Survival of Lactobacillus acidophilus TISTR1338 and Lactobacillus casei TISTR390 in probiotic Gac ice cream

Ice cream is a kind of dairy products consumed all over the world and most popular among children and adults. however, ice cream available commercially is generally poor in natural antioxidants and vitamins. Thus, it is of interest to improve the nutritional values of ice cream using spiny bitter cucumber (Gac) which is a good source of lycopene and β-carotene along with probiotic bacteria. First, the survival of two different strains of probiotic bacteria including L. acidophilus TISTR1338 and L. casei TISTR390 in Gac ice cream was determined during the freezing and hardening steps and it was found that there was no significant difference in % survival of both probiotic bacteria (P>0.05) as L. acidophilus TISTR1338 and L. casei TISTR390 had % survival of 95.77 and 94.90 respectively. Then, survival promoting substances for probiotic bacteria in Gac ice cream including cryoprotectant as UnipectineTM RS 150 at 0.5%, 1.5%, and 2.5% and cells encapsulation with sodium alginate at 1%, 2%, and 3% on % survival of probiotic bacteria i.e. L. casei TISTR390 were investigated. It was found that cryoprotectant as Unipectine TM RS 150 at 0.5%, 1.5%, and 2.5% contributed % survival of 100.42, 99.94, and 100.37 respectively which were not significantly different from control (0%) with % survival of 99.95 (P>0.05). For cells encapsulation with sodium alginate at 1%, 2%, and 3%, it was found that the probiotic survival was 99.25, 99.06, and 99.11% respectively which were not significantly different from control (0%) with the % survival of 99.54 (P>0.05). Also, all five formulas of probiotic Gac ice cream were sensory evaluated for liking scores using nine points hedonic scales (1-9) with 50 untrained panelists and it was found that the attributes of appearance, color, odor, taste, texture, and overall liking had the significantly different scores (P≤0.05). Moreover, the probiotic Gac ice cream with cryoprotectant had overall liking score of 6.08 which was higher than the other formulas but was not significantly different from Gac ice cream (P>0.05). Furthermore, the survival of probiotic bacteria in Gac ice cream during storage at -20°C for 8 weeks was determined and it was found that when storage time increased, the numbers of probiotic bacteria and pH tended downwards while % acidity tended upwards. Finally, by the end of 8 th week, the probiotic survival numbers in Gac ice cream were significantly different (P≤0.05) as probiotic Gac ice cream with cryoprotectant had the highest survival of probiotic L. casei TISTR 390 with the number of 8.40 log cfu/g.