OA12319A

OA12319A - Process for shelling fruits with shells

Info

Publication number: OA12319A
Application number: OA1200200259A
Authority: OA
Inventors: Anthony Martin Berlein; Anthony Walter Berlein
Original assignee: Berlin Process Technology Pty
Priority date: 2000-02-25
Filing date: 2001-02-23
Publication date: 2006-05-12
Also published as: WO2001062110A2; WO2001062110A3; AU4600501A; AU2001246005B2; BR0108645A; AP2002002607A0; AP1481A

Abstract

A method of treating nuts with shells containing a non-aqueous liquid comprising the steps of first removing at least 50 % of the non-aqueous liquid from the shells of the nuts; and thereafter subjecting the nuts to cold treatment to embrittle the shells. This method relates especially to cashew nuts and to the shelling of such nuts.

Description

PROCESS FOR SHELLING FRUITS WITH SHELLS 012319

Technical Field

This invention relates to a method of shelling fruits with shells, particularlybut not exclusively cashew nuts.

Background Art

The cashew nut tree (Anacardium Occidentale) produces a fruit, or cashewapple. This fruit is pear shaped and is similar in size to a large guava. At thebottom of the fruit, the seed (or nut) develops and hangs externally. The seed(or nut) is kidney shaped and is in reality the true fruit of the tree. When thefruit is ripe, it falls to the ground. The nut is then harvested and dried, inpréparation for shelling.

Raw cashew nuts consist of an outer skin, connected to a honey comb — likefibrous layer, which contains a highly corrosive and toxic resin known ascashew nut shell liquid (CNSL). This fibrous layer is in turn connected ro aninner shell which envelopes the kernel. The kernel is further protected by a 012319 membrane, or seed coat.

The outer skin is extremely tough but pliable. The CNSL (90% anacardic acidand 10% cardol) offers great protection against attack by insects, rodents and 5 birds. The inner shell allows water absorption into the kernel, but preventspénétration of CNSL.

Due to the toughness of the outer skin and the presence of the CNSL, theshelling of cashew nuts is an expensive process. Not only is it difficult to break 10 the outer skin without damaging the kernel, but great care must be taken thatthe CNSL does not contaminate the kernel. Contamination leads to aninferior taste. Furthermore, the seed coat clings to the kernel and has to bemanually scraped off once the shell has been removed. 15 Different processes hâve been suggested and are in use for shelling cashew nuts.Generally raw cashew nuts are bulk stored in a low humidity environmentwith a water content of 8-12% (by mass). This is in order to prevent stackburn and germination. Before shelling, the raw nuts are soaked in water inorder to increase the water content. The absorption of water causes: 20 1) The shell of the nut to swell and pull away from the kernel; 012319 2) The kernel to become flexible which reduces breakage during shelling; 3) Reduced burning of the kernel if CNSL removal is done by roasting of theraw nuts; and 4) Reduced viscosity of the CNSL. 5

After soaking the nuts in water the CNSL is removed by different methods' including : 1) Roasting the raw nuts in CNSL at about 250°C and then centrifugallyremoving the residue CNSL; 10 2) Super-heated steam application to the raw nuts and collection of condensate; and 3) Solvent extraction.

The shells may then be removed mechanically by centrifugally spinning the1 5 nuts and releasing them at high speed against an object; or pressing the nutsthrough inward turning rollers; or dropping the nuts through rotating conicalabrasive surfaces until the shell séparâtes from the nut. These mechanicalmethods hâve the disadvantage that they hâve a poor to very poor wholekernel recovery which reduces the value drastically. Semi-mechanical process 20 are accordingly more popular since they result in higher yields of whole 4 012319 kernels. Such semi-mechanical processes include: 1) Splitting the nut between two blades with a foot operated plunger; 2) Various hand operated cutting, sawing and squeezing devices; and 3) Hand shelling, by cracking the shell with a small wooden mallet. 5

Fr.ench Patent 2450 067 suggests a process of shelling nuts by plunging the nutsinto liquid air or liquid nitrogen and then crushing the nuts by mechanicalhammering to break the shells. The shelling is preceded by a double sizingprocess, humidification, steam drying and drying. This process has the 10 disadvantage that when the nuts are treated with the liquid air or nitrogen, thekernels easily become embrittled and break during the hammering process.The process does not disclose removal of CNSL prior to cryogénie treatæent.

