NZ199533A - Process for treating apples with calcium chloride to reduce bitter pip - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number 1 99533 s 1/9533 NEW ZEALAND PATENTS ACT. ] 953 No . Prov No. 199 ,533 _ 20 January 1982 Date: J COMPLETE SPECIFICATION "PRODUCE TREATMENT PROCESS AND APPARATUS" ft! We, THE NEW ZEALAND APPLE AND PEAR MARKETING BOARD, a body corporate^ constituted under the Apple and Pear Marketing Act 1971 of 73-75 Cambridge Terrace, Wellington, New Zealand hereby declare the invention for which^/ we pray that a patent may be granted to /us, and the method by which it is to be performed, to be particularly described in and by the following statement:- la 199533 This invention relates to a produce treatment apparatus and pro- v ■ cess. More particularly it relates to an apparatus and process for the treatment of the condition known as bitter pit in apples but is not limited thereto.

Bitter pit is a physiological disorder of apples which has been known for over 100 years and has been particulary important over the past 50 years for some cultivars grown for export in Australia, New Zealand and South Africa. Reference to this condition and prior art methods for dreating it may be found, for example in N.Z.J. Agric. Res. 5,302-9. 2. 199 It is known that when apples are dipped after harvest into an aqueous solution of CaC^ the incidence of bitter pit is reduced. It is also known that with some varieties of apples the treatment is enhanced by dipping in a vessel under either elevated or reduced pressure. It is advantageous to optimise the process parameters and to develop an automatic apparatus to provide the most efficient uptake of the CaCl^ solution.

It is an object of this invention to go some way toward achieving this desideratum or at least to offer the public a useful choice.

Accordingly in a first aspect the invention may be said broadly to consist in a process for the treatment of apples for protection against the bitter pit condition, which process comprises submerging said apples in an aqueous solution of CaClg in a pressure tight vessel, reducing the pressure in said vessel to the range of 25 to 60 kPa abs and retaining said reduced pressure for a predetermined residence time of at least one minute, restoring said pressure to atmospheric but retaining said apples in said aqueous'solution for at least a further 30 seconds and then removing said apples from said solution.

Preferably said apples are sprayed with water prior to said treatment and following said treatment.

Preferably the pH of the said solution is at least eight.

Preferably the pH of said solution is ten. 199533 Preferably the concentration;calcium ions in the solution of s-v • CaC^ is from 0.5 to 8% w/v, more preferably from 0.5 to 2% w/v.

Preferably said treatment under said pressure of 25 to 60 kPa abs is continued for from 1 to 3^ minutes.

Preferably said process is carried out continuously in cycles.

Preferably said solution is filtered continuously during said process.

Preferably there is present in said solution 20-100 ppm wetting agent.

Preferably there is present in said solution 2-10 ppm of an anti-foam agent.

