Mild Curing Conditions Research Articles

The Maillard Reaction as Source of Meat Flavor Compounds in Dry Cured Meat Model Systems under Mild Temperature Conditions

Flavor is amongst the major personal satisfaction indicators for meat products. The aroma of dry cured meat products is generated under specific conditions such as long ripening periods and mild temperatures. In these conditions, the contribution of Maillard reactions to the generation of the dry cured flavor is unknown. The main purpose of this study was to examine mild curing conditions such as temperature, pH and aw for the generation of volatile compounds responsible for the cured meat aroma in model systems simulating dry fermented sausages. The different conditions were tested in model systems resembling dry fermented sausages at different stages of production. Three conditions of model system, labeled initial (I), 1st drying (1D) and 2nd drying (2D) and containing different concentrations of amino acid and curing additives, as well as different pH and aw values, were incubated at different temperatures. Changes in the profile of the volatile compounds were investigated by solid phase microextraction and gas chromatography mass spectrometry (SPME-GS-MS) as well as the amino acid content. Seventeen volatile compounds were identified and quantified in the model systems. A significant production of branched chain volatile compounds, sulfur, furans, pyrazines and heterocyclic volatile compounds were detected in the model systems. At the drying stages, temperature was the main factor affecting volatile production, followed by amino acid concentration and aw. This research demonstrates that at the mild curing conditions used to produce dry cured meat product volatile compounds are generated via the Maillard reaction from free amino acids. Moreover, in these conditions aw plays an important role promoting formation of flavor compounds.

Cationic UV-Curing of Epoxidized Biobased Resins.

Epoxy resins are among the most important building blocks for fabrication of thermosets for many different applications thanks to their superior thermo-mechanical properties and chemical resistance. The recent concerns on the environmental problems and the progressive depletion of petroleum feedstocks have drawn the research interest in finding biobased alternatives. Many curing techniques can be used to obtain the final crosslinked thermoset networks. The UV-curing technology can be considered the most environmentally friendly because of the absence of volatile organic compound (VOC) emissions and mild curing conditions. This review provides an overview of the state of the art of bio-based cationic UV-curable epoxy resins. Particular focus has been given to the sources of the bio-based epoxy monomers and the applications of the obtained products.

Network dynamics in cationically polymerized, crosslinked epoxy resins and its influence on crystallinity and toughness

Crystallinity in crosslinked epoxy resins is a rarely observed phenomenon. If crystallinity is properly adjusted, it can lead to enhanced toughness in cationically polymerized epoxy resins. This work demonstrates the controlled crystallization of partially crystalline poly(ɛ-caprolactone) (PCL) in a model system based on a cycloaliphatic epoxy matrix polymerized with a thermo-latent, cationic initiator. Samples with the same composition were polymerized under varied conditions leading to different degrees of crystallinity and furthermore to differences in morphology and mechanical behavior. Mild curing conditions lead to a sufficient flexibilization of the epoxy matrix and the epoxide consumption is caused mainly by the activated monomer mechanism. On the other hand, more intense polymerization conditions result in a higher amount of transesterification compared to mild conditions which is evidenced by decreasing crystallinity and higher gel content despite a complete polymerization reaction. The PCL chains are shortened by transesterification while the smaller PCL chains are integrated into the network. Additionally, stress relaxation experiments measured with DMA and deformation-fixation-relaxation experiments reveal a type of flowing and stress reduction of the crosslinked polymers caused by rearrangement reactions. SEM micrographs show that increasing crystallinity leads to a raised roughness of fracture surfaces. Examination of the mechanical properties shows that enhanced crystallinity leads to higher stiffness, mechanical strength and also to superior toughness even if the network density does not significantly change. This work shows how the morphology and properties of the epoxy resin can be adjusted by just small variations in the polymerization conditions.

