The survival of lactococcus lactis in a convective-air-drying environment: The role of protectant solids, oxygen injury, and mechanism of protection
- Authors: Ghandi, Amir , Powell, Ian , Chen, Xiao Dong , Adhikari, Benu
- Date: 2013
- Type: Text , Journal article
- Relation: Drying Technology Vol. 31, no. 13-14 (2013), p. 1661-1674
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- Description: The effect of protectant solids (lactose, sodium caseinate, and their mixture) on the survival of Lactococcus lactis subsp. cremoris was studied in a convective-air-drying environment using single droplet drying. The effect of drying the bacteria in the presence or absence of sodium ascorbate was evaluated, and the evolution of glass transition temperature in the drying process was examined. It was found that the protective efficiency of lactose and sodium caseinate was comparable at the concentrations tested. A mixed protectant matrix (lactose:sodium caseinate, 3:1) gave higher survival than with lactose or sodium caseinate alone at the same total solids level. Protectants enhanced bacterial survival by moderating the drying rate and achieving dryness at lower temperatures, and by facilitating the formation of a glassy matrix earlier in the drying process. The addition of sodium ascorbate was also examined. © 2013 Copyright Taylor and Francis Group, LLC.
- Description: C1
The effect of dryer inlet and outlet air temperatures and protectant solids on the survival of Lactococcus lactis during spray drying
- Authors: Ghandi, Amir , Powell, Ian , Chen, Xiao Dong , Adhikari, Benu
- Date: 2012
- Type: Text , Journal article
- Relation: Drying Technology Vol. 30, no. 14 (2012), p. 1649-1657
- Full Text: false
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- Description: The influence of spray-drying conditions, inlet air temperature (130 degrees C to 200 degrees C), outlet air temperature (38 degrees C to 65 degrees C), drying medium (air and nitrogen) and milk-derived protectants (10%, 15%, and 25% lactose; 5% and 10% sodium caseinate; 10%, 25%, and 35% lactose: sodium caseinate (Lac: NaCas, 3:1)) on the survival of Lactococcus lactis ssp. cremoris was studied using a laboratory-scale spray dryer. An inlet air temperature of 130 degrees C and 65 degrees C as the outlet air temperature maintained high survival of the bacteria without sacrificing low moisture content. Inlet air temperature, previously considered to have no significant effect, was shown to play an important role in the survival of bacteria during spray drying. A mixture of Lac:NaCas (3: 1) showed a better protective effect on the survival of bacteria than lactose and sodium caseinate individually, and this effect increased with increasing amount of protectant. The results were generalized by substituting whey protein isolate for sodium caseinate. Finally, the positive effect of elimination of oxygen was demonstrated both by replacing air with nitrogen and adding ascorbic acid as an oxygen scavenger to improve survival of the bacteria. Adding an oxygen scavenger would be a better candidate for industrial application considering the potential high cost of manufacturing if nitrogen was used as the atomization and/or drying medium.
- Description: C1