title: Applicability of bacterial growth models in spreadable processed cheese.
abstract: BACKGROUND
  Food spoilage is a process in which the quality parameters decrease and products are no longer edible. This is a cumulative effect of bacteria growth and their metabolite production, which is a factor limiting shelf life. Thus, the aim of the study was to evaluate whether microbiological growth models for total viable count (TVC) and Clostridium strain bacteria are reliable tools for prediction of microbiological changes in spreadable processed cheese.
  
  
  METHODS
  Investigations were conducted for two types of bacteria: TVC and Clostridium in following temperature: 8°C, 20°C and 30°C. A total number of aerobic bacteria was determined based on standard PN-EN ISO 4833:2004 and Clostridium was detected by using microbiological procedure for sulphite-reducing anaerobic spore-bacteria with a selective nourishment. During the analysis nonlinear regression and Baranyi and Roberts primary model were used.
  
  
  RESULTS
  For temperatures 20°C and 30°C, Baranyi and Roberts model, for total viable count showed determination coefficient of 70%. The models prepared for Clostridium, in these temperatures, showed much lower R2, respectively 25% and 30%. At the abovementioned temperatures also the expiration of product shelf life was much shorter and amounted 70 days at 20°C and 7 days at 30°C. For both types of bacteria incubated at 8°C the numbers of bacteria decrease until the expiration of product shelf life.
  
  
  CONCLUSIONS
  Models used in the analyses, Baranyi and Roberts and nonlinear regression, poorly matched the experimental data, hence they are not reliable tools. Nevertheless, they gave information about dynamic of microbiological changes in spreadable processed cheese.
authors.affiliation: Department of Food Quality Management, Poznań University of Life Sciences, Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Weiss
authors.affiliation: Department of Food Quality Management, Poznań University of Life Sciences, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Kaczmarek
authors.affiliation: Department of Food Quality Management, Poznań University of Life Sciences, Poland.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Stangierski
mesh_terms: D001420:Bacteria, Aerobic / Q000254:growth & development* / Q000302:isolation & purification; D058491:Bacterial Load; D002611:Cheese / Q000032:analysis / Q000382:microbiology*; D055598:Chemical Phenomena; D003013:Clostridium / Q000254:growth & development* / Q000302:isolation & purification; D003080:Cold Temperature; D005511:Food Handling; D063427:Food Quality; D061353:Food Storage; D055595:Mechanical Phenomena; D050296:Microbial Viability; D008954:Models, Biological; D061352:Pasteurization; D011044:Poland; D015203:Reproducibility of Results
keywords: Baranyi and Roberts model; food spoilage; nonlinear regression; processed cheese