Impacts of preliminary isolation and enzymatic treatment on antioxidant activities of glycosylated whey protein isolate
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ORIGINAL PAPER
Impacts of preliminary isolation and enzymatic treatment on antioxidant activities of glycosylated whey protein isolate with inulin Ruijie Shi1 · Tianqi Li1 · Chunyan Wang1 · Haiying Yu1 · Wei Chen1 · Yu Wang1 · Abdul Qayum1 · Zhanmei Jiang1 · Juncai Hou1 Received: 1 January 2020 / Accepted: 19 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The effects of trichloroacetic acid (TCA), ethanol, ultrafiltration and enzymatic hydrolysis (pepsin and trypsin) on antioxidant activities of a glycosylated whey protein isolate (WPI)–inulin system were investigated. The antioxidant capacity of glycosylated WPI–inulin initially increased and then decreased after the TCA treatment. Correspondingly, the antioxidant activity of glycosylated WPI–inulin reached the highest level at a TCA concentration of 6% and an ethanol to sample ratio of 7:1. DPPH radical scavenging ability in fractions of glycosylated WPI–inulin > 50 kDa was enhanced about 24% after separation by ultrafiltration, compared with that of untreated glycosylated WPI–inulin. DPPH radical scavenging ability and ferrous reducing power of glycosylated WPI–inulin were about 32% and 15% higher than those of non-hydrolysis-treated glycosylated WPI–inulin after pepsin and trypsin hydrolysis. Chromatography revealed that more peptide molecules were produced by glycosylated WPI–inulin than by heated WPI. Therefore, TCA, ethanol, ultrafiltration, and enzymatic hydrolysis are effective ways to enhance the antioxidant activities of glycosylated WPI–inulin. Keywords Whey protein isolate · Inulin · Glycosylated · Preliminary isolation · Enzymatic treatment · Antioxidant activities
Introduction The various proteins retained in the supernatant after precipitation of casein in milk are called whey protein, which has high nutritional value [1]. Whey protein is extensively applied in the food industry, pharmacology, and biomedicine because of its functional properties and nutritional value [2]. Physical treatments, including ultrasound [3], heat [4], high pressure [5] and microwaves [6], chemical treatments, including acylation, phosphorylation, glycosylation and alcohol sulfidation [7, 8], and enzymatic treatments, Ruijie Shi and Tianqi Li are same contribution to this article. * Zhanmei Jiang [email protected] * Juncai Hou [email protected] 1
Key Laboratory of Dairy Science (Northeast Agricultural University), Ministry of Education, Harbin 150030, People’s Republic of China
including enzymatic hydrolysis and enzymatic cross-linking [9] are widely used to modify proteins and improve the functional properties. Inulin is a chain of non-digestible carbohydrates, composed of 31 β-d-fructofuranose and 1–2 glucopyranose residues. The fructose residues are connected with β-1, 2-bonds. Inulin has bioactive characteristics, including controlling blood lipids, lowering blood sugar, promoting mineral absorption, increasing intestinal bifidobacterial, preventing constipation and treating obesity [10]. Inulin not only improve
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