/sup 1/H, /sup 19/F and /sup 11/B nuclear magnetic resonance characterization of BF/sub 3/:amine catalysts used in the cure of C fiber-epoxy prepregs

The chemical composition of commercial BF/sub 3/:amine complexes are variable and contain BF/sub 4//sup -/ and BF/sub 3/(OH)/sup -/ salts together with other unidentified highly reactive species. The BF/sub 3/:amine complexes, which are susceptible to hydrolysis, also partially convert to the BF/sub 4//sup -/ salt (i.e. BF/sub 4//sup -/NH/sub 3//sup +/C/sub 2/H/sub 5/) upon heating. This salt formation is accelerated in dimethyl sulfoxide solution and in the presence of the epoxides that are present in commercial prepregs. Commercial C fiber-epoxy prepregs are shown to contain either BF/sub 3/:NH/sub 2/C/sub 2/H/sub 5/ or BF/sub 3/:NHC/sub 5/H/sub 10/ species together with their BF/sub 4//sup -/ salts and a variety of boron-fluorine or carbon-fluorine prepreg species. Considerable variation in the relative quantities of BF/sub 3/:amine to its BF/sub 4//sup -/ salt was observed from prepreg lot to lot, which will cause variable viscosity-time-temperature prepreg cure profiles. It is concluded that the chemically stable and mobile BF/sub 4//sup -/ salt is the pre-dominant catalytic species, acting as a cationic catalyst for the prepreg cure reactions. During the early stages of cure the BF/sub 3/:amine catalyst converts to the BF/sub 4//sup -/ salt in the presence of epoxides, whereas the BF/sub 3/-prepreg species are susceptible to catalytic deactivation and immobilization

Parvalbumin in fish skin-derived gelatin: Is there a risk for fish allergic consumers?

The major allergen parvalbumin was purified from cod muscle tissues, and polyclonal antibodies were raised towards it. The antibodies were tested for specificity and an enzyme-linked immunosorbent assay (ELISA) was developed using these antibodies. The ELISA was applied to measure parvalbumin in cod skin, the starting material for fish gelatin made from deep sea, wild fish. The ELISA was sufficiently sensitive (LLOQ = 0.8 ng ml-1 in extracts, corresponding to 0.02 μg of parvalbumin per g of tissue), and did not cross-react with common food constituents. Fish gelatin, wine and beer, matrices for the potential use of this ELISA, did not cause disturbance of the assay performance. The data show that the parvalbumin content in cod muscle tissue is 6.25 mg g-1, while the skins contained considerably less, 0.4 mg g-1. Washing of the skins, a common industrial procedure during the manufacturing of fish gelatin, reduced the level of parvalbumin about 1000-fold to 0.5 μg g-1, or 0.5 ppm. From 95 commercial lots of fish gelatin it is shown that 73 are below 0.02 μg g-1 parvalbumin. From the other 22 lots, the one with the highest concentration contained 0.15 μg g-1 of parvalbumin. These levels are generally assumed to be safe for fish-allergic individuals. © 2012 Copyright Taylor and Francis Group, LLC

Effects of sugars and aminooxyacetic acid on the longevity of pollinated Oncidium Gower Ramsey flowers

The effects of sugars and aminooxyacetic acid (AOA) on the vase life of pollinated Oncidium Gower Ramsey flowers were investigated in this study. AOA was found to be an effective ethylene inhibitor as holding solutions containing 0.5 mM of AOA considerably prolonged the vase life of the flowers. The best treatment in delaying the senescence of pollinated Oncidium Gower Ramsey flowers were solutions of 4 sucrose + 0.5 mM AOA and 0.5 mM AOA. Both these treatments managed to delay the discolouration, furrowing and appearance of the veins up to nearly twice the length of time it took for the control flowers held in distilled water, to start senescing. The addition of glucose to the holding solution was not as effective as sucrose in delaying the senescence and prolonging the vase life of the flowers. Signs of senescence such as discolouration were measured using the Minolta chroma meter. Weight loss and pH of the holding solutions were also measured daily. AOA added in the solutions had a positive effect of lowering the pH of the holding solution thus inhibiting bacterial growth in the vial. A low pH also accounted for better water uptake by the flowers which delayed turgor loss and thus also delaying the wilting of the flowers