Technology drives frozen vegetable process

From harvesting crops at their peak to accurately storing them post process, technology drives frozen vegetables at many levels.

Sno Pac Foods owner Pete Gengler says time is of the essence when processing vegetables. Most frozen vegetables can be fully processed and packaged within two hours of harvest.

“As soon as you pick something off the vine, it starts to breakdown,” Gengler said. “Enzymes work at it, and it begins to break down immediately.” 

Gengler says Sno Pac’s farms are located within 20-30 miles of the processing facility.  

“It’s only a half hour back to the plant, then the trucks are unloaded and through the freezer within roughly an hour to an hour and a half,” he said.  

Harvesting at peak freshness and processing so quickly allows for the food to be preserved with the greatest levels of nutrients still intact. 

How vegetables are frozen slows the enzymes down, Gengler said.  

“Virtually all vegetables are blanched before they're frozen, so that blanching process stops the enzymes,” Gengler said. “We do what we call a peroxidase test to ensure that the enzymes are stopped and that the breaking down of the vegetables stops so we can get a shelf life out of the product.” 

Peroxidase special types of enzymes found in nearly all vegetables. They are abundant in all forms of life including microorganisms and animals.  

The process for frozen vegetables begins in the field at harvest. Vegetables are then transported to the processing facility where they run through cleaning equipment. This process removes any matter from harvest that should not be included in the final package for consumers. Vegetables are then sent through an air cleaner, then continues to a flotation washer where additional matter is separated from the vegetables. Vegetables go through a final rinse and dewatering process. Then, vegetables are sorted using an optical sorting machine. 

“We can sort based on size and color,” Gengler said. “There’s a camera in the machine that can look at all the product as it goes by on a belt. We can select what colors are good or bad and the sizes and shapes that are good or bad.” 

This works by utilizing pixels to determine size and shape.  

“The computer will recognize if something has too few or too many pixels, and it will recognize that it can’t be the product,” Gengler said. 

The sorter moves at 500-600 feet per minute. 

Then, the vegetables are moved on to blanching. 

“It’s called blanching and not cooking because we are not trying to cook them,” Gengler said. “We are just inactivating the enzymes. We set the dwell time and the temperature to achieve negative peroxidation where we're inactivating the enzymes.” 

Once blanched, the vegetables are quickly cooled down in water that ranges between 42 and 44 degrees. Then, the vegetables are frozen, packaged and ready for transportation.  

Frozen vegetables are transported using temperature-controlled trucks from 0 degrees to –10 degrees, depending on product requirements. 

Seasonality and storage 

Vegetable production is seasonal. This means frozen vegetables are processed once per growing season. Not all processing facilities have storage space at their facilities, and grocery stores are unable to accept that will be sold per year.  

This means a space dedicated to housing frozen vegetables would be required. Enter: cold and frozen food storage facilities.  

Cold storage facilities offer temperature-controlled storage space where frozen vegetables can be held until needed.  

Les Dobbe, Director of Business Development with Lineage Logistics, said these facilities help ensure the production cycle continues. 

“We take production from various manufacturing facilities that are making French fries, appetizers, and more because that production line cannot stop,” Dobbe said. “As it goes out the backdoor, it has to go somewhere.” 

Cold storage facilities offer a “shock absorber” in the supply chain, Dobbe said. 

Dobbe’s facility in Steven Point, Wis. can hold 95,000 pallets of frozen food throughout the facility. 

“Alot of the products we deal with are then sent to local retailers such as Aldi, Walmart or Kroger,” Dobbe said. 

Food safety is critical in all aspects of the supply chain. At cold storage facilities, staff members work to ensure that the food does not suffer any temperature abuse at any point.  

“We have designated loiter times where food cannot sit on the dock,” Dobbe said.  

At Lineage, the process is highly technological. 

“We have a meter running in our warehouse management system that can notify the lead worker or supervisor and redirect labor to areas approaching a threshold,” Dobbe said. 

The warehouse management system can act as a GPS system for each pallet and staff in the storage facility.  

“The WMS system will alert the closest runner to pick up the pallet and relocate where it is needed,” Dobbe said.  

When grocery stores or restaurants are ready to accept the frozen vegetables, pallets are loaded onto a refrigerated truck, sealed and ready for final delivery.  

In case you missed it, join us on a tour of Lineage Logistics in this video: