Soluble corn steep

Abstract

The present invention relates to a process for treating a corn steep solution that allows obtaining a corn steep solution that can be easily atomized and that remains soluble after sterilization. The present invention also relates to a corn steep powder that can be obtained by this process.

Description

Technical Field

[0001] The present invention relates to a process for treating corn steep liquor that enables the obtaining of a corn steep liquor that can be easily atomized and maintains solubility after sterilization. The present invention also relates to corn steep powder that can be obtained by this process.

[0002] Prior Art The term "corn steep liquor", a term frequently used by those skilled in the art, means the concentrated steep water resulting from the steeping of corn.

[0003] The steeping of corn in water is the first step in starch extraction during wet starch processing. This steeping step allows the corn kernels to swell and enables the discard of the highly fermentable soluble substances contained in these kernels. It consists of placing the corn in a silo for a certain period of time in warm water containing a small amount of sulfur dioxide in order to facilitate the subsequent protein-cellulose-starch separation and to prevent the growth of unwanted microorganisms.

[0004] Two important phenomena occur simultaneously during steeping: the first consists of the diffusion of the soluble substances of the corn kernels into the steep water, and the second consists of the fermentation of this soluble substance in the steep water by lactic acid bacteria, and the above steeping conditions (presence of sulfite, reducing sugars, temperature) are favorable for the rapid development of this bacterial flora.

[0005] The main advantage of this concentrated steep water, commonly called "corn steep liquor" by those skilled in the art, lies in its composition of essential nutrients resulting from the transfer of soluble substances from the kernels. These nutrients constitute favorable factors for the growth of microorganisms and the production of secondary metabolites, making corn steep liquor an ideal source of nutrients for the fermentation industry.

[0006] Specifically, corn steep liquor is an organic nitrogen source selected by its amino acid distribution and form: free, peptide, or protein form, and a source with a delaying effect on carbon (lactic acid) and phosphate (phytate). When corn steep liquor is combined with one or more carbon sources (such as glucose, maltodextrin, starch, sucrose, etc.), the beneficial effects represented by corn steep liquor as a nutrient source for microbial growth and induction of secondary metabolites are increased by high contents of vitamins and trace elements.

[0007] Furthermore, this represents a reference substance in this field and constitutes a nutrient source that is relatively inexpensive compared to yeast extract, which is also used in human food and animal feed.

[0008] Furthermore, it is known that using corn steep liquor instead of a complex nitrogen source such as cotton or soy protein can substantially increase the production yield of antibiotics.

[0009] However, liquid-form corn steep liquor causes sedimentation problems over time, which is particularly problematic for product transportation, storage, and pumping. The above products must be stored in agitation and temperature control tanks to limit changes in their composition. This is especially true when corn steep liquor is consumed in small amounts at a time by several fermentation industries. In this case, it is particularly important to control its storage. Then, the production of dry-form corn steep liquor is envisioned.

[0010] Spray drying of corn steep liquor is a technique that is overwhelmingly used. This technique, which is very widely used in the industry, enables the drying of products that are considered difficult to dry, such as heat-sensitive products or highly hygroscopic products. However, in the case of corn steep liquor, those skilled in the art have encountered problems with sticking. Specifically, the drying of some products is not a problem at all, that is, the powder exits uniformly from the drying chamber or tower and has a satisfactory appearance and satisfactory flow characteristics. However, the corn steep liquor rich in amino acids and hygroscopic substances is prone to sticking.

[0011] This sticking is revealed by deposits at various levels in the drying chamber and auxiliary equipment, and these deposits result in product loss and degradation, which may require production stoppage in a costly cleaning cycle in terms of time, materials, and labor. Sticking can also occur after the drying process when the powder loses its fluidity and forms lumps after a certain period of storage.

[0012] Therefore, due to the particular hygroscopicity of organic acids and the salts contained therein, especially potassium lactate present in a high proportion, it is very difficult to atomize corn steep liquor (Wright K.N. Nutritional properties and feeding value of corn and its by-products. In: Corn Chemistry and Technology, pages 447 - 478 Watson, S.A. and Ramstad P.S. (Eds). Amer. Assoc. Cereal Chem., St Paul, MN, USA).

