Patent Publication Number: US-2004043126-A1

Title: Method and apparatus for peeling citrus fruit

Description:
[0001] This invention relates to a method and apparatus for peeling citrus fruit and in particular for producing skinned segments.  
       [0002] A vertical cross section of a citrus fruit is shown in FIG. 1 where a citrus fruit  10  has a fruit portion divided into segments  11  surrounded by a spongy layer, the pith or albedo  12 , which is itself is surrounded by a thin waxy outer layer, the peel or cuticle  13 . The segments are covered by a segment membrane. A citrus fruit is typically more or less spheroid having a longitudinal axis  14  passing through a stem end  15  and a blossom end  16 . The albedo is mostly composed of pectin, cellulose and hemi-cellulose with numerous air sacs. An average grapefruit may contain up to 200 ml of air in these air sacs.  
       [0003] It is well known in the art to use enzymes to assist in the removal of the peel and albedo from the fruit portion of a citrus fruit, the enzymes being used to at least partially digest the pectin and cellulose and thereby loosen the peel.  
       [0004] Thus it is known from U.S. Pat. No. 4,284,651 to produce segments from citrus fruits using an enzyme. The fruit is first heated so that the core is at 20° to 40° C. and the surface at 40° to 60° C., which takes 10 to 60 minutes. The peel is scored to barely penetrate the albedo and the fruit submerged in pectinase under a vacuum of 25 to 30 ins of mercury (85 to 102 kPa) at a temperature of 20° to 50° C. to remove air from the air sacs in the albedo. Pectinase then enters the air sacs when the vacuum is released. It may be necessary to repeat the process to remove sufficient of the air. The fruit is then incubated for 15 minutes to 2 hours at a temperature of 30° to 60° C. in an oven, in order for the enzyme to dissolve some of the pectin and cellulose in the albedo and loosen the peel. The fruit can then be mechanically peeled and segmented by “hand, scoop, section knives” from the core.  
       [0005] U.S. Pat. No. 5,000,967 discloses an alternative use of enzymes in which lower temperature are used and the enzyme is infused into the albedo using raised pressures without the use of a vacuum to extract the air. Thus, the core and surface of the fruit are maintained at below 40° C. and the peel is scored into wedges, rings, spirals or is grated or scratched. The fruit is submerged in an enzyme at room temperature and 60 to 10 pressure pulses of 20 to 40 p.s.i (180 to 276 kPa) are applied for 15 seconds with breaks between the pulses of 5 seconds. The fruit is incubated at less than 30° C. for 1 to 2 hours. This process is said to provide improved ease of peeling and less adhering albedo than in the vacuum infusion method with more segments being removed. It is supposed that the pulse pressure tends to flex the peel to work the enzyme solution through the albedo. This process has the advantage over the earlier process that because the enzyme is maintained at about room temperature, the enzyme can be reused for 9 to 10 batches, whereas in the previous process the effectiveness of the enzyme was destroyed after one use by the higher temperatures.  
       [0006] Methods of peeling whole citrus fruits, rather than producing segments, are known from U.S. Pat. No. 5,196,222 and U.S. Pat. No. 5,200,217.  
       [0007] U.S. Pat. No. 5,196,222 discloses a process in which the peel of the fruit is first perforated to allow the enzymes to access the albedo then the fruit is orientated so that it rotates on the longitudinal axis  14  through the stem so that a single equatorial cut can be made through the peel by knives urged towards the fruit. The fruit is then infused with a fluid beneath the outer surface, using either a vacuum or pressure method and incubated at less than 20° C. for 10 to 16 minutes. The fruit is then peeled manually, although the disclosure speculates that peeling could be automated, and the fruit is brushed to remove the strings of cellulose before being cooled and packaged.  
       [0008] In U.S. Pat. No. 5,200,217, the fruit is first chilled below 10° C. and preferably to 5° to 8° C. so that the enzyme will not affect the fruit portion in the subsequent infusion. The fruit is infused with the enzyme at 35° C. either using a vacuum of 25 to 30 inches of mercury (85 to 120 kPa) or using pressure pulses of 20 to 40 psi (180 to 276 kPa), using 15 second pulses with 5 second gaps between the pulses. The fruit then has to be incubated for 20 to 90 minutes depending on the time within the harvesting season and it is stated that in this time there is insufficient time for the core to warm and therefore for the enzyme to affect the fruit portion to any large extent.  
       [0009] The use of enzymes, therefore, normally requires the raising of the temperature of the fruit and long incubation times. The raised temperatures tend to destroy vitamin C and flavonoids in the fruit and the enzymes require long incubations periods in order partially to dissolve the albedo to loosen the fruit. Special precautions have to be taken to mitigate enzyme attack on the fruit portion. Moreover, manual peeling and, where required, segmenting of the fruit, are normally required as part of the process.  
       [0010] U.S. Pat. No. 5,560,951 discloses a non-enzymatic method of peeling a citrus fruit. In this process, the fruit is washed and held for 30 minutes at 25° to 45° C. and scored with longitudinal cuts before being infused with water either under a vacuum of 3 kPa for 3 minutes which is slowly released over the succeeding 3 minutes, or is infused under pressure at 203 kPa using compressed air in which 10 pulses of 15 seconds are applied to the fruit. Subsequent to infusion, it is disclosed that there is no advantage in incubating the fruit which has been infused with water as there is with fruit infused with enzymes. The fruit is then peeled by hand. It is disclosed that peeling time is actually longer for grapefruit using water infusion than for enzyme infusion but comparable with the peeling times using enzymes for oranges and tangelos. It is further disclosed that there is less juice leakage and softening during storage with water infusion than with enzyme infusion, which may be due to enzyme penetrating into the fruit portions in the enzyme methods. Peeling of the water infused fruit was, however, hampered by incomplete hydration of the albedo, particularly in the pressure method. According to the disclosure, the segments did not become slimy with storage as is experienced using enzyme. Problems were disclosed of dry albedo using the lower temperature of the process, in particular with the low pressure infusion process and where there were substantial air spaces or slightly desiccated peels.  
