AU2013204221A1 - Inhibiting Browning Of Cut Fruit And Vegetables - Google Patents

Abstract

A method 154 for inhibiting enzymatic browning of food comprises steam blanching the food 148, and cooling 149, 150 the steam blanched food. The food is steam blanched by operating a steam source to produce steam to steam blanch the food, and inhibiting a liquid that is condensed from the steam from contacting the food. Figure 5 23 FIGURE 1 22 stear 52 60 61 31 U30 50 71 -51 out aeed 20 ---------------- 24- u 53-J-- 61 6 2223 52 \0 V1ater Fir VS Drive 52 60 22606150 51 51 50 25 an24 53 53 1 40 40 /26 27\ 22 23 40 40 FIGURE 2 FIGURE 3

Description

1 INHIBITING ENZYMATIC BROWNING OF FOOD FIELD OF THE INVENTION [0001] The present invention relates generally to inhibiting browning of food and, in particular, to inhibiting enzymatic browning of food. [0002] Although the present invention will be described with particular reference to inhibiting enzymatic browning of fresh avocado that has been cut, it will be appreciated that it may be used to inhibit enzymatic browning of other foods. For example, it may be used to inhibit enzymatic browning of other fruit and vegetables which are susceptible to such browning. BACKGROUND ART [0003] The process of food becoming brown is known as browning. Browning of foods may be desirable, as in caramelisation, or undesirable, as in an avocado turning brown after being cut. Foods, including beverages, can turn brown through either enzymatic or non-enzymatic processes. [0004] Enzymatic browning is a chemical process, involving polyphenol oxidase, catechol oxidase and other enzymes that create melanins and benzoquinone from natural phenols, resulting in a brown colour. Enzymatic browning general requires exposure to oxygen, thus the browning that occurs when an avocado, for example, is cut. [0005] Contrary to enzymatic or oxidative browning, non-enzymatic browning is a chemical process that produces a brown colour in foods without the activity of enzymes. The two main forms of non-enzymatic browning are caramelisation and Maillard reaction. Both vary in reaction rate as a function of water activity. [0006] Caramelisation is the pyrolysis of sugar. It is used extensively in cooking for the resulting nutty flavor and brown colour. As the process occurs, volatile chemicals are released, producing the characteristic caramel flavor. [0007] The Maillard reaction is a chemical reaction between an amino acid and a reducing sugar, usually requiring the addition of heat. The sugar interacts with the amino acid, producing a variety of odours and flavours.

