WO2006094413A1

WO2006094413A1 - Method for the production of pectin from citrus fruits, in particular bio-certifiable pectin

Info

Publication number: WO2006094413A1
Application number: PCT/CH2006/000066
Authority: WO
Inventors: Ernst Schaltegger; Fritz K. Jaisli
Original assignee: Obipektin Ag
Priority date: 2005-03-07
Filing date: 2006-02-02
Publication date: 2006-09-14
Also published as: CH695979A5; AR055039A1

Abstract

A method for the production of pectin from citrus fruits comprising a process step for the production of a raw material (10) containing citras fruit components, a process step for conducting at least one acid hydrolysis (15, 20, 55, 60) and at least one pectin extraction step (25, 30, 35, 65, 70, 75). The acid hydrolysis step (15, 20, 55, 60) is conducted in the own citrus juice. Bio-certifiable pectin is obtained in one implementation of this method when biologically certified citrus fruits and biologically certified ethyl alcohol as precipitating means are utilised.

Description

Method for the production of pectin from citrus fruits, in particular bio-certifiable pectin

Technical area of the invention

The present invention relates to a method for the production of bio-certifiable pectin from citrus fruits. The method also allows the extraction of steam distilled citrus oil and citric acid. The residual material remaining after the various extractions is suitable for the production of ύpacifϊers or for use as cattle feed supplement.

State of the art

The conventional methods for obtaining pectin involve hydrolysis and extraction from the peel of citrus fruit, such as lemons, limes, grapefruits, oranges, tangerines, mandarins, etc. Thus, a lemon plantation with an area of, for example, 5 km² and an average crop of approximately 9000 tons of fresh fruit per km² and year will yield approximately 2000 tons of dried peels containing an average of 33% pectin. This results in approximately 600 tons of pure pectin per year. This amount is too small to warrant an economically sustainable local production of pectin using any of the currently available processes.

In addition, small to mid-size on-site production plants often extract citrus oil through prior grating of the peel, resulting in a considerable pectin loss. In the subsequent juice extraction and straining process the fruit's structure and cell wall components are utilised for cattle feed, whereby the pectin and often also the citrus oil contained therein is lost.

Drying of citrus peel constitutes a considerable cost component in the overall energy balance and the increasing energy and transport costs have an additional impact on the raw material costs. In the case of citrus peel, raw material with only 33% usability is transported over long distances. Separation, drying, packaging, storage and transport of these peels pose an increased risk in regard to bacterial and fungal contamination and can lead to the total loss of entire batches.

As described in WO 00/ 09567, RU 2,116,313, US 5,627,269, US 2,548,895, US 2,586,407 and US 6,787,177, the usual extraction procedure involves the use of water acidified to a pH between 1 and 3 with a mineral acid, such as nitric acid, sulphuric acid or hydrochloric acid. The crushed citrus peels are added to this acidified water and then slightly stirred at a temperature between 60 to 95 degrees Celsius for a time period ranging from 30 minutes to several hours. The solid-water-mixture is subsequently separated utilising a variety of methods, such as centrifugation or filtration. The process is completed by passing the raw juice through a polishing filter, transforming it into a clear juice, to which alcohol is added to precipitate the pectin. The clear juice is concentrated through evaporation in order to minimise the amount of alcohol used. The isolated precipitate (pectin) is then washed again with alcohol, dried and ground. Other process variants include continuous counter-current extraction in vats or percolation in columns or boilers.

If a pectin with a high methoxyl content (over 100,000 g/mol, over 50% esterification) is required, acid extraction is preferred. If a pectin with a low methoxyl content (less than 100,000 g/mol, fewer than 50% esterification) is required, strong bases, such as sodium or potassium hydroxide, are used.

The molecular weight of the extracted pectin is also influenced by the concentration of the utilised acids and bases. Concentrations in the range of 0.01 to 0.8% result predominantly in pectin with a low molecular weight, while concentrations exceeding 0.8% will dissolve pectin of a higher molecular weight. Typically, a concentration of 0.3 to 0.6 weight percent is used.

