CHARACTERIZATION OF PROTEINASE CLASSES IN LANGOSTILLA (PLEURONCODES PLANIPES) AND CRAYFISH (PACIFASTACUS ASTACUS) EXTRACTS

Proteinases (EC 3.4.21-24) in langostilla extract and crayfish hepatopancreas were classified using site specific effectors or chelators for either serine, cysteine, aspartic or metallo classes. Azocasein hydrolysis by langostilla and crayfish preparations was inhibited 50% and 40%, respectively, when assayed in the presence of serine proteinase inhibitor, phenylmethylsulfonyl fluoride. A similar degree of inhibition was observed with a trypsin inhibitor. However, no inhibition occurred with a chymotrypsin inhibitor. Less inhibition of azocasein hydrolysis, i.e., 20% and 14%, respectively, resulted with 1,10 phenanthroline. Inhibitors for cysteine and aspartic proteinases did not reduce the azocasein hydrolysis activities significantly. The amidase activity, with N-benzoyl-DL-Arg-p-nitroanilide as substrate was more sensitive, in both extracts, to serine proteinase inhibitors than the azocasein hydrolase activity. Results showed the presence of serine proteinases, i.e., trypsin but not chymotrypsin, as the major component and some minor activity of metallo dependent proteinases in the decapods extracts. Zymograms obtained after SDS-PAGE showed a dozen proteinases in each extract. Some of them were inhibited by a serine proteinase inhibitor and two to three were inhibited by 1,10 phenanthroline, supporting the results of the test tube proteinase activity assays. Furthermore, the reported technique for zymograms allowed direct comparison between extracts and provided information about their composition and the molecular weight of the targeted enzymes.     

Viability of probiotic micro-organisms (Lactobacillus casei Shirota and Bifidobacterium animalis subspp. lactis) in a milk-based dessert with cranberry sauce

The objective of this study was to evaluate the survival of two probiotic micro-organisms, Lactobacillus casei Shirota and Bifidobacterium animalis subspp . lactis , in a milk-based dessert (2.7% fat) with cranberry sauce added. B. lactis had a final concentration of 1.99 × 10⁶ cfu/g after 21 days of study, with a logarithmic decrease of 8.87%. On other hand, L. casei Shirota had a final concentration of 2.05 × 10⁷ cfu/g at the end of the same period, a logarithmic decrease of 8.41%. Statistical analysis showed that significant differences existed between both micro-organisms and over various storage times, the more viable micro-organism being L. casei Shirota , which decreased less than one logarithmic cycle after 21 days.     

Review: Studies on the reproductive and developmental biology of <I>Cichlasoma dimerus</I> (Percifomes,Cichlidae)

Many characteristics of the South American teleost fish Cichlasoma dimerus (body size, easy breeding, undemanding maintenance) make it amenable to laboratory studies. In the last years, many of the fundamental aspects of its reproductive and developmental biology have been addressed in our laboratory. Rather recently, the immunohistochemical localization of pituitary hormones involved in reproduction and in background color adaptation has been described in both adult and developing individuals, and the role of FSH in ovarian differentiation has been established. These findings have been correlated with mapping of some of their brain-derived controlling hormones. The latter include brain-derived gonadotropins which were shown to be active in vitro in the control of pituitary hormone secretions. The emerging picture shows C. dimerus as an interesting species in which many of their basic features have already been investigated and which conform a solid platform for comparative studies correlating neurohormones, pituitary hormones and behavior, from the molecular to the organismic level.     

STUDY OF TEXTURE AND GLASS TRANSITION OF FRENCH FRIED POTATOES PRETREATED WITH SOAKING SOLUTIONS

The objective of this work was to study the effects of soaking pretreatments, frying time and temperature, and oil content on texture and glass transition properties of French fried potatoes. Sodium chloride and total sugar contents showed a significant difference (P<0.05) between soaked samples and an unsoaked control. Texture parameters such as rigidity, work and maximum force showed that, up to 2 min offrying, these values decreased. Thereafter, there was a significant increase in these values as frying time increased beyond 3 min as confirmed by a Taguchi statistical analysis.
Glass transition temperature (Tg) was higher at the crust than in the strip center for all products and a control sample. This may have been due not only to differences in water content, but also dependent on the presence of other molecules that may have acted as plasticizers. As expected, the extent of starch gelatinization was greater at the crust for all treatments.     

Anticorrosives, encapsulates, catalytic supports and other novel nanostructured materials

A phenolic-formaldehydic resin (PFR) of the Novolac-type and modified through the attachment of carboxylic end groups (MPR), is used to tailor the morphological and optical properties of sol–gel synthesized silica materials. Silica microparticles are produced from alkoxide precursors in the presence of PFR or MPR resins, leading to a final material consisting of SiO₂ globules entangled inside a polymerized resin matrix. Under appropriate experimental conditions, chemical bonds can be established between the SiO₂ silanol surface groups and the MPR carboxylic chains, to render SiO₂/MPR core-shell-type compounds. The presence of PFR or MPR resins during the sol–gel production of silica microspheres allows to control: (i) the sizes of final SiO₂ particles and (ii) the transparency or opacity properties of the final hybrid products. In this way, either opaque or transparent solid substrates can be obtained, depending on the amounts of reactants used to prepare the hybrid specimens. Solid MPR and SiO₂/MPR samples were characterized by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy to determine chemical and textural properties of the hybrid substrates. Under appropriate experimental conditions, chemical bonds could be established between the SiO₂ silanol surface groups and the MPR carboxylic chains, to render SiO₂/MPR core-shell-type compounds.     

EVALUATION OF FLUORESCENT IN SITU HYBRIDIZATION (FISH) AS A RAPID SCREENING METHOD FOR DETECTION OF SALMONELLA IN TONSILS OF SLAUGHTERED PIGS FOR CONSUMPTION: A COMPARISON WITH CONVENTIONAL CULTURE METHOD

The pork tonsils are an important carrier of Salmonella, which could be involved in the contamination of pork products during the slaughter process. This paper reports a 23S rRNA fluorescent in situ hybridization (FISH) method used as a rapid screening tool for Salmonella detection in tonsils of slaughtered pigs and its comparison with the conventional culture method. As a rapid screening method, the FISH technique would reduce the high volume of negative samples that are routinely analyzed, indicating presumptive positive samples in a real and practical time. The use of a Sal3 probe allowed the rapid (7 h) Salmonella detection in 16 (34%) of 47 naturally contaminated tonsils, without pre‐enrichment. Salmonella was isolated by the culture method in six samples that were also FISH‐positive samples, and FISH failed to identify only one of the culture‐positive samples. The results indicate the potential of this technique as a rapid screening method for detecting Salmonella in tonsils from pork slaughtered for consumption.     

Supercritical CO2 Conditions Affecting Extraction of Lipid and Cholesterol from Ground Beef

Ground beef was extracted by supercritical CO₂ (SC-CO₂) with pressure ranging from 103-310 bar at 30-50°C. Higher pressure was needed to increase yield of extracted lipid. The profile of cholesterol content for the fractionated lipid extracted at 172 bar or 310 bar was generally lower in the initial stage of extraction and increased with CO₂ used. DSC thermograms indicated that, depending upon extraction conditions, the distribution of lipid components of fractionated samples either shifted toward higher melting temperatures or concentrated those lipids melting between 5-25°C.