Production of Pomegranate Juice Concentrate by Complete Block Cryoconcentration Process

In this study, complete block cryoconcentration of pomegranate juice was investigated. Two freezing temperatures (-201C and -40 +/- 1C), two thawing modes (gravitational-assisted thawing and microwave-assisted thawing) and four cryoconcentration stages were the process variables. Total dry matter content, process efficiency, pH and color values (L, a, b and E) of cryoconcentrated and ice fractions were investigated. In addition, pomegranate juice concentrate was produced by conventional thermal processes, namely evaporation by rotary vacuum evaporator and by heating at atmospheric pressure to compare the color values and pH of final cryoconcentrated pomegranate juice with those of thermally produced juice concentrates. Freezing temperature and thawing mode did not have any significant effect on the total dry matter content of cryoconcentrated and ice fractions as well as process efficiency, pH and the color values (P>0.05). However, the results indicate that cryoconcentration stage had a significant effect on dry matter content, process efficiency and the color properties of both fractions (P>0.05). The final dry matter content of pomegranate concentrate reached 34.20 +/- 0.13% from the initial value of 17.16 +/- 0.68%. The change in the pH of final cryoconcentrated pomegranate juice was less than the change in the pH of thermally produced juice concentrates. This study showed that the color characteristics of pomegranate juice were well preserved by complete block cryoconcentration process in comparison to conventional thermal processes. Practical ApplicationsConcentration of fruit juices is one of the oldest methods by which the shelf life of fresh products can be extended significantly. Concentration of fruit juices by means of thermal process is proved to induce adverse effects on sensory and chemical properties of them. Cryoconcentration technology is introduced as a suitable technique for concentration of liquid foods and nutraceuticals because it can preserve the nutritional and sensory qualities of the products while it is a green technology. Because pomegranate juice is a valuable source of bioactive compounds that are responsible for its appropriate color, cryoconcentration process has high potential for preserving its nutritional and sensory properties during concentration process.