The total amount of extractable pectin depends on a number of factors, i.e. the pH, the particle size of the peels, the extraction time and the extraction temperature. The same amount of pectin can be extracted, if a high acid or base concentration is applied at high temperature during a short period of time, or a low acid or base concentration is applied at low temperature during a long period of time.

The following process parameters are generally used to extract pectin with a high molecular weight:

• Temperature between 60 to 130 degrees Celsius, preferably 70 degrees Celsius

• Process time 30 minutes to 10 hours, preferably 5 hours

• pH 1 to 3, typically 1.2

Pectins with a low molecular weight are usually extracted using the following process parameters:

• Process temperature 90 degrees Celsius

• Process time 2.5 hours

• pH 1.8

ERSATZBLATT REGEL 26 The use of mineral acids and bases prevents pectin from obtaining a bio-certification due to non-compliance with the relevant minimal criteria. This drawback can be overcome with the use of commercially available enzymes. The utilisation of enzymes, however, has considerable disadvantages due to the difficulties in controlling their chemical reaction (unwanted side reactions of the enzymes) and because the yields obtained are too low for a commercially interesting pectin.

Summary of the invention

It is an object of the present invention to overcome the disadvantages of the prior art by providing a method for the on-site extraction of pectin, which can also be applied to smaller production plants.

It is another object of the present invention to provide a method for extracting bio-certifiable citrus pectin, the same method also enabling the simultaneous extraction of bio-certifiable essential oils and bio-certifiable citrus pectin. The content of essential oils in fruit juice is, at approximately 5 per mille relating to the fresh weight of the lemons, the same as that found in the peel. Bio-certified pectin is a pectin obtained exclusively by processing organically grown and bio-certified natural products as well as organically certified precipitating means.

The solution set forth in the claims thus accomplishes, in particular, the objectives outlined below, offering the corresponding advantages:

Local production of low-priced pectin in plants of a size that would normally be too small for industrial production,

Cost savings in the drying of the citrus peel,

Savings in transportation costs, as the pectin weight only constitutes approximately one third of the total weight of the citrus peel,

Production of a bio-certifiable pectin, as all the ingredients are bio-certifiable,

An increase in the pectin yield per weight unit of raw material because, in the case of citrus oil extraction, the grated peel can also be utilised,

An increase in the pectin yield because the inner parts of the citrus fruit containing pectin can also be utilised in the process,

Production of bio-certifiable citric acid after extraction of the pectin,

The integrated and complete recovery of the bio-certifiable citrus oil contained in the fruit, that is, the citrus oil contained in the peel and the pulp,

An alternative production of a bio-certifiable citrus juice concentrate with a controlled pectin, citrus oil and citric acid content.

Production of bio-certifiable carotenes or production of bio-certifiable citrus oil with a high carotene content,

Production of bio-certifiable opacifiers (cloudifiers) or bio-certifiable animal feed supplements,

Description of an exemplary embodiment of the invention

The general procedure in accordance with the present method will be apparent from the following description of an exemplary embodiment of the invention. At first, the harvested citrus fruits are washed, sorted and subsequently grated in a machine under a continuous water jet. The pressed-out grate shavings and the grated citrus fruits are then crushed and reduced to small pieces. The entire fruit is crushed from the first, if no oil extraction from the peel is to take place. Afterwards, the resulting fruit mass is cooked in its own juice under slight stirring. Depending on the pH and buffering of the fruit mass, citrus juice and/or citric acid can be added.

For the production of carotenes, at this stage the citrus oil floating on the top is removed through decanting and the citrus oil is cither separated after cleaning in a rotary evaporator under vacuum, which results in the carotenes crystallising out, or it is concentrated until a citrus oil containing a high concentration of carotenes is obtained, which, after drying, is highly suited for storage and conservation of the carotenes.

