This study was conducted to determine the changes in anthocyanins and other polyphenols of black mulberry juice during clarification and pasteurization and their relation with antioxidant activity. Morover, thermal stabilities of anthocyanins and polyphenols in clarified black mulberry juice and concentrate were studied at 70.90 ʻC. Furthermore, the black mulberry juice concentrate obtained from clarified juice were stored at .20, 4, 10 and 20 ʻC and the changes in anthocyanins and other polyphenols, and the relation with antioxidant activity of black mulberry juice concentrates was monitored during storage. The kinetic parameters for the degradation of anthocyanins in black mulberry juice and concentrate during heating and storage were also determined. Finally, the antimicrobial activities of black mulberry juice against various fungi and bacteria were determined. Clarification of black mulberry juice included depectinization and then fining steps. During fining, fining agents including bentonite, gelatin and kieselsol were used. Overall, during fining, monomeric anthocyanin and polyphenol contents as well as antioxidant activity decreased significantly. While bentonite treatment resulted in 8% decrease in monomeric anthocyanin content of black mulberry juice, nonsignificant decrease in polyphenol content and antioxidant activity was observed. After gelatine and kieselsol treatment; anthocyanin content, polyphenol content and antioxidant activity decreased 3, 5 and 13%, respectively. Anthocyanin and organic acid profiles of black mulberry juice were idendified by HPLC. Major anthocyanins were cy-3-glu (51%), cy-3-rut (44%) and pg-3-glu (5%). Citric acid and malic acid were the major organic acids. Anthocyanin degradation was fitted to a first-order reaction model while polymeric color ratio was fitted to zero-order reaction model during the storage of black mulberry juice concentrates (66 ʻBx). As expected, the degradation of anthocyanins and formation of Brown color formation occurred at a much faster rate with increasing storage temperature. Half-life period for anthocyanin degradation in black mulberry juice concentrates was 100.3, 14.3, 7.2 and 1.7 months at .20, 4, 10 and 20 ʻC, respectively. The zeroorder reaction rate constants for polymeric color ratio were 0.0091, 0.0512, 0.0900 and 0.2738 % days.1 at .20, 4, 10 and 20 ʻC, respectively. There were no significant differences found in the polyphenol content of black mulberry juice concentrates during storage, however; antioxidant activity decreased by 8 to 19%. Results of this study showed that gelatin-kieselsol treatment resulted in the most important decrease in polyphenol contents of black mulberry juice during clarification. Also, there were no important changes in polyphenol contents of black mulberry juice concentrates during storage, but very fast color deterioration occurred in concentrate samples stored at 20 ʻC. Over 85% loss in monomeric anthocyanin content was observed in concentrates after 112 days of storage at 20 ʻC. Tempereture dependence of anthocyanins was determined by calculating activations energy (Ea) and Q10 values. Ea value for the degradation of anthocyanins in black mulberry juice concentrates was 70 kJ mol.1 at 4 ʻC to 20 ʻC, respectively. Since polyphenol contents of black mulberry juice concentrates during storage at 4 to 20 ʻC did not change significantly, Ea for the degradation of polyphenols in black mulberry juice concentrates was not be calculated. Blackmulberry juice and concentrate samples did not show antifungal activity against to the yeast including Candida spp. and Saccharomyces cerevisiae. On the contrary, almost all the samples showed antibacterial activity for Staphylococcus aureus but there were nonsignificant differences during processing steps. Although anthocyanins from black mulberry juice were much more stable than those from other sources, there were still significant losses during storage of blackmulberry juice concentrates. Therfeore, black mulberry juice concentrates should be kept at low temperatures, preferably subfreezing temperetures, to minimize anthocyanin degradation as well as formation of polymeric color. Key Words: Anthocyanins, Clarification, Color, Black Mulberry Juice, Concentrate, Stability.
Tez (Doktora)- Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Gıda Mühendisliği Anabilim Dalı, 2011.
