ACIDIFICATION POWER - PERFORMANCE EVALUATION OF FREEZE-DRIED LACTIC-ACID BACTERIA

The Acidification Power Test (AP Test) was originally developed to predict the fermentation activity of fresh wet brewing yeasts. Studies of different samples of wet yeast demonstrated a positive correlation between AP values and fermentation performance. It has subsequently been established that dried yeast cultures can also be evaluated by this method. A modified AP Test is described which can be applied to freeze-dried lactic acid bacteria. The test is simple, rapid and highly reproducible. It can be applied to fresh or freeze-dried industrial starters that generate acid end products by the fermentation of sugars. Evidence is presented to suggest that the AP Test can provide valuable information concerning the physiological activity of lactic starter cultures used in the dairy industry and may eventually replace the Pearce Test as an indicator of fermentation activity. Results from AP Tests demonstrated the value of rehydrating freeze-dried cultures at 43-degrees-C before inoculation of bulk vats.