Ruplal Choudhary, a bioprocess engineer and associate professor of plant, soil and agricultural systems, is using infrared light in his nutrition lab to determine not only fats, proteins and carbohydrates but also the phytochemical, antioxidant and carotenoid protein make-up of produce. (Photo by Russell Bailey)
July 07, 2016
Researchers shining light on food waste, freshness
CARBONDALE, Ill. – From the turnip that falls off the truck to the yucky stuff we scrape off our plates, food waste in the United States accounts for 30 percent to 40 percent of the food supply. That’s about 133 billion pounds of food or approximately $161 billion annually.
Ruplal Choudhary, a bioprocess engineer and associate professor of plant, soil and agricultural systems, and other researchers at Southern Illinois University Carbondale are working at several stages of the farm to table (and beyond) cycle to find ways to reduce waste without sacrificing nutrition and taste.
Choudhary began looking at uses for infrared light in food processing when he was still a graduate student. Near-infrared (NIR) and mid-infrared (MIR) spectroscopes are becoming more common to determine fats, proteins and carbohydrates in nutritional analysis, but Choudhary also uses the spectroscopes to determine the phytochemical, antioxidant and carotenoid protein make-up of the produce.
Phytonutrients are health-boosting qualities of food occurring naturally in plants that have particular health effects. For example, glucosinolates, a class of phytonutrient, appear in cruciferous (green leaf) vegetables and give those vegetables their odor and flavor. Research suggests that glucosinolates are useful in slowing or stopping the development and growth of cancer.
Recently he was part of a research team funded with an Illinois Department of Agriculture specialty crop block grant to study Asian greens. Other researchers focused on growing 35 different varieties, including bok choy, bekana and Komatsuna, to determine which greens will grow best in Southern Illinois and which would prove most appealing to the local palate. Choudhary and a team of graduate student researchers handled the phytonutrient and antioxidant analysis of the greens.
He’s building a database of known analyses to “train” the spectroscopes in his lab. As the database grows, use of the spectrometer becomes more efficient.
In addition to the spectroscopes, he uses a camera to record the color and texture of fresh produce. Together with the spectroscope, he can even predict taste qualities such as sweetness or crispness. He hopes that the technology he’s using in his lab will find its way to food processing, making sorting fresh produce more efficient.
In a study, conducted with Alan Walters, professor of plant, soil and agricultural systems, he used the spectroscope in the nutrition lab to help the research team determine how harvest-time affects the nutritional value of produce. The team harvested produce at various stages of ripeness and found that the more ripe the fruit or vegetable when harvested, the better its nutritional value. In addition, the team checked nutritional levels after harvest at same day, next day, and after a week. They found that post-harvest nutritional levels declined over time.
This study clearly indicates that for optimum nutritional value, produce should not be harvested early nor should it sit around for a long time in storage. However, that’s a problem for major retailers of fruits and vegetables. It takes time to harvest produce and ship it -- which is why some produce is harvested early and allowed to finish ripening post-harvest. In addition, for a grocery store, quantity and choice is part of marketing – but that can contribute to fresh produce staying in the store longer than a day, two days or even a week.
The problem goes beyond declining nutritional benefits. The longer produce sits, the more likely it is to spoil. And that contributes to food waste. Chaudhary is part of a team of SIU researchers that is seeing a different kind of light when it comes to preserving food freshness.
Ultra-violet light seems an unlikely ally in the quest to preserve the freshness of fruits and vegetables. However, UV sterilization or UV irradiation can kill a list of things that lead to food spoilage, including viruses, bacteria, molds and yeasts.
Ultraviolet light is classified by wavelength. UV-C has the shortest wavelength and is germicidal. It deactivates the DNA of pathogens, which prevents them from multiplying and spreading disease. Irradiation is already a common application to disinfect and sanitize drinking water and even to disinfect the air and food contact surfaces.
Food processors have been applying UV-C lights to reduce dangerous pathogens in food and beverages as well, particularly in dairy products and fruit juices, for some time. Researchers are finding applications with a wide range of other foods, including fresh produce. UV-C light, which kills E. coli and salmonella among other well-known bacteria, can also contribute to preserving freshness.
However, the technology can be costly and the research is far from complete.
Choudhary and Dennis Watson, associate professor of plant, soil and agricultural systems, are working now on cost-effective “smart technology” ways to implement UV-C irradiation at the retail level for fresh produce. They’ve tested the effectiveness of UV light on blueberries and strawberries and they know it works to kill the bacteria and germs that lead to fruit spoilage. But there’s a problem – UV light is hot. Using UV light to keep berries fresh ends up cooking or drying them.
The team began working on a cooler that would use UV light to keep the produce fresh but also neutralize the heat the light generates. To make the cooler more energy efficient, Watson is working to build in smart technology. High humidity makes it easier for bacteria and other food nasties to grow. Watson wants the cooler to chill extra when humidity is high, and to take it easy when humidity is lower. He’s working on a humidity and temperature sensor that will automatically adjust cooling in relation to humidity.
Choudhary and Watson hope this combination of UV light and smart cooling will eventually be available to grocery retailers to use in their storage areas. If they can keep food fresh longer, certainly that ought to contribute to a reduction in food waste. And if the technology works well enough to allow for later harvest, consumers wouldn’t miss out on the enhanced nutritional value of in-the-field ripening.
Meanwhile, Choudhary is exploring natural phenolic compounds to use with the UV light for freshness. In an experiment with strawberries and blueberries kept fresh longer under UV light, he also used limonene, a citrus-based compound that works as a natural anti-microbial. The limonene discourages fungus-growth on the post-harvest berries. With the UV light and limonene combination, the team kept berries fresh for two weeks and edible with some shrinkage for three weeks. This compares favorably to the one week of freshness for non-treated berries that is typical.
Choudhary hopes to see the UV light coolers and natural food treatments applied to large scale grocery store short-term food storage.
He may be able to assist artisan food producers now. Choudhary said he has helped local food producers meet FDA labeling requirements with proper nutrition analysis.