Refrigeration: Chilling tales of technology

Thank freeze-drying, IQF and MAP for quantum leaps in the quality of foods.

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At left: A spiral freezer design from
Frigoscandia Equipment, which dramatically
improved the image of frozen food quality
when it introduced the FloFreeze IQF freezer
decades ago. Today, Frigoscandia is a unit
of FMC FoodTech.


By Mike Pehanich, Plant Operations Editor

In modern supermarkets and mass merchandising outlets, products seem to sprout from the shelves like mushrooms overnight. Nowhere is this more evident than in the frozen and refrigerated supermarket cases where attractive new products are the order of the day.

The consumer takes this horn of plenty for granted, rarely considering the technological wizardry that makes many of the most useful and exciting products possible. Old and new, big and small, following is a handful of freezing and refrigeration-related technologies that have opened the floodgates of possibility to food makers.

The fruits of freeze-drying

While freezing is a key part of the process, it turns out not to be the method of preservation in the backward world of freeze-dried foods and their three-stage metamorphosis from fresh to frozen to shelf-stable.

Freeze-dried products can be amazingly fresh-like when rehydrated. Freeze-dried shrimp plump up like a freshly cooked sea critter and look just as good as their freshly caught cousins on the rim of a cocktail bowl. Freeze-dried fruit and vegetables of comparable quality have been around even longer.

Nearly any type of fruit can be freeze dried into forms ranging from large chunks down to fine powders. Photo courtesy of Oregon Freeze Dry
A look in the supermarket might give the impression freeze-dried fruit is a new arrival in the cereal aisle. But a leader in the technology has been making freeze-dried product for two generations.

“The first freeze-dried product was a strawberry created for cereals,” says Herb Ashkenazy, president of Oregon Freeze Dry, Albany, Ore. (www.ofd.com). “That was 41 years ago.”

Timing is everything, says Ashkenazy, and the time for freeze-dry seems to have arrived. To Ashkenazy, the wait strengthens the first principle of the food entrepreneur’s credo: The most important thing a company can do is survive the tough times and be ready when its time finally comes.

Today, new cereal products containing freeze-dried fruit seem to be arriving daily. What’s more, they are reinvigorating cereal sales. Peaches, strawberries, bananas and berries of all sorts are buried in those cereal boxes. General Mills has even employed a branded ingredient strategy with its recent fruitful offerings, listing the Oregon Freeze Dry name on products containing the freeze-dry leader’s fruit.

What’s the reason for the surge? Not necessarily improved product quality. Complaints about quality have been nearly non-existent during Ashkenazy’s 21-year tenure with Oregon Freeze Dry. What has been a factor, however, is the cost.

“We have made real strides in the output [of dried product] per unit of equipment,” says Ashkenazy. “I can’t tell you how proud I am of our people. They had been doing the same thing, and producing a great product, for decades. But then to say ‘Here’s a better way…’ ”

Freeze-drying involves sublimation, a process you learned in high school science and likely thought little about since. Product is first frozen at low temperature and then placed under vacuum. This is where the sublimation takes place. The process evaporates the ice. The ice crystals pass into the gaseous phase without first becoming liquid. Applying heat at the proper stage accelerates sublimation. Low temperature condenser plates remove the vaporized ice crystals from the vacuum chamber by converting them back to a solid.

The improved economics came by diminishing the time and energy needed to remove ice crystals from the product. Equipment is expensive, as is the cost of running it. “You have to put energy into the product in those giant vacuum chambers,” says Ashkenazy. “Accelerating drying cycles and getting more product out of a chamber without damaging the product is a big deal.”

Still, Ashkenazy insists the improved economics of processing are only a part of the success story. The economics were never as bad as they were perceived, he claims. True, it takes 12 pounds of strawberries to yield a single pound of freeze-dried strawberries. “But you get it all back when you rehydrate the product,” he says. Customers understand that message more easily today.

Of course, market success simplifies education.

“Kellogg took Special K and added elements that could have been added a half century ago and hit a home run,” says Ashkenazy. “Now, we have been able to show cereal makers what freeze-dried fruit can do for their products. Freeze-drying has the unique ability to preserve product in a dry state without loss of quality. You can dry the product for exceptional shelf life and still get the flavor, appearance and aroma of the original product with rapid rehydration. Most important is that they have enabled the creation of cereal products that are new and different and better.”

The products have helped reverse the slow decline in dry cereal usage, he says. Now they have the cereal category on an upward path.

“I have felt for the longest time that freeze drying is the most underutilized preservation method known to man,” says Ashkenazy.

Quickly frozen

Individually quick freezing (IQF) is another technology that has dissolved into the invisibility of the consumer’s everyday expectations.

Before the advent of IQF, frozen fruits, vegetables and seafood often came frozen in lumps. Freshness, taste, and product integrity suffered for the cause of preservation. Frigoscandia Equipment, today a Northfield, Minn., unit of FMC FoodTech, introduced the technology with the FloFreeze IQF freezer, and it has changed the image of frozen food quality ever since.

