THERMORESISTANCE OF PECTIN METHYLESTERASE IN SANGUINELLO ORANGE JUICE

The behavior of pectin methylesterase (EC 3.1.1.11) activity as a function of temperature was investigated in Sanguinello orange juice. The thermal inactivation of this enzyme was evaluated in the range of 75–95C and was found to be nonlinear. Due to very low activity content, after the thermal treatment at temperatures above 80C, the active enzyme was concentrated by affinity chromatography. The logarithmic values of decimal reduction times, plotted against temperature, showed a nonlinear pattern featuring a sudden change in slope at temperatures exceeding 85C. The z value determined in the range 85–95C was much higher than that calculated in the range 75–85 C. The decimal reduction times were used to estimate the times of treatment for the enzyme inactivation during a HTST process.     

RHEOLOGY OF SUCROSE-CMC MODEL SOLUTION

The rheological behavior of an aqueous solution composed of 65% sucrose and 0.1% CMC was experimentally determined from -10C to 50C using a rotational viscometer equipped with coaxial cylinders. The model solution behaved as pseudoplastic fluid, represented by the power-law model. Flow behavior and consistency indices determined at -10.1, 0.5, 9.8, 19.0, 30.1 and 50. OC, showed values between 0.79 to 0.86 and 0.15 to 10.22 Pa. sⁿ, respectively. The effect of temperature on the rheological parameters was represented by Arrhenius-type relationships, with R²≥ 0.97. They were compared to the rheological behavior of a concentrated orange juice with 65° Brix and 7% pulp content. The comparison of separate rheograms for both fluids showed that the model solution can be used to represent concentrated orange juice.     

NMR assessment of water uptake in different Vigna spp. seeds

Water uptake in seeds of ten wild and cultivated Vigna spp. accessions was investigated by NMR Spectroscopy. Water absorbed by the intact seeds was measured at intervals by changes in unabsorbed water using analysis of transverse magnetization decay of water protons. Widely different hydration kinetics of first and higher orders were found amongst the samples. the time required to reach saturation hydration capacity ranged from 3 to 16 h; total amount of absorbed water varied from 1.06 to 1.39g H₂O g⁻¹ sample and kinetic constant from 8.2 to 20.4 10⁻³ min⁻¹.
Accessions with a rough seed coat showed a fast water uptake within the first hour while some accessions smooth seed coat need an activation period of 1–5h.
No significant relationships were found between kinetic constant, absorbed water and protein content or some morphological characteristics (100 seed mass, length/width, width/thickness).
Wild species did not absorb water for days, an attribute related to biological survival, but after dehulling they absorbed water at similar rates to the cultivated cowpeas.
NMR can be a suitable technique to investigate some technological characteristics of legumes related to domestic and industrial processing (cooking, canning). It has potential to give data on the various forms of free and bound water, although this was not fully derived in the present work.     

Hydrophobic and Electrostatic Interactions on Extrusion of Protein Isolates

Lung protein isolates previously defatted by solvents of increasing polarity were extruded. Water monolayer values of these isolates, calculated from water vapor isotherms, showed a maximum when solvents of intermediate polarity were used. Shear resistance of the extruded products presented a similar behavior, with maximum values attained when the same solvents were employed to defat the isolates prior to extrusion. Phospholipid percentage in lipid fraction of the solvent extracts showed that minimum phospholipids were removed from the isolates when these solvents were used. The results suggested that the presence of phospholipid in the isolates after defatting could be important in improving the extrusion of these systems. Hydrophobic and electrostatic interactions between the macromolecules involved seemed therefore, to be relevant for the final texture obtained by extrusion.     

STARCH TRANSFORMATION DURING BANANA RIPENING: I — THE PHOSPHORYLASE AND PHOSPHATASE BEHAVIOR IN MUSA ACUMINATA

Starch levels as well as the phosphorylases and acid phosphatase activity during ripening of the banana fruit was investigated. The concentrations and sequence of appearance of sucrose, glucose and fructose were determined by use of specific enzymatic reactions. During the climacteric period, the phosphatase activity increased while phosphorylase activity, which initially increased before starch transformation began, thereafter decreased in a complex pattern. The starch was transformed into sucrose with later formation of glucose and fructose. Four bands of phosphorylase multiple forms, detected electrophoretically, did not change during ripening. One of them was able to synthesize a branched starch-using amylose as a primer and glucose 1 -phosphate as the substrate. Banana slices were infiltrated with water or solutions of cycloheximide or actinomycin D. Inhibition of phosphatase-induced activity was recorded only in the cycloheximide group. No change in phosphorylase activity was detected in any of these infiltrated groups. Sucrose production from starch was partially inhibited both by actinomycin D and cycloheximide. The aformentioned results were interpreted as indicating the previous presence of phosphorylase in the preclimacteric phase without new synthesis during ripening. The increase of activity of phosphatase was probably due to ribosomal synthesis rather than to nucleic acid synthesis.     

