Inactivation of Alicyclobacillus acidoterrestris in orange juice by saponin extracts combined with heat-treatment

Alicyclobacillus acidoterrestris is a spoilage-causing bacterium in fruit juices. The inactivation of this bacterium by commercial saponin and saponin purified extract from Sapindus saponaria fruits combined with heat-treatment is described. We investigated heat treatment (87, 90, 95, and 99 °C) with incubation time ranging from 0 to 50 min, in both concentrated and reconstituted juice. Juices were inoculated with 1.0 × 104 CFU/mL of A. acidoterrestris spores for the evaluation of the best temperature for inactivation. For the temperatures of 87, 90, and 95 °C counts of cell viability decreased rapidly within the first 10 to 20 min of incubation in both concentrated and reconstituted juices; inactivation at 99 °C ensued within 1 and 2 min. Combination of commercial saponin (100 mg/L) with a very short incubation time (1 min) at 99 °C showed a reduction of 2.34 log cycle for concentrated juice A. acidoterrestris spores (1.0 × 104 CFU/mL) in the first 24 h of incubation after treatments. The most efficient treatment was reached with 300, 400 or 500 mg/L of purified extract of saponins from S. saponaria after 5 days of incubation in concentrated juice, and after 5 days with 300 and 400 mg/L or 72 h with 500 mg/L in reconstituted juice. Commercial saponin and purified extracts from S. saponaria had similar inactivation power on A. acidoterrestris spores, without significant differences (P > 0.05). Therefore, purified extract of saponins can be an alternative for the control of A. acidoterrestris in fruit juices.