engleski

Thermal degradation of anthocyanins in blackberry juice with addition of different sugars

Different factors influence anthocyanins stability among which temperature holds very important place. Prevention of thermal degradation of blackberry juice anthocyanins through sugar addition was investigated. Blackberry juice samples were prepared without (control) and with addition of 10% of different sugars (sucrose, fructose, glucose and trehalose), and heated at 50, 70 and 90°C for 1 and 2 hours. Since degradation of anthocyanins, over the time, followed first-order reaction model (R2 from 0.9650 to 0.9994), calculation of the reaction rate constant (k), half-lives (t1/2) and activation energy (Ea) was conducted. Initial anthocyanin content in blackberry juice was 202.91 mg/L. During heating at all investigated temperatures, degradation of anthocyanins occurred in higher or lesser extent (from 99.32 to 180.60 mg/L, depending on sugar and temperature). Addition of trehalose had the highest impact on anthocyanin stability during heating at all investigated temperatures and during both heating time. At 50°C all sugars caused prevention of anthocyanin degradation in comparison to control sample. However, samples with addition of glucose and trehalose, heated at 70 and 90°C, had higher, while with sucrose and fructose had lower anthocyanin content in comparison to control sample. k values ranged from 0.156 to 0.357 h-1, t1/2 from 1.94 to 5.98 h and Ea from 23.96 to 25.44 kJ/mol. Samples with trehalose addition had the lowest k values thus the highest t1/2 values at all investigated temperatures. In conclusion, careful formulation of foods, in our case sugar addition to blackberry juice, can minimise degradation of anthocyanins during heating.

anthocyanins; blackberry; sugars; heating

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