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

Abstract

Abstract Ca 2+ (0–60 g litre −1 ), glycerol (0–100 g litre −1 ), and non‐fat dry milk solids (NFDMS, 0–140 g litre −1 ) were combined to study their effects on the survival of Lactobacillus 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 Ca 2+ 5.34 g litre −1 . NFDMS 100.8 g litre −1 , and glycerol 41.5 g litre −1 and that of controlled low‐temperature vacuum dehydration was Ca 2+ 5.67 g litre −1 , NFDMS 107.1 g litre −1 , and glycerol 41.0 g litre −1 . Models obtained were tested using t ‐tests. Survival of freezing under different conditions was found to be not significantly different.