[0013] The applicant has already addressed this problem and has proposed a solution described in European Patent No. 1043337. Advantageously, the corn steep powder according to European Patent No. 1043337 has a metal ion content of 1% to 5% by weight (dry / dry). The addition of this metal ion can facilitate the atomization of corn steep without any adhesion. As a result, the nutritional quality of the corn steep powder according to the present invention is not only maintained but also improved. Therefore, these nutritional qualities, combined with the ease of storage and introduction, are understood to be advantages that cannot be ignored, for example, in the preparation of culture media for the fermentation industry.

[0014] For use in the fermentation industry, this atomized corn steep liquor must be redissolved in an aqueous solvent together with all the nutrients to be metabolized by the microbial strain whose production is desired. Sediments appear during the resuspension process and can account for up to 15% of the dry matter.

[0015] The amount of sediment is amplified by the next step of sterilization of the fermentation medium. This step, aimed at removing unwanted microorganisms by the application of heat, results in the substantial formation of insoluble particles in particular, which can correspond to up to 30% of the dry matter.

[0016] This problem has also been examined, especially in the Master of Science thesis "The purification of corn steep liquor as a fermentation feedstock by ultrafiltration" by E. Govender published in 2010. E. Govender has proposed several solutions consisting of various pretreatments such as adjusting the pH of the corn steep liquor to 7 by the addition of ammonium hydroxide, or using a decanter centrifuge or a rotary screen. After these pretreatments of the corn steep solution, an ultrafiltration step follows. However, adjusting the pH to 7 can reduce the amount of sediment in the corn steep after sterilization, but most of the nutrients are removed by this pretreatment and this corn steep is not recommended for fermentation.

[0017] Those skilled in the art are still seeking a process that enables the production of corn steep liquor that can be easily atomized, maintains solubility after sterilization, and can be used for fermentation purposes.

[0018] For the sake of the applicant's reputation, it should be said that the applicant has addressed all these problems and found a solution to the present invention, which will be described in more detail in the following chapter.

Summary of the Invention

[0019] The present invention is a process for treating corn steep liquor, comprising the following steps: a) adding a neutral salt of a divalent cation, preferably a salt of magnesium or calcium, more preferably calcium sulfate or magnesium sulfate, to the corn steep liquor; b) adjusting the pH of the corn steep liquor to 6 - 8, preferably by adding potassium hydroxide or ammonium hydroxide; c) separating the liquid phase and the solid phase of the solution obtained in step b); d) drying the liquid phase obtained in step c), preferably by spray drying, to obtain corn steep powder. Preferably, the neutral salt of the divalent cation is added to the corn steep liquor at a temperature of 20°C - 60°C. The separation of the liquid phase and the solid phase in step c) is preferably carried out by plate centrifugation. The amount of the divalent salt is preferably 0.5 - 3.5 mol / kg of the dry matter of the corn steep liquor, preferably 1 - 3 mol / kg of the dry matter of the corn steep liquor, and even more preferably 1.5 mol / kg of the dry matter of the corn steep liquor.

[0020] In another aspect, the present invention relates to a corn steep powder obtainable by the above process. Preferably, the corn steep powder is characterized in that the amount of protein is 20% - 40%, preferably 27% - 33%, of the dry weight of the corn steep powder. The present invention will be better understood from the detailed description to be found in the following chapter.

Brief Description of the Drawings

[0021] Other features, details, and advantages will become apparent by reading the following detailed description and analyzing the accompanying drawings.

[0022]

Figure 1

[0023]

Figure 2

Modes for Carrying Out the Invention

[0024] The term "neutral salt of a divalent cation" means any ionic compound composed of a divalent cation (i.e., having 2 units of positive charge) and an anion, forming a product having no net charge.

[0025] A salt of a divalent cation is said to be neutral if it does not affect the pH of the solution when the salt is dissolved.

[0026] For the purposes of the present invention, the term "corn steep liquor" or "corn steep solution" means the liquid fraction composed of the immersion water from a silo used for immersing corn kernels. The non-concentrated liquid fraction preferably has a dry matter content of about 15%, and a protein nitrogen content expressed as about 45% of N6.5 by dry matter weight, a phytic acid content of 9% - 10% by dry matter weight, a lactic acid content of 25% - 30% by dry matter weight, and an ash content of about 15% - 20% by dry matter weight.

