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 50min, in both concentrated and reconstituted juice. Juices were inoculated with 1.0×104CFU/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 20min of incubation in both concentrated and reconstituted juices; inactivation at 99°C ensued within 1 and 2min. Combination of commercial saponin (100mg/L) with a very short incubation time (1min) at 99°C showed a reduction of 2.34 log cycle for concentrated juice A. acidoterrestris spores (1.0×104CFU/mL) in the first 24h of incubation after treatments. The most efficient treatment was reached with 300, 400 or 500mg/L of purified extract of saponins from S. saponaria after 5days of incubation in concentrated juice, and after 5days with 300 and 400mg/L or 72h with 500mg/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.