Progress in Processing

In traversing the processing exhibits at the 2007 Food Expo in Chicago in July, I noticed that they seemed somewhat smaller than some have been in the past.

For instance, a few years ago, one supplier of high-pressure processing equipment brought a full-scale unit to the show. This year, only one of the three companies active in that area was present—Avure, Kent, Wash.—and it had a relatively small booth. Perhaps high pressure has become so well-accepted that it verges on routine. Avure said that treatment of meats, in particular, has caught on and resulted in sales of multiple units. High-pressure-treated, ready-to-eat meat still must be refrigerated, but the risk of Listeria is largely eliminated, since the product can be treated after packaging.

A Selection of Exhibits
Aside from this size observation, I also noticed some processing exhibits that bear mention in this roundup article.

• Small-Scale Equipment. Competitors Armfield, Jackson, N.J., and MicroThermics, Raleigh, N.C., each displayed new units and features in their lines of small-scale equipment for low-volume production, research, and demonstration. Armfield showed a new ultra-high-temperature (UHT) batch processing vessel, a 25-L chamber capable of 150ºC and 5 bar pressure with heating, cooling, and a variety of available agitators. Applications include cooking confections, soups, and puddings.

Other new units from Armfield include a carbonator/filler, capable of 60 L/hr in 5- to 30-L batches of soft drinks, beer, and other beverages; and two rapid extractors, one for the benchtop and the other laboratory scale. The small unit has a 1-L chamber, while the larger has 5-, 10-, or 20-L. Solvents such as ethanol, water, or glycerol can be used at room temperature to recover flavors and other active substances from herbs, fruits, and seeds.

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MicroThermics showed a new touch-screen programmable logic controller (PLC) control system that is available on most of its UHT/high-temperature short-time (UHT/HTST) processors. These are self-contained units that provide a variety of heat exchangers and hold tubes to simulate many different thermal processes for fluids. Flow rates vary from 0.5 to 6 L/min. The units can be used for small-scale production, product development, and demonstration.

The touch-screen controller contains the operating manual and walks the operator, step by step, through equipment setup and operation. Essentially, the controller can replace a paper manual, easily lost or damaged, and also offers data-acquisition capability. Actual connections of correct flow path must be made by hand, but the controller verifies that they are correct for the selected process.

• Sterilization. Ethylene oxide has been commonly used to serilize dry herbs, spices, and seeds, but its use is decreasing due to changes in regulations. This creates a need for a sterilization technique that leaves no residue. Steam is one option, but care must be taken not to wet the dry powder. Two firms showed alternate approaches—SteamLab, Hamburg, Germany, and Revtech, Charmes sur Rhone, France. (My April 2007 column discussed SteamLab and a third firm, Safesteril, in the April 2007.) SteamLab treats solids in packages or bins in large, special chambers—first with steam and then with vacuum to cool and dry. Treated material is sieved, ground (if necessary), and repacked in a clean room.

Revtech, similar to its French competitor, Safesteril, uses electrical resistance to heat a transport device—a helical coil in the case of Revtech and a screw in the case of Safesteril. Revtech’s coil vibrates at an adjustable frequency and amplitude to move a powder from entrance at the bottom to the exit at the top. Residence time and capacity are determined by the coil length and the tuning of the vibrations. The temperature is adjusted by the current supplied. Units range from 100 to 2,500 kg/hr. After sterilization, the material is dried, if necessary, in a second coil through which dry air is passed. The electrical heating of the metal surface is primarily to prevent condensation of the steam and to provide some additional heating.

• Drying. The company formerly known as California Pellet Mill, now CPM, has become an equipment conglomerate with the recent acquisition of Wolverine, Proctor & Schwartz, Ltd., the UK-based operation of dryer manufacturer Wolverine Proctor, previously acquired by CPM. CPM Wolverine Proctor LLC, Horsham, Pa., like competitor Aeroglide, Raleigh, N.C., makes a line of conveyor ovens and roasters. Wolverine also offers impingement ovens and jet-zone fluid bed dryers.

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Aeroglide combines former dryer manufacturers FEC and Sargent with its own brand. The company announced an advanced control system for its dryers that monitors evaporation load, humidity levels, and energy efficiency. Drying temperatures and dampers are adjusted to maintain a constant humidity, accomodate changes in feed rate, and maximize energy efficiency. (My December 2006 and July 2007 columns also discussed drying.)

• Extrusion. CPM also owns Century Extrusion, Traverse City, Mich., one of several suppliers of twin-screw extruders. Century also offers replacement parts for its own and others’ extruders. Other manufacturers showing extruders included Wenger, Sabetha, Kan.; Clextral, Tampa, Fla.; Coperion (former Werner Pfleiderer), Ramsey, N.J.; C.W. Brabender (mostly small units), South Hackensack, N.J.; and Buhler, Plymouth, Minn.

Coperion showed a new, small-diameter twin-screw extruder that was meant mostly for product development. It is generally understood that scale-up of extrusion is challenging and best done from somewhat larger machines, but these also require more raw material, create more waste, and cost more, so a lab-sized unit is useful.

Wenger’s new development is the Magnum ST, a higher-speed twin-screw extruder, capable of delivering high levels of specific mechanical energy (SME) to products. SME is known to be a useful scale-up parameter and to correlate with cooking and expansion of starch-based extrudates. Wenger also offers accessories, including a mid-barrel valve and end-of-barrel back-pressure valve, which can increase SME by increasing resistance to flow, thus requiring greater mechanical energy. Twin-screw extruders, compared to single-screw extruders, are capable of handling lower moisture feeds, can be more flexible in feed rates, and can produce unique properties in the extrudates. They are also more expensive for the same capacity because they are more complex to make.

