Apple and Pear Juices

Apple and pear products offer a unique challenge as they contain a class of color bodies called polyphenolics. These are responsible for the rapid browning color that is often seen when an apple is cut and left standing. In juice production, these color bodies are formed after extraction, either enzymatically or by rapid oxidation during exposure to air. Once extracted, an apple or pear juice stream contains about 12% sugars (glucose, sucrose and fructose). See Figure 1.

As the first step, the stream is passed through an adsorbent to remove the existing color bodies and the organic color body precursors. From the adsorbent, the stream is passed through a weak base anion resin in order to remove free acidity and a smaller portion of color components which may have slipped through the adsorbent bed. The strong acid cation resin in the H⁺ form is applied to exchange out the K⁺, Ca²⁺ and Mg²⁺ ions and to strip out a good portion of the nitrogenous containing materials. The second weak base anion resin column removes mineral acidity and provides a final color removal. The resulting stream can then be sent to an evaporator for concentration to a canning syrup or a juice for blending.

Figure 1. Apple and Pear Juices