Newsletter: March 20, 2018

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.

SteakAntimicrobial 'sugar-glass' film protects food from contamination
In the future, plastic films, deli sheets, and other food packaging could provide protection against E. coliSalmonella, and other pathogenic bacteria when boosted with a virus-infused “sugar-glass” coating that also extends food freshness. Developed by researchers at McMaster University, the antibacterial coating, described in a study published in ACS Biomaterials Science & Engineering, was created by embedding phages, viruses that infect and kill bacteria, into soluble “sugar glasses”—or films—made with pullulan, a polysaccharide used to prolong the shelf life of fruits and eggs; trehalose, a sugar used as a stabilizing agent in freeze drying; or a combination of the two.  

“We found when we combined pullulan, trehalose (a disaccharide), and the phage, we were able to obtain a film (a sugar glass) that can be easily coated on paper. That sugar-glass allows preserving the ability of the phage to kill specific bacteria even after storing the paper for more than one month at room temperature,” explains study co-author Carlos D. M. Filipe, professor and chair of the Department of Chemical Engineering at McMaster University.

Although phages are naturally found in certain fruits and vegetables and have been used as a spray to inhibit bacterial growth in food, they have not been successfully incorporated into food packaging. Drying them out so they can be added to films can kill the viruses. Other methods for stabilizing phages have been problematic, requiring special handling or equipment. But by encapsulating the phages in pullulan-trehalose films, they retain their effectiveness at ambient storage conditions.  

Although various buffers were also investigated to optimize the long-term stability of the phages, the researchers found that the presence of buffers led to the formation of crystals in the film, which inhibited phage activity. It was also found that pullulan and trehalose needed to be simultaneously present in the film to provide the stabilizing effect.  

“The ability to produce packaging material that provides additional levels of food protection is certainly of great interest,” says Filipe. “We can envision the thin pieces of paper separating thick slices of meat purchased from a local deli now having the ability to protect against contamination arising from bacteria being present in the blade of the slicer. Or a butcher using paper coated with a film storing the bacteria-killing phage to wrap the meat.”  

Preserving bacteriophage activity in a dried format also has great potential for use as a coating, which can be used to create antimicrobial surfaces for food preparation and food preservation. In the future, says Filipe, additional functionality may be added. “We have a paper under review that reports on a packaging system that is able to detect and report the presence of a specific bacteria without opening the package. We are excited about that work.”



ChickpeasNew insights into improving genetic diversity of chickpea
Chickpeas are popular, but the plant’s lack of genetic diversity is a potential detriment to its future sustainability. The lack of genetic diversity in domesticated chickpeas makes them more susceptible to extreme heat, droughts, and insects, and this could have serious implications for people around the world who depend on chickpeas as their main source of protein. So scientists have turned to the plant's wild relatives to create new varieties of chickpea plants that are more diverse, genetically speaking, allowing them to withstand various environmental stresses. 

“We believe that harvesting variation from the wild relatives, which are the greatest and largest reservoir of natural genetic diversity, can improve the lack of genetic variation using a mixture of tools from classical breeding and modern biology,” says Eric J.B. von Wettberg, assistant professor of plant and soil science at the University of Vermont. “We believe that ecologically guided surveys of natural diversity can identify populations harboring useful variation for disease, drought, and other challenges, and that emerging tools in biology can guide the utilization and deployment of this diversity. We think the emerging tools in biology allow us to deploy this variation to scale, and to do it more quickly than was possible with traditional breeding alone.”   

Doug Cook, professor in the department of plant pathology at the University of California, Davis, and director of the USAID Feed the Future Innovation Lab on Climate Resilient Chickpea says that there are two key steps after collecting the genetic material from the wild chickpea plants. According to Cook, the steps are “identifying the genetic bases of key traits (we focus on drought, heat, cold, disease, plant architecture, flowering time, and insect resistance), and using knowledge of these genes, combined with molecular markers, to use a knowledge-based, technology (genotyping)-driven effort to accelerate trait introgression.”  

Knowledge of the low genetic diversity in the chickpea plant has been known since at least the 1980s when there was an outbreak of Ascochyta blight in United Nations Food and Agriculture Organization trial plots in Aleppo, Syria, says von Wettberg. Plant diseases and limited tolerance to drought are challenges. “Existing cultivated chickpea germplasm, in breeding lines and heirloom varieties across the world, has very limited tolerance or resistance to these major threats,” says von Wettberg. “Furthermore, all genetic studies of chickpea have found low variation. We think some aspects of the biology of chickpea make this lack of variation worse, but that it largely stems from demographic consequences of crop domestication and breeding. Most major annual crops have this problem to some extent. It just happens to be very pronounced in chickpea. For the food system we think the diversity problem contributes to a lack of food security, and a lack of options for consumers and industries looking for chickpea and chickpea products.” 

