Source: PURDUE UNIVERSITY submitted to NRP
NANOSCALE TRIBOLOGY OF TASTE: RELATING TEXTURE TO ORAL SENSORY PERCEPTION FOR DESIGN OF FUNCTIONAL FOODS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
NRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
0215571
Grant No.
2009-35603-05002
Cumulative Award Amt.
(N/A)
Proposal No.
2008-01362
Multistate No.
(N/A)
Project Start Date
Jan 1, 2009
Project End Date
Jun 30, 2011
Grant Year
2009
Program Code
[75.0]- Nanoscale Science & Engineering for Agriculture & Food Sys.
Recipient Organization
PURDUE UNIVERSITY
(N/A)
WEST LAFAYETTE,IN 47907
Performing Department
(N/A)
Non Technical Summary
The objective of this research is to understand how food texture affects taste. This work is motivated by food manufacturers' need to control the taste attributes of functional foods. Thus far, the potential for functional foods to improve consumer health has been limited by a lack of large-scale acceptance: although consumers recognize health benefits, they are discouraged by unfavorable taste attributes. It is well known that texture is an extremely important property of food. And it has been proposed that perceived food texture is a physical manifestation of the friction between food particles and surfaces in the mouth. We will therefore investigate this relationship between food texture and friction to support design of functional foods with predetermined taste attributes. We will approach this problem from the fundamental perspective of the interactions of atoms and molecules that occur during the tasting process. Specifically, we will use molecular dynamics simulation to investigate how textural changes impact friction. Textural parameters known to affect taste that we will evaluate include food particle size and shape, as well as compositional properties such as the relative amounts of fat or carbohydrate molecules. We anticipate that characterizing the effect of food texture on friction at the molecular level will enable a fundamental understanding of the taste process which will in turn provide the groundwork for control and intentional design of food taste properties.
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
50250102020100%
Knowledge Area
502 - New and Improved Food Products;

Subject Of Investigation
5010 - Food;

Field Of Science
2020 - Engineering;
Goals / Objectives
The objective of this project is to understand the molecular-scale mechanisms underlying the effect of food texture on taste perception. The specific tasks we will perform to address this goal are the following. First, we will enhance an existing molecular dynamics simulation of a Coette flow to incorporate the critical properties of the nano-scale interfaces that arise during oral sensory perception. Then, we will employ this model to characterize the effect of food texture on friction, focusing on textural parameters known to significantly affect taste. And lastly, we will evaluating the impact of stick-slip vs. smooth sliding on oral friction and therefore taste. These tasks will result in (1) a physically representative molecular model of nanoscale taste processes, (2) a systematic characterization of the effect of food texture on friction, and (3) additional insights into the relationships between texture, friction, and taste. These outputs will create a knowledge base that will enable future work in which food taste attributes are prescribed through textural design.
Project Methods
Molecular dynamics simulation will be employed to investigate the critical tribological links between food texture, friction, and taste. From a design perspective, the physical system of taste is a nanoscale saliva lubricated interface. Nanoscale interfaces operate in the thin film lubrication regime: a new and relatively uncharacterized regime where lubricant thickness is comparable to the size of the lubricant molecule. At this length scale, molecular interactions strongly impact frictional behavior and therefore must be incorporated into a complete model of oral sensory perception. We propose such a model that employs advanced accelerated simulation techniques and incorporates the latest understanding of thin film lubrication behavior. We will employ this model to investigate the effects of food texture on friction thereby providing a physical understanding of the relationship between food texture and taste.

