Dole Value Added Products

By Charles E. Morris, Midwest Editor of Food Engineering

    Because highly-perishable raw materials are a major cost, manufacturing economics in the fresh-vegetable industry dictate that plants be located near the source of the supply.   Major processors actually relocate their plants seasonally between these two areas.

    The largest of these firms, Dole Fresh Vegetables, Inc. (a unit of Dole Food, Inc.), formerly operated one plant at Marina, CA, April through early November, and a "mirror" plant at Yuma, November through March.  Dole shifted major equipment back and forth to minimize capital idled during the off season. 

    In the autumn of 1992, Dole Fresh Vegetables was expanding its manufacturing strategy for a new product category:  refrigerated, retail-packaged pre-cut fresh vegetables and salads.   The company had extended its food-service line of pre-cut vegetables into the retail market in April '91, and the new "Refrigerated Salad" category was an instant success with customers.

   By November '92, Dole had completed the first phase of a two-phase off-season expansion plan at Yuma and was planning to expand its older, site-constructed plant at Marina.  Dole retained the Dennis Group, Inc. (DGI), a design, engineering and construction-management firm based in Sprongfield, MA, to critique its manufacturing strategy and design plans.

    Then Dole was hit with a double whammy:

•     On November 11, Dole voluntarily recalled cole slaw produced at the Marina plant.  Product contamination had been detected in a one-pound bag of Coleslaw Mix by the Canadian Health Ministry.  Although no illness resulted, Dole shut Marina down, started disassembling and sanitizing the plant, and modifying several processes.
•     On November 13-one week prior to startup, the Yuma plant was totally destroyed by fire.  Nothing could be salvaged.  Fortunately there were no injuries.

   Dole was left with no manufacturing facilities to supply a growing market, or to produce new products scheduled for rollout in January and April '93.

    Next challenge:  Develop an expansion plan which would allow Dole to maintain its aggressive expansion/new-product rollout schedule within the original capital budget.

    The Dole/DGI engineering team developed a plan for executing three concurrent projects:

    1.)  Double the capacity of the Marina plant while in full operation.

    2.)  Rebuild and double the size of the Yuma plant in time for seasonal production starting November '93.  (The value of the destroyed plant was covered by insurance.)

    3.)  Build a new plant to replace site-constrained Marina in time for seasonal production starting April '94.  Startup date was mandated by perishable crops.  This meant building a much larger "greenfield" plant within a budget (excluding site purchase) originally projected for expanding Marina.

    DGI was awarded design, engineering, and construction-management responsibilities, and DGI engineers were integrated with Dole's eight-person engineering staff.  Marina was expanded within its site limitations by 30,000 sq.-ft. and started-up at Yuma in time for seasonal production in time for November '93.

    Meanwhile, after evaluating 53 sites throughout a 65-mile radius over a two-month period, the Dole/DGI team, in June '93, selected a 361-acre site at Soledad, CA, as the location of its new plant to replace Marina.  Ground was broken in late July-allowing only eight months before mandatory startup.

•   USDA-equivalent sanitary standards, applied for first time to the largely unregulated fresh-vegetable industry.  All process equipment is made of stainless steel with continuous welds and open construction.
•     Hazard Analysis at Critical Control points (HACCP).  A hazard-analysis approach was a key priority in plant design and construction to eliminate safety concerns.
•     Process innovations, including new and redesigned equipment plus technology transfer from other food-processing industries.
•     Improved mobility, allowing more efficient seasonal relocation of more equipment.  Most equipment is of modular construction and pedestaled for easy removal by overhead monorails or forklift.  About 76 flatbed trailers are now required to move the plant to Yuma, for example, as opposed to the 20-25 to relocate from Marina, yet the April '95 move-from shutdown at Yuma to startup at Soledad-was accomplished in only 81 hours.  Transport time was 18 hours.  "We're like an organized caravan that follows the lettuce," says Manufacturing Director Eric Schwartz.

