title: Effect of steam cooking on the residual enzymatic activity of potatoes cv. Agria.
abstract: BACKGROUND
  The aim of this work was to study the influence of steam cooking on pectin methylesterase (PME) and endogenous α- and β-amylase activities in different tissues (cortex and pith) of raw and heat-treated potatoes cv. Agria. Three different cooking temperatures were chosen (55, 70 and 85 °C). For each cooking trial, time-temperature profiles were recorded and the degree of cooking was expressed in terms of cooking factor.
  
  
  RESULTS
  Steam cooking contributed to significantly activate PME at 55 °C and to reduce its activity at the final processing temperature (85 °C), with the highest amount in the cortex (0.3745 ± 0.0007 µmol galacturonic acid (GA) g(-1) fresh weight (FW) min(-1) ) compared with the pith (0.2617 ± 0.0012 µmol GA g(-1) FW min(-1) ). The presence of heat-labile and heat-stable isoforms of PME in the considered potato tissues was also assumed. Heat treatment by steam resulted in a significant decrease in endogenous α- and β-amylase activities in both tissues compared with the raw potato, though without complete deactivation. Starch-degrading enzymes were also found to be differently distributed in the raw tuber.
  
  
  CONCLUSIONS
  Steam cooking affected in different ways the assessed residual enzymatic activity in the considered tissues of potatoes cv. Agria. Further research is needed to confirm the results obtained.
authors.affiliation: Department of Food Science, Alma Mater Studiorum, University of Bologna, Campus of Food Science, Piazza Goidanich 60, I-47521 Cesena (FC), Italy. laura.alessandrini@unibo.it
authors.forename: Laura
authors.initials: L
authors.lastname: Alessandrini
authors.forename: Santina
authors.initials: S
authors.lastname: Romani
authors.forename: Pietro
authors.initials: P
authors.lastname: Rocculi
authors.forename: Ingegerd
authors.initials: I
authors.lastname: Sjöholm
authors.forename: Marco
authors.initials: M
authors.lastname: Dalla Rosa
mesh_terms: D002265:Carboxylic Ester Hydrolases / Q000378:metabolism; D055598:Chemical Phenomena; D003296:Cooking / Q000379:methods*; D004789:Enzyme Activation; D004795:Enzyme Stability; D006603:Hexuronic Acids / Q000378:metabolism; D006358:Hot Temperature / Q000009:adverse effects; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D014674:Plant Proteins, Dietary / Q000378:metabolism*; D035281:Plant Tubers / Q000737:chemistry / Q000201:enzymology*; D011489:Protein Denaturation; D011198:Solanum tuberosum / Q000737:chemistry / Q000201:enzymology*; D013046:Specific Gravity; D013213:Starch / Q000032:analysis / Q000378:metabolism; D013227:Steam / Q000009:adverse effects; D014867:Water / Q000032:analysis; D000516:alpha-Amylases / Q000378:metabolism; D001614:beta-Amylase / Q000378:metabolism
chemical_list: D006603:Hexuronic Acids; D007527:Isoenzymes; D014674:Plant Proteins, Dietary; D013227:Steam; D014867:Water; C007819:galacturonic acid; D013213:Starch; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase; D000516:alpha-Amylases; D001614:beta-Amylase