The complex of casein with pectin can improve the solubility and stability of casein. However, it is easily affected by the degree of esterification of pectin. Therefore, the effects of different degrees of esterification of pectins on the interaction and the properties of complexes were investigated by a combined experimental and computational study. Results showed that the optimum mass ratio of casein to pectin with 36.1%, 41.6%, 47.8%, and 67.9% degrees of esterification was 4∶1, 4∶1, 4∶1, and 5∶1, respectively. When the degree of esterification increased from 36.1% to 67.9%, the solubility of casein at pH 4.6 increased by 10.44%. The results of molecular dynamics simulation showed that the complex of β-casein with pectin with 67.9% degree of esterification had a relatively low root mean square deviation (0.36 nm) and binding energy (-1.91x106 kJ/mol), indicating relatively high stability. Electrostatic interaction played a major role in the combination of β-casein and pectin and was beneficial in reducing the turbidity of the casein-pectin complex at pH 4.6. The results of infrared spectrum analysis showed that amino acid residues in casein interacted with ester carbonyl and carboxyl groups in pectin. This study demonstrated the effect of the degree of esterification of pectin on the property of the casein-pectin complex by experiment and theoretical calculation, which provided a reference to improve the utilization of casein and the property of the casein-pectin complex.
[1] 张晶晶, 李艾黎, 程金菊.美拉德反应修饰的酪蛋白递送生物活性物质的应用研究进展[J].食品科学, 2022, 43(23): 316-325.
ZHANG J J, LI A L, CHENG J J.Review of the application of Maillard reaction modified-casein in the delivery of bioactive substances[J].Food Science, 2022, 43(23): 316-325.
[2] DONG X Y, DU S S, DENG Q C, et al.Study on the antioxidant activity and emulsifying properties of flaxseed gum-whey protein isolate conjugates prepared by Maillard reaction[J].International Journal of Biological Macromolecules, 2019, 153:1157-1164.
[3] LIU X Y, QIN X L, WANG Y H, et al.Physicochemical properties and formation mechanism of whey protein isolate-sodium alginate complexes:Experimental and computational study[J].Food Hydrocolloids, 2022, 131:107786.
[4] LAN Y, CHEN B C, RAO J J.Pea protein isolate-high methoxyl pectin soluble complexes for improving pea protein functionality:Effect of pH, biopolymer ratio and concentrations[J].Food Hydrocolloids, 2018, 80:245-253.
[5] LI X Y, FANG Y P, AL-ASSAF S, et al.Complexation of bovine serum albumin and sugar beet pectin:Structural transitions and phase diagram[J].Langmuir, 2012, 28(27):10164-10176.
[6] ARCHUT A, DRUSCH S, KASTNER H.Complex coacervation of pea protein and pectin:Effect of degree and pattern of free carboxyl groups on biopolymer interaction[J].Food Hydrocolloids, 2022, 133:107884.
[7] WARNAKULASURIYA S, PILLAI P K S, STONE A K, et al.Effect of the degree of esterification and blockiness on the complex coacervation of pea protein isolate and commercial pectic polysaccharides[J].Food Chemistry, 2018, 264:180-188.
[8] CHENG L L, ZHU X, HAMAKER B R, et al.Complexation process of amylose under different concentrations of linoleic acid using molecular dynamics simulation[J].Carbohydrate Polymers, 2019, 216:157-166.
[9] ZHAO R C, QIN X L, ZHONG J F.Interaction between curcumin and β-casein:Multi-spectroscopic and molecular dynamics simulation methods[J].Molecules, 2021, 26:165092.
[10] LI Y, ZHANG X Y, SUN N, et al.Formation and evaluation of casein-gum arabic coacervates via pH-dependent complexation using fast acidification[J].International Journal of Biological Macromolecules, 2018, 120:783-788.
[11] LIU S H, LOW N H, NICKERSON M T.Effect of pH, salt, and biopolymer ratio on the formation of pea protein isolate-gum arabic complexes[J].Journal of Agricultural and Food Chemistry, 2009, 57(4):1521-1526.