The pH of the fruit mass has a value between 2.5 and 3. This pH value is substantially higher than that obtained when mineral acids arc used. A higher temperature and longer cooking period, however, result in pectin yields similar to those obtained with conventional procedures. Citrus oil is obtained by increasing the temperature to 100 degrees Celsius, whereby the citrus oil is entrained by the emerging steam and earned to the condenser, where it is decanted and dried after cooling of the condensate. The same process can also be earned out under vacuum at considerably lower temperatures.

Alcohol, for example ethyl alcohol or isopropyl alcohol is then added to the clear juice previously obtained through filtration of the citrus oil in order to precipitate the pectin. Similarly, bio-pectin is produced using bio-certified ethyl alcohol as a precipitating agent. This process can be repeated several times and the alcohol used for the precipitation can be recovered in a rotary evaporator. The water left over after precipitating and removing the pectin and the alcohol is rich in citric acid is subsequently cooked again in a container at elevated temperature after adding fresh water and separating the filter cake and afterwards treated in the abovementioned way. Example

In an extraction trial at a small lemon production plant in South America the following raw material was used:

Composition of the average lemon:

Fresh weight per lemon: 168 g

Proportion of fresh peel: 53.4 g = 12.5 g (23.4 %) dry mass

- Pulp: 114.5 g = 10.7 g (9.3 %) dry mass

The whole fruit is utilised in the process described herein, to which it would be advantageous to add the step involving the grating of the outmost peel layer and associated oil extraction, the step involving the extraction of carotene from the same material, as well as the step involving the extraction of citrus oil from the pulp.

18 lemons with a total dry matter content, that is, the content including peels and pulp, of 417.6 g, or a total dry matter content in the peels of 225 g, were used in this trial. The yields are based on the peel dry matter because the pectin content in the pulp, without peel, was not determined (see reference sign AS in fig. 1).

In the first step the lemons were crushed with a disc mill to approximately 5 mm thick and 1 cm to 4 cm long strips (10). In the following acid hydrolysis step (15), 3024 g (18 fruits) of this fruit mass were added to an extraction vessel, diluted with 1700 g of water at a temperature of approximately 70 degrees Celsius (16), mixed and blended with a blender, while slowly heated to a temperature of 90 degrees Celsius. Further addition of citrus juice or citric acid was not necessary, although this process step (17) can be added to adjust the pH to an optimal level and to obtain sufficient buffering. It took one hour to increase the temperature from 70 degrees to 90 degrees Celsius. The heat energy required is marked in figure 1 with the reference sign (E).

The fruit mass was heated for a total of 2.5 hours. The water can either be added at a temperature of 70 degrees Celsius or be heated up while it is being added. The hot diluted fruit mass was subsequently further diluted by adding 1500 g of water at a temperature of 90 degrees Celsius (18).

The fruit mass was then filtered off without the addition of diatomaceous earth (20). The resulting filter cake (SR) was kept for further extraction. The raw Filtrate was then passed through a diatomaceous earth filter and the pectin was subsequently precipitated by adding (31) the double amount of isopropanol 99%, relative to the clear Filtrate. The separated (35) wet pectin was then washed with isopropanol 70% and later filtered. The liquid obtained from the first separation and the washing liquid were further processed in a process step (40).

The precipitated and alcohol-washed pectin was slowly dried for one hour with air at a temperature of 70 degrees Celsius (45) and finally ground (50) to provide the product Pl specified in figure 1.

The filtrate obtained after precipitating the pectin was concentrated in a rotary evaporator (40) under simultaneous addition of energy (E) in order to separate it from the alcohol. The remaining aqueous residue was utilised for the second extraction of the filter cake. The distilled and recovered alcohol was used again as precipitation means in step (30).