[0027] Regarding the object of the present invention, the term "powdery" means a product having a dry matter content exceeding 95% and characterized by a particle size distribution profile, a bulk density, and further a tapped density. The powder is obtained from a drying process such as spray drying (single or multiple effect spray dryer, or spray dryer with a belt after drying).

[0028] Regarding the object of the present invention, the term "soluble" means that a solid can be dissolved in a liquid solvent without insoluble particles or turbidity.

[0029] Regarding the object of the present invention, the term "sterilization" means a process step that aims to remove any microorganisms from a preparation. This technique involves, for example, heating at a high temperature of 100 °C to 180 °C, particularly at least 121 °C, for at least 20 minutes.

[0030] The proportion of insoluble particles is preferably measured by the method of Test A described below. The corn steep liquor is first adjusted to pH 7 ± 0.5 with HCl and NaOH. - Place 200 g of corn steep liquor in a 500 mL Erlenmeyer flask stoppered with a foam stopper covered with aluminum foil. The Erlenmeyer flask is sterilized using a wet steam autoclave according to a schedule of 121 °C for 20 minutes. - Then, filter the corn steep liquor through a cellulose acetate filter with 0.22 micron pores (the weight of which is known). - Freeze-dry the filter and then measure its weight. Proportion of insoluble particles (%) = ((weight of the dried final filter - weight of the initial filter) / initial weight of the corn steep solution) × 100.

[0031] The subject of this patent application is a process for treating a corn steep solution that enables the production of a corn steep liquor that can be easily spray-dried and maintains solubility after sterilization, the following steps: - a) adding a neutral salt of a divalent cation to the corn steep liquor; - b) adjusting the pH of the corn steep liquor to a value between 6 and 8; - c) separating the liquid and solid phases of the solution obtained in step b); - d) drying the liquid phase obtained in step c) to obtain corn steep powder; The process comprises the steps.

[0032] The first step of the process consists of adding a neutral salt of a divalent cation to the corn steep liquor. For this purpose, any commercially available corn steep liquor may be used.

[0033] Preferably, the corn steep liquor is produced from corn kernels by a process conventionally used in the prior art known as "steeping" of corn. As previously described herein, the steeping of corn in water is the first step in the starch extraction during wet starch processing. This steeping step causes the corn kernels to swell and makes it possible to discard the highly fermentable soluble substances contained in these kernels. It consists of placing the corn in a silo for a certain time in warm water containing a small amount of sulfur dioxide in order to facilitate the subsequent protein-cellulose-starch separation and to prevent the growth of unwanted microorganisms.

[0034] Two important phenomena occur simultaneously during steeping: the first consists of the diffusion of the soluble substances of the corn kernels into the steeping water, and the second consists of the fermentation of these soluble substances in the steeping water by lactic acid bacteria. The above steeping conditions (presence of sulfite, reducing sugars, temperature) are favorable for the rapid development of this bacterial flora.

[0035] Preferably, those skilled in the art may use the teachings of U.S. Patent No. 4,359,528 belonging to the applicant, or Patent Applications European Patent Nos. 724,841 and 819,702.

[0036] Preferably, the dry matter of the corn steep liquor is 5% to 25% dry matter, preferably 10% to 20%, more preferably 15%.

[0037] A neutral salt of a divalent cation is added to the corn steep liquor.

[0038] Preferably, a magnesium salt or a calcium salt is used. In particular, a magnesium salt is preferred in order to avoid a white salt precipitate containing tricalcium phosphate in a fermentation medium containing phosphorus and / or potassium. Among neutral magnesium salts, magnesium sulfate is highly preferred.

[0039] The amount of the neutral salt of the divalent cation, preferably the magnesium salt, more preferably magnesium sulfate, added to the corn steep liquor is 0.5 to 3.5 mol / kg of the dry matter of the corn steep liquor, preferably 1 to 3 mol / kg of the dry matter of the corn steep liquor, more preferably 1.5 mol / kg of the dry matter of the corn steep liquor. The amount of the neutral salt of the divalent cation should be understood as the amount of the anhydrous salt in the present invention.

