Heat kills, and that’s fine with food processors who want to ensure the safety of raw and minimally processed foods.
Heat also degrades the quality of products, and that’s a concern when the product in question’s health benefits are compromised by thermal treatment. Vacuum, ultraviolet light and other techniques can limit negative impacts, but processors who want a food safety intervention that doesn’t degrade taste or nutritional value have had to rely on propylene oxide and other chemical pasteurizers, all of which leave behind some residues, however minute.
Strictly speaking, a new intervention from Agri-Neo Inc. (agri-neo.com) is a chemical, although it has been certified organic by Ecocert Group, L’Isle-Jourdain, France. The only residue is water, developers point out, and log reductions from 2 to 5 or more for bacteria, fungi, yeast, mold and coliform loads are delivered, depending on the dosage used.
Agri-Neo is a Toronto-based startup that began research on the technology in 2009. Beta testing was done last year with several Canadian food processors. Everspring Farms, a Seaforth, Ontario, firm that processes about 25 varieties of raw seeds, sprouted grains and other natural products, commissioned an industrial scale unit in May.
Everspring Farms is taking a measured approach, applying the compound to seeds like chia and flax that will be sold as ready-to-eat and offering it as an option to customers who will further process them, according to owner Dale Donaldson. “So far, I’m happy with the system,” he says, but the processor is evaluating the results on a case-by-case basis before expanding treatment to all products. Everspring previously deployed an infrared pasteurization process, but results were inconsistent.
According to Rob Wong, Agri-Neo’s president and COO, the system consists of a rotating drum in which a mist is sprayed on up to 12 tons of product per hour. About 2 percent moisture pick-up occurs during the process. A post-treatment dryer is an optional though highly recommended component.
“The water isn’t bound, it’s free on the surface,” Wong explains. “We want to remove it at the end so that the product is back to its natural moisture level because you want to minimize any possibility of re-growth.”
The biocide is classified as peracetic acid, although it is derived from several types of plants, with food-grade ethanol as the carrier. The solvent contributes a molecule of oxygen when it contacts a microbe, rupturing the cell wall and leaving behind water. “The combination of agents wasn’t something that was obvious, and they attack microbes in a number of different ways to consistently deliver at least a 5 log reduction,” he adds.
The residual water isn’t enough to cause “gumminess” in seeds like chia and flax, he says. The compound has been approved by Health Canada and the U.S. EPA. A similar peracetic-acid wash for fruits and vegetables is on the market, but Agri-Neo’s compound won’t bleach grains and doesn’t cause a breakdown of protein in hard wheat. That’s a consideration for grain millers, several of whom are considering their pasteurization options in the wake of several E. coli-related flour recalls
Agri-Neo is working with two millers considering treatment of grain before it is milled. Those firms’ processes involve tempering to reduce moisture levels. The pasteurizer could be added during a hold step, avoiding the need for any additional capital equipment.
Do the wave
Mass heat transfer aided by acoustic waves is an option for drying and cooling food that is slowly attracting interest and installations. The Dept. of Defense is one of the technology’s biggest proponents, with food scientists at the U.S. Army Natick Soldier RD&E Center in Natick, Mass., eyeing it as a way to improve the quality of shelf-stable Meals Ready to Eat (MRE).
Tom Yang, senior food technologist at Natick, spoke about the technology at IFT. He cited numerous production efficiencies and food quality improvements to acoustic drying and cooling, including faster line speeds, significant reductions in energy use and a much smaller footprint compared to conventional dryers. Yang is working with Zinovy "Gene" Plavnik of Heat Technologies Inc. (HTI), an Atlanta engineering firm that secured a U.S. patent last year for acoustics-aided heat transfer.
The physics of acoustic or ultrasonic drying involves the breakdown of the boundary layer that envelopes the area to be cooled or, conversely, cooked. As Plavnik explains, sound waves from ultrasonic transducers “start obstructing the boundary layer and allow heat and moisture to escape.” That accelerates the heat transfer process that occurs.