    About 900 mostly seasonal employees working three shifts (two production, one cleanup) process some 25 different vegetables into 0 "active" SKUs ranging from Broccoli and Cauliflower Florets to Caesar, California Blend and European Blend Salads.  Vegetables are typically harvested, transported, processed, packaged and shipped within 36 hours.   No raw minerals are inventoried; once in-plant, vegetables can move "from bin to bag in 12 to 15 minutes," Schwartz adds.  About 50 percent of all production is made to order; no finished goods are warehoused on-site.  Most orders are shipped the same day the customer's order is placed.

    "We can make every SKU every day, which can mean up to 70 changeovers per day," Schwartz points out.  "We average about 58 turnovers per day."  About 85 percent of plant production is packaged for retail, 15 percent for food service markets.   Refrigerated shelf life of finished products:  14 to 19 days, depending on variety.

    The plant typically ships about 60,000 cases of finished products per day but has shipped as many as 80,000, Schwartz adds.  Finished products are shipped about 40 miles to the former Marina plant, now a distribution center.

    Receiving:   Vegetables are received in palletized harvest bins weighing 600 to 900 pounds each, 20 bins per flatbed trailer.  After weigh-in and physical inspection, vegetables are cooled to 35-40°F in a conveyorized vacuum cooler or hydroshower to remove field heat.  Hugh forklifts designed to handle 20 bins at a time (10 pallets stacked two high) move entire flatbed loads from trucks to cooler, the after cooling into the raw-material warehouse, where smaller forklifts continuously supply trim-line hoppers with two bins at a time.  This rapid-handling system minimizes outside staging time for cooled product.  Redesigned bin dumpers roll rather than drop product into hoppers, reducing product damage and extending shelf life.

    Trimming and Cutting:  Vegetables are conveyed down trim lines for visual inspection, manual trim, and removal of defects and field debris.  Trim lines are of 30-ft. modular stainless steel construction for improved sanitation and minimum breakdown during plant relocation.  Power supply is electric rather than hydraulic to further ease reinstallation.  Trim-line waste is removed at rates up to 120,000 pounds per hour via Reyco pneumatic conveyors (rather than typical belt conveyors) and blown directly to the waste press for composting.  The pneumatic system better handles wet, leafy waste, minimizes capital costs and is easily cleaned with a chlorine/water purge.

    Trimmed lettuce varieties are conveyed to Carruthers cutting machines, originally developed for cutting frozen meat blocks and oversized for vegetable applications, to minimize product damage while making square, consistent, accurate cuts   On one line, a "megacutter" boosts throughput tenfold to 18,000 pounds per hour, eliminating a former bottleneck.

    On other lines, vegetables such as broccoli and cauliflower are trimmed into florets; carrots are peeled in a Magnuson peeler and shredded in an Urschel cutter; spinach is rotated in a DGI-designed tumbler to remove sand and soil before washing.   One line incorporates a "vegetable combination project" which automates blending, washing, and continuous (rather than batch) drying of complex vegetable combinations.

    Washing (the most critical point): HAACP integration includes a triple-wash system designed by the Dole/DGI team to tightly control temperature, chlorination and product dwell while conserving as much energy as possible.

    Cutting traumatizes vegetables; their respiration rates increase, speeding degration.  Cut and blended vegetables are therefore conveyed immediately into chilled chlorinated water for a controlled dwell.  This reduces respiration rates and reduces bacteria while thoroughly cooling the product.

    According to DGI, engineering the wash process was formerly considered an exercise in energy conservation.  It centered on calculating the amount of energy required to lower the temperature of a given quantity of water, then filtering and recirculating the water while continuously controlling chlorine with each screening.

    But vegetable particulars in recirculated wash water create high BOD, which binds free chlorine and negates its benefit.  DGI therefore designed a triple-wash system consisting of:

    1.)  An initial chilled, chlorinated wash to remove gross debris.  This system is completely isolated and allows four screened reuses of water before complete, automatic replenishment.

    2.)  A secondary, isolated chilled-water system in which chlorine can be controlled, as a sanitizing step.

