Pulp wash

In the extraction of citms juices it is desirable to have as gende an extraction pressure as possible. There should be minimal contact time between juice and pulp to reduce the amount of bitter substances expressed from the peel into the juice. The amount of suspended soHds in citms juice is controlled in a subsequent separation in a finisher. A screw action is used to force the juice through a perforated screen and separate the larger pulp particles from the juice. The oil level in the juice is adjusted by vaporizing under a vacuum (10). The separated pulp is washed and finished several times to produce a solution which is then either added back to the juice to increase juice yield, or concentrated to produce pulp wash soHds, also called water extract of orange soHds, which can be used as a cloudy beverage base. 

Pollution Control in the Bleachery. The quantity of water necessary for bleaching, and consequently the volume of effluents, has been decreased significantly by various schemes for recycle of Hquors, eg, pulp washing using dilute spent Hquors and countercurrent flow. Effort is underway to close bleach plants and further reduce water consumption. 

DiManro, A. et al.. Recovery of anthocyanins from pulp wash of pigmented oranges by concentration on resins, J. Agric. Food Chem., 50, 5968, 2002. 

LEVELS OF CAROTENOIDS (MG/LITRE) IN AUTHENTIC (HAND-SQUEEZED ORANGE JUICE, FROZEN CONCENTRATED ORANGE JUICE (FCOJ) AND IN FROZEN CONCENTRATED ORANGE PULP WASH (FCOPW), BOTH DILUTED TO 12° BRIX. (N = 5 FOR PERA RIO, N = 4 FOR NATAL, N = 3 FOR VALENCIA AND HAMLIN VARIETIES, AND N = 2 FOR FCOPW)... 

The pulp recovered during screening may be transferred to a pulp-wash operation to yield further soluble solids by counter-current extraction with water. The washed pulp may be held for further processing or included with the bulk of ejected peel material from the extractors. This is milled, treated with lime (calcium hydroxide or calcium oxide) to break down pectin and reduce water retention, pressed, dried to c.10-12% moisture content and finally converted to pellets. Being high in carbohydrates these are used as filler in livestock feed blends. 

FIGURE 4.26 (A) A typical orange juice and pulp wash samples hi NMR spectra... 

Le Gall, G., Puaud, M., and Colquhoun, I. J. (2001). Discrimination between orange juice and pulp wash by 1H nuclear magnetic resonance spectroscopy Identification of marker compounds. ]. Agric. Food Chem. 49, 580-588. 

Viscosity poses a similar problem in the production of pulp wash concentrate. Pulp wash consists of juice solids obtained by countercurrent washing of pulp after its separation from juice. On a °Brix basis, pulp wash liquids are higher in pectin than juice from which the pulp has been screened (19). Concentration of pulp wash above 40°Brix is at times hampered by excessive pectin levels (20). To control viscosity processors may be forced to reduce finisher pressure to minimize pectin extraction, thereby curtailing yield. A more effective solution is to treat pulp wash with pectinases to reduce pectin levels (21). If pectinases are incorporated into the wash water, this method has the advantage of increasing total solids yield by reducing juice retention in the pulp. 

Dried Pulp, Peel Oils, Pulp-Wash Solids, Dried Juice Sacs... 

Juice and concentrate quality is controlled by regulations, resulting in manufacture to uniform standards worldwide however, less control is exercised over certain by-products and specialty products. Some of the factors important to quality of the specialty products, dried pulp, peel oils, pulp-wash solids, and dried juice sacs will be included in the following discussion. 

Composition. Scientific data concerning liquids washed with water from orange juice finisher pulp was first published by Olsen et al. (30). They studied Brix/acid ratios, sucrose, reducing sugars, pH, pectic constituents, turbidity, pulp content, ascorbic acid, viscosity, and flavonoid content of experimental and commercial samples. Characterization of pulp-wash continued with publication of quality data (31), examination of pectic substances (32), microbiology (33), and comparison of pulp-wash with orange concentrate (34). 

The composition of pulp-wash is such that, if both pulp-wash and juice are from the same batch of fruit, it may be included as a component of the product called concentrated orange... 

In a study of yield and recovery of various citrus byproducts, it was reported that juice finisher pulp recovery was about 4.4 kg/100 kg of oranges and 2.7 kg/100 kg of grapefruit. Commercial recovery of soluble solids (ss) as pulp-wash should yield approximately 0.6 kg ss (oranges) and 0.2 kg ss (grapefruit) from 100 kg fruit (38). 

Some quality parameters, typical of commercial pulp-wash concentrates and dilute liquids, are included in the following statements ... 

For 60°B pulp-wash concentrate, a viscosity up to 10,000 cps (Brookfield with 4 spindle, 60 rpm, 26.7°C) and a 2 gel would be typical. Viscosities above 15,000 cps would be considered high, but the range 2,000 to 5,000 cps would be good if the liquids had been enzyme treated. 

Recoverable oil (% by volume) of 10°B liquid reconstituted from concentrate is usually low (0.005 to 0.015%). Pulp-wash normally contains no floating pulp and should be reasonably free of hesperidin crystals and other defects. Pectinesterase activity should not exceed 5.0 P.E.U. (1 P.E.U. represents 1 meq. ester hydrolyzed per min per ml per °B) (43). 

The juice vesicles, or "sacs," remaining after juice extraction and pulp-washing may be included in the portion of peel residue dried as cattle feed. However, it is feasible to recover and utilize this material as either frozen (3) or drum-dried juice sacs (44). 

Royo Iranzo and Aranda (1 ) and Royo Iranzo et aK (2) found from one half to one third of the commercial European bottled orange juices tested were adulterated. Mears and Shenton [3) reported the most common form of adulteration in the early 1970 s was the use of fruit by-products such as extracts of peel and pulp (pulp-wash). It appears that the problem has continued into the 1980 s. Three orange juice surveys in the United States (162 samples obtained from retail outlets) conducted by the Florida Department of Citrus during 1979 and 1980 indicated gross adulteration by orange pulpwash (PW) and/or sugars and/or dilution (Petrus et al., unpublished data). 

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