Patent Description:
Production, starting from freshly squeezed orange juice (often referred to as raw orange juice), of an orange juice product that has a natural flavor while at the same time maximizing the shelf life of the orange juice product and minimizing the negative effects on orange juice quality due to pasteurization requires a number of processing steps. In prior art production methods and systems, membrane filtration technology and pasteurization have been used to remove prolong shelf life. <CIT> discloses for instance such a system comprising a heat exchanger, a ceramic filter with a pore size of <NUM>-<NUM> micrometers, an ultrafilter with a pore size of <NUM>-<NUM> configured to ultrafiltrate the cooled raw orange juice to produce a permeate and a retentate, a pasteurizer configured to pasteurize the retentate, a mixing unit configured to mix the permeate and the pasteurized retentate.

<CIT> discloses a system comprising a heat exchanger, a microfilter membrane, an ultrafilter membrane and a pasteurisation unit to pasteurize the retentate and a step of recombining the retentate with the permeate.

<CIT> discloses a membrane filtration system with a high pressure process or a heating process to remove or inactivate spoilage causing micro-organisms from the food, and an aseptic packaging unit.

<CIT> discloses an ultrafiltration membrane system combined with a heat exchanger, said membrane having a MWCO of <NUM>-100kDa, and further comprising a pasteurizer to inactivate enzymes and treat orange juices.

However, prior art solutions are typically only focused on a single part of the production process. No prior art solution has presented an orange juice product that has a natural flavor that resembles that of freshly pressed orange juice, while at the same time having a shelf life that is similar to the shelf life of pasteurized orange juice.

In view of the above, an object of the present disclosure is to improve prior art techniques for producing orange juice having a taste and quality that resembles freshly squeezed juice, while still providing a longer shelf life than freshly squeezed juice.

This object is achieved in a first aspect by a method for producing orange juice by only one membrane filtering. The method comprises cooling raw orange juice. The cooled raw orange juice is ultrafiltrated by a ceramic type ultrafilter having a membrane with a pore size of <NUM>-<NUM> and a channel size of <NUM>-<NUM> to produce a permeate and a retentate. The retentate is pasteurized and then mixed with the permeate to produce orange juice having an enzyme pectin esterase (PEU) content that is less than <NUM> % of the PEU content of the raw orange juice. Packets are aseptically filled with the orange juice produced by the mixing.

By ultrafiltrating the raw orange juice and thereby obtain a retentate and a permeate followed by pasteurizing only the retentate, a minimization of enzymes and microorganisms that are detrimental to the quality of the orange juice is obtained in the orange juice after mixing. By not pasteurizing the permeate, the flavor and aroma components which have smaller molecular size will pass through membrane and retain in the permeate, therefore permeate will retain natural flavor and the freshness of freshly squeezed orange juice. This is advantageous in relation to prior art processing of orange juice, which typically involves direct pasteurization of raw orange juice. The present method according to the first aspect has an effect on the minimizing the heat load on freshly squeezed orange juice and therefore, relatively little, such as maximum <NUM>%, of the total volume of the raw orange juice will pass through heat treatment. As a consequence, the quality of the orange juice, e.g. in terms of flavor, is improved. Setting up the production to obtain an enzyme pectin esterase (PEU) content that is less than <NUM> % of the PEU content of the raw orange juice has shown to be a very important parameter in an effort to achieve the above stated objectives.

According to the invention, the ultrafiltration is the only membrane filtering between cooling of the raw orange juice and aseptic filing of the orange juice produce. An example of membrane filtration may be microfiltration or a further ultrafiltration. The raw orange juice is only once filtered by a membrane filtering that is the ultrafiltration stated above and that separates the raw orange juice into the retentate and the permeate. Thus, objectives stated in this application are achieved by only one membrane filtering. In addition to that having only one membrane filtering decreases complexity and cost of the method and the system used to obtain the orange juice.

In this context, the membrane filtering is any filtering using membranes being able to filter particles or organisms having micro dimensions (e.g. micrometer).

As will be exemplified in the detailed description below, the method has effects on, i.e. provides certain values for, the lactic bacteria colony forming units (CFU) content, the vitamin C content, the pH value as well as the essential oil content of the orange juice after mixing. These effects are all favorable in terms of retaining the quality and flavor of the orange juice while at the same time provide a shelf life of the orange juice after mixing that is at least similar to that of NFC (not from concentrate) orange juice.

