Abstract
This work is aimed at optimising the spray drying conditions of the phenolic extracts of purple mashua microencapsulated with octenyl succinic anhydride (OSA) Andean tuber starches. Purple mashua extracts were obtained and spray dried using native and OSA starches of yellow oca, pink oca, and yellow olluco (140°C, 4% starch). The powders obtained were analysed by encapsulation efficiency of anthocyanin (EE), total phenol content, and antioxidant capacity to select the best starch for optimisation purposes. OSA pink oca starch was selected because the obtained powder presented the highest EE. The spray drying conditions optimised were obtained using a central composite rotatable design (CCRD) and response surface methodology. The encapsulant proportion of OSA pink oca starch (2-12%) and the inlet drying temperature (IDT, 120-160°C) were used as factors of the design. The optimised spray drying condition was 160°C IDT and 2% encapsulant; this condition maximised the EE, total phenol content, antioxidant capacity, and solubility and minimised the water activity and hygroscopicity of the powder. The OSA pink oca starch could be used as an encapsulating agent of phenolic extracts because it can produce powder with high antioxidant capacity and high EE.
Highlights
Unconventional tubers such as mashua, oca, and olluco are cultivated in the Andean region of South America and have been used since Inca times
The native starches of Andean tubers used to encapsulate the purple mashua extracts (PME) show a variation in the total phenol content and antioxidant capacity after spray drying
High inlet drying temperature (IDT) helped the formation of a porous layer on the surface of the solid atomised particles, which in turn resulted in the increase of the wettability and dissolution, justifying the increase in solubility [24, 32]. These results indicate that the efficiency of anthocyanin (EE), total phenol content, and antioxidant capacity were high at high IDT and low encapsulant proportions
Summary
Unconventional tubers such as mashua, oca, and olluco are cultivated in the Andean region of South America and have been used since Inca times. Certain studies of native oca and olluco starches indicated that they have a good paste forming property, low gelatinisation temperature, and high elasticity of gels [1,2,3]. One of the commonly used modification methods is one using octenyl succinic anhydride (OSA), which involves the inclusion of OSA groups in the starch chains, subsequently producing esters that have hydrophilic and hydrophobic properties. Starches with these properties can be used for various processes including gel formation, encapsulation, and emulsification. Because of their aroma preservation properties and protection of hydrophilic and hydrophobic bioactive compounds, starches esterified by OSA are used to microencapsulate certain extracts such as eggplant [6], tomato concentrate [7], and sweet palm [8]
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