Patent Application
20220315671
The present invention relates to a crystalline starch nano-microparticle product, gels and procedures. More particularly, it refers to a nano-microparticle product comprising between 60% and 70% of crystalline nano-microparticles and between 40% and 30% of modified starch grains, wherein at least 90% of the nano-microparticles have sizes less than 200 nm and more than 40% of said nano-microparticles are less than 100 nm. The nano-microparticles can be mixed with boiling water, giving rise to gels that are useful in coating food, making creams and other uses.
In the food industry, attempts are being made to implement more natural products that are cheap and easy to assimilate by the consumer. In this sense, it is beginning with the use of products that are within the framework of nanotechnology.
Methods for preparing starch nanoparticles using enzymes and starch recrystallization are known (CN102964609).
Methods for preparing starch nanoparticles by acid hydrolysis are known, which lead to crystalline nanoparticles, with sizes between 15-40 nm (Le Corre D., Bras J., & Dufresne A. (2010) Starch Nanoparticles: A Review. Biomacromolecules, 11, 1139-1153). It has the disadvantage of low performance. Even under the optimal conditions to produce nanoparticles with acid hydrolysis, a yield of 14.69% is obtained (Park E. Y., Kim M., Cho M., Lee J. H. & Kim, J. (2016) Production of starch nanoparticles using normal maize starch via heat-moisture treatment under mildly acidic conditions and homogenization. Carbohydrate Polymers, 151, 274-282).
Homogenization and emulsion methods are known (Ding Y., Zheng, J., Zhang, F., & Kan, J. (2016), Synthesis and characterization of retrograded starch nanoparticles through homogenization and miniemulsion cross-linking. Carbohydrate Polymers, 151, 656-665 and Chin S F, Azman, A., & Pang, S C (2014). Size controlled synthesis of starch nanoparticles by a microemulsion method. Journal of Nanomaterials, 9, 1-7).
Reactive extrusion methods are known (Song, D., Thio, Y. S., & Deng, Y. (2011). Starch nanoparticle formation via reactive extrusion and related mechanism study. Carbohydrate Polymers, 85(1), 208-214).
Ultrasound methods are known. Ultrasound breaks the crystalline structure of starch, leading to nanoparticles with low crystallinity or an amorphous structure with sizes between 30 nm and 100 nm. (Kim H. Y., Park S. S. & Lim S. T., (2015) Preparation, characterization and utilization of starch nanoparticles. Colloids and Surfaces B: Biointerfaces, 126, 607-620 and Haaj, S. B., Magnin, A., Pétrier, C., & Boufi, S. (2013). Starch nanoparticles formation via high power ultrasonication. Carbohydrate Polymers, 92(2), 1625-1632).
A crystalline starch nano-microparticle product is provided comprising between 60% and 70% crystalline nano-microparticles and between 40% and 30% modified starch grains. Where at least 90% of the nano-microparticles have sizes less than 200 nm and more than 40% of said nano-microparticles are less than 100 nm.
A procedure is provided for obtaining a product of crystalline starch nano-microparticles, with a content of between 60% and 70% of crystalline nano-microparticles and around 40% and 30% of modified starch grains and wherein at least 90% of the nano-microparticles are smaller than 200 nm and more than 40% of these nano-microparticles are smaller than 100 nm. The procedure comprises the following steps: preparing an aqueous solution of starch:water at a ratio between 1:99 and 10:90 and stirring and then heat it to a temperature between 50° C. and 60° C. maintaining constant stirring. Subsequently, the solution is cooled to a temperature between 4° C. and 6° C., washed with distilled water and a wet paste is obtained that comprises a starch/water ratio of around 50/50 and is irradiated at a dose of between 20 kGy and 23 kGy; to finally freeze-dry said paste if necessary. In one embodiment the water for preparing the aqueous solution may be water at an acidic pH, for example a pH of 4.5.
A starch gel is provided that comprises between 1% and 20% of the product of the nano-microparticles and between 99% and 80% of water, depending on its subsequent use, for example for coating foods such as fruits or for the preparation of creams. The gel can be lyophilized for other uses, for example in the pharmaceutical industry.