In a second aspect there is provided a system for producing orange juice. The system comprises a heat exchanger configured to cool raw orange juice. A ceramic type ultrafilter of the system having a membrane with a pore size of <NUM>-<NUM> and a channel size of <NUM>-<NUM> is configured to ultrafiltrate the cooled raw orange juice to produce a permeate and a retentate. A pasteurizer of the system is configured to pasteurize the retentate. A mixing unit of the system is configured to mix the permeate and the pasteurized retentate to produce orange juice having an enzyme pectin esterase content that is less than <NUM> % of the enzyme pectin esterase content of the raw orange juice.

An aseptic filling machine of the system is configured to aseptically fill packets with the orange juice produced by the mixing. This further aspect provides effects and advantages corresponding to the effects and advantages as summarized above in connection with the first aspect. All features and variants described herein in connection with the method according to the first aspect may be used for the system according to the second aspect, and vice versa.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which:.

With reference to <FIG>, an embodiment of a system <NUM> for producing orange juice <NUM> that retains much of the quality and flavor of freshly pressed orange juice <NUM> as summarized above will now be described. The system <NUM> is connected to a measuring and control system <NUM> that comprises processing and memory means <NUM>, <NUM>. The processing and memory means <NUM>, <NUM> are configured with software instructions that obtain measurements via signal lines <NUM> from schematically illustrated sensors <NUM> in the system <NUM> and also control the system <NUM> to perform the processing as described herein. As the skilled person will realize, the sensors <NUM> are configured such that they provide measurement signals representative of any desirable parameter related to the production of orange juice <NUM>, as will be discussed further in the following.

The system <NUM> comprises a storage tank <NUM> that holds raw orange juice <NUM> that has been obtained according to known techniques, e.g. by means of pressing freshly harvested oranges in an appropriately configured orange press.

The raw orange juice <NUM> is passed through a heat exchanger <NUM> to obtain a suitable temperature for the subsequent filtration steps. It has been found that a suitable temperature may be in the interval <NUM>-<NUM>. For example, a heat exchanger of the type the company Alfa Laval offers under the name "C3-SR" may be used for this, or any other suitable heat exchanger may be used.

A conventional slot filter <NUM> is arranged downstream the heat exchanger <NUM> to remove undesired large pulp particles from the raw orange juice <NUM>.

An ultrafilter <NUM> is arranged downstream the slot filter <NUM> to separate the raw orange juice <NUM> into a permeate <NUM> and a retentate <NUM>. The ultrafilter <NUM> is a ceramic type filter having a membrane with a pore size of <NUM>-<NUM>, or a pore size of <NUM>, and a channel size of <NUM>,<NUM>-<NUM>,<NUM>, or a channel size of <NUM>. The main function of the ultrafilter <NUM> is to separate the inlet stream into two other streams; the retentate <NUM> and the permeate <NUM>. To do this separation a pressure of <NUM>,<NUM>-<NUM>,<NUM> bar, or more specifically a pressure of <NUM>,<NUM> bar, is applied to the raw orange juice <NUM> and the product is fed through the ceramic membrane described above. The retentate <NUM> is retained at this membrane and the permeate <NUM> passes the membrane. The concentration factor of the ultrafilter <NUM> is in the range of <NUM>,<NUM> to <NUM>,<NUM>. The concentration factor is determined as the starting volume divided by the end volume, i.e. the volume of raw juice <NUM> that enters the ultrafilter <NUM> divided by the volume of retentate <NUM> that leaves the ultrafilter <NUM>.

The retentate <NUM> that exits the ultrafilter <NUM> enters a retentate storage tank <NUM>. The retentate storage tank <NUM> may be a buffer tank and it has a jacket though which ice water may flow to keep the retentate <NUM> at a temperature lower than <NUM>. The retentate storage tank <NUM> may also have an agitator to homogenize the retentate <NUM>. A pasteurizer <NUM> receives the retentate <NUM> from the retentate storage tank <NUM> and pasteurizes the retentate <NUM>. For example, the pasteurizer <NUM> may be a tubular heat exchanger that heats the retentate <NUM> to a temperature of at least <NUM> by indirect heat exchange. The retentate <NUM> is kept at minimum <NUM> for at least <NUM> seconds to inactivate enzymes and kill deteriorating and pathogenic microorganisms.

A mixing unit <NUM> is connected such that it receives the permeate <NUM> from the ultrafilter <NUM>, and is connected such that it receives the pasteurized retentate <NUM> from the pasteurizer <NUM>. The mixing unit <NUM> is further configured to mix the permeate <NUM> and the pasteurized retentate <NUM> to produce orange juice <NUM>. The mixing unit <NUM> may be an aseptic storage tank, which may include a flow re-circulator and/or an agitator for efficiently mixing the retentate <NUM> and the permeate <NUM>. Mixing may be achieved in other ways, for example by using so called in-line mixing, where the permeate <NUM> and the retentate <NUM> are fed into the same fluid line, for example via a branch pipe. The mixture of the permeate <NUM> and the retentate <NUM> forms the final orange juice <NUM>.