Kaynakça var.
This study was conducted to determine the changes in anthocyanins and other polyphenols of black mulberry juice during clarification and pasteurization and their relation with antioxidant activity. Morover, thermal stabilities of anthocyanins and polyphenols in clarified black mulberry juice and concentrate were studied at 70.90 ʻC. Furthermore, the black mulberry juice concentrate obtained from clarified juice were stored at .20, 4, 10 and 20 ʻC and the changes in anthocyanins and other polyphenols, and the relation with antioxidant activity of black mulberry juice concentrates was monitored during storage. The kinetic parameters for the degradation of anthocyanins in black mulberry juice and concentrate during heating and storage were also determined. Finally, the antimicrobial activities of black mulberry juice against various fungi and bacteria were determined. Clarification of black mulberry juice included depectinization and then fining steps. During fining, fining agents including bentonite, gelatin and kieselsol were used. Overall, during fining, monomeric anthocyanin and polyphenol contents as well as antioxidant activity decreased significantly. While bentonite treatment resulted in 8% decrease in monomeric anthocyanin content of black mulberry juice, nonsignificant decrease in polyphenol content and antioxidant activity was observed. After gelatine and kieselsol treatment; anthocyanin content, polyphenol content and antioxidant activity decreased 3, 5 and 13%, respectively. Anthocyanin and organic acid profiles of black mulberry juice were idendified by HPLC. Major anthocyanins were cy-3-glu (51%), cy-3-rut (44%) and pg-3-glu (5%). Citric acid and malic acid were the major organic acids. Anthocyanin degradation was fitted to a first-order reaction model while polymeric color ratio was fitted to zero-order reaction model during the storage of black mulberry juice concentrates (66 ʻBx). As expected, the degradation of anthocyanins and formation of Brown color formation occurred at a much faster rate with increasing storage temperature. Half-life period for anthocyanin degradation in black mulberry juice concentrates was 100.3, 14.3, 7.2 and 1.7 months at .20, 4, 10 and 20 ʻC, respectively. The zeroorder reaction rate constants for polymeric color ratio were 0.0091, 0.0512, 0.0900 and 0.2738 % days.1 at .20, 4, 10 and 20 ʻC, respectively. There were no significant differences found in the polyphenol content of black mulberry juice concentrates during storage, however; antioxidant activity decreased by 8 to 19%. Results of this study showed that gelatin-kieselsol treatment resulted in the most important decrease in polyphenol contents of black mulberry juice during clarification. Also, there were no important changes in polyphenol contents of black mulberry juice concentrates during storage, but very fast color deterioration occurred in concentrate samples stored at 20 ʻC. Over 85% loss in monomeric anthocyanin content was observed in concentrates after 112 days of storage at 20 ʻC. Tempereture dependence of anthocyanins was determined by calculating activations energy (Ea) and Q10 values. Ea value for the degradation of anthocyanins in black mulberry juice concentrates was 70 kJ mol.1 at 4 ʻC to 20 ʻC, respectively. Since polyphenol contents of black mulberry juice concentrates during storage at 4 to 20 ʻC did not change significantly, Ea for the degradation of polyphenols in black mulberry juice concentrates was not be calculated. Blackmulberry juice and concentrate samples did not show antifungal activity against to the yeast including Candida spp. and Saccharomyces cerevisiae. On the contrary, almost all the samples showed antibacterial activity for Staphylococcus aureus but there were nonsignificant differences during processing steps. Although anthocyanins from black mulberry juice were much more stable than those from other sources, there were still significant losses during storage of blackmulberry juice concentrates. Therfeore, black mulberry juice concentrates should be kept at low temperatures, preferably subfreezing temperetures, to minimize anthocyanin degradation as well as formation of polymeric color. Key Words: Anthocyanins, Clarification, Color, Black Mulberry Juice, Concentrate, Stability.