In a preferred embodiment of the procedure of the present invention, gamma irradiation is carried out on a wet paste comprising a starch/water ratio of at least 50/50. This relationship generates a high yield of the final product.
The procedure of the invention makes it possible to obtain a product made up of nano-microparticles and treated starch grains (fragmented, with holes). A crystalline product is obtained.
In the procedure of the invention it is not necessary to carry out re-crystallization steps because a crystalline material is irradiated and another crystalline material is obtained. When carrying out a first stage of heating the product to a maximum temperature of 50° C., the product obtained is crystalline, directly irradiating a wet paste of crystalline starch, wherein part of the product is nano-microparticles and another part is grains of treated starch (fragmented, with holes).
Basically, the procedure consists of a low-temperature heat treatment of a mixture of starch and water, subsequent washing, removal of water either by decantation, centrifugation or filtration, and subsequent treatment of the obtained paste with gamma radiation at a dose between 15 kGy and 25 kGy. One of the advantages of the procedure consists in the high yield (at least 600 grams of product is obtained for every 1000 grams of starch; preferably at least 700 g).
Starch was transformed, by an irradiation process, into crystalline starch nano-microparticles with about 65% submicron size and about 35% micron size. From the point of view of the product that results from this process, it consists of a nano-microparticle/starch grain mixture modified in size, composition and structure with different characteristics from the product obtained by other techniques. A product is obtained wherein at least 90% of the nano-microparticles have sizes less than 200 nm and of these, more than 40% are less than 100 nm. This product has advantages over having only nanoparticles or one made by mixing nanoparticles with starch grains. These advantages are, for example, the ability to generate non-sticky gels with a consistency similar to jelly; and if these gels are lyophilized, they lead to a unique micro-nano-porous structure of ultralight solid material, capable of storing different active ingredients inside.
Evaluation of the amylose content resulting from the leftovers from each wash (without sorbate), prior to irradiation: the results are shown in
The 2% iodine solution consists of polyiodide ions of the In− type and has a yellowish-brown color. In the presence of starch, iodine is introduced into the helical chain conformations of amylose, leading to the formation of an iodine-amylose complex. This complex absorbs light at a different wavelength than the In− ions, displaying a dark blue color. The intensity of the blue color decreases with the decrease in the number of complexes formed.
As can be seen in
A quantitative analysis was performed to find out the contents of amylose after each wash, by colorimetric determination, using UV-Visible spectroscopy. The results are shown in
It should be noted that the results of the supernatants in the different kinds of pastes (with or without potassium sorbate) did not show significant changes; showed that the addition of about 0.2% by weight of this antimicrobial agent did not modify the structure or the crystallinity of the nano-microparticles.
Observations by Optical Microscopy with polarized light:
Evaluation of the morphology of the nano-microparticles:
On the other hand, it can be seen that the nanometric-sized particles were associated forming a grape-like structure (systems without K-sorb:
Determination of particle size from the SEM micrographs: the histogram representing the size distribution of the nano-microparticles obtained by gamma radiation was made from the calculation of the particle diameter taken from the SEM images (
From the image analysis it was possible to determine that a material composed of at least 65% of submicron particles and around 35% of starch grains modified by the irradiation process was obtained. In addition, at least 90% of the submicron particles were smaller than 200 nm, of which more than 45% were smaller than 100 nm (nanoparticles).
Determination of particle size from DLS (Dynamic Light Scattering) studies: FIG. 8 shows the results of the DLS tests for the particles. It can be seen that the distribution does not change significantly with respect to the histograms shown in
Evaluation of the crystallinity of the nano-microparticles: in order to analyze the crystallinity of the materials obtained by gamma radiation (with and without K-sorb), X-ray diffraction tests were performed and compared with the pattern obtained for native starch (see
No effects were observed with the addition of sorbate,
Evaluation of the thermal properties of the nano-microparticles:
Gels and Gelified and Lyophilized Products:
With nano-microparticles, gels can be generated in a simple way. Said gels can be applied by means of different techniques on food products for their preservation.
