Total phenolics content, anthocyanins, and dietary fiber content of apple pomace powders produced by vacuum-belt drying.

摘要

BACKGROUND: Apple pomace is a waste material from apple juice processing, and contains significant amounts of dietary fiber and phytochemicals. Many of these compounds may be degraded post-pressing and during drying operations. Continuous vacuum-belt drying (VBD) was studied as a means of drying and maintaining quality of apple pomace. The color and chemical properties of samples dried by vacuum-belt drying at different temperatures were evaluated including total phenolics content (TPC), monomeric anthocyanins (TMA) and dietary fiber content (TDF). RESULTS: VBD powders were pale golden yellow, and those dried at 80 degrees C did not differ in L*, a* and b* values from freeze-dried powders. VBD pomace had 44.9 to 51.9 g gallic acid equivalents kg-1 TPC, with greatest retention for pomace dried at 80 and 95 degrees C. TPC for pomace dried at 80 or 95 degrees C was not significantly different from that for freeze-dried pomace. TMA levels (74.0 mg C3G kg-1, where C3G is cyanidine 3-O-glucoside equivalents) were highest in pomace vacuum dried at 80 degrees C. TDF ranged from 442 to 495 g kg-1 in vacuum-dried pomace and was not significantly different from TDF of freeze-dried poamce (480 g kg-1). CONCLUSION: In all cases, TPC, TMA and TDF were higher in VBD pomace than in freeze-dried whole apple, while VBD pomace prepared at 80 or 95 degrees C had fiber and phytochemical levels similar to freeze-dried powders