MXPA99004799A - Cryogenic rheological modification of tree nuts - Google Patents

Abstract

A method and apparatus for cryogenic rheological modification of tree nuts and other shelled foodstuffs wherein brief cryogenic exposure facilitates further processing, particular shell removal. Nuts from a bin (12) of conditioned nuts are transported by a conveyor (14) to a cryogenic dip (16). The nuts are then conveyed by a conveyor (18) to a cracker feeder chain (20) to a cracker unit (22).

Description

CRYOGENIC RHEOLOGICAL MODIFICATION OF TREE NUTS Description of the Invention The application claims the benefits of the United States provisional patent application no. of series 60 / 060,163 entitled "Method and process to improve breaking of tree nut shells", by Stahmann, filed on September 25, 1997, and its specification is incorporated by reference. The present invention relates to the selective modification of the rheological properties of foods to improve their processing. More specifically, the present invention improves the fracturing process of tree nut shells by contacting the nuts with a cryogen. Food processing generally adds value to raw or comfort foods. Frequently, raw foods must be crushed, ground, fractured or broken to produce a final commercial product. The rheological properties of the food control the selection and finally the efficiency of these processes. The rheological properties determine how materials flow or deform. For example, hydration typically reduces Young's model. { a parameter used to help characterize the relationship between stress and strain) and the elastic tension of food as starch-producing grains. A reduced Young's modulus corresponds to an increase in stress for a given amount of applied tension while an elastic tension means that the food will fracture or tear with a reduced applied tension. High levels of hydration can minimize or even eliminate fractures, in those cases, the elastic tension corresponds to tearing or point where the applied tension causes the food to flow. Other processes such as freezing affect the rheological properties of foods differently. Freezing usually increases the Young's modulus, however the elastic tension may increase or decrease depending on the physical structure of the food, in the case of foods with a substantial water activity, the time-temperature curve, this is the cooling rate , often determines the crystal size. For example, slow freezing produces larger crystals while rapid freezing produces smaller crystals. In addition, slow freezing secretes soluble materials rather than rapid freezing. Although frozen foods always have a greater Young's modulus, those with larger crystals fracture differently than those with smaller crystals. To facilitate the fracture, a high Young's model and a lower elastic tension are desired. The following U.S. patents describe methods for cooling foods using cryogens: U.S. do not. 5,333,802 entitled "Method and apparatus for producing bits or pieces of a food" from Seeling et al., Describe the use of a liquid cryogen to alter the rheological properties of foods before cutting or cutting. The U.S. patent do not. 4,742,686 entitled "Process to increase the efficiency of the husking of tree nuts" by Cook, describes the use of a cryogen to freeze tree nuts with which the nuclei of the nuts harden more than the husks. The U.S. patent No. 4,436,757 entitled "Cryogenic Process for Debarking and Emptying Sunflower Seeds", by Lange et al, describes the use of cryogen diffusion in sunflower seeds followed by rapid heating to cause gas expansion and separation of the skin. . The U.S. patent 4,177,296 and entitled "Process for the preparation of a peanut mass" from Mochizuki et al, describes the cryogenic cooling and pulverization of pressed peanuts to obtain a peanut mass. The U.S. patent do not. No. 4,004,037 entitled "Making Peanut Butter" by Connick, describes the use of cryogen for the preparation of peanut butter in a low temperature non-oxidizing medium. U.S. Patent do not. 3,452,936 entitled "Reduction of cereal grains to flour", by Hanser, describes the use of cryogenic conditions to process cereal grains.

