Patent Application
20200407244
The field of the disclosure relates to methods for producing a food product and, in particular, methods that involve use of a cross-flow filtration module to recycle wastewater effluent and/or to recover antioxidant compounds from the wastewater effluent.
Nixtamalization processing of grains by alkaline cooking is conventionally used to produce hominy. Hominy may be used as a food product or hominy may be ground to form masa either in the form of dried flour or wet dough. Alkaline (e.g., lime) cooking uses a substantial amount of water, both for cooking of the grain and for washing of the grain after cooking. The wastewater effluent (commonly referred to as “nejayote”) is discarded which requires costly treatment before disposal into the environment.
A need exists for methods for producing food products such as masa that allow the wastewater effluent produced during processing to be recycled and/or that allow compounds to be recovered from the wastewater effluent for further use.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
One aspect of the present disclosure is directed to a method for producing a food product from a cereal grain. The cereal grain is introduced into an alkaline cooking system to contact the cereal grain with an alkaline solution to partially hydrolyze the cereal grain. The partially hydrolyzed cereal grain is dewatered in a dewatering system to form a food precursor and a wastewater effluent. The food precursor is processed to form a food product. The wastewater effluent is introduced into a cross-flow filtration module to produce a permeate. The permeate is depleted in impurities relative to the effluent. At least a portion of the permeate is introduced into (1) the alkaline cooking system for partially hydrolyzing the cereal grain and/or (2) the dewatering system for dewatering the partially hydrolyzed cereal grain.
Another aspect of the present disclosure is directed to a method for recovering antioxidants from a wastewater effluent. The wastewater effluent is a by-product of the alkaline hydrolysis of a cereal grain. The wastewater effluent is introduced into a cross-flow filtration module. The cross-flow filtration module includes a porous filtration membrane which retains a portion of the effluent as retentate and allows a portion of the effluent to pass through the filtration membrane as permeate. The retentate or permeate is enriched in antioxidants relative to the wastewater effluent. The antioxidant compounds are extracted from the permeate or from the retentate.
Yet another aspect of the present disclosure is directed to a method for producing a food product and an antioxidant composition from a cereal grain. The cereal grain is contacted with an alkaline solution to partially hydrolyze the cereal grain. The partially hydrolyzed cereal graM is dewatered to form a food precursor and a wastewater effluent. The food precursor is processed to form a food product. The wastewater effluent is introduced into a filtration module to concentrate antioxidants in a permeate or retentate. At least a portion of the permeate is recycled to produce the food product and the antioxidant composition.
In yet a further aspect, the present disclosure is directed to the antioxidants, or a composition comprising the antioxidants, which is obtained from one or more of the methods described herein and above.
Various refinements exist of the features noted in relation to the above-mentioned aspects of the present disclosure. Further features may also be incorporated in the above-mentioned aspects of the present disclosure as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments of the present disclosure may be incorporated into any of the above-described aspects of the present disclosure, alone or in any combination.
Corresponding reference characters indicate corresponding parts throughout the drawings.
Provisions of the present disclosure relate to methods for producing a food product from a cereal grain. A wastewater effluent generated during production of the food product is contacted with a cross-flow filtration module having a porous filtration membrane. The porous filtration membrane may include a substrate made of stainless steel or a nickel alloy with a sintered titanium dioxide coating bonded to the substrate.
While the methods of the present disclosure may be described with respect to production of masa from a cereal grain such as corn, the methods are applicable to production of any food product from a cereal grain unless stated otherwise. Other cereal grains which may be processed in accordance with embodiments of the present disclosure include, for example, wheat, rice, barley, sorghum, millet, rye, oats, teff, buckwheat, quinoa, and amaranth.
Referring now to
The pH and/or temperature at which the grain is cooked may vary depending on the type of grain and may be selected such that the cooked grain 5 is suitable for downstream dough formation and for digestion. In some embodiments of the present disclosure (e.g., in some embodiments in which corn is processed), the grain is cooked at a pH of 10.5 or more (e.g., 10.5, 11 or 11.5) and/or at a temperature of at least about 60° C. Whole kernels of grain may be cooked (e.g., without particle size reduction) with the ratio of alkaline and grain being controlled before and/or during the cooking process. The rates at which grain and alkaline are metered into the alkaline cooking system 4 may be controlled with a gravimetric feeder such as a “loss in weight feeder,” which may be referred to herein simply as a “macerator”. The cooking process partially hydrolyzes the cereal grain to soften the grain and make it suitable for dough formation and for digestion.
The cooked grain 5 is strained and/or dewatered in a dewatering system 20. Optionally, the dewatering system may include a wash system in which grain is contacted with wash water 7 and dewatered (e.g., wash screens or the like). The dewatering operation produces a wastewater effluent 8 that is removed from the dewatering system 20. The dewatered, cooked grain or “food precursor” 9 (e.g., nixtamal when corn is processed) is further processed to produce a food product. For example, the food precursor 9 may be ground to produce a food product 13. A hammermill may be used to grind the food precursor 9. The ground food product 13 (e.g., masa) may be further processed such as by drying into flour or by preparing a dough. The food product 13 may be stored and/or packaged.
The wastewater effluent 8 from the dewatering system 20 is introduced into a cross flow filtration module 24. The effluent 8 introduced into the filtration module 24 may have a pH and/or temperature corresponding to the pH and/or temperature at which the grain was cooked. In some embodiments (e.g., some embodiments in which corn is processed) the wastewater effluent has a pH of about 10.5 or more (e.g., 10.5, 11 or 11.5).
In some embodiments, the pH of the wastewater effluent 8 is not modified between separation of the wastewater from the food precursor 9 in the dewatering system 20 and introduction into the cross-flow filtration module 24. The wastewater effluent 8 may be directly introduced into the cross-flow filtration module 24 after washing the partially hydrolyzed cereal grain 5 (e.g., without other processing such as temperature reduction, pH reduction, and the like). The wastewater effluent 8 may have a temperature of at least about 40° C. (e.g., 60° C. or more) when introduced into the module 24. The wastewater effluent 8 may optionally be cooled (e.g., by exchanging heat with another process stream) prior to filtration.
An example filtration module 24 is shown in
Referring now to
The substrate 36 of the porous filtration membrane may be an agglomeration of irregularly shaped metal particles or subunits 46 that are formed into a tube (e.g., particles with a diameter less than 100 μm). Channels between particles 46 allow the substrate 36 to be porous and allow permeate 15 to pass through the substrate 36. To coat the tubular substrate 36 with titanium dioxide, the substrate 36 may be contacted with a slurry of titanium dioxide and sintered (e.g., heated to at least 900° C.). In some embodiments, the porous filtration membrane 28 (e.g., the porous membrane tubes 32) is a microfilter and/or includes pores having an average diameter of from about 0.1 μm to about 10 μm. In other embodiments, the porous filtration membrane 28 is an ultrafiltration membrane (e.g., with pores having an average diameter of from about 0.01 μm to about 0.1 μm) or even a nanofiltration membrane (e.g., with pores having an average diameter of from about 0.001 μm to about 0.01 μm).
The tubes 32 of the module 24 may be disposed within a permeate shell (not shown). The tubes 32 may be in a single-pass arrangement or a multi-pass arrangement. In multi-pass systems, subsets of tubes 32 may be connected in series. The modules 24 may be operated at pressures from about 150 psi to about 3,000 psi.
In some embodiments, the filtration membrane is stable at relatively high pH ranges such as a pH of about 10.5, about 11, about 11.5 or even a pH of 12 or more. For example, in various embodiments, the membrane will maintain its rigidity and/or will exhibit little to no signs of degradation or corrosion for an extended period of time, when exposed to these pH ranges. The filtration membrane may be stable at temperatures of about 60° C. or more (e.g., 150° C., 200° C., 300° C. or 350° C. or more).
Commercially available embodiments of cross-flow filtration membranes include Scepter® filters, available from Graver Technologies (Glasgow, Del.).
A permeate 15 passes through the filtration membrane 28. The permeate 15 is depleted in one or more impurities (e.g., suspended solids, dissolved solids, larger compounds, etc.) relative to the effluent 8 introduced into the cross-flow filtration module 24.
In some embodiments of the present disclosure and as shown in
In some embodiments and as shown in
As shown in
The retentate 30 (i.e., concentrate) that does not pass through the filtration membrane retains at least a portion of the impurities in the effluent (i.e., is concentrated in one or more impurities). The retentate 30 may be further processed to remove additional water and/or to concentrate dissolved or suspended solid materials, such as by evaporation. Retentate 30 may be enriched in starch, non-starch polysaccharides, and proteins relative to the wastewater effluent 8 and may be formulated in animal feeds or other suitable uses.