       [0011] In WO 01/50891, a method and apparatus for peeling citrus fruit is provided, in which the citrus fruit is first of all submerged in liquid under a vacuum to extract air from the albedo portion and then subjected to pressure to loosen the peel portion in the albedo from the fruit portion. In particular, pressures in the range 400 kPa to 20000 kPa are preferably used. This can lead to generally good removal of the albedo and peel from the fruit portion but the resulting skinned segments may still have a certain amount of albedo still attached, after treatment.  
       [0012] It is, apparent that the enzyme methods known in the art, require long processing times and may result in poor shelf life. The pressure or temperature infusion methods with water result in some problems with manual peeling because of sections of dry albedo. The pressure methods of the prior art require pressure pulsing.  
       [0013] It is an object of the present invention to at least partially alleviate the foregoing difficulties.  
       [0014] The present inventor has discovered that the method of WO01/50891 may be improved by adding a small amount of enzyme in the liquid during the vacuum step, the pressurising step, or both of them. The resulting fruit portion can be peeled and cleaned to provide excellent, clean fruit segments.  
       [0015] Accordingly, in a first aspect, the present invention provides a method for preparing citrus fruit including the steps of:  
       [0016] a) providing a citrus fruit having a flesh portion, an albedo portion, a peel portion and a longitudinal axis;  
       [0017] b) scoring the peel portion to provide access to the albedo portion without piercing the flesh portion;  
       [0018] c) submerging the fruit in a liquid under a vacuum to extract air from the albedo portion;  
       [0019] d) subjecting the fruit submerged in the liquid to pressure to produce infused fruit, in which the peel portion and the albedo portion are loosened from the fruit portion;  
       [0020] e) removing the peel portion and the albedo portion from the fruit portion to produce peeled fruit,  
       [0021] f) preparing the fruit portion for consumption and storage,  
       [0022] wherein, in the step (c) or step (d), or both, the liquid comprises an enzyme.  
       [0023] The enzyme employed is suitably pectinase. Suitably, the liquid employed in step (c) and/or step (d) is an aqueous solution of pectinase. Suitably, the aqueous solution of pectinase comprises between 0.5 and 2% by weight of pectinase, more preferably 1-1.5% by weight.  
       [0024] Conveniently, the step (a) of providing a citrus fruit includes washing the fruit.  
       [0025] Advantageously, the washing step includes the steps of wetting the peel portion with water and detergent, and brushing the peel portion and rinsing the peel portion with water. The fruit may additionally be sterilised, for example using chlorine or ozone, in a conventional manner.  
       [0026] Conveniently, the step (a) of providing a fruit includes a step of grading the fruit by size.  
       [0027] Conveniently, the step (b) of piercing the peel portion to provide access to the albedo portion includes cutting through the peel portion into the albedo portion to produce slit fruit so as to facilitate subsequent removal of the peel and albedo portions from the fruit portion of the slit fruit.  
       [0028] Advantageously, the step of cutting through the peel portion comprises cutting the peel portion with latitudinal cuts. Preferably, at least, two, more preferably at least three cutting operations are performed to provide at least two, more preferably at least three intersecting sets of latitudinal cuts. A method and apparatus for achieving this will be described later below.  
       [0029] The steps (a) and (b) may each be carried out in continuously operating apparatus.  
       [0030] Conveniently, the step (c) of submerging the fruit in a fluid under vacuum comprises submerging the fruit under water in a vacuum in the range 40 to 100 kPa below atmospheric pressure, more preferably 51 to 100 kPa below atmospheric pressure.  
       [0031] Preferably, the fruit is submerged under vacuum for a period for a time in the range 10 seconds-2 minutes, more preferably 30 seconds-1.5 minutes.  
       [0032] The fruit may be submerged under vacuum in two steps. In a first step, the fruit is submerged under water under a vacuum in the range 40-70, more preferably 40-60 kPA below atmospheric pressure. This first step suitably last for a period in the range 10-60 seconds, more preferably 20-40 seconds. After the first step, the fruit is maintained in the fluid under vacuum under further reduced pressure, preferably in the range 70-100 kPa below atmospheric pressure. In the second step, the fruit may be maintained under vacuum for 30 seconds-2 minutes, preferably 40 seconds to 1 minute.  
       [0033] Preferably, the step (c) further includes the step of releasing the vacuum over a period of time in the range 20-60 seconds, more preferably 25-35 seconds. It is found to give better separation if vacuum is released slowly.  
       [0034] Suitably, during the step (c), the fruit is maintained at ambient temperature, or at a temperature in the range 15-25° C.  
       [0035] There may be a further incubating step between steps (c) and (d) in which the fruit is maintained in water at ambient pressure and temperature for a period in the range 10-30 minutes, more preferably 15-20 minutes.  
       [0036] Conveniently, the step (d) of subjecting the fruit submerged in the fluid to pressure comprises subjecting the fruit to a pressure in the range 400-20,000 kPa, more preferably about 4,000 kPa.  
       [0037] Suitably, the step (d) of subjecting the fruit to pressure is carried out at ambient temperature or at a temperature in the range 15-25° C.  
       [0038] It is found that, during the vacuum step, the optional incubating step and the pressurising step (d), the fruit suitably increases in weight by 33%. The fruit suitably increases in volume by 7-12%. Without wishing to be bound by theory, it is believed that this is due to replacement of the air in the sacs by water and swelling of the sacs under the influence of pressure.  
       [0039] The step (c), the optional incubating step and the pressurising step (d) may be carried out batchwise. They may all be carried out in the same vessel or they may be carried out in separate vessels in succession.  
       [0040] Apparatus for carrying out the step (c) according to the present invention preferably comprises an evacuation and pressure vessel; a vacuum reservoir connectable to the evacuation and pressure vessel to rapidly partially evacuate the evacuation and pressure vessel, the vacuum reservoir being evacuable by a vacuum pump connectable thereto; a pressure pump connectable to the evacuation and pressure vessel for filling the evacuation and pressure vessel with a liquid under pressure; and pressure release means for permitting the liquid in the evacuation and pressure vessel to be returned to atmospheric pressure.  
