A team from the Particle Technology Laboratory (LTP) of the Technological Research Institute (IPT) has developed iron sulfate (FeSO4) microcapsules that enable this compound to be used in fortifying food. Added to reconstituted powdered milk, they increased the rate of absorption by the body by a factor of more than four compared with milk with added unencapsulated FeSO4: the amount leapt from 2% or 3% to 13%. Iron deficiency affects a third of the population worldwide and, although FeSO4 is one of the compounds most widely used as a food additive, it lacked an efficient form of encapsulation. The technique developed at the IPT has already aroused the interest of companies.
Microencapsulation avoids common problems in these processes, such as a high degree of reaction of the mineral compounds with other ingredients, oxidation, as well as color variations and changes to the taste of the food. In this case, says the chemical engineer Maria Inês Ré, head of the LTP and coordinator of the project, “microencapsulation can mask the taste of the minerals in the products with additives, reduce the reaction with other ingredients and control their release in the specific part where they are better absorbed in the gastrointestinal tract”. Besides food, the uses include herbicides, adding enzymes to soap or detergent powder and printed perfume ads, where on scratching the paper, the fragrance can be smelt.
Maria Inês decided to work on iron supplements, because she saw a bottleneck. “Specialists know about iron deficiency in people and the need to supplement diets, but they do not have many technological options. It is no use including iron in the diet if it reacts with the other components of the food. After the reaction with other minerals, proteins or fats, in the journey to the intestine, the iron arrives already oxidized or precipitated or in poor state of usefulness (bioavailabilty)”. Maria Inês was joined in the work by the master’s degree student at the Pharmaceutical Sciences School of the University of São Paulo (USP), Tatiana de Oliveira Santos, who undertook complete studies of in vitro digestion – seeking to reproduce the complexity of the human organism.
The tests were carried out with microcapsules added to water and, then, toa complex culture – reconstituted powdered milk Maria Inês, who did her postdoctorate in Particle Technology at Toulouse in France, says that the project paves the way for exports; today microencapsulation is little known in this country and products are generally imported.For this reason, her great motivation was to develop the technology. “Existing techniques are in the private sector domain, and companies are not interested in swapping and absorbing information between distinct groups, such as between the perfumery, foods and pharmaceutical industries, because it is under patent”.
Stable and protected
Microcapsules are spherical, the best shape for draining and fluidity. In a solid culture, such as powdered milk, they are mixed into the product and they flow with it. The encapsulating material, natural or synthetic, protects the contents. In the pharmaceutical industry, the stability of the drugs increases and gives them “intelligent” properties, such as their controlled release in the human organism.
Iron sulfate was also was also chosen because of its high bioavailability if taken correctly to the place of absorption. In addition, it is a cheap compound and made in Brazil. These advantages make it easy to use microcapsules in food supplement programs. In an article on the bioavailabilty of minerals, in the Nutrition Magazine published in December 1997 by the Pontifical Catholic University of Campinas (Puccamp), Silvia Franciscato Cozzolino, of the Experimental Foods and Nutrition Department of USP Pharmaceutical Faculty, showed a study on the average daily ingestion of certain minerals in Brazilian diets, analyzed by region, age group, and social position. The lowest amounts of iron ingested were in the diets of the elderly in nursery homes in São Paulo, with 5.4 milligrams a day (mg/day), and in the diet of a low-income group in Santa Catarina, with 6.4 mg/day. The ideal for an adult is daily consumption of 15 mg/day.
The best product Maria Inês has developed, with bioavailability of 13%, was a microcapsule formulated with FeSO4 and an aqueous solution of NACMC (sodium carboxymethylcellulose, a derivative of cellulose). This liquid is placed in a special dryer where it is atomized and forms drops that evaporate and turn into microcapsules, imprisoning the iron sulfate in a membrane of carboxymethylcellulose. In the intestine, in contact with the alkaline aqueous solution, the membrane slowly turns into a gel. As the aqueous solution continues to penetrate, it dissolves the iron sulfate. “The release is at a controlled rate”.
In the beginning, around ten encapsulating agents were chosen. But most were rejected because they reacted poorly with the iron sulfate. Sodium carboxymethylcellulose and an association of it with a derivative of poly-acrylic acid used in the pharmaceutical industry, Eudragit RS 100, which did not work, were approved for microencapsulation.
Aqueous polymeric dispersions were also tested. They involved a technique that avoids organic solvents when the encapsulating agent is not water-soluble and, thus, ensures that there are no toxic residues in the product. These dispersions are used on macroscopic surfaces, such as tablets or pastilles. Maria Inês saw that, although the results for micro-particles were still not what was hoped for, it is possible to improve the process and optimize this type of covering.
The project enabled other studies to be undertaken at the same time with encapsulated products with innovative features that could be patented. Another possibility following patenting, which still requires time to be spent on research, is the iron sulfate microcapsule itself. The researcher believes that, after optimizing a product that is already good by introducing an additive to the encapsulating agent, a more precise modulation of the rate at which the iron is released into the body can be achieved. She wants to increase the iron absorption rate to 15%, which means shifting from a medium-high to a high usage rate.
In a new project, recently approved by FAPESP, Maria Inês intends to perfect the iron sulfate microcapsule, analyze the aqueous polymeric dispersions better, and also investigate all the mechanisms involved in the formation of the microcapsule that take place in the spray dryer. “The possible gain is very great. By mastering the technique and with more extensive knowledge of everything that might interfere in the process of producing the microcapsules, we will be able to achieve the ideal design for the product”.
Microencapsulation Study of Mineral (iron) by Spray Drying (nº 98/00533-7); Type Normal research assistance line; Coordinator Maria Inês Ré – Institute of Technological Research; Investment R$ 31,163.79 and US$ 45,925.16