A pulsed electric field treatment method for vegetable or fruit objects

Abstract

The present invention describes a method comprising - providing one or more fruit objects or vegetable objects; - adding a fruit juice or vegetable juice, where this is the aqueous solution or liquid needed for the pulsed electric field (PEF) treatment according to below, to said one or more fruit objects or vegetable objects, for providing a medium comprising said one or more fruit objects or vegetable objects in a fruit juice or vegetable juice; and - exposing said one or more fruit objects or vegetable objects in the fruit juice or vegetable juice to a pulsed electric field (PEF) treatment.

Description

[0001] A PULSED ELECTRIC FIELD TREATMENT METHOD FOR VEGETABLE OR FRUIT OBJECTS

[0002] Field of the invention

[0003] The present invention relates to a pulsed electric field (PEF) treatment method for vegetable or fruit objects.

[0004] Technical Background

[0005] It has long been known to use pulsed electric field to treat foodstuffs, such as potato-based objects.

[0006] The method according to the present invention is directed to an improved pulsed electric field method intended for fruit or vegetable objects.

[0007] Summary of the invention

[0008] The stated purpose above is achieved by a method comprising

[0009] - providing one or more fruit objects or vegetable objects;

[0010] - adding a fruit juice or vegetable juice, where this is the aqueous solution or liquid needed for the pulsed electric field (PEF) treatment according to below, to said one or more fruit objects or vegetable objects, for providing a medium comprising said one or more fruit objects or vegetable objects in a fruit juice or vegetable juice; and

[0011] - exposing said one or more fruit objects or vegetable objects in the fruit juice or vegetable juice to a pulsed electric field (PEF) treatment.

[0012] In relation to the statement “adding a fruit juice or vegetable juice to said one or more fruit objects”, this implies an active step of combining a flow or batch of a fruit or vegetable juice to a flow or batch or fruit or vegetable objects. It does, however, not imply treating fruit or vegetable pulp as such, and then extracting juice from such a stream. The method according to the present invention implies that the fruit or vegetable objects are held I immersed in a juice (liquid) when being PEF treated. This also means that juice (liquid) is the treatment medium , and where the fruits or vegetables objects are immersed during the PEF treatment. This method according to the present invention has been proven to be an efficient way of obtaining improved results for the material as such after the treatment, and also for higher efficiency in post-treatment. One such example is that a PEF step according to the present invention softens up the material and significantly decreases the drying time. This and other benefits will be explained more in the description below.

[0013] Specific embodiments of the invention

[0014] Below some specific embodiments of the present invention are presented and discussed further.

[0015] According to one embodiment, the fruit juice or vegetable juice is from the same origin as said one or more fruit objects or vegetable objects so that the medium comprises one or more fruit objects or vegetable objects and a corresponding juice. This alternative is one interesting embodiment according to the present invention; however, it should be clear that also using a different type of fruit or vegetable juice for a certain fruit or vegetable type is totally possible according to the present invention.

[0016] Also, the PEF treatment step may involve considering optimizing certain parameters. According to one embodiment, the step of exposing one or more fruit objects or vegetable objects to pulsed electric field (PEF) treatment is performed with a protocol providing an electric field strength of 0.5 - 3.0 kV / cm, preferably in a range of 0.5 - 2.0 kV / cm. This range of the electric field strength is optimized and suitable according to the present invention as the treatment is performed in a fruit juice or vegetable juice. Here the conductivity has a role. Moreover, the treatment in an added fruit juice or vegetable juice also plays a role in maintaining the %Brix levels as further proven below. Also other parameters mentioned below have an effect in this regard.

[0017] Furthermore, according to one embodiment, the pulsed electric field (PEF) treatment is performed in a voltage range of 6 - 12 kV. According to one embodiment, the pulsed electric field (PEF) treatment is performed with a frequency of pulses in a range of 40 - 100 Hz. According to yet another embodiment, the pulsed electric field (PEF) treatment is performed in in a pulse width in a range of 2 - 10 pS, and preferably the resulting energy density is in a range of 3 - 20 kJ / kg, more preferably 2 - 12 kJ / kg.

