do this, the invention provides a process for the production of citrus extracts rich in soluble pectins, according to which # the whole citrus fruit is heated to a core at a temperature below 110 ° C .; # submit in less than 3 seconds, the citrus fruit heated to a reduced pressure; # finally, the product obtained is treated so as to lead to an extract more or less rich in pulp.

The applicants have in fact found that, quite surprisingly, the fact of applying reduced pressure in a time of less than 3 seconds to a whole heated citrus fruit makes it possible to degrade the cell walls of the albedo of the skin of the skin. citrus and concomitantly extract the soluble non-volatile pectins present in said albedo, in significant quantities. For the record, the skin of citrus fruits has two distinct parts. The external part called flavedo contains the majority of essential oils and volatile aromas while the internal part, called albedo contains essentially soluble pectins. In other words, not only are the pectins present in the final extract extracted directly without requiring additional steps and are 100% natural, but in addition, their large proportion makes it possible to improve the long-term stability of the extract even for large quantities of pulp. Furthermore, the process of the invention has the advantage of being carried out on whole citrus fruits, that is to say citrus fruits which have not undergone any physical deterioration and oxidation.

The combination of heating, the temperature of the citrus fruit at heart being advantageously between 60 and 90 C, preferably equal to 80 C, with the

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 placing under reduced pressure, preferably less than 0.075 bar absolute, in a time of less than 3 seconds, advantageously in less than a second, leads to the following phenomena. The brutal evacuation causes an instantaneous evaporation of the water of constitution of the citrus fruit, which leads to a total or partial degradation of the citrus tissues due to the creation of intercellular micro-channels, favoring the extraction of compounds dyes and polysaccharides, especially pectins. It also causes an inhibition of endogenous enzymes due to the bleaching of the fruits, which makes it possible to avoid the phenomena of enzymatic browning. The combination of heat and brutal reduced pressure also leads to pre-grinding due to the instantaneous evaporation of part of the water of constitution. Finally, putting under reduced pressure causes immediate cooling of the plant material due to an abrupt return to thermodynamic equilibrium, in practice from 90 ° C. to around 40 ° C. If rapid passage under reduced pressure constitutes one of the essential elements of the process, said pressure can be maintained for a variable duration, in practice between 3 and 4 seconds.

In an advantageous embodiment, the water of constitution evaporated during the sudden placing under reduced pressure is condensed, for example by means of a surface exchanger, then recovered in the form of aromatic water. This aromatic water, representing approximately 8% of the mass of the product, contains different families of compounds, in particular many terpene hydrocarbons which it is necessary to eliminate. The aromatic water is therefore subjected to various purification treatments, for example to column fractionation distillation. The aromatic water then treated can optionally be reintroduced into the final extract.

As already said, the product obtained at the end of the heating stages and then under brutal reduced pressure, is then treated according to the desired pulp content in the final extract. The pulp consists of the cell walls resulting from the degradation of albedo during the brutal reduced pressure of the citrus fruit. This pulp can enter into the composition of the final extract in variable contents, depending on the method of separation of said pulp.

Thus, in a first embodiment, to obtain a citrus extract having the appearance of a juice, that is to say very poor in pulp, the treatment consists of a pressing, advantageously carried out at atmospheric pressure. However, the pulp content of the extract may vary depending on the method of pressing. In practice, juices

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 citrus fruits obtained at the end of the process of the invention comprise a very low pulp content, less than 0.2% by weight.

In a second embodiment, to obtain a citrus extract rich in pulp, having the consistency of a puree hereinafter called pectic puree, the treatment consists in a refining. By the term refining, we mean an operation consisting in passing the product obtained through a grid or equivalent, the size of the mesh of which allows the passage of a greater or lesser part of the pulp. Advantageously, the refining is carried out under vacuum so as to reduce the oxygen content in the refined product. In practice, the citrus puree obtained at the end of the process of the invention contains between 1 and 2.5% of pulp by weight of the wet matter treated.

As already said, one of the advantages of the process is to succeed in directly extracting soluble pectins and this in large quantities. The applicants have found that the content of soluble pectin in the final extract is important in the puree and the juice. In practice, the juice obtained by pressing contains between 0.3 and 1.8% of soluble pectins by weight of the treated wet matter. Likewise, the mash obtained by refining contains between 0.5 and 2.5% of soluble pectins by weight of the treated wet matter.

