Newsletter: February 19, 2019

Researched and written weekly by the editorial team of Food Technology magazine, the IFTNEXT Newsletter explores what are, arguably, the next big things in the science of food through original reporting of scientific breakthroughs, leading-edge technology, novel food components, and transdisciplinary R&D.

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Bionic Mushroom
Photo courtesy of Sudeep Joshi/Stevens Institute of Technology
Supercharging mushrooms to generate electricity
Researchers at Stevens Institute of Technology have supercharged mushrooms, using clusters of cyanobacteria and graphene nanoribbons to produce electricity.

In engineering circles, cyanobacteria are known for their ability to generate small amounts electricity. Stevens researchers took things to the next level, creating a bioengineered system that allowed the cyanobacteria to produce electricity for a longer period of time. They began by determining that the microbiota that white button mushrooms host effectively nourished the cyanobacteria and allowed them to survive for several days longer than on controls (silicone and dead mushrooms.)

For their experiment, the researchers used a 3-D printer to print an “electronic ink” that contained nanoscale graphene ribbons, which served as an electricity-collecting network atop the mushrooms. They also printed a “bio ink” that contained cyanobacteria onto the mushroom caps in a pattern that intersected with the electronic ink. At the points of intersection, electrons were able to transfer through the membranes of the cyanobacteria to the network of graphene nanoribbons. When light was shown on the mushrooms, it activated cyanobacterial photosynthesis and generated an electrical current. The more densely clustered the cyanobacteria were, the more electricity they generated.

“In this case, our system—this bionic mushroom—produces electricity,” said Manu Mannoor, an assistant professor of mechanical engineering at Stevens. “By integrating cyanobacteria that can produce electricity with nanoscale materials capable of collecting the current, we were able to better access the unique properties of both, augment them, and create an entirely new functional bionic system.”

“We showed for the first time that a hybrid system can incorporate an artificial collaboration, or engineered symbiosis, between two different microbiological kingdoms,” says Sudeep Joshi, a postdoctoral fellow in Mannoor’s lab.

Mannoor sees the potential for a variety of “next-generation” applications. “For example,” he says, “some bacteria can glow, while others sense toxins or produce fuel. By seamlessly integrating these microbes with nanomaterials, we could potentially realize many other amazing designer bio-hybrids for the environment, defense, healthcare, and many other fields.”

The research findings were published in the December issue of Nano Letters.


Oat Bran
Natural antioxidants from bran
A major trend driving food product development is the rising demand from consumers for natural ingredients, including antioxidants. Until now, little work has been done to identify new natural antioxidants. But a recent study published in Food Chemistry details the discovery by researchers at Pennsylvania State University of an antioxidant in grain bran that could preserve food longer and replace synthetic alternatives.

The research team focused on a class of compounds called alkylresorcinols (ARs), which are found in the bran layer of cereal grains like rye, wheat, and barley and are thought to be defense compounds protecting the grain kernels from the growth of microorganisms. After noticing that the chemical structure of ARs is similar to that of commonly used antioxidants, the researchers hypothesized that ARs might exhibit antioxidant activity and would also have the advantage of being extracted from a common waste stream—namely, bran—thus creating a value-added product.

The researchers extracted ARs from rye bran and purified them using low temperatures (-80oC), which caused the ARs to crystallize so they could be isolated from the soluble impurities. The rye bran extract was added to oil and homogenized to form model food emulsions. Emulsions were investigated because people often consume oils as emulsions in mayonnaise and salad dressings. Emulsified oils are prone to degradation, which produces off aromas and flavors.

Primary and secondary products of lipid oxidation were monitored over storage to determine the rate and degree to which the emulsified oils degraded. The researchers compared the AR-containing emulsion to an emulsion without added antioxidants and to emulsions containing alpha-tocopherol or butylated hydroxytoluene.

“The major finding of this study,” says lead author Andrew Elder, “was that a rye bran extract rich in ARs was able to preserve a model food emulsion by slowing the rate of oxidation, preserving the quality of the emulsion longer than emulsions which did not contain antioxidants.” The rye bran extract tripled the time before the onset of oxidation compared with the control treatment.

The researchers also observed that the emulsion containing ARs oxidized faster than those containing alpha-tocopherol and butylated hydroxytoluene, which might indicate that ARs, at the concentrations tested, were less effective but could also indicate that the rye bran extract was not completely pure. Further research will reveal whether an individual AR type is more or less effective than conventional antioxidants.

The preliminary findings open the door to investigating the ability of ARs to preserve many different foods. “Current research indicates that ARs are likely responsible for the observed increase in shelf life of whole grain breads over refined flour breads, where AR content is negligible, due to their antioxidant activity,” says Elder. He also notes that ARs could be applicable to creams, dips, soups, sauces, and certain beverages, as well as bakery goods that contain incorporated oils and fats

Elder cautions that “further work needs to be done on ARs to understand their mode of antioxidant action, effective concentrations, etc.,” including experiments to determine ARs’ viability and effectiveness in specific food products.



Lemon juice, white wine help inhibit browning in dough
Commercial bakers often make doughs and store them for days or weeks until they are ready to use them. The longer the doughs are stored, the more susceptible they are to enzymatic browning, which can cause pie, cake, and pastry doughs to discolor during storage. Certain synthetic additives can help prevent this, but the use of synthetic ingredients is scrutinized by some consumers. Researchers developed a naturally derived solution that is effective at preventing the discoloration and functions as an alternative to synthetic ingredients.

The team of researchers, led by Peter Fischer of the Institute of Food Nutrition and Health in Zurich, Switzerland, tested a range of synthetic browning agents and three natural ones (white grape juice, lemon juice, and white wine) on samples of dough made with wheat flour. They measured the levels of discoloration and the activity of polyphenol oxidase, the enzyme that drives enzymatic browning, on the samples of dough at different points over the period of 4 weeks of storage. Of the naturally derived ingredients tested, a combination of white wine and lemon juice performed the best at inhibiting polyphenol oxidase activity and enzymatic browning.

The researchers published their study in the Journal of Agricultural and Food Chemistry.