Disclosure of the Invention 15

The inventors hâve now found that if the CNSL is removed prior to subjectingthe nuts to liquid nitrogen treatment, the recovery of whole kernels is increased. 20 As indicated above CNSL removal is a known process but not in combination 012319 with cryogénie treatment. In the prior art the CNSL is removed to preventkernel contamination and easier handling of the nut. During cryogénietreatment the last mentioned advantages hâve no significance since the CNSLwill be “frozen” during cryogénie treatment and difficulties relating to 5 contamination or handling due to CNSL would not occur. AccordinglyCNSL removal would not be contemplated where cryogénie treatment is tobe applied.

It is accordingly an object of the présent invention to provide an alternative 10 method of shelling fruit with shells.

According to the présent invention a method of treating nuts with shellscontaining a non-aqueous liquid comprises the steps of : first removing at least 50% (by mass) of the non-aqueous liquid from the 15 shells of the nuts; and thereafter subjecting the nuts to cold treatment to embrittle the shells.

In this spécification “non-aqueous liquid” is a liquid other than water. 20 In a preferred embodiment of the invention the nuts may comprise cashew 012319 nuts which include shells with CNSL therein as a non-aqueous liquid.Preferably at least 50% (by mass) of the CNSL is removed prior to subjectingthe nuts to the cold treatment, preferably as much CNSL as is practicallypossible is removed.

The invention also includes a method of treating cashew nuts with shellscontaining CNSL, the method comprising the steps of : first removing at least 50% (by mass) of the CNSL from the shells of thenuts; and thereafter subjecting the nuts to cold treatment to embrittle the shells.

The CNSL may be removed by subjecting the nuts to heat treatment,preferably subséquent to humidifying the nuts. The nuts may be subjected toheat treatment by roasting the nuts, preferably from 180 to 300°C, preferablyfrom 200 to 270°C, and preferably at about 220°C. The roasting may becarried out in a liquid, preferably in CNSL. The roasting may be for a periodof 1 to 3 minutes, preferably 1,5 to 3 minutes, preferably about 2 minutes.

Additionally, but preferably alternatively, the nuts may be subjected to heat treatment to remove CNSL and at least partially replace it with water. 7 012319

Preferably the nuts are subjected to steam treatment to remove CNSL and toat least partially replace CNSL with water. More than 70% (by mass) of theCNSL may be removed. Preferably steam is applied at a température from 90to 150°C; preferably from 100 to 140°C and most preferably at about 125°C. 5 The steam treatment may be for a period of 5 to 35 min, preferably 10 to 30minutes, preferably about 15 minutes.

Steaming may take place at a pressure of above atmospheric pressure. 10 The heat treated nuts may be subjected to centrifugal treatment to furtherremove at least some of the remaining CNSL especially where the nuts hâvebeen roasted. in cases where the nuts are subjected to heat treatment to replaceCNSL with water, the centrifugal treatment may be omitted. 15 Subséquent to the heat treatment the nuts may be cooled or allowed to cool toambient température.

The method may also include the step of humidifying the nuts to increase thewater content in the shells prior to removing the non-aqueous liqtxid. 20 Preferably the nuts hâve a water content of between 8 and 12% (by mass) 012319 prior to humidification.

Preferably the nuts are humidified in order that the shells hâve a water contentof between 15% and 50% (by mass), preferably between 20% and 40% (by 5 mass). Where the nuts are roasted to remove the CNSL, the water content ispreferably about 30% (by mass). Where the nuts are subjected to heattreatment to remove CNSL and replace it with water, the water content ispreferably about 25% (by mass). The nuts may be humidified through anyknown process such as soaking the nuts in water. 10

Where the method includes the step of humidifying the nuts to increase thewater content in the shells prior to removing the non-aqueous liquid, thehumidification preferably takes place at a température below 20°C, preferablybelow 15°C, preferably from 3 to 15°C, preferably from 5 to 10°C, most 15 preferably at a température of about 7°C. Preferably the nuts are humidifiedby soaking them in water. Preferably the nuts are soaked in the water for aperiod of 12 to 96 hours. Where the nuts are subjected to roasting to removeCNSL, the nuts or preferably soaked in water for a period of about 72 hoursat a température of about 7°C to obtain a water content of about 30% (by 20 mass). Where the nuts are subjected to beat treatment to replace CNSL with 012319 water, the nuts are soaked in water for a period of about 24 hours at atempérature of about 7°C to obtain a water content of about 25% (by mass).