The content of soluble pectins (P.S.) and cell walls (P.C.) or pulp in the purees, is variable depending on the fruit: thus, for lemon, P.S. is close to 2% and P.C. is close to 2%. ; for Valencia oranges, P.S. is close to 1% and P.C. close to 2.5%; for the grapefruits, PS is close to 0.5% and PC close to 1%, the proportions being indicated relative to the wet weight of the treated product and for heating at the heart of the fruit at 80 ° C., before putting under reduced pressure brutal.

The invention also relates to beverages incorporating extracts capable of being obtained at the end of the process in the form of juice or purees. Such drinks result from the addition of water and sweeteners to the extracts obtained.

Furthermore, in the event that the citrus fruits have undergone a certain number of treatments during their cultivation or storage, in particular treatments with pesticides, or that the flavedo is heterogeneous or does not contain interesting extractable compounds, it becomes compulsory, before heating then brutally put under reduced pressure, to eliminate the external part of the skin constituted by the flavedo. Elimination of flavedo can be

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 carried out in different ways, in particular by scraping or peeling the citrus fruit. The scraping operation in practice involves the elimination of a small part of the albedo.

In an advantageous embodiment, the flavedo-albedo mixture from scraping can be treated separately to recover the aromatic waters after purification by distillation, absorption, decantation, so as to select volatile aromatic compounds. These aromatic fractions can be totally or partially reintroduced into the juices or purees obtained at the end of the process of the invention.

On the other hand, the preliminary scraping step is not required when the citrus fruit does not present on its surface residues of the pesticide or fungicide type or when it contains interesting extractable compounds (color and polyphenols). More specifically, citrus fruits are not scraped if the major compounds contained in the flavedo can bring organoleptic interest to the product. Part of the essential oils contained in the flavedo will be recovered with the aromatic waters (upper oleic phase). Part of these compounds after purification can be reintroduced into the product. Depending on the type of citrus fruit (lemon, orange, grapefruit), the treatment by temperature rise and rapid vacuuming allows yields of essential oils varying from 1.7 to 2.5 liters per tonne of whole fruit to be obtained. These oils have conventional compositions and in this sense have a very high content of limonene (more than 95% in essential oils of pomelo).

According to another characteristic of the process of the invention, all of the treatments can be carried out either continuously or discontinuously.

The invention also relates to the citrus extract capable of being obtained by the process described above.

It also relates to a citrus puree comprising between 0.5 and 2.5% of soluble pectins and between 1 and 2.5% of pulp by weight of the wet matter treated. Finally, it relates to a citrus juice comprising between 0.3 and 1.8% of soluble pectins by weight of the treated wet matter.

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 The invention and the advantages which result therefrom will emerge more clearly from the following exemplary embodiment in support of the appended figures.

FIG. 1 and a diagram representing the different stages of the process of the invention.

FIG. 2 is a comparative table of the physicochemical characteristics of the purees of the invention and of the traditional juices.

FIG. 3 is a comparative table of the biochemical characteristics of the purees of the invention and of the traditional juices.

The lemons used in this example are from the Portofiori variety (Spain), the oranges from the Valencia variety (Spain) and the pomelo from the Cavendish variety (Israel). They have average masses respectively equal to 158 t 23 g .; 181 31 g. and 379 ZL 47g.

As shown in the diagram in Figure 1, these treated citrus fruits were subjected, in a first step, to a partial peeling using a fruit scraper (Polycitrus type from INDELICATO). This treatment removes the flavedo and part of the albedo. It follows the elimination of the majority of essential oils, pesticides and fungicides contained in flavedo as well as some of the compounds contained in albedo. This treatment results in a total loss in mass of the fruit varying from 0.5 for pomelo to 5% for lemons (2% for oranges). The aromatic compounds contained in the flavedo (mainly essential oils and terpene compounds) can be recovered by distillation and fractionated on a column to be reintroduced in the juices or purees before final packaging. In a second step, the whole scraped fruit is treated by brutal reduced pressure. More specifically, They are introduced into a steaming chamber where they are heated to 80 ° C. then brutally introduced (opening time of the pneumatic valve less than 1 second) in an expansion chamber where a high vacuum prevails less than 0.075 bar absolute.

The water vaporized is, by the use of a surface exchanger, condensed and then recovered in the form of aromatic waters (approximately 10% by mass of the product). These aromatic fractions contain different families of compounds with in particular many terpene hydrocarbons. They can be recovered by distillation and fractionated on a column.

