Process for dehydrating whole zea mays l. kernels by freeze-drying

Abstract

The invention relates to a process for dehydrating whole kernels of Zea mays L. (maize), which comprises: providing clean, nixtamilised whole maize kernels; boiling the maize kernels in 4 parts water to 1 part maize kernels at 94ºC for 210-300 mins; rinsing the boiled maize kernels with clean water; freezing the boiled whole kernels at between -30 and -40ºC for 10-12 h; applying vacuum to the maize kernels, maintaining freezing at between -28 and -33ºC at a pressure below 80 Pa for 1-2 h; dehydrating the maize kernels, maintaining freezing at between -28 and -33ºC at a pressure of 23-26 Pa for 10-14 h; and continuing to dehydrate the maize kernels by increasing the temperature to 48-53ºC at 23-26 Pa for 2-4 h.

Description

[0001] PROCESS FOR DEHYDRATING WHOLE GRAINS OF Zea mays L., BY FREEZE-DRYING

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to the field of food technology, because it provides a process for dehydrating whole grains of Zea mays L. (corn), by freeze-drying.

[0004] BACKGROUND OF THE INVENTION

[0005] Freeze-drying is a type of food preservation technology, based on drying certain materials by sublimating the moisture they contain; it consists of freezing the product, then removing the ice by sublimation and heating it under vacuum conditions, thus preventing the water contained in the food from entering the liquid phase.

[0006] The common problem that occurs when dehydrating grains or seeds for use in food is that these grains or seeds become dry, hard, tasteless, broken, etc. Specifically, these problems in the food called pozole are undesirable, since they considerably reduce the quality of said food.

[0007] In this regard, technologies for dehydrating grains and seeds have been developed, such as patent document W02005 / 036985A1, which describes an improved process and apparatus for nixtamalization and various uses. The process comprises the following stages: filling a cooking unit; applying a vacuum from 0 inHg to 29.92 inHg (0 to 1.013 bar); filling with water, lime, and microelements; impregnation; and pressure cooking, where the pressure ranges from 0 to 20 kg / cm². 2from 0 to 20°C, for 0 to 80 min; vacuum dehydration from 0'' Hg to 29.92'' Hg (0 to 1.013 bar), for 0 to 40 min; and draining of the product. As can be seen, this methodology is only for the nixtamalization of corn kernels, using vacuum and pressure; and it does not mention dehydration of the nixtamalized corn kernels by freeze-drying so that the dehydrated corn kernels have a texture that allows them to be rehydrated with hot water later.

[0008] For its part, patent document CN103535640B refers to a process for obtaining vegetable powder by low-temperature freeze-drying, specifically the powder comprises: 160-180 g of winter melon, 20-30 g of corn kernels, 3-4 g of hawthorn, 1-2 g of lily, 2-3 g of broom, 2-3 g of cornus, 1-2 g of astragalus, 2-3 g of mulberry, 1-2 g of kudzu root, 2-3 g of chestnut leaves, 1-2 g of buzia leaves, 2-3 g of angelica, 3-4 g of chuanxiong, 1-2 g of cassia twig, 7-8 g of coix seed powder, 4-5 g of milk powder, 0.4-0. 6 g of konjac gum and appropriate amounts of salt and sea buckthorn oil. It can be concluded that this patent document proposes a process for obtaining a dehydrated vegetable powder by freeze-drying, where corn is an ingredient, but it is obtained in a powdered state and not as a whole grain.

[0009] However, the aforementioned technologies have not solved the problem presented by grains and seeds when they are dehydrated; therefore, a process has been developed to dehydrate whole grains of Zea mays L. (corn) by freeze-drying. The characteristic details of the present invention are clearly shown in the following detailed description, along with the figure and examples included to illustrate the concept, technical advantages, and some preferred embodiments of the invention.

[0010] DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention relates to a process for dehydrating whole corn kernels (Zea mays L.) by freeze-drying. The resulting dehydrated corn kernels can be used in hydratable food mixtures.

[0012] In this invention, the term "corn kernels" refers to those corn kernels (Zea mays L.) that are already physiologically mature, at the base of which a black layer is observed and which have a moisture content of around 35%.

[0013] Therefore, an object of the present invention is a process for dehydrating whole grains of Zea mays L. (corn), by freeze-drying, where said process comprises the following steps:

[0014] i) provide whole grains of Zea mays L. (maize) nixtamalized, clean of lime residue, without husk and other impurities;

[0015] ii) rinse the corn kernels from the previous stage with clean water;

[0016] iii) cook the corn kernels from the previous stage in 4 parts clean water to 1 part corn kernels, at 94°C for a time range of 210 to 300 min, to obtain corn kernels with a soft consistency and a popped appearance;

[0017] iv) rinse the cooked corn kernels with clean water; v) freeze the whole, cooked corn kernels from -30 to -40°C, at 0 pressure, for 10 to 12 h;

[0018] vi) apply vacuum to the corn kernels, maintaining freezing from -28 to -33 °C to a pressure below 80 Pa, for 1 to 2 h;

[0019] vii) dehydrate the corn kernels by maintaining freezing at -28 to -33°C, at 23 to 26 Pa pressure, for 10 to 14 h; and

[0020] viii) continue dehydrating the corn kernels by increasing the temperature from 48 to 53°C, at 23 to 26 Pa of pressure, for 2 to 4 h.

[0021] A preferred embodiment of the process for dehydrating whole grains of Zea mays L. (corn), by freeze-drying, of the present invention, is when the cooking period is 240 to 255 min.

