Effect of high pressure treatment on colour degradation of fresh Chinese bayberry, fresh-cut yacon and carrot

The effects of high pressure treatment on colour degradation of fresh Chinese bayberry, fresh-cut yacon and carrot were studied. Yacon slices, Chinese bayberry and carrot slices were treated at 300-500 MPa for 5-20 min, 400-600 MPa for 2 and 5 min and 200-600 MPa for 2-20 min, respectively. CIE L, a, b values and combined colour index (ΔE and W.I.) were used to describe their colour. Results showed that, after high pressure treatment, the colour indexes of yacon slices, Chinese bayberry and carrot slices changed differently. The L value and W.I. value of yacon slices decreased significantly. The a value of Chinese bayberry, however, remained constant or even increased while the L value decreased. The carrot had a better retention of L, a and b values at 400-600 MPa. Significance analysis showed that both vacuum package and ultra-high pressure treatment affected the colour degradation of yacon significantly. But there were no significant differences (P > 0.05) after extending the treatment times at the same pressure. The original colour of Chinese bayberry and carrot were better retained after treatments at 500 MPa/5 min and 400 MPa/10 min, respectively. This indicated that overhigh pressure and overlong holding time were not necessary for colour preservation of fresh Chinese bayberry and fresh-cut carrot.