Antifungal Activity of Protamine Salmine Hydrochloride and ε-Poly-l-Lysine in Actual Food Systems, Rice- or Wheat-Based Confectioneries

Abstract

Fungal contamination often occurs in confectioneries with high saccharide content during storage. Protamine salmine hydrochloride (PSH) and ε-poly-l-lysine (ε-PL) showed stable antifungal activities in the medium supplemented with 50% (w/v) sucrose, which pH shows around neutral, as a model of confectioneries. The antifungal activities of PSH and ε-PL have also shown synergy with sodium acetate. To confirm these antifungal activities into actual food systems, dumplings and steamed breads were used as rice- or wheat-based confectionery models. They substantiated practicable antifungal activities against confectionery pollution fungus in these models. The heat stability of both PSH and ε-PL was also indicated, and the impact on the taste or flavor of these confectioneries by addition of PSH and ε-PL were confirmed as less. The results proposed that both PSH and ε-PL are effective antifungal agents in actual foods with high saccharide contents such as confectioneries, at the neutral pH conditions. Practical Applications There are practically few natural antifungal agents used effectively to the actual foods at neutral pH, because many natural antifungal agents are lipophilic, or some of them show the antifungal effects only in the acidic condition even though they are hydrophilic. We screened the natural, hydrophilic antifungal agents effectual at neutral pH by using rice- or wheat-based confectioneries as models, which have actually problems of contamination of fungus. PSH and ε-PL were shown to be effectiveness in those models. They have been known to show strong antimicrobial effects at neutral pH, but they were thought to be necessary to add a large amount into foods to inhibit the growth of fungus. In this study, we demonstrated that the PSH and PL could use as effective antifungal agents with small amount at a high sugar concentration conditions around neutral pH. They were considered to suit for the application to the confectioneries.