Physicochemical and functional properties of dietary fiber from Nannochloropsis oceanica: A comparison of alkaline and ultrasonic-assisted alkaline extractions

• Published in: Food science & technology Vol. 133; p. 110080
• Main Authors: Ding, Qingzhi, Li, Zhikun, Wu, Wei, Su, Yingying, Sun, Nianzhen, Luo, Lin, Ma, Haile, He, Ronghai
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2020
• Subjects: adsorption; Adsorption properties; alpha-amylase; ammonium; cholesterol; Dietary fiber; food composition; functional foods; glucose; hydrophilicity; Nannochloropsis; Nannochloropsis oceanica; nitrites; oils; Physicochemical properties; sodium cholate; solubility; triacylglycerol lipase; Ultrasonic-assisted alkaline extraction; Adsorption properties; Nannochloropsis oceanica; Dietary fiber; Ultrasonic-assisted alkaline extraction; Physicochemical properties
• ISSN: 0023-6438; 1096-1127
• DOI: 10.1016/j.lwt.2020.110080

In this study, the process parameters were optimized for extracting soluble dietary fiber (U-SDF) from the residue of Nannochloropsis oceanica (NR) by ultrasonic-assisted alkaline extraction (UAE). The structure, physicochemical and functional properties of U-SDF, insoluble dietary fiber (U-IDF) extracted by UAE, and soluble dietary fiber (A-SDF) extracted by alkaline extraction were investigated. The results showed that the U-SDF yield (17.50 ± 0.26%) under optimal conditions increased by 150.72% compared with A-SDF. U-SDF exposed more hydrophilic groups (such as -OH) and more loose structure in comparison with A-SDF and U-IDF. In addition, U-SDF had higher solubility, adsorption capacity of cholesterol, sodium cholate, ammonium nitrite and glucose, and digestive enzyme (α-amylase and pancreatic lipase) inhibition ability in vitro than A-SDF and U-IDF. However, U-SDF had lower water holding capacity, water swelling capacity, and oil holding capacity than U-IDF. Thus it was indicated that DF from NR was a potentially available functional food ingredient, which will increase the added value of N. oceanica. •Nannochloropsis oceanica residue is a good potential source of DF.•Ultrasonic-assisted alkaline extraction was an effective method for extracting SDF from the residue of N. oceanica.•U-SDF exposed more hydrophilic groups (such as –OH) and surface area than A-SDF and U-IDF.•U-SDF also had higher solubility, adsorption capacity, digestive enzyme inhibition ability in vitro than A-SDF.•U-SDF had lower water holding capacity, water swelling capacity, and oil holding capacity than U-IDF.