EFFECT OF FROZEN STORAGE ON THE QUALITY ATTRIBUTES OF FRESH AND CONCENTRATE CUT-BACK STRAWBERRY JUICES
Zagazig Journal of Agricultural Research
The present study was aimed to evaluate the effect of frozen storage at -18°C for 6 months on the quality attributes of the fresh and the concentrate Cut-back strawberry juices. The obtained results showed that the concentrate Cut-back strawberry juice was more acceptable by panelists. A significant decline in titratable acidity after freezing was observed in both types of strawberry juices; it decreased from 0.85 to 0.41 and from 0.98 to 0.49% for fresh strawberry juice and concentrate
... concentrate Cut-back juice, respectively. After 6 months of frozen storage similar tendency was observed for their vitamin C content having 9.45 and 29.23 mg/100ml for fresh and concentrate Cutback strawberry juice, respectively. The pH increased from 3.805 to 4.340 and from 3.604 to 4.252 for fresh strawberry juice and concentrate Cut-back juice, respectively. The concentrated Cut-back strawberry juice prior to freezing was found to be rich in ferulic acid, resorcinol and quercetin being 10.09, 0.24 and 731.98 ppm which were by respectively compared to fresh strawberry juice. Quercetin was the dominant compound, it was the only one that found in the two juices after 6 months of frozen storage. While, kaempherol was appeared after freezing for the two types of juices and showed gradual increase by increasing the duration of frozen storage. The Cut-back strawberry juice showed higher antioxidant activity and viscosity than fresh juice. A slight decrease in viscosity was observed for the two types of juice after storage at -18°C for 6 months. The colour was not stable during the frozen storage at -18°C, The colour values increased in fresh strawberry juice for L*,a*and b* from 12.73, 21.00 and 7.77 to 16.89, 25.94 and 9.91, respectively, but in Cut-back strawberry juice the value of L* was only increased from 13.23 to13.55 while, a* and b* values decreased from 25.75 and 8.11 to 22.68 and 7.00, respectively. From results, it could be concluded that the Cut-back strawberry juice had the best quality after 6 months of frozen storage.