2 [0008] Although enzymatic browning can be beneficial for developing flavor in tea, and developing colour and flavor in dried fruit such as figs and raisins, it is often detrimental to fresh fruit and vegetables, including avocados, apples, potatoes, and bananas. Such detrimental browning has an important economic cost causing deterioration of the value of affected food products in the food market. [0009] As a result of enzymatic browning, avocados turn brown quickly after being cut. Consequently, avocados need to be consumed within a short timeframe of being peeled and cut. This is a significant problem particularly for food service and quick service restaurant (QSR) operators worldwide, and is an inconvenience for retail consumers. [0010] A variety of techniques currently exist for preventing enzymatic browning. Each technique exploits a different aspect of the biochemical process. One such technique involves the use of lemon juice and other acids to lower the pH and remove the copper cofactor necessary for the responsible enzymes to function. However, the use of lemon juice and acids can affect the taste and appearance of the treated food. [0011] Low temperatures can also prevent enzymatic browning by reducing rate of reaction. This usually requires cooling equipment which can be expensive to purchase and operate. Also, the treated food can be damaged if it is not cooled correctly. [0012] Inert gas, such as nitrogen, can be used to prevent food from reacting with oxygen. This usually requires specialist equipment for treating food in an inert atmosphere. Like cooling equipment, such equipment can be expensive to purchase and operate. It also requires a supply of inert gas which adds to the cost of employing this treatment technique. [0013] Chemicals such as sodium bisulfite and citrates can be used to treat food to prevent it from undergoing enzymatic browning. However, the use of such chemicals can, like lemon juice and acids, affect the taste and appearance of the treated food. [0014] Blanching can be used to denature enzymes and destroy responsible reactants. Blanching is a cooking process wherein the food substance, usually a 3 vegetable or fruit, is plunged into boiling water, removed after a brief time interval, and finally plunged into iced water or placed under cold running water to halt the cooking process. [0015] An example of a known process that uses blanching to inhibit enzymatic browning of cut avocado is disclosed in "A Process to Prevent Browning of Frozen Avocado Halves and Chunks", Bower J. P. & Dennison M. T., South African Avocado Growers Association: http://www.google.com.au/url?sa=t&rct=j&q=a+process+to+prevent+browning+of +frozen+avocado+halves+and+chunks&source=web&cd=1 &cad=rja&ved=0CC8 QFjAA&url=http%3A%2F%2Fwww.avocadosource.com%2FJournals%2FSAAG A%2FSAAGA 2005%2FSAAGA 2005 V28 PGS 40 41 Bower. pdf&ei=XqFfUevgCJCtiQe0j4HADw&usg=AFQiCN EXJa4PQ xiSDTn CliBn5zuMZmdVq&bvm=bv.44770516,d.aGc. According to the disclosed process, after avocado fruit has been ripened to the correct softness, it is cleaned externally with a microbial disinfectant, peeled and sliced, and then dipped into boiling water for sufficient time to inactivate the browning enzyme polyphenol oxidase (PPO), as well as to leach phenolics from the cut surface of the fruit. The latter supposedly prevents enhanced flavor and bitterness associated with storage of frozen avocado. Thereafter, the fruit is rapidly frozen in liquid nitrogen, packed and stored. According to the document, on defrosting, the treatment was shown to be highly effective, in that fruit browning did not occur for a number of hours after defrosting. [0016] A problem with using blanching to inhibit enzymatic browning of food is that the water that contacts the food can remove natural oils and juices from the food which can adversely affect the colour, taste, and/or other characteristics of the treated food. [0017] Chinese Patent Publication No. CN 101 558782A discloses a method for enzyme inactivation of longan flesh by steam blanching. As part of the method, fresh longans are cleaned and any rotten parts of the longans are removed. The shells and stones of the cleaned longans are then removed to obtain longan flesh. The longan flesh is then treated with steam at a temperature of 80-1 00C for 1-3 minutes, and is then rapidly co oled to a room temperature of about 25C. The steam treatment step involves pass ing steam generated by a 4 steam generation device directly into a receptacle containing longan flesh. The cooling step involves loading the steam treated longan flesh into a receptacle with a jacket, and then passing a cooling medium such as tap water or iced water through the jacket. According to the document, enzyme inactivation by steam blanching causes the endogenous enzymes of the longan flesh to be inactivated, preventing enzymatic browning of the longan flesh by the endogenous enzyme system. The document also claims that, since the steam avoids contact between the longan flesh and water, the loss of water-soluble substances is reduced, while the low-pressure oxygen-deficient environment created by the steam flavours preservation of the natural colour, lustre and flavor of the longan flesh, avoiding the emergence of undesirable "green" and "cooked" flavours in the course of longan flesh processing. [0018] Although the longan flesh may not be contacted by liquid water as the steam is passed directly into the receptacle containing the longan flesh, once the steam has passed into the receptacle it may condense into a liquid that may contact the longan flesh. If the liquid were to contact the longan flesh it would remove natural oils and juices from the longan flesh and adversely affect its colour, taste, and/or other characteristics. [0019] Furthermore, rapidly cooling the treated longan flesh to room temperature will not preserve the treated longan flesh for an extended period of time. [0020] It would be desirable to be able to treat cut avocado so as to inhibit enzymatic browning thereof without adversely affecting the colour, taste, texture, and/or other characteristics of the treated avocado. It would also be desirable to be able to preserve the treated avocado for an extended period of time without adversely affecting its colour, taste, texture, and or other characteristics. [0021] It is against this background that the present invention has been developed. SUMMARY OF THE INVENTION [0022] It is an object of the present invention to overcome, or at least ameliorate, one or more of the deficiencies of the prior art mentioned above, or to provide the consumer with a useful or commercial choice.

5 [0023] Other objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, a preferred embodiment of the present invention is disclosed. [0024] According to a first broad aspect of the present invention there is provided a steam blancher for steam blanching food, the steam blancher comprising a steam source for producing steam to steam blanch food, the steam blancher being adapted such that a liquid that is condensed from the steam is inhibited from contacting the food. [0025] By inhibiting the liquid that is condensed from the steam from contacting the food, the steam blancher is able to inhibit the liquid from removing natural oils and juices from the food and adversely affecting the colour, taste, and/or other characteristics of the food. [0026] Preferably, the steam blancher is for steam blanching fruit and/or vegetables. It is particularly preferred that the steam blancher is for steam blanching cut fruit and/or vegetables. According to a particular preferred embodiment, the steam blancher is for steam blanching cut avocado. [0027] Preferably, the steam source comprises a vessel for holding a liquid, and a heat source for heating the liquid so that the liquid is evaporated into steam. Preferably, the vessel comprises a tray. Preferably, the vessel comprises a filler for enabling the vessel to be filled with liquid. Preferably, the vessel comprises a drain for enabling the liquid to be drained from the vessel. [0028] Preferably, the heat source comprises a heatable tube. Preferably, the tube is able to be heated by passing steam through it. [0029] Preferably, the liquid comprises water. It is preferred that the water does not contain any chemical additives. [0030] Preferably, the steam blancher also comprises a plurality of legs for supporting the vessel. [0031] Preferably, the steam blancher also comprises a support for supporting the food. Preferably, the support is adapted to support the food above the steam source. Preferably, the support is adapted so that steam from 6 the steam source is able to pass through the support. Preferably, the support comprises a belt conveyor that is able to move the food along the steam blancher. Preferably, the belt conveyor comprises a variable speed drive that is able to vary the speed at which the food is moved along the steam blancher. Preferably, the belt conveyor comprises a mesh belt for supporting the food. [0032] Preferably, the steam blancher also comprises a canopy located above the steam source for inhibiting the steam from escaping from the confines of the steam blancher. Preferably, the canopy is adapted so that liquid on the canopy that is condensed from the steam is inhibited from contacting the food. Preferably, the canopy comprises a peaked canopy that is able to direct the liquid on it away from the food. Preferably, the peaked canopy is able to direct the liquid on it to return to the steam source without contacting the food. [0033] According to a second broad aspect of the present invention there is provided a method for steam blanching food, the method comprising: operating a steam source to produce steam to steam blanch food; and inhibiting a liquid that is condensed from the steam from contacting the food. [0034] Preferably, the method is for steam blanching fruit and/or vegetables. It is particularly preferred that the method is for steam blanching cut fruit and/or vegetables. According to a particular preferred embodiment, the method is for steam blanching cut avocado. [0035] Preferably, the operating step comprises heating liquid held in a vessel so that the liquid is evaporated into steam. Preferably, the heating step comprises heating a heat source so that the heating source heats the liquid. Preferably, the step of heating the heat source comprises heating a heatable tube. Preferably, the step of heating the heatable tube comprises passing steam through the tube. [0036] Preferably, the liquid comprises water. It is preferred that the water does not contain any chemical additives. [0037] Preferably, the method also comprises supporting the vessel.

