Keeping on top of new technologies can be daunting, especially ones that have yet to be commercialized. We’re looking at four technologies that have the potential to improve some very basic functions in food processing: freezing, disinfection, drying and authentication.
Isochoric freezing
There are two problems with conventional freezing: it’s expensive, and it often alters the product. Isochoric freezing is a potential path around both.
Simply put, the technique involves putting food, either bare or sealed in flexible material, inside a rigid container, filling the container with water and freezing it. The pressure inside the container keeps all but about 10% of the water from freezing. The actual food doesn’t freeze, and so forgoes the cellular damage that comes from crystallization.
Isochoric freezing for food was developed by a team funded by the USDA and headed by Boris Rubinsky, a mechanical engineer at the University of California-Berkeley, and Cristina Bilbao-Sainz, a USDA research food technologist. They patterned it after Rubinsky’s development of the technique for transporting organs for transplantation.
One of the biggest advantages of this kind of freezing is that it can be done with conventional freezing systems, Rubinsky says.
“In addition to improving the quality of the preserved food, preserving the food in an isochoric system as opposed to freezing results in huge savings of energy, because only a small part of the volume is frozen - and freezing is a huge energy consumer,” Rubinsky says. “All this without actually changing the refrigeration system and only by placing the food in a closed isochoric system rather than in open air.”
Food of any kind that is now frozen is a candidate for isochoric freezing, Rubinsky says, along with others. “This also opens the door to preservation of foods that cannot withstand freezing, because freezing involves formation of ice crystals in the food, while in isochoric preservation either the ice crystals do not form at all or form outside of the food.”
He says that the only major change would be using rigid containers instead of running food products directly through a freezer. The team is developing isochoric storage with fisheries in Iceland and has drawn interest from other industries.
“The biggest challenge [to commercialization] is the fact that isochoric preservation requires a change in thinking about low-temperature storage of food,” Rubinsky concludes.
High-voltage atmospheric cold plasma
An overriding goal in preserving food safely is killing as many microorganisms on or around it through a process that alters it as little as possible. One method to do this has been through atmospheric plasma, which has been used for industrial disinfection as far back as 1857 on drinking water in Germany.
High voltage atmospheric cold plasma (HVACP) uses the mostly ionized air that is produced by passing between two parallel electric diodes. The chemical properties of both the electric field and the gases that result (such as ozone, nitric oxides, peroxides and atomic oxygen) have biocidal properties and can also break down toxic microbial products like mycotoxins, rendering them harmless, says Cherian George, discovery & regulatory lead at NanoGuard Technologies, the leading developer of the process.
There’s a wide range of products that could potentially be treated with HVACP, including meat, potatoes, nutraceuticals, seeds, flour mills, ready-to-eat milled products, peanuts, hazelnuts, row crops, pet food, edible flax and animal feed mills, says NanoGuard CEO Larry Clarke. NanoGuard is currently concentrating on grain products like animal feed, wheat flour or corn grits. “Also the nut market and the seed market, but we’re still in the middle of research with pilots to introduce more,” Clarke adds.
HVACP has not been widely commercialized; “It’s the tip of the spear,” Clarke says. Considerations to commercialization include making it work on a scale that matters, getting FDA approval and “connecting a market with a problem and effectively, in a commercially viable way, [solving] that problem,” Clarke says.
Electrohydrodynamic drying uses an airflow between electrodes, called “ionic wind,” to dry foods faster and with less electricity.
Electrohydrodynamic drying
Like HVACP, electrohydrodynamic drying (EHD) uses ionized air. It creates an airflow, called “ionic wind,” by running electricity through a pair of electrodes on either side of the food to be dried. The ionic wind dries food faster than conventional convective drying, due in part to the heat generated by the process.
“EHD drying is a non-thermal and highly energy-efficient method that makes it suitable for drying heat-sensitive materials with low energy consumption,” says Kamran Iranshahi, a doctoral student at ETH Zurich, a Swiss public research university.
In addition to being more energy-efficient, studies have shown that products dried with EHD retain their color, flavor and nutritional content better than those done with conventional drying, with lower shrinkage and higher rehydration capacity. So far, the technique has mostly been used on fruits and vegetables, but there is potential for other products and even other industries like pharmaceuticals, Iranshahi says.
EHD is more suitable for small to medium-sized batches because it can’t achieve the airflow rate of fan-driven conventional systems, Iranshahi says: “In this type of drying, compatibility (to the production line and to the current values and norms e.g., production rate) of EHD is the biggest barrier towards diffusion of this clean technology.”
One promising potential application would be farmers using EHD for field drying. The energy consumption is low enough that a field EHD system could be powered by photovoltaic panels – something that many governments in the developing world are willing to underwrite.
Oxygen isotope modeling
Fraud in the food business often centers on geographic origin. If a country or region is famous for a certain kind of food or beverage, some products gain fraudulent value when they’re falsely advertised as being from there.
Ascertaining geographical identity in a food product involves studying its oxygen isotope ratio. This basically measures the proportion of 16O, the most prevalent isotope of oxygen, to 18O, a much less common one. The significance is that the amount of 18O in plant material is a function of the rainfall and other climate factors where the plant grew. This yields an isotope “signature” unique to that area.
However, developing this signature for a given area is a major obstacle to oxygen isotope analysis. Conventionally, it involves analyzing plants from that region and building a database – a time-consuming and expensive process.
Researchers at Switzerland’s University of Basel have developed a faster way to develop these regional signatures. Their model can take publicly available climate information and extrapolate the isotope signature for plants grown in that region.
“The model input data we need for our calculations at a given location are air temperature, relative humidity, precipitation amount and the oxygen stable isotope composition of precipitation,” says Florian Cueni, the researcher who developed the process.
“All this data is publicly available through different data sources, even as spatial maps, and thus allows the spatial application of our model,” he continues. “This then allows us to seek out all possible growing locations of a sample with unknown geographic origin.”
The model as currently developed is limited to plant organic material like cellulose or bulk dried material. It can’t be used for processed products like olive oil (a frequent target of regional fraud), but “is well possible that with certain modifications to the model, it might also be able to work on olive oil, as these oils also show very distinct geographical patterns in their isotope signature,” Cueni says.
