The Pennsylvania State University The Graduate School Department of Food Science CHEMESTHESIS AND BITTERNESS OF NATURAL AND SYNTHETIC ANTI- INFLAMMATORY STIMULI A Thesis in Food Science by Samantha Bennett ! 2012 Samantha Bennett Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science May 2012 ii The thesis of Samantha Bennett was reviewed and approved* by the following: John Hayes Assistant Professor of Food Science Thesis Advisor Joshua Lambert Assistant Professor of Food Science John Coupland Professor of Food Science John Floros Professor of Food Science Head of the Department of Food Science *Signatures are on file in the Graduate School iii ABSTRACT Recently, Gibson’s ecological approach to classifying chemosensation has regained popularity. In his model, sensations are not classified on the basis of anatomy, but rather by the function they serve. The idea of a “chemofensor” complex expands the Gibsonian model to include chemesthetic sensations, as well as the classical bitter and sour tastes and rancid or rotten odors. This comes at a fitting time when more unpalatable, but healthful compounds are incorporated into our diet. In particular, the discovery of oleocanthal, a compound responsible for the pungency of virgin olive oils, has reopened issues of qualitatively assessing the characteristics of chemesthetic compounds. This thesis includes a discussion of the difficulties surrounding a human behavioral approach to measuring chemesthesis and bitterness, including perceptual similarity, temporal considerations, and sensory adaptation. Major experimental findings include: Study 1- Differences between sub-qualities of irritation from olive oil, ibuprofen, and capsaicin were quantified, implicating that olive oil shares qualities with both ibuprofen and capsaicin. Study 2- Behavioral response to compounds that share structural similarity to oleocanthal and ibuprofen were used to identify functional parts of the molecules as well as further characterize the oral sensations from commonly used pain medications. The data from tyrosol and oleuropein suggest the functional end of oleocanthal does not include the phenol group, but may require the aldehyde groups at the other end of the molecule. Study 3- Ibuprofen and naproxen are similar to each other (high irritation, some bitterness), but not acetaminophen (high bitterness, little irritation). This result mimics what would be expected structurally. Finally, in Study 4- we explored the role of fat for masking unpleasant oral sensations from ibuprofen in dairy products. We observed a modest reduction in irritation with increasing milk fat, but bitterness was unaffected. Unexpectedly, the reduction cannot be explained by partitioning into the fat phase, so more sophisticated analyses are needed to understand the binding mechanisms responsible. iv TABLE OF CONTENTS LIST OF FIGURES ................................................................................................................. vi LIST OF TABLES................................................................................................................... viii ACKNOWLEDGEMENTS..................................................................................................... ix Chapter 1 The importance of chemesthesis in flavor ............................................................. 1 Sidebar ............................................................................................................................. 1 Introduction...................................................................................................................... 2 Methodologial Concerns.................................................................................................. 4 Promising Techniques...................................................................................................... 8 Conclusions...................................................................................................................... 9 Chapter 2 Preface.................................................................................................................... 10 Chapter 3 Chemestethic sub-qualities of capsaicin, ibuprofen and olive oil.......................... 14 Introduction...................................................................................................................... 15 Materials and methods ..................................................................................................... 19 Results.............................................................................................................................. 22 Discussion........................................................................................................................ 27 Chapter 4 Structure-activity relationships between olive oil phenolics: tyrosol, oleuropein, and oleocanthal ..................................................................................................... 31 Introduction...................................................................................................................... 31 Materials and methods ..................................................................................................... 34 Results and Discussion .................................................................................................... 36 Chapter 5 Common over-the-counter pain medications differ in their primary perceptual qualities.................................................................................................................................... 39 Introduction...................................................................................................................... 39 Materials and methods ..................................................................................................... 41 Results and Discussion .................................................................................................... 43 Chapter 6 Physiochemical masking of irritation and bitterness with milk fat........................ 46 Introduction...................................................................................................................... 47 Materials and methods ..................................................................................................... 50 Results and Discussion .................................................................................................... 54 Chapter 7 Conclusions and further steps ................................................................................ 60 v References................................................................................................................................ 64 Appendix A: Chapter 2 Copyright Permissions ...................................................................... 69 Appendix B: Chapter 5 Supplemental Data............................................................................. 72 vi LIST OF FIGURES Figure 1-1: Difference scores of time intensity curves for cooling, mint flavor, and bitterness of two gum samples. The control contains peppermint extract and the treatment contains a novel compound intended to increase cooling. While bitterness is higher in the treatment gum for the first two minutes of chewing, it decreases to be no different from the control as cooling peaks after 3 minutes ....................................... 5 Figure 1-2: Time-intensity ratings of capsaicin after exposure to a non-desensitizing stimulus (citric acid) and a desensitizing stimulus (capsaicin) daily for ten days. The graph shows that the group exposed to capsaicin showed significantly lower intensity ratings and faster recovery than the control group............................................ 6 Figure 1-3: Shown is a box plot of group intensity ratings for irritation qualities of olive oil. The data suggests that participants had a difficult time distinguishing between the qualities, as mean intensities are similar for all qualities........................................... 8 Figure 3-1: Chemical structures of (a) the non-steroidal anti-inflammatory drug ibuprofen (b) (")-deacetoxy-dialdehydic ligstroside aglycone [oleocanthal] and (c) capsaicin, a known agonist of the TRPV1 channel. ............................................................................ 16 Figure 3-2: Intensity ratings (group means with standard errors) for ‘overall irritation’ in the throat for each stimulus. Capsaicin was significantly different from olive oil and ibuprofen at all time points, while olive oil and ibuprofen did not differ significantly at any time point. Abbreviations on the right axis correspond to labels given on the gLMS presented to participants: BD= Barely Detectable, W=Weak, M=Moderate, S=Strong, and VS=Very Strong....................................................................................... 24 Figure 3-3: Correlations between Imax values for overall irritation for each stimulus. (A) Ibuprofen correlated with both olive oil (p <0.0001) and capsaicin (p=0.038). (B) Capsaicin was also correlated with olive oil (p=0.005). Similar results were seen for the AUC values ................................................................................................................ 25 Figure 3-4: Percentages for the number of times each of the sub-qualities was described as the ‘predominant sensation’ for the irritation from a particular stimulus. Note that this measure does not directly reflect the intensity