ENERGY CONSUMPTION IN A CONCENTRATED ORANGE JUICE PLANT

The consumption of electricity and thermal energy for frozen concentrated orange juice (FCOJ) and citrus pulp pellets (CPP) was determined in a plant. Thermal energy accounted for 90% of the total energy consumption in the plant and its consumption for CPP exceeded that for FCOJ. The kilocalories of thermal energy per kg of water evaporated (KKWE) in the evaporators increased as the feed rate of single strength juice was decreased. At the design evaporation capacity, the steam efficiency of two tubular evaporators and two plate evaporators was found to be 0.85N and 0.82N, respectively; N being the number of effects of the evaporator. Fouling of the waste heat evaporator was a major reason for the high energy consumption in the CPP unit.     

FLOW BEHAVIOR OF GUAVA PUREE AS A FUNCTION OF TEMPERATURE AND CONCENTRATION

Flow behavior of guava puree was determined with a tube viscometer. The puree samples (9.8-16.0° Brix) exhibited shear-thinning behavior. The flow behavior index of the power law model was nearly constant for all the samples over a temperature range of 25-60°C; its mean value was 0.43 with a standard deviation of 0.031. The apparent viscosity decreased with increase in temperature and the activation energy offlow was found to be 3.7 kcallg mole. The apparent viscosity increased as the concentration of the purees was increased; the increase was proportional to concentration raised to a power of 2.7. The Mizrahi-Berk model described well the flow data of the purees. The magnitude of the shear rate exponent was about 0.48, indicating that the purees were suspensions in shearthinning media.     

A study of chlorophyll-like and phycobilin pigments in the C endosymbiont of the apple- snail <i>Pomacea canaliculata</i>

Pigments present in the brown-greenish C morph of an intracellular endosymbiont of Pomacea canaliculata were investigated. Acetone extracts of the endosymbiotic corpuscles showed an absorption spectrum similar to that of chlorophylls. Three fractions obtained from silica gel column chromatography of the acetone extracts (C_I , C_II and C_III ), were studied by positive ion fast atom bombardment-mass spectrometry (FAB–MS) and hydrogen-nuclear magnetic resonance (H-NMR). Results indicated the presence of (1) a sterol in the yellow colored C_I fraction; (2) a mixture of pheophorbides a and b in the major green fraction, C_II; and (3) a modified pheophorbide a in the smaller green fraction, C_III . Aqueous extracts of the C endosymbiont did not show evidence of the occurrence of C-phycocyanin, allophycocyanin or phycoerithrin (light absorption, fluorescence emission, and electrophoresis of the protein moieties) while cyanobacterial cells (Nostoc sp.) showed evidence of C-phycocyanin and allophycocyanin. The possible phylogenetic and functional significance of the pigments present in the C endosymbiont is discussed.     

Lipid Protein Interactions in Offal Protein Isolates: Effect of Several Solvents on Lipid Extraction

The effect of solvents of increasing polarity on lipid extraction of bovine lung and rumen proteins, isolated by two different procedures, namely, alkaline solubilization of the protein followed by its isoelectric precipitation, and sodium dodecyl sulfate solubilization of the protein and its subsequent precipitation by ferric chloride was studied. A hyperbolic relationship was observed between the amount of lipid extracted and the dielectric constant of the solvent used. This relationship was described by an equation which allowed the calculation of the total amount of lipids present in the isolates and the average intensity of the interaction between lipids and proteins in each system. Relative composition of fatty acids in lung isolates showed marked dependence on the polarity of the solvent employed.     

Soil and Sun angle interactions on partial canopy spectra

Abstract

The spectral behaviour of an incomplete cotton canopy was analysed in relation to solar zenith angle and soil background variations. Soil and vegetation spectral contributions towards canopy response were separated using a first-order interactive model and consequently used to compare the relative sensitivity of canopy spectra to soil background and solar angle differences. Canopy reflectance behaviour with solar angle increased, decreased or remained invariant depending on the reflectance properties of the underlying soil. Sunlit and shaded soil contributions were found to alter vegetation index behaviour significantly over different Sun angles.