Objective: To assess the erosive potential of various soft drinks by measuring initial pH and titratable acidity (TA) and to evaluate enamel surface roughness using different exposure times. Materials and Methods: The initial pH of the soft drinks (group 1: Coca-Cola; group 2: orange juice; group 3: Cedevita; group 4: Guarana, and group 5: strawberry yoghurt) was measured using a pH meter, and TA was measured by titration with NaOH. Enamel samples (n = 96), cut from unerupted human third molars, were randomly assigned to 6 groups: experimental (groups 1-5) and control (filtered saliva). The samples were exposed to 50 ml of soft drinks for 15, 30 and 60 min, 3 times daily, during 10 days. Between immersions, the samples were kept in filtered saliva. Enamel surface roughness was measured by diamond stylus profilometer using the following roughness parameters: R_a, R_q, R_z, and R_y. Data were analyzed by one-way ANOVA, Tukey's post hoc and Student-Newman-Keuls post hoc tests. Results: The pH values of the soft drinks ranged from 2.52 (Guarana) to 4.21 (strawberry yoghurt). Orange juice had the highest TA, requiring 5.70 ml of NaOH to reach pH 7.0, whereas Coca-Cola required only 1.87 ml. Roughness parameters indicated that Coca-Cola had the strongest erosion potential during the 15 min of exposure, while Coca-Cola and orange juice were similar during 30- and 60-min exposures. There were no significant differences related to all exposure times between Guarana and Cedevita. Strawberry yoghurt did not erode the enamel surface regardless of the exposure time. Conclusion: All of the tested soft drinks except yoghurt were erosive. Erosion of the enamel surfaces exposed to Coca-Cola, orange juice, Cedevita, and Guarana was directly proportional to the exposure time.

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AbstractŽivković J., Zeković Z., Mujić I., Vidović S., Cvetković D., Lepojević Ž., Nikolić G., Trutić N. (2010): Scavenging capacity of superoxide radical and screening of antimicrobial activity of Castanea sativa Mill. extracts. Czech J. Food Sci., 28: 61-68.The superoxide radical scavenging and antimicrobial activity were examined of sweet chestnuts: seeds, peeled chestnut, brown seed coat, leaves, catkin, spiny burs, and chestnut bark as well as of Lovran's marrone leaves and grafted Italian marrone cultivar. Parts of chestnut were extracted under the same conditions with 50% ethanol as extractant and afterwards the dry extracts of the examined samples were obtained. The total phenolics and flavonoids contents were determined using standard spectrophotometrical methods. The capacity of the investigated extracts to remove radicals was evaluated by EPR method. The most efficient in scavenging• O 2 − radicals proved to be the extracts of leaves of grafted Italian marrone (RI = 86%) and of Lovran's marrone cultivar (RI = 80%). Catkin, leaves, chestnut bark, and spiny burs extracts demonstrated the highest antimicrobial activity. Very significant and significant correlations were established between the antimicrobial activity of extracts and • O 2 − radicals scavenging in all samples examined. The extracts of Castanea Sativa Mill. are important sources of components active in reducing the level of oxidative stress.

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