The growing demand for meat and dairy products necessitates the intensification of the production of feeds containing high-protein components. Yarrowia lipolytica biomass constitutes a rich source of easily digestible proteins and numerous vitamins, which makes it a valuable additive for both liquid and dry feeds. Unfortunately, the liquid products are susceptible to the growth of undesirable microflora. The aim of the presented research was to assess the possibility of using selected chemical substances to stabilize the high-protein liquid products acquired from Yarrowia lipolytica biomass. The research was designed with the use of a statistical method based on mixture designs. Microbiological stability was assessed using the results of culture tests aimed at calculating the total number of mesophilic bacteria, yeasts, molds, and bacteria from the coli and Salmonella sp. groups. Storage tests were performed at temperatures of 4 and 25 °C. Sodium benzoate, potassium sorbate and phosphoric acid were used as preservatives.
The use of preservatives resulted in a significant decrease in the numbers of bacteria during storage. After 30 days of storage, the total number of bacterial cells was 0.95±0.11 and 1.5±0.09 Log10 Cfu ml-1, respectively, for storage tests at temperatures of 4 and 25°C. A product with optimum preservative mixture composition, stored at 4°C, should contain 1297mg l-1 of sodium benzoate and 1203 mg l-1 of phosphoric acid. In the case of products stored at 25°C, the concentration of sodium benzoate and phosphoric acid should be 1307 mg l-1 and 1197 mg l-1, respectively.