MXPA00000116A - Fruit juice clarification - Google Patents

Abstract

The present invention relates to clear fruit juices and to a process for the production thereof. A fast process is provided that comprises the combined use of pectin esterase and flotation.

Description

CLARIFICATION OF FRUIT JUICES FIELD OF THE INVENTION The present invention relates to substantially transparent fruit juices and to a process for preparing said transparent fruit juices.

BACKGROUND OF THE INVENTION The elaboration of fruit juices typically comprises the squeezing of the fruit followed by the elimination of the pulp and the centrifugation. The juice without pulp is pasteurized as soon as possible after the elimination of the pulp, in order to prevent oxidation. The juice thus obtained can be clarified with sulfur dioxide (S02), clarifying agents or enzymes before pasteurization, solids removal, and concentration. Fruit juices, and in particular citrus fruit juices, are very difficult to clarify, due to their high acidity. After the extraction of the juice and pasteurization, turbid citrus juices are usually stored at 2-15 ° C for months, so that they can be clarified slowly, before REF .: 32448 of further processing. The temperature must be kept low to prevent oxidation reactions in the juice. Two other factors that complicate the clarification of citrus fruit juice are the presence of protein and pectin. A conventional method for the clarification of juice is the addition of S02 as a clarifying agent. However, this may result in high concentrations of S0, undesirable in the juice. Although this can be resolved by desulphurization, some S02 remaining in the juice will remain. In addition, juice manufacturers must invest in large storage capacities, since the juice has to be stored for a fairly long time. Another conventional method for clarifying juices is the addition of pectinases after squeezing, pulp removal and pasteurization. The dose used is generally rather high, and the clarification takes several hours, sometimes up to days, depending on the temperature. The juice can then be clarified with bentonite or silica sol and filtered on a soil filter and / or an ultrafilter. This process also consumes time and can result in a rather high waste production.

U.S. Patent No. 4,624,980 discloses a process of continuous clarification of fruit juices, comprising the addition of coagulants that form a flock with the solid particles of the juice. These can then be separated by introducing a non-deleterious gas in the form of microbubbles that make it. the flocculated particles float to the surface of the juice. Le Quere et al. (Industries Alimentarles et Agricoles, 105, 137-139, 1988) discloses a method for specifically clarifying apple cider that previously involves fermentation, a step of pectin demethylation using. Pectin esterase for 66 - 72 hours, subsequent addition of CaCl2 solution and nitrogen gas and flotation of the pectin gel formed accordingly. U.S. Patent No. 1,535,983 discloses a method for clarifying lemon juices, and comprises the addition of a combination of polygalacturonase and pectin esterase, in order to completely eliminate the pectin, in combination with colloidal silica. Similarly, U.S. Patent No. 4,211,799 discloses a method for making citrus juice resistant to flocculation during storage, by treating naturally turbid citrus juices having a pH below 2.5, with a pectinase of the polygalacturonase / pectinaestiarase type, at a temperature below 30 ° C until the alcohol test for pectin is negative, then decanting the supernatant juice resistant to flocculation after resting. Therefore, there is still a need for a rapid process for the clarification of fruit juices in general, and in particular for the clarification of citrus fruit juices. Surprisingly we have discovered that rapid clarification of fruit juices can be achieved by applying a pectin esterase treatment for 0.5 - 48 hours in combination with a flotation technique.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a process for the preparation of fruit juices substantially transparent, from the corresponding fruit, with a turbidity of less than 300 NTUS, which comprises the following steps: I. Extraction of the liquid part of the fruit and pulp elimination and optional pasteurization of the liquid part; II. Incubation of the liquid part of the fruit, between 0.5 and 48 hours, with an enzymatic preparation containing pectin esterase and optionally calcium ions; III. Transfer of the liquid part of the fruit treated enzymatically to a flotation tank followed by pressurization; IV. Release of the pressure, allowing the solid particles of the liquid part of the enzymatically treated fruit to float to the surface, followed by the elimination of the insoluble particles; and V. Recovery of substantially transparent fruit juice. In another aspect, the invention relates to clarifying fruit juices with a turbidity of less than 300 NTUS.

