Soy protein isolate extruded with high moisture retains high nutritional quality.

High-moisture extrusion of soy protein isolate generates a highly palatable meat substitute. No systematic evaluation of the nutritional quality of soy processed in this manner has been performed. This study compared the growth rate of male and female mice fed diets containing soy protein isolate without extrusion or with high-moisture extrusion. Other measures of overall growth and animal health were examined. Minor differences in the parameters were observed. Overall, the extruded soy protein was equally nutritious as the unextruded soy protein for the animals. Hence, high-moisture extrusion may be considered a useful method to generate high-quality protein foods. A longer term feeding trial may be recommended to further define the nutritional adequacy of this protein.

Protein-protein interactions during high-moisture extrusion for fibrous meat analogues and comparison of protein solubility methods using different solvent systems.

Soy protein, mixed with gluten and starch, was extruded into fibrous meat analogues under high-moisture and high-temperature conditions. The protein solubility of samples collected at different extruder zones and extrudates made with different moistures was determined by 11 extraction solutions consisting of 6 selective reagents and their combinations: phosphate salts, urea, DTT, thiourea, Triton X-100, and CHAPS. Protein solubility by most extractants showed decreasing patterns as the material passed through the extruder, but the solution containing all 6 reagents, known as isoelectric focus (IEF) buffer, solubilized the highest levels and equal amounts of proteins in all samples, indicating that there are no other covalent bonds involved besides disulfide bonds. With regard to relative importance between disulfide bonds and non-covalent interactions, different conclusions could be made from protein solubility patterns, depending on the type of extracting systems and a baseline used for comparison. The observation points out pitfalls and limitation of current protein solubility methodology and explains why controversy exists in the literature. Using the IEF buffer system with omission of one or more selective reagents is considered to be the right methodology to conduct protein solubility study and thus recommended. Results obtained with this system indicate that disulfide bonding plays a more important role than non-covalent bonds in not only holding the rigid structure of extrudates but also forming fibrous texture. The sharpest decrease in protein solubility occurred when the mix passed through the intermediate section of the extruder barrel, indicating formation of new disulfide bonds during the stage of dramatic increase in both temperature and moisture. After this stage, although the physical form of the product might undergo change and fiber formation might occur as it passed through the cooling die, the chemical nature of the product did not change significantly.

Single wire versus double wire loops for median sternotomy closure: experimental biomechanical study using a human cadaveric model.

BACKGROUND: Healing of median sternotomy requires reliable sternal fixation. Although both single and double wire kits are commercially available, no experimental study has compared the two closures in a human cadaveric model. We used a recently described human experimental cadaveric model to compare the stability of the closures. METHODS: Sixteen fresh adult human cadaveric sternal plates with adjacent ribs were fixed with custom designed spiked stainless steel clamps and attached to a biomechanical testing device. Single No. 5 peristernal and double peristernal closures were tested. The stability of the unions was tested using perpendicular, repetitive force loads increasing from 0 to 800 Newtons at a rate of 0.5 mm/second. RESULTS: The two study groups did not differ in age or sex. No clamp failures or damage to the specimens occurred. The double peristernal closure exhibited a significantly lower permanent displacement than the single wire group, suggesting a superior strength and stability of that closure. CONCLUSIONS: To the extent to which this human cadaveric model resembles in vivo median sternotomy, these data suggest that the biomechanical stability of the peristernal double wire closure may exceed that of single wires.

Alpha 2(I) collagen deficient oim mice have altered biomechanical integrity, collagen content, and collagen crosslinking of their thoracic aorta.

Collagen and elastin are the primary determinants of vascular integrity, with elastin hypothesized to be the major contributor to aortic compliance and type I collagen the major contributor to aortic strength and stiffness. Type I collagen is normally heterotrimeric composed of two alpha1(I) and one alpha2(I) collagen chains, alpha1(I)(2)alpha2(I). Recent investigations have reported that patients with recessively inherited forms of Ehlers Danlos syndrome that fail to synthesize proalpha2(I) chains have increased risks of cardiovascular complications. To assess the role of alpha2(I) collagen in aortic integrity, we used the osteogenesis imperfecta model (oim) mouse. Oim mice, homozygous for a COL1A2 mutation, synthesize only homotrimeric type I collagen, alpha1(I)3. We evaluated thoracic aortas from 3-month-old oim, heterozygote, and wildtype mice biomechanically for circumferential breaking strength (Fmax) and stiffness (IEM), histologically for morphological differences, and biochemically for collagen content and crosslinking. Circumferential biomechanics of oim and heterozygote descending thoracic aortas demonstrated the anticipated reduced Fmax and IEM relative to wildtype mice. Histological analyses of oim descending aortas demonstrated reduced collagen staining relative to wildtype aortas suggesting decreased collagen content, which hydroxyproline analyses of ascending and descending oim aortas confirmed. These findings suggest the reduced oim thoracic aortic integrity correlates with the absence of the alpha2(I)collagen chains and in part with reduced collagen content. However, oim ascending aortas also demonstrated a significant increase in pyridinoline crosslinks/collagen molecule as compared to wildtype ascending aortas. The role of increased collagen crosslinks is uncertain; increased crosslinking may represent a compensatory mechanism for the decreased integrity.

Hydrophobicity of bitter peptides from soy protein hydrolysates.

Soy peptides were characterized for flavor, chemical properties, and hydrophobicity to investigate their relationships with bitterness. Five peptide fractions ranging in average molecular mass from 580 to 11300 Da were fractionated by ultrafiltration from two commercial soy protein hydrolysates. The bitterness of fractionated peptides was related to molecular mass, with maximum bitterness observed at approximately 4000 Da for one hydrolysate and 2000 Da for the other. The bitterness increased as the peptide M(w) decreased to 3000 Da for the first hydrolysate and to 2000 Da for the second one and then decreased as the peptide M(w) decreased below 1000 Da. The peptide fraction with molecular mass of <1000 Da showed the lowest bitterness for both. The hydrophobicity data based on Q values do not support Ney's Q rule as a predictor of bitterness for soy peptides.

Biomechanical comparison of median sternotomy closures.

BACKGROUND: Poor healing of median sternotomy can significantly increase morbidity, mortality, and hospital costs. Effective union requires reliable sternal fixation. Although wire has proven the most reliable and widely used sternotomy closure material, no experimental studies have compared a large variety of wiring techniques in a human model. We developed an easily reproducible experimental model using cadaveric human sterna and compared several wiring methods to assess closure strength and stability. METHODS: Fifty-three fresh adult human cadaveric sternal plates with adjacent ribs were fixed with specially designed spiked stainless steel clamps and attached to a texture analyzer. Single peristernal and transsternal, alternating single peristernal and transsternal, figure-eight peristernal, figure-eight pericostal, and Robicsek closures using no. 5 stainless steel wires were tested. We evaluated bone density, stiffness, and displacement using perpendicular, repetitive variable force loads of 800 Newtons cycling at a rate of 0.5 mm/s. RESULTS: There were no significant differences in age, sex, or bone density in outcome measures of the sternal groups. No clamp failures or clamp damage to the specimens occurred. The single peristernal and alternating peristernal and transsternal closures proved superior in strength and stability (p < 0.001). The figure-eight peristernal, then the single transsternal, then the Robicsek were next stablest groups in decreasing order. The figure-eight pericostal closure had the highest failure rate (p < 0.001). CONCLUSIONS: This novel model of sternotomy closure testing was reliable, inexpensive, and easily reproducible. The mechanical stability of peristernal and alternating peristernal and transsternal wires was significantly greater than that of the other tested methods. Pericostal figure-eight closures were not sufficiently stable to be considered a reliable method of primary sternotomy repair.

Effects of processing conditions on the physical and chemical properties of buckwheat grit cakes.

Buckwheat grit cakes were prepared with a rice cake machine using the following independent variables: tempering moisture contents (15, 17, and 19%, wb), heating temperatures (240, 246, 252, and 258 degrees C), and heating times (5, 6, 7, and 8 s). Higher moisture, higher heating temperature, or longer heating time produced cakes with a higher cake specific volume. Cakes became lighter in color at a lower heating temperature or a shorter heating time. The hardest cake was produced at 252 degrees C for 5 s at 19% moisture content. The percent weight loss after tumbling decreased with increasing heating times and heating temperatures. Increased heating time resulted in more expanded products. The average rutin content decreased as the heating temperature or heating time increased. These results suggest that processing conditions, including tempering moisture, heating temperature, and heating time, significantly influenced physical and chemical qualities of buckwheat grit cakes such as specific volume, hardness, integrity, color, internal structure, and rutin content.

Biomechanical porcine model of median sternotomy closure.

BACKGROUND: Healing complications following median sternotomy commonly include instability, nonunion, and infection. They are associated with a high mortality rate if mediastinitis supervenes. Closure complications are best avoided by improving stability at the union, but there has thus far been no widespread agreement among surgeons about relative superiority among the available closure techniques. MATERIALS AND METHODS: A biological sternotomy closure model was developed utilizing whole porcine sterna. A special stainless-steel clamp with multiple spikes was created to reliably attach the sterna to a biomechanical testing device. RESULTS: Two wiring techniques, single peristernal and pericostal figure-eight, were used in 14 fresh cadaveric porcine sterna. The more rigid closure utilized single peristernal wires (P < 0.0001). There was no tissue associated with clamp spikes penetrating the specimen's layers, and there was no clamp displacement even at closure failure loads. CONCLUSIONS: The porcine sternotomy model is a valuable tool for comparing closure techniques based on geometrical and mechanical wiring patterns. The model's low cost and easy reproducibility make it a promising first step in sternotomy closure research. The stainless-steel clamp used in the porcine model provided reliable repeat specimen fixation.