MXPA00002294A - Process for steeping corn and steepwater having a low reducing sugar content made therefrom - Google Patents

Abstract

A corn steeping process wherein the pH is adjusted to from about 4.2 to about 5.5 at a time between about 4 hours after fresh steepwater is introduced to about 1 hour before the separation of the steepwater from the corn. The process provides a steepwater having a low reducing sugar content while also providing good starch yields.

Description

PROCEDURE FOR MACERATING MAIZE AND MACERATION WATER. WHAT IT HAS A LOW CONTENT OF REDUCING SUGAR. OBTAINED FROM THE SAME BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an improvement in the wet milling process, to separate and recover corn products. More particularly, the present invention relates to an improved maceration process, which results in an improved grinding capacity, which provides high starch yields and a maceration water having a low reducing sugar content.

Description of the Related Art In the usual corn process, whole corn is soaked in water containing sulfur dioxide, at an elevated temperature and an acidic pH, for a prolonged period of time. During the soaking process, the soluble substances are extracted from the corn grains in the soaking water, where they ferment due to the presence of lactic acid bacteria in the water. Variables, such as soaking time, SO2 levels, water removal regimes, temperatures, etc., are used to promote separation. The resulting soaking water is used as a fermentation medium to produce a wide variety of products, such as enzymes, pharmaceuticals, etc.

Due to the many variations in the process, the water quality of corn maceration, found in the market, varies widely. An earlier description of a simple maceration process is described in the patent of E.U.A., RE 18,775, where acidulated water is added to a simple maceration tank. Following the separation of the starch, the water is reused in the process. Other prior descriptions of maceration processes, involving the recycling of the soaking water back into the process, are found in U.S. Patent Nos. 58, 2424, 1,655,395 and 1,960,985. U.S. Patent No. 2,232,555 describes a process in which the corn is soaked in acidified water, which has a pH of 4.5 to 6.9, at a temperature of 52 to 63ac, for about 5 to 15 hours, to supply an extract which contains substantial amounts of carbohydrates or sugars soluble in water. U.S. Patent No. 4,359,528 describes a process for producing soaking water having a high content of amino acids and which is useful in the production of penicillin. The process uses decreasing temperatures in a series of silos and high rates of water cycling to corn. A pH of 3.95 to 4.2 is reported. U.S. Patent No. 4,980,282 describes a process in which the soaking water is separated from the process, incubated to develop a biomass and this developed biomass is treated at a temperature between 40 and 48 s at a pH of at least 3.5 , approximately. While macerating water of varying degrees of utility is produced, a process has been found which provides a soaking water having a low reducing sugar content, necessary for use as a fermentation medium, while providing high yields of the starch.

SUMMARY OF THE INVENTION In accordance with this invention, a process for producing a maize soaking water is provided, this process comprises: a.) Introducing fresh soaking water, containing approximately 1,000 to 2,200 parts per million sulfur dioxide , to corn; b.) macerate the corn for a soaking time of more than 10 hours, at a temperature of approximately 48 to 52sc; c.) Separate the soaking water from corn, at a rate of 7.57 to 15.14 liters per 35,238 liters of ground corn; d.) adjust the pH by about 4.2 to 5.5 at a time, between about 4 hours after introducing the fresh soaking water until about 1 hour after the separation of the water from soaking the corn; e.) keep the soaking water separate, at a temperature of 48 to 52, between approximately 10 and 40 hours; and f.) evaporate the water from soaking the corn.

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the invention, reference will be made to the following detailed description, taken in conjunction with the accompanying drawings, in which: Figure 1 is a schematic side elevational view of a battery of used silos in a process of corn maceration; Figure 2 is a diagram showing starch performance as a function of soaking time and time of pH adjustment; Figure 3 is a diagram of curves showing incubation at different temperatures; and Figures 4 and 5 are graphs showing the percentage of reducing sugars in the soaking water in the incubation tanks, before and after the pH adjustments in the maceration.

DETAILED DESCRIPTION OF THE INVENTION When carrying out the process, the corn kernels, placed in silos, are put in contact with the soaking water, which contains about 1,000 to 2,200 parts per million of sulfur dioxide, to the corn This corn it will macerate for more than 10 hours and preferably between 20 and 48 hours, approximately, at a temperature of about 48 to 52SC. The maceration can be carried out in a batch or serial process, as shown in Figure 1. When carried out in series, the fresh soaking water is introduced successively into each of the silos in the series. In a normal maceration process, the pH is 3.8 to 4.1. It has been found in the process of this invention that by adjusting the pH from 4.2 to 5.5, in a time between about 4 hours after initially introducing the fresh soaking water, about 1 hour before the separation of the water from soaking the corn , followed by the maintenance of the separate soaking water at a temperature of about 48 to 52se, for between about 10 and 40 hours, supplies a soaking water having a low reducing sugar content. This feature makes the soaking water commercially attractive. Also, the yields of the starch are high, providing another advantage in that the starch yields are frequently tolerated when fermentation quality soaking water is produced.

