Traditional starter cultures for cheddar cheese are combination of Lactococcus lactis. , subsp. lactis and subsp. cremoris. Acidifying rates and temperature dependence vary with both subspecies. Acid production from lactis is faster but cremoris is more suitable for flavor development. Our goal was to compare their growth and survival during cheesemaking and after salting and pressing. Two commercially suitable strains of lactis and cremoris were used (600-M1, E36 and B36, G61 respectively). Starter culture numbers were enumerated by plating on both M17 and Reddy's agar. A standardized make procedure was used with 88'F set temperature and 101'F cook temperature using 1200-lb of pasteurized milk. Curd was sampled at after cut, before draining, after pack and before salting. Final curd was salted with 2.0, 2.4, 2.8, 3.2 and 3.6% salt, pressed for 3 hours and stored at 42'F for 6 days. Cheese after the 6th day was evaluated using plate count and flow cytometry. Flow cytometry measured both living and dead cells based upon permeability to Propiduim iodide and Sybr green. Cheese make time (set -to-mill time) varied from 210 - 400 min depending on the strain. L. lactis subsp. cremoris B36 strain took the longest manufacturing time among all the four strains. The E36 lactis strain had the highest number at before salting than any other strains. The two cremoris strains (B36, G61) were different from each other in terms of acid production, regeneration and cheese make time. There was no difference in cell numbers based on salt content after 6 days. Conclusion: There was difference in performance between same subspecies. Limitation of plate count method was that not all cells multiplied to form colonies. Use of flow cytometry would help track number of living cells during cheese storage and flavor development.