In another aspect, the invention relates to the use of pectin esterase, in combination with a flotation technique for the preparation of substantially transparent fruit juices.

DETAILED DESCRIPTION OF THE INVENTION The present invention solves the problem of how to clarify fruit juices, more particularly how to clarify citrus fruit juices. According to the present invention the problem can be solved by a simple process comprising the use of a treatment with pectin estearase and flotation. This process is faster than conventional processes. This process involves obtaining the liquid part of the fruit, mechanically, enzymatically or by a combination of both methods. Next, after pulp removal and optional pasteurization, the pectin esterase is added to the liquid part of the fruit. The pectin esterase used is preferably free of activities of pectin polymers, such as a pectin lyase (PL) and polygalacturonase.

(PG), is resistant to high acidity (pH less than 2) and active at low temperatures (10 ° C-50 ° C). Pectin esterase treatment takes a relatively short period of time compared to conventional fruit juice clarification processes. The pectin esterase treatment lasts 0.5-48 hours, preferably 0.5-24 hours and more preferably 1-5 hours. Treatment times vary "depending on the amount of pectin esterase used and the temperature.The pectin esterase dosage may vary between 100-100,000, more preferably between 1,000-50,000 and more preferably between 1,000-15,000 units of pectin esterase. The temperature can be chosen between 0 and 45 ° C, preferably between 0 and 35 ° C and, more preferably between 2 and 20 ° C. Then the liquid part of the enzymatically treated fruit is subjected to flotation in order to Then, the juice is introduced into the flotation tank in a pressurized state.The pressure conditions are 2-10 bars, preferably 2-7 bars and more preferably 4-7 bars and are applied for 1 hour. -120 minutes, preferably 2-120 minutes and more preferably 2-60 minutes.After this time, the pressure is released, causing the juice particles to float and separate from the rest of the juice Optionally, during the flotation calcium can be added, for example, as calcium chloride. Preferred concentrations of calcium chloride are in the range 1-500, more preferably 10-500 and more preferably 10-200 grams per hectolitre. The turbidity of the substantially transparent fruit juices obtained by the present invention can be determined by various methods. The most common method is to express turbidity in Nephelometric Turbidity Units (NTU?). The substantially transparent fruit juices obtained by the present invention have a turbidity of less than 300 NTU, preferably less than 200 NTU, and more preferably less than 100 NTU. With another method, the filterability of substantially transparent fruit juices is determined by filtering these juices through filter paper and measuring the amount of filtering as a function of time. The lower the turbidity of the substantially transparent fruit juice, the greater the amount of filtering per unit of time. Similarly, the ultrafiltration capacity (UF) of substantially transparent fruit juices can be determined by filtering these juices through ultrafilters and measuring the amount of ultrafiltrate as a function of time. The lower the turbidity of the substantially transparent fruit juice, the greater the amount of filtering per unit of time.

Materials and Methods: Pectin esterase. It can come from any source, such as microorganisms or plants. The pectin estearase suitable for use according to the present invention is stable in the medium of fruit juice and retains its activity during juice processing. Because. the desired enzymatic characteristics, the pectin esterase is preferentially derived from a fungus. More preferably it comes from Aspergi l l us, especially from Aspergi l l us ni ni ger. The crude pectin esterase, obtained from a culture medium, can be purified in a number of ways. Preferably, the purification results in a product substantially free of. depolymerizing activities, such as, for example, polygalacturonase and pectin lyase. The crude enzyme can be purified by, for example, liquid chromatography (ion exchange, gel filtration, affinity) (Ishii et al., 1980, U.S. Patent No. 4,200,694) or by selective inhibition of polymerizing activities (e.g. , by abrupt change of pH, abrupt temperature change, chemical inhibitors, or chemical extraction or with organic solvents (Smythe C. et al., 1952, U.S. Patent No. 2,599,531) Another source of obtaining purified pectin esterase is is defined in the present application, pectin esterase is obtained by DNA recombination technology, an example is the cloned expression of the pectin esterase of Aspergi llus niger for which the sequence cDNA has been determined (Khanh et al., 1990 , Nucí, Acids Res 18, 4262) As the expression host, the Aspergi llus ni ger may be used, however, considering the possible contamination of pectin esterase. On polygalacturonase, pectin lyase and other depolymerizing activities it may be preferable to use a heterologous host organism to produce the pectin esterase. Host organisms comprise bacteria and fungi. The preferred species would be Ba ci l os, Es ch eri chi a, Sa ccha romyces, Kl uyveromyces and Aspergi l l i.

RAPIDASE CLEAR LEMON® is a commercially available product from the Beverage Ingredients Group of DSM Food Specialties (Seclin, France) and contains a pectinase preparation of Aspergi llus niger, with pectin esterase, polygalacturonase, pectin lyase and arabinase as the main activities .

Table 1: Properties of the enzymatic preparations.

Pectin estease test activity A PF unit is defined as the amount of enzyme that hydrolyzes a microequivalent per minute of carboxy methyl groups at 30 ° C and pH 4.5. The substrate is an aqueous solution of 0.5% apple pectin (Ruban Brun) with a degree of methylation > 70% One unit PE = 0.98 International Units PE.

Pectin lyase activity assay (PL) A PL unit is defined as the amount of enzyme that produces a micromol of Uranic product? 4.5 unsaturated in one minute. The extinction coefficient at 235 nm is 5.55 x 103 M'Xc 'X The reaction is carried out at 45 ° C and at pH 5.5 and the substrate is an aqueous solution of submethylated pectin at 1% (W / V). The optical density, measured at 235 nm, is read after a reaction time of 10 minutes. .

Assay of endo-polygalacturonase activity. One unit (PG) is defined as the amount of enzyme in 1 ml of enzyme solution that decreases the viscosity of the substrate at a rate that has an apparent rate constant of 0.0053 per minute at 45 ° C and at pH 4.5. The substitute is an aqueous solution of 0.5% sodium polygalacturonate. The reaction conditions for the tests described above are for these tests. The enzyme is added to the assay medium consisting of the indicated substrate solution buffered to the desired pH. The exploitation was carried out in a flotation tank with a pressurization equipment with a laboratory float of 2 liters capacity (type TMCI Padovan).

The turbidity of the juices are expressed in nephelometric turbidity units (NTUs) measured at atmospheric pressure. The method is based on infrared absorbance measurements of particles with a diameter >; 2 microns. The filterability of the clarified juices was measured at atmospheric pressure using Prat Dumas No. 2 filter papers in a funnel mounted on the top of a calibrated flask. . The ultrafiltration capacity (UF) of the juices was measured using Ultrafree Millipore devices equipped with poly isul phonade membranes with a cut point of 30 kDalton. The weight of the filtrate was measured after centrifugation for 1.5 hours at 2.500 g and at 20 ° C. In the example given below, the effect of the combination of pectin esterase treatment and flotation for the production of a transparent lemon juice will be demonstrated.

EXAMPLE 1 Production of transparent lemon juice. The lemon juice was prepared with a citrus press Philips Citrus - 1,000 (40% yield) = the weight of the liquid part of the fruit / total weight of the fruit and then sieved with a sieve of 0.5 mm. The turbidity of the juice was 580 NTU. The juice was divided into 4 parts of 250 ml each for the tests as indicated in Table 2.

The beakers containing the juice were placed in a water bath at 35 ° C and allowed to reach equilibrium temperature, after adding the other components as indicated in Table 2 the mixture was stirred and kept at 35 ° C. ° C for 5 hours. The juices were then kept under pressurization with stirring for 2 minutes at 6 bars. The pressurization was stopped and the juice was poured into 500 ml beakers in order to allow the insoluble particles to float to the surface.

