Effect of oxygen on batch yogurt cultures

• Published in: World journal of microbiology & biotechnology Vol. 18; no. 4; pp. 361 - 365
• Main Authors: BESHKOVA, D. M, SIMOVA, E. D, FRENGOVA, G. I, SIMOV, Zh. I, SPASOV, Z. N
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01-01-2002
• Subjects: Biological and medical sciences; Food industries; Fundamental and applied biological sciences. Psychology; Milk and cheese industries. Ice creams; Mixed microorganism culture; Dairy product; Environmental factor; Yogurt; Streptococcaceae; Lactobacillus delbrueckii subsp. bulgaricus; Batchwise; Streptococcus salivarius subsp. thermophilus; Bacteria; Lactobacillaceae; Micrococcales; Dissolved oxygen; Milk
• ISSN: 0959-3993; 1573-0972

A yogurt culture (Streptococcus thermophilus 15HA + Lactobacillus delbrueckii subsp. bulgaricus 2-11) was studied in conditions of aerobic batch fermentation (10-40% dissolved oxygen in milk). The growth and acidification of S. thermophilus 15HA were stimulated at 20% oxygen concentration and the lactic acid process in a mixed culture was shortened by 1 h (2.5 h for the aerobic culture and 3.5 h for the anaerobic mixed culture). Streptococcus thermophilus 15HA oxygen tolerance was significantly impaired at oxygen concentrations in the milk above 30%. Though S. thermophilus 15HA was able to overcome to some extent the impact of high oxygen concentration (40%), the lactic acid produced was insufficient to coagulate the milk casein (4.0 g lactic acid l super(-1) in the mixed culture and 3.8 g lactic acid l super(-1) in the pure culture). A dramatic decrease in the viable cell count of L. delbrueckii subsp. bulgaricus 2-11 in the pure and mixed cultures was recorded at 30% dissolved oxygen.