DETERMINATION OF MAGNESIUM IN SPINACH UNDER DIFFERENT COOKING METHODS

Background and objectives: Magnesium is necessary for about 300 biochemical reactions of the body, with a requirement of 260 mg/d for a healthy adult. Therefore the aim of the study was to determine how the content of magnesium in spinach varies under different cooking processes. Methods: To carry out this experience it was used 10 kg of spinach, acquired and processed on the same day. For the sampling, each plant was divided into 5 equal parts, obtaining 5 lots submitted to different cooking techniques: Lot 1: raw spinach, which was reserved for analysis; Lot 2: spinach cooked by boiling; Lot 3: sauteed spinach; Lot 4: steamed spinach; Lot 5: spinach cooked using microwave. It was determined the centesimal composition of raw and cooked product applying official laboratory techniques. The magnesium content was determined by atomic absorption spectrometry on ash dilution. In order to establish if there is statistically significant differences. It was applied analysis of variance (ANOVA) for a level of significance alpha ≤0.05. Results: The loss of humidity was statistically significant for sauteed spinach (73 g%) and cooked with microwave (60 g%). The fat content is increased from 0.3 g to 12.58 g in sauteed spinach, which represented a 5.4 times more caloric intake. The magnesium content was 64±3 mg% in raw spinach; by boiling 52±2 mg%; sauteed 86±3 mg%; steamed 63±3 mg% and microwave 99±4 mg%. Conclusions: Spinach processed with microwaves presented the greatest loss of weight and volume (-70%), but concentrated in a 50% the magnesium content, in relation with the loss of humidity. The one cooked by boiling had the greatest loss of magnesium (leaching of minerals). Steamed spinach maintained the content of magnesium. The sauteed one had a loss of weight and volume of 18%, and also it concentrated 35% magnesium respect to raw spinach, but increased its caloric value.