[0018] Another benefit of the method according to the present invention relates to increased efficiency in possible post-processing of the material. One such is in a possible subsequent drying step. In line with this, according to one embodiment of the present invention, the method comprises a subsequent step of drying of said one or more fruit objects or vegetable objects after the pulsed electric field (PEF) treatment and after being removed from the fruit / vegetable juice. One advantage of the method according to the present invention is that this drying step can be performed during a relatively speaking shorter time when compared with drying of a non-treated material. The normal drying time when a material is not treated such as according to the present invention is 10-11 hours. However, when the PEF method according to the present invention is implemented, then the drying time may be decreased to 7-8 hours, all other parameters similar.

[0019] Furthermore, according to yet another embodiment, pulsed electric field (PEF) treatment is performed on pineapple slices, chucks or tidbits in a medium comprising the pineapple slices, chucks or tidbits in added pineapple juice.

[0020] The present invention is also directed to use of a method according to the present invention, for

[0021] - softening of said one or more fruit objects or vegetable objects; -maintaining the sugar concentrations in the fresh fruit objects wherein there was an insignificant reduction in % Brix;

[0022] - shortening the drying time in a subsequent drying step in comparison to a non-treated material, when dried to the same moisture level, preferably with at least 15% reduction of the drying time, more preferably at least 20% reduction of the drying time, such as even above 25% reduction of the drying time;

[0023] - providing treated and dried fruit objects or vegetable objects exhibiting a uniform moisture content; and / or

[0024] - providing treated and dried fruit objects or vegetable objects exhibiting a reduced hardness attribute. Preferably, the method according to the present invention provides for several of the possible intended uses mentioned above in one technical application.

[0025] The present invention also refers to a quantity of the same type of fruit objects or vegetable objects in a dried format, which exhibits below 5%, such as even below 4% or 3%, variation of the moisture content in the dried fruit objects or vegetable objects when compared in the amount of the same type of fruit objects or vegetable objects, where there was over 8% moisture content variation in the amount of the same type of untreated fruit objects or vegetable objects. It should be noted that the expression “in a dried format” implies that the objects have been dried in a preceding step.

[0026] According to the present invention, the PEF treatment “promotes” an even water distribution in the matrix of the fruit and vegetable object. During drying, the water is evenly “evaporated”. On the untreated fruit and vegetable objects, water is randomly distributed resulting in an uneven moisture content or distribution in a final production after drying.

[0027] According to yet another embodiment of the present invention, there is disclosed fruit or vegetable objects obtainable by a method according to the present invention also including a drying step, wherein said fruit objects or vegetable objects

[0028] - exhibit below 5% variation of the moisture content in the dried fruit objects or vegetable objects when compared in a group of same type of fruit objects or vegetable objects; and

[0029] - have an improved texture in terms of reduced hardness as exhibited by a reduction in tested cut force of at least 15%, preferably at least 20%, more preferably at least 25%.

[0030] It should be noted that also other steps may be combined with the PEF treatment step. One such step is vacuum impregnation. Therefore, according to one embodiment the method also comprises performing vacuum injection of the fruit juice or vegetable juice into said one or more fruit objects or vegetable objects. Examples and description of drawings

[0031] Material

[0032] Pineapple chucks, slices and titbits, especially from Thailand, and early harvested or green plants are often deemed as hard and whitish by the end customers even after the ‘short cooking’ for microbial and enzymatic deactivation in a bid to enhance its shelf life. Softening pineapple chucks or tidbits before canning or before ‘cooking’ will be a most welcome development for better organoleptic attributes such as color, taste, and visual appearance.

[0033] Method and experimental protocol

[0034] In accordance with one embodiment of the present invention the following experimental protocol was used.

[0035] Pulsed electric field (PEF) treatment was used in accordance with the present invention. The PEF treatment was performed in pineapple juice, being the treatment liquid. The PEF protocol entailed applying a voltage of 6 to 12 kV giving an electric field strength of 0.5 to 3.0 kV / cm. The frequency of the pulses ranged from 40 to 100 Hz while the pulse width ranged from 2 to 10 pS.

[0036] Results

[0037] In fig. 1 the result of the PEF treatment is shown. Here, the hardness is measured by measuring compression force with the aid of texture analyzer (TA-XT2, Stable Micro Systems) when comparing PEF treatment with nontreated control. As can be seen, the PEF treatment led to over 12% decrease in hardness, i.e. an increase in softness, in the first hour, and over 49% change in 24 hours.

[0038] In table 1 below there are presented the results of a series of trials performed in accordance with the present invention. The material tested was pineapple pieces. The PEF parameters varied in accordance with the present invention as described above. The PEF treatment according to the present invention implies treatment of the pineapple pieces in pineapple juice.

