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The effects of temperature and soluble solids on degradation of anthocyanins in sour cherry concentrate were determined over temperature ranges (-18 to 37)"C and 50 to 80°C. Anthocyanin degradation could be modeled as a first-order rate reaction, with rates of 33.97 X lo-' .hr-1 (lS"Brix), 59.19 X lo-' .I@ (45"Brix) and 97.14 X lo+ .hr-' (71"Brix) at 80°C. Temperature dependence of reaction was described by the Arrhenius relationship. Activation energy for a solids content of U-71' Brix ranged from 16.37-19.14 kcal.mole-' with an average of 17.45 kcaI.mole-1

Heat inactivation kinetics of crude polyphenoloxidase (PPO) from six apple cultivars (Golden Delicious, Starking Delicious, Granny Smith; Gloster, Starcrimson and Amasya) were studied at three temperatures (68Њ, 73Њ and 78ЊC). PPO activity initially increased and then decreased with heat, following a first order kinetic model. Increase in activity indicated presence of latent PPO. Regression coefficients for the linear portions of inactivation curves were computed to determine inactivation parameters. Reaction data at 78ЊC revealed that PPO in Amasya was the least and Starking Delicious the most heat-stable. Rate constants for heat inactivation at 78ЊC ranged from 15.99-28.27 ⅐ 10 Ϫ2 min Ϫ1 . Activation energies varied between 54.7-77.2 kcal ⅐ mol Ϫ1 with z values of 7.1-10.0CЊ. PPO in apples was generally more heat-stable than PPO in most fruits.

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Black carrot juice concentrate was added to enhance the color of strawberry jams prepared from two locally grown cultivars, Osmanlı and Kara. Compared to other cultivars processed to jams, these two cultivars are lightly colored but very aromatic. Color and pigment stability of colored and noncolored (control) strawberry jams were studied during storage. The use of black carrot concentrate as a source of natural colorant stabilized the color of strawberry jam. The stabilization was more noticeable for jams prepared from Osmanlı cultivar. Monomeric anthocyanin degradation was fitted to a firstorder reaction model. Storage temperature had a strong influence on anthocyanin degradation. As the storage temperature increased, the stability of anthocyanins decreased significantly in both colored and noncolored jams. Parallel to decrease in monomeric anthocyanins, hue (h°) values of all jam samples increased throughout the storage. However, increase in h°values was much smaller in colored samples than in noncolored samples. High correlation was found between h°value and anthocyanin concentration at 22C (r = 0.910-0.978) and 37C (r = 0.931-0.981). PRACTICAL APPLICATIONSAn attractive and stable color of strawberry products is the indication of high quality for the consumers. However, the anthocyanins of strawberry 1 Corresponding

: Degradations were studied at different hydrogen peroxide (H2O2) concentrations (9.31 to 27.92 mmol. L1) over a range of 10° to 30 °C. Degradation of anthocyanins by H2O2 was described by first‐order function. Comparison of t1/2 values revealed that sour cherry anthocyanins were the most resistant to H2O2, followed by pomegranate and strawberry anthocyanins. Thus, the removal of residual H2O2 from the juice contact surfaces of aseptically packaged strawberry juices should be controlled more carefully to prevent anthocyanin degradation. Respective Ea values were between 9.4 to 11.1, 9.5 to 11.4, and 11.4 to 12.2 kcal.mol1; and Q10 values between 1.59 to 2.22, 1.62 to 2.05, and 1.76 to 2.36 for strawberry, sour cherry, and pomegranate anthocyanins.

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