Effect of potassium sorbate and sodium benzoate concentrations on growth of cheese starter cultures

Abstract Text:

Potassium sorbate and sodium benzoate are commonly added to foods as antimicrobials.  The objective was to determine if varying concentrations of potassium sorbate or sodium benzoate affect the growth of DVS R-604 cheese starter cultures at a 10^-4 dilution in peptone and M17 broth containing 5% (w/v) lactose.  Potassium sorbate and sodium benzoate concentrations used were 0% (control), 0.01%, 0.05%, 0.1%, 0.2%, 0.5%, and 1%.  Counts on M17 agar containing 5% (w/v) lactose were performed immediately after inoculation of cheese starter culture and at 1, 2, 3, and 4 days of storage.  Immediately after inoculation, concentration of potassium sorbate or sodium benzoate did not affect counts of cheese starter cultures in either peptone or M17 broth containing 5% (w/v) lactose.  For cheese starter cultures grown in peptone, the counts after 1 day in the presence of 1% potassium sorbate or 1% sodium benzoate were lower than in the presence of the lower concentrations of these antimicrobials.  Also, the decrease of these counts over 4 days of storage was greater in the presence of 0.5% and 1% potassium sorbate or sodium benzoate than in the presence of lower concentrations of these antimicrobials.  For cheese starter cultures grown in M17 broth containing 5% (w/v) lactose, the counts increased between 100 and 1000-fold during the first day of storage after inoculation in the presence of potassium sorbate or sodium benzoate at concentrations of 0.2% or less.  However, this increase was less than 100-fold in the presence of 0.5% and 1% potassium sorbate and 1% sodium benzoate.  Between day 1 and day 4 of storage, the counts in M17 broth containing 5% (w/v) lactose decreased between 10 to 100-fold in the presence of potassium sorbate or sodium benzoate at concentrations of 0.2% or less but this decrease was smaller in the presence of 1% potassium sorbate.  Concentrations of 0.5% and 1% potassium sorbate and sodium benzoate were more effective than lower concentrations for decreasing the counts of cheese starter cultures grown in either peptone or M17 broth containing 5% (w/v) lactose, but this greater effectiveness was observed in different ways in peptone versus M17 broth containing 5% (w/v) lactose.

Keywords:

cheese starter culture, potassium sorbate, sodium benzoate, growth.