       [0041] A process and apparatus for moving the peel portion and the albedo portion from the fruit portion will be described further below.  
       [0042] Conveniently, the step (f) of preparing the fruit portion for consumption or storage includes segmenting the fruit portion into segments.  
       [0043] A suitable method and apparatus for segmenting the fruit portion into segments will be described further below.  
       [0044] Conveniently, the step (f) of preparing the fruit portion for consumption or storage comprises the further step of treating the segments with acid.  
       [0045] It is found that the step of treating the segments with acid effectively deactivates any remaining enzyme so that further degradation of the fruit does not occur. The step of treating the segments with acid may be included in order to remove outer membranes from the segments.  
       [0046] Advantageously, the further step of removing outer membranes from the segments with acid comprises removing the outer membranes with dilute citric acid and/or dilute hydrochloric acid.  
       [0047] Preferably, the step of removing the outer membranes with dilute citric acid and/or dilute hydrochloric acid comprises passing the segments for 1-3 minutes through a bath containing a solution in the proportions of 1 gm of citric acid: 100-200 ml of water: 5 ml dilute hydrochloric acid, the solution having a pH in the range 0.88 to 0.91. The temperature range is suitably 30-60° C.  
       [0048] Conveniently, the step of removing the membranes with acid comprises the further steps of draining acid from the segments and neutralising any of the acid by immersing the segments in an alkaline solution.  
       [0049] Conveniently, the step of immersing the segments in an alkaline solution includes the step of dissolving any remaining segment membrane in the alkaline solution.  
       [0050] Conveniently, the alkali solution used in the alkali bath, used in the method described above, is obtainable by dissolving sodium hydroxide crystals in water in the proportion of 1 gm of sodium hydroxide crystals to 100 ml of water.  
       [0051] Preferably, the step of immersing the segments in an alkaline solution comprises immersing the segments in dilute sodium hydroxide at a temperature in the range 30° C. to 60° C. for 1-3 minutes.  
       [0052] Preferably, the step (f) of preparing the fruit for consumption or storage includes agitating and rinsing the segments in cold water.  
       [0053] Advantageously, the step (f) of preparing the fruit for consumption or storage includes chilling the segments in cold water, drying the segments and coating the segments.  
       [0054] Conveniently, the step of chilling the segments in cold water comprises chilling the segments in water at a temperature in the range 0° C. to 2° C.  
       [0055] Preferably, the step of coating the segments comprises coating the segments with ascorbic acid 0.5% and/or citrus oil 0.5%.  
       [0056] The method and apparatus for forming cuts in the peel and albedo portion of the fruit may be substantially as described in WO 01/50891. However, it is found that a single set of latitudinal slits formed by that method may not be sufficient to allow penetration of enzyme to all parts of the albedo. The present inventor has realised that penetration may be improved by arranging a plurality of cutting means in succession, each cutting means comprising means for rotating the fruit, the means for rotating the fruit being movable to allow the fruit to move to the next cutting means in succession.  
       [0057] This arrangement is believed to be inventive in its own right. Accordingly, in the second aspect, the present invention provides a cutter for cutting into the albedo portion of a citrus fruit, comprising a plurality of cutting means in succession, each cutting means comprising:  
       [0058] first and second movable surfaces movable in opposite directions, for supporting and rotating between them a citrus fruit,  
       [0059] an array of cutter knives biassed towards the first and second movable surfaces for cutting a plurality of latitudinal slits through the peel portion to the albedo portion of a citrus fruit, and depth control means for preventing the cutter knives piercing the fruit portion,  
       [0060] the second movable surface being displaceable away from the first surface so that a citrus fruit carried on the first movable surface can be released and passed to the next cutting means in succession or out of the cutter.  
       [0061] The first and second movable surfaces may each comprise rotatable rollers or continuously movable belts. In a particularly preferred embodiment, the first movable surface comprises a moving belt for supporting on a horizontal surface thereof, a citrus fruit, the second movable surface comprising a rotatable roller located above the horizontal surface of the belt. It is further preferred that the first movable surface for each of the plurality of cutting means is provided by the same continuously movable belt extending through each of the cutting means, each cutting means comprising a second movable surface in the form of a roller above the belt. In this way, when the second movable surface is displaced away from the belt to release the citrus fruit, it is carried by the belt to the next cutting means in succession in a simple and easy manner.  
       [0062] Drive means may be provided for rotating the first movable surface and the second movable surface. Any suitable means may be provided for moving the second movable surface away from the first movable surface. For example, it may be mounted on an arm or on a piston. The second movable surfaces of the plurality of cutting means may be separately movable or they may be moved all at once by a common displacing apparatus.  
       [0063] Means may be provided between respective cutting means for rotating the citrus fruit about an axis different to the axis about which the fruit is rotated by the first and second movable surfaces. In this way, the citrus fruit is repositioned between respective cutting means to ensure that the sets of latitudinal slits formed by the plurality of cutting means cross one another at an angle.  
       [0064] Conveniently, the cutter knives each comprise an L-shaped blade holder having a first arm and a second arm shorter than the first arm, the first arm housing a protruding blade; the blade holder being pivotable about a pivot point adjacent a junction between the first arm and the second arm; and the cutter further comprising: pivot means passing through the pivot point; bias means acting on the second arm to bias the first arm towards the conveyor and rotator means; and stop means such that the blade holder is rotatable about the pivot point between a rest position in which the second arm abuts the stop means to limit downward rotation of the first arm and an upper position in which the first arm abuts the stop means to limit upward rotation of the first arm.  
       [0065] Advantageously, the depth control means comprises a shoulder between the blade holder and the blade for engaging an outer surface of the peel to allow the blade to penetrate only a pre-determined distance through the peel portion and into the albedo portion.  
       [0066] Water jets may be provided for spraying at least the knives and preferably also the movable surfaces, to act as a lubricant and to remove deposits left during the cutting operation.  
       [0067] The surface of the second movable surface may be configured to improve its frictional engagement with the citrus fruit. For example, it may be ridged or patterned. Preferably, a plurality of small protrusions or pins of lengths in the range 1-5 mm, preferably around 2 mm are provided for engaging the surface of the citrus fruit.  