In another aspect the invention may_ be* said broadly to consist in a process for the treatment of apples for protecticn against "the bitter pit condition, which process comprises submerging apples in an aqueous solution of CaC^ in a pressure tight vessel, increasing the pressure in said vessel to at least 130 kPa abs and retaining said elevated pressure for a predetermined residence time of at least one minute, restoring said pressure to atmospheric and removing said apples from said solution. ;Preferably said process includes the additional subsequent step of retaining said apples in said aqueous'solution for at least a further 30 seconds and then removing said apples from said solution. ;In another embodiment the invention may be said broadly to consist in an apparatus for the treatment of produce comprising, ;a fluid and pressure tight treatment vessel, ;liquid circulating means for circulating treatment liquid into and ;199533 ;- 4 - ;out of said vessel, ;pressure and/or vacuum applying means associated with said vessel to raise and/or lower the pressure therewithin, ;at least one door to allow the passage of produce into and out of said vessel, and, ;sequencing means to control the sequence of operations so that in use the components are operated in the following sequence: ;1) said door is fully shut, ;2) liquid is circulated into said vessel and held for a predetermined period of time, ;3) said vessel is pressurised or depressurised for a predetermined period of time, ;4) said liquid is circulated out of said vessel and, ;5) said door is opened. ;Preferably said second and third steps are confoined. ;Preferably said sequencing means is a micro-processor. ;Preferably said vessel is cylindrical and has a door at either end thereof. ;Preferably said doors at either end are hydraulically opened. ;Preferably said sequencing means,includes means to actuate said hydraulic door opening means. ;Preferably there are provided infeed and outfeed conveyors at either end of said cylindrical vessel. ;Preferably the operation of said infeed and said outfeed conveyors is controlled by said microprocessor. ;199533 ;- 5 - ;Preferably there is provided conveying means within said vessel. ;Preferably said conveying means within said vessel comprises rollers mounted within said vessel. ;Preferably said liquid circulating means comprises a main storage tank, a feed storage tank, conduits and a pump for circulating said liquid from said main storage tank to said feed storage tank. ;Preferably said feed storage tank is at a level above the level of said treatment vessel. ;Preferably there is a grid within said vessel to retain fruit within containers passing through said vessel from floating above treatment liquid. ;Preferably there is provided a filter in association with said feed storage tank. ;Preferably there is provided a sterilization loop in association with said feed storage tank to sterilize microorganisms present in said solution. ;Preferably there is present a vacuum applying means for reducing the pressure within said vessel. ;Preferably said vacuum applying means comprises a water ring pump. ;Preferably said system also includes a knock-out vessel between said treatment vessel and said pump. ;Preferably there are provided spraying booths in association with said conveying means into and out of said treatment vessel to spray fruit prior to entry into the treatment vessel and emerging after treatment therefrom. ;Preferably said booths include washing means for washing the bot- ;.1 99533 ;- 6 - ;torn of containers of produce. ;Preferably there is provided a solution preparation tank in association with said main storage tank for injecting a concentrated solution of solute into said solution. ;Preferably there is provided a bin stacker in association with said out-feed conveyer and an unstacker in association with said in-feed conveyer. ;Preferably the operation of said bin stacker is controlled by said microprocessor. ;The invention may be more fully understood by having reference to the drawing accompanying the provisional specification which is a schematic diagram of the apparatus according to the invention. ;The apparatus according to the invention comprises a treatment vessel 10 which is a cylindrical tank having hydraulically operated doors 11 and 13 at either end thereof. The tank is of a dimension to hold six bulk bins 18 of apples. A track is provided for bins 18 on rollers in vessel 10 which track extends along the length of vessel 10 near the base thereof. A perforated metal grid 20 is provided above the height of the line of the tops of the bins 18 to prevent apples from being floated out of the bins when the bins are immersed in the treatment solution. ;An infeed conveyer 12 is provided in association with door 11. An unstacker 14 resting on conveyor portion 27 unstacks bins 18 and places them onto conveyer 12. The bins then pass through a spray booth 16 which has upper sprayer 24 and lower sprayers 26. Outside and adjacent to door 13 is a second spray booth 22 also having upper ;199553 ;- 7 - ;sprayers 24 and lower sprayers 26. A second outfeed conveyer 28 is provided. A bin stacker 30 stacks bins 18 which have been treated. ;The conduit out of the top of vessel 10 connects with an oil free compressor 34, atmosphere and knock out vessel 36. A pair of alternative water ring vacuum pumps 38 and 39 are provided so that the system can remain operational if one pump is out of order. ;A main water storage tank 42 is provided at a level below treatment vessel 10. A mixing tank 44 is provided with a mixing blade 45 and calcium chloride injecting means to supply additional calcium chloride solution in a concentrated form to main storage tank 42. A pair of alternative pumps 46 and 47, each capable of filling feed storage tank 50 within 60% of the process cycle time, for example, are provided. A screen 32 is provided