The aim of this study was to determine the possibility of using Olkuska sheep milk for the production of ice cream with probiotics and prebiotics. The study examined the effect of the storage and type of bacteria used for the fermentation of ice cream mixes and partial replacement of inulin with apple fiber on the physicochemical properties, viability of probiotic cultures and organoleptic properties of sheep's milk ice cream stored at -22 °C for 21 days. The addition of apple fiber reduced the pH value of ice cream mixes before fermentation. In ice cream mixes and ice cream with apple fiber, the lactic acid content was higher by 0.1-0.2 g L-1 than in their equivalents with inulin only. These differences persisted during the storage of the ice cream. After fermentation of the ice mixes, the bacterial cell count ranged from 10.62 log cfu g-1 to 12.25 log cfu g-1. The freezing process reduced the population of probiotic bacteria cells in ice cream with inulin from 0.8 log cfu g-1 in ice cream with Lactobacillus acidophilus, 1.0 log cfu g-1 in ice cream with Lacticaseibacillus paracasei and 1.1 log cfu g-1 in ice cream with Lacticaseibacilluscasei. Freezing the varieties with apple fiber also resulted in a reduction of viable bacterial cells from 0.8 log cfu g-1 in ice cream with L. paracasei and Lb. acidophilus to 1 log cfu g-1 in ice cream with L. casei, compared to the results after fermentation. The highest percentage overrun was determined in ice cream with L. paracasei and Lb. acidophilus. Ice cream with L. casei was characterized by significantly lower overrun on the 7th and 21st days of storage. Although L. paracasei ice cream had the highest overrun, it did not cause a significant reduction in the probiotic population during storage. After seven days of storage, the first drop differed significantly depending on the type of bacteria used for fermentation of the mixture and the addition of apple fiber. L. casei ice cream had a longer first drop time than L. paracasei and Lb. acidophilus ice cream. Partial replacement of inulin with apple fiber resulted in a significant darkening of the color of ice cream mixes. Depending on the type of bacteria used for fermentation, the addition of apple fiber decreased the value of the L* parameter. Ice cream mixes and ice cream with inulin and apple fiber were characterized by a high proportion of yellow. Partial replacement of inulin with apple fiber reduced the hardness of ice cream compared to inulin-only ice cream. Moreover, the panelists found that ice cream with inulin was characterized by a sweeter taste than ice cream with apple fiber. Moreover, the addition of apple fiber favorably increased the flavor and aroma perception of the mango-passion fruit. Therefore, the milk of Olkuska sheep could be successfully used for the production of symbiotic dairy ice cream.
Keywords: Lacticaseibacillus; Lactobacillus; Olkuska breed; apple fiber; dairy ice cream; probiotics; sheep milk; symbiotic.