Physical and chemical stability after pasteurization of a colloidal beverage containing lutein

The daily intake of lutein is related to the maintenance of visual and cognitive health. In the food industry, lutein may be used as a bioactive ingredient and/or a natural pigment. However, structural changes may occur due to oxidation and isomerization during processing and/or storage, affecting the carotenoid stability. This work evaluated the physical and chemical stability of a colloidal beverage mimic system containing lutein after pasteurization (63±2°C for 30 min), during a 15-day storage period under accelerated conditions (45ºC). Three beverages - non-pasteurized (NP), conventional-pasteurized (CP) and microwave-pasteurized (MWP) were prepared based on an isotonic drink formulation with 10% lutein carrier emulsion. During storage, total carotenoids, color, zeta potential, and gravitational separation were evaluated. Just after preparation (Day 0), CP and MWP presented higher initial carotenoid contents (1.2 and 1.05 mg lutein/200 mL beverage, respectively) in comparison to NP (0.92 mg lutein/200 mL beverage). After 15 days of storage at 45 ºC, the total content of carotenoids reduced 75 % (CP and NP beverages) and 83% (MWP) when compared to day 0. Since the only source of pigment in the beverages comes from lutein, the reduction of carotenoids is closely related to the decrease in the color intensity and the increase in the brightness. CP and MWP presented higher loss of tonality (57%) than NP (37%). For all beverages, the zeta potential value between 10 and 30 mV was an indicative of instability, evidenced from the fifth day of storage, when flocculation and sedimentation were observed, and the sedimentation index was eight times higher for pasteurized beverages (42%) than the NP (5%). NP-beverage showed better stability than the pasteurized ones. Microwave pasteurization was the most susceptible condition to changes. The temperature may have interfered with the physical stability of the pasteurized beverage, leading to droplet flocculation and phase separation.