Finally, the soaking water evaporates to supply a commercial product. In preferred embodiments of this invention, the pH is adjusted at a time between about 8 and 16 hours after the fresh soaking water is introduced. While the pH adjustment can be carried out in the course of the soaking water process, in another embodiment of the invention, the soaking water can be removed from the process, the pH adjusted and this soaking water is returned to the process . The following examples serve to illustrate the practice of this invention.

EXAMPLE 1 The maceration of light yellow corn, tooth No.2, was carried out in an industrial plant at different conditions, as described below, in two helical sets of maceration silos (batteries A and B). One of these batteries is shown in Figure 1 and comprises: Eight silos, Al a A8, made of stainless steel, with a filtration base B of total volume of 256,623 cubic meters and each with a diameter equal to 5.49 meters, equipped with : a pipe 11, which connects the base of a given silo to the head of the silo itself, and to the heads of the other seven silos, via a common discharge pipe C2, and a common filling pipe C3, which ensures the recycling the water within the silo itself or to any other silo, this pipe also serves to remove the water from soaking at a given time to a holding tank (not shown) through common pipes, shown in Figure 1; a bottom valve 14 for emptying the corn; a tube and cover heat exchanger 16, with a circulation pump P-1, which controls the flow of the liquid through the heating tubes in the heat exchanger 16 to the head of any other silo; eight water discharge valves V2, operated by solenoid, placed in the pipe 11 to segregate each silo from the common discharge line C2, which allows the movement of water through the battery; eight water filling valves VI, operated by solenoid, placed in the pipe 12, to segregate each silo from the common filling line C3, which allows the movement of water through the battery; an outlet Cl tube and a valve V3, which connect to an incubation tank (not shown) that receives a batch of 7.57 to 15.14 liters of water per 35 238 liters of ground corn, with a capacity large enough to supply 24 to 40 hours of incubation time, connected to each silo through tubes C2 and 11, with valves V2 that ensure the segregation of water between the silos; an inlet pipe 19 for water with SO2, adjusted to 1,000-2,200 ppm, from which the water with S02 is added as a batch by the opening valves V5 and Cl, which replace the discharged water; an inlet tube 18 for the addition of alkaline substances, for adjusting the pH in the range of 4.2 to 5.5 from which the alkaline substance is added inside the tube C2 by opening the valves V4, V2 and Vi of the same silo, and the pump Pl of departure; this allows adjustment of the pH of the water in any silo during part of the maceration cycle; a pH meter Z-l, to measure the pH of the water, which closes the valve V-4 when the pH reaches the desired set point. The silos are filled with the M maize and the process water moves countercurrent through the maceration silos, with the oldest maize in contact with the newer water. In the system, corn does not move from one maceration silo to another; only the water is advanced between the silos. After 24 to 40 hours of incubation, the soaking water is moved to an evaporator (not shown) and evaporated to 50% dry matter under a vacuum, at a temperature below 85 ° C.

The two identical sets of silos are operated at maceration temperatures of 48 to 52sc, S0 concentrations of 1,000 to 2,200 ppm and soaking water withdrawal rates of 7.57 to 15.14 liters per 35.23 liters of ground corn. The battery B was the control sample and the battery A was adjusted in the pH during the maceration at designated times. A sample of 100 grams of clean yellow corn, tooth No.2, was sealed in a 30.48 x 30.48 mm thin cloth and placed inside each silo in each battery, then the silo was filled with corn. The maize samples inside the thin cloth were exposed to maceration conditions identical to macerated corn in each battery. After designated times, during the maceration cycle, the samples were pulled from each battery, cooled to stop further maceration and tested on the grinding capacity, according to the procedure described in Cereal Chem. 70; 732-727 . The pH of the maceration water was adjusted in 4.6 in battery A, at several points during the maceration cycle, as indicated in Table I, while battery B was maintained at normal pH conditions of 3.8 to 4.1. This adjustment was made with the addition to 30% aqueous NaOH. The point in the maceration cycle where the pH was adjusted varies from 8 hours after the water with SO2 is introduced in the maceration process, through the inlet tube 18, up to 1 hour, before the final water withdrawal soaking. Table I shows the results of comparisons of starch yields between control samples of battery B and samples of battery A at various times during the maceration process. The graph of these data in Figure 2 shows the relationship between the maceration times of pH adjustment and their impact on the yields of the starch. It should be noted that the most effective point of the pH adjustment occurred between 8 and 16 hours after the water with SO2 was introduced to the maceration process, with a second adjustment made 1 hour before the water moved to the incubation tank.

