Research Article Influence of Rosemary Extract Addition in Different Phases on the Oxidation of Lutein and WPI in WPI-Stabilized Lutein Emulsions Duoxia Xu, 1 Zhanqun Hou, 2,3 Guorong Liu, 1 Yanping Cao , 1 Atikorn Panya, 4 Hang Xiao, 5 and Will Dixon 5 1 Beijing Advanced Innovation Center for Food Nutrition and Human Health (BTBU), School of Food & Health, Beijing Engineering and Technology Research Center of Food Additives, Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing Technology & Business University, Beijing, China 2 China National Research Institute of Food and Fermentation Industries Co., Ltd., Beijing 100015, China 3 Beijing Key Laboratory of the Innovative Development of Functional Staple and the Nutritional Intervention for Chronic Disease, Beijing, China 4 Food Biotechnology Research Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC), 113 ailand Science Park, Phaholyothin Rd., Khlong Nueng, Khlong Luang, Pathumthani 12120, ailand 5 Department of Food Science, University of Massachusetts, Amherst, MA, USA Correspondence should be addressed to Yanping Cao; caoyp@th.btbu.edu.cn Received 5 June 2019; Revised 24 September 2019; Accepted 30 September 2019; Published 10 January 2020 Guest Editor: Fuguo Liu Copyright © 2020 Duoxia Xu et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e aim was to investigate rosemary extract with different addition methods affecting the physicochemical stability of WPI-coated lutein emulsions and examine the correlations between lutein degradation and WPI oxidation during storage. First, lutein emulsions containing different concentrations of rosemary extract in the oil phase were prepared. Second, lutein emulsions containing rosemary extract in the oil phase or water phase were studied along with the kinetic reaction of lutein degradation. Moreover, the impact of rosemary extract on the oxidation of WPI and their products was also determined. It was noticed that rosemary extract at 0.05 wt.% exhibited the best protection of lutein. According to the kinetics analysis of lutein degradation, the direct addition of rosemary extract in the oil phase was more suitable for retarding the degradation of lutein in emulsion than the addition in the aqueous phase due to it being partitioned at the interface. Meanwhile, it was revealed that the addition of rosemary extract in the water phase exhibited better inhibition of the WPI oxidation than addition in the oil phase. e understanding of the association and driving forces of rosemary extract in emulsion systems may be useful for the application of rosemary extract in multicomponent food systems. 1. Introduction Lutein is a yellow pigment with two hydroxyl groups in the conjugated polyene chain presented in fruits and vegetables [1]. It has been reported that lutein has the functional properties of reducing incidences of eye diseases such as age- related macular degeneration and reducing the risk of cardiovascular diseases, atherosclerosis, and cancer diseases [2, 3]. However, the conjugated polyene chain of lutein is susceptible to degradation during processing and storage. e degradation of lutein produced a number of initial oxidation products, such as carbon-peroxyl triplet biradicals and epoxides [4]. ese reactions can lead to loss of color and bioactivity of lutein in food products. Dispersing the lipid soluble lutein into the oil phase of oil-in-water emulsions could improve its oxidative stability by emulsifying the oil phase solution with the aqueous phase containing emulsifiers [5]. Some studies have reported the stability of delivery systems enriched with lutein [6, 7]. e oxidation mechanism of lutein was comprehensively reviewed by Boon et al. [8]. Several factors could influence the degradation of lutein in oil-in-water emulsions including Hindawi Journal of Food Quality Volume 2020, Article ID 5894646, 10 pages https://doi.org/10.1155/2020/5894646