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.
Chemical inactivation of aflatoxin B1 (AFB1) and aflatoxin B2 (AFB2) in maize grain by means of 1N aqueous citric acid was confirmed by the AFLATEST immunoaffinity column method, high performance liquid chromatography (HPLC), and the Ames test (Salmonella-microsomal screening system). The AFLATEST assay showed that aflatoxins in the maize grain with an initial concentration of 29 ng/g were completely degraded and 96.7% degradation occurred in maize contaminated with 93 ng/g when treated with the aqueous citric acid. Aflatoxin fluorescence strength of acidified samples was much weaker than untreated samples as observed in HPLC chromatograms. On the other hand, the Ames test results indicated that the mutagenic activity of acidified samples was greatly reduced compared with that of untreated samples based on his- --> his+ reversions in the Salmonella TA100 strain. Chemical inactivation appears to be a promising method of removing aflatoxin from food commodities.
Aflatoxin B1/chemistry , Aflatoxins/chemistry , Citric Acid/pharmacology , Food Contamination/prevention & control , Mutagens/chemistry , Zea mays/chemistry , Aflatoxin B1/toxicity , Aflatoxins/toxicity , Animals , Chromatography, High Pressure Liquid/methods , Consumer Product Safety , Humans , Immunoassay/methods , Mutagenicity Tests , Rats , Rats, Sprague-Dawley , Safety , Salmonella typhimurium/drug effects , Salmonella typhimurium/genetics , Treatment Outcome
To determine whether pozol, a nixtamalized maize-based food was contaminated with aflatoxins, samples of non-fermented pozol were collected during the period November 2002 to April 2003 from local markets at Comitan in Chiapas, Mexico. The samples were analyzed for the presence of aflatoxins. Nineteen out of one hundred and eleven samples were contaminated with aflatoxin B2 (AFB2) and traces of aflatoxin B1 (AFB1). The percentage of samples contaminated with AFB2 in pozol prepared with white maize was 5.4%. Pozol mixed with toasted cacao paste had a contamination rate of 41.5%. No aflatoxins were detected in pozol prepared with yellow maize. It was found that only 1 of 19 contaminated samples had aflatoxin concentrations above 20 ppb.
Aflatoxins/analysis , Food Contamination/analysis , Zea mays/chemistry , Aflatoxin B1/analysis , Aflatoxin B1/toxicity , Aflatoxins/toxicity , Consumer Product Safety , Food Microbiology , Zea mays/metabolism
The corn tortilla is elaborated using corn grain masa processed by the traditional nixtamalization method, which consists of two steps: cooking and steeping. In these steps the physicochemical and structural properties are strongly affected, resulting in changes in the textural characteristics of the tortilla produced. In this work the effects of cooking and steeping time on the moisture content, amylographic profiles, crystallinity, weigh loss from masa to tortilla, starch damage, rollability, elasticity and cutting force for grain, masa and corn tortillas, were evaluated. The milling of the nixtamalized grain and the cooking of tortilla conditions were the same in all treatments. All tortillas samples showed a good rollability. The results show that the moisture content of corn grain was increased up to 42 g/100 g during the total cooking time (45 min), and it further increased to 52-53 g/100 g after when the cooked grain was steeped for 4 h. All evaluated parameters showed high correlation coefficients with the texture properties of tortillas. The starch damage was the variable with the best correlation among all evaluated parameters. The correlation coefficients between starch damage and moisture content, weigh loss and maximum viscosity for corn grain, masa and tortillas were larger than 0.92 (p < 0.01). The best tortillas were produced using nixtamal with the follow characteristics: moisture content of nixtamal, 42-44 g/100 g and tortilla, 43-44 g/100 g; adhesiveness of masa, 30-50 g; maximum viscosity of nixtamal, 860-880 cp and tortilla 490-510 cp; starch damage of nixtamal, 14 g/100 g and tortilla, 35-37 g/100 g, and weigh loss of tortilla during cooking, 16 g/100 g.
Flour/analysis , Food Handling , Food Technology , Hot Temperature , Zea mays/chemistry , Food Preservation , Quality Control , Rheology
