Iron concentration, bioavailability, and nutritional quality of polished rice affected by different forms of foliar iron fertilizer Wanling He a,b,1 , M.J.I. Shohag a,1 , Yanyan Wei a,c , Ying Feng a,⇑ , Xiaoe Yang a a Ministry of Education (MOE) Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, People’s Republic of China b College of Animal Science and Technology, Henan Science and Technology University, Luoyang 471003, People’s Republic of China c College of Agriculture, Guangxi University, Nanning 530005, People’s Republic of China article info Article history: Received 26 March 2013 Received in revised form 27 June 2013 Accepted 1 July 2013 Available online 8 July 2013 Keywords: Polished rice Iron Foliar application Bioavailability Nutritional quality abstract The present study compared the effects of four different forms of foliar iron (Fe) fertilizers on Fe concen- tration, bioavailability and nutritional quality of polished rice. The results showed that foliar fertilisation at the anthesis stage was an effective way to promote Fe concentration and bioavailability of polished rice, especially in case of DTPA-Fe. Compared to the control, foliar application of DTPA-Fe increased sulphur concentration and the nutrition promoter cysteine content, whereas decreased phosphorus concentration and the antinutrient phytic acid content of polished rice, as a result increased 67.2% ferrtin formation in Caco-2 cell. Moreover, foliar DTPA-Fe application could maintain amylase, protein and min- erals quality of polished rice. According to the current study, DTPA-Fe is recommended as an excellent foliar Fe form for Fe biofortification program. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Rice is the most widely consumed staple food crop and a pri- mary food source for 50% of the world’s population (Fitzgerald, McCouch, & Hall, 2009). The nutrient-rich aleurone layer and embryo are traditionally removed before human consumption, typically leaving only the starch-rich endosperm as the edible part (Bouis & Welch, 2010; Wei, Shohag, Yang, & Zhang, 2012). There- fore, the resulting polished rice is a poor source of essential micro- nutrients, such as iron (Fe) and zinc (Zn) (Bouis & Welch, 2010; Khush, 1997). Jiang, Wu, Feng, Yang, and Shi (2007) found that the average Fe content in milled rice of 274 genotypes was 5.4 ± 2.9 lg/g. A survey of 11,400 rice samples revealed that brown rice contained 10.0–11.0 lg/g Fe, whereas the milled rice con- tained 2.0–3.0 lg/g Fe (Martínez et al., 2010). As the polished rice contains an average of only 2.0 lg/gFe (Johnson et al., 2011; Yuan, Wu, Yang, & Lv, 2012), which is much lower than the international biofortification target for polished rice Fe concentration of 14.0 lg/ g. Thus, an inadequate intake of Fe from staple food leads to Fe malnutrition in humans, affecting two billion people (Sperotto, Ric- achenevsky, Waldow, & Fett, 2012), most of them in developing countries (Yang, Chen, & Feng, 2007). Many approaches have been chosen to increase the Fe content in rice grains and ameliorate the Fe malnutrition, including con- ventional breeding, genetic engineering and agronomic approaches (Sperotto et al., 2012; Wei et al., 2012; Yang et al., 2007). Among them, fertilisation, especially foliar Fe spray is considered as a rapid and efficient way to reach the Fe biofortification target in recent years (Aciksoz, Yazici, Ozturk, & Cakmak, 2011; Fang et al., 2008; Yuan et al., 2012). However, the Fe intake from food is not only determined by the net Fe concentration but, to a large extent, also by the Fe bioavailability (Glahn, Cheng, Welch, & Gregorio, 2002; Promüthai et al., 2009). Ideally, the Fe bioavailability in grains should be evaluated through in vivo human studies, but performing large-scale screenings is complex and costs limit their applicability (Glahn et al., 2002; Promüthai et al., 2009; Wei et al., 2012). In re- cent years, an in vitro digestion/Caco-2 cell model had been pro- posed as an alternative to in vivo methods for estimating mineral bioavailability in diets, as this cell line mimics the gastric and intestinal digestion of humans and has been successfully used to assess Fe bioavailability in cereal grains (Glahn et al., 2002; He, Feng, Li, & Yang, 2008; Wei et al., 2012). FeSO 4 is a widely used form of foliar Fe fertilizer (Fang et al., 2008; Wei et al., 2012; Yuan et al., 2012); however, Fe(II) is highly unstable and is easily converted to plant-unavailable, solid Fe(III) forms. Therefore, increasing the stability of Fe(II) and controlling its release speed is very important for enhancing the absorption efficiency of foliar Fe fertilizer (Fernández & Ebert, 2005). Synthetic 0308-8146/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodchem.2013.07.005 ⇑ Corresponding author. Tel.: +86 13588028635; fax: +86 571 88982907. E-mail address: yfeng@zju.edu.cn (Y. Feng). 1 These authors contributed equally to this work. Food Chemistry 141 (2013) 4122–4126 Contents lists available at SciVerse ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem