Purpose: The goal of this work was to evaluate the ability of sodium polyphosphate (SPP), a commonly used food additive, to enhance the antifungal efficacy of whole or fractionated PSE against Z. bailii in AJM. SPP is added to juices for various reasons, including metal sequestration and color stabilization. It is also known to possess antimicrobial properties. We hypothesized that SPP and PSE might show cooperative antimicrobial effects, allowing effective use of PSE at lower levels.
Methods: Z. bailii ATCC 60483 (105 CFU/ml) was incubated for up to 120 h in AJM or in AJM to which SPP (0.013% w/v), PSE (2 mg/ml), or combinations thereof were added. Both whole PSE and 9 individual HPLC-separated PSE fractions were tested. Growth suppression or lethality was determined for each treatment using a Bioscreen C automated turbidimeter and by plating onto YM agar.
Results: When combined with SPP, whole PSE and all 9 PSE fractions showed some antifungal activity against Z. bailii. Specifically, Fractions A, B, and D inhibited, but did not prevent, growth. The remaining fractions and whole PSE were more active, some fungicidal. Although whole PSE was ineffective alone, growth was completely inhibited when combined with SPP.
Significance: The cooperative antimicrobial action of SPP and PSE enabled complete suppression of Z. bailii growth in AJM, a real juice system. This approach represents a value-added natural antimicrobial solution for inhibition of spoilage yeasts in juices at lower levels of PSE.