[0040] An additional amount of salt may be added. The product functions similarly with respect to sterilization stability and fermentation performance. However, an increase in the salt content is disadvantageous for the fermentation industry.

[0041] In an even more preferred method, the concentration of magnesium sulfate heptahydrate is 4% to 8%, preferably 4% to 6%, more preferably 4.5% of the dry weight of magnesium sulfate heptahydrate with respect to the weight of the dry corn steep.

[0042] The neutral salt of the divalent cation, preferably the neutral magnesium salt, more preferably magnesium sulfate, can be added to the corn steep liquor in powder form or in a pre-diluted form in an aqueous solvent.

[0043] After the addition of the salt of the divalent cation, a stirring step is recommended to obtain a homogeneous dispersion of the neutral salt of the divalent cation defined previously with the corn steep liquor. This stirring step has conventionally been carried out in a suitable container (such as a tank) equipped with a stirring system, for example, a rotating shaft equipped with an impeller.

[0044] The addition is preferably carried out by adjusting the temperature of the corn steep liquor to 20°C to 60°C, preferably 30°C to 50°C, and even more preferably 40°C. For this purpose, any temperature adjustment system can be used, such as the use of a "coil" type heat exchanger to which hot water or steam is supplied.

[0045] The second step of the process of the present invention is to neutralize the pH of the corn steep liquor, that is, to adjust the pH of the corn steep liquor to pH 6 to 8, preferably pH 6.5 to 7.5, and even more preferably pH 7.

[0046] To carry out this step, one skilled in the art may add any basic reagent well-known in the prior art to the corn steep liquor.

[0047] Preferably, this basic reagent is selected from the group consisting of potassium hydroxide and ammonium hydroxide. The use of ammonium hydroxide is advantageous because it allows a little more nitrogen to be supplied for fermentation. However, the use of ammonium hydroxide produces a final product with a slightly more acidic pH, which requires potential initial pH adjustment by the user. The use of potassium hydroxide makes it possible to avoid this final pH variation.

[0048] For the first step, while adjusting the temperature of the solution, the pH adjustment is carried out with stirring. The apparatus is of the same nature as that used in the previous step (a tank with stirring and temperature control).

[0049] Therefore, in one particular embodiment, the addition of the magnesium salt in the first step and the pH adjustment in the second step may be carried out together.

[0050] Preferably, the temperature of the corn steep liquor during pH adjustment is 15°C to 25°C, preferably 20°C.

[0051] Preferably, during pH adjustment, the corn steep liquor requires stirring to enable the formation of insoluble compounds. The stirring time is preferably 1 minute to 60 minutes, preferably 10 minutes to 50 minutes, and even more preferably 20 minutes to 40 minutes.

[0052] The third step is to separate the liquid phase and the solid phase of the solution obtained in the previous step.

[0053] For this purpose, a person skilled in the art may use any well-known techniques including filtration (cross-flow, membrane, dead-end filtration, etc.) and sedimentation (static, centrifugal sedimentation, etc.).

[0054] Preferably, a person skilled in the art will use centrifugation, particularly "plate" centrifuge technology.

[0055] The solid phase, also called sludge or precipitate, generally contains 30% to 50% (dry / dry) mineral ash, and the remainder is mainly composed of phytic acid, lactic acid, and protein. This sludge contains approximately 50% of the protein initially contained in the corn steep liquor. This reduction is the result of the improved stability of the supernatant fraction.

[0056] The liquid phase, also called the supernatant, concentrates the remaining soluble compounds.

[0057] The liquid phase of the liquid corn steep has improved the stability against heat treatment and improved atomization. When this liquid phase is used, the fermentation performance is further maintained.

[0058] The last step is to dry the liquid phase obtained in the previous step to obtain corn steep powder.

[0059] For this purpose, a person skilled in the art may use any technique well-known in the prior art.

[0060] The applicant of the present invention has demonstrated that the corn steep powder according to the present invention can be advantageously produced, for example, by using an atomization tower of the Niro type, preferably a multiple-effect atomization tower.

