The hypothesis that the consumption of soy foods, tomatoes, and cruciferous vegetables is associated with reduced risk for cancer has been supported by epidemiologic research. Our objective was to develop convenient, sensory acceptable, soy-tomato beverages rich in lycopene, soy isoflavones, and glucosinolates, which would be suitable for cancer prevention clinical trial research. Tomato juice, soy isoflavone concentrate, and broccoli sprouts were selected as ingredient sources for lycopene, soy isoflavones, and glucosinolates, respectively. Beverages were formulated to deliver a standardized serving of each of the phytonutrients. Because the bioavailability of fat soluble lycopene is dependent on the presence of lipid, in vitro digestion experiments were completed, and determined that a level of 1% oil addition would facilitate lycopene absorption while limiting adverse sensory effects. In addition, a preparation method for broccoli sprout inclusion was designed to maintain intact glucosinolates because they are easily enzymatically hydrolyzed by chopping and grinding.
Two functional beverages were developed, a soy-tomato product and a soy-tomato-sprout product. Sensory evaluation determined consumer acceptance of the beverages on overall acceptance, appearance, flavor, color, and mouthfeel. The control (Hirzel tomato juice) was found to be more acceptable (P < 0.05) than the experimental products for all attributes evaluated. Experimental products were acceptable in regard to their appearance and color. The soy-tomato product had higher acceptability (P < 0.05) scores than the soy-tomato-sprout product for flavor and overall acceptability. Flavor scores were most closely correlated to product acceptability.
The effects of processing on the physical and chemical properties of tomato juice and on phytonutrient content and composition were also evaluated. Viscosity, pH, lightness, and amount of yellow and red colors of the tomato juice increased (P < 0.05). Total soluble solids was not affected. Quantitative determination of lycopene, isoflavones, and glucosinolates was achieved using reverse phase HPLC and mass spectrometry (glucosinolates only). All phytochemical levels were decreased as a result of processing. However, processing led to increases in cis lycopene isomers, which may be the more bioavailable form of lycopene. Isoflavone distribution between families and between conjugation forms were not affected by processing. Processing had the greatest effect on the level and profile of glucosinolates. To minimize glucosinolate loss, broccoli sprouts should be added at a later step of processing.
Overall, this study has shown that the combination of soy isoflavones, lycopene, and glucosinolates into functional beverage can be achieved. These products have the potential for use in clinical cancer prevention trial research.