       [0068] The step (e) of removing the peel portion and the albedo portion from the fruit portion preferably includes pressing the infused fruit by a predetermined amount to loosen the peel portion and the albedo portion from the fruit portion to produce pressed fruit. The step of pressing the infused fruit may be as described in WO 01/50891, in which the infused fruits are passed between brush rollers and contoured bars separated from the brush rollers by a distance 1 cm-3 cm less than the diameter of the infused fruit, followed by an optional brushing step.  
       [0069] However, it has been found that the removal of peel and albedo from the fruit portion is not always achieved completely by this process, due to the gaps between the brushes of the brush rollers. The present inventor has realised that more effective removal of peel can be achieved by passing the fruit through a hole formed in a resilient material structure which will strip the peel off the sides of the fruit. This apparatus is believed to be inventive in its own right.  
       [0070] Accordingly, in a third aspect of the invention, there is provided a peeler for peeling the peel and albedo portion from the fruit portion of a citrus fruit, comprising at least one peeling means comprising a structure of resilient material having an aperture passing through the structure, and means for driving the fruit through the aperture.  
       [0071] Preferably, there are a plurality of peeling means in succession, to provide a peeling action in different directions. Means may be provided for rotating the fruit between each peeling means to ensure that it is fed in a different orientation to each respective peeling means. The means for rotating the fruit may simply comprise a chute extending from one peeling means to the next peeling means, along which the citrus fruit may roll. The sizes of the apertures of successive peeling means which are placed in succession may become gradually smaller to provide an increasing peeling effect.  
       [0072] Preferably, the fruit passed to the peeler has been graded before treatment so that the average size of the fruit passed to the peeler is a predetermined value, the size of the aperture in the peeling means being smaller than the predetermined average size by a value in the range 1-4 cm, preferably about 3 cm.  
       [0073] The resilient means may comprise a silicone rubber. It may be formed as a sheet. The sheet may be of a thickness in the range of 1 mm-10 mm, more preferably 2-5 mm, and most preferably around 3 mm in thickness. It may be formed as a circular sheet with an annular hole in the middle. The sheet may be pierced to further reduce the stiffness of the peeling means. For example, a plurality of holes (suitably, circular holes) may be punched through the sheet of the peeling means.  
       [0074] Water sprays and air jets may be provided for lubricating and cleaning the surfaces of the peeler.  
       [0075] The means for driving the fruit through the aperture may comprise a piston for reciprocating movement through the aperture and back again. The piston may be operated electrically, mechanically or by compressed air or hydraulically.  
       [0076] Peel collecting means may be provided for removing peel removed from the citrus fruit. For example, means may be provided for blowing removed peel into a collecting means, for example a collecting chute. Optionally, a further peel removal means may be provided comprising a pair of contrarotating brushes defining a valley between them in which fruit may sit and be brushed. The fruit may sit in the valley for 1-3 minutes.  
       [0077] The segments of fruit portion may be loosened from one another by a segmenter as described in WO 01/50891, comprising two spaced apart rotatable drums defining a valley therebetween, delivering means for delivering peeled fruit to the valley for rotation by the drums therein, such that centripetal forces set up by rotation of the fruit by the drums cause the fruit to divide into segments.  
       [0078] However, it has been found difficult to balance the forces required to separate the segments with the forces liable to cause damage to the segments using this apparatus. The present inventor has realised that the segments of the fruit portion can be loosened from one another by a rolling and pressing operation.  
       [0079] It is believed that this is inventive in its own right, and in a fourth aspect, there is provided a segmenter for loosening the constituent segments of the fruit portion of a citrus fruit from one another, comprising:  
       [0080] means for rolling and pressing a citrus fruit, the rolling and pressing means being configured to apply a cyclically varying pressure to the citrus fruit.  
       [0081] It has been found that particularly good separation can be obtained if the fruit portion is chilled before passing it to the segmenter. Accordingly, the segmenter preferably further comprises cooling means for cooling a citrus fruit.  
       [0082] The chilling means may suitably comprise a liquid nitrogen tunnel in a manner known in the art. Preferably, the citrus fruit is chilled so that the temperature of the surface is in the range 0 to −2° C., preferably −1 to −2° C. and the temperature at the centre of the citrus fruit is in the range 0 to 5° C., preferably 1.5 to 3° C. The fruit portion may be chilled for a period in the range 10 minutes-60 minutes, preferably 20-30 minutes, more preferably 20 minutes.  
       [0083] The rolling and pressing apparatus of the present invention may be used to loosen segments, final separation of the segments being achieved by another apparatus or by hand. If sufficient pressure is applied, the segments may be completely loosened from one another.  
       [0084] The coating for coating segments of citrus fruit, preferably comprises ascorbic acid 0.5% and citrus oil 0.5%. 
     
    
    
     [0085] A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:  
     [0086]FIG. 1 is a schematic cross section through a citrus fruit;  
     [0087]FIG. 2 shows a flow diagram of the principal steps in the method of the invention;  
     [0088]FIG. 3 is a flow diagram showing the method of FIG. 2 in detail;  
     [0089]FIG. 4 is a schematic view of an apparatus according to the present invention for peeling citrus fruit;  
     [0090]FIG. 5 is a sketch side view of the cutter of FIG. 4 in a first position;  
     [0091]FIG. 6 is a sketch side view of the cuter of FIGS. 4 and 5 in a second position;  
     [0092]FIGS. 7 and 8 are views of the cutter sets of FIGS. 5 and 6, at a larger scale and in more detail.  
     [0093]FIGS. 9 and 10 show sketch sections through the apparatus of FIG. 5;  
     [0094]FIG. 11 is a schematic view of a citrus fruit after being scored in the apparatus of FIG. 5;  
     [0095]FIG. 12 is a schematic view of an infuser for use with the present invention;  
     [0096]FIGS. 13 and 14 show side and end views respectively of the fruit basket used in the infuser of FIG. 12;  
     [0097]FIGS. 15 and 16 are sketch end views of the infuser of FIG. 12 in the operating and unloading positions respectively;  
     [0098]FIG. 17 is a schematic view of the peeler of FIG. 4, in more detail;  
     [0099]FIG. 18 is a schematic view of a peeler diaphragm of the peeler of FIG. 17 at greater scale;  
     [0100]FIG. 19 is a flowchart showing the operation of one peeling means of the peeler of FIG. 17; and  
     [0101]FIG. 20 is a schematic side view of the segmenter of FIG. 4. 