The insoluble pectate clots were removed with a spatula from the surface of the juice. The following analyzes were then carried out: 1. Turbidity of the juice obtained after the enzymatic treatment and flotation, and elimination of the pectate clots (expressed in NTU). 2. Filterability of the juice with filter papers. 3. Turbidity of the juice filtered by paper (expressed in NTU). 4. Filtration by ultrafiltration using Ultrafree Millipore devices. These analyzes were carried out one hour after obtaining the juices from the enzymatic and flotation treatment, and they were repeated 3 hours later. Table 1 shows that in the incubations comprising purified pectin esterase (tests 1 and 2), much more pectate clot is formed compared to the incubations with RAPIDASE CLEAR LEMON® (tests 3 and 4). Also, the juices obtained from tests 1 and 2 are much more transparent (Table 1 - column 3) compared to the juices of tests 3 and 4, the last being as turbid as the juice without treatment (580 NTU). The turbidity measured after 3 hours shows the same trend (Table 1 column 11). Filterability in paper filters, expressed as the volume (ml) of filtrate collected at certain times, was also much higher in tests 1 and 2 of the juices, compared to the juices of tests 3 and 4, both 1 and 3 hours after the enzymatic and exploitation treatment (Table 1 column 4 - 8 and 12 respectively). Also the turbidity of the filtrates was much lower than in the case of tests 1 and 2 compared to tests 3 and 4 (Table 1 - columns 9 and 13). The filtration measured by ultracentrifugation using Ultrefree Millipore devices was also much greater for the juices of tests 1 and 2 compared to those of tests 3 and 4 (Table 1 - columns 10 and 14).

Cp O p Cp TABLE 3 Results The luridity of the filtrate is expressed in NTU. The filterability is expressed in milliliters of liquid collected after the filtration time indicated c Ultraflix collected after the ultrafiltration of 2.5 ml of juice.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (16)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A process for the production of substantially transparent fruit juices from the corresponding fruits, with a turbidity of less than 300 NTUS, characterized in that it comprises the following steps: i. Extraction of the fluid part of the fruit and elimination of the pulp and optional pasteurization of the liquid part; ii. Incubation of the liquid part of the juice between 0.5 and 48 hours, with an enzymatic preparation containing pectin esterase and optionally calcium ions; iii. Transfer of the liquid part of the fruit treated enzymatically to a flotation tank followed by pressurization; iv. Release of the pressure, allowing the solid particles of the liquid part of the enzymatically treated fruit to float to the surface, followed by elimination of the insoluble particles; and V . Recovery of substantially transparent fruit juice.

2. The process according to claim 1, characterized in that the liquid part of the fruit is extracted mechanically, enzymatically or by a combination thereof

3. The process according to claims 1-2, characterized in that the pectin esterase is added in final concentrations of 100 10,000 units of pectin estearase per hectoliter of the liquid part of the fruit.

4. The process according to claims 1-3, characterized in that the calcium ions are added as calcium chloride in a final concentration of 1-500 grams per hectolitre.

5. The process according to claims 1-4, characterized in that the temperature is maintained between 0-45 ° C.

6. The process according to claims 1-5, characterized in that the pressurization is carried out at 2-10 bars.

7. The process according to claims 1-6, characterized in that the pressurization is carried out for 1-120 minutes.

8. The process according to claims 1-7 for the production of fruit juices, characterized in that they have a turbidity of less than 200 NTU.

9. A process according to claim 8, characterized in that the fruit is a citrus fruit.

10. A process according to claim 9, characterized in that the citrus fruit is lemon.

11. Transparent fruit juices characterized because they have a turbidity of less than 300 NTU.

12. Transparent fruit juices according to claim 11, characterized in that the fruit is a citrus fruit.

13. Transparent citrus fruit juices according to claim 12, characterized in that the citrus fruit is lemon.

14. The production of transparent fruit juices according to claims 11-13, characterized in that pectin esterase is used in combination with a flotation technique.

15. The use according to claim 14, characterized in that the fruit is a citrus fruit.

16. Use according to claim 15, characterized in that the citrus fruit is lemon.