The second acid hydrolysis (55) was carried out with the filter cake (SR), together with the returned aqueous residue (2200 g) (WR), by adding 200 g of hot water (56) and heating up the mixture to a temperature of 85 degrees Celsius in an extraction vessel. The temperature increase from 65 degrees Celsius to 85 degrees Celsius was gradual and took place over the period of one hour (E). The hot filter cake and water mixture was then maintained at 85 degrees Celsius for 3.5 hours. The filter cake and water mixture was subsequently further diluted with an additional 1000 g of water at a temperature of 85 degrees Celsius (57) under stirring. The filter cake and water mixture was finally filtered (60) without the addition of diatomaceous earth. The remaining solid (61) can be used in the production of opacifiers (cloudifiers) or, locally, as cattle feed supplement.

The second raw filtrate obtained previously was passed through a diatomaceous earth filter to produce a clear filtrate (65). The pectin was then precipitated by adding the double amount of isopropanol 99% (71) and, while still wet, washed with isopropanol 70% under stirring (mixer). The liquid obtained from the subsequent filtration step was further processed in step (80).

The separated pure pectin was slowly dried (85) for one hour using air circulation at a temperature of 70 degrees Celsius with the addition of energy (E) and finally ground (90) to provide the product P2 shown in the following table. The filtrate and the alcohol used for washing were concentrated in a rotary evaporator with the simultaneous addition of energy (E) to separate and recover the alcohol. The remaining aqueous residue (81 ) could be used afterwards for the production of citric acid. The recovered alcohol was re-used in the process for precipitating pectin (70).

Table

In the experiment described above the overall pectin yield to 100 SAG in a two-stage extraction process was 53.6 % plus 16.4 % = 70. 1 %. In processes according to prior art, pectin yields exceeding 50% to 100 SAG using citrus peels are regarded as good.

As already mentioned previously, bio-certified citrus oils can be obtained from bio-certified citrus fruit plantations, while bio-certificd pectin and bio-ccrtified opaci tiers can be obtained when bio-ccrti lied alcohol is used. In addition, bio-ccrtified citric acid and bio-certificd carotenes or carotene concentrates can be produced under the same conditions.

In another particular embodiment of this method, the peel, or the material obtained from grating the peel, is mixed with the citrus oil obtained from cooking the pulp, subsequently stirred at an elevated temperature in the presence of water, and, finally, decanted. A large part of the carotenes contained in the outer skin of the citrus peel is thereby transferred to the citrus oil and is subsequently either crystallised out by concentrating the citrus oil in a high vacuum rotary evaporator or used as concentrated, carotene-rich citrus oil concentrate. Citrus oil as an extraction and carrier substance has excellent oxidation protection characteristics for the carotenes, substantially increasing their stability. The intensive coloration of the carotenes in ripe citrus peels is commercially very interesting as a colouring agent for the food and drinks industry.

If citrus oil is to be the only side product, the cooking temperature is increased to approximately 100 degrees Celsius and the citrus oil is removed from the fruit juice through steam distillation. In laboratory and industrial experiments it was also found that a sufficient amount of pectin is also precipitated from the clear filtrate by adding citrus oil with or without the presence of solubilisers. The citrus oil used for the precipitation can subsequently be removed from the pectin by washing with alcohol and recovered after distilling the alcohol.

The indicated temperatures and heating times are exemplary and advantageous. Starting temperatures below 65 to 70 degrees Celsius result in a lower pectin yield. The same applies for an end temperature below 85 to 90 degrees Celsius. Higher temperatures require, in particular, a higher energy input and, with it, an adequate plant design. The hydrolysis can be earned out at a maximum temperature between 80 and 100 degrees Celsius and the corresponding heat-up time can be between 30 minutes and 2 hours. This approximate temperature is subsequently maintained for a time period of 2 to 4 hours.

It is another advantageous aspect of the present invention that, apart of the previously obtained oil and colour products, opacifϊcrs, citric acid (CA) and/or vitamin C are also obtained as side products, thus ensuring that the citrus fruit is completely utilised. Here, the citrus juice forms the direct basis for the acid utilised in the production of pectin.

