QUALITY OF MEAT PRODUCTS DURING REFRIGERATED AND ULTRA-CHILLED STORAGE

Standard domestic refrigerators store food between 1 and 5C (33.8–41F). A manufacturer recently developed a refrigerator capable of storing food in the “ultra‐chilled region” (?3 to ?7C) and claimed that storage of fresh meat in this region better maintains quality. To understand quality in terms of chemical reaction rates, microbial growth and texture and flavor changes, three common consumer meat products – steak, ground beef patty and salmon – were stored for a selected period of time, as determined by microbial testing, in five refrigerator models with different environmental conditions (constant temperature and temperature fluctuation). At the end of the storage period, consumer panelists assessed the quality of the cooked samples by ranking them according to preference. In addition, instruments were used to measure the color and shear cutting force (for steak only) of each sample. Results from the consumer Ranking R‐Index Test indicate that panelists preferred samples stored under or near ultra‐chilled conditions rather than samples stored under standard refrigerated conditions. The ultra‐chilled samples not only had higher panelist rankings and more favorable comments, but also had lower microbial aerobic plate counts. The instrument readings, however, highly varied and did not correlate well with sensory data.     

THE THROMBORESISTANCE OF A HEPARIN-POLYVINYL ALCOHOL HYDROGEL†

Heparin immobilized onto polyvinyl alcohol (PVA) by action of glutaraldehyde has been shown to be biologically active in a novel parallel flow arteriovenous shunt in dogs. The hepann-PVA hydrogel originally devised by Merrill and his collaborators was applied as a coaling to chromic acid etched polyethylene lubing. A pair of Y-connectors was used to divert < 2% of the flow in the AV shunt through the heparinized tube, which remained patent for longer Ihan two hours while a control tube without heparin was occluded within 30 minutes at a main shunt flow rate of ～l50mL/min. This enhanced patency was achieved without significant release from the surface, consistent with earlier experiments attributing the thromboresistance of the heparin-PVA hydrogel to the formation of a surface bound inactive thrombin-antithrombin III complex. Radiolabelled thrombin adsorbed onto beads made from the gel was readily displaced by arvinized plasma, indicating that the inactive complex was not itself permanently bound to the surface.

These results demonstrate the utility of Merrill's hydrogel for preparing materials with potential long lerm thromboresistance and for testing the validity of the hypothesized limitations to the long term use of immobilized heparin.     

Immunohistochemistry of GluR1 subunits of AMPA receptors of rat cerebellar nerve cells

The localization of GluR1 subunits of ionotropic glutamate receptors in the glial cells and inhibitory neurons of cerebellar cortex and their association with the climbing and parallel fibers, and basket cell axons were studied. Samples of P14 and P21 rat cerebellar cortex were exposed to a specific antibody against GluR1 subunit(s) of AMPA receptors and were examined with confocal laser scanning microscopy. GluR1 strong immunoreactivity was confined to Purkinje cell and the molecular layer. Weak GluR1 immunoreactivity was observed surrounding some Golgi cells in the granule cell layer. Intense GluR1 immunoreactivity was localized around Purkinje, basket, and stellate cells. Purkinje cells expressed strong GluR1 immunoreactivity surrounding the cell body, primary dendritic trunk and secondary and tertiary spiny dendritic branches. Marked immunofluorescent staining was also detected in the Bergmann glial fibers at the level of middle and outer third molecular layer. Positive immunofluorescence staining was also observed surrounding basket and stellate cells, and in the capillary wall. These findings suggest the specific localization of GluR1 subunits of AMPA receptors in Bergmann glial cells, inhibitory cerebellar neurons, and the associated excitatory glutamatergic circuits formed by climbing and parallel fibers, and by the inhibitory basket cell axons     

The effect of varying the calcium-sequestering salt cation on the hydration behaviour of rennet caseins in a simple model system

Di potassium orthophosphate and di-ammonium orthophosphate were used to replace di-sodium orthophosphate in a simple model of cheese analogue manufacture. Rheological changes that occurred as eight rennet caseins, possessing widely differing hydration behaviour, were dispersed in solutions of the different calcium-sequestering salts were determined. Dispersion in the potassium salt resulted in minor differences in hydration behaviour of rennet caseins when compared to the behaviour in di-sodium orthophosphate solution, while dispersion in the ammonium salt resulted in considerably modified hydration behaviours and rheological profiles.     

The compositional and functional properties of commercial mozzarella, cheddar and analogue pizza cheeses

The compositional and functional properties of commercial retail and/or wholesale samples (n = 8) of low-moisture mozzarella, cheddar and analogue (pizza) cheeses were compared. Inter-and intravariety differences were evident with intravariety differences in composition being relatively large for the analogue cheese. Cheddar had the lowest mean pH and level of expressible serum and the highest mean levels of proteolysis, expressible fat, and serum calcium and nitrogen (p < 0.05). Compared to mozzarella, the analogue cheeses had significantly lower (p < 0.05) mean levels of total protein and serum calcium, higher levels of total calcium and higher cheese pH. The mean stretchability of the melted mozzarella cheese was significantly higher than that of the melted cheddar or analogue cheeses. The melted cheddar had the highest mean flowability and lowest mean apparent viscosity (p < 0.05). The mean flowability and apparent viscosity of the analogue cheese were numerically lower and higher, respectively, than those of mozzarella.     

The role of homogenization in the manufacture of halloumi and mozzarella cheese from recombined milk*

When halloumi and mozzarella cheese are made from normal recombined milk, neither product exhibits the characteristic stretch and melt behaviour of the fresh milk cheeses. The present study demonstrates that this problem may be overcome either by using low homogenization pressures to prepare the recombined milk or by coating the fat in the recombined milk emulsion with phospholipid and homogenizing at the usual pressure. The influence of homogenization of milk on the properties of the cheese is discussed in terms of a polymer network model.     

Sintering of ZrO2 in HCl Atmospheres

Pure zirconia fired in HCl shows greatly reduced shrinkage compared to the same material fired in air. One of the main microstructural differences is the much more rapid grain growth in the porous zirconia fired in HCl. The observed grain growth does not follow any simple growth law over the temperature range investigated. The grains grow up to a limiting particle size close to the initial agglomerate size arid appear to stop.     

Temperature Influence on Acetyllysine Interaction with Glucose in Model Systems due to Maillard Reaction

The interaction between N-α-acetyllysine and glucose was investigated in a dry cellulose matrix (1.8% moisture) at 40, 50 and 60°C and a_w 0.19-0.21. The loss in acetyllysine in 6 days at those temperatures was 22, 54, and 79%, respectively. The degradation data more clearly fit a double exponential function (Ae^BX+ Ce^DX) than the first order function, Ae^BX. An estimate of the activation energy of 36 kcal/ mol and a Q₁₀ of 5.5 was computed from second order rate constants for acetyllysine and glucose degradation. The increase in color followed zero order kinetics and indicated an activation energy of 44 kcal/mol for the presumed third phase of the Maillard reaction in the solid state.     

Remarks on the Economic Implications of Convergence

Convergence means different things to different people. Thispaper discusses two ways in which convergence is generally discussed:(i) the convergence of voice, video and data in telecommunicationsmarkets: and (ii) the convergence of the telecommunicationsand computer industries. In order to understand what types ofnew services will be offered and how industry structure willevolve, it is also necessary to understand the drivers of convergence.Although technological change has played a key role, it is justas important to emphasize other forces, such as regulatory factors.Finally, while some aspects of convergence should lead to increasedcompetition, others may not.