Properties of Lactobacillus helveticus CNRZ-32 Attenuated by Spray-Drying, Freeze-Drying, or Freezing

Lactobacillus helveticus CNRZ-32 was attenuated for use in accelerated ripening of Cheddar cheese. The goal was to delay acid production without reducing enzyme activity. Changes in the cellular properties of viability, enzyme activity, lactic acid production, and permeability were measured for each attenuation treatment. The viabilities were highest for frozen and freeze-dried cells. Viabilities were lower for cells spraydried at an outlet air temperature of 82C and lowest for 120'C. Aminopeptidase and i3-galactosidase activities decreased with each treatment. Low temperature spray-dried cells had the highest residual aminopeptidase and i3-galactosidase activities by a substantial margin. Acid production was similar for the frozen, freeze-dried, and low temperature spraydried cells, and no lag time occurred; however, high temperature spray-dried cells had a 5-h lag time before producing acid. The increase in permeability was greatest for high temperature spray-dried cells. Viability did not necessarily indicate the extent of cell attenuation. Low temperature spray-dried cells had low viability, but the greatest lactic acid production and enzyme acti vity. High temperature spray-dried cells had the best balance between delaying acid production and maintaining enzyme activity.