[0061] An air inlet temperature of 150°C to 250°C and a flow rate of the incoming substance such that the temperature of the air exiting the tower is 60°C to 100°C can preferably be selected.

[0062] The corn steep powder obtained according to the process of the present invention can then be formed into tablets, for example, using an alternating press in the presence of a lubricant.

[0063] In a preferred embodiment, the dry matter ratio of the corn steep powder according to the present invention is more than 80%, preferably more than 85%, and even more preferably more than 90%.

[0064] The dry matter is measured by any protocol that may be available to a person skilled in the art. Preferably, the following "drying" method is used. - First, weigh the sample and measure the mass m1 in grams. - Place the sample in a heating chamber to evaporate the water until the water has completely evaporated and the mass of the sample has stabilized. Preferably, the temperature is 105°C under atmospheric pressure. - Weigh the final sample and measure the mass m2 in grams. - Dry matter = (m2 / m1) × 100

[0065] In a preferred embodiment, the total protein content of the corn steep powder is 20% to 40%, preferably 27% to 33%, and the ratio is based on dry matter.

[0066] The total protein content can be determined by any protocol well-known to those skilled in the art, for example, by analysis of the total amount of amino acids. Preferentially, the total nitrogen amount is analyzed according to the Dumas method and the value is multiplied by a factor of 6.25.

[0067] Finally, the present invention relates to the use of this soluble corn steep in any industry, particularly the large-scale fermentation industry.

[0068] The corn steep powder according to the present invention can be advantageously used as a nutrient in the preparation of a culture medium for the fermentation industry. It can also be used in the fields of food or animal nutrition, or other fields.

[0069] Beside its sterilization stability and in contrast to the prior art corn steep powder, the corn steep according to the present invention preserves its initial biochemical characteristics. Furthermore, it is advantageously compressible and it is particularly attractive in industrial implementation due to the risks and drawbacks associated with the handling of powders. Furthermore, the tablet form allows for an accurate dosage during the preparation of the culture medium.

[0070] The present invention is better understood by the following examples, which are not intended to be limiting and merely present some of the embodiments and some of the advantageous characteristics of the corn steep powder according to the present invention.

Examples

[0071] Example 1: Production of a corn steep solution according to European Patent No. 0026125, which is prior art For the production of the corn steep liquor, an array of silos composed of 7 stainless steel silos S1 to S7, each having a bottom filter, a total volume of 33 liters and a diameter of 25 cm, and capable of being filled with corn M, was used (Figure 1): - A level probe 10, and - A pipe system 11 that connects the bottom of a given silo, on the one hand, to the head of the next silo via line 12 and, on the other hand, to the head of the silo itself or towards the next silo via line 13 for the recirculation of the liquid phase of the silo itself, and which is also used, if necessary, to drain the immersion water. - A large-diameter underflow gate 14 for emptying the silo of corn. - As many temperature-controlled water baths 16 as there are circulation pumps P for circulating the liquid phase from a given silo through a heating coil to the head of the next silo or the silo under consideration. - Seven sets of two solenoid valves 17 and 18, each arranged in pipe systems 12 and 13 and controlled by level probes, to ensure that the corn is completely covered and the liquid moves through the silo arrangement. - A line 19 for introducing water containing sulfite adjusted to 1.5 g / L of sulfur dioxide, from which the water containing sulfite is distributed at a constant flow rate and, at each silo, by opening the corresponding valve V1, a constant circulation level (liters of water per kilogram of corn) is ensured. - Twenty-liter tanks (not shown), each connected to each silo via lines C1 to C7 branched onto line 11 of each silo, for recovering the immersion water from the silo before grinding the corn, and the direction of the immersion water exits from a given silo towards the pipe system 11 or towards line C provided by valves V2 and V3 respectively. - An evaporator (not shown) of the type sold by Kurt Herbert Apparate und Maschinenbau Lahr, Baden. Every day, the recovered immersion water is evaporated using this vacuum evaporator to 50% of the dry matter at a temperature below 60°C.

[0072] The corn used is French corn from a normal supplier in the starch industry. The selected immersion time is 40 hours and the SO2 content is set at 1.5 g / litre.