Cook explains that the reduced variation in the chickpea germplasm is a result of domestication and a recent shift in breeding priorities away from landrace varieties, particularly in the latter half of the 20th century. “Genome sequencing clearly shows these two distinct phases,” he says. “What it means for people and food is that our ability to improve the crop for any trait (nutrition, drought tolerance, disease resistance) is hampered, because we lack the full breadth of adaptations typical of the species as evidenced in its immediate wild ancestor.” 

The implications of the research that Cook, von Wettberg, and their other research collaborators have conducted are, as Cook says, “huge,” and may lead to increased and stabilized yields, more nutritious food, and increased livelihoods, especially for the small holder farmers who grow the majority of the crop, he adds. “We are, for example, working with a food company to evaluate the potential of wild species to deliver more sustainable sources of protein, and if successful then chickpea protein might become a significant source of non-milk–based protein in the food supply.” 

The study was published in Nature Communications.



GrapesGrape compounds may help fight depression
Bioactive compounds derived from grapes have the potential to treat and prevent depression, scientists from the Icahn School of Medicine at Mount Sinai Hospital have found. Study lead Giulio Maria Pasinetti, a professor of neurology at the school, says that the research is innovative not only because it is the first time the compounds were shown to function in this way but also because they were used to target newly discovered underlying mechanisms of the disease. Results from the study were published online last month in Nature Communications.  

The team found that grape-derived dihydrocaffeic acid (DHCA) and malvidin-3’-O-glucoside (Mal-gluc) were effective in promoting resilience against stress-induced depression in mouse models of depression by modulating inflammation and synaptic plasticity. “This is the first time either DHCA or Mal-gluc have been shown to promote synaptic stability by regulating the expression of inflammatory proteins,” says Pasinetti. “We believe this research supports new initiatives into how inflammation may contribute to depressive-like behaviors as well as provides a novel therapeutic approach toward preventing inflammation.  

“We chose to specifically investigate dihydrocaffeic acid and malvidin-3’-O glucoside because we found these two compounds both accumulated in the plasma and blood as well as regulated the expression of proteins (IL-6 and Rac1) that we showed promoted resilience against depression,” says Pasinetti. 

Depression is a common affliction. Approximately 16 million people in the United States have a major depressive episode each year, according to the U.S. Centers for Disease Control and Prevention, and it is estimated that conventional pharmacological treatments yield a temporary remission in less than 50% of patients. The disease is associated with a variety of pathological processes, including inflammation of the peripheral immune system, which is a set of biological structures and processes in the lymph nodes and other tissues that protect against disease and abnormalities involving synapses, the nervous system units that transmit and receive nerve impulses. The antidepressants that are currently available focus on neurotransmitters but do not target inflammation and synaptic maladaptations associated with major depressive disorders.



Lettuce FieldsModel farm system predicts pathogen outbreaks
Leafy green vegetables are frequently a source of foodborne pathogens. Scientists at the University of Maryland have developed the first model simulating farm systems containing soil, crops of lettuces, irrigation, food animals, and rainfall to mimic the conditions under which E. coli O157:H7 transmission can occur. 

“Over the past 35 years, the proportion of foodborne outbreaks linked to the consumption of leafy green vegetables has substantially increased,” says Abhinav Mishra, an assistant professor at University of Georgia who was the lead author of the study when he was a member of the University of Maryland research team. “Consumption of leafy greens has increased over the years, but it does not completely explain the increase in the proportion of foodborne outbreaks due to leafy green consumption.” Foodborne outbreaks linked to leafy greens encompassed more than 600 outbreaks in the United States between 1973 and 2012. Of those outbreaks, at least 50 were attributed to E. coli O157:H7. “We chose leafy greens as the crop for the model farm system because we wanted to identify the potential contamination sources behind the high number of leafy greens outbreaks,” says Abani Pradhan, an associate professor at University of Maryland who helped conduct and write the study.  

The study is the preliminary step in developing a mathematical system model to identify and understand the ways that leafy greens can become contaminated with E. coli O157:H7. “This model can predict the probability of contaminated harvests of leafy greens produced in any region subject to availability of relevant information for that region,” Mishra says. He and Pradhan believe that their model can be used to identify the potential causes of foodborne outbreaks and significantly reduce the number of outbreaks in the future. This will ultimately help the industry save money and “ensure that the consumers and regulatory agencies maintain their trust in the leafy greens industry,” Pradhan concludes.

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Published every Tuesday, this newsletter explores what are, arguably, the next big things in the science of food.