PECAN NUT KERNEL EXTRACTION METHOD

Abstract

The invention relates to a pecan nut kernel extraction method including the steps of sizing pecan nuts from which kernels are to be extracted to have a maximum diameter size variation of 8 mm; controlling the moisture content of the shells of the pecan nuts to within a shell moisture control range of 3% to 30%; heating the kernels to a temperature of between 20° C. and 100° C.; pre-cracking the shells; immersing the nuts in liquid nitrogen, or the like, for between 5 and 15 seconds; and cracking the shells within no more than 15 seconds from completing the cryogenic fluid immersion step to substantially separate the shells from the kernels. The method also includes performing the steps in the absence of a pre-cracking step or in the absence of the cryogenic fluid immersion step.

Claims

1-29. (canceled)

30. A pecan nut kernel extraction method, comprising: sizing pecan nuts from which kernels are to be extracted to have a maximum diameter size variation of 8 mm; controlling the moisture content of shells of the pecan nuts to within a shell moisture control range of 3% to 30%; heating the kernels to a temperature of between 20° C. and 100° C.; pre-cracking the shells; immersing the pecan nuts in liquid nitrogen for between 5 and 15 seconds; and cracking the shells within no more than 15 seconds from completing the immersing step to substantially separate the shells from the kernels.

31. The pecan nut kernel extraction method of claim 30 wherein the immersion time period in the immersion step is 10 seconds.

32. A pecan nut kernel extraction method, comprising: sizing pecan nuts from which kernels are to be extracted to have a maximum diameter size variation of 8 mm; heating the kernels to a temperature of between 20° C. and 100° C.; controlling the moisture content of shells of the pecan nuts to within a shell moisture control range of 3% to 30%; immersing the pecan nuts in liquid nitrogen for a predetermined time period between 15 and 30 seconds; and cracking the shells within no more than 15 seconds from completing the immersing step to substantially separate the shells from the kernels.

33. The pecan nut kernel extraction method of claim 32, further comprising cleaning the pecan nuts before immersing them in liquid nitrogen.

34. A pecan nut kernel extraction method, comprising: sizing pecan nuts from which kernels are to be extracted to have a maximum diameter size variation of 8 mm; heating the kernels to a temperature of between 20° C. and 100° C.; controlling the moisture content of shells of the pecan nuts to within a shell moisture control range of 3% to 30%; pre-cracking the shells; allowing the nut shells to cool down to a temperature of about 20° C.; and cracking the shells to substantially separate the shells from the kernels.

35. The pecan nut kernel extraction method of claim 34, further comprising cleaning the pecan nuts before heating the kernels.

36. The pecan nut kernel extraction method of claim 34, wherein heating the kernels includes heating the kernels to a temperature of about 70° C.

37. The pecan nut kernel extraction method 34 wherein heating the kernels includes heating the kernels by exposing the pecan nuts to a minimum temperature of 70° C. for at least 2 minutes.

38. The pecan nut kernel extraction method 34 wherein heating the kernels includes subjecting the nuts to an amount of microwave radiation for a predetermined time period, the combination of the amount of microwave radiation and the time period which has been empirically determined to heat the kernels of a specific pecan cultivar from which kernels are being extracted using the method to the desired temperature.

39. The pecan nut kernel extraction method 34 wherein controlling the moisture content of the shells of the pecan nuts includes empirically determining the moisture content of the shells, and subjecting the pecan nuts to remedial action to either increase or decrease the moisture content of the shells to be within the shell moisture control range.

40. The pecan nut kernel extraction method of claim 39 wherein the remedial action for increasing the moisture content of the shells includes any one or more of subjecting the pecan nuts to steaming or boiling, or by humidifying the shells.

41. The pecan nut kernel extraction method 40 wherein the pecan nuts are subjected to steaming for a period of between 1 and 20 minutes.

42. The pecan nut kernel extraction method of claim 39 wherein the remedial action for decreasing the moisture content of the shells includes actively or passively drying the shells.

43. The pecan nut kernel extraction method of claim 34 wherein the shell moisture control range is between about 5% and 20%.

44. The pecan nut kernel extraction method of claim 34 wherein heating the kernels includes subjecting the pecan nuts to steaming or boiling.

45. The pecan nut kernel extraction method of claim 44 wherein the pecan nuts are subjected to steaming or boiling to simultaneously achieve the remedial action of increasing the moisture content of the shells and to heat the kernels.