in one line in the line out of main storage tank 42 for straining leaves and other larger impurities discharged from tank 42. ;Feed storage tank 50 is provided at a level higher than treatment vessel 10. The capacity of the feed storage tank is 60% greater than the capacity of vessel 10. The capacity of the main storage tank 42 is 10% larger than the combined capacities of the feed storage tank 50 and the treatment vessel 10. ;A sterilisation loop 48 is provided out of and into tank 50 for sterilising the solution from time to time during operation. The loop 48 comprises a plate heat exchanger having a steam source of heating. ;A filtering loop 40 is also provided out of and into feed storage tank 50. The loop includes a pump and a filter. The filter is preferably a Culligan HD multimedia depth filter. The operation of ;- 8 - ;loop 40 will be discussed below. ;Control valves 51, 52, 53-, 54, 55, 56, 57, 58, 60, 62, 64 and 66 are provided in the various operating lines. The operation of these control valves is described below. ;A microprocessor is provided to sequence the operational steps of the apparatus. Liquid level detectors in the vessel 10 and in tanks 42, 44 and 50 feed signals as to the status of the tanks into the microprocessor. Detectors are provided with door opening mechanisms to detect the positions of the doors 11 and 13. A pressure detector is provided in vessel 10. Actuating switches are provided in connection with the microprocessor to actuate the various pumps, valves and other components. Actuators are also present in association with the unstacker 14 and stacker 30 and conveyors 12 and 28. ;In operation the sequence of processing is controlled by a microprocessor. When liquid level detectors in vessel 10 have detected that the vessel is empty doors 11 and 13 are opened. ;Conveyer 12 conveys six bulk storage bins 18 filled with apples through spraying booth 16 and onto the conveying rollers within vessel 10. At the end of a treatment the six bins 18 within vessel 10 are pushed onto conveyer 28 and here they are passed out through spray booth 22. The bins are restacked by automatic stacker 30 and the processed apples are returned to storage. In the meantime new bins 18 which have been placed onto conveyer portion 27 are unstacked by unstacker 14. The next bins 18 are conveyed along conveyor 12 into vessel 10. When the bins are present within vessel 10 doors 11 and 13 are shut and the automatic sequence begins. Once the detecters can ;199553 ;- 9 - ;detect that the doors are tightly in position control valves 54 and 62 are opened and valve 60 closed and treatment solution containing CaCl^ fills vessel 10 to a level above the grid 20 and valve 62 is closed. When vacuum processing is being used valve 54 is closed and valve 56 is opened and either pump 38 or 39 activated to create a vacuum of 25 to 60 kPa abs within vessel 10. The pressure is maintained at this lower level for a preset period of time, typically 1 to 3 minutes. ;The control valve 56 is closed and valve 54 opened to allow pressure to return to atmospheric within vessel 10. The apples are retained submerged in the treatment solution for an additional time of at least 30 seconds to complete the treatment. Valve 60 is then opened and treating fluid or liquid passes into main storage vessel 42. ;Prior to the commencement of the first cycle, the appropriate concentrations of calcium chloride (0.5 to 2% calcium ions typically), in 50 ppm wetting agent (surfactant) and 5 ppm of a silicone anti-foam ("Dow Emulsion AF") were mixed in mixing tank 44 and tank 42 topped up by opening control valve 58. A commercial calcium chloride flake, of which 25% w goes into solution as calcium ions, was used. ;Either pump 46 or pump 47 is run continuously to circulate water from main storage tank 42 to feed storage tank 50. Whenever required, valve 66 is closed and valve 64 opened and liquid being pumped by either pump 46 or 47 passed through the screen 32 to remove larger pieces of foreign matter. Otherwise valve 64 is closed and valve 66 open. ;When the solution has become spent or too contaminated for ;OOC- -;; J J ;- 10 - ;filtering to be effective it may be dumped to drains from tank 42. ;Tank 42 may then be refill erf from mains and the concentration of CaC^ increased to treatment level by adding a concentrated solution of it from mixing tank 44. ;When the treatment is carried out under pressure valve 52 is opened to compressor 34 instead of being opened to the vacuum sequence. ;Because of the high volumes which must be circulated through the system it is impractical to employ a filter in any of the direct lines between vessel 10 and main storage tank 42, main storage tank 42 and feed storage tank 50, or feed storage tank 50 and vessel 10. Thus in operation liquid from feed storage tank 50 is fed through filtering loop 40 by opening valves 51 and 53 during most of the running time of the system. The solution is sufficiently purified by such an operation that filtering in direct lines into or out of feed storage tank 50 is not required. ;Similarly sterilisation loop 48 is actuated by the opening of valves 55 and 57. It is not directly in a main flow line between main components for the same reason as filtering loop 40. It can be used continuously if required. The need for sterilisation can be monitored by the operator. ;Optimum process parameters are set out in the following examples. EXAMPLES: VARIATION OF PARAMETERS 1) pH of the Solution ;A standard treatment solution A was prepared using a 4% w/v solu- ;J 'I* tion of commercial flake CaC^ which contains Ca in a concentration of 1% w/v. Treatment was carried out for 2 minutes under a reduced pressure of 25 kPa abs. The apples were removed from solution immediately after pressure was returned to atmospheric. Solution A was not filtered. The pH of the solution was at its natural level of around pH6.