An aseptic filling machine <NUM> is connected to receive the orange juice <NUM> from the mixing unit <NUM> and is arranged to aseptically fill packets <NUM> with the orange juice <NUM>. The filling machine may be any conventional machine built for aseptically filling packets with liquid food.

As will be described below, the system <NUM> is operated to produce orange juice <NUM> from raw orange juice <NUM>. Various parameters are obtained from the raw orange juice <NUM>, the permeate <NUM>, the retentate <NUM>, before and after passing through the pasteurizer <NUM>, and the orange juice <NUM> after mixing in the mixing unit <NUM>, as will be exemplified in more detail below. The parameters are obtained by the described process and may be measured by means of the sensors <NUM> as well as by means of sampling and subsequent laboratory analysis as follows:
pH values are obtained by conventional pH meters. Brix values are obtained by conventional Brix meters. Vitamin C values are obtained by conventional methods using sampling and subsequent laboratory titration analysis. Enzyme values are obtained by sampling and by following the procedure for PEU test described in "Citrus Processing: Quality Control and Technology" by Dan A. Total lactic bacteria values and listeria monocytogenes values are obtained by sampling and subsequent conventional laboratory methods. Essential oil values are obtained by using the Scott Method (Bromide-Bromate solution), also described in "Citrus Processing: A Complete Guide" by Dan A. The essential oil is the combination of oils (hydrocarbons) present in oranges, which typically comprise of more than <NUM>% D-limonene. Color and lightness values are obtained by colorimeter measurements, by using conventional equipment such as Konica Minolta type CM-2600d spectrophotometer. Acidity (nitric acid) values are obtained by using sodium hydroxide titration method.

Turning now to <FIG> and with continued reference to <FIG>, software instructions that are stored in the memory <NUM> may be executed by the processor <NUM> in the measuring and control system <NUM> in order to obtain measurable values and to provide control signals to the system <NUM>, via the signal lines <NUM>, and thereby perform a method for producing orange juice <NUM> that has the values and properties discussed herein.

Such a method comprises cooling <NUM> raw orange juice <NUM> and, as exemplified in <FIG>, the raw orange juice <NUM> may originate in the storage tank <NUM> and be cooled in the heat exchanger <NUM> to a temperature that is suitable for the subsequent ultrafiltration.

The cooled raw orange juice <NUM> is ultrafiltrated <NUM> in the ultrafilter <NUM> to produce a permeate <NUM> and a retentate <NUM>. A suitable temperature at which the raw orange juice <NUM> is ultrafiltrated is in the range of <NUM>-<NUM>. As indicated in <FIG>, the cooled raw orange juice <NUM> may optionally have been subjected to filtering in the slot filter <NUM> before being ultrafiltrated in the ultrafilter <NUM>.

The retentate <NUM> that emanates from the ultrafiltration <NUM> is pasteurized <NUM> in the pasteurizer <NUM>. Optionally, the retentate <NUM> may exit from the ultrafilter <NUM> into the retentate storage tank <NUM> prior to being provided to the pasteurizer <NUM>. With regards to the pasteurization <NUM>, the pasteurization temperature is <NUM> and the retentate is held at this temperature for at least <NUM> seconds.

The permeate <NUM> and the pasteurized retentate <NUM> is mixed <NUM> in the mixing unit <NUM> to produce orange juice <NUM>. The orange juice <NUM> has an enzyme pectin esterase (PEU) content that is less than <NUM>% of the PEU content of the raw orange juice <NUM>.

Packets <NUM> are then aseptically filled <NUM> with the orange juice <NUM> that is obtained by the mixing <NUM>.

In an embodiment, the raw orange juice <NUM> that enters the filter <NUM> is not been subjected to any prior microfiltration, ultrafiltration, nanofiltration or filtration by reverse osmosis, while the neither the permeate <NUM> nor the retentate <NUM> that leaves the filter <NUM> have been subjected to any subsequent microfiltration, ultrafiltration, nanofiltration or filtration by reverse osmosis. In other words, the only filtration that is used in the process, not counting courser filtration than microfiltration such as the filtering in the slot filter <NUM>, is one step of ultrafiltration.