The U.S. patent do not. No. 3,413,818 entitled "Pelletizing by Injection", describes cryogenic food processing for storage or for subsequent freeze drying. The U.S. patent do not. No. 3,214,928 entitled "Method and apparatus for freezing food", from Oberdorfer, describes spraying and watering cryogenic fluids to freeze food products. The present invention is a method and apparatus for cryogenic rheological modification of skinned foods which consists of providing a skinned food consisting of one of an inner skin and inner fleshy part and briefly exposing the skinned food to a cryogen to modify Substantially the rheology of the outer layer substantially leaving the rheological of the inner flesh unaffected. In the preferred embodiment, the present invention further comprises hydrating the skinned food. Preferably, the preferred embodiment consists in providing, for example, nuts (for example, tree nuts), crustaceans or molluscs. To hydrate the tree nuts a hydrated moisture content of between about 5% by weight and about 7% by weight is preferred. The exposure consists of briefly exposing the skinned food to a cryogen for a sufficient time to improve the fracturing capacity of the peels. The preferred modality additionally consists of modifying after exposing, being to modify the fracturing of the husks of the food with husks, splitting the husks of the food with husks, burst the husks of the food with husk, exploiting the husks of food with husk, or their combinations. The modification preferably occurs approximately after 10 seconds of exposure, and employs an applied force of at least 10% less force than the applied force necessary to modify the shell foods in the absence of exposure to a cryogen and separates approximately 90%. % of the fleshy part of the corresponding husks. The exposure preferably consists of exposing for less than one minute, more preferably between about 3 and 16 seconds, and more preferably between about 6 and 15 seconds. The exposure preferably consists of briefly exposing the shell food to a cryogen having a temperature of at least 38 ° C less than the temperature of the shell food and more preferably at least 93 ° C less. A primary object of the present invention is to selectively modify the rheological properties of foods to improve the processing of foods. A first advantage of the present invention is the improved processing of the tree nuts with which more intact peeled nuts are recovered.