[0073] The temperature is set at 48 °C ± 1 °C throughout the array of silos. The operation in the five silos that are emptied every 8 hours takes 40 hours.

[0074] The water circulation level was gradually increased from 0.8 to 1.0 - 1.5 and 1.8 litres per kg of commercially available corn.

[0075] Next, an attempt is made to atomize the corn steep liquor or immersion water thus obtained in a Niro tower under the following conditions: inlet temperature, 200 °C - outlet temperature, 96 °C - turbine speed, 15,000 rpm - evaporation capacity, 80 litres / hour.

[0076] Even by varying the parameters, it was not possible to obtain satisfactory atomization. The powder adhered rapidly and strongly to the atomization chamber, creating a layer of product. The atomization process was rapidly interrupted by this layer of product and could not be sustained for a long period. It is not possible to consider industrial scale-up.

[0077] Example 2: Treatment with salts of divalent cations of the corn steep solution A corn steep solution containing 50% dry matter is prepared by carrying out the process described in Example 1 and then concentrated using a vacuum evaporator. Then, 3.2% by weight (dry / dry) of the salt MgO of divalent cations is added thereto in the form of a 100 g / L suspension at a temperature adjusted to 50 °C with stirring into the tank.

[0078] The pH of the MgO-rich corn steep liquor thus obtained is 5.7.

[0079] Next, atomization is carried out in a Niro tower under the following conditions: inlet temperature, 200 °C - outlet temperature, 96 °C - turbine speed, 15,000 rpm - evaporation capacity, 80 liters per hour.

[0080] The lactic acid content of the obtained corn steep is 14% by weight. The particles do not adhere to the walls of the atomization chamber. The powder has a high density and flows rapidly down from the cyclone.

[0081] Example 3: Corn steep solution subjected to the step of adjusting to pH 7 A corn steep liquor containing 50% dry matter is prepared by carrying out the process described in Example 1.

[0082] Next, the required amount of ammonium hydroxide (NH4OH) is added to the tank while stirring at a temperature adjusted to 50 °C to obtain pH 7.

[0083] After stirring for 10 minutes, the corn steep solution is sent to a PS ultrafiltration membrane having a cut-off threshold of 30 kDa and disposed on a cross-flow filtration skid.

[0084] Next, atomization is carried out in a Niro tower under the following conditions: inlet temperature, 200 °C - outlet temperature, 96 °C - turbine speed, 15,000 rpm - evaporation capacity, 80 liters per hour.

[0085] Even by varying the parameters, it was impossible to obtain satisfactory atomization. The powder adheres rapidly and strongly to the atomization chamber, creating a layer of the product. The atomization process is rapidly interrupted by this layer of the product and cannot be sustained for a long period. It is impossible to consider industrial scale-up.

[0086] Example 4: Treatment of corn steep solution according to the present invention A corn steep liquor containing 50% dry matter is prepared by carrying out the process described in Example 1.

[0087] After dilution to 15%, 5% w / w potassium hydroxide (50%) and 4.2% w / w MgSO4 are added thereto while stirring in the tank at a temperature adjusted to 40 °C to obtain a pH of 7. Alternatively, 3.5% w / w ammonium hydroxide (20.5%) and 4.2% w / w MgSO4 may be added.

[0088] After stirring for 10 minutes, the corn steep liquor is cooled to 20 °C and then fed to a Westfalia separator NA7 type plate centrifuge in the form of "continuous sediment removal" as a nozzle separator. The separator is equipped with four 0.3 mm discharge nozzles. The bowl speed is 8400 rpm and the acceleration is estimated to be about 6000 g. The separator is fed at a flow rate of about 250 L / hour with a back pressure of 0.5 bar.

[0089] The supernatant is then dried directly by atomization. Atomization is carried out in a Niro tower under the following conditions: inlet temperature, 200 °C - outlet temperature, 96 °C - evaporation capacity, 20 liters / hour.