In the method for producing orange juice <NUM> it has been found that the retentate <NUM>, before the pasteurization <NUM>, should have a PEU content in the interval <NUM>% to <NUM>% of the PEU content of the raw orange juice <NUM>, and the retentate <NUM>, after the pasteurization <NUM>, should have a PEU content in the interval <NUM>% to <NUM>% of the PEU content of the raw orange juice <NUM>. Also, it was found that the permeate <NUM> should have a PEU content in the interval <NUM>% to <NUM>% of the PEU content of the raw orange juice <NUM>.

In the method for producing orange juice <NUM>, in the orange juice <NUM> produced by the mixing <NUM>, the number of lactic bacteria colony forming units, CFU, per milliliter is less than <NUM>% of the number of lactic bacteria CFU per milliliter in the raw orange juice <NUM>. Furthermore, in the retentate <NUM>, before the pasteurization <NUM>, the number of lactic bacteria CFU per milliliter is in the interval <NUM>% to <NUM>% of the number of lactic bacteria CFU per milliliter in the raw orange juice <NUM>, and in the retentate <NUM>, after the pasteurization <NUM>, the number of lactic bacteria CFU per milliliter is in the interval <NUM>% to <NUM>% of the number of lactic bacteria CFU per milliliter in the raw orange juice <NUM>. Also, it was found that in the permeate <NUM>, the number of lactic bacteria CFU per milliliter is in the interval <NUM>% to <NUM>% of the number of lactic bacteria CFU per milliliter in the raw orange juice <NUM>.

In the method for producing orange juice <NUM> it has been found that, in the orange juice <NUM> produced by the mixing <NUM>, the vitamin C content is more than <NUM>% of the vitamin C content of the raw orange juice (<NUM>). Furthermore, in the retentate <NUM>, before the pasteurization <NUM>, the vitamin C content is in the interval <NUM>% to <NUM>% of the vitamin C content of the raw orange juice <NUM>, and in the retentate <NUM>, after the pasteurization <NUM>, the vitamin C content is in the interval <NUM>% to <NUM>% of the vitamin C content of the raw orange juice <NUM>. Also, it was found that in the permeate <NUM>, the vitamin C content is in the interval <NUM>% to <NUM>% of the vitamin C content of the raw orange juice <NUM>.

In the method for producing orange juice <NUM> it has been found that, in the orange juice <NUM> produced by the mixing <NUM>, the pH value is in the interval <NUM>% to <NUM>% of the pH value of the raw orange juice <NUM>. Furthermore, in the retentate <NUM>, before the pasteurization <NUM>, the pH value is in the interval <NUM>% to <NUM>% of the pH value of the raw orange juice <NUM>, and in the retentate <NUM>, after the pasteurization <NUM>, the pH value is in the interval <NUM>% to <NUM>% of the pH value of the raw orange juice <NUM>. Also, it was found that in the permeate <NUM>, the pH value is in the interval <NUM>% to <NUM>% of the pH value of the raw orange juice <NUM>.

In the method for producing orange juice <NUM> it has been found that, in the orange juice <NUM> produced by the mixing <NUM>, the essential oil content is more than <NUM>% of the essential oil content of the raw orange juice <NUM>. Furthermore, in the retentate <NUM>, before the pasteurization <NUM>, the essential oil content is in the interval <NUM>% to <NUM>% of the essential oil content of the raw orange juice <NUM>, and in the retentate <NUM>, after the pasteurization <NUM>, the essential oil content is in the interval <NUM>% to <NUM>% of the essential oil content of the raw orange juice <NUM>. Also, it was found that in the permeate <NUM>, the essential oil content is in the interval <NUM>% to <NUM>% of the essential oil content of the raw orange juice <NUM>.

Detailed results from operation of the system <NUM> according to the method described above have resulted in parameter values as specified in tables 1a-c as follows:.

Claim 1:
A method for producing orange juice (<NUM>) by only one membrane filtering, comprising:
- cooling (<NUM>) raw orange juice (<NUM>),
- ultrafiltrating (<NUM>) the cooled raw orange juice (<NUM>) to produce a permeate (<NUM>) and a retentate (<NUM>) by a ceramic type ultrafilter (<NUM>) having a membrane with a pore size of <NUM>-<NUM> and a channel size of <NUM>-<NUM>;
- pasteurizing (<NUM>) the retentate (<NUM>),
- mixing (<NUM>) the permeate (<NUM>) and the pasteurized retentate (<NUM>) to produce orange juice (<NUM>) having an enzyme pectin esterase, PEU, content that is less than <NUM>% of the PEU content of the raw orange juice (<NUM>), and
- aseptically filling (<NUM>) packets (<NUM>) with the orange juice (<NUM>) produced by the mixing.