In summary, it can be ascertained that by utilising the citrus fruit's own juice a complete utilisation of the fruit is achieved in the production of the following products.

- Cold-pressed citrus oil

- Steam-distilled citrus oil

- Pure carotenes, carotene concentrates

- Pure pectin in high yield

- Opacifiers (cloudifiers)

- Animal feed

- Concentrated citrus juice

- Citric acid.

Abovementioned products can be produced in a bio-certified manner by using bio-certified fruits and bio-certified ethyl alcohol.

The method according to the present invention provides substantial cost savings because the raw material (peel) can be utilised locally, without prior drying, also in the case of small and medium-sized citrus producers. The raw material is processed in its fresh form directly after the harvest, thus providing hygienically faultless, mycotoxin-free products with greatly reduced losses. In addition, as henceforth saleable pure products are transported, rather than ballast-rich raw products, the transport costs are reduced by the equivalent amount. Local manpower costs are considerably lower than in the consumer or developed countries.

The typically high energy costs seen in developed countries are in stark contrast to the only marginal local energy costs, thanks to the availability of sufficient waste heat from agricultural drying and from the wood obtained from citrus trees, to meet the entire process heat requirements. The method according to the present invention also provides a way to include small and medium-sized citrus fruit production plants in the pectin market. These production plants could previously not be integrated in a cost-effective manner due to their size and/or the distance to the pectin-producing industries. .

Claims

Patent Claims

1. A method for the production of pectin from citrus fruits comprising the following steps

- Production of a raw material (10) containing citrus fruit components

- Conducting an acid hydrolysis (15,20)

- Extracting a pectin (25, 30, 35) characterised in that the acid hydrolysis (15,20) is conducted in the own citrus juice and/or in the own citrus oil, with additional citrus juice and/or citric acid being optionally added.

2. A method as claimed in claim 1 in which the raw material production step comprises the production of a crushed fruit mass using parts of the fruit or the whole fruit and/or the pectin extraction step comprising the following sub-steps:

- addition of a precipitating means and precipitation of the pectin,

- filtering and washing of the precipitated pectin, and

- the optional extraction of side products,

3. A method as claimed in claim 1 or 2 in which in a further processing step the grated citrus peel is obtained, in case of citrus oil being extracted from citrus peel.

4. A method as claimed in one of the claims 1 to 3, characterised in that the pectin precipitating means is ethanol or isopropanol or, in particular, bio-certified ethanol.

5. A method as claimed in one of the claims 1 to 4, characterised in that the liquids obtained after the filtration of the pure pectin and after washing the pectin are separated from precipitating means or alcohol in a distiller and said precipitating means or alcohol is returned into the process as a means for further precipitating of pectins.

6. A method as claimed in one of the claims 1 to 5, characterised in that the aqueous liquid obtained in the first extraction, being rich in citric acid which remains after separating the precipitating means or alcohol, is mixed again with the filter cake remaining after the raw filtration to conduct the second extraction of the remaining pectins.

7. A method as claimed in one of the claims 1 to 6, characterised in that the obtained filter cake is extracted at least one time to five times, preferably two consecutive times, with the respectively recovered, citric acid rich and alcohol-free aqueous liquid.

8. A method as claimed in one of the claims 1 to 7, characterised in that the volume of the water added to the fruit mass is between one quarter and ten times the volume of the raw material, preferably between one third and three thirds of that of the raw material.

9. A method as claimed in claim 8, characterised in that the temperature of the added water is between 40 degrees Celsius and 100 degrees Celsius, preferably between 60 degrees Celsius and 70 degrees Celsius.

10. A method as claimed in one of the claims 1 to 9, characterised in that, after adding and mixing the water, the fruit mass temperature is maintained between 40 degrees Celsius and 140 degrees Celsius, preferably between 80 degrees Celsius and 110 degrees Celsius, and, in particular, between 85 degrees Celsius and 95 degrees Celsius.

