Biopackaging materials based on fish myofibrillar proteins have been developed. The effects of protein concentration, pH, temperature and storage time before casting on the apparent viscosity of the film forming solution (FFS) were evaluated using experimental design methodology. The first objective was to determine a feasible experimental range for film-forming. The pH and protein concentration had strong interactive effects on FFS viscosity. During FFS storage before casting, partial degradation of high molecular weight protein components led to decreased viscosity, allowing thin layer casting. In the experimental range for filmforming, none of the conditions affected film functional properties. Standard conditions were determined at: pH 3.0,2.Og protein/lOOg FFS, 25°C and 6 hr storage. The functional properties of the standard biopackaging were slightly better than those that determined for known protein-based films, with tensile strength close to those of low density polyethylene films.

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A sensitive and reproductible HPLC method to determine the reactive lysine content of films made from cottonseed flour was developed. This method is applied to follow the cross-linking of cottonseed proteins by formaldehyde, glutaraldehyde, or glyoxal. The cross-linking of these proteins resulted in the decrease of reactive lysine content within the film. The maximum puncture force of the films is correlated with the modified reactive lysine content after cross-linking treatments. Of the three cross-linking agents, formaldehyde was the most effective to enhance the maximum puncture force of the films despite its moderate reaction with only 50% of reactive lysine in the films. By contrast, glutaraldehyde, which reacted with nearly 100% of lysine, led to less resistant films. The results were interpreted as the impact of the molecular structure of the cross-link bridges on the mobility between protein chains. Keywords: Cross-linking; HPLC; cottonseed proteins; films; reactive lysine

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In view of utilizing the commercial enzyme Maltogenase for the production of maltose syrup in a continuous membrane reactor, some kinetic properties of this enzyme were investigated. Preliminary tests were conducted using Zulkowsky soluble starch as substrate. At pH 5.0 and 60°C, the Michaelis and Menten kinetic constants Vmax and KM were respectively 2.47mmol of maltose equivalents·min−1·dm−3 and 9.64g of Zulkowsky soluble starch·dm−3. Initial hydrolysis velocity was reduced at high starch concentrations and in the presence of maltose. When liquefied cassava starch (≈60 to 340g·dm−3) was used as substrate, hydrolysis kinetics was modelled by analyzing whole progress curves. A simple empirical modell was established and allowed satisfactory descriptions of the experimental data for the formation of maltose over time at large enzyme/substrate ratios.

Drying of natural rubber (NR) crumb (grade TSR10) requires high temperatures (100-120 • C). In order to determine the changes in bulk viscosity during the drying process, ageing kinetics at 120 • C were studied on model NR samples. During the process, changes in Mooney viscosity and weight-average molar mass (M W ) were monitored. Rubber from clones GT 1 and PR 107, with a bimodal inherent molar mass distribution (MMD 0 ), was degraded in a two-phase process. During the first phase, Mooney viscosity and M W increased, undoubtedly owing to a predominance of storage hardening over chain scissions [0 < t (min) < 120]. During the second phase, chain scissions predominated (t > 120 min) and Mooney viscosity and M W decreased. For rubber samples from clone PB 217, with a unimodal MMD 0 , no or reduced storage hardening was observed throughout the ageing process. These results showed that the key parameter involved in storage hardening seems to be the quantity of short polyisoprene chains and probably the nature of the chain ends.

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