No abstract

Scallop tropomyosin (TM), the major allergen of shellfish, was prepared from adductor muscles and reacted with four reducing sugars to investigate the effect of the Maillard reaction on the allergenicity of TM. The IgE-binding ability of TM increased significantly with the progress of the reaction with glucose, ribose, and maltose, but not with maltotriose. The allergenicity was enhanced at the early stage of the Maillard reaction, and the trend of the effect depended on the type of reducing sugar used. 2,4,6-Trinitrobenzenesulfonic acid treatment of the lysine residues in TM showed that the protein surface charge resulting from the Maillard reaction had no effect on the enhancement of the allergenicity. Thus, the change in the allergenicity would be closely related to the structural change caused by the Maillard reaction.

The effect of the Maillard reaction on the allergenicity of squid tropomyosin (TM) was investigated. When TM was reacted with ribose (TM-ribose), its human-specific IgE-binding ability decreased markedly and alpha-chymotryptic digestibility of TM was also altered at the early stage of the Maillard reaction. On the other hand, the modification of the lysine residues in TM using 2,4,6-trinitrobenzenesulfonic acid had no effect on the allergenicity and alpha-chymotryptic digestibility of TM. Therefore, the structural change in TM induced by the Maillard reaction would cause the reduction of the allergenicity, rather than the block of lysine residues. Although peptic digestion diminished the specific IgE-binding ability of TM, the reduction of the allergenicity by the Maillard reaction remained after peptic digestion. These results suggest that hypersensitive reaction of TM-ribose in the human body might be lower than that of native TM.

Neoglycoprotein was prepared from carp myofibrillar protein by using the Maillard reaction with glucose, and its solubility in a high ionic strength medium, Ca-ATPase activity, and emulsifying properties were investigated. For reacting with glucose, the lyophilized protein mixed with glucose (the weight rate:  1:9) was incubated at 40 °C (for 24 h), 50 °C (for 6 h), or 60 °C (for 3 h) and 65% relative humidity. Fructosamine was produced during incubation, and available lysine content decreased simultaneously at all temperatures. In these conditions, the Maillard reaction occurring between a lysine residue and glucose was in the early stage. The glycosylated protein has high solubility in 0.5 M NaCl, and its emulsifying properties were superior to unglycosylated protein, although Ca-ATPase activity was completely lost. The regulation of the Maillard reaction in the early stage would be important for improvement of functional properties of fish myofibrillar protein. Keywords: Fish; myofibrillar protein; myosin; neoglycoprotein; glycosylation; Maillard reaction

Carp myofibrillar proteins were glycosylated with glucose through the Maillard reaction (the early stage), and their solubility in various ionic strength media was investigated. To react with glucose, lyophilized myofibrils mixed with glucose (at weight ratio of 1:9) were kept at 40 °C and 65% relative humidity for 0−48 h. By glycosylation, myosin and actin became solubilized in low ionic strength media. The total solubility of myofibrillar proteins in 0.01−0.16 M NaCl increased with the progress of glycosylation and was almost equal to the solubility of 0.5 M NaCl. When 17% lysine residue in myofibrillar proteins was reacted with glucose, 61% myosin and 82% actin were solubilized in 0.1 M NaCl. These results indicate that water-soluble myofibrillar proteins can be prepared by glycosylation with the Maillard reaction. Keywords: Fish; myofibrillar proteins; neoglycoprotein; glycosylation; Maillard reaction; solubility

Carp myofibrillar proteins (Mf) were conjugated with dextran through the Maillard reaction, and their functional properties were investigated. Lyophilized myofibrils mixed with dextran (weight ratio 1:9) were kept at 40 and 50 °C (65% relative humidity) for preparing neoglycoprotein (Mf−Dex). The utilization of the protective effect of dextran was required for preparing Mf−Dex with high solubility, and the myosin heavy chain was selectively conjugated with dextran. Mf−Dex developed an excellent emulsifying property, and the solubility of Mf−Dex was almost unchanged by heating at 50 °C for 6 h. The improved emulsion stability was not impaired by heat treatment at 50 °C. Keywords: Fish; myofibrillar proteins; neoglycoprotein; glycosylation; dextran; solubility; thermal stability; emulsifying property; Maillard reaction

When myofibrillar proteins of scallop striated adductor muscle were reacted with glucose through the Maillard reaction, the change in the solubility of myofibrillar proteins in 0.05-0.5 M NaCl solutions during glycosylation and their soluble states were investigated. The solubility in low-ionic-strength media increased greatly with the progress of the Maillard reaction. The solubility in 0.1 M NaCl reached 83% when more than 60% of lysine residues in myofibrillar proteins were modified by glucose. However, the excess progress of the Maillard reaction impaired the improved solubility of myofibrillar proteins in a low-ionic-strength medium. Myosin, actin, and paramyosin in glycosylated myofibrillar proteins were solubilized independently regardless of NaCl concentration. In addition, the glycosylated myosin lost its filament-forming ability and existed as a monomer in 0.1 M NaCl.

Alginate oligosaccharide (AO) was conjugated with carp myofibrillar protein (Mf) by using the controlled Maillard reaction, and the change in the solubility of Mf in low ionic strength media as affected by the glycosylation was investigated. AO was prepared by degrading sodium alginate using alginate lyase, which was purified from the culture supernatant of Pseudoalteromonas elyakovii. When a lyophilized Mf and AO mixture was incubated at 40 degrees C and 65% relative humidity, the conjugation of AO was confirmed at myosin heavy chain, actin, and tropomyosin. When >30 microg/mg of AO was conjugated to Mf, the protein solubility in a low ionic strength medium was greatly improved without significant loss of available lysine. These results indicate that the conjugation with AO is a superior manner for improving the water solubility of Mf in view of its nutritional aspect.