title: Influence of storage temperature and time on the physicochemical and bioactive properties of roselle-fruit juice blends in plastic bottle.
abstract: Roselle-fruit juice blends were made from roselle extract and mango, papaya, and guava juices at the ratio of 80:20, 60:40, 40:60, and 20:80, % roselle: fruit juice, respectively. The blends were pasteurized at 82.5°C for 20 min and stored in 100 mL plastic bottles at 28 and 4°C for 6 months. The effects of storage time and temperature on physicochemical and bioactive properties were evaluated. Total soluble solids, pH, and reducing sugars increased significantly (P < 0.05) in some blends while titratable acidity decrease with increasing storage time. Vitamin C, total monomeric anthocyanins (TMA), total phenols (TPC), and antioxidant activity (ferric reducing ability of plasma, FRAP) in all roselle-fruit blends (40% roselle) decreased significantly (P < 0.05) at 28 and 4°C as storage progressed. Vitamin C in all roselle-fruit blends (40% roselle) decreased from 58-55% to 43-42% when stored at 28 and 4°C, respectively. TMA losses were 86-65% at 28°C and 75-53% at 4°C while TPC losses were 66-58% at 28°C and 51-22% at 4°C. Loss of antioxidant capacity (FRAP) was 18-46% at 28°C and 17-35% at 4°C. A principal component analysis (PCA) differentiated roselle-juice fruit blends into two clusters with two principle components PC1 and PC2, which explained 97 and 3% (blends stored at ambient temperature) and 96 and 4% (blends stored at refrigerated temperature) of the variation, respectively. PC1 differentiated roselle-guava juice blends which were characterized by vitamin C, TPC, FRAP, and pH, while PC2 from another cluster of roselle-mango and roselle-papaya juice blends and was characterized by TSS, RS, and color parameters (L* a* b*). However, TMA was the main variable with the highest effect on all roselle-fruit juice blends regardless of the storage time and temperature.
authors.affiliation: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences P.O. Box 5003, 1432, Åas, Norway ; Department of Food Science and Technology, Faculty of Agriculture, Sokoine University of Agriculture P.O. Box 3006, Morogoro, Tanzania.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Mgaya-Kilima
authors.affiliation: Department of Plant and Environmental Sciences, Norwegian University of Life Sciences P.O. Box 5003, 1432, Åas, Norway.
authors.forename: Siv Fagertun
authors.initials: SF
authors.lastname: Remberg
authors.affiliation: Department of Food Science and Technology, Faculty of Agriculture, Sokoine University of Agriculture P.O. Box 3006, Morogoro, Tanzania.
authors.forename: Bernard Elias
authors.initials: BE
authors.lastname: Chove
authors.affiliation: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences P.O. Box 5003, 1432, Åas, Norway.
authors.forename: Trude
authors.initials: T
authors.lastname: Wicklund
keywords: Anthocyanins; antioxidants; fruit juices; roselle