Block freeze concentration technique applied to grape juice

Concentration extends the shelf life and reduces logistics costs of food products. Cryoconcentration maintains the content of thermosensitive compounds similar to those of fresh food. Thus, the objective was to evaluate the efficiency of blocks cryoconcentration of grape juice. The experiment was conducted in triplicate. Samples of 4.70 ± 0.06 L each were subjected to blocks cryoconcentration. After freezing and thawing, 2.35 ± 0.03 L were obtained from each of cryoconcentrated (C1) and cryodiluted (D1) samples. Total soluble solids (TSS), total phenolic compounds (TPC) and total reducing sugars (TRS) contents of each sample were used to calculate the concentration efficiency. During freezing, water molecules organize themselves to form ice crystals, the solutes are segregated and accumulate in the solid-liquid interface (C1), located between the ice crystals (D1). C1 has its vapor pressure reduced, lowering its freezing point and remaining liquid. With an efficiency of 91.13% ± 0.09%, the TSS content increased from 18.31 ± 0.03 °Brix in the initial juice to 31.16 ± 0.36 °Brix in C1, with a D1 of 2.76 ± 0.01 °Brix. The TRS content, expressed in mg of GAE L-1, increased from 3,771.67 ± 6.65 in the initial juice to 6,566.67 ± 26.96 in C1 and 565.28 ± 7.27 in D1, with an efficiency of 91.38% ± 0.35%. With efficiency of 98.74% ± 0.04%, there was an increase in the TRS content from 116.20 ± 12.57 g L-1 in the initial juice to 193.50 ± 25.24 g L-1 in C1, with D1 of 2.40 ± 0.25 g L-1. The results expressed statistically significant difference between sample means in both analysis of variance and Tukey's test (p < 0.05) in all parameters. The results obtained prove the importance and efficiency of the technique and present an alternative able to improve the quality of oenological processes and products.