[Effect of High Hydrostatic Pressure Combined with Temperature on the Antigenicity and Conformation of Tropomyosin Purified from Shrimp].

Foodborne shrimp allergy events have occurred in recent years. To illustrate the mechanism of high hydrostatic pressure technology to change the allergenicity of shrimp, the major allergen tropomyosin was separated and purified from Litopenaeus vannamei, and indentified with matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS). The effect of temperature factor under high hydrostatic pressure was measured with indirect ELISA method, CD and fluorescence spectrum. The results showed that the antigenicity of TM protein had an increase after being heated at 35 or 45 ℃ when treated at 300 MPa for 15 minutes, while the antigenicity decreased at 55, 65, and 75 ℃. With the increase of heat temperature, the secondary structure of TM also changed. The mutual transformation happened between the alpha-helix and beta-sheet, beta-turn, and the random coil. The tertiary structure of TM was observed dynamic changes from the extended state to the folded state, and then re-extended state to re-folded state. These results suggested that high hydrostatic pressure combined with temperature could influence the antigenicity of TM by the change of conformation which would be useful as theoretical guidance on developing new methods or technologies for producing hypoallergenic shrimp products.

Bagging treatment influences production of C6 aldehydes and biosynthesis-related gene expression in peach fruit skin.

Bagging is a useful method to improve fruit quality by altering its exposure to light, whereas its effect on fruit volatiles production is inconsistent, and the genes responsible for the observed changes remain unknown. In the present study, single-layer yellow paper bags were used to study the effects of bagging treatment on the formation of C6 aldehydes in peach fruit (Prunus persica L. Batsch, cv. Yulu) over two succeeding seasons. Higher concentrations of n-hexanal and (E)-2-hexenal, which are characteristic aroma volatiles of peach fruit, were induced by bagging treatment. After bagging treatment, peach fruit had significantly higher LOX and HPL enzyme activities, accompanying increased contents of C6 aldehydes. The gene expression data obtained through real-time PCR showed that no consistent significant differences in transcript levels of LOX genes were observed over the two seasons, but significantly up-regulated expression was found for PpHPL1 after bagging treatment In addition, bagging-treated fruit produced more (E)-2-hexenal and had higher expression levels of PpHPL1 during postharvest ripening at room temperature. The regulatory role of the LOX-HPL pathway on the biosynthesis of n-hexanal and (E)-2-hexenal in response to bagging treatment during peach fruit development is discussed in the text.

Analysis of the interaction between tropomyosin allergens and antibodies using a biosensor based on imaging ellipsometry.

A biosensor based on high spatial resolution imaging ellipsometry has been studied to examine its role in the rapid detection and analysis of the tropomyosin allergen existing in crustaceans. This methodology has been established for detection of the tropomyosin allergen and includes ligand screening, the determination of sensitivity, and a comparison with traditional detection methods. Three kinds of monoclonal antibodies (2F9, 4C7, and 2H6) known to have a high bioactivity against the tropomyosin allergen were screened and separately immobilized as ligands on a silicon wafer surface, thus allowing them to capture the tropomyosin allergen. Resulting changes on the wafer surface were visualized in gray scale variation on an ellipsometry image. Images showed that these antibodies are able to recognize the presence of the tropomyosin allergen in shrimp and crab with sensitivity of 1 mg L(-1), and at a detecting time of approximately 30 min for an extracted sample. This preliminary study has shown that the detection of the tropomyosin allergen is rapid and specific when using this type of assay on products containing shrimp and crab. When compared with the enzyme-linked immunosorbent assay, the biosensor based on imaging ellipsometry is able to perform a fast label-free analysis.