    
    
     [0102] The method of the invention is shown in outline in FIG. 2. Referring also to FIG. 1, following preparation of the fruit in step S 100 , the peel  13  is scored or slit a number of times in step S 200 . The peel is scored through to the albedo  12  without piercing the segments  11 . The fruit is then immersed in water and subjected to a vacuum in step S 300 . This leads to some of the air from the air sacs in the albedo  12  being removed. The water in which the fruit is immersed comprises a dilute solution of pectinase. The fruit is left under vacuum for a period of time. The vacuum is then released and water infuses in step S 400  into the former air sacs and this is assisted by increasing the pressure of the water to 4000 kPa. At this pressure, the water may behave as a super solvent to dissolve the pectin and softens the albedo, cellulose and hemicellulose to such an extent that they can be subsequently removed by mechanical means. The pectinase assists in dissolving the pectin. Fruit is then peeled in step S 500 , segmented in step S 600  and prepared for consumption or storage in S 700 .  
     [0103] The process will be described in more detailed with reference to FIG. 3.  
     [0104] The preparation S 100  can be split into three primary operations. They are disinfection (S 110 ), grading the fruit into grades with certain size ranges (S 120 ) and orientating (S 130 ). It is found that it is important to grade the citrus fruit accurately into at least three classes (small, medium, large) which are matched to the size and setting of various parts of the apparatus to be described later.  
     [0105] The slitting operation S 200  will be described further below with reference to FIGS.  4  to  11 .  
     [0106] The evacuating and soaking step S 300 , and the pressurising step S 400  will be described further below with reference to FIGS.  12  to  16 . The peeling step S 500  will be described further below with reference to FIGS.  17  to  19 .  
     [0107] The segmenting step S 600  comprises two separate operations. This first is chilling in step S 610  and the second is segmenting in step S 620  which will be described further below with reference to FIG. 20.  
     [0108] The preparation of the citrus fruit for storage comprises three steps. The first step S 710  comprises immersing the citrus fruit in an acid bath. This has two functions. The acid bath helps to remove any remaining albedo which still adheres to the segments. It is also found that the immersion in the acid bath helps to deactivate any enzyme which remains on the fruit after the treatment step. This prevents the enzyme becoming active during storage, which would leave to damage to the fruit segments.  
     [0109] After treatment in the acid bath in step S 710 , the citrus fruit is immersed in an alkali bath in step S 720  to neutralise any remaining acid. Finally, in step S 730 , the citrus fruit is rinsed, chilled and coated as will be described further below with reference to FIG. 4.  
     [0110]FIG. 4 is a sketch view of an apparatus according to the invention.  
     [0111] Citrus fruit enters the apparatus at the top left hand corner of the page and leaves the apparatus at the bottom right hand corner.  
     [0112] Water jets  111  and revolving brushes  112  are provided to disinfect fruit  10  to be peeled, by thoroughly wetting the surface of the fruit with washer jets  111  and by brushing the outer surface of the peel with water and detergent as the fruit is moved over the revolving brushes  112  to remove field oils, soil, mould and dust. This is followed by a further set of water jets to provide a fresh water rinse.  
     [0113] A grader  120 , known per se, is provided to grade the fruit by size to ensure that the fruit is processed by subsequent stages of the apparatus adjusted for the particular graded size of fruit. Thus, for example, one size of fruit may be passed through the remaining parts of the apparatus at a time or separate channels through the apparatus may be provided for different sizes of fruit. It is found in practice that grading into three sizes of fruit (small, medium, large) is sufficient. A conveyor  121  of known design is provided to pass the fruit from the grader  120  to a cutter or slitter  200 . The cutter  200  will be described in detail further below, but comprises in outline a first moving surface  201  comprising a conveyor belt and a plurality of cutting stations. Each cutting station comprises a second moving surface  202  and a set of knives  203 . Each cutting station cuts the citrus fruit about a different axes, leading to a plurality of intersecting scores. The scores pierce the peel portion of the fruit and extend into the albedo portion  12  without piercing the segments  11 .  
     [0114] The cutter is shown in more detail in FIGS.  5 - 10 .  
     [0115]FIG. 5 shows a schematic side view of a cutter apparatus according to the present invention. Citrus fruit is fed in from the left-hand side and passed through the apparatus to the right-hand side. There are three cutter means, each comprising a cutter set  203  located above a first movable surface, which in all cases is defined by the upper face of the moving belt  201 . Adjacent each cutter set  203  is a second movable surface, in the form of a roller  202 . In use, a citrus fruit  151 ,  152 ,  153  will be held on top of the rolling belt  201 . It will be prevented from moving forwards by the roller  202 . The roller  202  is rotated in each case by a belt, so that the roller rotates in such a direction that the citrus fruit  151 ,  152 ,  153  is rotated by the combined action of the belt and roller. The cutter sets  203  are arranged such that they contact the peripheral surface of the citrus fruit, cutting through the peel into the albedo section in a manner which will be described further below.  
