RESUMEN
Nixtamalized maize tortilla is a basic food for the Mexican population. It has high energy due to high starch, which may be modified to decrease its bioavailability and to produce changes in the characteristics of flours. For this research, nixtamalized maize flour was prepared and subjected to an acetylation chemical process, with and without prior hydrolysis. Raw maize flour, traditionally nixtamalized maize flour, acetylated-nixtamalized maize flour (AF) and acetylated-hydrolyzed nixtamalized maize flour (AHF) were prepared and evaluated. These flours were used for dough and tortilla preparation and analyzed for degree of substitution (DS), physicochemical properties, structure, thermal, rheological, morphological and texture properties. FTIR spectra and DS showed the presence of acetyl groups. AHF showed the highest value for water absorption index. The resistant starch increased 0.27 and 0.42% for AF and AHF samples. The gelatinization enthalpy (∆Hg) for AF was greater than other flours. AF tortillas showed better characteristics than the traditional ones and their consumption was recommended since showed better RS.
RESUMEN
UNLABELLED: Starch isolated from macho banana was oxidized by using 2.5% and 3.5% (w/w) of sodium hypochlorite. Native and oxidized starches with glycerol were processed using a conical twin screw extruder to obtain thermoplastic laminates or sheets, which were partially characterized. Oxidized banana starches presented higher moisture and total starch but lower ash, protein, lipids, and apparent amylose content than the native starch. Micrographs of sheets from oxidized starches showed wrinkles and cavities presumably caused by the plasticizer, but with less free glycerol and unplasticized starch granules than those from native starch. Sheets from oxidized starch showed a notorious increase in all thermal parameters (To, Tp, and ΔH), mechanical properties (tensile strength, elongation at break, and elasticity), and solubility. Banana starch X-ray diffraction patterns corresponded to a mixture of the A- and B-type polymorphs, with apparently slightly higher crystallinity in oxidized specimens than in native starch. A similar trend was observed in the corresponding sheets. PRACTICAL APPLICATION: Due to the pollution problem caused by the conventional plastics, there has been a renewed interest in biodegradable sheets, because they may have the potential to replace conventional packaging materials. Banana starch might be an interesting raw material to be used as edible sheet, coating or in food packaging, and preservation, because it is biodegradable, cheap, innocuous, and abundant.