Effects of storage conditions on phytochemical and stability of purple corn cob extract powder
Corn (Zea mays L.) has been primarily consumed in South America with various colors such as white, yellow, red and purple. Purple corn, a special corn variety with high anthocyanin concentration in aleurone layer and cob (Zhang et al., 2010), is reported to possess antioxidant ability higher than the non-colored corn (Lopez-Martinez et al., 2011). On Thailand, the developed variety of waxy purple corn presents dark purple color due to the considerable the high amount of anthocyanins, phenolics and antioxidant activity, leading to the increased consumption of waxy purple corn as fresh foods (Harakotr et al., 2014); meanwhile, its cob tends to be largely neglected. Ondeed, the cob of purple corn is reported to contain high amount of anthocyanins, including cyanidin-3-glucoside, pelagonidin-3glucoside and peonidin-3-glucoside (Yang et al., 2008); additionally, protocatechuic, hydroxybenzoic, vanillic, caffeic, p-coumaric and ferulic acid, the majority of phenolic compound, are also found in the cob (Harakotr et al., 2014), thereby becoming one of a most interesting source of nutraceutical food. Certain investigations of clinical study confirm that waxy purple corn cob (WPC) offers considerable benefits in various biological activities, e.g. preventing hyperlipidemia and cerebrovascular diseases (Zhang et al., 2010). Consequently, the development of value added products from WPC to be a potential source of nutraceutical is of great interest. Nevertheless, most of phenolics and anthocyanins are sensitive and decomposed by environmental factors during storage, such as temperature, light and pH (Ersus & Yurdagel, 2007). Anthocyanin molecule tends to change and transform into other degraded products during storage or heat processing (Rødtjer et al., 2010; Sivamaruthi et al., 2016). However, there is an effective technique able to enhance the stability of those compounds against storage conditions called microencapsulation. This technique mainly relies on spray drying, where the compounds are entrapped by coating material, thus protecting them from environment factors. Hydroxypropyl beta-cyclodextrins (HPβCD) is a chemical modification of beta-cyclodextrins from esterification at the hydroxyl groups of the glucose residues. Hydroxypropyl substitutions help to improve solubility and their binding ability, resulting in increasing the stability of core compound (Khan et al., 1998). Nevertheless, recently little literature has focused on microencapsulation using HPβCD as a coating material by spray drying of anthocyanin and phenolic compound in plant extract (Wilkowska et al., 2016). Due to those benefits, the addition of this novel coating agent encourages food industry to preserve the unstable compounds in WPC extract in this study. Significant retention of phytochemical compounds during storage is an ideal characteristic for microcapsules powder. However, there is limited information on the storage stability of phytochemical Effects of storage conditions on phytochemical and stability of purple corn cob extract powder