In addition, gelled products can be generated from the immersion of between 1% and 20% of nano-microparticles in boiling water, such that, immediately upon reaching room temperature, a gel is generated that is in a viscous state with movement (it can flow) (
On the other hand, in the food industry it can replace the applications of starch as a thickener, with the advantage that at least 65%, being submicron in size, can be more easily digested.
The incorporation of essential oils in a starch gel and in the gel of starch nano-microparticles has been tested. Fragrance retention of limonene essential oil was determined both in the gel formed by the nano-microparticles, and in a native cassava starch gel, by means of GC-MS (gas chromatograph with a mass selector) studies. Measurements were made after 1 month by opening the vials containing the gels twice a day, every day, and leaving them open for 5 minutes. The sample made with starch after 4 days of study did not measure a fragrance peak related to the essential oil, while the nano-microparticle gel maintained its 75% fragrance.
Products whose photographic images are shown in
In the pharmaceutical, cosmetic and agronomic industries, the product can be used since prior gelation and lyophilization of the same, leads to highly porous, ultralight and natural structures that can contain antibiotics, vitamins, antioxidants, fertilizers or the additive that one wishes, controlling the release. In addition, thanks to its highly porous structure, the product could replace styrofoam or the material traditionally used in packaging, with the additional advantage that this material is biodegradable and would not lead to polluting waste.
In the packaging industry, it could replace starch-containing containers with the additional advantages of its high crystallinity.
This process could be extended to any polysaccharide from gamma radiation cleavage of the O-glycosidic bond.
The product can be colored with pigments and/or natural inks. In addition, it can be derivatized or modified with different substances intended for a particular use thanks to the high density of hydroxyl groups that the material presents on the surface. This same effect makes the material a powerful water absorber, for which it could be used to replace previously known moisture absorbers.
It is a product considered by European legislation as natural nanoparticles. The material is non-toxic, edible, non-irritable. This is because the body is used to processing starch and as part of this process it breaks down into nanoparticles. In addition, in the case of using cassava starch as the starting starch, the product would be suitable for coeliacs. Nanoparticle legislation considers as such a particle with a size less than or equal to 100 nm.
The density of the pieces has been determined by measuring their geometry and weight. From statistics of more than 10 samples, the density of the irradiated and lyophilized gel was determined to be 0.17 g/cm3±0.02 g/cm3. This invention is better illustrated according to the following examples, which should not be interpreted as a limitation imposed on the scope thereof. On the contrary, it should be clearly understood that other embodiments, modifications and equivalents thereof may be resorted to, which after reading this description, may suggest to those skilled in the art without departing from the spirit of the present invention and/or scope of the attached claims.
Two procedures were carried out: with and without potassium sorbate (K-sorb). An aqueous starch solution was prepared consisting of a mixture of 100 grams of starch and 1900 grams of distilled water, so as to have a ratio of 5:95 (starch:water). Other ratios were carried out, for example 10:90 to 1:99. The distilled water was previously acidified to bring it to pH=4.5.
The aqueous solution was stirred using a magnetic stirrer at various constant speeds between 100 rpm and 300 rpm for about 45 minutes. Heating was then started from room temperature to 50° C., maintaining constant stirring, and using heating ramps of around 1° C./min. Then, it was left stirring at the same speed and at 50° C. for around 10 minutes. In this stage, the amylose proceeds to detach from the starch, solubilizing in the water.
Immediately afterwards, the container with the solution that was at 50° C. was placed in an ice bath to cut the heating inertia and prevent the temperature from continuing to rise, and then it was stored in a refrigerator (6° C.) for about 24 hours. hours. At that stage, phase separation occurred due to decantation of the starch. Subsequently, the supernatant was discarded and the resulting paste was washed 4 times with distilled water, in order to remove the amylose that had detached from the starch grain and that had been solubilized in the water. After each wash, an aliquot of the supernatant (10 ml) was separated to qualitatively check the removal of amylose during the heat treatment, and verify that it had been completely removed by the fourth wash.
The hydrated paste was divided and collected in Ziploc bags and kept at −16° C., until irradiated.
