Adsorption of carvacrol from package headspace onto food surface and its impact on antimicrobial activity
Creators: name: Yuan, Shuo
Publisher: name: No Publisher Supplied
Year: 2024

description: The efficacy of an antimicrobial agent in controlled release packaging (CRP) is influenced by both the headspace concentration of the antimicrobial and its adsorption onto the food surface. However, the mechanistic relationships between antimicrobial efficacy and headspace concentration or adsorption were never fully understood, thereby hindering the optimization of CRP. The overall objective of this study is to elucidate how the efficacy of carvacrol, a prominent antimicrobial agent, in CRP is influenced by its headspace concentration, the concentration on food surface, and the adsorption rate. This information could guide the design and optimization of CRP in future studies. To achieve this goal, the study was conducted in three parts. In the first part of the study, a mechanistic mathematical model was developed to predict the temporal profiles of headspace concentration, surface concentration, and adsorption rate for carvacrol, using the physical principles that govern the movement of carvacrol molecules in a CRP system. The model and its estimated parameter values were validated using three different sets of gas chromatography measurements—this rigorous process confirms the accuracy and reliability of the model. Advancing beyond existing models, our model enhances the understanding of the dynamics between the concentration profile and its interacting processes including evaporation, adsorption, and gas transmission. It provides packaging developers with a superior alternative to the trial-and-error approach to tailor concentration profiles for optimizing antimicrobial efficacy, leading to more efficient and better design of CRP.In the second part of the study, relationships were investigated between carvacrol’s efficacy against E. coli O157:H7 Sakai on tryptic soy agar and variables predicted by the model, including the headspace concentration of carvacrol, its surface concentration, and the adsorption rate. Through different regression analyses and a dimensional analysis using Buckingham π theorem, a strong positive correlation between the surface concentration of carvacrol and its antimicrobial efficacy was revealed, with a potential decline in efficacy after the surface for adsorption becomes saturated with the antimicrobial. Different from surface concentration, carvacrol’s headspace concentration showed no positive correlation with the antimicrobial efficacy, but it may still indirectly contribute to the antimicrobial activity through modifying the surface concentration. In the third part of the study, carvacrol’s efficacy against E. coli O157:H7 Sakai on different foods was studied. The selected foods accounted for different surface properties such as hydrophobicity, porosity, and moisture content. The result not only confirmed the positive correlation between carvacrol’s efficacy and surface concentration, but also associated the various efficacy on different surfaces to carvacrol’s mobility after being adsorbed, expressed by freedom level (δ), drawing inspirations from water activity. Reflected by higher δ, free carvacrol on agar and freeze-dried honeydew had more frequent interaction with microorganisms and showed stronger efficacy. Conversely, with lower δ, carvacrol adsorbed onto blueberries was bound to the food matrix and showed weaker efficacy. Overall, this study used carvacrol to demonstrate that the efficacy of an antimicrobial agent in CRP is regulated by the concentration of the antimicrobial on food surface and its mobility after being adsorbed. Meanwhile, factors like headspace concentration does not directly influence the efficacy but may contribute to the antimicrobial activity through modifying the surface concentration. To design and optimize CRP in future studies, achieving an effective concentration of the antimicrobial on food surface should be the primary focus to ensure effectiveness, and other system parameters can be adjusted accordingly based on the mechanistic model.