Juice press, rotary

Juice extractors differ in design, but all are fast, rugged, easy to clean, and adjustable to accomodate fruit of different sizes. Prior to the invention of automatic extractors, the rotary juice press was in common use, and is still used commercially in many parts of the world, principally Italy, Spain, South America. 

The Bucher-Guyer horizontal rotary press is a highly automated batch process machine that requires no press aid. The press consists of a horizontal hydrauhc ram inside a rotating cylinder containing many flexible rods covered with a knitted synthetic fabric. The rods have serrated surfaces to allow juice which passes through the fabric to flow to the discharge ends. Hydrauhc pressure is apphed for a preset time, the ram is retracted, and the cylinder is rotated to break up the press cake. This cycle is repeated several times before the press cake is removed from the cylinder and the press is cleaned (16). Juice yield for this horizontal rotary press is 84% with secondary water addition it is increased to 92% (15). 

Use of ultrafiltration (UF) membranes is becoming increasingly popular for clarification of apple juice. AH particulate matter and cloud is removed, but enzymes pass through the membrane as part of the clarified juice. Thus pasteurization before UF treatment to inactivate enzymes prevents haze formation from enzymatic activity. Retention of flavor volatiles is lower than that using a rack-and-frame press, but higher than that using rotary vacuum precoat-filtration (21). 

Alfalfa Lysis. Whole alfalfa (Medicago sativa) plant tissue was broken and cell rupture was by shear in a rotary device. Juice expression was by a batch type press, as described elsewhere (17), The resulting alfalfa extract was stored, until required, at -20°C. 

Carbonation. In this process, the juice is heated to 80 to 90°C, limed, and then sent to a carbonator for gassing with carbon dioxide. The resulting mixture, containing insoluble lime salts, chiefly calcium carbonate, is pumped to subsiders (thickeners, clarifiers) to remove the insolubles by settling. From the subsider, the partially clarified filtrate is recarbonated, and the residual lime is precipitated. This treatment is followed by press filtration. The sludge from the subsiders is filtered on rotary-drum filters, and the sugar-laden filtrate is returned to the first carbonation step. The carbonation process can be either continuous or batch. 

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