Viability of Lactobacillus rhamnosus R0011 in an apple-based fruit juice under simulated storage conditions at the...

Lactobacillus rhamnosus R0011 was inoculated in an apple-pear-raspberry juice blend at 4.5 x 10(9) CFU/250 mL portion, and viability was followed during storage in conditions simulating consumer use. Study parameters were age of the juice (2 or 4 wk), sampling size (one to three 250-mL portions), incubation temperature (between 2 and 7 degrees C), and atmosphere (aerobic compared with anaerobic). Dependent variables were pH, dissolved oxygen (DO) level, and viable count. The DO level in the unopened PETE commercial bottles decreased from 10% to 3% over a 5-wk storage period at 7 degrees C. In shaken and opened bottles, DO increased to 15% during the 1st week of storage, irrespective of sampling size. However, agitation of bottles having more that 250 mL of headspace initially increased DO readings to 30% of maximum, but the DO level subsequently dropped to 15% during the 1-wk storage period between samplings. The presence of L. rhamnosus R0011 did not affect the DO data. The pH varied between 3.6 and 3.9, and was not influenced by L. rhamnosus R0011. However, the pH increased on average by 0.1 unit following multiple agitations and samplings. When the juices remained unopened in the PETE bottles, the viable population gradually dropped by 75% over 5 wk of storage at 7 degrees C, while in opened bottles reduction were only between 20% and 40%. Viability losses under anaerobic conditions were twice as high at 7 degrees C than at 4 degrees C. Data show that consumers can expect good viability of L. rhamnosus R0011 over a few weeks of storage in a refrigerator, even if the bottles have been opened and cells are exposed to oxygen.