Concentrated grape juice by reverse osmosis following a consumer-driven approach
This study aimed to evaluate the consumer acceptance of grape juice concentrated by reverse osmosis at 60 bar and 50°C. The concentrated juice was diluted and sweetened using just-about-right scale determined by consumers. The principal component analysis showed similarities between the reconstituted grape juice previously concentrated by reverse osmosis and the integral grape juice, which confirmed the potential of reverse osmosis process. The pre-concentration of grape juice by reverse osmosis tested in this study had a positive result due to the maintenance of the sensory characteristics of the grape juice.
Grapes are harvested worldwide and they are processed into important food products, such as raisins, jam, preserves and juice. In addition, grapes are an important source of antioxidants due to their high content of phenolic substances. Grape juice has almost three times the total polyphenolic concentration of orange or grapefruit juice and grape juice contains flavonols, anthocyanidins, and proanthocyanidins (1).
Grape juice is widely commercialized as concentrated juice. The traditional methods of juice concentration, such as vacuum evaporation, usually employ high temperatures to remove water. However, heat can cause undesirable changes in the product's sensory and nutritional properties, such as colour alterations, off-?avour and reduction in the nutritional value. In this context, an alternative for thermal evaporation is the use of membrane concentration processes. Membrane processes are able to concentrate juices at room temperature, causing little or no damage to the product (2, 3).
Reverse osmosis is a membrane separation process in which a hydraulic pressure that is greater than the osmotic pressure of the solutio ...