Viability, efficacy, and storage stability of freeze-dried biocontrol agent Candida sake using different protective and rehydration media.
Viability, efficacy against Penicillium expansum on Golden Delicious apples, and storage stability of freeze-dried Candida sake strain CPA-1 were studied. The effect of several protective agents and rehydration media was investigated in the freeze drying of C. sake. Skimmed milk at 10% concentration was a good rehydration medium for all protectants tested. In general, good viability results were obtained when the same solution was used as a protectant and as a rehydration medium. The best survival was obtained when C. sake cells were protected with 10% lactose + 10% skimmed milk and rehydrated with skimmed milk (85% viability). The potential for biocontrol of the best freeze-dried treatments against P. expansum on apples was compared with that of fresh cells. Freeze-dried treatments at 1 x 10(7) CFU/ml reduced the incidence of decay by 45 to 66%. The best biocontrol effect was obtained with cells that had been freeze dried using 10% lactose + 10% skimmed milk as a protectant and 1% peptone as a rehydration medium, with a 66% reduction in rot incidence. However, in all treatments, the efficacy of freeze-dried cells was significantly lower than fresh cells. The stability of freeze-dried samples decreased during storage and was influenced by storage temperature. In the best treatment, storage of C. sake cells for 60 days at 4 degrees C resulte in final concentrations of 2.5 x 10(8) CFU/ml, which was a 10-fold reduction in relation to the initial starting concentration of cells prior to freeze drying.
Abadias
M
M
Postharvest Unit, CeRTA, Centre UdL-IRTA, Lleida, Catalonia, Spain. isabel.abadias@irta.es
Teixidó
N
N
Usall
J
J
Benabarre
A
A
Viñas
I
I
D002175:Candida / Q000254:growth & development*; D015169:Colony Count, Microbial; D003451:Cryoprotective Agents / Q000494:pharmacology*; D005511:Food Handling / Q000379:methods*; D005612:Freeze Drying; D010407:Penicillium / Q000254:growth & development*; D019685:Rosales / Q000382:microbiology*; D013696:Temperature; D013997:Time Factors
D003451:Cryoprotective Agents