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 Products from brutal reduced pressure can undergo 2 different technological paths. The first voice calls for a pressing of the product in order to reduce the final pulp content and to obtain pectic citrus juices. The second solution consists in refining these products (PH3 / Auriol type refiner provided with a cylindrical grid (perforation of 1 millimeter in diameter)) and in obtaining pectic citrus purées (very rich in pulp). This refining is carried out under vacuum in order to reduce the final oxygen content in the refined products. The first and second stages of the process induce a first reduction in the oxygen content (the product obtained at the end of the two stages has an oxygen content of approximately 30%) by the effect of the high vacuum and the refining under vacuum. causes a decrease in the oxygen content up to about 5%. This low oxygen content limits the phenomena of oxidation and therefore of non-enzymatic browning.

The juices or purees can then be added to water or sugar in order to obtain drinks with lower viscosity due to lower pulp (cell wall fragments) and lower pectins contents. The drinks, juices or purees are finally homogenized, pasteurized and then packaged.

The use of refining to obtain purees makes it possible to obtain extraction yields higher than those traditionally obtained by the conventional processes for obtaining juice by pressing the juice vesicles, without incorporating citrus peel, of the type of those developed by FMC corporation.

Thus, the treatment of lemons according to the diagram in FIG. 1 makes it possible to obtain a final mash extraction yield (that is to say after scraping, heating, brutal reduced pressure and refining) of 61%. The average juice yield obtained by a traditional process is around 35% (with values varying from 27 to 43 depending on the size and variety of lemons). The yield of pectic lemon puree obtained by this new process is therefore almost twice that of traditional extraction processes.

The treatment of oranges by this new process provides a yield of 60%. The use in the traditional process industry allows, depending on the size of the oranges and the process used, to obtain yields of around 50%.

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 Finally, concerning the grapefruits, a yield of 60% is reached whereas the traditional methods make it possible to obtain yields varying from 45 to 55% depending on the size of the grapefruits and the process used.

This increase in yield in the 3 cases is due to the incorporation of part of the albedo of the fruit in the juice. The albedo is degraded during treatment by brutal reduced pressure; this is incorporated into the juice during the refining of the product.

The physico-chemical characteristics of the purees obtained by all of the treatments: partial peeling, brutal reduced pressure, refining (cf. Figure 1) as well as those of the juices obtained by using a traditional process are presented in Figure 2 .

The lemon puree, obtained by the treatments designated in Figure 1, has a pH of 2.85 and a titratable acidity of 53.6 mEq. per 100 g. of product. By comparison, a traditional lemon juice has a pH of 2.50 and a titratable acidity of 84.0 mEq. per 100 g. of product.

The orange puree obtained by these treatments (Figure 1) has a pH of 3.60 and a titratable acidity of 15.8 mEq. per 100 g. of product. By comparison, a traditional orange juice has a pH of 3.54 and a titratable acidity of 17.0 mEq. per 100 g. of product. Likewise, the grapefruit puree obtained by these treatments (Figure 1) has a pH of 3.65 and a titratable acidity of 13.1 mEq. per 100 g. of product. By comparison, a traditional pomelo juice has a pH of 3.25 and a titratable acidity of 13.0 mEq. per 100 g. of product.

The lower acidity of the purees obtained as described above in Figure 1 compared to juices obtained in the traditional way is due to the addition of albedo in the products during the rapid vacuuming and refining stages. The citrus albedo has a pH varying from 4 to 4.5 and a low titratable acidity (due to a low organic acid content in the albedo) compared to the values obtained in the juices contained in the segments.

The color study carried out using a chromameter (Minolta, CR-A70) in (L, a, b) mode on the different products is presented in the table in Figure 2.

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 The intensity of product clarity follows the increasing value of parameter L and the intensity of the yellow color (particularly sought in citrus juices and purees) follows the increasing value of parameter b.

The lemon, orange and pomelo purees obtained by the process described in FIG. 1 have values of L respectively equal to 59.6; 58.8; 44.9 while the lemon, orange and pomelo juices have L values respectively equal to 40.9; 49.0; 34.1. Citrus purées therefore have a lighter shade compared to that of traditional juices.

Lemon, orange and grapefruit purees have b values equal to 10.5 respectively; 40.7; 20.5 while the lemon, orange and pomelo juices have b values equal to 2.3 respectively; 24.6; 2.5. Citrus purées are characterized in that they have a more intense yellow color.

In the end, the colors of the lemon, orange and pomelo purees are characterized by a light shade and an intense yellow.

The dry matter of the purees and the juices were determined by gravimetry and the dry solids by refractometry (Refractometer 0-32 Brix).

