Effect of temperature, pH, and time factors on the stability and antioxidant activity of the extracted astaxanthin from haematococcus microalgae (Haematococcus pluvialis)

One of the important factors in the use of natural pigments in various foods is their stability and preservation of their antioxidant properties under the production and storage conditions. Astaxanthin is one of these natural pigments that microalgae are one of its resources. In the present study, after the extraction of astaxanthin from hematococcus microalgae (Haematococcus pluvialis) by a combined method (HCL-Acetone), the effect of temperature, pH, and time parameters on its stability and antioxidant activity (DPPH free radical scavenging activity and reducing power of ferric) were evaluated. The results showed that the effect of temperature, pH and time factors alone and the interactions between the time and temperature were significant (p<0.05). However, the interactions of pH with time, pH with temperature, and the interaction of three factors together on the concentration and stability of astaxanthin were not significant (p>0.05). According to the findings, the antioxidant activity and pigment stability at 4 °C was more than 20 °C and with increasing the storage time, these properties were decreased. The pH changes did not have much effect on the pigment properties, although the results at pH=5.5 were relatively better than pH=4.5. Among the studied treatments, DPPH free radical scavenging activity as well as the reducing power of the extracted pigment ranged from 45.5-93.11% and absorption of 0.31-0.81 at 700 nm, respectively. This property makes it possible to use this pigment in food products as an antioxidant. However, use of various methods such as coating the pigment for using in heat-treated foods is recommended due to the low stability of the pigment at the higher temperatures.