Table 2 summarizes the kinetic parameters obtained for each temperature evaluated. The kinetic rate constants increased with increasing temperature, ranging from 5.9 to 19.7 × 10−3 min−1. Kirca and Xu (2007) studied anthocyanin stability of black carrots at various solid contents (11, 30, 45 and 64 °Brix) and pHs (4.3 and 6.0) during heating at 70–90 °C. Monomeric anthocyanin degradation fit a first-order reaction model and the rate constants ranged from 0.68 to 4.98 × 10−3 min−1. Wang and Xu

(2007) evaluated thermal stability of anthocyanins in blackberry juice over the temperature range 60–90 °C. Results indicate that the thermal degradation of anthocyanins also followed first-order reaction kinetics with Tariquidar chemical structure rate constants ranging between 0.69 and 3.94 × 10−3 min−1. Aurelio, Edgardo, and Navarro-Galindo (2008) studied the degradation kinetics of anthocyanins in a Roselle infusion (Hibiscus sabdariffa L.) in temperatures ranging from 60 to 100 °C and the rate constants, obtained from first-order reaction model, were between 0.6 and 7.9 × 10−3 min−1. Clearly, the literature check details values of rate constants for anthocyanin degradation in the above food products are smaller than the results found for acerola pulp.

According to de Rosso and Mercadante (2007), the presence of high concentrations of ascorbic acid is the main cause of the low stability of the acerola anthocyanins. Studies have shown that the presence of ascorbic acid has negative influence on anthocyanin stability, leading to a mutual degradation of these compounds (de Rosso and Mercadante, 2007, Garzón and Wrolstad, 2002 and Poei-Langston and Wrolstad, 1981). Three different mechanisms have been proposed to explain the degradation of anthocyanins in the presence of ascorbic acid. The first

5-Fluoracil solubility dmso one suggests that hydrogen peroxide formed through oxidation of ascorbic acid oxidizes anthocyanin pigments (Sondheimer & Kertesz, 1948). The second mechanism, proposed by Jurd (1972), consists of direct condensation of ascorbic acid on the carbon 4 of the anthocyanin molecule, causing loss of both compounds. On the other hand, according to Iacobucci and Sweeny (1983), anthocyanin degradation in the presence of ascorbic acid occurs due to oxidative cleavage of the pyrilium ring by a free radical mechanism in which the ascorbic acid acts as a molecular oxygen activator, producing free radicals. It can also be observed from Table 2 that there was no significant difference between the rate constants of the ohmic and the conventional heating at the same temperature. To the best of our knowledge, no study regarding degradation of anthocyanins during ohmic heating is available in the literature. Comparative studies of the heating technologies were conducted evaluating the degradation of ascorbic acid.