title: Analysis of different thermal processing methods of foodstuffs to optimize protein, calcium, and phosphorus content for dialysis patients.
abstract: OBJECTIVE
  To analyze how different thermal processing methods affect the protein, calcium, and phosphorus content of hospital food served to dialysis patients and to generate recommendations for preparing menus that optimize nutritional content while minimizing the risk of hyperphosphatemia.
  
  
  METHODS
  Standard Official Methods of Analysis (AOAC) methods were used to determine dry matter, protein, calcium, and phosphorus content in potatoes, fresh and frozen carrots, frozen green beans, chicken, beef and pork, frozen hake, pasta, and rice. These levels were determined both before and after boiling in water, steaming, stewing in oil or water, or roasting.
  
  
  RESULTS
  Most of the thermal processing methods did not significantly reduce protein content. Boiling increased calcium content in all foodstuffs because of calcium absorption from the hard water. In contrast, stewing in oil containing a small amount of water decreased the calcium content of vegetables by 8% to 35% and of chicken meat by 12% to 40% on a dry weight basis. Some types of thermal processing significantly reduced the phosphorus content of the various foodstuffs, with levels decreasing by 27% to 43% for fresh and frozen vegetables, 10% to 49% for meat, 7% for pasta, and 22.8% for rice on a dry weight basis. On the basis of these results, we modified the thermal processing methods used to prepare a standard hospital menu for dialysis patients. Foodstuffs prepared according to the optimized menu were similar in protein content, higher in calcium, and significantly lower in phosphorus than foodstuffs prepared according to the standard menu.
  
  
  CONCLUSIONS
  Boiling in water and stewing in oil containing some water significantly reduced phosphorus content without affecting protein content. Soaking meat in cold water for 1 h before thermal processing reduced phosphorus content even more. These results may help optimize the design of menus for dialysis patients.
authors.affiliation: Department of Dietetics and Nutrition, General Hospital "Dr Josip Benčević", Slavonski Brod, Croatia.
authors.forename: Ivica
authors.initials: I
authors.lastname: Vrdoljak
authors.affiliation: Department of Food Quality Control, Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia. Electronic address: ipanjkota@pbf.hr.
authors.forename: Ines
authors.initials: I
authors.lastname: Panjkota Krbavčić
authors.affiliation: Department of Food Quality Control, Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia.
authors.forename: Martina
authors.initials: M
authors.lastname: Bituh
authors.affiliation: Department of Dietetics and Nutrition, General Hospital "Dr Josip Benčević", Slavonski Brod, Croatia.
authors.forename: Tea
authors.initials: T
authors.lastname: Vrdoljak
authors.affiliation: Department of Dietetics and Nutrition, General Hospital "Dr Josip Benčević", Slavonski Brod, Croatia.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Dujmić
mesh_terms: D000818:Animals; D002136:Calcium, Dietary / Q000032:analysis*; D004044:Dietary Proteins / Q000032:analysis*; D005504:Food Analysis; D005511:Food Handling / Q000379:methods*; D006761:Hospitals; D006358:Hot Temperature; D006801:Humans; D008460:Meat / Q000032:analysis; D009751:Nutritional Requirements; D016226:Phosphorus, Dietary / Q000032:analysis*; D006435:Renal Dialysis; D051436:Renal Insufficiency, Chronic / Q000628:therapy
chemical_list: D002136:Calcium, Dietary; D004044:Dietary Proteins; D016226:Phosphorus, Dietary