The humidification of the nuts is preferably carried out in such a manner to5 control the amount of water reaching the kernels (especially in the case ofcashew nuts). If the water content of the kernels rises to above 14% by massit causes the kernels to split. It is believed that at the lower températuresindicated above, especially below 15°C, better control is obtained of themovement of water to the kernels. Furthermore if the nuts are humidified 10 above 20°C, tannins contained in the seed coat are deposited onto the kernel which leads to discoloration.

The cold treatment to embrittle the shells may comprise cryogénie treatment.Preferably the nuts are brought into contact with a medium in liquid form, 15 which medium would be in the form of a gas at ambient température and atatmospheric pressure. The medium may comprise liquid nitrogen or liquid air.

Preferably it comprises liquid nitrogen. 20 In cases where CNSL is removed without being replaced with water, the nuts 012319 10 may be treated with liquid nitrogen for a period from 10 to 90 seconds,preferably from 20 to 60 seconds, preferably about 40 seconds. In cases wherethe CNSL is replaced with water, the nuts may be treated with liquid nitrogenfor 10 to 60 seconds, preferably 15 to 40 seconds, preferably about 20 seconds. 5

Care should be taken not to subject the nuts to too long cold treatment, toprevent the kernels from becoming embrittled. It is believed that when theCNSL is removed prior to cold treatment the kernel is better isolated and lessprone to become embrittled. It is also believed that when the CNSL remains 10 in the shells, freezing of the CNSL results not in embrittlement of the shell,but rather hardening of the shell.

Sizing of the nuts may take place prior to subjecting them to cold treatmentto embrittle the shells. This is especially the case where the nuts are roasted to 1 5 remove CNSL. It is believed that sizing is not necessary where CNSL isreplaced with water.

Subséquent to the cold treatment the embrittled shells of the nuts may becracked. The cracked shells may then be removed. 20 012319 11

Known methods of cracking the shells may be employed.

In one embodiment of the invention the nuts may be centrifugally flungagainst an object, preferably the object is rotating in a direction opposite to the 5 movement of the nuts. ' It is also foreseen that the cracking may occur through ultrasonic treatment ofthe nuts subséquent to embrittlement. 10 It aiso is foreseen that the cracking may occur through subjection of the nutssubséquent to embrittlement to high frequency mechanical vibration.

Preferably cracking should take place as soon as possible after the coldtreatment. Preferably cracking should take place within seven seconds of the 15 cold treatment to embrittle the shells.

Once the shell has been removed the seed coat remains on the seed and has tobe removed. The seed coat may be manuaily removed. 20 It is foreseen that the kernel with the seed coat may be treated by means of a °’2379 12 gas such as ozone to enhance removal of the seed coat.

It is foreseen that a bleaching agent, such as ozone can be used to bleach kernels which hâve become discoloured.

According to another aspect of the présent invention there is provided amethod of treating cashew nuts which contain CNSL in their shells comprisingthe steps of : humidifying cashew nuts at a température below 20°C in order that the shells contain more than 10% (by mass) water; thereafter removing CNSL from the shells; and thereafter subjecting the nuts to cold treatment to embrittle the shells.

Preferably CNSL is replaced with water.

The method may also inciude the step of removing the shells subséquent to thecoid treatment.

According the another aspect of the présent invention a method of shellingnuts with shells containing a non-aqueous liquid comprises the steps of: 13 0 723 7 9 first removing at leasr 50% of the non-aqueous liquid from the shells of the nuis; thereafter subjecting the nuts to cold treatment to embrittle the shells; andthereafter cracking the embrittled shells of the nuts to remove said shells.

The invention also relates to products (especially shelled kernels of cashewnuts) produced by the above methods.

The invention will now be further described by means of the following non·limiting examples.

Example 1

An amount of 900kg dry raw cashew nuts, having a water content of about 8%by mass, was sized into four different categories according to known methods.The sizes were as follows (size in mm width):

Group 1 : smaller than 15mm

Group 2 ; from 15mm to 19mm

Group 3 : larger than 19mm to 23 mm 14

Group 4 : larger than 23mm °’23l9

The nuts were then soaked in water at a température of 7ÛC for a period of 72hours to allow the water content in the shells of the cashew nuts to raise above 5 10% (by mass). The water content of the nuts increased to 35% by mass.

The cashew nuts were then roasted in CNSL for a period of two minutes. Thenuts of group 1 were roasted at a température of 210°C, the nuts of group 2 ata température of 220°C, the nuts of group 3 at a température of 230°C and the 10 nuts of group 4 at a température of 240°C. The cashew nuts were thenremoved from the hot CNSL and remaining oil was removed by subjecting the. nuts to centrifugal treatment for a period of 2 minutes.