The lemon, orange and pomelo purees have dry matter percentages relative to wet matter, respectively, equal to 11.6; 13.1 and 12.6% (see Figure 2) while traditional juices have much lower dry matter percentages (8.5, 7.0 and 9.6% respectively). These markedly higher values in the purees treated as indicated in FIG. 1 are attributed to a higher content of fragments of cell walls (pulp). The treatment by brutal reduced pressure and the refining are concomitantly responsible for this clear increase in dry matter: part of the albedo (particularly rich in cell walls) was incorporated into the product during these 2 stages.

Likewise, the lemon, orange and grapefruit purees have percentages of soluble dry extract relative to wet matter respectively equal to 10.0; 10.1 and 11.0 whereas traditional juices have significantly lower percentages of soluble dry extract (7.4, 6.1 and 9.1% respectively). These very clearly higher values in purees are due to a high value of the dry extract soluble in albedo (high

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 content of soluble sugars and pectins), part of which is incorporated into the product during heating / reduced pressure and refining treatments.

The finished products share their consistency, their viscosity and their pulp content, the rheological characteristics of a puree which are described below.

The viscosities of the purees were determined by using a Haake viscometer (model 550) fitted with an MV-DIN module.

These 3 products have a rheo-fluidifying behavior and are not thixotropic. The apparent viscosity measured at constant speed (100 rad.s- ') varies from 21 Pa.s for the lemon puree to 260 mPa.s for the pomelo puree (820 mPa.s for the orange puree). By comparison, values lower than 2.5 mPa.s are obtained in the case of citrus juices obtained by a traditional process.

These very large differences in viscosity are mainly attributed to the very high contents of cell walls and soluble pectins in the purees obtained by this new process.

The flow threshold for these purees follows the same classification with values respectively equal to 70, 15 and 7 Pascals for lemon, orange and pomelo purees. These threshold values are, depending on the nature of the puree, comparable to those obtained for example for a chocolate paste (- 15 Pascals) or a tomato puree (- 30 Pascals).

The consistency of these purees, determined using a Bostwick consistometer, is proportional to the distance traveled by the puree under the effect of its own weight (100 g.) In 30 seconds on a horizontal surface. The most consistent puree is that from lemon (d = 2 cm) while that from orange and pomelo are slightly more fluid (respectively d = 5.5 cm and d = 9 cm). The consistency of the juices obtained in the traditional way could not be measured: these juices have no consistency due to their low content of cell wall fragments and soluble pectins.

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 The absence of essential oil in the final purees may be doubly justified - the major part of the essential oils contained in the citrus flavedo (bright yellow part rich in glands with essential oils) was partially removed during the passage on the scraper fruit (type Sfumatrice, Polycitrus or Citrorap), - the essential oils still present after partial scraping of the flavedo are vaporized during the passage under brutal reduced pressure and are therefore recovered in aromatic waters. This step allows not only a breakdown of the plant material but also a total elimination of the essential oils still contained in the flavedo.

The results concerning the contents of MIA, of soluble pectins as well as their contents of galacturonic acid are presented in the table of FIG. 3.

The contents of cell wall fragments and of soluble pectins of these products were determined by the method of precipitation with 80% ethanol (M.I.A. Material Insoluble in Alcohol).

The M.I.A. consisting mainly of parietal fragments and soluble pectins are present in very high proportions in the purees resulting from the treatments of Figure 1 with increasing values of 1.6% (relative to the wet matter) in the pomelo puree, 3, 4% in orange puree and 3.8% in lemon puree. The average percentages of galacturonic acid which reflect the purity of these polysaccharide components are approximately 30%.

Conversely, traditional juices have low contents of material insoluble in alcohol with values in the 3 juices less than 0.6%. In addition, the purity of these polysaccharides in galacturonic acid is low with values being around 10% in the 3 traditional juices.

Treatment by brutal reduced pressure therefore makes it possible to obtain products much richer in fragments of cell walls with higher contents of pectic polysaccharides.

The contents of pectins soluble in alcohol-insoluble materials (M.I.A.) obtained from citrus fruit purees were determined under 2 different extraction conditions: in a weakly acidic medium at room temperature (pH 4;

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 20 C) and in a strongly acid medium when hot (pH 1.5; 90 C). These contents are respectively equal to 0.77; 0.41 and 0.23% for purees of lemon, orange and pomelo in the case of extraction at pH 4, 20 C. In the case of a stronger extraction (pH 1.5, 90 C), the contents of soluble pectins are logically, clearly higher with contents respectively equal to 1.84; 1.06 and 0.56% in the purées of lemon, orange and pomelo. The galacturonic acid contents of these pectins are between 50 and 70%.

