Physicochemical Properties and Antimicrobial Efficacy of Electrostatic Complexes Based on Cationic ε-Polylysine and Anionic Pectin

• Published in: Journal of agricultural and food chemistry Vol. 59; no. 12; pp. 6776 - 6782
• Main Authors: Chang, Yuhua, McLandsborough, Lynne, McClements, David Julian
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 22.06.2011
• Subjects: Anti-Infective Agents - chemistry; Anti-Infective Agents - pharmacology; Biological and medical sciences; Food Chemistry/Biochemistry; Food industries; Food microbiology; Food Preservatives - chemistry; Food Preservatives - pharmacology; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; Pectins - chemistry; Pectins - pharmacology; Polylysine - chemistry; Polylysine - pharmacology; Static Electricity; Yeasts - drug effects; beverages; pectin; ε-polylysine; antifungals; antimicrobials; Zygosaccharomyces bailli; electrostatic complex; Saccharomyces cerevisiae; yeast; Ascomycota; Cationic complex; Yeast; Pectin; Food additive; Antimicrobial agent; Fungi; Gelling agent; Antifungal agent; Dietary fiber; Beverage; Polysaccharide; Physicochemical properties
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf201162g

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).