Liberation of lutein from spinach: Effects of heating time, microwavereheating and liquefaction

Lutein, abundant in dark leafy vegetables, has been associated with several health promoting effects. Still, to what extent different preparation conditions and practices affect the liberation of lutein from food is not fully understood. Here, we compared a range of domestic methods under realistic conditions to prepare spinach, the most common lutein-rich vegetable. After preparations, samples were processed by in vitro digestion and lutein was quantified by HPLC. Data indicate that short-term and medium-term heating of spinach, independent of heating method, substantially reduced liberated lutein and reduction was most pronounced after long boiling times. Interestingly, the loss of lutein in heated samples was partly compensated when samples were reheated in the microwave. However, the highest yield of liberated lutein was obtained from liquefied spinach. Additional dairy enhanced the liquefaction effect. Thus, for optimal liberation of lutein, liquefaction of raw spinach appears to be the method of choice.