A greener approach to New Mexican produce opens up opportunities for sustainable baking
Author: Mollie Rappe
Courtesy article SandiaLabNows
Every August and September, the unmistakable pungent aroma of roasted green chiles permeates the air throughout New Mexico and neighboring states.
This delicious dish of regional cuisine is green in color, but roasting chili peppers to deepen the flavor and make it easier to remove the inedible skin is not environmentally friendly.
In New Mexico alone, burning propane to roast peppers results in the seasonal emission of approximately 7,800 metric tons of carbon dioxide—the equivalent of driving 1,700 cars annually.
Sandia engineer Ken Armijo, who grew up on a chile farm in Sabinal, located between Albuquerque and Socorro, thought there was a “greener” way to roast green chiles. The results of his experiments roasting chiles with concentrated sunlight will be shared at the American Society of Mechanical Engineers conference on energy sustainability this July.
“The principle behind this research was to see if high temperature roasting of food, not just peppers, could be done on solar power and produce comparable results to traditional propane roasting, and the answer is yes,” said Ken. “We used green chiles to represent the culture of New Mexico. The combination of the state-of-the-art facilities and research at Sandia National Labs with the culture, food and people of New Mexico is so special. What other national laboratory in the world would do that?”
Ken harnesses the power of the sun at the Sandia National Solar Thermal Test Facility to explore new ways to capture the sun’s energy for electricity and industrial process heat.
Solar Roasted Green Chili
For decades, Sandia has developed technologies that convert renewable sources like wind and sunlight into electricity and useful heat without producing greenhouse gases. Real-world demonstration of these technologies provides valuable testing and validation. Ken’s demonstration of using solar energy to roast green chiles could inspire new applications of solar technologies and new avenues of research.
With the help of several Sandia engineers, technologists and interns, Ken brought a traditional steel drum chili roast to the top of a 200-foot tower at the Sandia National Solar Thermal Test Facility and protected the rotor mechanism from the intense heat of the sun.
Ken’s father, a Chilean farmer and roaster, donated several bags of green chiles and his experience in judging properly roasted chiles. Ken’s father grows organic, heirloom chilies from seeds passed down through generations.
Using 38 to 42 of the 212 heliostats — mirror-like devices used to focus sunlight — in the thermal test facility, Ken was able to achieve temperatures above 900 degrees Fahrenheit evenly across the firing drum, he said. This is comparable to the temperature of a traditional propane chili roaster.
He used concentrated solar energy to roast three 22-pound batches of green chiles: two that were washed just before roasting and one that was dry-roasted. Washed chiles took slightly longer to roast than dry chiles, but the amount of char was more uniform, and green chile connoisseurs preferred the flavor profile, Ken said.
After that, Ken’s team took chili roasting back to the ground and roasted three more batches of green chili using traditional propane. Propane was slightly faster, taking four minutes to roast a washed chile compared to six minutes for the fastest solar water chile roast. With further experimentation and using more heliostats, Ken thinks he can roast the chilies even faster than with propane, but he didn’t want to fry the chilies during his first experiments.
“With solar baking, we’ve actually been able to achieve a more even distribution of heat,” Ken said. “With propane grilling, you just get the heat where the burners are, but all the chili piled on top doesn’t really heat as efficiently. With our infrared cameras, we saw that with solar cameras, it is more uniform. Essentially, the heat reaches the entire chili in the front part of the roast. In practice, this has a lot of potential for faster, better quality, and greener chili roasting.”
“Green”, green chili
For each traditional propane roast, Ken recorded the amount of propane used to roast 22 pounds of green chiles and found that switching from propane to solar would reduce greenhouse gas emissions by 2.68 pounds per 22 pounds of green chiles roasted. If the entire state of New Mexico switched to solar chile roasting, the net result would be equivalent to planting 130,000 tree seedlings and letting them grow for 10 years a year.
It’s great to roast green chilies sustainably; however, if consumers do not like the taste of solar water roasted chile, it will never be accepted. This is where the second part of Ken’s study comes in.
Ken introduced 14 green chile connoisseurs to both solar-roasted chiles and traditional propane-roasted chiles and quizzed them on the various qualities of chiles. He found that, on average, respondents preferred solar-roasted chilies by 18% for taste, 12% for smell, and 2% for easier peeling of the inedible skin. However, subjects preferred the propane-fried texture by 4%.
“I did a survey and overall, participants preferred solar-fired chiles over propane-fired ones,” Ken said. “That was shocking for me. They preferred the taste because it didn’t taste as burnt. They said it was just tastier than green chili.”
From portable roasters to coffee beans
Ken admitted that it was not feasible to build a heliostat tower and field just to roast food like green chilies, coffee or grains. However, he and his colleagues are investigating a much smaller and more modular solar roasting system that could be brought to farmers’ markets, grocery stores and Chilean festivals to roast small batches of green chiles, such as propane-burning steel drum chiles. roasters currently in use.
“I hope that in the future, Chilean roasters will be arriving at farmers’ markets and festivals with a trailer with a modular roasting mirror,” Ken said. “They just pour in the chili, point the system at the sun and let it bake. That would be great.”
But Ken says solar roasting isn’t just for green chiles. Concentrated sunlight can also be used to roast other foods such as soybeans at 840 degrees Fahrenheit for animal feed and human consumption; beer grains at 200-400 F; almonds and cashews at about 300 and 266 F; and even coffee. French roast coffee is roasted until the beans reach a temperature of 464 F, and coffee beans are roasted to 350-400 F for light roast coffee. Traditionally, fossil fuels such as propane or natural gas are used for these processes.
New Mexico has practically perfect weather for solar baking, with an average of 300 days of sunshine each year, Ken said. Many other crop production locations also have plenty of sunny days. The almond producing region of California has 260 days of sunshine, especially in the summer and fall. In fact, two companies in California are working on pilot plants to use concentrated solar energy for lower-temperature processes, such as almond pasteurization. Coffee farmers in Colombia, Ecuador and Peru grow and roast at high altitudes, which is also perfect for using solar energy to roast coffee, Ken added.
When it comes to the future of green food fried on solar water, the sky’s the limit.
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