# Magnetic Properties of Commercial Cornflakes
## 2 Materials and Methods  
### Extraction of Iron  
Four packages, each containing 275 g of the most popular brand of cornflakes in Mexico, were bought from different supermarkets to extract as much iron as possible for subsequent physicochemical characterization. The ingredients published on the package are sugar, malt extract, iodized salt, calcium carbonate, ascorbic acid, maltodextrin, iron (11.7 mg/100 g), niacinamide, \(\alpha\)-tocopherol acetate, zinc oxide, retinyl palmitate, cobalamin, pyridoxine hydrochloride, thiamine mononitrate, riboflavin, folic acid, vitamin C, vitamin A, and BHT antioxidant. Additionally, the absence of artificial colorants is highlighted. After reading this nutritional information, the question arises about the kind of iron mentioned and whether any magnetic colorant is included. The iron was extracted under aseptic conditions using a method similar to that described by [PERSON] et al. [17]. In total, 1 kg of cornflakes was manually ground with a mortar, and the resulting fine powder was mixed with pure Milli-Q water and homogenized to a soft paste. This paste was transferred separately into five clean nylon bags, and in each bag, the paste was spread out to form a thin layer. Then, neodymium magnets were passed over the bags, whereby the attracted iron attached to their inner walls became visible as small, dark, and wet pellets, which were gently dragged and deposited into Eppendorftubes. The procedure was repeated until no more iron remained. Finally, all the collected iron was dried at room temperature for 12 h without a controlled atmosphere. At the end of the extraction process, surprisingly, the initially black iron filings changed to a red-brown color (RBIFs). In total, \(\approx\)70 mg of RBIFs were collected. But this color change of iron was not reported in [17]; therefore, we conclude that this extraction procedure alters the initial type of iron content in the cornflakes. Because of the unexpected color change observed in the last step of the previous method, a second extraction method was used to obtain the iron filings. Five packages with 0.275 kg (of the same cornflakes brand) were ground using a domestic electrical grinder at maximum grinding power (350 W) for 30 s. In total, 1.275 kg of powdered cereal was then sifted and transferred into six clean nylon bags, where it was spread out to form thin layers. As in the first method, neodymium magnets were passed over the bags, and the attracted gray iron filings on the inner face of each bag were collected into 50 mL polypropylene tubes. This step was repeated until no more iron remained. In contrast to the first method, these iron filings did not change their color over time, which is more consistent with the findings reported in [17]. The next step was to remove the organic material adhered to the iron using a method that involved a N\({}_{2}\) atmosphere. Then, the iron filings were deposited into an Erlenmeyer flask, mixed with 250 mL of ultra-purified water (previously bubbled with N\({}_{2}\) gas), and agitation at 200 rev/min was applied for 5 min. The iron filings were decanted using a magnet to remove the supernatant, which was then replaced with 200 mL of fresh water; immediately, agitation was applied again for 10 min. Two additional series of agitation and washings were performed, resulting in clear water that appeared to be free of organic residues. After that, the flask was subjected to sonication for 1 h, maintaining the inert atmosphere throughout. Later, the iron filings were decanted and washed twice. The resultant dark powder was then transferred and dried on absorbent paper while a direct saturant flux of N\({}_{2}\) was ventilated. Finally, the dried powder was deposited into two sealed bags using a magnet. Using this second extraction procedure, only \(\approx\)110 mg of dark iron filings (DIFs, brand 1) from the first brand of cornflakes were obtained.