Browsing by Author "Remberg, S. F."

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Inﬂuence of storage temperature and time on the physicochemical and bioactive properties of roselle-fruit juice blends in plastic bottle
(Food Science & Nutrition, 2014) Mgaya-Kilima, B.; Remberg, S. F.; Chove, B. E.; Wicklund, T.
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.
Physio-chemical, mineral composition and antioxidant properties of roselle (hibiscus sabdariffa l.) Extract blended with tropical fruit juice
(Ajfand, 2014) Mgaya, K. B.; Remberg, S. F.; Chove, B. E.; Wicklund, T.
Different varieties of fruit juices and beverages are available globally and there has been an increased consumption of fruit juices and beverages due to consumer awareness of nutritional and health benefits. Juice extracts are produced from various parts of plants including leaves, fruits and flowers. Hibiscus sabdiriffa (Roselle) is one such plant whose flowers are used to prepare juices. The roselle extract has a unique red colour, good flavour, low sugar and high acidic content. The acidity makes the juice sour hence the need for addition of sweetening products. A study was conducted on the formulation of roselle extract-tropical fruit blends aimed at establishing its physiochemical, mineral and antioxidant composition. Dried roselle calyces at a ratio of 1:10 (dried roselle calyces: water) were extracted at 50oC for 30 minutes. The roselle extracts were blended at various proportions of fruit (mango, papaya and guava) juices. Physiochemical, mineral composition and antioxidant properties were evaluated in all the roselle fruit juice blends The results for all rosellefruit blends (80% roselle to 20% roselle) showed that pH ranged between (2.35-3.32), total soluble solids (5.6-10.6o Brix), titratable acidity (1.28-1.92 %), reducing sugars (2.95-5.55) mg/100g,. Calcium (555.3-23.4 mg/100g DM), Magnesium (213.8-11.5 mg/100g DM), Phosphorus (39.8-9.0 mg/100g DM), Sodium (2.3-5.47 mg/100g DM), Zinc (5.85-0.69 mg/100g DM), Iron (29.5-1.36 mg/100g DM), monomeric anthocyanin (493.5-118.2 mg cyanidin-3-glucoside/100g), vitamin C (40.0-86.5 mg/100g), total phenol (54.6-10.8 mg gallic acid/ 100 g) and antioxidant activity (1.80-1.37 mmol/L). Blending of tropical fruit juices with roselle extract have improved mineral composition and antioxidant properties of fruit juices as roselle is a good source of calcium, magnesium and iron. Antioxidants acts as free radical scavengers inhibit lipid peroxidation and other free radical mediated process, therefore, consumption of roselle-fruit juices with high anthocyanin will protect human body from several diseases attributed to the reactions of free radicals.