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Chitosan inactivates spoilage yeasts but enhances survival of Escherichia coli O157:H7 in apple juice
Author(s) -
Kiskó G.,
Sharp R.,
Roller S.
Publication year - 2005
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/j.1365-2672.2004.02527.x
Subject(s) - food spoilage , salmonella enterica , chitosan , food science , yeast , escherichia coli , microbiology and biotechnology , biology , salmonella , food microbiology , bacteria , biochemistry , genetics , gene
Aims: To develop new measures for controlling both spoilage and pathogenic micro‐organisms in unpasteurized apple juice using chitosan. Methods and 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°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°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°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. Significance and Impact of the Study: 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.