Studies on the effect of protectants on Lactobacillus acidophilus strain dehydrated under controlled low‐temperature vacuum dehydration and freeze‐drying by using response surface methodology

Abstract

CaZ+ (0-60 g litre-'), glycerol (0-100 g litre-'), and non-fat dry milk solids (NFDMS, 0-140 g litre-') were combined to study their effects on the survival of Latobacillus acidophilus in controlled low-temperature vacuum dehydration and freeze-drying. A three-variable (each at three-levels) design method was used and analysed by fitting a quadratic response surface. These factors were found to be significantly effective on survival. Fitted quadratic regression equations were plotted using a graphing software package. Conditions for the best survival of freeze-drying was found to be Caz+ 5-34 g litre-'. NFDMS 100.8 g litre-', and glycerol 41.5 g litre-' and that of controlled lowtemperature vacuum dehydration was Ca2+ 5.67 g litre-', NFDMS 107.1 g litre-', and glycerol 41.0 g litre-'. Models obtained were tested using t-tests. Survival of freezing under different conditions was found to be not significantly different.

Survival of freeze-dried Lactobacillus acidophilus immobilized in .KAPPA.-carrageenan gel.

“…The pH of the medium was adjusted to 6.5 with 1 M HCl before autoclaving. Bacteria were proliferated statically in flasks containing 500 ml MRS broth with 1% inoculum and incubated at 37°C for 12-14 h. After incubation, cells were harvested by centrifugation at 8,000ϫg for 15 min at 0°C and washed twice with 0.1% peptone water (King and Lin, 1995;King and Su, 1993). Cell cultures from the previous procedure were suspended in 0.1% peptone water to obtain a concentrated cell suspension which contained a cell concentration level of 10 10 cells/ml.…”

Accelerated storage testing of freeze-dried and controlled low-temperature vacuum dehydrated Lactobacillus acidophilus.

“…The culture might be mixed with some protectants in order to improve survival during the drying process (Potts, 1994). Controlled low-temperature vacuum dehydration (CLTVD), a newly developed drying method, was used to dehydrate the strain in order to avert some defects of freeze-drying, and products with quality close to those of freeze-drying could be obtained (King and Lin, 1995;King and Su, 1993). The application of CLTVD not only reduced the drying time and cost but also avoided freeze-injury to the cells (King and Su, 1993).…”

“…The application of CLTVD not only reduced the drying time and cost but also avoided freeze-injury to the cells (King and Su, 1993). The combination of adding CaCO 3 , glycerol, and nonfat dry milk solids (NFDMS) as protectants had also been studied in CLTVD and freeze-drying for the amelioration of survival during the drying of cultures (King and Lin, 1995).…”

“…After incubation, the cells were collected by centrifugation at 8,000ϫg for 15 min at 0°C and washed twice with peptone water. In the experiments with protectants, MRS broth was supplemented with CaCO 3 to a concentration of 0.53% for freezedrying and 0.57% for CLTVD according to the optimum results obtained by King and Lin (1995). The cell pellets were then suspended in 10 ml protective media to make concentrated cell suspensions of about 10 9 -10 10 cells/ml for the experiments.…”

“…The cell pellets were then suspended in 10 ml protective media to make concentrated cell suspensions of about 10 9 -10 10 cells/ml for the experiments. Three different protective media were used for experiments: (1) 10% NFDMS was used as the basal medium for drying without protectants (Bozoglu and Gurakan, 1989;King and Su, 1993), (2) 4.15% glycerol and 10.08% NFDMS for freeze-drying, and (3) 4.10% glycerol and 10.71% NFDMS for CLTVD with protectants based on the optimum conditions obtained by King and Lin (1995).…”