The contents of cell wall fragments are determined after extraction at pH 4. 90 C considering that all of the soluble pectins have then been extracted. These contents are logically lower in the case of M.I.A. of pomelo (1.04%) and are respectively equal to 1.96 and 2.33% in the case of M.I.A. lemon and orange puree.

The contents of soluble pectins have not been determined on traditional juices due to the too small quantities of pectins which would have been obtained (less than 0.1 in the 3 traditional juices).

The high levels of M.I.A. and in soluble pectins in the citrus purees obtained from the treatments presented in FIG. 1 are directly correlated to the high viscosity and the high consistency of these purees.

 Regarding the pectic juices obtained by pressing after the brutal reduced pressurization step, the cell wall contents are very low and vary depending on the type of pressing. The contents of soluble pectins, on the other hand, are close to those of the purees and vary from 0.5% for the pectic juice of pomelo to 1.5% for the pectic juice of lemon (case of extraction at pH 1.5; 90 VS).

Tests carried out by an expert analysis jury tell us the organoleptic characteristics of these 3 purees - the colors of the purees are pleasant, clear with intense bright yellow colors, especially in orange and pomelo purees.

- the flavor in the 3 products is similar to that of a traditionally squeezed juice but with a slightly less marked freshness, - no cooked note is observed, revealing too intense heating, denaturing the initial aromatic characteristics,

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 - the acidity on the palate, particularly in lemon and pomelo purees, is very pleasant and non-aggressive, unlike that of a traditional juice, - the products bring no heat to the mouth, which confirms the total absence of essential oils in the final purees, - the products present a slight bitterness (more marked in the case of pomelo) due to the extraction of albedo from the fruits during the manufacturing process which can be easily attenuated by increasing the sugar content of the products. These new products thus presented are called to be marketed as intermediate food products and can therefore be used as a manufacturing additive.

The different areas of application are as follows - purees used in dairy products, baby foods or pastries, - nectar-type drinks obtained after dilution of the purees (see Figure 1): a 1/3 dilution with l according to the expert jury, water with the same degree Brix brings the best compromise concerning viscosity, aromatic intensity, bitterness and acidity in the mouth.

The new products obtained use three consecutive fruit processing devices which can be adapted to industrial production by simply dimensioning its components. Indeed, these three technologies: fruit scraper (type Polycitrus brand INDELICATO), brutal reduced pressure, refining (type PH3 / Auriol or vacuum refiner) can be or are automated so as to operate continuously and thus optimize the energy balance.

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Claims (13)

 CLAIMS 1 / Process for the production of citrus extracts rich in soluble pectins, according to which # the whole citrus fruit is heated to a core below 110 C; # submit in less than three seconds, the citrus fruit heated to a reduced pressure; # finally, the product obtained is treated so as to lead to an extract more or less rich in pulp. 2 / A method according to claim 1, characterized in that the product obtained by pressing is treated, so as to obtain an extract in the form of a juice, with a low pulp content. 3 / A method according to claim 1, characterized in that the product obtained by refining is treated, so as to obtain an extract in the form of a puree, rich in pulp. 4 / A method according to claim 3, characterized in that the refining is carried out under vacuum. 5 / A method according to claim 2, characterized in that the citrus puree contains between 1 and 2.5% of pulp by weight of the treated wet matter. 6 / A method according to claim 2, characterized in that the juice obtained by pressing contains between 0.3 and 1.8% of soluble pectins by weight of the treated wet matter. 7 / A method according to claim 3, characterized in that the puree obtained by refining contains between 0.5 and 2.5% of soluble pectins by weight of the treated wet matter. 8 / A method according to claim 1, characterized in that before heating the entire citrus fruit, the flavedo and a small part of the albedo are removed by scraping the citrus fruit. 9 / A method according to claim 8, characterized in that the flavedo / albedo mixture is treated separately to recover the aromatic waters.  10 / Citrus extract capable of being obtained by the process of claim 1. <Desc / Clms Page number 15>  11 / Citrus puree comprising between 0.5 and 2.5% of soluble pectins and between 1 and 2.5% of pulp by weight of the wet matter treated. 12 / Citrus juice comprising between 0.3 and 1.8% of soluble pectins by weight of the treated wet matter. 13 / Beverage incorporating the extract of claim 10.