Journal
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
Volume 59, Issue 12, Pages 6776-6782Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jf201162g
Keywords
epsilon-polylysine; pectin; electrostatic complex; antifungals; antimicrobials; yeast; Zygosaccharomyces bailli; Saccharomyces cerevisiae; beverages
Funding
- National Institute of Food and Agriculture, U.S. Department of Agriculture
- Massachusetts Agricultural Experiment Station
- Department of Food Science
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epsilon-Polylysine (epsilon-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 epsilon-PL and anionic pectin. The nature of the complexes formed depended on the mass ratio of pectin to epsilon-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), similar to 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 epsilon-PL < 10 mu g/mL) at R(P-PL) <= 20 against two acid resistant spoilage yeasts: Zygosaccharomyces bailli and Saccharomyces cerevisiae. Finally, we showed that certain epsilon-PL pectin complexes (10 mu g/mL epsilon-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 (e-polylysine) can be improved by incorporating it within electrostatic complexes using a food-grade anionic biopolymer (pectin).
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