A VERSATILE FOOD RHEOMETER

A new texture test instrument is described that applies linear or rotary deformations, singly or in combination, to food samples. A range of texture test cells and mixing, consistometer or viscometer attachments are adaptable to this apparatus so that many test methods presently used to measure the properties of foods can be performed with the instrument. Different transducers can be installed to detect force, torque, deformation and deformation rate, which are precisely recorded electronically. Environmental and sample temperature controls are built into the equipment. Application of the apparatus is illustrated with measurements of consistency during the formation of wiener emulsions and the rupture property of the wieners.     

A SYSTEM FOR RECORDING DEFORMATIONS IN TEXTURE TESTS*

An instrumental technique is described for recording food deformation in texture tests. The time required for the applied force to change between two levels is accurately recorded in digital form. Constant deformation rates are used so that deformation is directly proportional to time. The new readout is demonstrated with springs and selected foods to indicate its performance and show the inaccuracies that occur when using strip-chart recorders to measure deformations. The response of the new system is adequate to test products with a deformability up to 3400 g mm^-1 at deformation rates up to 100 cm min^-1 with less than 3 % error.     

Inhibition of tomato pectin methylesterase by partially purified kiwi pectin methylesterase inhibitor protein

The inhibition of tomato pectin methylesterase (PME) by a recently discovered kiwi pectin methylesterase inhibitor (PMEI) is described. PME was consequently purified by CM Sephadex C-50, Concanavalin A-Sepharose 4 B and Mono S chromatography, and PMEI by Q-Sepharose and Sephacryl S-200 chromatography. Inhibition of tomato PME activity under optimal conditions (0.125 m NaCl, pH 7.5) by partially purified kiwi PMEI (MW of 27 kD, pI ≥ 3.67) was independent of the PMEI/PME ratio between 36 and 61% of the maximal uninhibited activity. the non-competitive inhibition observed was optimal in the pH range of 5 to 7. PMEI was inactivated by heating to 120°C, and showed actinidin-like activity towards N-α-benzyloxycarbonyl-L-lysine p -nitrophenyl ester (CBZ-lys-ONp) and azocasein which was partially inhibited by the protease inhibitor leupeptin.     

A COMPARISON OF PROTEIN ASSAYS FOR THE DETERMINATION OF THE PROTEIN CONCENTRATION OF BEER

Seven protein assays have been compared for determination of the protein content of beer. Dialysis and ultrafiltration have been used to investigate possible interference and the protein content of the samples has been simultaneously monitored by sodium dodecyl sulphate-polyacrylamide gel electro-phoresis. The Fisons NA2000 Nitrogen/Protein Analyzer gave identical results to the standard Kjeldahl method but both measure nitrogen-containing compounds rather than protein. Colorimetric methods based upon the biuret reaction (including the Lowry and bicinchoninic acid protein assays) are particularly prone to interference from reducing substances and gave protein concentration values dependent upon the sample volume. The protein dye-binding assays (Coomassie Brilliant Blue and pyrogallol red-molybdate methods) were optimal for beer protein analysis displaying minimal inter ference and giving reproducible protein concentration values consistent with the protein content of the beers as indicated by electrophoresis.     

An NMR pulsed field gradient study of the electrical and conventional heating of carrot

Experiments have been carried out using pulsed field gradient NMR to characterize the self-diffusion of water within samples of carrot, both uncooked and cooked by either volumetric electrical or conventional heating. The method detected the presence of structure within uncooked carrot, and the disappearance of the structure on cooking. The NMR data were fitted to two models: (i) an analytical solution for diffusion between impermeable barriers and (ii) a numerical solution to the more physically realistic situation of diffusion between permeable barriers. The barrier spacings obtained with raw carrot data using both methods (i) and (ii) were consistent with cell sizes found in carrots. The effect of cooking on the model fit was either an increase in barrier spacing (method i), or an increase in barrier permeability (method ii). There was a statistically significant difference between samples cooked electrically and conventionally, but this was much less than the difference between cooked and uncooked material.     

2-Pyrazoline Dyes for Wool and Nylon

A range of yellow fluorescent 2-pyrazoline acid dyes has been synthesized. Their spectral and dyeing properties (on wool and nylon) depend both on the nature of the substitution pattern of the dye and on the nature of the fibre substrate. Exhaustion and fastness to washing, which are better on nylon than on wool, are improved by substituents attached to the 2-pyrazoline ring. Fastness to light is independent of the fibre and is increased by substituents on the 4- and 5- positions of the 2-pyrazoline ring. The fastness properties of the pyrazoline dyes were compared with those of C.I. Acid Yellow 7.     

MEASUREMENT OF PEA TENDERNESS

Abstract Twenty one tenderometers were compared in processing plants for their accuracy of measurement using wax wafers as the test material. The results indicate that there are serious differences among the tenderometers and that the accuracy of measurement is unsatisfactory for the purpose of grading peas to establish the price paid to the grower. If a relationship of compatible trust is to remain between the processor and the grower, serious consideration must be given either to better calibration of currently used tenderometers or to devising some other method of grading and paying for peas.     

Phase Equilibria in System CaO-CO2-H2O and Related Systems, with Implications for Crystal Growth of Calcite and Apatite

Conditions for crystallization of calcite from melts in the presence of a vapor or gaseous phase are reviewed to provide possible guidelines for growth of calcite. Phase equilibrium data for the system CaO-CO₂ show that to precipitate calcite from molten CaCO₃ the temperature must be above 1230° C and excess CO₂ must be present at pressures greater than 39.5 bars. Phase equilibrium data for the system CaO-CO₂-H₂O show that calcite can be precipitated from melts at 650°C in the presence of an aqueous vapor phase at 10 bars or more. Crystallization can be induced either by introducing temperature variations, or by changing the composition of the coexisting aqueous vapor phase under isobaric, isothermal conditions. The system CaO-MgO-CO₂-H₂O is used to show that doped calcite crystals, Ca_xR₁-_xCO₃, could be precipitated, with precisely controlled compositions, from melts in the system CaO-RO-CO₂-H₂O. Apatite phase relations are also presented.