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EP-4741059-A1 - METHOD FOR OBTAINING DEHULLED CORN KERNELS

EP4741059A1EP 4741059 A1EP4741059 A1EP 4741059A1EP-4741059-A1

Abstract

The present invention refers to a method for obtaining dehulled corn kernels comprising the steps of providing raw corn kernels, subjecting said kernels to an acid hydrolysis while heating, washing the hydrolyzed-pericarp corn kernels and optionally drying the dehulled corn kernels obtained to a final moisture adequate to safe storage and manufacture of the dehulled corn kernels.

Inventors

  • VELDERRAIN RODRÍGUEZ, Gustavo Ruben
  • MARINÉ MONTEIRO, Agustin Henry
  • MARINÉ TRIAS, Agustin

Assignees

  • Quality Corn Grain S.A

Dates

Publication Date
20260513
Application Date
20241111

Claims (15)

  1. A method for obtaining dehulled corn kernels, comprising the steps of: a) providing raw corn kernels, b) subjecting the corn kernels of step a) to hydrolysis with an acid aqueous solution at an acid concentration between 15 and 50% v/v while heating at a temperature comprised between 40 °C and 90 °C to obtain hydrolyzed-pericarp corn kernels and a waste acid aqueous solution, c) washing the hydrolyzed-pericarp corn kernels obtained step b) with an alkaline aqueous solution to obtain dehulled corn kernels, d) optionally, drying the dehulled corn kernels obtained in step c) to obtain dehulled corn kernels having a final moisture content equal to or below 15%.
  2. The method of claim 1, wherein the heating of step b) is performed at a temperature comprised between 60 °C and 90 °C.
  3. The method according to any one of claims 1 to 2 wherein the acid concentration of the acid aqueous solution of step b) is between 20 and 40 % v/v.
  4. The method according to any one of claims 1 to 3, wherein step b) is performed during a time equal to or less than 15 minutes.
  5. The method according to any one of claims 1 to 4, wherein the acid of the acid aqueous solution of step b) is selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, acetic acid and mixtures thereof.
  6. The method according to any one of claims 1 to 5 wherein the corn kernels:acid aqueous solution ratio is comprised between 1:1 and 1:5 m/v, preferably between 1:1 and 1:2 m/v.
  7. The method according to any one of claims 1 to 6, wherein the hydrolysis of step b) is performed with an acid aqueous solution at a concentration comprised between 25 and 38% v/v, while heating at a temperature comprised between 60 and 90 °C during a time comprised between 3 and less than 15 minutes.
  8. The method according to any one of claims 1 to 7, wherein the washing of step c) further comprises contacting the hydrolyzed-pericarp corn kernels obtained with an alcohol aqueous solution.
  9. The method according to any one of claims 1 to 8, wherein the hydrolyzed-pericarp corn kernels:alkaline aqueous solution ratio is comprised between 1:1 to 1:5 m/v ratio, preferably between 1:1 to 1:2 m/v ratio.
  10. The method according to any one of claims 1 to 9, wherein the alkaline aqueous solution of step c) is a metal hydroxide aqueous solution at 0.5-3% m/v.
  11. The method according to any one of claims 1 to 9, wherein the alkaline aqueous solution of step c) is a metal carbonate aqueous solution at 3-10% m/v.
  12. The method according to any one of claims 1 to 10, wherein step c) is performed with a sodium hydroxide aqueous solution at 0.5-3% m/v, during a time comprised between 30 and 120 seconds, preferably during 90 seconds.
  13. The method according to any one of claims 1 to 13, further comprising the purification of the waste acid aqueous solution obtained in step b) with a resin.
  14. The method according to any one of claims 1 to 14, further comprising the recirculation of the purified waste acid aqueous solution obtained according to claim 14.
  15. The method according to any one of claims 1 to 14, further comprising either first soaking with water or with an aqueous solution and then frying the dehulled corn kernels obtained in step c), or first soaking with water or with an aqueous solution and then frying the dehulled corn kernels obtained in step d).

