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Levenston, M. E.

Publications and source records attributed to Levenston, M. E..

5 recordsLinked to original sources

Got meat? The mechanical signature of plant-based and animal meat

Eating less meat is associated with a healthier body and planet. Yet, we remain reluctant to switch to a plant-based diet, largely due to the sensory experience of plant-based meat. Food scientists characterize meat using a double compression test, which only probes one-dimensional behavior. Here we use tension, compression, and shear tests-combined with constitutive neural networks-to automatically discover the behavior of eight plant-based and animal meats across the entire three-dimensional spectrum. We find that plant-based sausage and hotdog, with stiffnesses of 95.9{+/-}14.1kPa and 38.7{+/-}3.0kPa, successfully mimic their animal counterparts, with 63.5{+/-}45.7kPa and 44.3{+/-}13.2 kPa, while tofurky is twice as stiff, and tofu is twice as soft. Strikingly, a complementary food tasting survey produces in nearly identical stiffness rankings for all eight products ({rho} =0.833, p=0.015). Probing the fully three-dimensional signature of meats is critical to understand subtle differences in texture that may result in a different perception of taste. Our data and code are freely available at https://github.com/LivingMatterLab/CANN

bioengineering↗

Discovering the mechanics of artificial and real meat

Artificial meat is an eco-friendly alternative to real meat that is marketed to have a similar taste and feel. The mechanical properties of artificial meat significantly influence our perception of taste, but how precisely the mechanics of artificial meat compare to real meat remains insufficiently understood. Here we perform mechanical tension, compression, and shear tests on isotropic artificial meat (Tofurky(R) Plant-Based Deli Slices), anisotropic artificial meat (Daring Chickn Pieces) and anisotropic real meat (chicken) and analyze the data using constitutive neural networks and automated model discovery. Our study shows that, when deformed by 10%, artificial and real chicken display similar maximum stresses of 21.0 kPa and 21.8 kPa in tension, -7.2 kPa and -16.4 kPa in compression, and 2.4 kPa and 0.9 kPa in shear, while the maximum stresses for tofurky were 28.5 kPa, -38.3 kP, and 5.5 kPa. To discover the mechanics that best explain these data, we consulted two constitutive neural networks of Ogden and Valanis-Landel type. Both networks robustly discover models and parameters to explain the complex nonlinear behavior of artificial and real meat for individual tension, compression, and shear tests, and for all three tests combined. When constrained to the classical neo Hooke, Blatz Ko, and Mooney Rivlin models, both networks discover shear moduli of 94.4 kPa for tofurky, 35.7 kPa for artificial chickn, and 21.4 kPa for real chicken. Our results suggests that artificial chicken succeeds in re-producing the mechanical properties of real chicken across all loading modes, while tofurky does not, and is about three times stiffer. Strikingly, all three meat products display shear softening and their resistance to shear is about an order of magnitude lower than their resistance to tension and compression. We anticipate our study to inspire more quantitative, mechanistic comparisons of artificial and real meat. Our automated-model-discovery based approach has the potential to inform the design of more authentic meat substitutes with an improved perception of taste, with the ultimate goal to reduce environmental impact, improve animal welfare, and mitigate climate change, while still offering the familiar taste and texture of traditional meat. Our source code, data, and examples will be available at https://github.com/LivingMatterLab/CANNs.

bioengineering↗

Contrast Solution Properties and Scan Parameters Influence the Apparent Diffusivity of Computed Tomography Contrast Agents in Articular Cartilage

