He Siyu, Zhang Nan, Jing Pu
Research Center for Food Safety and Nutrition, Key Lab of Urban Agriculture (South), Bor S. Luh Food Safety Research Center, School of Agriculture & Biology, Shanghai Jiao Tong University Shanghai 200240 China
RSC Adv. 2019 Feb 5;9(8):4530-4538. doi: 10.1039/c8ra09329f. eCollection 2019 Jan 30.
Chlorophylls are the major pigments present in photosynthetic plants but their application in foods is limited due to their lack of solubility in aqueous media and their susceptibility to degradation during processing and storage. These problems might be overcome by the addition of sodium caseinate (NaCas) whose hydrophobic and hydrophilic groups may result in electrostatic and steric stabilization. In the present work, 1% and 3% (w/w) chlorophylls in NaCas dispersion or in ethanol (control) were prepared and their color stability under light treatment for 5 h and light-shed storage for 10 days was studied along with their interaction mechanism, using electrostatic, spectroscopic and morphological methodologies. Chlorophylls remained 58.72% and 53.84% in NaCas dispersions compared with the control (41.29% and 45.93%) after light treatment for low- and high-dose treatment, respectively, suggesting that NaCas improved the solubility and stability of the pigments. Additionally, 1% and 3% (w/w) chlorophylls in NaCas dispersion remained stable at 60.49% and 57.62% compared with the control (44.81% and 48.17%) for the 10 day storage during which the zeta-potential of the dispersions changed from -31.7 to -52.2 mV and from -36.7 to -56.2 mV with a well-defined diameter (∼221-245 nm). The data obtained from electron microscopy, together with the results of fluorescence spectroscopy, suggests that chlorophylls were entrapped in NaCas dispersions mainly hydrogen bonds.
叶绿素是光合植物中的主要色素，但由于它们在水性介质中缺乏溶解性，并且在加工和储存过程中易降解，因此其在食品中的应用受到限制。添加酪蛋白酸钠（NaCas）可能会克服这些问题，其疏水基团和亲水基团可能会导致静电和空间稳定作用。在本研究中，制备了1%和3%（w/w）叶绿素的NaCas分散液或乙醇溶液（对照），并使用静电、光谱和形态学方法研究了它们在5小时光照处理和10天光照储存下的颜色稳定性及其相互作用机制。低剂量和高剂量光照处理后，与对照（分别为41.29%和45.93%）相比，NaCas分散液中的叶绿素分别保留了58.72%和53.84%，这表明NaCas提高了色素的溶解性和稳定性。此外，在10天的储存期内，NaCas分散液中1%和3%（w/w）的叶绿素分别稳定在60.49%和57.62%，而对照分别为44.81%和48.17%，在此期间分散液的zeta电位从-31.7 mV变为-52.2 mV，从-36.7 mV变为-56.2 mV，粒径明确（约221-245 nm）。从电子显微镜获得的数据以及荧光光谱结果表明，叶绿素主要通过氢键包裹在NaCas分散液中。
