title: Effect of heat shock on browning-related enzymes in minimally processed iceberg lettuce and crude extracts.
abstract: The effects of heat shock on PPO and POD activity in minimally processed Iceberg lettuce was examined during storage (10 days). The results were compared with the effect of temperature on crude extracts of these enzymes (in vitro analysis). Fresh-cut lettuce washed at 50 degrees C showed significantly lower PPO and POD activity throughout storage than lettuce washed at 4 degrees C and 25 degrees C. These results were consistent with a sensory analysis in which the panellists found the lowest browning scores in those samples treated at 50 degrees C. When PPO and POD were analysed in vitro, the samples treated at 50 degrees C showed a rapid loss of POD activity and a similar but slower loss of PPO activity in all tissues, while incubation at 4 degrees C and 25 degrees C showed no significant loss of activity. While heat shock did not lead to significant loss of activity it did repress the synthesis of PPO and POD during storage.
authors.affiliation: Dublin Institute of Technology, School of Food Science and Environmental Health, Postharvest Unit, Cathal Brugha Street, Dublin 1, Ireland.
authors.forename: Ana Belen
authors.initials: AB
authors.lastname: Martin-Diana
authors.forename: Daniel
authors.initials: D
authors.lastname: Rico
authors.forename: Catherine
authors.initials: C
authors.lastname: Barry-Ryan
authors.forename: Jemina
authors.initials: J
authors.lastname: Mulcahy
authors.forename: Jesus
authors.initials: J
authors.lastname: Frias
authors.forename: Gary T M
authors.initials: GT
authors.lastname: Henehan
mesh_terms: D004156:Catechol Oxidase / Q000378:metabolism*; D005519:Food Preservation; D018869:Heat-Shock Response; D006358:Hot Temperature; D018545:Lactuca / Q000201:enzymology / Q000378:metabolism*; D015416:Maillard Reaction; D018515:Plant Leaves / Q000201:enzymology / Q000378:metabolism*; D013997:Time Factors
chemical_list: D004156:Catechol Oxidase