BACKGROUND OF THE DISCLOSURE

The present disclosure relates generally to the formation of low-crystallinity phytosterol nanoparticles via cooling-controlled supercritical carbon dioxide (SC—CO2) impregnation into biodegradable nanoporous wheat starch aerogels and methods of preparing these aerogels. Particularly, it has been found that these aerogels and method of impregnation of the aerogels increase the water dissolution and release properties of the phytosterols in the simulated gastric and intestinal fluids, thereby making them available for preparation of high nutraceutical value foods.

In recent years, the concern among food consumers is not simply building blocks and calories, but nutrition for improved health and wellness. The increased prevalence of diet-related illnesses (e.g., obesity, cardiovascular disease, and cancer) and the emerging trend of “green” consumerism have negatively impacted the acceptability of foods containing artificial ingredients. As a result, food industry prioritized the development of foods and beverages using bioactives, e.g. phytosterols, carotenoids, tocopherols, and omega-3 oils, and this has led the food industry to focus on “technology-driven” food products. This means industry and scientists are not just looking for high stability foods, energy food, pre-prepared food, but rather foods enriched with bioactives using various delivery methods to improve the bioavailability and bioefficacy of the bioactives.

Numerous studies have shown the positive health effects of bioactives to maintain health and wellness and also to prevent and cure many diseases. Among lipophilic bioactives, phytosterols has been receiving increasing attention due to growing interest in dietary treatment of hypercholesterolemia. Consequently, there is a growing interest in preparing functional food and nutraceutical products containing phytosterols. Phytosterols, which are chemical homologs of cholesterols, mainly include β-sitosterol, campesterol and stigmasterol. Phytosterols are well-known for their role in reducing the risk of cardiovascular disease by decreasing the serum total and low-density lipoprotein (LDL) cholesterol concentrations in humans. They are further known for managing inflammatory bowel disease (IBD). Recent research has suggested that phytosterols may have other biological activities such as anti-inflammatory, anticancer, and antioxidative effects in addition to cholesterol lowering activity. Nevertheless, the amount of phytosterols taken in the typical Western diet is only 150-400 mg/day. For efficient utilization of phytosterols for their positive health benefits, their content in the diet must be increased. American Heart Association Nutrition Committee suggested consumption of 2 g of phytosterols per day to manage hypercholesterolemia.

Absorption of phytosterols in the body is much smaller compared to cholesterol. During digestion, cholesterol is first incorporated into the dietary mixed micelles for absorption in the intestine. Phytosterols are relatively more hydrophobic than cholesterol and are in dynamic competition with cholesterol for incorporation into dietary mixed micelles, displacing cholesterol and leading to its excretion. Phytosterols are not synthesized in the human body and therefore have to be taken in the diet containing phytosterols such as vegetable oils, nuts, and cereal grains. While there has been a growing trend in the food industry to enrich foods with phytosterols with the growing market demand, food quality can be negatively affected by phytosterols as phytosterols are high melting point crystalline powders, which are not soluble in water and poorly soluble in fats and oils. Thus, conventional phytosterol use has low efficacy, and the crystallization of phytosterols in an oil phase affects food sensory and quality negatively.

Commercially, natural phytosterol mixtures are isolated from vegetable oil deodorizer distillates or tall oil to be used as supplemental sources of phytosterols. However, earlier studies have shown that natural phytosterol mixtures were not very effective in reducing cholesterol as much larger doses were needed. Further, because of the poor solubility and crystallinity of the phytosterols, their inclusion into the micellar phase is limited. Additionally, incorporation of phytosterols into foods is a major challenge from a technological and food quality standpoint because phytosterols are high melting point crystalline powders that are insoluble in water and poorly soluble in fats and oils. When used in this form, the efficacy of the phytosterols is very low, and also crystallization of phytosterols in the oil phase leads to a gritty texture, compromising sensory quality and consumer acceptance.

Based on the foregoing, low water solubility is an important parameter limiting the enrichment of the foods with water-insoluble bioactives. Moreover, water solubility is a key parameter determining the bioavailability of the bioactives. Said a different way, low water solubility limits the health benefits of the bioactives in the food products, and hinders their health benefits due to poor bioavailability caused by poor water solubility. Therefore, improving the bioavailability of bioactive food compounds is essential to improving their bioefficacy. Bioavailability of the lipophilic bioactives also depends on their physical properties such as morphology and crystallinity. Crystalline forms of bioactives are typically less bioavailable than their amorphous or soluble forms. The effect of the crystal structure on the bioavailability was observed for phytosterols. Very low bioavailability of the phytosterols is due to its insoluble crystalline structure.