The inability to detect early degenerative changes to the articular cartilage surface that commonly precede bulk osteoarthritic degradation is an obstacle to early disease detection for research or clinical diagnosis. Leveraging a known artifact that blurs tissue boundaries in clinical arthrograms, contrast agent diffusivity can be derived from computed tomography arthrography (CTa) scans. We combined experimental and computational approaches to study protocol variations that may alter the CTa-derived apparent diffusivity. In experimental studies on bovine cartilage explants, we examined how contrast agent dilution and transport direction (absorption vs. desorption) influence the apparent diffusivity of untreated and enzymatically digested cartilage. Using multiphysics simulations, we examined mechanisms underlying experimental observations and the effects of image resolution, scan interval and early scan termination. The apparent diffusivity during absorption decreased with increasing contrast agent concentration by an amount similar to the increase induced by tissue digestion. Models indicated that osmotically induced fluid efflux strongly contributed to the concentration effect. Simulated changes to spatial resolution, scan spacing and total scan time all influenced the apparent diffusivity, indicating the importance of consistent protocols. With careful control of imaging protocols and interpretations guided by transport models, CTa-derived diffusivity offers promise as a biomarker for early degenerative changes.

bioengineering↗

Non-ionic CT Contrast Solutions Rapidly Alter Bovine Cartilage and Meniscus Mechanics

ObjectiveTo evaluate effects of a common CT contrast agent (iohexol) on the mechanical behaviors of cartilage and meniscus. MethodsIndentation responses of juvenile bovine cartilage and meniscus were monitored following exposure to undiluted contrast agent (100% CA), 50% CA/water, 50% CA/Phosphate Buffered Saline (PBS) or PBS alone, and during re-equilibration in PBS. The normalized peak force [Formula], effective osmotic strain ({varepsilon}osm), and normalized effective contact modulus [Formula] were calculated for every cycle, with time constants determined for both exposure and recovery via mono- or biexponential fits to [Formula]. ResultsAll cartilage CA groups exhibited long-term increases in [Formula] following exposure, although the hyperosmolal 100% CA and 50% CA/PBS groups showed an initial transient decrease. Meniscus presented opposing trends, with decreasing [Formula] for all CA groups. Re-equilibration in PBS for 1hr after exposure to 100% CA did not produce recovery to baseline [Formula] in either tissue. The recovery time for meniscus was substantially longer than that of cartilage. [Formula] increased with CA exposure time for cartilage but decreased for meniscus, suggesting an increased effective stiffness for cartilage and decreased stiffness for meniscus. Long-term changes to{varepsilon} osm in both tissues were consistent with changes in [Formula]. ConclusionExposure to iohexol solutions affected joint tissues differentially, with increased cartilage stiffness, likely relating to competing hyperosmotic and hypotonic interactions with tissue fixed charges, and decreased meniscus stiffness, likely dominated by hyperosmolarity. These altered tissue mechanics could allow non-physiological deformation during ambulatory weight-bearing, resulting in an increased risk of tissue or cell damage.

bioengineering↗

Osmotic Swelling Responses are Conserved Across Cartilaginous Tissues with Varied Sulfated-Glycosaminoglycan Contents

The interactions between the negatively charged sulfated glycosaminoglycan (sGAG) chains and the ionic interstitial fluid in articular cartilage and meniscal fibrocartilage give rise to an osmotic swelling stress that is critical for the load-bearing capability of both tissues. This osmotic swelling stress is altered when the sGAG content is changed, as during progression of degenerative joint disease; understanding the influence of sGAG concentration on the osmotic swelling stress of cartilage and meniscus is important to enhance our understanding of physiology and disease. This study compared the effect of altered osmotic environments on the confined compression swelling behavior of bovine tissues spanning a range of sGAG concentrations: juvenile articular cartilage, juvenile and adult meniscus, and juvenile cartilage degraded to reduce sGAG content. The transient response to changes in bath conditions was evaluated for explants assigned to one of three compressive offsets (5%, 10%, or 15% strain) and one of three bath conditions (0.1X, 1X, or 10X Phosphate Buffered Saline). Our results show that relative responses to alterations to the osmotic environment are consistent across tissue types, demonstrating that the role of sGAG in the swelling properties of the tissues tested is conserved, even when sGAG is present at low concentrations. Additionally, this study found unexpected correlations across tissue types between sGAG and collagen contents and between the aggregate modulus and both sGAG and collagen contents. These results suggest some conservation of composition-function relationships across a range of tissue types.

bioengineering↗