Research Article EDTA and a‐tocopherol improve the chemical stability of astaxanthin loaded into nanostructured lipid carriers Fardin Tamjidi 1 , Mohammad Shahedi 1a , Jaleh Varshosaz 2a and Ali Nasirpour 1 1 Department of Food Science and Technology‐Center of Excellence for Safety and Quality of Foods, College of Agriculture, Isfahan University of Technology, Isfahan, Iran 2 Department of Pharmaceutics, Faculty of Pharmacy and Novel Drug Delivery Systems Research Center, Isfahan University of Medical Sciences, Isfahan, Iran Nanostructured lipid carriers (NLC) as a promising delivery system have specific advantages over other nanocarriers for food applications. This study was aimed to evaluate the effect of different antioxidants on physical and chemical stability of NLC containing astaxanthin, a hydrophobic nutraceutical. Antioxidants (EDTA, ascorbic acid, a‐tocopherol, coenzyme Q 10 ) were added to aqueous and/or lipid phases. Tween 80 and lecithin were utilized as stabilizers; NLC formulations were produced by melt emulsification‐sonication technique, and then stored at 35°C for 15 days. Except formulations with high levels of EDTA or ascorbic acid, others yielded small nanoparticles (Z‐average  94 nm) which were stable to growth during storage. Of these antioxidants, only EDTA and a‐tocopherol increased the stability of astaxanthin without causing physical instability, and EDTA was more efficient. The utilization of a‐tocopherol and EDTA in combination was more effective than using them individually. Storage temperature and artificial light had significant effects on the stability of astaxanthin in NLC. These results provide useful information for choosing antioxidants and storage conditions to further protection of nutraceuticals within NLC. Practical applications: Fortification of aqueous‐based foods with carotenoids is greatly restricted owing to their poor water‐solubility, chemical instability, and low bioavailability. NLC immobilize the encapsulated compounds effectively, and can improve their stability and bioavailability in aqueous‐based foods. However, pro‐oxidants can still decrease the chemical stability of NLC. Different antioxidants were employed to further increase the chemical stability of astaxanthin‐loaded NLC. It was found that degradation of astaxanthin in NLC could be significantly reduced by utilizing proper chelators and free radical scavengers. But, higher temperatures and light could still decrease the stability of astaxanthin. These results provide strong evidences for utilizing metal chelators and free radical scavengers in carotenoids‐loaded NLC, and for storing commercial foods and beverages fortified with these nanoparticles at low temperature and darkness. Keywords: Antioxidants / Astaxanthin / Chelators / Nanostructured lipid carriers (NLC) / Stability Received: December 27, 2013 / Revised: March 25, 2014 / Accepted: April 8, 2014 DOI: 10.1002/ejlt.201300509 1 Introduction With the increasing public perception of a strong correlation between food and human health, food manufacturers are trying to enrich staple foods and beverages with “health promoting substances.” Astaxanthin, a type of carotenoids, has powerful antioxidant activity and possesses many nutraceutical functions, such as general enhancement of Correspondence: Prof. Jaleh Varshosaz, Department of Pharmaceutics, Faculty of Pharmacy and Novel Drug Delivery Systems Research Center, Isfahan University of Medical Sciences, Isfahan 81746‐73461, Iran E‐mail: varshosaz@pharm.mui.ac.ir Fax: þ98 313 6680011 Abbreviations: AA, ascorbic acid; astaxanthin‐NLC, astaxanthin‐loaded nanostructured lipid carriers; EDTA, ethylenediaminetetraacetic acid; NLC, nanostructured lipid carriers a Equally contributing authors. 968 Eur. J. Lipid Sci. Technol. 2014, 116, 968–977 ß 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.ejlst.com