Optimising the Polyphenolic Content and Antioxidant Activity of Green Rooibos (Aspalathus linearis) Using Beta-Cyclodextrin Assisted Extraction.

Antioxidant activity associated with green rooibos infusions is attributed to the activity of polyphenols, particularly aspalathin and nothofagin. This study aimed to optimise ß-cyclodextrin (ß-CD)-assisted extraction of crude green rooibos (CGRE) via total polyphenolic content (TPC) and antioxidant activity assays. Response surface methodology (RSM) permitted optimisation of ß-CD concentration (0−15 mM), temperature (40−90 °C) and time (15−60 min). Optimal extraction conditions were: 15 mM ß-CD: 40 °C: 60 min with a desirability of 0.985 yielding TPC of 398.25 mg GAE·g−1, metal chelation (MTC) of 93%, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging of 1689.7 µmol TE·g−1, ferric reducing antioxidant power (FRAP) of 2097.53 µmol AAE·g−1 and oxygen radical absorbance capacity (ORAC) of 11,162.82 TE·g−1. Aspalathin, hyperoside and orientin were the major flavonoids, with quercetin, luteolin and chrysoeriol detected in trace quantities. Differences (p < 0.05) between aqueous and ß-CD assisted CGRE was only observed for aspalathin reporting the highest content of 172.25 mg·g−1 of dry matter for extracts produced at optimal extraction conditions. Positive, strong correlations between TPC and antioxidant assays were observed and exhibited regression coefficient (R2) between 0.929−0.978 at p < 0.001. These results demonstrated the capacity of ß-CD in increasing polyphenol content of green rooibos.

Degradation of ß-carotene in amorphous polymer matrices. Effect of water sorption properties and physical state.

BACKGROUND: The use of encapsulation in amorphous matrices of carbohydrate and/or polymer formed during dehydration processes to enhance the stability and retention of labile compounds is increasing in the food and pharmaceutical industries. Efforts to improve encapsulating properties have been made using mixtures of carbohydrates with proteins or gums in different proportions. The objective of the present work was to study the stability of encapsulated ß-carotene and its degradation kinetics in maltodextrin/gum arabic and maltodextrin/gelatin matrices in relation to the physical properties and state of the dehydrated matrix. RESULTS: The degradation of ß-carotene followed a first-order kinetic model of fractional retention for all encapsulating matrices. The Guggenheim-Anderson-de Boer (GAB) model was adequate to describe the sorption isotherms of the studied systems. ß-Carotene losses were observed mainly at relative humidities (RHs) above the glass transition temperatures (T(g) ) of the corresponding systems, where the matrices were fully plasticised and collapsed (75 and 92% RH). At these high RHs the best ß-carotene retention was obtained in the system containing gum arabic. CONCLUSION: The results showed that pigment degradation was determined by the physical state of the matrix, related to the degree of collapse. They represent a contribution to the knowledge of physical factors that affect the retention kinetics of labile biomolecules encapsulated in dehydrated matrices.