Physico-chemical characterization of a novel functional food: Tomato juice with soy.

摘要

Several epidemiological studies suggest that the consumption of tomato and soy is associated with a reduced risk of a number of chronic diseases. Isoflavones and carotenoids, found in soy and tomato products respectively, have been identified as potential health promoting active components. The impact of combining these foods into new products, and characterizing their physico-chemical properties has not been investigated. Therefore the overall objective of this study was to characterize at a macroscopic and molecular level a system of tomato juice with added soy.; The rheological properties of tomato juice containing 1.5% soy germ was compared to plain tomato juice with and without 1% soy protein isolate. Rheological tests depicted characteristics of "physical gels" for all three products governed by non covalent interactions that are dynamically formed and broken. From the steady- and dynamic-flow experiments, the addition of soy germ to tomato juice did not affect qualitatively the rheological properties of tomato juice while addition of soy protein showed significant qualitative and quantitative differences. Dynamic tests as a function of temperature showed that the stability and the compatibility between tomato juice and soy germ were higher as compared to soy protein isolate. Therefore, the addition of soy germ is not expected to change the texture of plain tomato juice as compared to tomato juice with soy protein isolate while significantly enhancing its isoflavones content.; The combination of homonuclear and heteronuclear two-dimensional NMR techniques using cryogenic probe served to identify several lycopene isomers and other carotenoids dissolved in lipid mixtures of traditional, high beta-carotene and tangerine tomato juices. Diffusion NMR measurements using Pade-Laplace method (a non traditional processing technique) showed an enhanced ability to calculate diffusion coefficient for carotenoids present at different concentrations without "a priori" assumption concerning the number of exponential components in the signal decay. The results obtained suggested that high field NMR can be used as an excellent means to rapidly characterize complex carotenoid mixtures with minimal purification procedures.; In consideration of the model systems applied, diffusion NMR measurements showed that the addition of carotenoids to the soy isoflavones/protein mixture did not affect the diffusion coefficient of polyphenols. Therefore, on the basis of self-diffusion coefficient, carotenoids found in the tomato juice, did not seem to interfere with the interactions between soy protein and isoflavones.; The overall studies showed that the addition of soy germ improved the stability and texture of tomato juice providing a delivery system of carotenoids, soy protein and significant isoflavone content.