Three different apple-carrot juice blends (60:40, 75:25 and 90:10, v/v) were prepared and treated with ultrasound with comparison to the conventional thermal pasteurization. Total aerobic viable count (TAC) were significantly lower in juice blends with lower pH (apple-carrot ratio of 90:10, v/v) than the blends with higher pH after one month storage at 4˚C. TAC were similar in ultrasound-treated and thermal pasteurized juice blends. Changes of turbidity of juice during storage followed the same pattern of TAC. Other juice quality parameters such as color, pH, titratable acid, total soluble solids, antioxidant capacity and beta-carotene did not change significantly during the storage period. The results suggest that ultrasound treatment has a potential to use as an alternative non-thermal technique for traditional thermal pasteurization process for maintaining the quality of beverages prepared from fruit and vegetable juices.

In order to examine the influence of delayed cooling on juice quality, seven and three days of delayed cooling were applied to 'Honeycrisp' and 'McIntosh' apples, respectively. After the delayed cooling treatment, apples were stored in refrigerated air (RA) and in three different controlled atmospheres (CA) for six months. Titratable acidity (TA) decreased over the storage period due to the delayed cooling treatment for both 'Honeycrisp' and 'McIntosh' apples. Lower TA was detected in RA-stored apples compared to CA-stored fruit. In addition, the lowest TA of the juice samples was detected when 'McIntosh' apples were stored in RA with no delayed cooling treatment.

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The high concentration of malic acid is responsible for the acidity and sourness in apple juice. Bio-conversion of malic acid to lactic acid through malolactic conversion (MC) in apple juice using Oenococcus oeni was investigated. When apple juice was inoculated with O. oeni (1 9 10 6 CFU mL À1 ), over 90% of malic acid was converted into lactic acid within 96 h at room temperature. When pH of apple juice was adjusted to 4.1 prior to inoculation, MC was completed within 60 h. MC was enhanced at a higher temperature (30°C) when compared with room temperature. The rate of MC was directly proportional to the number of bacteria added and MC was completed within 24 h at 1 9 10 9 CFU mL À1 initial cell density. MC occurred equally under aerobic and anaerobic conditions. The sensory analysis of partial MC-applied juice when compared against control revealed potential for use of MC for manufacture of low-acid apple juice. Characterisation of malolactic conversion by Oenococcus oeni J. Gao et al.Characterisation of malolactic conversion by Oenococcus oeni J. Gao et al.Characterisation of malolactic conversion by Oenococcus oeni J. Gao et al.Characterisation of malolactic conversion by Oenococcus oeni J. Gao et al.Characterisation of malolactic conversion by Oenococcus oeni J. Gao et al. Characterisation of malolactic conversion by Oenococcus oeni J. Gao et al.