[12] 王鲁慧, 肖军霞, 徐同成, 等.湿热条件下大豆分离蛋白与葡萄糖、麦芽糖的美拉德反应[J].食品科学, 2018, 39(16):19-26.
WANG L H, XIAO J X, XU T C, et al.Maillard reaction of soybean protein isolate with glucose and maltose under wet heating conditions[J].Food Science, 2018, 39(16):19-26.
[13] KAUR J, KATOPO L, HUNG A.Combined spectroscopic, molecular docking and quantum mechanics study of β-casein and p-coumaric acid interactions following thermal treatment[J].2018, 252:163-170.
[14] ŠALI A, BLUNDELL T L.Comparative protein modelling by satisfaction of spatial restraints[J].Journal of Molecular Biology, 1993, 234(3):779-815.
[15] FERREIRA-LAZARTE A, MORENO F J, CUEVA C, et al.Behaviour of citrus pectin during its gastrointestinal digestion and fermentation in a dynamic simulator (simgi®)[J].Carbohydrate Polymers, 2019, 207:382-390.
[16] FERNANDES A, BRÁS N F, MATEUS N, et al.Understanding the molecular mechanism of anthocyanin binding to pectin[J].Langmuir, 2014, 30(28):8516-8527.
[17] VORAGEN A G J, COENEN G J, VERHOEF R P, et al.Pectin, a versatile polysaccharide present in plant cell walls[J].Structural Chemistry, 2009, 20(2):263-275.
[18] KRIEGER E, VRIEND G.New ways to boost molecular dynamics simulations[J].Journal of Computational Chemistry, 2015, 36(13):996-1007.
[19] GAN N, SUN Q M, TANG P X, et al.Determination of interactions between human serum albumin and niraparib through multi-spectroscopic and computational methods[J].Spectrochimica Acta Part A:Molecular and Biomolecular Spectroscopy, 2019, 206:126-134.
[20] PILLAI P K S, STONE A K, GUO Q, et al.Effect of alkaline de-esterified pectin on the complex coacervation with pea protein isolate under different mixing conditions[J].Food Chemistry, 2019, 284(30):227-235.
[21] AZARIKIA F, ABBASI S.Mechanism of soluble complex formation of milk proteins with native gums (tragacanth and Persian gum)[J].Food Hydrocolloids, 2016, 59:35-44.
[22] KLASSEN D R, ELMER C M, NICKERSON M T.Associative phase separation involving canola protein isolate with both sulphated and carboxylated polysaccharides[J].Food Chemistry, 2011, 126(3):1094-1101.
[23] ARYEE F N A, NICKERSON M T.Formation of electrostatic complexes involving mixtures of lentil protein isolates and gum Arabic polysaccharides[J].Food Research International, 2012, 48(2):520-527.
[24] 刘祥雨, 覃小丽, 钟金锋.采用分子动力学模拟研究温度对乳球蛋白稳定性的影响[J].食品与发酵工业, 2020, 46(7):89-96.
LIU X Y, QIN X L, ZHONG J F.Effect of temperature on the stability of lactoglobulin:A molecular dynamics simulation[J].Food and Fermentation Industries, 2020, 46(7):89-96.
[25] CHEN F P, LI B S, TANG C H.Nano complexation between curcumin and soy protein isolate:Influence on curcumin stability/bioaccessibility and in vitro protein digestibility[J].Journal of Agricultural and Food Chemistry, 2015, 63(13):3559-3569.
[26] NIU F G, DONG Y T, SHEN F, et al.Phase separation behavior and structural analysis of ovalbumin-gum arabic complex coacervation[J].Food Hydrocolloids, 2015, 43:1-7.
[27] WANG C N, WANG H, SUN X M, et al.Heat-induced interactions between whey protein and inulin and changes in physicochemical and antioxidative properties of the complexes[J].International Journal of Molecular Sciences, 2019, 20(17):4089.