Potassium Sorbate Procedure:
A procedure was carried out as mentioned in the previous paragraphs but potassium sorbate (K-sorb) was added. The final concentration of K-sorb was around 0.2% by weight, much lower than the limit allowed for its use in foods by the FDA (which is 0.3% by weight).
The irradiation of the wet pastes, which comprised an approximate ratio of 50/50 starch/water, was carried out at the Semi-Industrial Irradiation Plant (Pisi) belonging to the Ezeiza Atomic Center, Atomic Energy Commission. For this, a minimum dose of 20 KGy and a maximum dose of 23 KGy were used, with a rate of (14±1) KGy/h, according to the data reported by the company. After this process, the pastes were freeze-dried for 24 hours.
The yield of the procedure was about 74%.
To do this, aliquots of the supernatants were taken and complexed with a 2% iodine solution (amylose-water-2% iodine) to generate an iodine-amylose complex. Each solution was photographed.
100 mg of paste was weighed and 1 ml of 95% ethanol and 9 ml of 1 N NaOH were added. The system was left at room temperature for 18-24 hours. The content was transferred by washing to a 100 ml volumetric flask. Next, a 5:100 dilution of the previous system was made, adding 1 ml of 1 N acetic acid and 2 ml of 2% iodine stock solution. It was shaken and allowed to stand for 20 minutes.
The nano-microparticle gel of the invention was allowed to cool at room temperature on the counter until it reached 25° C. The application of the gel at room temperature was carried out using two techniques: immersion or spray. For both cases, the food product was previously washed and dried at room temperature and controlled humidity (RH ˜56.7%).
In the case of immersion, the food was immersed in the gel for 5 to 15 seconds depending on the roughness of the product to be coated. The longest time was used in those foods whose shape was more irregular and that required a uniform and thick coverage. After removing the food, the excess gel was allowed to drain.
In the case of the spray, the gel was placed in a sprayer and sprayed on the products until completely covering their surface.
The release experiment of different components was carried out. In particular, it was evaluated using limonene essential oil, a commercial fertilizer (with nitrogen, potassium and phosphorus), and a commercial antibiotic (gentamicin). In all cases, the tests were carried out at room temperature on 10 samples. The desired component was injected into the gelled and lyophilized material of
In the case of limonene essential oil, it was observed that the product immediately releases a significant amount of essential oil, with the release after 15 min of exposure being between 30% and 40%, and after 48 hours of study, greater than 50%.
In the case of the commercial fertilizer, the gelled and lyophilized material released between 25% and 45% at 15 min, and after 48 hours of study, the release was greater than 65%.
In the case of the antibiotic, the tests were carried out in different aqueous media, distilled water (pH=6.4) and acidified medium (pH=3.5), in order to simulate the pH of the stomach.
The nano-microparticle gel films can be obtained by dehydration at room temperature and pressure (0.1 MPa and 25° C.) inside a hood. The dehydration procedure can also be carried out in a desiccator with a drying agent, such as silica gel, calcined anhydrous calcium sulfate, anhydrous copper sulfate or anhydrous magnesium sulfate, at room temperature (25° C.). A vacuum can be applied to the desiccator with a vacuum pump (for example of the order of 40 kPa or less) thereby speeding up the dehydration time, reducing it significantly depending on the physicochemical conditions that are set.
From the nano-microparticle gel of the invention, with and without K-sorb, films can also be prepared by dehydration on a heating plate under pressure. To this end, nano-microparticle gel is poured into a heated press container that can increase its temperature from 50 to 150° C., which allows the gel to dehydrate. Once a consistent texture of the gel is achieved, a pressure of the order of 3.2 to 3.8 Pa is applied to the film being formed to level its thickness until it is consistent and homogeneous. The film is then cooled to room temperature (25° C.).
Once the gel adopts the consistency of a firm and homogeneous film, it is demolded. The thickness of the film will depend on the conditions imposed to obtain it, wherein said thickness is between 0.5 and 2 mm.
| Number | Date | Country | |
|---|---|---|---|
| 63171439 | Apr 2021 | US |
