Theses and Dissertations


Sulagna Saha

Issuing Body

Mississippi State University


Nannapaneni, Ramakrishna

Committee Member

Haque, Zahur Z.

Committee Member

Sharma, Chander Shekhar

Date of Degree


Document Type

Graduate Thesis - Open Access


Food Science and Technology

Degree Name

Master of Science


College of Agriculture and Life Sciences


Department of Food Science, Nutrition and Health Promotion


Previous findings showed that Listeria monocytogenes exhibits higher heat tolerance to thermal exposure at 60°C when pre-exposed to sublethal heat stress at 48°C for 30/60 min. The objective of this study was to investigate the morphological changes that occurred in L. monocytogenes serotype 1/2a cells as visualized by transmission electron microscopy (TEM) after exposure to sublethal heat stress at 48°C for 60 min and in combination with lethal concentration of carvacrol for 30 min. The TEM micrographs revealed thickening of cell wall and cell membrane, and clumping of cytoplasm when subjected to sublethal heat stress followed by carvacrol treatment. These studies indicate that L. monocytogenes cells when adapted to heat stress may alter its morphology to protect themselves against carvacrol. Further studies will investigate the effect of increased contact time with carvacrol and with other essential oils on the ultrastructural changes in L. monocytogenes cells adapted to heat stress.