Description

TECHNICAL FIELD The present invention relates to the field of food industry. More specifically, the present invention relates to the field of corn snacks industry, in particular to a method for obtaining dehulled corn kernels. BACKGROUND Corn (Zea mays L.) stands out as one of the most significant and widely cultivated cereals globally, covering approximately 197 million hectares of land annually. This makes it the second-largest crop worldwide, surpassed only by wheat. The popularity of this cereal is related to the nutritional and sensory properties of maize and its food-related products, especially snacks (C. A. Zugravu et al., Journal of Agroalimentary Processes and Technology, vol. 18, no. 1, pp. 8-12, 2012). According to a study described by C.A. Zugravu et al., more than 9 out of 10 adults report eating some type of salty snack regularly, at least twice a month. (D. Santiago-Ramos et al., J Cereal Sci, vol. 81, pp. 108-117, 2018). Corn fried snack products have seen increasing popularity and demand in recent years, with corn and tortilla chips being the most popular. These snacks are typically prepared by processing corn kernels through several unit operations such as cooking, steeping, soaking, and frying. (S. Garcia-Lara, et al. 'Development and Structure of the Corn Kernel', Corn: Chemistry and Technology, Third Edition, pp. 147-163, 2019). Corn and tortilla chips are often made by transforming corn into nixtamalized dough, which is then baked, fried, or extruded to create these popular snacks. However, there is another type of corn snack that has been gaining popularity, particularly in European and North American countries that is the previously hydrated and fried/toasted corn kernels, also known as "corn nuts" or "kikos" in Spain. Corn nuts are typically made from waxy corn kernels, as the amylose-to-amylopectin ratio in these varieties provides the desirable palatability of these snacks (J. Á. Granados-Arvizu et al., Bioresources, vol. 12, no. 4, pp. 7955-7963, 2017). These snacks are usually part of nut mix snacks or serve as the main ingredient in salty fried snacks. One of the main attractions of these products to consumers is that they have a similar appearance to whole raw kernels, whether baked or fried and, on the other hand, results in a more stable kernel. Therefore, preserving the integrity of the kernels to maintain their natural shape is a desirable attribute for consumers. In the traditional process of corn nuts, this attribute is compromised due to mechanical processes during the pericarp elimination that leads to an increased number of broken kernels, and thus turns out into a reduced yield of quality products. The pericarp, the outer layer that protects the kernels from external stress factors, also acts as a barrier to maintain kernel moisture. These carbohydrates form a hydrophobic barrier that helps the grain control moisture gradients. However, the presence of the pericarp results in undesirable properties during the corn nut preparation process. The pericarp hardens during cooking, increasing the hardness of the snacks and limiting the moisture the kernels can absorb, reducing the crunchiness of these snacks, which is often a desirable feature (Cereal Chem. 1992 | Alkali Debranning of Corn to Obtain Corn Bran). The first step in making corn nuts is to remove the pericarp from the corn kernels, which is primarily composed of cellulose, hemicellulose, and lignin. Traditional processes use highly concentrated acids, such as sulfuric acid at 98%, to hydrolyze the glycosidic bonds in cellulose and hemicellulose (N. Parris et al., J. Agric. Food Chem., vol. 49, no. 8, pp. 3757-3760, 2001). This hydrolysis breaks down the complex carbohydrates into simpler molecules, which can then be mechanically separated through processes such as centrifugation. Broken kernels are discarded as defective products, and the acid residues must be processed in a water treatment plant to be safely disposed of without causing environmental harm. While these methods effectively remove the pericarp, they can be harsh and environmentally unfriendly. Therefore, there is a need for more sustainable and less aggressive alternatives. BRIEF DESCRIPTION OF THE INVENTION The present application relates to a sustainable dehulling method that effectively removes the pericarp, along with zeins and sugars, from corn kernels. The inventors of the present patent application surprisingly found that high quality purified corn kernels can be obtained using lower acid concentrations in aqueous solutions, compared to traditional methods, without requiring any centrifugation step. The method of the invention significantly reduces the number of broken kernels and allows the cleaning and reutilization of the acidic aqueous solution, thereby minimizing the amount of waste generated. Conventional acid hydrolysis performed to dehulling corn kernels uses highly concentrated acid aqueous solutions, up to 98% v/v. In contrast, th