Abstract
This study was conducted to extract and encapsulate anthocyanins from black rice bran using chitosan-alginate nanoparticles. Ten black rice varieties were screened for the anthocyanin content and the variety with the highest anthocyanins was used for the encapsulation. The anthocyanins were extracted by defatting the bran with n-hexane and soaking it with 85% acidified ethanol. The crude anthocyanin extract (CAE) was freeze-dried at -110°C for 48 h and then encapsulated in chitosan-alginate nanoparticles using two processes: ionic pre-gelation and polyelectrolyte complex formation. The mass ratio of chitosan and alginate polymers used in this study was 100:10. The treatments applied were as follows: T0-0 mg CAE, T1-10 mg CAE, T2-20 mg CAE, and T3-30 mg CAE. The resulting capsules were characterized in terms of chemical properties, surface morphology, particle size, polydispersive index, encapsulation efficiency, and 2, 2-diphenyl-1-picrylhydrazyl radical scavenging activity. Screening of rice samples indicated that Ominio bran had the highest anthocyanin content (36.11 mg/g). Anthocyanins were successfully encapsulated in the matrix as shown by the Scanning Electron Microscopy images and Fourier Transform Infrared spectra of the anthocyanin-loaded chitosan-alginate nanoparticles. Among the different concentrations of CAE, T3 had the highest encapsulation efficiency (68.9%) and antioxidant scavenging activity (38.3%) while T1 and T2 had the lowest. Ascending particle size was observed for T0 (358.5 nm), T3 (467.9 nm), T1 (572.3 nm), and T2 (635.9 nm). All anthocyanin-loaded capsules were found to be of nano-size (<1000 nm). The study concluded that chitosan-alginate nanoparticles can be a good encapsulating material for anthocyanin.
Highlights
The Philippines being one of the top rice producers in the world produced about 18.15 million metric tons of paddy rice in 2015 (Philippine Statistics Authority, 2016)
The result confirms our previous findings on the screening of rice bran with maximum health promoting properties wherein Ominio bran had the highest anthocyanin content among the black rice varieties (Bulatao et al, 2016)
Ominio bran was selected as sample for the preparation of crude anthocyanin extract (CAE) for encapsulation
Summary
The Philippines being one of the top rice producers in the world produced about 18.15 million metric tons of paddy rice in 2015 (Philippine Statistics Authority, 2016) This huge amount of paddy rice contributed significantly in the generation of agricultural by-products such as rice bran. Anthocyanins are known to exhibit antimicrobial, anticancer, and anti-hyperglycemic properties (Andersen & Jordheim, 2006). These compounds are very promising as ingredient for functional and pharmaceutical products, but they have limited use due to their low stability under varying environmental conditions (pH, light, oxygen, and heat) and high reactivity with other compounds in the food matrix (Cavalcanti et al, 2011; Robert & Fredes, 2015)
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