Abstract
A blueberry anthocyanin extract was obtained from Brightwell blueberry fruits cultivated in eastern China and the extraction and purification conditions were optimized. The components of the anthocyanin extract were identified using ultra-performance liquid chromatography-electrospray ionization interface-mass spectrometer. The antioxidant and antibacterial activities of the blueberry fruit supernatant (BFS), blueberry anthocyanin crude extract (BCE), and blueberry anthocyanin rich extract (BRE) were evaluated. The extraction yield was 1.79 ± 0.0014 mg/g under the following optimal conditions: 1:20 solid-to-liquid ratio (v/w), 24 h, 34 °C, and 90% ethanol containing 0.21% (v/v) hydrochloric acid. With regard to purification, anthocyanin purity increased 19.1-fold. Nine fractions were identified as the glycosides of delphinidin, cyanidin, petunidin, and malvidin. The biological activities of the blueberry anthocyanin extract were improved through extraction and purification. Compared with BFS and BCE, BRE had a higher DPPH radical scavenging activity (EC50 = 0.51 mg/mL), ABTS antioxidant capacity (EC50 = 0.32 mg/mL), and oxygen radical absorbance capacity (0.43 mmol Trolox/g). Furthermore, BRE (2 mg/mL) showed a maximum of 84.64 ± 0.35% reduction in the biofilm biomass of Listeria monocytogenes and the inhibition zone given by BRE against Escherichia coli was 16.04 ± 0.38 mm. BRE showed the highest antioxidant capacities and obvious antibacterial effects against food-related microorganisms than the other samples. Therefore, BRE can be used as a natural antioxidant and antibacterial agent and has potential health advantages and food industry applications.
Highlights
Chemical preservatives are often added to improve microbiological food safety
HPLC-grade acetonitrile, methanol, and formic acid were purchased from Merck Chemicals Co., Ltd. (Darmstadt, Germany). 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 2,2′-Azo-bis(2-amidinopropane) dihydrochloride (AAPH), 6-hydroxy-2,5,8tetramethylchroman-2-carboxylic acid (Trolox), and fluorescein disodium salt were purchased from SigmaAldrich
Measurement of antioxidant activities Freeze-dried blueberry anthocyanin rich extract (BRE), blueberry anthocyanin crude extract (BCE), and blueberry fruit supernatant (BFS) dissolved in deionized water at the different concentrations were used in the antioxidant assays
Summary
Chemical preservatives are often added to improve microbiological food safety. Consumers, on the other hand, are becoming increasingly concerned about the possible dangers of chemical preservatives and want meals that are free of them. The blueberry anthocyanin was extracted from smashed berries by using a mixture of ethanol, water, and HCl at 150 rpm. A Box Behnken design was used in investigating the effects of independent variables, namely, ethanol concentration (A), HCl dose (B), extraction time (C), extraction temperature (D), and solid-to-liquid ratio (E) on the yield of blueberry anthocyanin extracts.
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