11. A method as claimed in one of the claims 1 to 10, characterised in that, after adding and mixing the first amount of water to the fruit mass, the temperature is maintained between 85 degrees Celsius and 95 degrees Celsius during a time period of 30 minutes to 10 hours, preferably between 30 minutes and 5 hours, and, in particular, between 2 hours and 2.5 hours.

12. A method as claimed in one of the claims 1 to 11, characterised in that after completing the cooking period further diluting water (one third to three thirds of the raw mass) at the same temperature is added under stirring of the already cooked fruit mass.

13. A method as claimed in one of the claims 1 to 12, characterised in that the amount of fresh water added to the filter cake obtained in the first extraction is between 10% and 30% of the returned residual water remaining after separation of the precipitating means or alcohol.

14. A method as claimed in one of the claims 1 to 13, characterised in that the temperature of the fresh water added in the second extraction is between 40 degrees Celsius and 100 degrees Celsius, preferably between 80 degrees Celsius and 85 degrees Celsius.

15. A method as claimed in one of the claims 1 to 14, characterised in that filter cake mass diluted and heated up for the second extraction step is maintained at a temperature between 40 degrees Celsius and 140 degrees Celsius, preferably between 80 degrees Celsius and 110 degrees Celsius, and, in particular, between 80 degrees Celsius and 85 degrees Celsius.

16. A method as claimed in claims 15, characterised in that, after adding and mixing the diluting water to the filter cake mass in the second extraction step, the temperature is maintained between 80 degrees Celsius and 85 degrees Celsius during a time period of 30 minutes to 10 hours, preferably between 30 minutes and 5 hours, and, in particular, between 3 hours and 3.5 hours.

17. A method as claimed in one of the claims 1 to 16, characterised in that the cooked fruit mass from the first and from the second extraction steps is transformed into a so-called raw extract by means of centrifuges or filters.

18. A method as claimed in one of the claims 1 to 17, characterised in that the raw filtrate obtained from the two extractions is converted into a transparent, so called clear filtrate, by means of a polishing filter or a polishing centrifuge, in the case of filtration using filtering aids, such as diatomaceous earth.

19. A method as claimed in claims 1 to 18, characterized in that bio-certified fruits are used for the production.

20. Cold-pressed, bio-certifiable citrus oil produced in accordance with a method as claimed in one of the claims 1 to 19.

21. Steam-distilled, bio-certifiable citrus oil produced in accordance with, a method as claimed in one of the claims 1 to 19.

22. Bio-certifiable carotenes produced in accordance with a method as claimed in one of the claims 1 to 19.

23. Bio-certifiable, citrus oil based carotene concentrate produced in accordance with a method as claimed in one of the claims 1 to 19.

24. Bio-pectin produced in accordance with a method as claimed in one of the claims 1 to 19, characterised in that it is produced using bio-certified citrus fruits and bio-certified precipitating means.

25. Bio-pectin produced in accordance with a method as claimed in one of the claims 1 to 19, characterised in that bio-certified citrus oil, with or without the simultaneous use of bio-certified solubilisers, is used as precipitating means.

26. Bio-certifiable citric acid produced in accordance with a method as claimed in one of the claims 1 to 19, characterised in that it is obtained using bio-certified citrus fruits and bio-certified precipitating means from the precipitating means-free aqueous liquid remaining after the second extraction step.

27. Bio-certifiable opacifier produced in accordance with a method as claimed in one of the claims 1 to 19, characterised in that it is obtained using bio-certified citrus fruits and bio-certified precipitating means from the solids remaining after the second extraction step.

28. Bio-certifiable animal feed supplements produced in accordance with a method as claimed in one of the claims 1 to 19, characterised in that it is obtained using bio-certified citrus fruits and bio-certified precipitating means from the solids remaining after the second extraction step.

29. Bio-certifiable, concentrated citrus juice pulp with controlled citrus oil, pectin and citric acid content, as well as a specified concentration, produced in accordance with a method as claimed in one of the claims 1 to 19.