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Microencapsulation of Indian gooseberry juice using calcium-alginate crosslinking: Optimization, stability and application in yogurt
Dissertation Abstract:
Indian gooseberry (Phyllanthus emblica Linn) is a fruit renowned for its high phenolic and vitamin C content. However, its sour and astringent taste limits utilization. The objective of this study was to develop vitamin C- and phenolic-rich Indian gooseberry microbeads (IGM) using calcium-alginate ionic crosslinking microencapsulation technique. Plackett-Burman variable screening design, followed by a 5-level-4-factor Central Composite Design for response surface methodology analysis was utilized for optimization. The independent variables included calcium chloride (1-5% w/v), hardening time (15-75 min), sodium alginate concentration (0.45-1.05% w/v), and pH of juice (4.0-8.0). The optimization analysis to maximize both TPC and vitamin C encapsulation efficiency (38.85% and 41.63%, respectively) resulted in optimal parameters of 5% w/v calcium chloride, 30 min gelling time, 1% w/v sodium alginate, and pH 6.0. Methods such as the use of bigger nozzle sizes and using juice in CaCl2 solution, can improve encapsulation efficiency. The result of stability study of fresh IGM showed that TPC is stable over a moderate period in 35 days while vitamin C degrades at a faster rate, therefore freeze drying was recommended. A 91-day degradation study conducted at various storage temperatures (25°C, 35°C, and 45°C) confirmed that freeze-dried IGM are highly stable even with samples stored in higher temperatures. Incorporating freeze-dried IGM (1.5-3.0 g/serving) into freeze-dried yogurt powder were evaluated for their effect on bioactive components, chemical, and sensorial characteristic of rehydrated yogurt. Results showed that incorporation enhanced TPC, vitamin C, and DPPH radical scavenging activity while affecting chemical properties and consumer acceptability of yogurt. In terms of overall acceptability, overall flavor and texture, a recommended 1.5 g of IGM per serving ensures the health benefits without compromising the sensory quality of the product. The analysis of variance verified the significance of the factors investigated and their interactions with a confidence level of 95%.