Solution B was prepared in the same way and apples treated under the same conditions except the pH of the solution was brought to pH7.

It was found that increasing the pH of chloride A and B to pH 10 increased the uptake of solution by the apples as shown in Table 1 below.

TABLE 1 Uptake at "normal" pH Uptake at Adjusted (pH 6-7) (mg/lOOg) pH (pH 10) (mg/lOOg) 61 111 122 198 2) Filtration of the Solution During processing material such as fine dirt and organic matter are washed off or leached from the apples. This material causes a deterioration in the liquor and progressively less and less solution is able to be taken up by the apples. Ultimately the solution has to be dumped and fresh solution is made. It has been found that a vast improvement in the liquor by filtering it. This restores the liquor to an "as fresh" condition enabling a full uptake ofsolution by the Solution A Solution B apples and prolonging the life of the liquor.

It has also been observed that the uptake of calcium from freshly made up solutions of CaC^ can be enhanced by filtering in a conventional activated carbon filter. Solutions C, D, E and F containing 1% ++ Ca and pH 6-7 are each used solutions taken from an operating plant, filtered and then reused. The increase in uptake of calcium is apparent from Table 2.

TABLE 2 Uptake of Unfiltered Solution (mg/lOOg) Uptake of Filtered Solution (mg/lOOg) Solution C Solution D Solution E Solution F 113 96 89 104 378 195 233 209 3) Submergence Time as the Controlling Factor in Solution Uptake It has been observed that for vacuum treatment at least, the length of time after vacuum release that the apples remain submerged is of greater importance than the length of time the vacuum is applied for. Solution G and solution H in Table 3 were freshly made up standard solutions with a concentration and pH the same as solution A of example 1. Solution I was a used solution taken unfiltered from an operating plant. The relative increases in uptake of calcium with increased post vaccuum submergence is apparent from Table 3.

TABLE 3 Submergence time Uptake (after vacuum release) (mg/lOOg) Solution G 10 sec 112 2 mi n 189 Solution H 10 sec 123 2 mi n 189 Solution I 10 sec 61 2 min 113 I $"33 14 -

Claims (38)

WHAT WE CLAIM IS: -

1. A process for the treatment of apples for protection against bitter pit condition, which process comprises submerging said apples in an aqueous solution of CaC^ in a pressure tight vessel, reducing the pressure in said vessel to the range of 25 to 60 kPa abs and retaining said reduced pressure for a predetermined residence time of at least one minute, restoring said pressure to atmospheric but retaining said apples in said aqueous solution for at least a further 30 seconds and then removing said apples from said solution.

2. A process according to claim 1 wherein said process is carried out continuously in cycles.

3. A process according to Claims 1 or 2 wherein said treatment under said pressure of 25 to 60 kPa abs is continued for from 1 to 33/2 mi nutes.

4. A process for the treatment of apples for protection against the bitter pit condition, which process comprises submerging said apples in an aqueous solution of CaC^ in a pressure tight vessel, increasing the pressure in said vessel to at least 130 kPa abs and retaining said elevated pressure for a predetermined residence time of at least one minute, restoring said pressure to atmospheric and removing said apples from said solution.

5. A process according to claim 4 wherein said process includes the additional subsequent step of retaining said apples in said aqueous solution for at least a further 30 seconds and then J99S33 - 15 - removing said apples from said solution.

6. A process claimed in any one of the preceding claims wherein said apples are sprayed with water prior to said treatment and following said treatment.

7. A process according to any one of the preceding claims wherein the pH of the said solution is at least 8.

8. A process according to any one of the preceding claims wherein the pH of the said solution is 10.

9. A process according to any one of the preceding claims wherein the concentration of calcium ions in the solution of CaC^ is from 0.5 to 8% w/v.

10. A process according to any one of the preceding claims wherein the concentration of calcium ions in said solution of CaC^ is from 0.5 to 2% w/v.

