Comparative study of block cryoconcentration in pomegranate juice: Centrifugation versus vacuum

Abstract

AbstractBlock cryoconcentration is a technique that can be applied to obtain fruit juice concentrates while preserving their nutritional, bioactive and organoleptic properties. Until now, the investigations present both the centrifugation and vacuum cryoconcentration method independently for different matrices, but with different purposes such as observing the effect of the initial freezing temperature, the freezing direction, whether radial or unidirectional, the effect of several cycles of cryoconcentration, comparing cryoconcentration with other concentration methods, etc. However, there is no study that compares both methods in the same matrix considering some common parameters such as cryoconcentration time. The objective of this research work was to compare two block centrifugation methods, centrifugation‐assisted (CABC) and vacuum‐assisted (VABC). A factorial experimental design was used. The operation conditions evaluated were 110 RCF and 2360 RCF, and 10 and 70 kPa at the same time conditions (4 and 12 min). Pomegranate juice was frozen at −20°C unidirectionally for 48 h before treatments. For the response studied—concentration index (CI), solute yield (SY, %) and efficiency (Eff, %)—CABC at 110 RCF for 12 min showed the best overall results (SY = 59.2% and Eff = 84.3%) and the desirability was .91. For VABC at 10 kPa for 12 min, the desirability was .98 but SY was lower. In both methods, the CI in one cycle was up to 3.0. The advantage of both systems is that in one cycle the CI, SY and Eff were higher than those obtained by other investigations on pomegranate juice.Practical applicationsCryoconcentration is an emerging technology for concentrating a food solute in a solution based on the separation of ice crystals from a freeze‐concentrated solution. The nutritional and sensory quality of cryoconcentrated fruit juices is higher than those concentrated conventionally by means of evaporation due to the low processing temperatures. Consumer demand for food rich in bioactive components for a healthy lifestyle is growing. With the use of the block freeze concentration technique, it is possible to produce a pomegranate juice concentrate with excellent nutritional properties. Two techniques for assisted block cryoconcentration of pomegranate juice—vacuum and centrifugal—were compared in a single cycle. Both methods showed better performance in once cycle than other cryoconcentration methods at lab scale. The generated knowledge in this study can be easily adapted for the juice industry in order to improve the process parameters of block freeze concentration in the elaboration of concentrated pomegranate juice.