46. The pecan nut kernel extraction method of claim 34 wherein heating the kernels includes subjecting the pecan nuts to a heating step that excludes the addition of moisture, including subjecting the pecan nuts to microwave heating or convection heating, and if required subjecting the pecan nuts to a separate pasteurization step.

47. The pecan nut kernel extraction method of claim 46 wherein the remedial action of decreasing the moisture content of the shells includes subjecting the pecan nuts to active or passive drying of their shells.

48. A pecan nut kernel extraction method, comprising: sizing pecan nuts, at least some of which have been pre-cracked and from which kernels are to be extracted, to have a maximum diameter size variation of 8 mm; controlling the moisture content of the shells of the pecan nuts to within a shell moisture control range of 3% to 30%; heating the kernels to a temperature of between 20° C. and 100° C.; immersing the nuts in liquid nitrogen for between 5 and 15 seconds; and cracking the shells within no more than 15 seconds from completing the immersing step to substantially separate the shells from the kernels.

49. The pecan nut kernel extraction method of claim 48 wherein heating the kernels includes heating the kernels to a temperature of about 70° C.

50. The pecan nut kernel extraction method of claim 49 wherein heating the kernels includes exposing the pecan nuts to a minimum temperature of 70° C. for at least 2 minutes.

51. The pecan nut kernel extraction method of claim 48 wherein controlling the moisture content of the shells of the pecan nuts includes empirically determining the moisture content of the shells, and subjecting the nuts to remedial actions to either increase or decrease the moisture content of the shells to be within the shell moisture control range.

52. The pecan nut kernel extraction method of claim 51 wherein the remedial action for increasing the moisture content of the shells comprises any one or more of subjecting the pecan nuts to steaming or boiling, by or humidifying the shells.

53. The pecan nut kernel extraction method of claim 52 wherein the pecan nuts are subjected to steaming for a period of between 2.5 and 10 minutes.

54. The pecan nut kernel extraction method of claim 51 wherein the remedial action for decreasing the moisture content of the shells includes actively or passively drying the shells.

55. The pecan nut kernel extraction method of claim 48 wherein pre-cracking of the shells includes subjecting the shells to mechanical stress in a mechanical cracker configured to deliver only side impacts to the pecan nuts.

56. The pecan nut kernel extraction method of claim 48 wherein the shell moisture control range is between about 5% and 20%.

57. The pecan nut kernel extraction method of claim 48 wherein the pecan nuts are sized to have a variation in diameter not exceeding 6 mm.

58. The pecan nut kernel extraction method of claim 48, further comprising splitting any whole kernels produced by the method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Preferred embodiments of the invention are described by way of example only and with reference to the drawings in which:

[0077] Table 1 shows the effect of steaming pecan nuts on its kernel moisture content, with an average starting moisture content of about 3%;

[0078] FIG. 1 is a diagrammatic representation of the process flow used in example 1;

[0079] FIG. 2 is a diagrammatic representation of the process flow used in example 2;

[0080] FIG. 3 is a diagrammatic representation of the process flow used in example 3;

[0081] FIG. 4A is a diagrammatic representation of the process flow used in example 4A; and

[0082] FIG. 4B is a diagrammatic representation of the process flow used in example 4B.

DETAILED DESCRIPTION OF THE INVENTION

[0083] The applicant has found that it is possible to use the characteristics of the shell to assist in the recovery of the kernel from the shell without damaging the kernel. The applicant aims to disrupt the structure of the shell as much as possible, without removing it from around the kernel, prior to exposing it to a cryogen. This is done in concert with increasing the temperature of the kernel, which protects the kernel from the process of destructing the shell.

[0084] It is required to strike a balance between compromising the shell and breaking the shell. If the shell is largely detached there is a risk of discolouration and exposure of the kernel to the cryogenic fluid.

[0085] The inventor therefore recognized that it is inevitable that at least some nuts will have their kernels exposed to the cryogenic fluid and has found that the risk of damage to such nuts especially, but also other undamaged nuts in general, can be managed by heating the kernels.

[0086] The effect of heating the kernels is believed to decrease the viscosity of oils and fats within the kernel, which makes the kernel more pliable and resistant to impact forces. This is also believed to protect the kernel against the possible effects of freezing. In terms of the kernel, the temperature differential between the heated kernel and any cryogen that may penetrate through a cracked shell will accentuate the Leidenfrost effect. This at least creates a time delay between the cryogen coming into contact with the kernel and the kernel freezing as a result of it. In addition, the cryogen then still has to extract the heat from the kernel before the kernel will freeze.

