Effect of Processing on Magnesium Content of Green Leafy Vegetables

In the present paper, we have studied the effect of different food processing techniques like blanching, microwave processing, boiling, frying, and different drying methods on depletion of minerals especially magnesium in green leafy vegetables (leaves of Trigonella foenum, common name methi, and Spinacia oleracea, common name spinach) using laser-induced breakdown spectroscopy (LIBS). These processing techniques are frequently used at home as well as in food processing industries. The LIBS spectra of the fresh leaves of methi and spinach and their pellets (made by drying, grinding, and pressing the leaf) were recorded in a spectral range from 200 to 500 nm. After applying the above processing techniques, different pellets of these leaves were made in the same way. The LIBS spectra of these processed leaf samples were also recorded using the same experimental parameters as used for the fresh samples. Our results show that among the above processing techniques, frying most significantly reduces the content of magnesium, whereas the least loss of Mg is observed in the case of boiling. We have verified this result by recording the LIBS spectra of the intact fresh leaves and of those processed with different techniques. The same results were also obtained from the LIBS spectra of the intact leaves and their pellets. The LIBS spectra of methi and spinach leaves were also recorded after drying them using two different techniques — drying in vacuum and in a hot air oven; the results show that vacuum drying is more suitable in terms of minimizing loss of Mg content in leaves.