Optimization of Lactobacillus acidophilus La-5, Feta Cheese Starters and Salt Content in Iranian Ultrafiltered Soft Cheese Formula
Mohammad A. Nezami *
Department of Food Science and Technology, Science and Research Campus, Islamic Azad University, Tehran, Iran.
Mohammad R. Ehsani
Department of Food Science and Technology, Science and Research Campus, Islamic Azad University, Tehran, Iran.
Ali. Mohammadi-Sani
Department of Food Science and Technology, Quchan Branch, Islamic Azad University, Quchan, Iran.
Kianoush Khosravi-Darani
Research Department of Food Technology, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, P. O. Box: 19395-4741,Iran.
*Author to whom correspondence should be addressed.
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.
Keywords: Probiotic, starter, soft cheese, ultrafiltration, medium, viability, La-5, Iran