TABLE I Yield of Starch in% by Weight of Corn Maceration Time (Control) (Hours *) 0 hours 8 hours 12 hours 16 hours 18 hours 12 - 59.48 62.31 61.37 - 16 59.46 62.25 64.92 63.93 62.56 20 63.21 62.18 66.18 64.64 62.93 24 64.90 64.63 67.01 65.16 60.83 28 65.95 - 68.15 - - * Time after water with SO21 was introduced to maceration EXAMPLE 2 Samples of 3,785 liters of the final soaking water were obtained from Battery A, while pH adjustments occurred 8 hours after the SO2 water was introduced to the water. maceration 200 ml aliquots of the samples were taken and the pH was adjusted from 4.9 to 5.0 and incubated at various temperatures ranging from 43 to 55 in the laboratory. The content of the reducing sugar was tested during the incubation, using the standard analytical method of the Corn Industries Research Foundation Division of Corn Refiners Association, Inc., Sixth Edition. D-52, J-58, Washington. This method measures the percent by weight of dry substance of reducing sugars in the samples. The results shown in Figure 3 indicate the reduction of reducing sugars in the soaking water, during the duration of the incubation cycle. Samples were maintained at or below 46SC during incubation and began exhibiting sensory attributes of alcohol fermentation, which is detrimental to the process of producing the fermentation grade water. In addition, the results of incubation temperatures above 50sc showed that a sufficient reduction in reducing sugars was not achieved. Therefore, the optimum temperature limits based on these results to reduce the amount of reducing sugars in the soaking water during incubation will be approximately 48 to 50sc.

EXAMPLE 3 Additional tests of reducing sugars were carried out in the process, to confirm the laboratory data. Table II and Figure 4 indicate the data that results from the actual content of the reducing sugars before any pH adjustment occurs in the actual maceration process. Aliquots were removed in a period of 3 months and 6 days. Consistently, the percentage of dry reducing sugars was above 10 percent and averaged over 12 percent. These levels are above the acceptable levels, generally required for the effective fermentation medium. Table III and Figure 5 indicate the actual percentage of reducing sugars after adjusting the pH in 4.5-4.8 in the maceration process, 8 to 16 hours after introducing the water with SO2 and with a second adjustment of the pH made to the water of maceration 1 hour before the movement of the water to the incubation. Soaking water temperatures in all processes were 48 to 508C. Aliquots were removed in a period of 5 months. The results indicate that the soaking water had an average reducing sugar content below 5 percent by weight of the dry substance.

TABLE II Incubation Tank # 3 Before Adjusting the pH in the Macerations TABLE III Incubation Tank # 3 After pH Adjustment in Macerations

Claims (8)

1. CLAIMS 1. A process for macerating corn, to produce water for soaking corn with a low content of reducing sugar, this process includes: a.) Introducing fresh soaking water, which contains approximately 1,000 to 2,200 parts per million dioxide sulfur, to corn; b.) macerate the corn for a soaking time of more than 10 hours, at a temperature of approximately 48 to 52sc; c.) Separate the soaking water from corn, at a rate of 7.57 to 15.14 liters per 35,238 liters of corn; d.) adjust the pH by about 4.2 to 5.5 at a time, between about 4 hours after introducing the fresh soaking water until about 1 hour after the separation of the water from soaking the corn; e.) keep the soaking water separate, at a temperature of 48 to 522C between approximately 10 and 40 hours; and f.) evaporate the water from soaking the corn.
2. 2. The process of claim 1, wherein the pH is adjusted at a time between about 8 and 16 hours after introducing the fresh soaking water.
3. 3. The process of claim 1, wherein the soaking water is removed from the process before adjusting the pH, this pH is adjusted and the soaking water, which has an adjusted pH, is returned to the process.
4. 4. The process of claim 3, wherein the pH is adjusted at a time between about 8 and 16 hours after introducing the fresh soaking water.
5. 5. The process of claim 1, wherein the maize is macerated for a maceration time between about 20 and 48 hours.
6. 6. The process of claim 5, wherein the pH is adjusted at a time between about 8 and 16 hours after introducing fresh soaking water.
7. 7. The process of claim 5, wherein the soaking water is removed from the process before adjusting the pH, this pH is adjusted and the soaking water, which has the adjusted pH, is returned to the process.
8. 8. The process of claim 8, wherein the pH is adjusted at a time between about 8 and 16 hours after introducing fresh soaking water.