The rheological behaviour of blueberry cloudy juice (Vaccinium corymbosum L.), prepared from fresh berries, was studied as a function of solids concentration, in the range 25–61 °Brix, at different temperatures (5–50 °C), with a control rate (CR) rheometer. Cloudy juice was concentrated by vacuum evaporation, and solutions at other concentrations were prepared from the concentrate by adding the liquid collected as distillate. The juices were slightly thixotropic between 45 and 61°Brix. For lower concentrations, the thixotropy was low and could be easily eliminated by shearing. The power law model was applied to fit the pseudoplastic behaviour. The activation energy for flow, evaluated with the Arrhenius–Guzman equation, increased with solids concentration and ranged from 4.6 to 24 kJ gmol–1. A non‐linear correlation, accounting for temperature and concentration effects on the consistency coefficient, was identified.

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The skeletal isomerization of n-butenes over a chlorinated alumina catalyst has been studied, by operating under reaction−regeneration cycles in an isothermal fixed-bed integral reactor. The limiting values of the reaction and regeneration temperatures for avoiding irreversible deactivation by loss of chlorine have been determined. Reversible deactivation by deposition of coke, which is completely removable by combustion, is unavoidable. The effect of the operating conditions upon the deposition of coke and the deterioration of the porous structure as a consequence of the deposition have been analyzed.

: The e †ect upon kinetic behaviour (activity and selectivity) of the physical properties (pore volume distribution) and acidic characteristics (nature of acidic sites and acidic strength distribution) of acidic catalysts in the skeletal isomerization of n-butenes has been studied. The catalysts studied are the following : c-alumina, alumina modiÐed by introduction of F, Cl and Br, silicaÈalumina, HZSM-5 zeolite-based catalyst and SAPO-34-based catalyst. It has been proven that the selectivity of acidic catalysts towards the skeletal isomerization of nbutenes is the result of a compromise between pore shape selectivity and intrinsic selectivity of the acidic sites of di †erent strength, this latter property being more signiÐcant. Strong acidic sites are needed for the skeletal isomerization, but sites which are too strong produce important amounts of byproducts. A chlorinated alumina is a highly active and selective catalyst for skeletal isomerization.

We studied the rheological behaviour of apricot jam ( Prunus armeniaca) made with sucrose, and jams of bilberry ( Vaccinium myrtillus) and rose hips ( Rosa canina ) prepared for dietary usé with fructose in a temperature range of 5-65 °C. All three jams presented thixotropy, and the decrease in stress with time fit first order kinetics. The flow behaviour can be described by power equa tions and the Herschel-Bulkey équation. The relation between temperature and apparent viscosity was described with the Arrhenius-Guzman équation.