[0087] In contrast, the shell has much less fats and oils, and with an increase in its moisture content to within the shell moisture control range, the shell will be targeted much quicker by the cryogen than the kernel will be when the pecan nuts are immersed in the cryogen. Another factor here is that with pre-cracking the cryogen is enabled to contact the shell on the outside and also on the inside (between the shell and the kernel). The shell is thinner than the kernel and at least to some extent contacted by the cryogen from both outside and inside. In comparison, the kernel is thicker and only contacted to a limited extent on its outer surface by the cryogen, to the extent that it penetrates the cracks in the shell caused by the pre-cracking. This amplifies the time difference that it takes the cryogen to freeze the shell compared to freezing the kernel.

[0088] This allows in practical terms a time delay between exposure to the cryogen and possible freezing of the kernel. By managing the heat in the kernel, i.e. its temperature, and the duration of exposure to the cryogen the risk of fracturing the kernel is effectively addressed.

[0089] The inventor has established that the best results are obtained when the nuts are compromised before exposure to the cryogenic fluid and the kernel are heated. However, it is possible to achieve still acceptable results, which also present an improvement over the results from prior art techniques, by making use of either comprising the shells before exposure to cryogenic fluid or heating the kernels.

[0090] The inventor has established that there are several possible implementations of this principle, some of which is explained in more detail with reference to test results below. In each instance, practical variables are accounted for to compensate for characteristics of specific pecan cultivars that are being treated.

Example 1—Mixed Cultivar (Nuts which are not Pre-Cracked)

[0091] Mixed cultivar pecans in-shell (1), with a medium kernel content of about 51% (shell to kernel ratio), and with a kernel moisture content of less than 4% and a shell moisture content of between 8% and 10%, were pre-sized (2) into a size range of 22 mm to 24 mm.

[0092] The nuts in shell were then boiled (3) for 10 minutes. As a result of this, the kernel moisture content of the nuts increased to between 4% and 5%, and the shell moisture content of the nuts increased to about 20%.

[0093] The nuts were allowed to cool (4) for 5 minutes. The nuts were then exposed to liquid nitrogen (5) for 20 seconds and cracked in a double jaw-type cracker (6) with a total taper from top to bottom of 2.5 mm in less than 5 seconds following completion of the exposure to the liquid nitrogen.

[0094] This resulted in a recovery of 100% fully intact kernels with 100% cracked and shelled after cracking (7).

[0095] The process flow of this example is indicated graphically in FIG. 1.

Example 2—Mixed Cultivar (Pre-Cracked and Pre-Sized Nuts)

[0096] Pre-cracked mixed cultivar pecans in-shell (11), with a medium kernel content of about 51% (shell to kernel ratio), and with a kernel moisture content of about 3% and a shell moisture content of between 8% and 10%, were pre-sized (12) into a size range of 24 mm to 26 mm.

[0097] The nuts in shell were steamed (13) at atmospheric pressure at about 98° C. for 5 minutes.

[0098] The nuts were allowed to cool (14) for 2% minutes. The nuts were then exposed to liquid nitrogen (15) for 10 seconds and cracked in a double jaw-type cracker (16) with a total taper from top to bottom of 6 mm in less than 5 seconds following completion of the exposure to the liquid nitrogen.

[0099] This resulted in a recovery of 100% fully intact kernels with 100% cracked and shelled after cracking (17).

[0100] The process flow of this example is indicated graphically in FIG. 2.

Example 3—Ukulinga Cultivar

[0101] Thick shell cultivar (Ukulinga) pecans in-shell (which are notoriously difficult to crack due to their thick shells) (21), with a medium kernel content of about 50% (shell to kernel ratio), and with a kernel moisture content of about 3% and a shell moisture content of between 8% and 10%, were pre-sized (22) into a size range of 20 mm to 21.5 mm.

[0102] The nuts in shell were steamed (23) at atmospheric pressure at about 98° C. for 15 minutes.

[0103] Whilst still hot the nuts were pre-cracked (24) in a double jaw-type cracker with an initial total taper from top to bottom of 1 mm and the jaws in the maximum closed position of 20.5 mm at the inlet and 19.5 mm at the outlet.

[0104] The nuts were then exposed to liquid nitrogen (25) for 10 seconds, and in less than 5 seconds following completion of the exposure to the liquid nitrogen the nuts were cracked in the same double jaw-type cracker with a total taper from top to bottom of 1 mm (26). For the final cracking the jaws were closed by 2 mm, to have in the maximum closed position a size of 18.5 mm at the inlet and 17.5 mm at the outlet.