IQF has made it easy to assemble attractive frozen meals and "looks as if it were made from scratch" meal components.
This revolutionary process eliminated blocks and frozen clusters of product. It enabled processors to clean, trim and freeze-in the nutrients of fruits and vegetables sometimes within hours of harvest. The process arrested the natural degradation process, making the frozen product at times superior to fresh.

But by preserving the product and integrity of the raw food item, it also enabled accurate and high-quality portion control. Thanks to IQF, not only are frozen meals easily and attractively assembled, but so are the popular “cook it yourself as if you had made it from scratch” component meals as well.

“Product can be frozen in bulk, individually divided up and mixed into component packages,” explains Jeff Barach, vice president of special projects and technology tracker for the National Food Processors Assn. Barach touts IQF quality and the way it has enabled easy, high-quality meal assembly and compartmentalization. “New applications of IQF include prepared meals for folks with special dietary needs such as low-fat, low-carb, or any type of special meal,” he says.

A slightly different tack is taken at Graceland Fruit (www.gracelandfruit.com), Frankfort, Mich. “Graceland started innovating during a year when the cherry crop was so large that we decided to experiment by drying the excess cherries,” says Donald Nugent, president and CEO. Experimentation led Graceland to become a supplier of fruit and vegetable ingredients to food processors, and to provide them using several processes.

Graceland’s Soft-N-Frozen process combines fruit with sugars and a natural stabilizing system, which binds and controls the free water in fruit pieces, inhibiting ice crystal formation. The result is a fruit ingredient that will not completely freeze, remaining soft and scoopable, while retaining fruit piece identity and natural color.

Unlike IQF fruits, these fruits can be added directly to consumer products with minimal thawing, the company says. The Soft-N-Frozen process preserves the integrity and character of delicate fruits, plus the pasteurization process ensures very low microbe counts.

A healthy atmosphere

Just a few degrees warmer than the freezer, refrigerated cases for more than a decade have carried the invisible technology of modified atmosphere packaging. MAP controls the internal environment of fresh products such as raw meats and vegetables to extend freshness and shelf life.

MAP helps maintain the visual as well as microbiological assurance of freshness. Yet the consumer sees nothing of the technology other than the plastic overwrap, which appears no different than films consumers have encountered for decades.

NOTE TO PLANT OPS:

Knowledge of the ingredients and their properties is critical in maintaining the quality, freshness and shelf life in your packaged refrigerated product. Discuss with Plant Operations and especially Packaging how the ingredients vary with regard to respiration, maintaining fresh appearance and texture, and microbial response with different gas mixes and films.

Fresh beef requires oxygen to maintain the red color equated with freshness. Yet oxygen accelerates degradation in vegetables, which yield oxygen as a waste product.

It really gets tricky when you mix widely varying ingredients, as in a fresh salad. The various components may have different gas preferences, and finding the right balance to provide the best atmosphere for the mix requires knowledge not only of the ingredients themselves, but of the packaging materials influencing the atmosphere.
Maintaining the optimum mixture of gases – evacuating some and sealing in others -- is the key to the technology.


“The challenge of MAP has always been finding the right mix of gas,” says NFPA’s Barach, “plus selecting the packaging material with appropriate breatheability for moisture control with respiring vegetables.”

Determination of both is not an easy task, and the technology has a long history of study, punctuated by trial and error. The atmosphere in a bag of respiring mixed vegetables, for example, is constantly changing. Vegetables emit gases as they age, and each vegetable varies in its pattern of respiration and moisture retention.

“You also have a safety factor,” explains Barach. “With mushrooms, you need a certain amount of breathability. That’s why you often find holes in the film. You don’t want dangerous anaerobic bacteria like clostridium botulinum to develop.”

In other products, the mere presence of oxygen is sometimes the biggest threat to shelf life. Oxygen scavenging technologies today are recruited to meet the challenge.

The latest generation of Cryovac (www.cryovac.com) oxygen-scavenging films absorb oxygen at a 10- to 20-percent faster rate than their predecessors. The polymer-based film has a scavenging component that is coextruded as an invisible package layer, which preserves the clarity of the film. The result is improved freshness, color and nutrient preservation, not to mention a better microbiological safeguard. It is particularly valuable with light-sensitive products.

Nestle’s Buitoni brand of Italian food products incorporates Cryovac OS (oxygen scavenging) film into the lid packaging on its fresh refrigerated pasta products. The companies claim a 50-percent increase in shelf life.

Of course, products like fresh meat need to keep oxygen in to prolong the appearance of freshness. Case-ready meats make major use of modified atmosphere packaging, primarily with multi-layer barrier containers. Often these consist of polypropylene (PP) with an added ethylene-vinyl alcohol (EVOH) layer, the latter keeping oxygen or nitrogen in while keeping ambient air out.

Eastman Chemical (www.voridian.com), Kingsport, Tenn., has introduced its VersaTray Dual-Ovenable crystallized PET and Voridian APET, an amorphous (non-crystalline) polyethylene terephthalate, touting the combination as a more cost-effective alternative to more expensive PP-EVOH containers in MAP applications. The manufacturer claims its products have better gas barrier properties and can be easily sealed.

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