At present, the main approach to add phytosterols into foods is to esterify the phytosterols with fatty acids to obtain liquid or semi-liquid esters, similar to fats and oils, which can be incorporated into high-fat products like margarines and spreads. However, enrichment of low-fat products is still a challenge. When the big number of low-fat products and the demand for low-fat products are considered, there is a critical need to find solutions to incorporate free phytosterols into foods, including low-fat foods. In order to make the inclusion of the free phytosterols in the foods, it is desirable to have small phytosterol crystals with less crystallinity that can be easily dispersed in water. Emulsion formation, liposomes, and micronization are among the different approaches used to develop delivery forms for phytosterols. Micronization increases the surface-to-volume ratio by decreasing the particle size, leading to increased solubilization and thus increased bioavailability. Microemulsions are suitable only for water-based food formulations, and they require large amounts of surfactants which result in off-flavor formation. They are also sensitive to environmental conditions such as temperature, pH, and dilution. Nanoemulsions are similar in structure to microemulsion, but they are thermodynamically unstable colloidal dispersions and break down over time through a variety of destabilization mechanisms, such as flocculation, coalescence, gravitational separation, and Ostwald ripening. Liposomes are formed of one or more concentric shells of surfactant bilayer. Solvent evaporation method uses organic solvents for liposome production, but clean production is possible with other methods such as extrusion methods. However, short shelf life and low stability are the major problems limiting the use of liposomes in suspension. Therefore, they need to be dried to improve the stability. Another issue is that only few of those systems can be used in the food industry because the materials used to construct the delivery system is not food grade. For a successful commercialization of the delivery system in food industry, the delivery system must be fabricated from food grade ingredients and, possibly, inexpensive ingredients.

SC—CO2technology has been used as a “green” method for the isolation of phytosterols from various sources, especially fractionation of deodorizers' distillates of vegetable oils. However, the use of supercritical fluid technologies for phytosterol particle engineering is very new. A modified rapid expansion of supercritical solutions (RESS) method was used to form composite L-poly(lactic acid)-phytosterol particles. Another application of supercritical fluid technology for particle formation is DELOS (depressurization of an expanded liquid organic solution). In the DELOS process, the solute is first dissolved in a conventional organic solvent, and CO2is added to expand the liquid solution at high pressure, and finally the expanded solution is depressurized to form micron size particles. Recently, the DELOS process was used for micronization of phytosterols. However, even though that method generated micron size phytosterols, obtained phytosterol particles had higher crystallinity than the native phytosterol. Moreover, those studies have not demonstrated the improvement of the bioavailability of the generated phytosterol products.

In the present disclosure, a simple and clean approach to decrease the size and crystallinity of the phytosterols in order to improve their bioaccessibility, and in turn bioavailability, is disclosed. This approach uses nanoporous food grade starch as a nanoporous and high surface area mold and SC—CO2to impregnate the phytosterols into the nanopores and to form colloidal phytosterols with decreased crystallinity.

BRIEF DESCRIPTION OF THE DISCLOSURE

The present disclosure is generally related to nanoporous starch aerogels impregnated with a bioactive. Particularly, low-crystallinity phytosterol nanoparticles are formed using nanoporous starch aerogels via a cooling-controlled SC—CO2impregnation process. Developing nanoporous starch aerogels impregnated with lipophilic bioactives such as phytosterols will improve the health benefits of the water-insoluble bioactives, will make the addition of crystalline lipophilic bioactives into foods and beverages to produce health and wellness improving foods in a clean and simple way, and maximize the utilization of the bioactives.

Accordingly, in one aspect, the present disclosure is directed to a nanoporous starch aerogel impregnated with a bioactive.

In another aspect, the present disclosure is directed to a method of forming a starch aerogel impregnated with a bioactive, the method comprising: forming a nanoporous starch aerogel; and cooling-controlled impregnating of a supercritical carbon dioxide (SC—CO2)-bioactive solvato-complex into the nanoporous starch aerogel. In some embodiments, the forming of the nanoporous starch aerogel comprises: forming a starch hydrogel; exchanging water in the starch hydrogel with ethanol to form an alcogel; and SC—CO2drying the alcogel to form the nanoporous starch aerogel. In some embodiments, the nanoporous starch aerogel can further be ground for use in powder form.

