LYOPHILIZATION OF BLACKBERRY PULP-CONCENTRATED MILK MIXTURE: ANTIOXIDANT ACTIVITY EVALUATION

The blackberry (Rubus spp.), a small fruit grown in a temperate climate, shows an attractive color ranging from purple-red to blue, due to the high content of bioactive compounds. Many studies have reported the importance of these natural pigments as protectors and, or, inhibitors of degenerative disorders; however, data regarding the bioactive compounds in blackberry cultivated in Brazil are rare. In addition, the bioactive compounds contained in blackberry such as anthocyanins, possess antioxidant properties, acting as free radical scavengers and are also frequently linked to the prevention of cardiovascular diseases. Thus, the objective of the present study was to evaluate the antioxidant activity of powders from blackberry pulp-concentrated milk by the lyophilization process. The antioxidant activity against the peroxyl radical (ROO˙) was measured by ORAC assay, which is based on monitoring the effect of the hydrophilic extract or standard (Trolox) on the fluorescence decay resulting from ROO˙ induced oxidation of fluorescein. The results were expressed as µmol of Trolox equivalent/ g of sample. All of the analyses were conducted in triplicate, and the data were expressed as the mean ± standard deviation (SD); the differences between the samples were detected by ANOVA, followed by Tukey, and the differences were considered to be significant at p < 0.05. In order to determine the influence of lyophilization process on the antioxidant activity, samples of blackberry pulp (in natura), blackberry pulp-concentrated milk mixture (75%/25%, m/m) and lyophilized blackberry pulp-concentrated milk were analyzed. The results ranged from 113.2 to 203.3 µmol of Trolox equivalent/ g of sample. The mean values obtained for the blackberry pulp sample was 131.5 ± 18.3; regarding the blackberry pulp-concentrated milk mixture it was found 189.5 ± 13.5 and, for the lyophilized blackberry pulp-concentrated milk the results were 141.9 ± 3.8. The blackberry pulp and the lyophilized blackberry pulp-concentrated milk did not show statistically significant differences. Therefore, the lyophilization process maintained the antioxidant capacity of the bioactive compounds present in the blackberry pulp with or without the addition of concentrated milk.