7 [0038] Preferably, the method also comprises supporting the food on a support. Preferably, the supporting step comprises supporting the food above the steam source. Preferably, the food is supported so that steam from the steam source is able to pass through the support. Preferably, the supporting step comprises supporting the food on a belt conveyor. Preferably, the method also comprises moving the food with the belt conveyor. Preferably, the speed at which the food is moved by the belt conveyor is able to be varied. [0039] Preferably, the method also comprises using a canopy to inhibit the steam from escaping. Preferably, the inhibiting step comprises liquid on the canopy that is condensed from the steam being inhibited by the canopy from contacting the food. Preferably, the step of the canopy inhibiting the liquid on it from contacting the food comprises the canopy directing the liquid away from the food. Preferably, the canopy is able to direct the liquid to return to the steam source without contacting the food. [0040] According to a third broad aspect of the present invention there is provided an apparatus for inhibiting enzymatic browning of food, the apparatus comprising a steam blancher according to the first broad aspect of the present invention, and a cooler for cooling food that is treated with the steam blancher. [0041] Preferably, the apparatus is for inhibiting enzymatic browning of fruit and/or vegetables. It is particularly preferred that the apparatus is for inhibiting enzymatic browning of cut fruit and/or vegetables. According to a particular preferred embodiment, the apparatus is for inhibiting enzymatic browning of cut avocado. [0042] Preferably, the cooler comprises a freezer for freezing the treated food. Freezing the treated food is advantageous in that it allows the food to be preserved for an extended period of time. Preferably, the freezer comprises a snap-freezer. Preferably, the freezer comprises a tunnel freezer. Preferably, the cooler also comprises a pre-cooler for cooling the treated food prior to the food being frozen by the freezer. Preferably, the pre-cooler comprises a tunnel pre cooler. Preferably, the pre-cooler uses coolant from the freezer to cool the food. Preferably, the coolant comprises carbon dioxide.

8 [0043] According to a fourth broad aspect of the present invention there is provided a method for inhibiting enzymatic browning of food, the method comprising steam blanching food using a method according to the second broad aspect of the present invention, and cooling the steam blanched food. [0044] Preferably, the method is for inhibiting enzymatic browning of fruit and/or vegetables. It is particularly preferred that the method is for inhibiting enzymatic browning of cut fruit and/or vegetables. According to a particular preferred embodiment, the method is for inhibiting enzymatic browning of cut avocado. [0045] Preferably, the cooling step comprises freezing the steam blanched food. Preferably, the freezing step comprises snap-freezing the steam blanched food. Preferably, the cooling step also comprises pre-cooling the steam blanched food prior to freezing the food. Preferably, the cooling step comprises using coolant from the freezing step to pre-cool the food. Preferably the coolant comprises carbon dioxide. [0046] According to a fifth broad aspect of the present invention there is provided an apparatus for processing food, the apparatus comprising a cutter for cutting the food, and an apparatus for inhibiting enzymatic browning of the food according to the third broad aspect of the present invention. [0047] Preferably, the apparatus is for processing fruit and/or vegetables. It is particularly preferred that the apparatus is for processing avocado. [0048] Preferably, the cutter comprises a mechanical slicer and/or dicer for slicing and/or dicing the food. [0049] Preferably, the apparatus also comprises an accumulation table for storing food that is suitable for further processing. [0050] Preferably, the apparatus also comprises a preparation station where the food is able to be prepared for further processing. [0051] Preferably, the apparatus also comprises a packaging station for packaging the processed food.

