The process for producing pectin peel involves diffusing the sugars from the peel and then drying the peel at low temperature. The dried peel is exported to plants that use an acid-alcohol precipitation process to extract the pectin.

This processing of citrus peel for sale to pectin extractor firms is an area of technical expertise of Vincent Corporation. For many years we have designed and manufactured the machinery that is required.

Pectin peel is a by-product made from peel by citrus producers. It is generally made from lime or lemon peel, although it can also be made from grapefruit and orange peel.

The processed peel is sold to firms such as CP Kelco in Denmark and Danisco Cultor in Mexico. Citrico is a new firm entering the field. These firms, in turn, extract pectin from the peel and sell it as a food additive. Contacts at these firms are found at the end of this report.

Pectin peel generally sells in the range of US$ 300 to $600 per short ton. This can be compared to selling pelletized citrus peel for animal feed, where the market is in the range of US$ 50 to $100 per ton.

The process of producing pectin peel revolves around washing the peel in water so as to leach out the soluble sugar.

This contrasts to the process for making peel into animal feed in which the first step is to react the peel with lime. Lime degrades the pectin, releases the bound juices, and thus permits efficient pressing and dehydrating. In contrast to this, the production of pectin peel must preserve the pectin; therefore it can not be limed.

As a consequence of this process the peel is a lot more slippery and a lot more difficult to press (dehydrate). Accordingly we de-rate the capacity of our traditional screw presses by 50% or more.

Further, pectin peel must be dried very carefully at low temperatures and with carefully controlled humidity. The Vincent design rotating drum drier is the norm for the industry. This dryer permits recirculating some of the partially dried peel and mixing it with the material coming from the dewatering press. It is a triple pass dryer with a stationary outer shell, which contrasts to the single pass rotating drum dryer most commonly used in the production of animal feed.

Most places that have tried to use the single pass dryer have failed to the point where the process was discontinued. However there are some plants, notably at Decidersa in Murcia, Spain where operation is successful.

Processing plants where Vincent, over 40 years, has installed pectin operations include Ci Pro Sicilia and Cesap in Italy; Laconia, Paco Hellas, Nikopolis (ex-Esperis) and Greek Juice Processing in Greece; Citrex and San Miguel in Argentina; Quimica Hercules, Productos Esenciales, Industrial Citricola, and Industriales Limonera in Mexico; Jn-Jacques and Moscoso in Haiti; Priman Canning and Yahkin in Israel; Avante in Brazil and Unipectin in Morocco.

Currently there are only two processors producing pectin peel in the United States: Ventura Coastal in California and Parman Kendall in Florida. Both of these plants were engineered and built by Vincent Corporation.

Typically we look at peel coming from extraction in the range of four tons per hour on the low side and sixteen on the high side. More recently flows of 26 MTPH have been of interest.

The following equipment is key to the process:

Vincent VS-180 Shredder. This machine slices the peel in order to permit proper pressing without creating excessive fines. It is of the thin, rigid blade design, as contrasted to the hammer mill concept.

Pulp Wash Conveyors or Tanks. These are used for diffusing the sugar from the peel. We recommend either three or four counterflow wash stages, either vertical or horizontal in configuration.

Pulp Wash Sumps. Stainless steel sump tanks, possibly with progressive cavity peel transfer pumps.

Dewatering Between Stages. We recommend the use of either Vincent Series KP "soft squeeze" presses or static screens for dewatering between wash stages.

Vincent Series TSP Screw Press. Traditionally the Series VP presses have been used to remove moisture from the peel prior to further dehydration in the dryer; the new Series TSP offers superior performance. It separates the peel into (a) press liquor and (b) press cake. The pectin peel is made from the cake. It is a horizontal, all stainless machine featuring an interrupted flight design. The unit is equipped with a rotating air cushioned cone, complete with pneumatic controls.

Furnace. Each Vincent dryer comes with its burner and refractory lined furnace for burning natural gas, fuel oil, or a combination of these fuels. A very low gas temperature, in the neighborhood of 1200º F, must enter the dryer. A low wet bulb temperature is important in the production of high quality pectin peel, whereas a feedmill dryer must produce high wet bulb temperature in order to drive the Waste Heat Evaporator.

Dryer Feeder. This is a stainless steel screw conveyor and feeder with a companion flange matched to the dryer throat. It has a variable speed drive.

Dryer Drum. This is a Vincent triple pass dehydration unit with a stationary outer drum. The unit is equipped with recycle extractor conveyors so that partially dried material is extracted at the end of the second pass and mixed with the incoming press cake. Also important is a 180º elbow between the Furnace and the inlet to the drum. The selection of this dryer is made using the appropriate de-rating associated with (low temperature) pectin peel production.

Exhaust System. This separation system features the Vincent low level entry cyclone separator that has proven ideal in producing pectin peel. The expansion chamber is complete with an air lock screw conveyor product discharge.

Exhaust Fan. A radial blade fan complete with inlet elbow and exhaust stack.

Standard Instruments. A solid state programmable controller modulates combustion through a sensor mounted at the inlet to the third pass of the dryer. This is required for precise control of product quality.

Vincent Cooling Reel. This is complete with a fan, dust collector, ductwork, supports, and electric motors. This type of cooler is not used in modern feedmills because of the need for a pellet cooler (which is not used in pectin peel production).

Product Elevating Screw and Surge Hopper. A carbon steel conveyor and hopper, leading to the bagging equipment.

Sewing Head and Bagging Scale. A compact Fischbein sewing head and conveyor with a bagging scale are typically included. Hercules plants use a proprietary baler.

Despite the length of this letter, there are a great many details that I have left out. We would be glad to work with you on specific requirements.

Robert B. Johnston, P.E.

P.S. The contacts at CP Kelco and Danisco are:

For CP Kelco the switchboard number is 011-45-56-165616; the office fax number as 011-45-56-169446. The peel buyers are Martin Kragh and Hans Porse. CP KELCO, DK-4623 LILLE SKENSVED, DENMARK