Clextral has traditionally used electrical heating of its extruders, while most other manufacturers use jackets for steam or hot oil. Some also use direct steam injection.

• Filtration. Two companies—Pall Corp., Port Washington, N.Y., and Microdyn Technologies, Raleigh, N.C. (U.S. subsidiary of Microdyn-Nadir GmbH, Wuppertal, Germany)—showed various membrane and ceramic filter media. Filtration is used in food processing to clarify sweeteners, concentrate dairy proteins, reduce waste water volume, and concentrate egg, among many other uses. Membrane filtration is categorized as micro-, ultra-, and nano-filtration, depending on the molecular weight cutoff (MWCO) of the medium. Microdyn’s membranes are various polymers with different porosities, resistance to solvents, and permeation rates.

Membranes can be configured as flat sheets, hollow fibers, and spiral-wound modules, in which flat sheets are separated by spacers and wound around a central collection tube. The objective is to maximize turbulence on the feed side, where there is a risk of a gel layer of concentrate building up. This maximum turbulence is achieved by maintaining as high a velocity as possible across the face of the membrane.

Pall offers complete filtration systems and modules as well as media, including metal cartridges for steam, ceramic microfilters, and polymeric membranes. In one application, a California dairy was able to reduce wastewater discharge penalties based on volume by concentrating the waste with a Pall ceramic membrane filter and discharging a lower volume of stronger waste to the municipal system. The ceramic filter is durable and easy to clean in place.

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• Mixing. Several companies exhibited a variety of mixers. Littleford Day, Inc., Florence, Ky., announced a line of laboratory mixers in various sizes, some with vacuum or pressure capability. Littleford’s mixers are characterized by their rotating plows and high-speed choppers, which enable incorporation of high levels of fat in dry mixes. Some units are also used as dryers.

Amixon Inc., Memphis, Tenn., has a line of well-constructed vertical-shaft mixers that use a spiral mixing tool to turn over the contents in as few as four revolutions. The shaft is top mounted with no bottom bearing, avoiding the wear and cleaning issues of a submerged bearing.

Komax Systems, Inc., Wilmington, Calif., offers a proprietary sanitary static mixer in tube sizes of 1–12 in. Static mixers have no moving parts, but rather have a succession of elements that divide and displace a flowing fluid or fluids. The more elements, the greater the dispersion, but also the greater the pressure drop. Static mixers are used for blending two fluids, as in reconstituting fruit juices from concentrates or adding liquid flavors to ice cream mix. The mixer can be jacketed for heating or cooling and can also be used with direct steam injection for heating a product stream.

Pulsair Systems, Inc., Bellevue, Wash., demonstrated its tote-stick mixer in an International Paper, Memphis, Tenn., corrugated tote with a plastic bag inside. The mixer uses pulses of compressed air to mix the contents with no moving parts. Similar mixers can be provided for up to 10,000-gal tanks and 20,000-gal rail cars.

• Heating. The EzHeater from hydroThermal, Waukesha, Wis., is a relatively simple device that directly injects steam into cold water to make hot water. While some direct steam injectors can also be used for other heating purposes, this device is apparently intended for water. A variable diffuser is modulated according to the desired temperature to control the amout of steam added.

• Powder Processing. Two companies—GEA Niro Inc., Columbia, Md., and Glatt Ingenieurtechnik GmbH, Weimar, Germany—offer different approaches to small-scale powder processing. Niro is well known for spray dryers and showed what it described as a new generation of laboratory spray dryers. The company’s Mobile Minor has three different atomizing systems: rotary, co-current two fluid, and fountain two-fluid. The rotary atomizer is a wheel spun by an air turbine onto which fluid is fed. The co-current atomizer uses compressed air to break up a viscous feed into droplets. The fountain nozzle sprays feed countercurrent to the air flow to create somewhat larger particles.

Glatt uses a fluidized bed for spray granulation, agglomeration, coating, powder layering, encapsulation, or drying/cooling. Inserts of various shapes are used for the different purposes, sharing a common internal filter and air supply, which may be heated or cooled. Glatt units are flexible and can be used to develop and evaluate a wide range of processes.

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• Separation. Waltham, Mass.–based Artisan Industries Inc., showed its versatile Rototherm, a type of scraped-surface heat exchanger which can be used in desolventizing, aroma recovery, caramelizing, concentrating, dehydrating, distilling, and stripping. Artisan also fabricates an evaporator/stripper column with specially designed internals, and a steam-jet chiller, which uses a steam ejector to create a vacuum which, by evaporating water, lowers the temperature of the remaining fluid.

• Pallets. One of the more novel and interesting developments I noticed was corrugated pallets, offered by Weyerhaeuser, Indianapolis, Ind. The pallets can replace those made of wood or plastic, can support more than 2,000 lb, and are much lighter than wooden pallets. This can save on shipping costs. In addition, corrugated pallets may present less risk of damage to goods stacked on them, since they do not have nails or splinters. It is normally good practice to keep wooden pallets out of food processing areas because of the risk of contamination, but corrugated pallets would not pose the same hazard. Weyerhaeuser says the pallets are waterproofed with PET film and are less expensive than plastic pallets.

Incremental Progress
It is rare to find a dramatic development in processing equipment; most progress is incremental. There continues to be considerable consolidation among equipment manufacturers, illustrated by the dryer industry, where five one-time competitors are now two firms.

New controllers, taking advantage of the constant improvement in computing power available, can be found on many traditional types of equipment. The suppliers of small-scale units continue to develop new offerings, and as universities and corporations shrink their pilot plants, these will be more in demand.

by J. Peter Clark, Contributing Editor, Food Technology ([email protected]).