title: Optimization of hot water treatment for removing microbial colonies on fresh blueberry surface.
abstract: Blueberries for the frozen market are washed but this process sometimes is not effective or further contaminates the berries. This study was designed to optimize conditions for hot water treatment (temperature, time, and antimicrobial concentration) to remove biofilm and decrease microbial load on blueberries. Scanning electron microscopy (SEM) image showed a well-developed microbial biofilm on blueberries dipped in room temperature water. The biofilm consisted of yeast and bacterial cells attached to the berry surface in the form of microcolonies, which produced exopolymer substances between or upon the cells. Berry exposure to 75 and 90 °C showed little to no microorganisms on the blueberry surface; however, the sensory quality (wax/bloom) of berries at those temperatures was unacceptable. Response surface plots showed that increasing temperature was a significant factor on reduction of aerobic plate counts (APCs) and yeast/mold counts (YMCs) while adding Boxyl® did not have significant effect on APC. Overlaid contour plots showed that treatments of 65 to 70 °C for 10 to 15 s showed maximum reductions of 1.5 and 2.0 log CFU/g on APCs and YMCs, respectively; with acceptable level of bloom/wax score on fresh blueberries. This study showed that SEM, response surface, and overlaid contour plots proved successful in arriving at optima to reduce microbial counts while maintaining bloom/wax on the surface of the blueberries.
  
  
  CONCLUSIONS
  Since chemical sanitizing treatments such as chlorine showed ineffectiveness to reduce microorganisms loaded on berry surface (Beuchat and others 2001, Sapers 2001), hot water treatment on fresh blueberries could maximize microbial reduction with acceptable quality of fresh blueberries.
authors.affiliation: Dept. of Food Science, Nutrition and Health Promotion, Mississippi State Univ., Mississippi State, MS 39762, USA. tkim@foodscience.msstate.edu
authors.forename: Tae Jo
authors.initials: TJ
authors.lastname: Kim
authors.forename: Melody P
authors.initials: MP
authors.lastname: Corbitt
authors.forename: Juan L
authors.initials: JL
authors.lastname: Silva
authors.forename: Dja Shin
authors.initials: DS
authors.lastname: Wang
authors.forename: Yean-Sung
authors.initials: YS
authors.lastname: Jung
authors.forename: Barbara
authors.initials: B
authors.lastname: Spencer
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology; D018441:Biofilms / Q000187:drug effects; D029798:Blueberry Plants / Q000737:chemistry / Q000382:microbiology*; D015169:Colony Count, Microbial; D005519:Food Preservation / Q000379:methods*; D005638:Fruit / Q000737:chemistry / Q000382:microbiology*; D005658:Fungi / Q000187:drug effects / Q000302:isolation & purification / Q000502:physiology / Q000648:ultrastructure; D006088:Gram-Negative Aerobic Bacteria / Q000187:drug effects / Q000302:isolation & purification / Q000502:physiology / Q000648:ultrastructure; D006094:Gram-Positive Bacteria / Q000187:drug effects / Q000302:isolation & purification / Q000502:physiology / Q000648:ultrastructure; D006358:Hot Temperature; D006801:Humans; D050296:Microbial Viability / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D016877:Oxidants / Q000494:pharmacology; D010858:Pigmentation / Q000187:drug effects; D019441:Plant Epidermis / Q000737:chemistry / Q000187:drug effects / Q000382:microbiology* / Q000648:ultrastructure; D011786:Quality Control; D012677:Sensation; D014867:Water / Q000737:chemistry
chemical_list: D000890:Anti-Infective Agents; D016877:Oxidants; D014867:Water