Effect of UV-B light and different cutting styles on antioxidant enhancement of commercial fresh-cut carrot products Wen-Xian Du a,⇑ , Roberto J. Avena-Bustillos b , Andrew P. Breksa III a , Tara H. McHugh a a Processed Foods Research Unit, United States Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan St., Albany, CA 94710, USA b Department of Biological and Agricultural Engineering, University of California, One Shields Ave., Davis, CA 95616, USA article info Article history: Received 28 January 2012 Received in revised form 29 February 2012 Accepted 22 March 2012 Available online xxxx Keywords: Ultraviolet light Fresh-cut carrots Total soluble phenolics Antioxidant capacity abstract Wounding stresses resulting from fresh-cut processing are known to enhance the antioxidant capacity (AC) of carrots by increasing the synthesis of phenolic compounds. Ultraviolet-B (UV-B) light exposure further promotes the formation of phenolic compounds. Changes in total soluble phenolics (TSP), 5-O-caf- feoylquinic acid (5-CQA), total carotenoids, AC, and phenylalanine ammonia-lyase (PAL) activity of five commercial fresh-cut carrot products (baby carrots, carrot stixx, shredded carrots, crinkle cut coins, and oblong chips) were evaluated after exposure to UV-B dosage at 141.4 mJ/cm 2 . Significant increases in TSP, AC and 5-CQA levels were observed for each sample following UV-B exposure. Increases in PAL activity were also observed in all carrot products, except crinkle cut coins. Total carotenoids of the carrot products were unchanged by UV-B exposure. Increases in AC levels corresponded directly with increases in the area/weight ratio (exposure area) of the fresh-cut carrot products. Published by Elsevier Ltd. 1. Introduction Epidemiological and clinical investigations have associated diets rich in fruits and vegetables with reduced risk of cardiovascu- lar disease, cancer, atherosclerosis, and other age-related diseases induced by free radicals (Dudonné, Vitrac, Coutiére, Woillez, & Mérillon, 2009; Jacobo-Velázquez & Cisneros-Zevallos, 2009; Moon, Wang, & Morris, 2006; Nijveldt et al., 2001). This health ben- efit can be partly attributed to the presence of antioxidant com- pounds, especially phenolic compounds (Sandra, 2004; Willcox, Ash, & Catignani, 2004). Water-soluble phenolic compounds repre- sent some of the most potent antioxidants and depending on diet can be consumed at quantities reaching 1 g/day, a level that is approximately 10 times higher than the typical vitamin C intake (Scalbert, Johnston, & Saltmarsh, 2005). Therefore, increasing the levels of phenolic compounds in food plants has the potential for improving human health. Among vegetables, carrots are now increasingly consumed, mainly due to their pleasant flavor and perceived health benefits related to their vitamins, minerals and dietary fiber (Alasalvar, Grigor, Zhang, Quantick, & Shahidi, 2001). Carrots are one of the most popular vegetables in the United States and fresh-market car- rot consumption has been increasing over the past few decades. About 80% of fresh-market carrots are purchased at retail and consumed at home, with the majority consisting of fresh-cut/baby carrots (Lucier & Lin, 2007). The predominant carotenoid identified in carrot cultivars is b-carotene (Alasalvar et al., 2001). Carrots also contain an array of phenolic compounds, of which 5-O-caffeoylqui- nic acid (5-CQA, chlorogenic acid) has been identified as the most abundant phenolic present in carrot cultivars (Babic, Amiot, Nguyen-The, & Aubert, 1993; Klaiber, Baur, Koblo, & Carle, 2005; Kreutzmann, Christensen, & Edelenbos, 2008). Interest in the role of antioxidants in human health has prompted researchers in the fields of food science and horticulture to compare the antioxidant content of fruits and vegetables and to assess how their content may be maintained or even enhanced through cultivar development, harvesting methods, post-harvest procedures, processing technologies and storage conditions (Alasalvar, Al-Farsi, Quantick, Shahidi, & Wiktorowicz, 2005). The accumulation of phenolic compounds and corresponding increases in AC levels in minimally processed carrots during storage has been observed by several groups (Babic et al., 1993; Cisneros-Zevallos, 2003; Howard & Griffin, 1993; Klaiber et al., 2005; Reyes, Villarreal, & Cisneros-Zevallos, 2007; Ruiz-Cruz, Islas-Osuna, Sotelo-Mundo, Vázquez-Ortiz, & González-Aguilar, 2007; Simões, Allende, Tudela, Puschmann, & Gil, 2011). The accumulation of phenolic com- pounds in these cases has been linked with the wound-induced activation of phenylalanine ammonia-lyase (PAL) synthesis (Howard & Griffin, 1993). Wounding, in combination with other abiotic stresses, such as hormones and UV-B radiation hormesis, can synergistically enhance the accumulation of bioactive phenolic 0308-8146/$ - see front matter Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.foodchem.2012.03.097 ⇑ Corresponding author. Tel.: +1 (510) 559 6148; fax: +1 (510) 559 5851. E-mail addresses: Wen-Xian.Du@ars.usda.gov (W.-X. Du), Roberto.Avena@ ars.usda.gov (R.J. Avena-Bustillos), Andrew.Breksa@ars.usda.gov (A.P. Breksa III), Tara.Mchugh@ars.usda.gov (T.H. McHugh). Food Chemistry xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem Please cite this article in press as: Du, W.-X., et al. Effect of UV-B light and different cutting styles on antioxidant enhancement of commercial fresh-cut carrot products. Food Chemistry (2012), http://dx.doi.org/10.1016/j.foodchem.2012.03.097