     [0116] Each roller  202  is mounted on the end of an arm  204 . Each arm  204  is itself pivoted at its lower end  205  so that it is rotatable in an upward direction. The arms are rotated by a crank mechanism comprising cranks  206  and a connecting rod  207 , the cranks and connecting rod being jointly operable by a cylinder  208  as will be described further below. Also visible in FIG. 5 are guide rails  209  extending alongside the belt  201  to prevent the citrus fruit sliding off. Also visible is a chute  210  for feeding citrus fruit, with a feeder mechanism  211  comprising a paddle with four arms projecting therefrom. Upon rotation of the paddle by a quarter turn, a single citrus fruit may be fed. FIG. 6 is a side view of the apparatus of FIG. 5 in which the cylinder  208  has been operated to draw up the crank mechanism  206  and thereby raise the arms  204  with the rollers  202  located at the ends to a height which will permit the citrus fruits  151 ,  152 ,  153  to be carried along by the belt  201 . During this step, the paddle  211  is rotated by a quarter turn so that a further citrus fruit  150  is fed onto the belt  201 . The citrus fruit  151  is allowed to pass underneath the roller  202 . After this has happened, the. roller  202  is lowered by the crank mechanism  206  so that the newly fed citrus fruit comes to rest against it, where it makes contact with the cutter set  203 . The citrus fruit  151  released from the first roller is fed along the belt to the second roller, which has been returned to the blocking position. Whilst it is moving, the fruit will be contacted by depending brushes  230 , rotated about a vertical axis by pneumatic motors. This will cause the citrus fruit to rotate about a vertical axis. In this way, the citrus fruit  151  is orientated in a different direction when it meets the next cutter set, so that the set of cuts formed by the second cutter set are at an angle to the first set of cuts. Once a citrus fruit has passed all three cutter sets, its will have on its surface, three sets of intersecting cuts at angles to one another, giving a very high level of cutting to the surface.  
     [0117]FIGS. 7 and 8 show sketch views of the cutter sets  203 . They are exactly as shown and described in WO 01/50891 and will not be described further.  
     [0118]FIG. 9 is a schematic cross section through the apparatus of FIG. 5 along the line IX-IX-IX. The frame  212  of the cutter can be seen. The frame comprises a vertical member and a horizontal member. Through the vertical member of the frame  212  there extends a shaft  213  of the belt roller  214 . A drive pulley  215  is shown for rotation by drive means (not shown). The cutter set  203  depends above the belt  201  in a position in which it will cut scores through the peel and into the albedo portion of a citrus fruit resting on the belt  201 . The position of the cutter set  203  is variable in vertical direction by adjusting the position of the vertical support  216 .  
     [0119]FIG. 10 is a schematic cross sectional view through the line X-X in FIG. 5. It shows the belt  201  and the roller  202  extending above the belt  201 . A plurality of pegs  217  are formed on the surface of the roller for enhancing the engagement between the roller and the citrus fruit. The roller  202  is supported on an arm  204 . The arm  204  is itself rotatably mounted on a shaft  218  which extends through the vertical part of the frame  212  and connects to a crank  206 . The crank  206  is connected by the connecting rod  207  to the cranks of the other two rollers. Further, there is a crank  219  which is connected by a shaft  220  to the cylinder  208  (not shown) whereby the arm may be rotated to lift the roller above the belt  201 , the lifting action being transmitted to the cranks  206  of the other two rollers  202  by the connecting rod  207 . Finally, coaxial with the shaft  218 , there is another rotatably mounted shaft  221 . The shaft  221  is rotatable by means  222  connected to rotating means, for example a pulley set, not shown. A further belt and pulley arrangement  223  on the other side of the frame  212  drives the shaft  224  of the roller  202  so that the roller  202  is rotated. Finally, the rail  209  to one side of the belts  201  can be seen, which prevents citrus fruits falling off the side and also rotates the fruits about a vertical axis as they are fed along the belt.  
     [0120]FIG. 11, is a schematic view of a citrus fruit which has been scored by the cutter sets  203  of all three cutting stations shown in FIG. 5. It can be seen that a very large number of intersecting cuts are formed, allowing a high level of penetration of the aqueous solution of enzyme into the citrus fruit.  
     [0121]FIG. 12 is schematic illustration of the infuser apparatus for use in the present invention. In this case, fruit is fed in from the right hand side of the top into a cage  301  which is described further in relation to FIG. 13. The cage comprises a cylindrical drum with an open top, mesh sides  305  and mesh ends  306 , to allow penetration of water. Finally, roller wheels  308  are provided to allow the cage to be moved backward and forwards in the direction parallel to its longitudinal axis. In FIG. 12, the cage  301  is shown rolled into position inside a tilting drum structure  309 . The tilting drum structure  309  comprises a pair of annular flanged ends  310  spaced apart by longitudinal frames  311 . The tilting drum  309  is shown further in FIGS. 15 and 16. In FIG. 15, it can be seen in its normal position. A track is defined by track members  312  which is configured to accept the rollers  308  of the cage  301  so that the cage can be slid into and out of the tilting drum  309 . A further pair of rollers  313  are provided on either side of the cage drum  309 , rotatably engagable with the mesh sides of the cage  301  to support the sides of the cage in the drum.  
     [0122] Referring back to FIG. 12, the flanged ends  310  are engagable with rollers  314  which can be driven by a motor (not shown) to rotate the tilting drum  309  through about 90°. FIG. 16 shows the tilting drum  309  in the rotated position. It can be seen that the cage  301  contained inside the drum is now in a position in which the fruit may be discharged from the cage  301  through the space between the frames  311  of tilting drum  309 . Finally, a traction motor  315  is provided which can be used to pull a cable  316  which is attached to the cage  301  as will be described further below.  
     [0123] A second tilting drum which is a mirror image of the tilting drum  309  is provided on the other side of the infuser drum  302 . The second tilting drum  317  will not be described in detail, as it is exactly the same in design as the tilting drum  309 . However, it should be noted that the tilting drum  317  as illustrated does not have a cage inside it. A cable  319  has been drawn out from the traction motor  318  so that a hook attached to the end the cable  319  is in position in which is it ready to engage the next cage as will be described further below.  
     [0124] The infuser comprises a longitudinally horizontally extending hollow cylindrical pressure vessel manufactured from stainless steel of food grade. The ends  321  and  322  comprise sealable pressure doors which are openable to admit a cage  301  into the pressure vessel  302 . A cage  303  is shown in dotted lines inside the pressure vessel. A track  323  is formed in the bottom of the infuser  302  along which the cage rollers  308  of the cage may run. The infuser  302  is provided with a pressure senser  324  for measuring and displaying the pressure above atmospheric pressure in the infuser  302 . A vacuum sensor  325  is provided for measuring the pressure below atmospheric pressure in the infuser  302 . Separate devices for measuring pressure above and below atmospheric pressure are provided because of the very wide range of pressures employed in the infuser. It is generally difficult to obtain a single pressure measuring device which can be accurately used across the whole range of pressures employed. The pressure sensers  324  and  325  are connected to a central processor  327  for giving signals indicating the pressure within the infuser  302 . There is a vacuum release valve  326 . The vacuum release valve  326  comprises a remotely operable valve which is controllable by the central processor  327 . A vacuum pump  328  is provided, operable by control signals received from the central processor  327 , for evacuating the space inside the infuser  302 . A pressurising device  329  is provided for pumping water at pressure into the infuser  302 . The pump  329  is controllable by signals from the central processor  327 . The water is supplied by water tank  330 . The water tank  330  preferably comprises means (not shown) for introducing enzymes in solution to the water which is to be pumped into the infuser  302 . A pressurised water return valve  331  is provided, controllable by signals from the central processor  327  to allow water under pressure to be released from the infuser and returned either by gravity or by a pump to the tank  330 .  
     [0125] The operation of the infuser shown in FIG. 12 will now be described.  
     [0126] Firstly, slit citrus fruits from the cutter shown in FIG. 5 are fed into the cage  301  on the right hand side of the figure, through the open top. This is continued until the cage is substantially full. Then, the doors  321  and  322  of the pressure vessel are opened and the cable  319  from the traction motor  318  is extended through the pressure vessel so that the hook  320  is engaged with the cage  301 . The motor  318  is then used to the draw the cage  301  through the open door  322  into the infuser  302 . It should be noted there is a small gap between track  323  and the track of the tilting drum  309 . However, this gap is much smaller than the length of the cage  301  so that the cage does not tilt into the gap during delivery. Once the cage  301  is in position inside the infuser, the hook  320  is disconnected and the doors of the infuser  321  and  322  are returned to a closed, sealed position. Next, the pump  329  is used to pump water into the infuser  302  so that it substantially covers the fruit in the cage  301  but does not completely fill the space inside the infuser  302 . A certain amount of air is left at the top of the infuser, so that the vacuum pump  328 , which is configured to pump air, can operate.  
     [0127] During this period, the pressure relief valve  326  is kept open to allow air displaced by the water to flow out. Subsequently, the pressure release valve  326  is closed. The processor  327  then controls the vacuum pump  328  to reduce the pressure inside the infuser. The pressure is reduced until the vacuum sensor  325  indicates that pressure has reached a pressure in the range 0.5-0.6 bar below atmospheric. The pressure inside the infuser is maintained at this level for a period of about 30 seconds after which the processor  327  operates the vacuum pump  328  to pump the vacuum down to the pressure in the range 0.9-1.0 bar below atmospheric pressure. The fruit in the infuser is maintained at this pressure for approximately 1 minute. The processor  327  then operates the vacuum release valve  327  to release the vacuum slowly over a period of approximately 30 seconds.  
     [0128] Then, the pressure relief valve  326  is opened and the pump  329  is used to pump more water into the infuser  302 , substantially filling the infuser and driving any remaining air out through the pressure relief valve  326 . The pressure relief valve  326  is then closed again and water under pressure is pumped into the vessel until the pressure sensor  324  measures a pressure in the range 45 bar. The fruit in the vessel is retained in the water under pressure for of period about 10 seconds, after which the central processor  327  operates the valve  331  to return the water from the infuser  302  to the tank  330 . The relief valve  326  is opened to allow air to replace the water being pumped out of the infuser  302 . During this operation, air in the air sacs in the albedo portions of the citrus fruit is removed and replaced with dilute aqueous solution of enzyme which begins to soften and hydrolyse the albedo. During this operation, the weight of the fruit may increase by 30%. When all of the water has been removed from the infuser, the door  321  is opened and the hook  320  engaged with the cage  301  to draw it into the tilting drum  317 . Any remaining water in the fruit will drain out during this operation. Then rollers  314  are operated to rotate the drum substantially through a quarter rotation to the position shown in FIG. 16 so that the infused citrus fruit are poured out through the open top into a hopper (not shown).  
     [0129] The fruit thus treated is then passed to the peeler which is described further with relation to FIG. 17. FIG. 17 is a schematic side view of a peeler according to the invention. Citrus fruit are fed into the peeler at the top left hand comer of FIG. 17 and are fed out, when finished, to the bottom right hand corner. The peeler  500  comprises a frame  501  on which there are mounted, in succession, a first feed chute  502 , a first peeling means  503 , a second feed chute  504 , a second peeling means  505 , a third feed chute  506  and a third peeling means  507 .  
     [0130] The first and second feed chutes  502 ,  504  each comprise a short channel dimensioned to receive citrus fruit stacked in a line, one at a time. At the end of the chute there is a feed paddle  508 , which comprises four blades mounted at equal spaces around an axle. The axle is horizontally mounted with the blades extending through a slot in the bottom of the chute  502 ,  504 . Upon making a single quarter turn, a single citrus fruit is allowed to pass the paddle  508 .  
     [0131] Each peeling station comprises a peeling ring  509  which is located in a position to receive a citrus fruit fed by the paddle  508  or chute  506 . The peeling rings  509  are represented as being elliptical in FIG. 17, being viewed in perspective. FIG. 18 shows a plan view of a peeling ring  509 . The ring  509  comprises an annular ring formed out of sheet silicone rubber material of thickness 3 mm. The central opening  510  is dimensioned to be slightly smaller than the external dimensions of the fruit portion of citrus fruit. Because the fruit fed into the apparatus will have been graded first of all so that their size fall within a small range, it is possible to select a central aperture of size which allows the albedo and peel portions of the fruit to be stripped from the fruit portion without unnecessarily compressing and damaging the fruit portion. Preferably, the apertures  509  of the successive peeling rings become slightly smaller in succession.  
     [0132] In order to provide added flexibility to the peeling ring, it may be pierced at regular intervals by holes  511  extending through the sheet material. The holes are suitably of radius 3 mm.  
