Retention of Ascorbic Acid and Solid Concentration via Centrifugal Freeze Concentration of Orange Juice

Abstract

Freeze concentration of liquid foods produces high-quality concentrates while retaining the heat-labile compounds found in fresh samples. Centrifugal freeze concentration is a cryoconcentration method assisted by an external force, centrifugation, to enhance the separation of concentrate from the ice. When applying centrifugal freeze concentration to orange juice, after the third cryoconcentration cycle, the ascorbic acid content in the concentrate showed retention close to 70% of the initial value. After the third cycle, the solutes in the concentrate increased 4 times the initial value of the fresh sample with 70% efficiency. The color evaluation showed that the final concentrated fraction was darker than the fresh juice. The centrifugal freeze concentration in orange juice was effective for obtaining a high-quality concentrate with a higher concentration of solids and ascorbic acid retention.

Improvement of Centrifugal Cryoconcentration by Ice Recovery Applied to Orange Juice

“…In addition, a good fit was observed between the experimental ( W e ) and predicted ( W p ) ice mass ratios over the cycles and recirculated samples, leading to low values of the RMS, namely, between 2.4 % and 7.1 %. These RMS values were close to those reported in the literature using different cryoconcentration technologies , , , , , , .…”

“…By raising the number of cycles, the solutes in the concentrate increased progressively and reached approximately 31, 50, and 57 °Bx after the first, second, and third cycle, respectively. These results were superior to those obtained previously in our laboratory with orange juice under the same centrifugal conditions , where the concentration increased from 10 to 40 °Bx. Similarly, the results were higher than those reported by Sanchez et al , in which orange juice was concentrated until 29 °Bx with a semi‐industrial pilot‐plant falling‐film unit for progressive cryoconcentration (static freeze‐thaw without external forces) of liquids.…”

“…Under this condition, the ice in the third cycle has a sufficient amount of solutes for its practical use as a concentrated product. The resulting amount of solutes occluded in the ice was higher than those obtained previously in our laboratory , , where the solids amount incremented by 2.5, 2.7, and 1.2 times after the third cryoconcentration cycle of orange, blueberry, and pineapple juices, respectively. This difference can be explained by the fact that in the present study different centrifugation times among the cycles were applied, namely, approximately 10 min in the previously mentioned study versus 14, 12, and 8 min, which could induce differences in the suction process of solutes (concentrated solution) from the ice fraction by centrifugation .…”

“…The final separation is performed through passive thawing, but the overall separation efficiency is relatively low [13]. Therefore, external forces such as shaking [14], ultrasound [15], vacuum [16], or centrifugation [17] have been added to the block cryoconcentration to improve the separation and other process parameters. In the centrifugation case, the process takes advantage of the frozen matrix formed by veins between the ice crystals occluding the concentrated solution.…”

“…Hence, block centrifugal cryoconcentration as an effective concentration technique was applied to different frozen liquid samples such as orange juice [17], protein solution [18,19], sugar solution [20,21], brackish water [22], coffee extract [23], yerba mate [24], blueberry juice [25], and pineapple juice [26]. In addition, centrifugal cryoconcentration was recently proposed as a technique to obtain a concentrated osmodehydration agent from pomegranate juice [27].…”