Color is the most important indicator of taste and flavor, both vital sensory properties of food and beverages. The processing industry commonly uses artificial food colorants derived from petroleum or coal, called coal tar dyes. These dyes may cause attention-deficit/hyperactivity disorder, genotoxicity, neurotoxicity and/or carcinogenicity. In an era of “natural ingredients”, there is increasing customer pressure for exploring natural alternatives of synthetic dyes. Anthocyanins can be used as a replacement of synthetic FD&C Red 40 dye. However, their recovery from conventional sources is uneconomical due to higher inputs and lower economic value of the processing residues. The potential of using colored corn as a viable source of anthocyanins was explored.
Anthocyanins containing purple and blue corn were fractionated using laboratory scale wet milling, dry milling and dry grind processes; coproduct yields were compared with those from conventional yellow dent corn. In wet milling, starch yields of colored corn were 6.7 to 8.7% less than conventional yellow dent corn on dry basis (db). In dry milling, large grit yields of colored corn were <25% (db), implying a softer endosperm composition. In the dry grind process, mean final ethanol concentrations for colored corn were 2.7% (v/v) less than those from yellow dent corn. Colored corn may be used in all three processes; however, with some yield differences. Colored corn coproducts from three processes were analyzed for anthocyanin content. Corn processing can generate coproducts with disproportionately higher anthocyanin contents. Location of pigments in colored corn kernels differed. Anthocyanins in the blue and purple corn were located in the aleurone and pericarp, respectively. Purple corn contained 13 times higher anthocyanins compared to blue corn. For purple corn, 80% of the anthocyanins were found in steepwater from wet milling and 48% in pericarp from dry milling process. Corn processing was tailored in such a way so as to recover coproducts with maximum anthocyanin concentrations while other fractions, which remain unaffected, could be further utilized.
To increase anthocyanin recovery, dry milled purple corn pericarp was steeped using different combinations of wet milling chemicals. In the treatment containing SO2 (0.2%), lactic acid (0.5%) and water, 22.9 g anthocyanins/kg pericarp was quantified while the treatment containing only water recovered 7.1 g anthocyanins/kg pericarp. Although addition of SO2 facilitated higher anthocyanin extraction, it had a bleaching effect on the final extract color. Cyanidin-3-glucoside and its acylated form were the most dominant anthocyanins in treatments containing SO2 and lactic acid while the condensed forms were most abundant in the treatment containing only water. A 100 g dry milling protocol was developed which allowed estimation of coproduct yields for corn hybrids with low standard deviations of means. Crude oil contents of large and medium grits from hard endosperm varieties were comparable to those reported for similar lab scale studies. Due to the absence of a roller milling step, true sized large grits were recovered. This protocol should be helpful in estimating dry milling characteristics of newly developed colored corn varieties with relatively small amounts of material