9 [0052] Preferably, the apparatus also comprises an accumulation table for storing the packaged food. [0053] Preferably, the apparatus also comprises a freezer for storing the packaged food. [0054] According to a sixth broad aspect of the present invention there is provided a method for processing food, the method comprising the steps of: cutting the food; and using a method for inhibiting enzymatic browning of the food according to the fourth broad aspect of the present invention. [0055] Preferably, the method is for processing fruit and/or vegetables. It is particularly preferred that the method is for processing avocado. [0056] Preferably, the cutting step comprises slicing, dicing, cutting into chunks, or halving the food. [0057] Preferably, the method also comprises testing the food to determine if it is suitable for further processing. [0058] Preferably, the method also comprises storing the tested food. [0059] Preferably, the method also comprises manually preparing the food. Preferably, the step of manually preparing the food comprises halving, pitting, and/or peeling the food. [0060] Preferably, the method also comprises packaging the processed food. [0061] Preferably, the method also comprises storing the packaged food. Preferably, the step of storing the packaged food comprises freezing the packaged food. [0062] Preferably, the method also comprises coating the cut food. For example, if the food is avocado that has been sliced, a Tempura coating may be applied to the sliced avocado to produce Tempura sliced avocado.

10 BRIEF DESCRIPTION OF THE DRAWINGS [0063] In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawings, in which: Figure 1 is a plan view of steam blancher for steam blanching avocado; Figure 2 is a side view of the steam blancher; Figure 3 is an end view of the steam blancher; Figure 4 is a schematic diagram of an apparatus for processing avocado; and Figure 5 is a flow chart of a method for processing avocado. DESCRIPTION OF EMBODIMENTS [0064] Referring to figures 1 to 3, there is depicted a steam blancher 20 for steam blanching fresh avocado that has been cut into pieces. Steam blancher 20 includes a steam source 21 for producing steam to steam blanch cut avocado. Steam blancher 20 is adapted such that a liquid that condensates from the steam is inhibited from contacting the cut avocado so that the liquid is inhibited from removing natural oils and juices from the avocado and adversely affecting its colour, taste, and/or other characteristics. [0065] A vessel 22 of the steam source 21 includes a tray 23 for holding a liquid that the steam source 21 is able to evaporate into steam. Vessel 22 also includes a filler 24 for enabling the tray 23 to be filled with liquid, and a drain 25 for allowing the liquid in the tray 23 to be drained therefrom. [0066] A heat source 26 of the steam source 21 is able to heat the liquid in the tray 23 to a sufficiently high temperature so that the liquid is evaporated into steam. The heat source 26 includes a heatable stainless steel tube 27 that is able to be heated by passing steam through it and that has a diameter of a quarter of an inch. One end of the tube 27 is connected to a steam inlet 30 that is connected to an outlet of a boiler (not depicted) so that steam produced by the boiler is able to flow into the tube 27 through the inlet 30. The other end of the tube 27 is connected to a steam outlet 31 that is connected to an inlet of the boiler so that the steam that flows into the tube 27 through the inlet 30 is able to flow out of the tube 27 and back to the boiler through the outlet 31. As the steam 11 from the boiler flows through the tube 27, heat is transferred from the steam to the tube 27. The heat that is transferred to the tube 27 is in turn transferred to the liquid in the tray 23 so that the heated liquid evaporates into steam. [0067] The liquid that is placed in the tray 23 is cold potable water that does not contain any chemical additives so that the steam produced from the water by the steam source 21 also does not contain any such additives. [0068] Tray 23 is supported on a support surface (not depicted) such as a ground surface by a plurality of legs 40 that extend downwardly from the bottom of the tray 23 and rest on the support surface. [0069] Steam blancher 20 also includes a support 50 in the form of a belt conveyor 51 for supporting the cut avocado. The belt conveyor 51 is positioned above the steam source 21 so that the avocado supported by the conveyor 51 is in turn supported above the steam source 21. The belt conveyor 51 includes a mesh belt 52 for supporting the avocado. Belt 52 extends along the length of the steam source 21. As it rises from the tray 23, steam produced by the steam source 21 is able to pass through the mesh belt 52 and around the avocado pieces supported by the belt 52. Belt conveyor 51 is able to move the avocado supported by the belt 52 along the steam source 21. A variable speed drive 53 of the belt conveyor 51 is able to vary the speed at which the avocado supported by the belt 52 is able to be moved along the steam source 21 by the conveyor 51. [0070] A peaked canopy 60 in the form of a lid 61 rests on the tray 23 and covers a middle portion of both the tray 23 and the belt conveyor 51 so that the canopy 60 and the tray 23 define a tunnel 62 through which the conveyor 51 extends. Canopy 60 inhibits steam from escaping from the confines of the tray 23. Steam that condenses into liquid on the underside of the canopy 60 is directed by the canopy 60 to return to the tray 23 without contacting avocado on the conveyor belt 52. In particular, the liquid is able to flow along the underside of the canopy 60 under the influence of gravity until it flows into the tray 23 where it can again be evaporated into steam. [0071] Avocado pieces supported by the belt conveyor 51 are able to be moved through