    3.)  A spray of single-pass chlorinated chilled water serves as a final "kill" step.

    Cut vegetables are pumped into tubular, 8-inch diameter washing flumes by Cornell hydropumps, originally designed for pumping live fish without damage in the seafood industry.  Screening and chilling systems allow all process water to be recycled.

    The plant uses 650,000 gallons of water per day, derived from an aquifer and cooled through an APV plate heat exchanger before use.  Wastewater is applied with a linear sprinkler system to crops such as kale and alfalfa grown on-site.

    Drying:   Leafy products move across dewatering conveyors; more delicate products such as broccoli and cauliflower are dried by air knife.  Vegetables then move via vibratory conveyors into stainless steel baskets, which are maneuvered by chain hoists into centrifugal dryers redesigned by Dole engineers to minimize the time vegetables spend unpackaged.  The new PLC-controlled dryers reduce total spin time by 50 percent.   Baskets are then staged on a stainless steel roller deck and moved to elevators supplying the packaging systems.  This was formerly a labor-intensive, accident-prone area where employees pushed loaded baskets across wet surfaces, adding risk of cross-contamination and causing idling downstream.

    DGI collaborated with Stokes Material Handling Co. to design a more highly automated handling system combining free roller conveyors with proximity switches and PLC-controlled chain conveyors to keep packaging lines continuously supplied.   The new system minimizes injuries and contamination.

    Packaging:   Baskets of dried vegetables elevate to vibratory metering conveyors feeding 19 packaging lines, each consisting of Hayssen/Yamato computerized combination scales atop Hayssen vertical form/fill/seal (VFFS) bagging machines.  (Designed with expansion in mind, the plant can accommodate 17 more packaging lines.)  Packaging lines were formerly sized to the 5-pound food-service package, which required a feed rate of only 60 pounds per minute to the scales, many upstream and downstream line components were oversized.

    For smaller packages, the Dole/DGI team designed a "double stack" system with six Key Iso-Flow vibratory metering conveyors stacked in tandem to supply a combination of twin-tube and single-tube VFFSs for a combined operating speed of about 300 packages per minute.  This system reduces required upstream/downstream equipment, better utilizes plant space, and allowed design of a smaller plant than originally envisioned-important to keeping the project within budget.

    For mixed-vegetable salads such as Caesar, Italian Blend, California Blend and Herb Ranch, pouches of seasonings, croutons and dressings (supplied by other packers) are manually added at the scales.  Products are bagged in films of varying oxygen-transmission rates (OTRs) designed by Dole to match vegetable respiration rates and mass.

    Finished packages travel via belt conveyors through metal detectors and are manually cartoned on lines supplied by mezzanine case formers.  Cartoned products are manually palletized and moved to a staging area for immediate shipping.

    Process Control is based on Texas Instruments PLCs integrated with a single PC in a control room via Opto 22 Cyrano man-machine interface (MMI) and Wonderware software.   Cyrano, a flow-chart programming language, interface Wonderware with the PLC control language, explains project manager Bill Vith.  PLCs control process variables such as refrigeration temperatures, pump speeds and scale-feed rates, and equipment such as the basket-handling decks and elevators.  The system monitors equipment such as dryers, packaging machines, and motor controls in real time; alarms process variations when out of spec; monitors and histograms use of resources such as water and chlorine; and incorporates a statistical process control (SPC) capability used to tighten process specifications and improve equipment utilization.

    Quality assurance incorporates HACCP, with three shift supervisors and 22 technicians monitoring critical control points such as water temperatures, chlorine levels, plant temperatures and metal detectors.  The plant's QA lab inspects incoming raw materials, and samples finished products for specifications such as cut, size, package weight, shelf life, and mix ratio.  QA technicians and production teams apply SPC to tightening package fill-weight variances.  Microbiological testing is conducted by an independent lab, and plant technicians use 3M Petrifilms for quick quantitative indications of bacterial growth on equipment surfaces.