Synthesis and Characterizations of Melamine-Based Epoxy Resins

A new, easy and cost-effective synthetic procedure for the preparation of thermosetting melamine-based epoxy resins is reported. By this innovative synthetic method, different kinds of resins can be obtained just by mixing the reagents in the presence of a catalyst without solvent and with mild curing conditions. Two types of resins were synthesized using melamine and a glycidyl derivative (resins I) or by adding a silane derivative (resin II). The resins were characterized by means of chemical-physical and thermal techniques. Experimental results show that all the prepared resins have a good thermal stability, but differ for their mechanical properties: resin I exhibits remarkable stiffness with a storage modulus value up to 830 MPa at room temperature, while lower storage moduli were found for resin II, indicating that the presence of silane groups could enhance the flexibility of these materials. The resins show a pot life higher than 30 min, which makes these resins good candidates for practical applications. The functionalization with silane terminations can be exploited in the formulation of hybrid organic-inorganic composite materials.

Glyoxal as a Formaldehyde-Free Durable Press Reagent for Mild Curing Applications'

The combination of aluminum sulfate and an α-hydroxy acid has proven highly effective in catalyzing the crosslinking of cotton cellulose by glyoxal under mild curing conditions. The durable press appearance ratings were increased by the presence of ethylene glycol as a coreactive additive, and a silanol-terminated silicone as softener. An unusual effect was observed with longer chain glycols, which cannot form 1:1 cyclic adducts with glyoxal as ethylene glycol does. The added glycols appeared to increase the efficiency of cellulose crosslinking by glyoxal, so that quite low curing temperatures and catalyst concentrations could be used. A preferential absorption and interaction of glyoxal with the cellulose may have occurred during the drying step to form complex cellulose hemiacetals, which subsequently interacted with added glycols to give the final crosslink structures during the heat cure. With diethylene glycol as eoreactant for glyoxal in a 1:1 mole ratio, curing at 1.15°C was effective in imparting a durable press rating of 4.0 with 298° conditioned wrinkle recovery (w + f) and 46-48% breaking or tearing strength retention in cotton printcloth. Fabric whiteness was equal or superior to that with dimethyloldihydroxyethyleneurea applied by a conventional pad-dry-cure treatment with magnesium chloride catalysis.

Diisocyanate Vulcanization of 1-Chlorobutadiene-Butadiene Rubber

Abstract TDI-d was found to react quantitatively with hydroxyl group in CB-BR under relatively mild curing conditions to give CB-BR vulcanizates, while AEP afforded vulcanizates having a certain amount of pendent AEP. The latter could be used to increase the network-chain density by postcuring with TDI. This crosslink formation was found to proceed almost quantitatively through the reaction of pendent AEP and hydroxyl groups with equimolar amounts of TDI in CB-BR under suitable curing conditions.

Moderated Mineral Acid Catalysis for Durable-Press Finishing Under Mild-Curing Conditions 1

Mineral acids are effective catalysts in mild-cure finishing treatments for producing wrinkle resistance in cotton fabrics. In these treatments fabrics are impregnated with a solution containing an N-methylolated amide crosslinking agent and the catalyst, and heated without predrying, at 60-100°C for a short time. The heating is regulated so that the moisture content of the fibers at the end of the crosslinking treatment is about 3-5%. However, because of the potentially corro sive effect on equipment and the precise control necessary during treatments that utilize mineral acid catalysts, other catalyst systems have been sought. The present approach has been to modify the activity of the mineral acid by in cluding a moderating salt in the catalyst system. Certain acid/salt combinations that provide sufficient catalytic activity for mild-cure finishing were developed. The catalyst systems used were HCl/NH4H2PO 4, HCl/NH4C2H3O2, and HNO 3/ NH4H2PO4. Treatments utilizing these catalysts gave fabrics with greater strength but lower wrinkle- and chlorine- resistance than those receiving treatments catalyzed by mineral acid alone. Magnitude of the changes varied with concentrations and relative amounts of acid and salt in the catalyst system; quantities for optimum relationships were established.