In some embodiments, the wastewater effluent 8 is introduced into a plurality of modules 24, either in parallel or in series. In one example (e.g.,
In some embodiments, an antioxidant composition is recovered from the permeate 15 and/or retentate 30 produced from the cross-flow filtration module 24. As shown in
In the method of
Antioxidant compounds that may be recovered from the permeate 15 or retentate 30 include, but are not limited to, phenolic compounds, polyphenolics, ferulic acid, sinapinic acid, cinnamic acid, caffeic acid, chlorogenic acid, coumaric acid, vanillic acid, tocopherol, tocotrienols, anthocyanins, procyanidins, flavonoids, polyflavonols, tannins, and combinations thereof.
In some embodiments and as shown in
In other embodiments, absorption media is eliminated and the permeate 15 or retentate 30 is directly contacted with a solvent in the antioxidant recovery unit 33 to extract the antioxidant compounds. Suitable solvents include organic solvents such as ethyl acetate, ethyl lactate, isopropanol, ethanol, ether, pentanol, aliphatic alcohol, acetonitrile, hexane and combinations thereof. The permeate 15 or retentate 30 may be concentrated prior to solvent extraction such as by spray drying, freeze drying and/or evaporation.
In some embodiments, at least about 33% or more (e.g., 50%, 75%, 90%, 95% or more) of the antioxidant compounds introduced into the cross-flow filtration module 24 are recovered in the permeate 15 or retentate 30. Alternatively or in addition, the yield of antioxidants recovered from the wastewater effluent 8 may be about 0.1 grams of antioxidants per liter of wastewater effluent (e.g., 0.5 grams, 1 gram, or 1.5 grains or more of antioxidants per liter of wastewater effluent).
Referring now to
After storage and/or packaging, the antioxidant composition 40 may be processed for human and/or animal use (e.g., formulated in a food or drink, in a pharmaceutical, or in a cosmetic).
It should be noted that
Compared to conventional methods for producing a food product, the methods of the present disclosure have several advantages. For example, by using a cross-flow filtration membrane, fouling of the membrane may be reduced which increases the life of the membrane and reduces processing downtime. In embodiments in which at least a portion of the permeate is recycled such as by introduction in the alkaline cooking system or the dewatering system (e.g., for washing of cooked grain), the amount of process water input into the processing system may be reduced, the amount of alkaline (e.g., lime) used to hydrolyze the grain may be reduced (i.e., when recycling to the cooking system), and/or the heat in the recycled permeate may be recovered (e.g., by direct use of recycled permeate or by exchanging heat with other process streams). In embodiments in which a filtration membrane includes a stainless steel or nickel alloy substrate, the membrane is stable at the relatively high pH and relatively high temperature of the wastewater effluent. The stability of the membrane allows the wastewater effluent to be filtered without reducing the pH and/or temperature of the effluent. In embodiments in which an antioxidant composition (e.g., phenolics) is recovered from the permeate or retentate from the cross-flow filtration module, the antioxidant composition may be further processed for human or animal use which improves the economics of the food processing system.
The processes of the present disclosure are further illustrated by the following Examples. These Examples should not be viewed in a limiting sense.
Batch and continuous filtration operations were tested during separate trials. Batch operation was used to determine the estimated volume recovery feasible for wastewater. Continuous operation was tested to determine efficacy of the membrane filtration over time. The combination of recovery volumes paired with flux value over time were used to estimate the size needed for handling the flow rate of alkaline cook water discharged from a macerator for various recovery amounts and feed rates.
Alkaline cook water discharged through a macerator was sifted for large particles. The cook water (pH of 10.9-11.1) was processed through a cross-flow filtration module having a microfiltration membrane (benchtop model Scepter® filter from Graver Technologies (Glasgow, Del.)). The testing system (
The test fluid was macerator effluent separated from the grain. The initial feed was a pale yellow color and completely opaque, with a cooked corn odor. Some suspended solids settled in the feed quickly, leaving a turbid supernatant. The feed was agitated in to re-disperse any settle solids. Material was then pre-heated to 60° C. using low-pressure steam in an immersion coil with all condensate sent to drain.
After the feed was transferred to a test unit, the temperature was increased and maintained at approximately 74° C. through the use of low-pressure steam through the shell side of a heat exchanger. Shortly after introduction to the test unit, feed color changed to a slightly green hue. All permeates were golden brown and crystal clear. Final concentrate was similar to the initial feed, but much more viscous.
Permeate and retentate were recycled to the tank for 47 minutes allowing the membrane to achieve steady state flux. A pressure scan was performed by incrementally increasing trans-membrane pressure (IMP), while holding all other parameters constant. Membrane flux briefly increased with TMP, but then dropped back to the prior recorded level. Lack of a permanent flux increase at higher TMP demonstrates that the membrane was diffusion-limited at the lowest TMP tested. A concentration scan was performed by incrementally removing permeate while recycling concentrate and holding all other parameters constant.