the steam blancher 20 between the tray 23 and the canopy 60 by 12 operating the variable speed drive 53 so that the conveyor belt 51 and therefore the avocado pieces are moved along the tray 23 between the tray 23 and the canopy 60. [0072] To steam blanch pieces of fresh avocado using the steam blancher 20, the avocado pieces are placed on the conveyor belt 52 at an in-feed side 70 of the conveyor 51. The conveyor 51 is operated so that the avocado is moved along the conveyor 51 by the belt 52, through the tunnel 62, and then off the belt 52 at an out-feed side 71 of the conveyor 51. As the avocado travels through the tunnel 62 it is blanched by steam that is produced by operating the steam source 21. Steam from the steam source 21 that condenses on the underside of the canopy 60 flows along the underside of the canopy under the influence of gravity without contacting the avocado on the belt 52 until the liquid returns to the tray 23. [0073] Steam produced by the steam source 21 is low pressure, 'wafting', steam. This is very different to other existing steam blanchers which use high pressure steam for operations such as skinning operations on fruit. [0074] Although the steam blancher 20 is an in-line steam blancher that can process fruit pieces continuously, a batch-type steam blancher 20 that does not utilise a conveyor belt could be employed to steam blanch batches of avocado pieces. [0075] Referring to figure 4, steam blancher 20 is part of an apparatus 80 for inhibiting enzymatic browning of cut avocado. In addition to the steam blancher 20, the apparatus 80 includes a cooler 81 for cooling avocado that is treated by the steam blancher 20. Cooler 81 includes a pre-cooler 82, and a freezer 83 in the form of an Individual Quick Frozen (IQF) tunnel snap-freezer 84. Pre-cooler uses carbon dioxide coolant from the freezer 83 to cool the steam blanched food. [0076] In turn, the apparatus 80 is part of an apparatus 100 for processing food. In addition to the apparatus 80, the apparatus 100 includes an accumulation table 101 where avocados that pass quality assurance ripeness requirements are placed to await further processing. Apparatus 100 also includes a first station 103 where avocados from the table 101 are manually prepared by being manually halved, pitted, and peeled. An in-feed conveyor 104 13 is operable to transfer manually prepared avocado to a second station 105. The second station 105 is a cutter 106 in the form of a mechanical slicer and/or dicer 107 that is able to slice and/or dice the avocado that is fed to it by the conveyor 104. An out-feed conveyor 108 is operable to feed the sliced and/or diced avocado directly onto the in-feed conveyor 51 of the steam blancher 20 which comprises a third station 109 of the apparatus 100. An in-feed conveyor 110 is operable to feed steam blanched avocado to the pre-cooler 82 which comprises a fourth station 111 of the apparatus 100. Pre-cooled avocado is able to be fed directly from the pre-cooler 82 to an in-feed conveyor 112 of the freezer 83 which is a fifth station 113 of the apparatus 100. An out-feed conveyor 114 is operable to transfer frozen avocado from the freezer 83 to a sixth station 115 where the frozen avocado is packaged. Apparatus 100 also includes an accumulation table 116 to which the packaged avocado is able to be transferred. From the table 116, the packaged avocado can then be placed in cartons 117 which are transferred to a seventh station 118 of the apparatus 100 which comprises a freezer (not depicted). [0077] Referring to figure 5, a method 140 for processing avocado utilises the apparatus 100. The method 140 is able to inhibit enzymatic browning of cut pieces of fresh avocado, freeze the pieces for long storage life so that they will have extensive shelf life once thawed, whilst maintaining the unique eating qualities of fresh-cut avocado. Utilisation of the method 140 allows for the commercial production of cut avocado pieces and their packaging into retail or food service packaging for sale worldwide. [0078] At step 141 of the method 140, whole avocados are graded to select a specific ripeness (by use of a penetrometer) and stored in a cold-room, ready for processing. Lower grade fruit that would have otherwise not been selected for standard retail opportunities can still be processed using the method 140, subject to that fruit meeting certain grading criteria. [0079] Graded and stored fruit is transferred from the cold-room to the accumulation table 101 at step 142. Then, at the first station 101, the whole avocados transferred to the table 101 are, at step 143, manually sliced in half using a sharp knife. The halved fruit is then manually pitted 144, and the pits discarded. Peeling 145 is achieved by scooping the mesocarp from the avocado 14 skin and placing it cut-face down on the in-feed conveyor 104 to the mechanical slicer and/or dicer 107. All waste products are removed from the factory/disposed of in an appropriate manner. [0080] At the second station 105 that includes the mechanical slicer and/or dicer 107, mechanical slicing and/or dicing is used to cut 146 the mesocarp halves into the desired cut type. The mesocarp is fed through a series of rotating blades with the resulting cut pieces of mesocarp extracted onto the out-feed conveyor 108. Care is required to ensure the cut pieces are separated from each other before entering the steam blancher 20. Hence, the method 140 includes a grading step 147 before the cut pieces enter the steam blancher 20. [0081] After grading 147, the cut pieces are steam blanched 148 by the steam blancher 20 at the third station 109. The purpose-built steam blancher 20 is specifically designed to deliver a known volume and pressure of steam at the correct zonal temperature with sufficient turbulence to achieve the desired allover contact of steam with the individual pieces of avocado