Other objects, advantages and novel features, and other scope of applicability of the present invention will be described in part of the detailed description that follows and in part will be apparent to those skilled in the art after examining the following, or can be learned by putting in practice the present invention. The objects and advantages of the invention can be realized by means of the instrumentation and combinations particularly indicated in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS The appended drawing that is incorporated in and forms part of the description illustrates one embodiment of the present invention and together with the description serves to explain the principles of the invention. The drawing is for illustrative purposes only of a preferred embodiment of the invention and should not be construed as limiting the invention. In the drawing: Figure 1 is a block diagram of the preferred embodiment of the present invention. The present invention selectively manipulates the rheological properties of foods. The present invention uses the techniques of cryogenic hydration and freezing and their combinations to facilitate the fracturing of foods. Foods and other materials with an outer husk or husk and a fleshy inner part include nuts, crustaceans and molluscs. In a preferred embodiment, the tree nuts are quilt and are briefly exposed to a cryogenic fluid. The hydration step reduces the Young's modulus of the nut while the cryogenic exposure increases the Young's modulus of the shell while reducing the elastic tension of the shell. In a preferred embodiment, shell fracture occurs with the least applied stress and the least damage to the fleshy part of the nut. Clearly, the speed at which the stress is applied to the walnut shell is an important factor for fracture; however, most commercial processes use speeds that are sufficient in such a way that the discussion of this factor has less importance. In general, to fracture nut shells, the present invention uses a three-stage process. The first stage hydrates the fleshy part of the nut, typically to a moisture content of between 5% by weight and 7% by weight. This stage also increases the water content of the shell. The next stage uses a cryogenic fluid to freeze the water that has been introduced into the shell. The period of contact between the shell and the cryogenic fluid is short, for example less than one minute such that the nut does not freeze. The third stage of fracturing follows immediately to ensure that the temperature of the shell has not increased substantially. To achieve rapid freezing of the shell, the freezing stage uses a high temperature differential between the nut and the cryogen, for example greater than 38 ° C. Suitable cryogens include, without limitation, for example liquid nitrogen, boiling point at -195.6 ° C, liquid oxygen (boiling point at -182.8 ° C), liquid helium (boiling point at -268.3 ° C), and dioxide of solid carbon (sublimation point at -78.3 ° C). When the temperature of the shell is above -17 ° C, the liquefied oxygen produces a temperature differential May at about 93 ° C, and the liquid nitrogen produces a temperature differential greater than about 149 ° C. In most cases the cryogenic fluid or solid makes contact with the food directly, however heat transfer media can also be used. For direct cryogenic contact with for example a walnut shell, thermal energy is transferred from the shell to the cryogen. For cryogenic liquids, first the fluid that surrounds the shell can vaporize and form a vapor layer around the shell is the Leidenfrost effect. Typically a vapor layer reduces the heat transfer coefficient, however as the surface temperature falls the Leidenfrost effect dissipates and rapid cooling results. For some tree nuts, there may be a small layer of gas between the shell and the fleshy part. This gas layer typically has a lower heat transfer coefficient than the shell and thus protects the fleshy part of the nut from freezing (the coefficient of heat transfer from the fleshy part of the nut and shell also differs and depends on such factors as water activity and fat content). After hydration, however such a gas space can be filled with water increasing the thermal transfer of the fleshy part of the nut. This effect that seems harmful is balanced by the ability to freeze or supercool the inner water. In most circumstances, the density of water decreases upon freezing causing the water to expand when it freezes. Expanded frozen water exerts a force on the shell; This force can help the process of removal of the general skin. Superfried water or liquid water at a temperature below the freezing point freezes quickly when disturbed or when an impetus is given to crystallize, for example a drop in pressure or initial point of crystal formation. Again the expansion of the freezing water will exert an outward force on the shell and help the process of removal of the general shell. The following three stages are of a preferred embodiment of the present invention, the first stage conditions the nuts by exposing them to a moist medium to increase the "free" water content in the fleshy part of the walnut to between 5% by weight and 7% by weight. % by weight and the same type introduced in the moisture in the shell. When wet, the fleshy part of the nut is flexible and will not break when the shell is broken or crushed. In the second stage, the nuts are exposed to a cryogen for a period of preferably about 3 to 16 seconds, and more preferably about 6 to 15 seconds depending on the size of the nut and the thickness of the shell. When liquid nitrogen is used, the freezing process leads to shell temperature at about 195.5 ° C, making the shell very brittle but the fleshy part of the nut remains flexible. The nuts are transferred to a nutcracker immediately after exposure to the cryogen, for example in 10 seconds, and are cracked with a reduced striking force at approximately 10 to 25% of the normal force. The striking force is a force that is applied to the surface of the shell and when it is expressed on the surface area, it represents an applied force or pressure. The reduced striking force also contributes to less damage to the fleshy part of the nuts, more whole nuts and more halves without damage in the case of nuts such as paper peel or pecans. In addition, brittle shells are broken and detached more completely than in conventional processes. So the need for a peeling process to separate the nuts from their peels is reduced (Peeling processes often damage nuts). In many cases, about 90% of the product can use the peeling process through the use of the present invention. In general, the invention results in more whole or whole halves, fewer pieces and less lost by grinding. In addition to or as a substitute for the applied mechanical forces, forces applied in the form of for example liquid or air jets can be used. A pressure drop can cause the shell to explode while an increase in pressure can cause the shell to burst. Techniques using supercritical transitions, for example supercritical carbon dioxide techniques, are also encompassed in the present invention and can serve to cool and / or fracture the shells. Figure 1 illustrates the preferred apparatus of the invention 10. The nuts of the conditioned nut tank 12 are transported with a conveyor 14 to a cryogenic bath 16. The nines are then transported by the conveyor 18 to a feeder chain 20 to the cooling unit. Cascading 22. The present invention can be used with traditional methods of food processing. For example some milling processes use chemical substances such as sodium hydroxide or sulfur dioxide to improve hydration. The addition of these chemicals accelerates the rate of hydration and can drastically reduce processing times. The first stage of the present invention is designed to accommodate alternative processes of soaking to hydration. Regardless of the specific nature of the first stage, the present invention has the advantage that the freezing stage is fast and therefore does not tend to be a speed limiting step. Although the invention has been described in detail with particular reference to those preferred embodiments, other embodiments may achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover those modifications and equivalents in the following claims. The descriptions of all references, applications, patents and publications cited above are incorporated.

Claims (32)

