Extraction Of Red Radish Pigment And Improvement Of Stability

In this paper, the countercurrent extraction process of the red radish pigment was studied to improve its extraction efficiency, using the red radishes bought in Chongqing as raw material. Moreover, the stability of the pigment was enhanced by adding stabilizer and chemical modification.1. The red radish pigment was extracted by single-stage extraction and countercurrent extraction in phosphoric acid-water medium within optimized operation conditions. The optimum technique parameters of single-stage extraction were obtained as follows: raw/liquid ratio 1:5 (W/W), extraction time 2.5 h and extraction temperature room-temperature. Under these conditions, the extraction efficiency was about 55%. The optimum technique parameters of countercurrent extraction were as follows: raw/liquid ratio 1:20, extraction stage 5, extraction time 20 min, extraction temperature room-temperature, and extraction efficiency reached to 92% with these parameters. Compared with single-stage extraction, the process of countercurrent extraction had higher raw material utilization, higher extraction efficiency and lower energy losses.2. The effects of Fe³⁺ on red radish pigment were also investigated in this thesis. The results showed that Fe³⁺ had hyperchromic effect on red radish pigment. However, as time went by, Fe³⁺ caused the ABS value of the pigment reducing, which indicated that this pigment was susceptible to Fe³⁺. Therefore, the study on how the stabilizer improved its stability of red radish pigment was carried out. Results showed that the pigment stability could be enhanced when mole ratios of DMY to Fe³⁺, EDTA to Fe³⁺ and Vc to Fe³⁺ were 2:5, 1:1 and 2:5, respectively. Feed sequences had significant influences on the pigment, pigment + Fe³⁺ + EDTA and pigment + Fe³⁺ + Vc could get higher pigment stability. EDTA could improve the pH stability of the pigment containing Fe³⁺ and had few effects on its heat stability, while Vc could improve its pH stability and reduce its heat stability.3. This paper studied three methods of modification (acetyl salicylic esterification, carboxymethyl etherification, and isopentenyl etherification) and analyzed both the stability and the antioxidation of the red radish pigment and modified pigment. Stability experiments indicated that pigment modified by acetyl salicylic had higher stability to pH, heat, light and Fe³⁺. Carboxymethyl pigment had higher stability to pH, heat and light with little improvement of the stability to Fe³⁺. The stability of isopentenyl pigment to heat, light and Fe³⁺ was enhanced, but its stability to pH was reduced. Their total antioxidative activity and the scavenging ability of hydroxyl radical were determined by ABTS assay and phenanthroline method respectively, with Vc as the control group. The results showed that the scavenging ability of ABTS radical was reduced slightly by esterification but was still higher than that of Vc, while the scavenging ability of hydroxyl radical was slightly lower than both of the red radish pigment and Vc. Carboxymethyl modification did not change its scavenging ability of ABTS radical and hydroxyl radical. Isopentenyl modification enhanced its scavenging ability of ABTS radical, which was higher than that of Vc, while its scavenging ability of hydroxyl radical remained the same.