as they travel through the tunnel 62 of the steam blancher 20. Efforts are made during the blanching process to minimise any liquid water (condensed steam or any other liquid water) coming in direct contact with the avocado pieces, as this will create off flavor notes in the final avocado product. Avocado pieces are fed from the mechanical slicer and/or dicer directly onto the in-feed conveyor 51 of the blancher 20. Belt speed of the conveyor 51 is calculated from the size of the average avocado piece and density of avocado pieces on the conveyor belt 52, and will vary depending on these two parameters. The belt speed is able to be varied by suitably operating the variable speed drive 53 of the blancher 20. The total amount of time avocado pieces are exposed to the steam environment of the steam blancher 20 is critical to achieving the desired outcome of inhibiting the impact of the browning enzyme polyphenol oxidase (PPO) but not exposing the pieces for so long that they tend to cook. The elements of the steam blancher 20 and its operation that are critical to achieving the desired outcome include the pressure of the boiler that provides steam to the heatable tube 27 of the blancher 20, the length of the conveyor 51, the time that the avocado pieces spend in the steam blancher 20, the maximum and minimum temperatures inside the blancher 20. The values of these elements will vary with the size of the steam blancher 15 20, and also with the fruit variety that is being blanched (e.g. Hass avocados versus Shepard avocados versus Reed avocados, etc.). As regards the maximum and minimum temperatures inside the blancher 20, it has been found that good results are achieved if these temperatures are chosen so that the temperature of the steam at the surface of the fruit pieces is between 95C and 99C. [0082] Upon exiting the blanching tunnel 62, the avocado pieces need to be cooled as soon as practical to remove internal heat and limit the ongoing cooking effect. A pre-cooling step 149 is introduced prior to freezing the avocado pieces, to lower the heat coefficient and increase freezing efficiency. The steam blanched avocado pieces are fed onto the in-feed conveyor 110 which passes the pieces through a cooling tunnel of the pre-cooler 82 at the fourth station 111. The pre-cooling step 149 is predicated primarily on commercial reasoning to lower the coolant gas usage cost of IQF freezing 150 at the subsequent station (i.e. the fifth station 113). [0083] The method of freezing 150 is another critical aspect to the overall method 140. The primary goal is to freeze the avocado pieces as fast as possible to minimise water crystallization of their cut surfaces and produce a final product that resembles all the organoleptic characteristics of fresh-cut avocado. To achieve this, IQF freezing technology is used, with carbon dioxide identified as the preferred freezing gas/coolant. Avocado pieces are fed directly from the pre-cooler 82 onto the in-feed conveyor 112 of the IQF tunnel snap-freezer 83 and travel through the tunnel in a predetermined time. The belt speed of the conveyor 112 can be approximated to that of the blancher 20, thereby creating an efficient in-line process flow. Essential to the freezing process is to create a 'crust' freeze on each avocado piece. Further internal (core) freezing can take place later in the storage blast freezer at the seventh station 118. Satisfactory crust freezing will limit the extent of avocado pieces sticking to each other, which is an important aspect of the final product offering. [0084] The frozen avocado is transferred by the out-feed conveyor 114 to the sixth station 115 where the avocado is packaged 151. The type of packaging and packaging equipment that is used at the packaging step 151 is not highly critical. However, two functional aspects that are desirable are to seal the 16 avocado pieces from ambient conditions to prevent risk of any form of contamination and to limit the exposure of the avocado pieces to UV light, which can cause pigment fading. Packaging choice is therefore largely determined by market demands and preferences and equipment employed in the factory/processing facility. [0085] At step 152 the packaged avocado is transferred to the accumulation table 116. [0086] From the accumulation table the packaged avocado is placed in cartons at step 153. After cartooning, the packaged frozen product needs to be stored in the freezer (the blast freezer mentioned earlier) at the seventh station 118 at or below a temperature of -1 8C. Thawed pro duct needs to be kept refrigerated at or below 4C. [0087] The steam blanching step 148, pre-cooling step 149, and freezing step 150 of the process comprise a method 154 for inhibiting enzymatic browning of avocado. [0088] The resultant frozen avocado product produced by using the method 140 shows no sign of any enzymatic browning or any other deleterious condition for several months, while kept in its frozen state. Independently frozen pieces of avocado remain separate from each other in their packaging, which allows for their easy removal from the packaging and subsequent use by the consumer or processor. [0089] Upon removal from the freezer, thawed avocado pieces show no sign of any enzymatic browning for 10-14 days, if kept refrigerated. Organoleptic characteristics such as flavor and odour are largely unaffected when compared to fresh-cut avocado. Texture can be slightly reduced, although the product still remains firm and easy to handle. Colour is slightly enhanced by the blanching process, improving its overall appeal. However, colour will fade over time if avocado pieces are exposed to UV light. [0090] In order to preserve the fruit, the method 140 does not rely on the use of any preservatives/anti-oxidants or any other agents that could interfere with the taste, mouth feel, texture, or bouquet of the fruit.