[0039] Moreover, after the PEF treatment, the material was dried in a hot air dryer at 65°C. The control below presents a material which is not PEF treated according to the present invention, and which is instead dried directly.

[0040] Table 1 : Freeh fruit characteristics (%Brix), drying time and dried fruits characteristics (hardness and moisture variance)

[0041] *PEF treated dried fruits significantly softer than untreated

[0042] **Moisture content consistency in the dried fruit. PEF shows minimal variation

[0043] As may be seen, the material treated according to the present invention, where the method also included a drying step, exhibited maintained sugar concentrations in the fresh fruit objects as there was an insignificant reduction in % Brix. Moreover, the treated material also exhibited an improved texture with reduced hardness as exhibited by a reduction in tested cut force of (1 - 1982 / 2603) = 0.238, i.e. 24% in average. Moreover, as notable, the drying time used was reduced from 11 .3 to 8.3 hours in average. Furthermore, it may also be noted that the moisture content variance in the material being PEF treated according to the present invention, and then dried, was only 2.5 % on average, which may be compared with 8.0% in average for the control material after drying.

[0044] Furthermore, it may be noted that the texture is determined by measuring “cut force” in newton (N). This is measured using a texture analyzer where a probe or a blade cut / shear through the fruit or vegetable object, under specified conditions. The maximum force required and / or the work necessary to achieve this (i.e. the area under the curve) is taken as an index of firmness, toughness or hardness of the fruit or vegetable object.

Claims

Claims1 . A method comprising- providing one or more fruit objects or vegetable objects;- adding a fruit juice or vegetable juice to said one or more fruit objects or vegetable objects, for providing a medium comprising said one or more fruit objects or vegetable objects in a fruit juice or vegetable juice; and- exposing said one or more fruit objects or vegetable objects in the fruit juice or vegetable juice to a pulsed electric field (PEF) treatment.

2. The method according to claim 1 , wherein the fruit juice or vegetable juice is from the same origin as said one or more fruit objects or vegetable objects so that the medium comprises one or more fruit objects or vegetable objects and a corresponding juice.

3. The method according to claim 1 or 2, wherein the pulsed electric field (PEF) treatment is performed in a protocol providing an electric field strength of 0.5 - 3.0 kV / cm.

4. The method according to any of claims 1-3, wherein the pulsed electric field (PEF) treatment is performed in a voltage range of 6 - 12 kV.

5. The method according to any of claims 1-4, wherein the pulsed electric field (PEF) treatment is performed with a frequency of pulses in a range of 40- 100 Hz.

6. The method according to any of claims 1-5, wherein the pulsed electric field (PEF) treatment is performed in in a pulse width in a range of 2 - 10 pS.

7. The method according to any of claims 1-6, wherein the method comprises a subsequent step of drying of said one or more fruit objects or vegetableobjects after the pulsed electric field (PEF) treatment and after being removed from the fruit / vegetable juice.

8. The method according to any of claims 1-7, wherein pulsed electric field (PEF) treatment is performed on pineapple slices, chucks or tidbits in a medium comprising the pineapple slices, chucks or tidbits in added pineapple juice.

9. Use of a method according to any of claims 1-8, for- softening of said one or more fruit objects or vegetable objects;-maintaining the sugar concentrations in the fresh fruit objects wherein there was an insignificant reduction in % Brix;- shortening the drying time in a subsequent drying step in comparison to a non-treated material, when dried to the same moisture level, preferably with at least 15% reduction of the drying time, more preferably at least 20% reduction of the drying time;- providing treated and dried fruit objects or vegetable objects exhibiting a uniform moisture content; and / or- providing treated and dried fruit objects or vegetable objects exhibiting a reduced hardness attribute.

10. A quantity of the same type of fruit objects or vegetable objects in a dried format, which exhibits below 5% variation of the moisture content in the dried fruit objects or vegetable objects when compared in the amount of the same type of fruit objects or vegetable objects.11 . Fruit objects or vegetable objects obtainable by a method according to any of claims 1-8, wherein said fruit objects or vegetable objects, after a drying step,- exhibit below 5% variation of the moisture content in the dried fruit objects or vegetable objects when compared in a group of same type of fruit objects or vegetable objects; and- have an improved texture in terms of reduced hardness as exhibited by a reduction in tested cut force of at least 15%, preferably at least 20%, more preferably at least 25%.

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