engleski

Effect of trehalose and sucrose addition on phenols, antioxidant activity and colour in apple juice

The objective of this study was to investigate influence of trehalose and sucrose addition (10 %) on phenol content, antioxidant activity and colour in apple juice during storage at room temperature and at 4 °C. Apple juice was obtained from Golden Delicious, Pink Lady and Fuji varieties. Apple juice without sugar addition was used as control sample. The highest phenol content had juice from Pink Lady variety, than Fuji and Golden Delicious (828.25, 796.01 and 749.67 GAE mg/L, respectively). During storage, degradation of phenols occurred at both storage temperature, but in higher extant at room temperature. Addition of sugars had high influence on phenol content in comparison to control sample. Samples with addition of sucrose had lower, while samples with addition of trehalose had higher phenol content in contrast to control sample. DPPH and ABTS methods were used for antioxidant activity determination. The lowest antioxidant activity had juice from Pink Lady variety (5.82 and 8.48 μmol TE/100 mL obtained with DPPH and ABTS method). Juice from Fuji and Golden Delicious variety had similar values of antioxidant activity regardless of used method (~7.3 and ~10.2 μmol TE/100 mL obtained with DPPH and ABTS method). During storage, increase of antioxidant activity occurred. This is probably due to formation of Maillard reaction products and/or chemical oxidation of phenols which can lead to increase of antioxidant activity since it was found that partially oxidised phenols can demonstrate higher antioxidant activity than unoxidised phenols. Calculation of colour change during storage showed that higher colour change was observed in samples stored at room temperature. In all samples when trehalose was added lower colour change was observed.

apple juice; phenol content; antioxidant activity; colour; storage

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