Evaluation of antimicrobial efficacy against spoilage microorganisms and impact on beverage color and turbidity of commercial preservatives derived from edible mushrooms

Abstract

The antimicrobial efficacy and the impact on sensory quality of preservatives from different natural sources can vary dramatically. This makes it challenging for manufacturers to incorporate natural preservatives in shelf-stable beverage formulation. This study compares new-to-market natural glycolipids (NG) derived from Dacryopinax spathularia and white button mushroom extract (WBME) containing chitosan from Agaricus bisporus. The antimicrobial efficacy was evaluated in a microbial spoilage challenge study wherein three-species suspensions of yeasts (Saccharomyces cerevisiae YG25, Zygosaccharomyces bailii DSM 70492 and Candida parapsilosis TD-0020), bacteria (Lactiplantibacillus plantarum DSM 12028, Lactococcus lactis DSM 20481 and Gluconobacter oxydans AC39) and fungal spores (Aspergillus brasiliensis DSM 1988, Byssochlamys nivea DSM 1824 and Penicillium roqueforti DSM 1079) were inoculated (100 CFU/mL per species) in acidified iced tea and juice drink. The preservatives were tested at concentrations within the range proposed by their respective manufacturers. They were also benchmarked against sodium benzoate (SB) and potassium sorbate (PS). Beverage samples were maintained at ambient temperature for 12 weeks and analyzed for microbial counts, pH, total soluble solids (TSS) at week 0, 1, 2, 4, 8 and 12. The impact on color and turbidity was assessed in a separate trial without spoilage microorganisms. Overall, NG was more effective and consistent than WBME and PS + SB in preventing spoilage by selected bacteria, yeasts, and molds in this study without significant impact on pH and TSS. WBME counterproductively supported the growth G. oxydans AC39 in acidified iced tea. WBME at high concentration appeared to reduce growth of S. cerevisiae YG25 and Z. bailii DSM 70492, but not C. parapsilosis TD-0020 whereas PS + SB could not inhibit any yeast species. WBME reduced mold spoilage for 4 weeks, after which the antifungal effects wore off. Finally, WBME and NG at high concentrations may cause separation, which increases beverage turbidity upon remixing and lightens the beverage color, especially if the beverage contains a significant amount of pectin.