17 [0091] The method 140 allows the original nutritional and eating attributes of fresh fruit to be retained. [0092] Processing avocado in the manner described herein addresses the problem of avocado turning brown quickly after being cut and therefore having to be consumed within a short timeframe of being peeled and cut. The processed avocado is a ready to use, long shelf life offering which can remain in frozen storage until required for use. [0093] Although the steam blancher 20, apparatus 80, apparatus 100, and associated methods have been described herein with particular reference to the processing of avocado, it will be appreciated that the same or similar apparatus and methods can be used for processing other foods, including other fruit and/or vegetables. [0094] It will be appreciated by those skilled in the art that variations and modifications to the invention described herein will be apparent without departing from the spirit and scope thereof. The variations and modifications as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth. [0095] Throughout the specification and claims, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. [0096] Throughout the specification and claims, unless the context requires otherwise, the term "substantially" or "about", if used, will be understood to not be limited to the value for the range qualified by the terms. [0097] It will be clearly understood that, if a prior art publication is referred to herein, that reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

Claims (83)

1. A steam blancher for steam blanching food, the steam blancher comprising a steam source for producing steam to steam blanch food, the steam blancher being adapted such that a liquid that is condensed from the steam is inhibited from contacting the food.

2. The steam blancher defined by claim 1, wherein the steam blancher is for steam blanching fruit and/or vegetables.

3. The steam blancher defined by claim 2, wherein the steam blancher is for steam blanching cut fruit and/or vegetables.

4. The steam blancher defined by claim 3, wherein the steam blancher is for steam blanching cut avocado.

5. The steam blancher defined by any one of the preceding claims, wherein the steam source comprises a vessel for holding a liquid, and a heat source for heating the liquid so that the liquid is evaporated into steam.

6. The steam blancher defined by claim 5, wherein the vessel comprises a tray.

7. The steam blancher defined by any one of claims 5 to 6, wherein the vessel comprises a filler for enabling the vessel to be filled with liquid.

8. The steam blancher defined by any one of claims 5 to 7, wherein the vessel comprises a drain for enabling the liquid to be drained from the vessel.

9. The steam blancher defined by any one of claims 5 to 8, wherein the heat source comprises a heatable tube.

10. The steam blancher defined by claim 9, wherein the tube is able to be heated by passing steam through it.

11. The steam blancher defined by any one of the preceding claims, wherein the liquid comprises water.

12. The steam blancher defined by claim 11, wherein the water does not contain any chemical additives. 19

13. The steam blancher defined by any one of claims 5 to 10, wherein the steam blancher also comprises a plurality of legs for supporting the vessel.

14. The steam blancher defined by any one of the preceding claims, wherein the steam blancher also comprises a support for supporting the food.

15. The steam blancher defined by claim 14, wherein the support is adapted to support the food above the steam source.

16. The steam blancher defined by any one of claims 14 to 15, wherein the support is adapted so that steam from the steam source is able to pass through the support.

17. The steam blancher defined by any one of claims 14 to 16, wherein the support comprises a belt conveyor that is able to move the food along the steam blancher.

18. The steam blancher defined by claim 17, wherein the belt conveyor comprises a variable speed drive that is able to vary the speed at which the food is moved along the steam blancher.

19. The steam blancher defined by any one of claims 17 to 18, wherein the belt conveyor comprises a mesh belt for supporting the food.

20. The steam blancher defined by any one of the preceding claims, wherein the steam blancher also comprises a canopy located above the steam source for inhibiting the steam from escaping from the confines of the steam blancher.

21. The steam blancher defined by claim 20, wherein the canopy is adapted so that liquid on the canopy that is condensed from the steam is inhibited from contacting the food.

22. The steam blancher defined by claim 21, wherein the canopy comprises a peaked canopy that is able to direct the liquid on it away from the food.

23. The steam blancher defined by claim 22, wherein the peaked canopy is able to direct the liquid on it to return to the steam source without contacting the food.

24. A method for steam blanching food, the method comprising: operating a steam source to produce steam to steam blanch food; and 20 inhibiting a liquid that is condensed from the steam from contacting the food.

25. The method defined by claim 24, wherein the method is for steam blanching fruit and/or vegetables.

26. The method defined by claim 25, wherein the method is for steam blanching cut fruit and/or vegetables.

27. The method defined by claim 26, wherein the method is for steam blanching cut avocado.

28. The method defined by any one of claims 24 to 27, wherein the operating step comprises heating liquid held in a vessel so that the liquid is evaporated into steam.

29. The method defined by claim 28, wherein the heating step comprises heating a heat source so that the heat source heats the liquid.

30. The method defined by claim 29, wherein the step of heating the heat source comprises heating a heatable tube.

31. The method defined by claim 30, wherein the step of heating the heatable tube comprises passing steam through the tube.

32. The method defined by any one of claims 24 to 31, wherein the liquid comprises water.

33. The method defined by claim 32, wherein the water does not contain any chemical additives.

34. The method defined by any one of claims 28 to 31, wherein the method also comprises supporting the vessel.

35. The method defined by any one of claims 24 to 34, wherein the method also comprises supporting the food on a support.

36. The method defined by claim 35, wherein the supporting step comprises supporting the food above the steam source. 21

37. The method defined by any one of claims 35 to 36, wherein the food is supported so that steam from the steam source is able to pass through the support.

38. The method defined by any one of claims 35 to 37, wherein the supporting step comprises supporting the food on a belt conveyor.

39. The method defined by claim 38, wherein the method also comprises moving the food with the belt conveyor.

40. The method defined by claim 39, wherein the speed at which the food is moved by the belt conveyor is able to be varied.