The test was stopped because the unit reached minimum volume. Given additional feed, the test could have continued to higher volume recovery. The membrane flux over time is shown in
Alkaline cook water (pH of 10.7-11.2) discharged from a macerator was sifted for large particles and then processed through a cross-flow filtration module having a microfiltration membrane made of stainless steel coated with sintered titanium dioxide (Scepter® membrane). Continuous operation was performed to determine efficacy of the membrane filtration over time. The testing system (
The processed wastewater was macerator effluent with large particles such as corn kernels, large bran and germ being separated. Wastewater was circulated until steady state flux was achieved in the membrane. A target data point was taken to determine the membrane flux at the steady state prior to continuous operation.
For continuous operation, the permeate 15 and retentate 30 were directed to drain 50. Wastewater effluent 8 from the macerator was fed to tank 42. Every hour, the drain valves were closed and permeate/concentrate again recirculated back into the feed tank 42. After resting for 5 minutes on recirculation, another data point was collected to determine the flux. These data points are reported in Table 1, below.
Collected data indicated that 90% permeate recovery may be achieved with a membrane flux of 44.3 GFD. Reducing permeate recovery to 71.3% increased membrane flux to 70.1 GFD.
Antioxidants (phenolics) were recovered from masa wastewater by resin adsorption to demonstrate antioxidant recovery from the permeate or retentate discharged from a cross flow filtration module. The resins used for adsorption of phenolics were activated by contacting the resin (21 g) with ethanol (125 ml) in a beaker (250 ml) to cover the bed of resin by about 2.5-5 cm of ethanol. Alternatively, methanol could be used to activate the resin. The resin and ethanol were blended by shaking for 1 minute and the suspension was stirred at 175 rpm at 25° C. for 15 minutes. The beads (21 g) were filtered out of the mixture and were twice rinsed with deionized water (105 g) at a 5:1 mass ratio of deionized water to resin. The washed resins included about 65% water as determined by drying to constant weight (100° C. overnight).
Masa wastewater was adjusted from 12.4 pH to 4 pH by addition of 85% sulfuric acid. Hydrated activated resin was mixed with wastewater (3 g of resin to 25 ml wastewater or 21 g resin to 175 ml wastewater) in sealed Erlenmeyer flasks (25° C.). The mixture was mixed on an orbital shaker at 175 rpm for up to 3 hours. The beads of resin were filtered by a 0.45 μm membrane filter. The phenolic level in the masa wastewater was determined before and after contact with resin and indicated yields between 67-90%.
After adsorption, the resins were washed with distilled water to remove unadsorbed compounds that may reduce the purity of the extracts. The resin was washed twice with distilled water at a mass ratio of resin to water of 3:1. The mixture was mixed on an orbital shaker for 20 minutes at 25° C.
The washed resins (65% moisture) were contacted with an ethanol/water (88:12) solution (1 gram resin to 3 ml solution) at 25° C. to desorb extracts. Alternatively, acidified ethanol (0.5% w/w HCl 37%) may be used for desorption. The mixture was mixed for 2 hours on a rotary shaker at 180 rpm at 25° C. Resin was regenerated overnight in 1 M NaOH and was washed with deionized water.
The amount of antioxidants in the masa wastewater before extraction is shown in Table 2.
Several different resins were tested for antioxidant recovery with the amount of antioxidants in the desorbed solution and the recovery rate being shown in Table 3.
As shown in Table 3, each adsorbent recovered 80% or more of the antioxidants with Amberlite XAD-4 recovering 99.8% of the antioxidants.
As used herein, the terms “about,” “substantially,” “essentially” and “approximately” when used in conjunction with ranges of dimensions, concentrations, temperatures or other physical or chemical properties or characteristics is meant to cover variations that may exist in the upper and/or lower limits of the ranges of the properties or characteristics, including, for example, variations resulting from rounding, measurement methodology or other statistical variation.
When introducing elements of the present disclosure or the embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” “containing” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a particular orientation (e.g., “top”, “bottom”, “side”, etc.) is for convenience of description and does not require any particular orientation of the item described.
As various changes could be made in the above constructions and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawing[s] shall be interpreted as illustrative and not in a limiting sense.
This application claims the benefit of U.S. Provisional Patent Application No. 62/536,115, filed Jul. 24, 2017, which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2018/043270 | 7/23/2018 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62536115 | Jul 2017 | US |
