University of Vermont ScholarWorks @ UVM Graduate College Dissertations and Theses Dissertations and Theses 2018 Analysis of surface crystals on soft washed rind cheeses using polarized light microscopy and their effect on the sensory perception of grittiness Patrick Polowsky University of Vermont Follow this and additional works at: https://scholarworks.uvm.edu/graddis Part of the Food Science Commons Recommended Citation Polowsky, Patrick, "Analysis of surface crystals on soft ashew d rind cheeses using polarized light microscopy and their effect on the sensory perception of grittiness" (2018). Graduate College Dissertations and Theses. 864. https://scholarworks.uvm.edu/graddis/864 This Thesis is brought to you for free and open access by the Dissertations and Theses at ScholarWorks @ UVM. It has been accepted for inclusion in Graduate College Dissertations and Theses by an authorized administrator of ScholarWorks @ UVM. For more information, please contact [email protected]. ANALYSIS OF SURFACE CRYSTALS ON SOFT WASHED RIND CHEESES USING POLARIZED LIGHT MICROSCOPY AND THEIR EFFECT ON THE SENSORY PERCEPTION OF GRITTINESS A Thesis Presented by Patrick Polowsky to The Faculty of the Graduate College of The University of Vermont In Partial Fulfillment of the Requirements for the Degree of Master of Science Specializing in Nutrition and Food Sciences May, 2018 Defense Date: March 19, 2018 Thesis Examination Committee: Paul S. Kindstedt, Ph.D., Advisor John M. Hughes, Ph.D., Chairperson Catherine W. Donnelly, Ph.D. Cynthia J. Forehand, Ph.D., Dean of the Graduate College ABSTRACT With the rising popularity of artisanal cheese in the United States, the soft washed rind category has emerged as a fast-growing segment of the marketplace. There is much anecdotal evidence to suggest a common sensorial defect in soft washed rind cheese is a gritty/sandy texture attributed to crystal growth on the rind of these cheeses A preliminary study was undertaken to develop a set of criteria to visually identify crystals found on soft washed rind cheeses. Single crystal identities were presumptively determined using polarized light microscopy (PLM), and cross-checked using powder x- ray diffractometry (PXRD). Two distinct crystal groupings were determined based on these metrics. Group 1 crystals had high birefringent coloring, angle of extinction (AE) ≈ 90°, and were smaller and less circular than Group 2 crystals (P<0.05). Group 2 crystals had no birefringent coloring and AE ≈ 18°. Using established mineralogical data, Group 1 and Group 2 crystals were identified to be struvite and ikaite, respectively. These crystalline bodies are situated in an amorphous cheese matrix (i.e. smear), which create difficulties when examining via PLM and PXRD, leading to high background noise. To remedy these issues, a novel method for harvesting crystals was developed. Smear scrapings were immersed in NaOH (pH=10) to dissolve smear material, which resulted in improved PLM and PXRD performance. A subsequent observational study was conducted to understand the prevalence of surface crystals and grittiness associated with washed rind cheeses sourced from the U.S.A. and Europe. Crystal types were identified via PXRD and PLM. Crystal size and shape (circularity) metrics were determined via PLM and image analysis. A descriptive sensory panel (n=12) was used to evaluate grittiness presence and intensity. Identified crystal types included ikaite, struvite, calcite, and brushite. Mean crystal length and area ranged from ~30μm to ~1100μm, and ~500μm2 to ~200,000μm2, respectively. Sensory perception threshold for grittiness occurred at a mean crystal length of ~70μm and mean crystal area of ~2900μm2. Below these threshold levels, cheeses presented with negligible grittiness. Above these threshold levels, grittiness was highly correlated with crystal length and area (r=0.93 and 0.96, respectively; P<0.001). These results indicate surface crystals have a direct impact on the sensorial quality of soft washed rind cheeses. ACKNOWLEDGEMENTS I would like to express my sincere gratitude to my advisor, Dr. Paul Kindstedt, who pushed my intellectual boundaries and shepherded me along my academic journey. I consider it a great privilege to have had the chance to work with such a titan of the dairy world. Much appreciation and gratefulness to Dr. John Hughes, whose guidance and know-how made this work possible. His passion and expertise for crystallography inspires me to continue to seek ways that disparate fields can be intermingled. Many thanks to Dr. Catherine Donnelly for her encouragement and providing invaluable feedback along my journey. I must recognize Dr. Gil Tansman for his friendship and mentorship. His enthusiasm, curiosity, and knowledge was the solid foundation on which this work was built. Many thanks to Jasper Hill Farm and The Cellars at Jasper Hill for their support. I could not ask for a better industry partner in conducting this work. ii TABLE OF CONTENTS Acknowledgements ............................................................................................................. ii List of Tables ..................................................................................................................... iv List of Figures ..................................................................................................................... v Chapter 1: Comprehensive Literature Review .................................................................... 1 Mineral Components of Milk and Cheese ...................................................................... 1 Microbiology and Physico-Chemistry of Washed Rind Cheeses ................................... 4 Basic Dynamics of Crystallization and Biomineralization ........................................... 12 Potential Surface Crystal Dynamics on Washed Rind Cheeses .................................... 17 Sensory Perception of Grittiness in Relation to Dairy Products ................................... 23 Historical Aspects of Cheese Crystals .......................................................................... 25 Basics of Polarized Light Microscopy .......................................................................... 31 References ..................................................................................................................... 35 Chapter 2: Characterization and presumptive identification of surface crystals on smear ripened cheese by polarized light microscopy ................................................ 47 Abstract ......................................................................................................................... 47 Introduction ................................................................................................................... 49 Materials And Methods ................................................................................................. 52 Results And Discussion ................................................................................................ 56 Conclusions ................................................................................................................... 63 Acknowledgments ......................................................................................................... 64 References ..................................................................................................................... 65 Chapter 3: Size, Shape, and Identity of Surface Crystals and their Relationship to Sensory Perception of Grittiness in American Artisanal and European PDO Soft Smear Ripened Cheeses ............................................................................................. 77 Abstract ......................................................................................................................... 77 Introduction ................................................................................................................... 78 Materials And Methods ................................................................................................. 81 Results ........................................................................................................................... 86 Discussion ..................................................................................................................... 89 Conclusion .................................................................................................................... 95 Acknowledgments ......................................................................................................... 95 References ..................................................................................................................... 96 Comprehensive Works Cited .......................................................................................... 111 Appendix A: Supplementary Diffractorgrams ................................................................ 126 Appendix B: Supplementary PCA Figures ..................................................................... 138 iii LIST OF TABLES Table 1. Mineral composition in milk. Adapted from Lucey and Horne 2009. ................. 1 Table 2. Mineral contents of common cheese varieties. Adapted from Zamberlin et al. 2012. ............................................................................................................................ 3 Table 3. Microbes isolated from rinds of smear ripened cheeses. Adapted from Wolfe et al. 2014 and Hohenegger et al. 2014.