[0090] Example 5: Comparison of the stability of various corn steep liquors against sterilization The stability of various products obtained in the above examples against sterilization was compared. Specifically, when subjected to the conventional sterilization schedule in the fermentation industry, insoluble precipitates appear in the prior art corn steep liquor precursors. The tests for comparing various samples are as follows: The corn steep liquor precursor is first adjusted to pH 7 ± 0.5 with HCl and NaOH. Next, the above corn steep liquor precursor is photographed. The proportion of insoluble particles is measured by the following Test A: - 200 g of the corn steep liquor precursor is placed in a 500 mL Erlenmeyer flask stoppered with a foam stopper covered with aluminum foil. - The Erlenmeyer flask is sterilized using a wet steam autoclave according to a schedule of 121 °C for 20 minutes. - Next, the corn steep liquor is filtered through a cellulose acetate filter having pores of 0.22 microns (the weight of which is known). - The filter is lyophilized and then its weight is measured. The tare weight of the filter is weighed, which enables determination of the amount of insoluble matter that appeared after drying the filter under vacuum. Percentage of insoluble particles (%) = ((weight of the final dried filter - weight of the initial filter) / initial weight of the corn steep solution) × 100.

[0091] For the purpose of comparison with the values obtained in Step 1, the corn steep filter is photographed.

[0092] Table 1 below summarizes the relative performance of the various corn steep liquors presented in the above examples.

[0093]

Table 1

[0094] [Table 1]

[0095] As explained in the detailed section, the treatment of the corn steep solution according to the present invention is the only treatment that enables easy atomization of the solution while limiting the appearance of precipitates after sterilization (less than 1% according to the above tests).

[0096] Example 6: Comparison of the effectiveness of various corn steep liquors in fermentation The reference strain here is Lactobacillus delbrueckii.

[0097] The preculture is prepared in 100 mL of MRS medium (Man-Rogosa-Sharpe agar) containing cysteine in a 250 mL Erlenmeyer flask with stirring under anaerobic conditions at 37 °C and pH 6.8 - 7.

[0098] Once the pre-culture is complete, the 3-liter fermenter is seeded with 1000 mL containing glucose at a final concentration of 50 g / L, 3 - 1 g / L of K2HPO4 - KH2PO4, 0.5 g / L of MgSO4·7H2O, and 1 g / L of Tween 80.

[0099] Next, corn steep is added in an amount of 0.5 g / L. The cultivation is carried out at a temperature of 37 °C and a pH initially adjusted to 6.4 with 5N NaOH, and under anaerobic conditions in an inert atmosphere of nitrogen.

[0100] To ensure the comparative performance of the various corn steep solutions produced in the above examples, colonies are counted during fermentation (performed by culturing in Petri dishes and expressed as cfu / mL). The counting results are shown in Table 2 below.

[0101]

Table 2

[0102] [Table 2]

Claims

1. A process for treating a corn steep solution, comprising the following steps: a) adding a neutral salt of a divalent cation to the corn steep solution; b) adjusting the pH of the corn steep solution to a value between 6 and 8; c) separating the liquid phase and the solid phase of the solution obtained in step b); d) drying the liquid phase obtained in step c) to obtain corn steep powder; characterized in that the neutral salt of the divalent cation is added to the corn steep solution at a temperature between 20 and 60 °C.

2. The process according to claim 1, characterized in that the neutral salt of the divalent cation is a salt of magnesium or calcium.

3. The process according to claim 1 or 2, characterized in that the neutral salt of the divalent cation is added to the corn steep solution at a temperature between 30 and 50 °C.

4. The process according to any one of claims 1 to 3, characterized in that the pH is adjusted to between 6 and 8 by adding potassium hydroxide or ammonium hydroxide.

5. The process according to any one of claims 1 to 4, characterized in that the separation of the liquid phase and the solid phase in step c) is carried out by plate centrifugation.

6. The process according to any one of claims 1 to 5, characterized in that the drying in step d) is carried out by atomization.

7. The process according to any one of claims 1 to 6, characterized in that the amount of the divalent salt is 0.5 to 3.5 mol / kg of the dry matter of the corn steep solution.

8. Corn steep powder obtained by the process according to any one of claims 1 to 7.

9. The corn steep powder according to claim 8, characterized in that the amount of protein is 20% to 40% of the dry weight of the corn steep powder.

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