Department of Food Science, University of Massachusetts , Amherst, Massachusetts 01003, USA.
J Agric Food Chem. 2011 Jun 22;59(12):6776-82. doi: 10.1021/jf201162g. Epub 2011 May 27.
ε-Polylysine (ε-PL) is a food-grade cationic antimicrobial that is highly effective against a wide range of food pathogens and spoilage organisms. However, its application within foods and beverages is currently limited because of its tendency to associate with anionic substances, thereby increasing product turbidity or forming sediments. In this study, we examined a potential means of overcoming these problems by forming electrostatic complexes between cationic ε-PL and anionic pectin. The nature of the complexes formed depended on the mass ratio of pectin to ε-PL (R(P-PL)), since this determined their electrical characteristics, aggregation stability, and antimicrobial efficacy. The electrical charge on the complexes went from positive to negative with increasing R(P-PL), with the point of zero charge being around R(P-PL) ∼ 8. Soluble complexes or stable colloidal dispersions were formed at low and high R(P-PL) levels, but insoluble complexes were formed at intermediate levels (i.e., 4 ≤ R(P-PL) ≤ 16). The complexes maintained good antimicrobial activity (minimum inhibitory concentration of ε-PL < 10 μg/mL) at R(P-PL) ≤ 20 against two acid resistant spoilage yeasts: Zygosaccharomyces bailli and Saccharomyces cerevisiae. Finally, we showed that certain ε-PL-pectin complexes (10 μg/mL ε-PL; R(P-PL) ≥ 2) could be incorporated into green tea beverages without adversely affecting their appearance or physical stability. This work has shown that the function of a cationic antimicrobial agent (ε-polylysine) can be improved by incorporating it within electrostatic complexes using a food-grade anionic biopolymer (pectin).
ε-聚赖氨酸（ε-PL）是一种食品级阳离子型抗菌剂，对广泛的食源性致病菌和腐败菌具有高效的抗菌作用。然而，由于其与阴离子物质结合的倾向，导致产品浑浊或形成沉淀物，因此其在食品和饮料中的应用目前受到限制。在本研究中，我们通过形成阳离子ε-PL 和阴离子果胶之间的静电复合物来研究克服这些问题的潜在方法。形成的复合物的性质取决于果胶与ε-PL 的质量比（R（P-PL）），因为这决定了它们的电学特性、聚集稳定性和抗菌功效。复合物的电荷从正到负随 R（P-PL）的增加而增加，零电荷点约为 R（P-PL）∼8。在低 R（P-PL）和高 R（P-PL）水平下形成可溶性复合物或稳定的胶体分散体，但在中间水平（即 4≤R（P-PL）≤16）下形成不溶性复合物。复合物在 R（P-PL）≤20 时对两种耐酸腐败酵母（Zygosaccharomyces bailli 和 Saccharomyces cerevisiae）保持良好的抗菌活性（ε-PL 的最小抑菌浓度<10μg/mL）。最后，我们表明，某些 ε-PL-果胶复合物（10μg/mL ε-PL；R（P-PL）≥2）可以掺入绿茶饮料中而不会对其外观或物理稳定性产生不利影响。这项工作表明，通过使用食品级阴离子生物聚合物（果胶）将阳离子抗菌剂（ε-聚赖氨酸）掺入静电复合物中，可以改善其功能。