     [0133] In use, the diameter of the aperture  510  will be selected according to the size range of citrus fruit being processed. In order to process citrus fruit of a different diameter, a second peeler (not shown) may operate in parallel to the peeler  500  to FIG. 17.  
     [0134] In use, once a citrus fruit is fed into the ring  509 , it is pressed through the ring by a plunger  512  operated by a pneumatic cylinder  513 . The pneumatic cylinder is operated to first of all push the fruit through the ring and then retract to a position which will allow a second citrus fruit to be fed to the peeling ring  509 . As a result of stripping the albedo and peel portion from the fruit portion, the peeled material may remain on the peeling ring  509 . To remove such material, a plurality air or water jets  514  are provided located around a substantial part of the periphery of the peeling ring. On one side of the peeling ring  509 , there is a chute  515  for accepting peeled material. The chute  515  may lead to a collector (not shown). A vacuum means may be provided for drawing peeled material along the chute  515 . Once a citrus has been pushed through the ring, before the piston is retracted, the jets are switched on so that any peeled material is blown into the chute  515  thereby clearing the ring. While the jets are on, the piston is retracted. In this way, any material adhering to into the piston is also removed.  
     [0135] The cycle is shown in greater detail in FIG. 19. In step S 501 , the feeder is rotated through a quarter turn to feed one fruit. In S 502 , the fruit is driven through the peeler ring by the piston  512 . In step S 503 , the jet is switched on to remove peeled material. In step S 504 , the piston is retracted. Finally, in step S 505  the jet is switched off and the cycle returns to the beginning.  
     [0136] The first two peeling stations  503  and  505  are substantially identical. The last peeling  507  is slightly different in that it is arranged so that the piston  512  travels in a substantially horizontal direction. A final collection chute for the peeled citrus  516  is provided at the bottom right hand corner of the FIG. 17.  
     [0137] After peeling, the fruit is segmented. The segmenting operation comprises a first step in which the fruit is cooled in a chiller which is operated for example by solid carbon dioxide or liquid nitrogen. As a result of the chilling operation, the surface of the fruit is chilled to a temperature of −2° C. and the interior of the fruit reaches a temperature around 2° C. Any conventional form of a chiller may be used. After chilling, the fruit is passed to a segmenting apparatus  602  which is shown in FIG. 20. The fruit is fed into the segmenter from the top right hand side and passes from right to left through the apparatus. A feed chute and feeder  603  is provided which is the same in design and operation as the chute and feeder  502  and  508  of FIG. 17.  
     [0138] The segmenting apparatus comprises a continually travelling belt  604 , the top run of which travels from right to left. It has a surface treated, for example by roughening, to improve frictional grip with the citrus fruits  605 . Above the belt  604  there is a contoured pressure bar  606 . The underside of the bar is contoured with a concave surface, which defines a channel for guiding the fruit. At the right hand end of the pressure bar, the space between the pressure bar and the top of the belt is greater than the size of the citrus fruit. The pressure bar is inclined so that at its left hand end, the distance between the belt and the pressure bar is much smaller than the average size of the citrus fruit being fed. In this way, as the fruit is fed along by the belt  604 , it is progressively compressed. The bottom surface of the pressure bar  607  is treated with a frictional material to ensure that the fruit  605  are rotated as they are fed. Further, a piston  608  is provided for cyclically oscillating the pressure bar  606  about a pivot  609 . In this way, the citrus fruits are submitted to varying pressure as they are rotated and fed from right to left. The frequency of oscillation is suitably around about 1 Hz. For different sizes of fruit, the position of the pivot  609  may be raised and lowered by the apparatus  610 .  
     [0139] As a result of passing the fruit through the segmenter  602 , the fruit may be progressively pummelled and rolled, leading to a partial or complete separation of the segments. Final preparation of the segments may be achieve by hand, if necessary.  
     [0140] Returning to FIG. 4, fruit segments are subsequently passed to the finishing operation. In the finishing operation, the fruit segments are first of all treated in an acid bath, to dissolve any remaining albedo material which adheres to the fruit segments and to deactivate any enzyme which remains in the fruit segments. A feed arrangement which allows the fruit to be collected from the acid bath, drained and then fed to the next stage  711  is provided. Suitable arrangements are well known in the art and it will not be described further. After passing through the acid bath, the fruit is fed to an alkali bath . 720  filled with dilute alkaline solution for neutralising any remaining acid appearing to the surface of the fruit segments.  
     [0141] The acid bath suitably comprises dilute citric acid and dilute hydrochloric acid. A suitable bath may be provided by a mixture in proportions 100 ml to 200 ml of cold water to 1 gm of citric acid crystals E(330): 5 ml of dilute hydrochloric acid (E507). The pH of the solution is preferably 0.88 but can be as high as 0.91. The bath may be at elevated temperature. A heater may be provided to maintain the bath at 30-60° C.  
     [0142] The alkali bath  720  comprises sodium hydroxide (1%). The alkali solution may be prepared by mixing in the proportion 1 gm sodium hydroxide crystals E(524): 100 ml of water. The alkali bath may also be maintained at a raised temperature in the range 30° C.-60° C. A draining conveyor  721  is provided to remove the fruit segments from the alkali bath  720  and feed it to a cold water bath for cooling the fruits  722 . A third draining conveyor  723  is provided for collecting the fruit segment from the cold water bath and passing them to a rinse  724 . A fourth draining conveyor  725  is provided for lifting the fruit segments from the rinsing bath and transferring them to a second chilled water bath  726  maintained at a temperature 0° C.-2° C. A fifth draining conveyor  726  is provided for lifting the fruits segments from the second chilled water bath  726  and passing them beneath air knives  727  for removing excess moisture. The segments then pass on the conveyor  726  below a mister  728  under which the segments are coated with a mist of ascorbic acid 0.5% and citrus oil 0.5% in water, before packing.  
     [0143] The present invention has been described above by way of example only and modifications can be made within the invention. The invention also extends to equivalents of the features described. The invention also consists in any individual features described or implicit herein or shown or implicit in the drawings or any combination of any such features or any generalisation of any such features or combination.