Liz Oliveira dos Santos

Homogeneity study of a corn flour laboratory reference material candidate for inorganic analysis.

In this work, a homogeneity study of a corn flour reference material candidate for inorganic analysis is presented. Seven kilograms of corn flour were used to prepare the material, which was distributed among 100 bottles. The elements Ca, K, Mg, P, Zn, Cu, Fe, Mn and Mo were quantified by inductively coupled plasma optical emission spectrometry (ICP OES) after acid digestion procedure. The method accuracy was confirmed by analyzing the rice flour certified reference material, NIST 1568a. All results were evaluated by analysis of variance (ANOVA) and principal component analysis (PCA). In the study, a sample mass of 400mg was established as the minimum mass required for analysis, according to the PCA. The between-bottle test was performed by analyzing 9 bottles of the material. Subsamples of a single bottle were analyzed for the within-bottle test. No significant differences were observed for the results obtained through the application of both statistical methods. This fact demonstrates that the material is homogeneous for use as a laboratory reference material.

Mineral and centesimal composition evaluation of conventional and organic cultivars sweet potato ( Ipomoea batatas (L.) Lam) using chemometric tools

Sweet potato is a food consumed in the world. In this work, the minerals and centesimal composition in sweet potatoes of organic and conventional cultivars was investigated. The accuracy was confirmed with a certified reference material of apple leaves (NIST 1515). The quantification of the samples was performed by inductively coupled plasma optical emission spectrometry and the digestion efficiency was evaluated by residual carbon content. The mean concentrations (in mg/100 g) of minerals were: 23.5 and 40.7 (Ca); 0.082 and 0.159 (Cu); 0.303 and 0.481 (Fe); 197 and 381 (K); 166 and 35.7 (Mg); 0.183 and 1.15 (Mn); 68.6 and 0.433 (Na); 54.1 and 62.2 (P) and 0.197 and 0.261 (Zn) for conventional and organic cultivars, respectively. Average centesimal concentrations in conventional and organic cultivars (in %), were: 72 and 72 (moisture); 0.87 and 0.90 (ashes); 1.5 and 1.4 (proteins); 0.63 and 0.54 (lipids) and 24.8 and 23.9 (carbohydrates).

Mineral content in mustard leaves according to the cooking method

This work evaluated the influence of the cooking methods (cooked in a water bath, in a stove, and in a microwave oven) on the mineral composition of mustard leaves (Sinapis alba). So, raw and cooked samples were digested and afterward the elements calcium, magnesium, potassium, sodium, iron, zinc, phosphor, barium and sulfur were determined using inductively coupled plasma optical emission spectrometry (ICP OES). The experimental work involved a set of five samples from different locations, processed in triplicates. The results were evaluated employing Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA) and Linear Discriminate Analysis (LDA). All techniques showed that the mineral content of the raw and cooked samples in a water bath is different from the samples cooked in stove and microwave oven. Especially for potassium, whose content is strictly controlled for chronic renal patients, this study showed that cooking using microwave oven has the greatest efficiency for reduction.