1. CLAIMS l. - n method of cryological modification of criogenic food with skin, the method consists of the steps of: providing a food with skin that consists of outer shell and inner fleshy part; and briefly exposing the skinned food to a cryogen to substantially modify the rheology of the outer shell without substantially affecting the rheology of the inner fleshy part.
2. 2. - The method according to claim 1 further comprising the step of hydrating the skinned food after the stage of providing the food.
3. 3. - The method according to claim 2 wherein the step of providing consists of providing nuts.
4. 4 - The method according to claim 3 in which the step of providing consists of providing tree nuts.
5. 5. - The method according to claim 4 wherein the hydration step consists of hydrating the tree nuts to a content between about 5% by weight and about 7% by weight.
6. 6. - The method according to claim 1 in which the step of providing the skinned food selected from the group consisting of nuts, crustaceans and molluscs.
7. 7. The method according to claim 1, wherein the exposure step consists of briefly exposing the shell-fed food to a cryogen for a sufficient time to improve the fracture capacity of the peels.
8. 8. - The method according to claim 1 further comprising a step of modification after the selected exposure stage of the group consists of fracturing the peels of the food with peel, split the peel of the food with peanuts, burst the peels of the food with peel, explode the peels of food with peel.
9. 9. - The method according to claim 8 wherein the step of modifying occurs within approximately 10 seconds of the exposure step.
10. 10. The method according to claim 8, wherein the step of modifying consists in using an applied force of at least 10% less in force than the applied force necessary to modify the foods with husks in the absence of exposure to a cryogen.
11. 11. The method according to claim 8, wherein the step of modifying consists in separating at least approximately 90% of the fleshy part from the corresponding peels.
12. 12. - The method according to claim 1 wherein the exposure step consists of exposing for less than about 1 minute.
13. 13. - The method according to claim 12 wherein the exposure step consists of exposing for between about 3 and 16 seconds.
14. 14. - The method according to claim 13 wherein the exposure step consists of exposing for between about 6 and 15 seconds.
15. 15. - The method according to claim 1 wherein the exposure step consists of briefly exposing the shell food to a cryogen having a temperature of at least 38 ° C less than the temperature of the shell food.
16. 16. - The method according to claim 1 wherein the exposure step consists in briefly exposing the shell food to a cryogen having a temperature of at least 93 ° C less than the temperature of the shell food.
17. 17. - An apparatus for the cryogenic rheological modification of skinned foods, the apparatus comprising: means for providing a skinned food consisting of an outer layer and inner fleshy part; and means for briefly exposing the skinned food to at least one cryogen to substantially modify the rheology of the outer layer without affecting the rheology of the inner fleshy part.
18. 18. - The apparatus according to claim 17 further comprising means for hydrating the skinned food.
19. 19. - The apparatus according to claim 18 where the food with shell consists of nuts.
20. 20. The apparatus according to claim 19 wherein the shell food consists of tree nuts.
21. 21. The apparatus according to claim 20 wherein the moisturizing means consist of hydrating the tree nuts to a moisture content between about 5% by weight and 7% by weight.
22. 22. - The apparatus according to claim 17 wherein the shell-fed food consists of a member selected from the group consisting of nuts, crustaceans and mollusk.
23. 23. - The apparatus according to claim 17 wherein the means of exposure consists of means for briefly exposing the shell-fed food to a cryogen for a sufficient time to improve the fracture capacity of the peels.
24. 24. The apparatus according to claim 18 further comprises modifying means selected from the group consisting of means for fracturing the husks of the food with husks, means for splitting the husks of the food with husks, means for bursting the husks of the food. with peel and means to exploit the peels of food with peel.
25. 25. The apparatus according to claim 24, wherein the modifying means operates at approximately 10 seconds from the exposure stage.
26. 26. The apparatus according to claim 24, wherein the modifying means consists in using an applied force of at least 10% less force than the applied force necessary to modify the foods with shell in the absence of exposure to a cryogen.
27. 27. The apparatus according to claim 24 wherein the modifying means consists in separating at least about 90% of the fleshy part of the corresponding shells.
28. 28. The apparatus according to claim 17 wherein the means of exposure consist of means to expose for less than about one minute.
29. 29. The apparatus of claim 28, wherein the means of exposure consist of means for exposing between about 3 and 16 seconds.
30. 30. The apparatus of claim 29, wherein the means of exposure consist of means for exposing between about 6 and 15 seconds.
31. 31, - The apparatus according to claim 17, wherein the means of exposure consists of means for briefly exposing the shell-fed food to a cryogen having a temperature of at least 38 ° C less than a temperature of the shell-fed food.
32. 32. The apparatus according to claim 31, wherein the means of exposure consists of means for briefly exposing the shell-fed food to a cryogen having a temperature of at least 93 ° C less than a temperature of the shell-fed food.