Open Access
Anderson, Nathan Morgan
Graduate Program:
Agricultural and Biological Engineering
Doctor of Philosophy
Document Type:
Date of Defense:
July 05, 2006
Committee Members:
  • Paul Walker, Committee Chair
  • Virendra Puri, Committee Member
  • Robert Bruce Beelman, Committee Member
  • Stephanie Doores, Committee Member
  • mushroom
  • Agaricus bisporus
  • thermal processing
  • heat penetration
  • inoculated pack study
  • Clostridium sporogenes
A continuous steam sterilization unit capable of producing shelf-stable aseptically processed particulate foods of high quality was developed. The system utilizes steam as the heating medium to achieve better heat transfer and segmented-flow technology to produce a smaller residence time distribution than pipe-flow aseptic processing. A temperature penetration test was used as the foundation for developing a scheduled thermal process using microbiological kinetics. Most conservative process times of 11.04 and 3.74 minutes to achieve a 5D process for Clostridium sporogenes for whole and sliced mushrooms, respectively, were calculated from temperature penetration data. Aseptic processing times are less than would typically be encountered in conventional canning of mushrooms. When compared to conventionally canned mushrooms, aseptically processed yield (weight basis) increased 6.1% (SD=2.9%) and 6.6% (SD=2.2%), whiteness (L) improved 3.1% (SD=1.9%) and 4.7% (SD=0.7%), color difference (ÄE) improved 6.0% (SD=1.3%) and 8.5% (SD=1.5%), and texture improved 3.9% (SD=1.7%) and 4.6% (SD=4.2%) for whole and sliced mushrooms, respectively. The segmented-flow processing system utilized high temperature, short time (HTST) processing conditions, eliminated a separate blanching step, eliminated the unnecessary packaging of water and promoted the use of bag-inbox and other versatile aseptic packaging methods. Inoculated pack studies proved the development of a scheduled process based on temperature penetration data of the slowest heating particle lead to predictable destruction of Clostridium sporogenes spores. At an inoculation level of approximately 103 CFU/container, viable spores were eliminated after 9.3 minutes process time, indicating that 11.0 minutes of process time used in this study could be likely be reduced to approximately 10 minutes. Following aseptic processing, mass had decreased 24.4% (SD=2.9%) and 55.9% (SD=3.1%), volume 51.8% (SD=1.9%) and 56.8% (SD=3.3%), and characteristic mushroom dimensions 4.7% (SD=5.8%) to 28.4% (SD=5.2%) and 9.0% (SD=3.8%) to 30.4% (SD=4.4%) for aseptically processed versus raw, and aseptically processed versus vacuum hydrated mushrooms, respectively. However, on average, length decreased 96.6% and 63.8% more than diameter. Vacuum hydration increased moisture content (dry basis) by 71.5% relative to raw mushrooms. Aseptic processing decreased moisture content (dry basis) by 27.4% and 57.7% relative to raw and vacuum hydrated mushrooms, respectively.