[0105] This resulted in a recovery of 95% fully intact kernels with 97% cracked and shelled after cracking (27).

[0106] The process flow of this example is indicated graphically in FIG. 3.

Example 4—Wichita Cultivar (Comparison)

[0107] A comparison was made between the results of pre-cracking nuts and of not pre-cracking nuts, with subsequent cryogenic treatment of the nuts.

[0108] For the nuts treated without pre-cracking, Wichita cultivar with a shell to kernel ratio of 62% (31), which are notoriously difficult to crack due to their high kernel percentage without severe damage to the kernels, with a shell moisture content of 7% and kernel moisture content of about 3%, were pre-sized (32) in a size range of 21.5 mm to 23 mm.

[0109] The nuts in shell were steamed (33) at atmospheric pressure at about 98° C. for 15 minutes.

[0110] The shell-moisture content increased to about 11.5% and the kernel moisture content increased to about 4.5%.

[0111] The nuts were then exposed to liquid nitrogen (34) for 15 seconds, and in less than 5 seconds following completion of the exposure to the liquid nitrogen the nuts were cracked in a double jaw-type cracker with a total taper from top to bottom of 3 mm, with an inlet setting in the maximum closed position of 21.5 mm and 18.5 mm at the outlet (35).

[0112] This resulted in a recovery of 75% fully intact kernels with 35% cracked and shelled after cracking (36).

[0113] The process flow of this example is indicated graphically in FIG. 4A.

[0114] For the nuts treated with pre-cracking, a second sample was drawn from the same batch of Wichita cultivar with a shell to kernel ratio of 62% (41) with a shell moisture content of 7% and kernel moisture content of about 3%, were pre-sized (42) into a size range of 21.5 mm to 23 mm.

[0115] The nuts in shell were steamed (43) at atmospheric pressure at about 98° C. for 15 minutes.

[0116] The shell-moisture content increased to about 11.5% and the kernel moisture content increased to about 4.5%.

[0117] The nuts where then, within 10 seconds from the steaming, pre-cracked (44) in the same double-jaw cracker (as that described with reference to FIG. 4A) with an inlet setting of 21.5 mm and 18.5 mm at the outlet, for a total taper from top to bottom of 3 mm.

[0118] The nuts were then exposed to liquid nitrogen (45) for 10 seconds, and in less than 5 seconds following completion of the exposure to the liquid nitrogen the nuts were cracked (46) in the same double jaw-type cracker with an inlet setting in the maximum closed position of 20.5 mm and 17.5 mm at the outlet, for a total taper from top to bottom of 3 mm.

[0119] This resulted in a recovery of 81% fully intact kernels with 81% cracked and shelled after cracking (47).

[0120] The process flow of this example is indicated graphically in FIG. 4B.

[0121] With this comparison the effect of the combination of the pre-cracking and heating (in this instance by means of steaming) is shown. The typical recovery of Wichita cultivar with a shell to kernel ratio of about 62%, is less than 50% fully intact kernels with less than 10% cracked and shelled after cracking. The combination of pre-cracking and heating thus presents a significant improvement of prior art processes. Even the heating without pre-cracking presents a notable improvement over the prior art processes.

[0122] In cultivars that are easier to process, it is possible to achieve improved and acceptable results by using heating and/or pre-cracking with the liquid nitrogen.

[0123] By making use of the process of the invention it is possible to impact the nuts with a force that is greater than what is conventionally used to crack pecan nut shells. The advantage of this, contrary to conventional wisdom, is that such a greater and in effect sharper (higher impact) force, shatters the shell with greater effect than a lower level impact. Since the kernels are protected by their increased temperature, the higher force on the shell does not damage the kernel.

[0124] In respect of the kernel and shell, the level of oils and fats in the kernel is about 20 times greater than those in the shell. This explains why the kernel's resilience is more much responsive to an increase in temperature of the kernel, than the resilience of the shell is to the same increase in temperature—the shell contains far less oils and fats compared to the kernel. The high fat and oil content of the kernel allows these constituents to increase the pliability of the kernel when they are heated up, with a reduction in their viscosity. At higher temperature these oils and fats flow easier, which is believed to allow the kernel to resist impacts more successfully.

[0125] It will be appreciated that the embodiments described above are given by way of example only and are not intended to limit the scope of the invention.