Optimization of Lactobacillus acidophilus La-5, Feta Cheese Starters and Salt Content in Iranian Ultrafiltered Soft Cheese Formula

Abstract

Aims: To optimize the process variables including: Lactobacillus acidophilus La-5, total starter (a mixture of mesophilic cheese starters (MCS) and thermophilic yoghurt starters (TYS), mesophilic cheese starter: thermophilic yoghurt starter (MCS:TYS) ratio and salt content in probiotic Iranian ultrafiltered soft cheese (IUSC). Methodology: In order to choose the best probiotic cheese formula with the highest Lactobacillus acidophilus La-5count, a total of eight samples with 20% total solids were produced using a small scale ultrafiltration system. Probiotic bacteria of Lactobacillus acidophilus La-5(0.1 and 0.3 %), total starters (1 and 2%), MCS: TYS ratio (8:2 and 7:3) and salt (NaCl) concentration (1 and 2%)by the help of Taguchi design were inoculated into cheeses and the viable cell counts of Lactobacillus acidophilus La-5enumeratedwithin 45 d of shelf lifeat5ºC, as well the multiple effects of process variables on probiotic count and colony morphologies of probiotic and starters evaluated. Results: The most suitable conditions for the highest Lactobacillus acidophilus La-5 stability were addition of 0.1% w/w Lactobacillus acidophilus La-5, 1% v/w total starter, MCS:TYS ratio of 8:2 and 1 % w/w salt content. The lowest and highest viable cell count of probiotic Lactobacillus acidophilus La-5in IUSC ranged from 6.41 to 7.92 CFU.g-1, respectively. The acidified (pH 5.2) MRS agar medium used for the differentiation of the colony morphology of Lactobacillus bulgaricus and Lactobacillus acidophilus La-5, anaerobically. In all of the cheeses except for cheese 3 and 6 which the La-5 survived to 6.95 and 6.41 log orders, respectively, Lactobacillus acidophilus La-5cell count survived to over107 CFU.g-1, when all the cheeses had the small amount of acetic acid taste with a creamy and soft texture. The MCS:TYS ratio of 8:2 and 0.1% initial dosage of Lactobacillus acidophilus La-5(PË‚0.05) affected the probiotic stability of Lactobacillus acidophilus La-5 in IUSC during shelf life, however the salt content (1 and 2%) and total starter (1 and 2%) did not significantly influence the Lactobacillus acidophilus La-5viability. Conclusion: This study showed that Iranian ultrafiltered soft cheese has a probiotic potential to have 107 CFU.g-1 viable cell count of Lactobacillus acidophilus La-5 strain, when process variables optimized and this progress will contribute to develop a healthier foods.