11. A process according to any one of the preceding claims wherein said solution is filtered continuously during said process.

12. A process according to any one of the preceding claims wherein there is present in said solution 20-100 ppm wetting agent.

13. A process according to any one of the preceding claims wherein there is present in said solution 2-10 ppm of an antifoam agent.

14. A process for the treatment of apples for protection against the bitter pit condition substantially as herein described with reference to the drawing accompanying the provisional specification.

15. An apparatus for the treatment of produce comprising, 198533 - 16 - a fluid and pressure tight treatment vessel, liquid circulating means for circulating treatment liquid into and out of said vessel, pressure and/or vacuum applying means associated with said vessel to raise and/or lower the pressure therewithin, at least one door to allow the passage of produce into and out of said vessel, and, sequencing means to control the sequence of operations so that in use the components are operated in the following sequence: 1) said door is fully shut, 2) liquid is circulated into said vessel and held for a predetermined period of time, 3) said vessel is pressurised or depressurised for a predetermined period of time, 4) said liquid is circulated out of said vessel and, 5) said door is opened.

16. An apparatus according to claim 15 wherein said second and third steps are combined.

17. An apparatus acccording to claim 16 wherein said sequencing means is a micro-processor.

18. An apparatus according to any one of the claims 15 to 17 wherein said vessel is cylindrical and has a door at either end thereof.

19. An apparatus according to claim 18 wherein said doors at either end are hydraulically opened.

20. An apparatus according to claim 19 wherein said sequencing means 1* 16 OCT 1984 CCU 199533 - 17 - includes means to actuate said hydraulic door opening means.

21. An apparatus according to any one of claims 18 to 20 wherein there are provided infeed and outfeed conveyors at either end of said cylindrical vessel.

22. An apparatus according to claim 21 wherein the operation of said infeed and said outfeed conveyors is controlled by said microprocessor.

23. An apparatus according to any one of claims 15 to 22 wherein there is provided conveying means within said vessel.

24. An apparatus according to claim 23 wherein said conveying means within said vessel comprises rollers mounted within said vessel.

25. An apparatus according to any one of claims 15 to 24 wherein said liquid circulating means comprises a main storage tank, a feed storage tank, conduits and a pump for circulating said liquid from said main storage tank to said feed storage tank.

26. An apparatus according to claim 25 wherein said feed storage tank is at a level above the level of said treatment vessel.

27. An apparatus according to any one of claims 15 to 26 wherein there is a grid within said vessel to retain fruit within containers passing through said vessel from floating above treatment liquid.

28. An apparatus according to either of claims 26 or 27 wherein there is provided a filter in association with said feed storage tank.

29. An apparatus according to any one of claims 25 to 27 wherein there is provided a sterilization loop in association with said feed storage tank to sterilize micro-organisms present in said 199533 - 18 - solution.

30. An apparatus according to any one of claims 15 to 26 wherein there is present a vacuum applying means for reducing the pressure within said vessel.

31. An apparatus according to claim 30 wherein said vacuum applying means comprises a water ring pump.

32. An apparatus according to any one of claims 15 to 31 wherein said system also includes a knock-out vessel between said treatment vessel and said pump.

33. An apparatus according to any one of claims 23 to 32 wherein there are provided spraying booths in association with said conveying means into and out of said treatment vessel to spray fruit prior to entry into the treatment vessel and emerging after treatment therefrom.

34. An apparatus according to claim 33 wherein said booths include washing means for washing the bottom of containers of produce.

35. An apparatus according to any one of claims 15 to 34 wherein there is provided a solution preparation tank in association with said main storage tank for injecting a concentrated solution of solute into said solution.

35. An apparatus according to any one of claims 33 to 35 wherein there is provided a bin stacker in association with said outfeed conveyor and an unstacker in association with said infeed conveyor.

37. An apparatus according to claim 36 wherein the operation of said bin stacker is controlled by said microprocessor. - 19 - 199533

38. An apparatus for the treatment of produce substantially as herein described with reference to the drawing accompanying the provisional specification. ^2. <soA QrCx'vi By sir authorised Agents., A. J. PAfcK & SON. V ■ r V "Ui 16 OCT 1984