[0022] Another embodiment of the process for dehydrating whole grains of Zea mays L. (corn), by freeze-drying, according to the present invention, is that it may comprise a step of: removing foreign materials and / or contaminants, before step i).

[0023] In fact, the present process can begin with a conventional nixtamalization of corn kernels.

[0024] EXAMPLES

[0025] The following example is attached to illustrate the concept of the present invention, its technical effects, and some embodiments of the present invention; which should not be considered as a limitation to the scope of the present invention.

[0026] Example 1. Determining the cooking time of corn kernels.

[0027] To determine the optimal cooking time for Zea mays L. (corn) kernels for pozole preparation, a test was conducted using rehydration with water. The corn kernels were cooked at 94°C for varying cooking times, as illustrated in Table 1. At each cooking time, kernel hardness was measured using a potato masher. Three 100 g samples (3 replicates) were taken and mashed using a conventional potato masher. The amount of mashed mass that passed through the mashing machine's mesh was weighed, and the average of these weights was calculated. A fourth 100 g sample from each cooking time was also subjected to freeze-drying to measure its texture, rehydration, and kernel integrity parameters.

[0028] Table 1 shows the results of the corn kernel crushing test, where the best cooking time ranges from 210 to 300 minutes; the optimal range being 240 to 255 minutes, where the greatest quantities of crushed kernels were obtained. This indicates that when the kernels are cooked for these times, they are softer and therefore more likely to hydrate. Table 1. Average (g) of the quantity of crushed corn samples subjected to different cooking times at 94°C.

[0029]

[0030] The results of the freeze-drying process are presented in Table 2, where the best cooking time at 94°C ranges from 210 to 300 minutes, with the optimum range being 240 to 255 minutes. At these cooking times, the kernels had a firm, bloomy texture with ideal rehydration and intact kernels. Table 2. Physical characteristics of corn samples subjected to freeze-drying, after being cooked at different times at 94°C.

[0031]

[0032] Example 2. Process for dehydrating whole corn kernels by freeze-drying.

[0033] Once the cooking range of the corn kernels was established, a pilot trial of the process to dehydrate corn kernels was initiated, starting from the nixtamalization of the Zea mays L. (corn) kernels.

[0034] The corn kernels were mixed with clean water in a 1:4 ratio; the mixture was heated to 80°C for 2 hours, and then 2% lime was added relative to the dry weight of the corn kernels, stirring manually to disperse the lime in the mixture. The corn kernels were then nixtamalized for 60 minutes at boiling temperature.

[0035] After nixtamalization and cooling, the nixtamalized corn kernels were washed three times with clean water to remove the husk covering the kernels, lime residue, and other impurities. The corn kernels were then rinsed with clean water, resulting in a recovery of 1.6%.

[0036] Then the corn kernels were cooked in 4 parts clean water to 1 part corn kernels, until the kernels had a soft consistency and a popped or rosette appearance, which happened at around 240 min at 94°C; then the cooked corn kernels were rinsed with clean water.

[0037] The cooked corn kernels were then freeze-dried. To do this, the whole cooked corn kernels were frozen at -35°C, at 0 pressure, for 11 h; then a vacuum was applied to these corn kernels, maintaining the freezing at -28°C until a pressure of 80 Pa was reached, for 1.5 h; the whole corn kernels were dehydrated, maintaining the freezing at -28°C, at 25 Pa of pressure, for 12 h; and the dehydration of the corn kernels continued, increasing the temperature to 50°C, at 25 Pa of pressure, for 3.5 h.

[0038] By applying this process, we obtain whole, dehydrated corn kernels with a moisture content of 3 to 5%, which can have a long shelf life of up to 24 months. Another advantage of these corn kernels is that they acquire a firm, rosette-like texture and rehydrate well when soaked.

[0039] The corn kernels obtained through this process can be used in food mixtures, especially those prepared instantly by adding hot water to hydrate the ingredients, such as instant pozole, instant menudo, etc. They can also be used in food mixtures that don't require hot water; instead, they can be ground, pulverized, crushed, etc., to make atole, beverages, and other drinks.

Claims

CLAIMS 1. A process for dehydrating whole grains of Zea mays L. (maize), by freeze-drying, characterized in that it comprises the following steps: i) provide whole grains of Zea mays L. (corn) nixtamalized, clean of lime residue, without husk and other impurities; ii) rinse the corn kernels from the previous stage with clean water; iii) cook the corn kernels from the previous step in 4 parts clean water to 1 part corn kernels, at 94°C for a period of 210 to 300 min, to obtain corn kernels with a soft consistency and a popped or rosette appearance; iv) rinse the cooked corn kernels with clean water; v) Freeze whole, cooked corn kernels from -30 to -40°C, at 0 pressure, for 10 to 12 hours; vi) apply vacuum to the corn kernels, maintaining freezing from -28 to -33°C and down to a pressure below 80 Pa, for 1 to 2 h; vii) dehydrate the corn kernels by maintaining freezing at -28 to -33°C, at 23 to 26 Pa pressure, for 10 to 14 h; and viii) continue dehydrating the corn kernels by increasing the temperature from 48 to 53°C, at 23 to 26 Pa of pressure, for 2 to 4 h. The process of claim 1, wherein the cooking period is 240 to 255 min.

3. The process according to claim 1, characterized in that it comprises the step of: removing foreign and / or contaminating materials, before step i).

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