108 Citrus oil Extract Potentiates the Antifungal Efficacy of Whey Protein Fermentate AgainstAspergillus Flavus in Semi-Moist pet Treats for Dogs

Abstract

Abstract Semi-moist pet treats contain moisture content ranging from 20-30% making them ideal for mold growth and mycotoxin production. To control spoilage, synthetic mold inhibitors, such as potassium sorbate, have been used. Unfortunately, consumers would prefer “natural” preservatives. Whey protein fermentate (WPF) is an efficient antifungal, albeit in large doses. Therefore, the objective of this study was to determine the effect of citrus extract (CX) to potentiate WPF against Aspergillus flavus in semi-moist pet treats. Nioutritionally complete semi-moist dog treats were produced with WPF alone [0.25%, 0.5% and 1.0% (w/w)] or in combination with CX [0.25% WPF+ 0.015% CX, 0.25% WFP+ 0.15% CX, 0.5% WPF+ 0.015% CX, 0.5% WFP+ 0.15% CX (w/w)]. The negative control (NC) contained no antifungal additive and the positive control had potassium sorbate (0.1% w/w). Treats were baked into 3cm x 3cm squares. Individual squares were inoculated with 0.1 mL of Aspergillus flavus (ATCC 204304) to achieve a final concentration of ~ 5.0 Log CFU/square. The inoculated squares were individually incubated at 250 C. Fungal analysis was performed at day 3, 6, 9, 12, 15, 18, 21, 24 and 28 by surface plating on Potato Dextrose Agar (PDA) followed by incubation at 250 C for 72h. The total log reductions were calculated by subtracting the initial inoculum with the colony counts on day 28. Log reductions of Aspergillus flavus (P< 0.05) were observed when WPF at 0.25% and 0.5% were added with 0.15% CX compared with when 0.015% CX was applied. All treatments were different from the NC (P< 0.05). Citrus extract at 0.15% potentiated the antifungal potency of WPF at 0.5% to give a similar log reduction (P >0.05) to WPF at 1.0% the treats. In conclusion, CX reduced the dose of WPF required to control Aspergillus flavus in semi-moist dog treats.