Physicochemical property changes of cabbage outer leaves upon preparation into functional dietary fiber powder

White cabbages (Brassica oleracea L. var. capitata) are important sources of dietary fiber (DF) and glucosinolates, which are claimed to possess anticarcinogenic activity. Although the potential use of cabbage outer leaves as starting raw materials to produce functional dietary fiber powder (DFP) has been reported, the effects of various processing steps that are necessary to produce the powder have not been systematically investigated. To allow minimization of losses of glucosinolates during production of DFP the effects of processing steps, i.e., slicing, blanching and drying, on the changes of total glucosinoltates in cabbage outer leaves were investigated; the changes of DFP compositions and color were also investigated. It was noted that the preparation steps did not lead to any significant changes of the DFP compositions. On the other hand, steam blanching was noted to better preserve glucosinolates than water blanching. Drying methods and conditions did not lead to any significant effect on the DFP compositions; however vacuum drying led to better retention of glucosinolates. Color of the DFP was not affected by the drying methods and conditions. The results suggested that cabbage outer leaves should be prepared into DFP by steam blanching prior to slicing in combination with vacuum drying at 80 °C.

► Cabbage outer leaves were used as raw material to produce dietary fiber (DF) powder.
► Processing steps did not have significant effect on changes of DF compositions.
► Steam blanching could preserve glucosinolates better than water blanching.
► Steam blanching prior to slicing followed by vacuum drying was suggested for DF powder production.