41. The method defined by any one of claims 24 to 40, wherein the method also comprises using a canopy to inhibit the steam from escaping.

42. The method defined by claim 41, wherein the inhibiting step comprises liquid on the canopy that is condensed from the steam being inhibited by the canopy from contacting the food.

43. The method defined by claim 42, wherein the step of the canopy inhibiting liquid on it from contacting the food comprises the canopy directing the liquid away from the food. 43. The method defined by claim 43, wherein the canopy is able to direct the liquid to return to the steam source without contacting the food.

44. An apparatus for inhibiting enzymatic browning of food, the apparatus comprising a steam blancher as defined by any one of claims 1 to 23, and a cooler for cooling food that is treated with the steam blancher.

45. The apparatus defined by claim 44, wherein the apparatus is for inhibiting enzymatic browning of fruit and/or vegetables.

46. The apparatus defined by claim 45, wherein the apparatus is for inhibiting enzymatic browning of cut fruit and/or vegetables.

47. The apparatus defined by claim 46, wherein the apparatus is for inhibiting enzymatic browning of cut avocado. 22

48. The apparatus defined by any one of claims 44 to 47, wherein the cooler comprises a freezer for freezing the treated food.

49. The apparatus defined by claim 48, wherein the freezer comprises a snap freezer.

50. The apparatus defined by any one of claims 48 to 49, wherein the freezer comprises a tunnel freezer.

51. The apparatus defined by any one of claims 48 to 40, wherein the cooler also comprises a pre-cooler for cooling the treated food prior to the food being frozen by the freezer.

52. The apparatus defined by claim 51, wherein the pre-cooler comprises a tunnel pre-cooler.

53. The apparatus defined by any one of claims 51 to 52, wherein the pre cooler uses coolant from the freezer to cool the food.

54. The apparatus defined by claim 53, wherein the coolant comprises carbon dioxide.

55. A method for inhibiting enzymatic browning of food, the method comprising steam blanching food using a method as defined by any one of claims 24 to 43, and cooling the steam blanched food.

56. The method defined by claim 55, wherein the method is for inhibiting enzymatic browning of fruit and/or vegetables.

57. The method defined by claim 56, wherein the method is for inhibiting enzymatic browning of cut fruit and/or vegetables.

58. The method defined by claim 57, wherein the method is for inhibiting enzymatic browning of cut avocado.

59. The method defined by any one of claims 55 to 58, wherein the cooling step comprises freezing the steam blanched food.

60. The method defined by claim 59, wherein the freezing step comprises snap-freezing the steam blanched food. 23

61. The method defined by any one of claims 59 to 60, wherein the cooling step also comprises pre-cooling the steam blanched food prior to freezing the food.

62. The method defined by claim 61, wherein the cooling step comprises using coolant from the freezing step to pre-cool the food.

63. The method defined by claim 62, wherein the coolant comprises carbon dioxide.

64. An apparatus for processing food, the apparatus comprising a cutter for cutting the food, and an apparatus for inhibiting enzymatic browning of the food as defined by any one of claims 44 to 54.

65. The apparatus defined by claim 64, wherein the apparatus is for processing fruit and/or vegetables.

66. The apparatus defined by claim 65, wherein the apparatus is for processing avocado.

67. The apparatus defined by any one of claims 64 to 66, wherein the cutter comprises a mechanical slicer and/or dicer for slicing and/or dicing the food.

68. The apparatus defined by any one of claims 64 to 67, wherein the apparatus also comprises an accumulation table for storing food that is suitable for processing.

69. The apparatus defined by any one of claims 64 to 68, wherein the apparatus also comprises a preparation station where the food is able to be prepared for further processing.

70. The apparatus defined by any one of claims 64 to 69, wherein the apparatus also comprises a packaging station for packaging the processed food.

71. The apparatus defined by claim 70, wherein the apparatus also comprises an accumulation table for storing the packaged food.

72. The apparatus defined by any one of claims 70 to 71, wherein the apparatus also comprises a freezer for storing the packaged food.

73. A method for processing food, the method comprising the steps of: 24 cutting the food; and using a method for inhibiting enzymatic browning of the food as defined by any one of claims 55 to 63.

74. The method defined by claim 73, wherein the method is for processing fruit and/or vegetables.

75. The method defined by claim 74, wherein the method is for processing avocado.

76. The method defined by any one of claims 73 to 75, wherein the cutting step comprises slicing, dicing, cutting into chunks, or halving the food.

77. The method defined by any one of claims 73 to 76, wherein the method also comprises testing the food to determine if it is suitable for further processing.

78. The method defined by claim 77, wherein the method also comprises storing the tested food.

79. The method defined by any one of claims 73 to 78, wherein the method also comprises manually preparing the food.

80. The method defined by claim 79, wherein the step of manually preparing the food comprises halving, pitting, and/or peeling the food.

81. The method defined by any one of claims 73 to 80, wherein the method also comprises packaging the processed food.

82. The method defined by claim 81, wherein the step of storing the packaged food comprises freezing the packaged food.

83. The method defined by any one of claims 73 to 82, wherein the method also comprises coating the cut food.