Graduate Student Profile - Manoj Ramkrishna sawale

manoj-sawale.jpgManoj Sawale successfully defended his Ph.D. dissertation on June 14, 2024. Manoj is originally from  Dabhadi, Tal- Malegaon, Nasik District, Maharashtra, India. Prior to coming to Purdue, he obtained his Bachelor's of Science in Microbiology from Pune University in Pune, India, and he earned his Master's of Science in Biotechnology from Bangalore University in Bangalore, India.

Manoj's dissertation was entitled, "Microbial Inactivation and Validation of Aseptic Processing and Packaging System Using Vapor Peroxide." 

Liquid hydrogen peroxide (LHP) and vapor hydrogen peroxide (VHP) efficacy as a sterilant for Bacillus atrophaeus and Geobacillus stearothermophilus spores in aseptic packaging systems under commercial sterilization conditions were evaluated in this research. The work centers on quantifying and modeling the kinetic parameters that impact peroxide sterilization efficacy, including the D and Z values, and a novel zconc parameter that relates to the change in the concentration required for a 1-log reduction in spore population. This comprehensive study is divided into four key investigations, each contributing critical insights to understanding peroxide sterilization processes.

The first study examined the inactivation kinetics of B. atrophaeus spores in liquid hydrogen peroxide. The study revealed that higher concentrations and elevated temperatures significantly enhanced spore inactivation by evaluating different concentrations (20%, 28%, and 33%) and temperatures (up to 82.2°C). The Weibull model provided a more accurate fit for the data, indicating a non-linear relationship between spore reduction and exposure time.

The second part of the research explored the use of VHP for sterilizing B. atrophaeus spores. With VHP concentrations of 2500 ppm and 4450 ppm at various temperatures, the study demonstrated that higher concentrations and temperatures are highly effective for spore inactivation. Both log-linear and Weibull models accurately described the inactivation kinetics, with the Weibull model showing a slightly better fit, emphasizing the potential of VHP in achieving commercial sterility.

The third investigation focused on developing predictive models for VHP concentration and its efficacy in spore inactivation. The study evaluated VHP concentrations ranging from 2.32 mg/L to 7.35 mg/L and their impact on spore inactivation rates. The Weibull model proved particularly effective in predicting the inactivation of G. stearothermophilus and B. atrophaeus spores, offering a robust tool for optimizing sterilization protocols in aseptic packaging.

The fourth and final study of the research investigated the influence of surface roughness on spore survival during VHP sterilization cycles on plastic packaging materials. Artificial roughness on high-density polyethylene (HDPE) coupons was created using sandpaper with different grits. B. atrophaeus spores were applied to both roughened and smooth HDPE surfaces. The study finds that rougher surfaces provide more shelter for spores, reducing sterilization efficacy. For example, surfaces roughened with P-36 grit showed a 2.75 log reduction in spore count, whereas smoother surfaces with P-220 grit achieved a 4.42 log reduction. Contact angle measurements indicated that increased roughness led to more hydrophilic surfaces, with water contact angles decreasing from 149.7° for the pristine sample to 105.4° for the P-36 sample. Scanning electron microscopy (SEM) images confirmed that spores were more likely to reside in the valleys of rough surfaces, highlighting the importance of surface characteristics in optimizing VHP sterilization protocols.

The findings of this work underscore the significant impact of hydrogen peroxide concentration, application conditions, and packaging material surface properties on the efficacy of spore inactivation during sterilization. By providing a comprehensive understanding of these factors, the research contributes to developing optimized aseptic sterilization protocols, enhancing the reliability and safety of aseptically packaged food and pharmaceutical products. This work will ensure compliance with regulatory standards and improve food safety in commercial manufacturing, laying a solid foundation for future research and practical applications in VHP sterilization technology.

Manoj's mentor was Dr. Dharmendra Mishra. Other members of his gradate committee included Dr. Amanda Deering, Dr. Arun Bhunia, and Dr. Ferhan Ozadali.

Manoj was drawn to Purdue Food Science for his graduate degree for a couple of reasons, stating, "I chose Purdue University for my graduate degree due to its renowned reputation for research and innovation, especially in food science, aseptic processing, thermal processing, and food engineering. Purdue provides access to advanced facilities and resources crucial for leading-edge research. Moreover, the university boasts a diverse and highly skilled faculty whose expertise closely matches my research interests. The collaborative atmosphere and emphasis on practical, real-world research applications at Purdue solidified my decision that it was the perfect place to pursue my graduate studies and enhance my career."

Manoj adamantly recommends Purdue Food Science to prospective graduate students. "I strongly endorse Purdue Food Science to prospective graduate students due to its top-tier academic and research environment. The program boasts modern facilities, expert and supportive faculty, and excellent industry connections. Purdue focuses on practical research applications and offers great career development opportunities within a collaborative and inclusive community. It's a perfect place to further your academic and professional aspirations in food science."

Manoj was heavily involved in several professional clubs and organizations including Phi Tau Sigma Society, International Association for Food Protection (IAFP), Purdue Cricket Club, Institute of Food Technologists (IFT), Institute for Thermal Processing Specialists (IFTPS), and American Institute of Chemical Engineers (AICHE). In addition to his organizational involvement, Manoj has received several acolades during his time at Purdue Food Science, including:

  • J. Mac Goepfert Developing Scientist Award (2024) - International Association for Food Protection (IAFP)
  • NSF Travel Grant Recipient (2024) - Attended the International Conference on Inverse Problems in Engineering (ICIPE) in Brazil
  • Graduate Recognition Award (2024) - Awarded by the Food Science Department
  • First Place - Charles R. Stumbo Student Paper Competition (2024) - Awarded by the Institute for Thermal Processing Specialists (IFTPS)
  • International Society of Beverage Technologists (ISBT) Scholarship Recipient (2023)
  • Kirlei’s Graduate Student Award (2023) - Purdue University
  • Best Poster Award (Third Prize) - Industrial Associates Meeting (2022) - Purdue University
  • Best Poster Award (Fourth Prize) - Industrial Associates Meeting (2022) - Purdue University
  • International Society of Beverage Technologists (ISBT) Scholarship Recipient (2018)

Post-graduation, Manoj joined Baldwin Richardson Foods as the Corporate Food Safety and Thermal Processing Manager in Macedon, New York. His future goal is to advance to the role of Process Authority, specializing in high- and low-acid foods where he can contribute to ensuring the highest standards of food safety and quality within the industry.