Progress 01/01/09 to 06/30/11

Outputs
OUTPUTS: The primary means of communicating our research to others has been via technical presentations: (1) P. Duval, "Tribology of Food Fats," Technical Presentation, 2011 STLE Annual Meeting, Atlanta GA, (2) H. Gylfadottir "Effect of molecular structure on tribological properties of free fatty acids," Technical Presentation, 2010 STLE Annual Meeting, Las Vegas NV. (3) H. Gylfadottir, 2009. "Effect of molecular structure on free fatty acid properties and correlation to human detection thresholds", Purdue Interdepartmental Nutrition Program Poster Session, February 2010, West Lafayette IN (4) H. Gylfadottir, 2009. "Effect of triglyceride molecular structure on frictional properties of fats", Society of Tribologists and Lubrication Engineers, Poster, 64th Annual Meeting and Exhibition, May 2009, Orlando FL. PI Martini will also be presenting on this topic at the upcoming International Conference on BioTribology. The title of her accepted technical presentation is "Relating food fats to human sensory threshold sensitivity through tribological behaviour". Two graduate research assistants have been involved in this project. One of them, Hildur Gylfadottir, graduated with a Masters in Mechanical Engineering in July 2010. Her thesis title was "Effect of Molecular Structure on Tribological Properties of Free Fatty Acids and Correlation to Human Detection Thresholds". She is now pursuing her career in the pharmaceutical production industry. The other student, Paul Duval, is on track to graduate with his masters in Mechanical Engineering in December 2011. Lastly, this project has led to multiple interdisciplinary collaborations. PARTICIPANTS: PI: Ashlie Martini; Graduate Research Assistants: Ms. Hildur Gyfadottir and Mr. Paul Duval; Collaborators: R. Mattes - Purdue Foods and Nutrition, O. Campanella - Purdue Agricultural and Biological Engineering, M. Colvin - University of California Merced TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Food is vital to life and health as a precursor for various biological compounds, structural elements, nutrient carriers, an energy source, signaling molecules, and more. However, our ability to control or prescribe these outcomes is limited by consumer detection and acceptance of their sensory properties, i.e. taste. Unfortunately, to this point we do not have a fundamental understanding of the relationship between food material properties and our perception of them. Only with such an understanding can the roles that foods play (both positive and negative) be manipulated for desired health outcomes. In this project, we have focused on food fats. A first order measure of human perception of food fats is a detection threshold - the lowest concentration at which participants correctly detect or identify target stimuli. Detection thresholds have been measured in humans and found to vary with FFA chain length and degree of un-saturation. We found no obvious correlation between detection thresholds and bulk material properties. It has been proposed that, during the perception process, the food-palate interface is extremely small, even nanoscale. In this regime, the bulk properties of the food materials do not generally apply. Instead, unique thin film behavior may better reflect the microscopic factors that ultimately influence sensory properties. In this study we investigate the potential correlation between FFA detection and thin film material properties using molecular dynamics (MD) simulation. MD simulation is ideal for this research because of its flexibility and the ability to explicitly control molecular structure (details of the model are available elsewhere). Food applications of MD are somewhat limited, but results from the studies have been performed are encouraging and imply that modeling can be an important tool to predict behavior of food systems. Using this method, we characterized the four FFA's mentioned above in terms of their thin film density and compressibility, and the slip (velocity difference) at the solid-liquid interface. The results have been extremely promising and indicate that there may indeed be correlations between nanoscale properties of food materials and our perception of them. We have complemented the atomistic modeling approach with classical tribology models of thin film lubrication. In these models, we consider the tongue-palate interface to be lubricated by food materials. Such models enable us to predict the film thickness and friction that occurs in this interface during the tasting process. We have correlated these predictions to human perception of a variety of liquid or semi-liquid food materials (e.g. mayonnaise, cream, yogurt). The consistency of these correlations has shown that there is significant potential for tribological models in understanding and predicting human perception of foods.

Publications

  • P. Duval and A. Martini, 2011, "Tribology of Food Fats," 2011 STLE Annual Meeting Abstract Book, Atlanta, GA.
  • H. Gylfadottir, R.D. Mattes and A. Martini, 2011, "Effect of Free Fatty Acid Molecular Characteristics on Material Properties and Detection," International Journal of Food Engineering, Pending.
  • H. Gylfadottir and A. Martini, 2010, "Effect of molecular structure on tribological properties of free fatty acids," 2010 STLE Annual Meeting Abstract Book, Las Vegas, NV.
  • H. Gylfadottir and A. Martini, 2009, "Effect of Trigylceride Molecular Structure on Frictional Properties of Fat," 2009 STLE Annual Meeting Abstract Book, Orlando, FL.


Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: The primary means of communicating our research to others has to this point been via technical presentations: (1) H. Gylfadottir and A. Martini, "Effect of molecular structure on tribological properties of free fatty acids," Technical Presentation, 2010 STLE Annual Meeting, Las Vegas, NV. (2) H. Gylfadottir and A. Martini, 2009. "Effect of molecular structure on free fatty acid properties and correlation to human detection thresholds", Purdue Interdepartmental Nutrition Program Poster Session, February 2010, West Lafayette, IN (3) H. Gylfadottir and A. Martini, 2009. "Effect of triglyceride molecular structure on frictional properties of fats", Society of Tribologists and Lubrication Engineers, Poster, 64th Annual Meeting and Exhibition, May 2009, Orlando, Florida. The graduate student research assistant on this project has also recently graduated with a Masters in Mechanical Engineering. Her thesis title was "Effect of Molecular Structure on Tribological Properties of Free Fatty Acids and Correlation to Human Detection Thresholds". She is now pursuing her career in the pharmaceutical production industry. Lastly, this project has lead to interdisciplinary collaborations between researchers in Mechanical Engineering (PI Martini), Foods and Nutrition (R. Mattes), and Agricultural and Biological Engineering (O. Campanella). PARTICIPANTS: PI: Ashlie Martini; Graduate Research Assistant: Ms. Hildur Gyfadottir; Collaborators: R. Mattes - Purdue Foods and Nutrition, O. Campanella - Purdue Agricultural and Biological Engineering TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Food is vital to life and health as a precursor for various biological compounds, structural elements, nutrient carriers, an energy source, signaling molecules, and more. However, our ability to control or prescribe these outcomes is limited by consumer detection and acceptance of their sensory properties, i.e. taste. Unfortunately, to this point we do not have a fundamental understanding of the relationship between food material properties and our perception of them. Only with such an understanding can the roles that foods play (both positive and negative) be manipulated for desired health outcomes. We here focus on food fats. Triacylglycerol (triglyceride) is the primary molecular form of food fats and consist of three fatty acids (FFA) attached to a glycerol backbone. While they are detected largely by their tactile properties, FFAs are also thought to be detected by olfactory and possibly taste mechanisms, with the latter holding unique health implications. The material properties of FFAs are functions of their molecular characteristics and the large number of molecular configurations possible in food fats is directly related to the complexity of determining their effects on human perception. A first order measure of human perception is a detection threshold - the lowest concentration at which participants correctly detect or identify target stimuli. Detection thresholds have been measured in humans and found to vary with FFA chain length and degree of un-saturation. In preliminary work, we found no obvious correlation between detection thresholds and bulk material properties. It has been proposed that, during the perception process, the food-palate interface is extremely small, even nanoscale. In this regime, the bulk properties of the food materials do not generally apply. Instead, unique thin film behavior may better reflect the microscopic factors that ultimately influence sensory properties. In this study we investigate the potential correlation between FFA detection and thin film material properties using molecular dynamics (MD) simulation. MD simulation is ideal for this research because of its flexibility and the ability to explicitly control molecular structure (details of the model are available elsewhere). Food applications of MD are somewhat limited, but results from the studies have been performed are encouraging and imply that modeling can be an important tool to predict behavior of food systems. To this point, we have characterized the four FFA's mentioned above in terms of their thin film density and compressibility, and the slip (velocity difference) at the solid-liquid interface. The results have been extremely promising and indicate that there may indeed be correlations between nanoscale properties of food materials and our perception of them. Next research steps include extending the method developed to characterize additional and more complex molecules in confinement and evaluate those findings by comparison to more subtle human perceptions.

Publications

  • H. Gylfadottir, R.D. Mattes and A. Martini, 2011, "Effect of Free Fatty Acid Molecular Characteristics on Material Properties and Detection," International Journal of Food Engineering, Pending.
  • H. Gylfadottir and A. Martini, 2010, "Effect of molecular structure on tribological properties of free fatty acids," 2010 STLE Annual Meeting Abstract Book, Las Vegas, NV.
  • H. Gylfadottir and A. Martini, 2009, "Effect of Trigylceride Molecular Structure on Frictional Properties of Fat," 2009 STLE Annual Meeting Abstract Book, Orlando, FL.


Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: The primary means of communicating our research to others has to this point been via technical poster presentations: H. Gylfadottir and A. Martini, 2009, Effect of triglyceride molecular structure on frictional properties of fats, Society of Tribologists and Lubrication Engineers, Student Poster Competition, 64th Annual Meeting and Exhibition, May 2009, Orlando, Florida. H. Gylfadottir and A. Martini, 2009, Effect of molecular structure on free fatty acid properties and correlation to human detection thresholds, Purdue Interdepartmental Nutrition Program Poster Session, February 2010, West Lafayette, Indiana. PARTICIPANTS: Principle Investigator: Dr. Ashlie Martini - Assistant Professor of Mechanical Engineering, Purdue University Graduate Research Assistant: Hildur Gylfadottir Collaborators: Dr. Richard Mattes - Professor of Foods and Nutrition, Purdue University; Dr. Osvaldo Campanella - Professor of Agricultural and Biological Engineering, Purdue University TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
This project has had a significant outcome that I could not have predicted at its inception: the graduate student researcher has become aware of and is enthusiastically pursing studies in food science and engineering. This project has been primarily undertaken by a Mechanical Engineering masters student, Hildur Gylfadottir. When she started this work, her intention was to complete the masters program and then enter the workforce as a Mechanical Engineering. However, her participation in this project has lead to awareness of the importance and excitement of food science and engineering. This awareness started through collaboration with Dr. Richard Mattes from the Purdue Foods and Nutrition department who is now a member of Hildur's graduate committee. Hildur is also taking a class in the Food and Nutrition department, Human Sensory Systems and Food Evaluation, this semester. This interaction has been extremely fruitful and has also led Hildur to become interested in pursuing PhD study in this area. Thus, this project has encouraged a promising young researcher to continue her graduate research, and has made her aware of the socially relevant research questions to which she can apply her talents going forward.

Publications

  • We are in the final stages of preparing a full manuscript for publication and anticipate submission in the next month. However, we also have a conference abstract: H. Gylfadottir and A. Martini, 2009, Effect of triglyceride molecular structure on frictional properties of fats, Society of Tribologists and Lubrication Engineers, 64th Annual Meeting and Exhibition Program and Abstract Book, Orlando, Florida.