Investigation of thermosonicated strawberry nectar quality during storage and kinetic modelling

The changes in ascorbic acid-(AA) content, hydroxymethylfurfural-(HMF) content, total color difference-(∆E*) and browning index-(BI) of optimally thermosonicated (59°C-455 J/g) cloudy strawberry nectar during storage (3 months at 4°C) were evaluated. Also, the data obtained were modelled. The initial AA content (104.86 mg/L) decreased ~99% after storage, while HMF level increased from 20.46 to 494.44 µg/L. The significant increases in BI-(0.45-0.56) and ∆E*-(5.21–11.23) were consistent with each other and over storage time. The changes in HMF content-(R2=0.849), BI-(R2=0.942) and ∆E* were best fitted to zero-order kinetic model, while decrease in AA content-(R2=0.9755) was described with the first-order kinetic model. The reaction rate constants of AA, HMF, ∆E* and BI were determined as 5.58x10-2 1/day, 4.34 mg/L.day, 6.40x10-2 mg/L.day and 14x10-2 mg/L.day, respectively. The highest correlation with the change in ∆E* was observed in AA-(R2=0.955) followed by BI-(R2=0.859). Therefore, the greatest effect on color might be caused by AA degradation.