Thereafter the cashew nuts were allowed to cool to ambient température. The 15 cashew nuts were then submerged in liquid nitrogen for a period of 40 seconds.

After removal from the iiquid nitrogen the nuts were mechanically hurledagainst a Steel surface, where the shells shattered to separate them front the kernels. 20 15 072379 A 97% whole kernel recovery rate was achieved, without any CNSLcontamination to the kernels.

Example 2 5

An amount of 900kg dry raw cashew nuts, having a water content of about 8%by mass, was soaked in water at a température of 7°C for a period of 24 hoursto allow the water content in the shells of the cashew nuts to raise above 10% (by mass) to about 25% (by mass). 10

The cashew nuts were then steamed in a closed container containing water ata pressure of about 288 kPa for a period of 15 minutes at 125°C, after whichthey were removed and allowed to cool to ambient température. 15 The nuts were then submerged in liquid nitrogen for a period of 20 seconds.

After removal from the liquid nitrogen, the nuts were mechanically hurledagainst a Steel surface, where the shells shattered, to separate them from the kernels. 20 16 072379 A 94% whole kernel recovery was achieved, without any CNSL contamination to the kernels.

The method of example 1 used less liquid nitrogen compared to the method of5 example 2. However, the method of example 2, where CNSL is removed andreplaced with water by means of steam treatment, was found to be a cleaner and an easier method. in example 2 no sizing was required. 10 15 20

Claims

17 θ’23ΐ9 CLAIMS

1. A method of treaüng nuts with shells containing a non-aqueous iiquidcompnsing the steps of : first removing at least 50% of the non-aqueous Iiquid from the5 shells of the nuts; and thereafter subjecting the nuts to coid treatment to embâttle the shells.

2. The method of claim 1 wherein the nuts are cashew nuts with shells 10 containing CNSL, and wherein the method comprises the steps of : - fîrst removing at least 50% of the CNSL &om the shells of the nuts; and thereafter subjecting the nuts to cold treatment to embâttle the shells. 1&

3. The method of ciaim 2 wherein as much. CNSL as is practically possible is removed.

4. The method of claim 2 wherein the CNSL is removed by 20 18 °l23ig subjecting the nuts to heat treatment.

5. The method of claim 4 wherein the nuts are subjected to heattreatment by roasting the nuts at a température from 180 to 5 300°C.

6. The method of claim 4 wherein the nuts are subjected to heattreatment to remove CNSL and at least partially replace it with water. 10

7. The method of claim 6 wherein the nuts are subjected to steamtreatment to remove CNSL and at least partially replace CNSL with water.

8. The method of any one of the daims 2 to 7 wherein the nuts are humidified to increase the water content in the shells to between15 and 50% (by mass) prior to removing the CNSL.

9. The method of claim 8 wherein the nuts are soaked in water in order that the shells hâve a water content from 25 to 30% (by 20 19 °123iq mass},

10. The method of either one of daims 8 or 9 wherein the humidification takes place at a température below 20°C. 5

11. The method of daim 10 wherein the humidification takes place ata température from 3 to 15°C.

12. The method of claim 10 wherein the humidification takes place at 10 a température from 5 to 10°C.

13. The method of any one of the preceding daims wherein the coldtreatment to embrittle the shells comprises cryogénie treatment.

14. The method of daim 13 wherein the nuts are brought into contact with liquid nitrogen and/or liquid air.

15. The method of any one of the preceding daims wherein the embrittled shells of the nuts are cracked subséquent to the cold 20 treatment. °'23i9 20 16. 10 17. 18. 15 20 The method of claim 2 comprising the steps of : humidifying the cashew nuts at a température below 20°C inorder that the shells contain more than 10% (by mass) water; - thereafter removing at Ieast 50% of the CNSL from the shells; and - thereafter subjecting the nuts to cold treatment to embrittle the shells. The method of claim 16 wherein the removed CNSL is replaced with water. A method of shelling nuts with shells containing a non-aqueousliquid comprising the steps of : first removing at ieast 50% of the non-aqueous liquid from the shells of the nuts; thereafter subjecting the nuts to coid treatment to embrittle the shells; and thereafter cracking the embrittled shells of the nuts to remove said shells. 21. °123

19. Shelled nuts prepared by the method of claim 18.