Competitive displacement of sodium caseinate by low-molecular-weight emulsifiers and the effects on emulsion texture and rheology.

Low-molecular-weight (LMW) emulsifiers are used to promote controlled destabilization in many dairy-type emulsions in order to obtain stable foams in whippable products. The relation between fat globule aggregation induced by three LMW emulsifiers, lactic acid ester of monoglyceride (LACTEM), saturated monoglyceride (GMS), and unsaturated monoglyceride (GMU) and their effect on interfacial protein displacement was investigated. It was found that protein displacement by LMW emulsifiers was not necessary for fat globule aggregation in emulsions, and conversely fat globule aggregation was not necessarily accompanied by protein displacement. The three LMW emulsifiers had very different effects on emulsions. LACTEM induced shear instability of emulsions, which was accompanied by protein displacement. High stability was characteristic for emulsions with GMS where protein was displaced from the interface. Emulsions containing GMU were semisolid, but only low concentrations of protein were detected in the separated serum phase. The effects of LACTEM, GMS, and GMU may be explained by three different mechanisms involving formation of interfacial α-gel, pickering stabilization and increased exposure of bound casein to the water phase. The latter may facilitate partial coalescence. Stabilizing hydrocolloids did not have any effect on the LMW emulsifiers' ability to induce protein displacement.

Technical note: Effects of frozen storage on the mechanical properties of the suspensory tissue in the bovine claw.

It is proposed that a softening of the suspensory tissue in the claw is involved in the development of lameness and claw lesions in cattle. A relatively small amount of research has been carried out to verify this theory. Research in this area would be simplified if mechanical testing of the suspensory tissue could be performed on frozen and stored specimens. The current study tested whether freezing of the specimens changes the suspensory tissues' mechanical properties. Limbs from 3 freshly slaughtered Danish Holstein dairy cows and 6 nonpregnant Angus heifers, without clinical signs of lameness, were allocated to 1 of 2 treatments (frozen or nonfrozen) in such a way that each cow was represented in each treatment group with a frozen limb and a corresponding nonfrozen limb (i.e., frozen left front, fresh right front, and so on). The frozen limbs were kept at -18°C for a week before processing and the nonfrozen limbs were processed within 2h of slaughter. Two samples measuring 8 × 8 mm were cut from the abaxial side of each claw in such a way that the sample included the horn of the abaxial wall, pedal bone, and the interposed corium. The samples were kept on ice until being mounted in a large deformation rheometer with an extension testing frame, fixed by the horn and the pedal bone, and loaded to failure. During deformation force and displacement data were recorded, from which corresponding stress and strain were calculated. Young's modulus (a measure of tissue elasticity or stiffness) and a measure of physiological support (PS; force needed to displace the sample 1mm) were calculated from the data. The response variables, Young's modulus and PS, were analyzed separately by a mixed model. The explanatory variables were treatment (frozen or nonfrozen), limb (front or back), claw (medial or lateral), position of the sample (dorsal or palmar-plantar), and group (Angus or Holstein). Interactions between group and treatment and between limb, claw, and sample position were included in the model. Cow identity was included as a random effect. Model reduction was performed by stepwise backward elimination, until all remaining terms were significant at the 5% level or less. Freezing had no effect on the elasticity of the suspensory apparatus or on PS. However, PS was affected by limb (hind legs had higher PS values than front) and the position of the sample (palmar-plantar samples had higher PS values than dorsal). The Angus group had higher PS values than the Holstein group, but the groups differed in age, parity, body weight, lactation, housing, and management, as well as in breed; therefore, further studies are needed to investigate these effects. The results indicate that mechanical testing of bovine claw suspensory tissue can be performed on specimens that have been frozen, thus aiding research in the mechanical aspect of bovine lameness and claw lesions.

Novel method for determination of myofibril fragmentation post-mortem.

Multi angle light scattering was used to determine the myofibril fragmentation of pig longissimus dorsi muscle which was then compared with results from the common turbidity method. The method is based on measurement of the myofibril particle size distribution with the use of a special optical unit containing several individual detectors. The method was able to determine post-mortem changes in a pig muscle homogenate without purification of the myofibrils and is therefore simpler and much faster than the traditional turbidity method. There was a significant correlation (p<0.01) between Warner-Bratzler shear force (WBSF) and particle size distribution. The root mean square error of prediction was found to be 6.1N (10-15% of the measured WBSF) when multivariate data analysis was used to make a prediction model for WBSF. Multi angle light scattering is very useful for estimation of myofibril fragmentation since the method is fast and the sample preparation is simple.

Distribution of hypertension and renal disease in Oregon.

Expecting to find agreement between the geographic distribution of hypertension and renal disease, we developed regional mortality rates for 1950-72 and prevalence rates for a Selective Service cohort born in 1939-41 and examined during 1957-69. For this purpose the State's counties were grouped into eight geographically homogeneous regions. The general decline in hypertension mortality was most pronounced in Portland, Oregon's major urban center. However, the decline halted during 1968-72 in the southern Cascade region which has become an area of relatively higher risk within the State. During these 23 years nephritis mortality fell, kidney infection mortality was stable, and both syndromes showed peak mortality in other, different regions of the State. The geographic pattern of hypertension prevalence among the draftee cohort resembled the 1963-67 hypertension mortality pattern, but more recent morbidity data are needed to confirm the southern Cascade region's recent change to a high-risk area. Of 529 draftees with diagnosed hypertension, only 35 percent of the cases were previously known, only 7 percent has had any previous treatment, and only 7 percent were associated with known renal conditions. Among 521 registrants with a history of renal disorders, the prevalence of hypertension was increased for all categories of renal disease but was significantly high only for those with a history of glomerulonephritis. To date in Oregon we have found no evidence that renal disorders are major determinants of hypertension morbidity or mortality.