title: Discerning intra-tuber differences in textural properties in cooked Solanum tuberosum group Tuberosum and group Phureja tubers.
abstract: BACKGROUND
  The textural properties of potato tubers influence their acceptability and palatability and these properties differ between varieties, groups and progeny. The aim of this study was to compare the textural properties of cooked tubers of Solanum tuberosum group Phureja with those of group Tuberosum.
  
  
  RESULTS
  To assess intra-tuber differences, the textural properties of seven cubes from defined positions along the longitudinal axis of tubers of four Tuberosum group cultivars and three Phureja group lines were tested after cooking using an amended wedge fracture method. Tuberosum group tubers gave consistently higher peak force and work done values during fracture than the Phureja group tubers. Moreover, the values for cubes 1-6 from any tuber were not significantly different and only cube 7, from the stem end, gave higher values. Therefore, the use of any of cubes 1-6 is a valid measurement of the tuber as a whole but the central cube 4 may be most conveniently located. The dry matter content of the cubes did not influence the textural properties of the cubes, which suggested that starch swelling is not the main driving force for textural differences. Total pectin methyl esterase (PME) activity was consistently higher in cubes of the Tuberosum group cultivars over the Phureja group lines.
  
  
  CONCLUSIONS
  The method developed is valid and consistent for assessing textural differences within potato germplasm. The relationship between PME activity and enhanced resistance to fracture suggests that PME may modulate pectin cohesiveness, perhaps through increasing Ca(2+)-bridges, to provide greater resistance to fracture.
authors.affiliation: Plant Products and Food Quality Programme, Scottish Crop Research Institute, Invergowrie, Dundee, UK.
authors.forename: Heather A
authors.initials: HA
authors.lastname: Ross
authors.forename: Gordon J
authors.initials: GJ
authors.lastname: McDougall
authors.forename: Julian F V
authors.initials: JF
authors.lastname: Vincent
authors.forename: Derek
authors.initials: D
authors.lastname: Stewart
authors.forename: Susan
authors.initials: S
authors.lastname: Verrall
authors.forename: Mark A
authors.initials: MA
authors.lastname: Taylor
mesh_terms: D002265:Carboxylic Ester Hydrolases / Q000378:metabolism; D055598:Chemical Phenomena; D019245:Compressive Strength; D003296:Cooking; D005504:Food Analysis / Q000379:methods*; D035281:Plant Tubers / Q000737:chemistry* / Q000201:enzymology; D015203:Reproducibility of Results; D011198:Solanum tuberosum / Q000737:chemistry* / Q000201:enzymology; D013045:Species Specificity
chemical_list: D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase