Chitosan inactivates spoilage yeasts but enhances survival of Escherichia coli O157:H7 in apple juice.
OBJECTIVE
To develop new measures for controlling both spoilage and pathogenic micro-organisms in unpasteurized apple juice using chitosan.


RESULTS
Micro-organisms were isolated and identified from apple juice treated or untreated with chitosan using enrichment, selective media, microscopy, substrate assimilation patterns and ribosomal DNA profiling. Chitosan (0.05-0.1%) delayed spoilage by yeasts at 25 degrees C for up to 12 days but the effect was species specific: Kloeckera apiculata and Metschnikowia pulcherrima were inactivated but Saccharomyces cerevisiae and Pichia spp. multiplied slowly. In challenge experiments at 25 degrees C, total yeast counts were 3-5 log CFU ml(-1) lower in chitosan-treated juices than in the controls for 4 days but the survival of Escherichia coli O157:H7 was extended from 1 to 2 days; at 4 degrees C, chitosan reduced the yeast counts by 2-3 log CFU ml(-1) for up to 10 days but survival of the pathogen was prolonged from 3 to 5 days. The survival of Salmonella enterica serovar Typhimurium was unaffected by chitosan at either temperature.


CONCLUSIONS
The addition of chitosan to apple juice delayed spoilage by yeasts but enhanced the survival of E. coli O157:H7.


CONCLUSIONS
The results suggest that the use of chitosan in the treatment of fruit juices may potentially lead to an increased risk of food poisoning from E. coli O157:H7.
Kiskó
G
G
Szent István University, Budapest, Hungary.
Sharp
R
R
Roller
S
S
D001628:Beverages / Q000382:microbiology*; D001672:Biocompatible Materials / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D048271:Chitosan / Q000494:pharmacology*; D015169:Colony Count, Microbial / Q000379:methods; D003470:Culture Media; D019453:Escherichia coli O157 / Q000187:drug effects / Q000254:growth & development* / Q000302:isolation & purification; D005516:Food Microbiology; D027845:Malus / Q000382:microbiology*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification; D012486:Salmonella typhimurium / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification; D013045:Species Specificity; D015003:Yeasts / Q000187:drug effects / Q000254:growth & development* / Q000302:isolation & purification
D001672:Biocompatible Materials; D003470:Culture Media; D048271:Chitosan