Nutritional Estimation of Changes in Mineral Content During Frozen Storage of White Asparagus

Abstract

Nine essential elements (copper, iron, zinc, manganese, calcium, magnesium, sodium potassium and phosphorous) were determined in white asparagus (Asparagus officinalis, L.) by flame atomic absorption spectrophotometry in order to examine the possible variations in mineral content caused by frozen storage at -18C for 45 and 90 days. Statistically signlficant differences were determined duringfiozen storage for all the mineral elements investigated, except for Ca, Mg, Na and P which did not exhibit any significant differences @O. 05) and, together with Zn, showed no signlficant modfications under fiozen storage. A diminution in Cu, Fe, Mn and K concentrations was observed during the frozen storage time. Statistically signijcant diferences were established between thicknesses of the asparagus spear in the content of Cu, Fe, Zn, Ca, Na and K and it was seen that the thickness of the asparagus did not fit any specijic model. Between portions, all the elements studied displayed statistically sign ficant differences in their concentrations, except for Ca and K (p>O.O5) and, for all the minerals elements analyzed, the highest levels were found in the apical portion of the asparagus spear, except for Na with a higher content in the basal portion. White asparagus is an adequate food source of mineral elements, except for Na, andfiozen storage does not cause any great variations in the percentages of mineral RDAs (Recommended Dietary Allowances) supplied.

Retention of mineral constituents in frozen leafy vegetables prepared for consumption

“…According to Haring and Delft (1981), the leaching of mineral compounds depends on their content in water. Amaro et al (1998) express a similar opinion. The content of mineral constituents analysed in the vegetables was in each case measured in the tap water used in technological and culinary processing.…”

Zinc retention in vegetables according to the method of preparation for consumption

“…In the case of all the vegetables investigated, the percentages of ND considerably (Table II), confirming that all the raw and processed vegetables in the present study are adequate food sources of zinc. Amaro et al (1998Amaro et al ( , 1999 also showed very high ND values of fresh and frozen asparagus.…”

“…It was not possible to verify the zinc levels given for all the investigated species since the relevant data could not always be found in the literature. In cases in which significantly different levels of zinc were quoted by some authors, the differences were due to numerous factors -the year of investigation and the locality, the cultivar, the thickness, the size and the usable part -with differences of up to several dozen-fold recorded in the investigated material (Amaro et al 1998(Amaro et al , 1999Bhattacharjee et al 1998;Cheng and Ruichi 1998;Martinez et al 1998;Kmiecik et al 2000;Słupski et al 2005).…”