Rice processing research points to evolving milling rates as quality factor
April 27, 2026
By John Lovett
University of Arkansas System Division of Agriculture
Fast Facts
- Research suggests commingling certain cultivars is a source of decreased head rice yield
- Rice breeding requires regular evaluation of milling parameters
- Miniscule amount of over-milling cuts head rice yield by about 2 percentage points
(1,116 words)
Download PHOTOS of rice and the researchers
FAYETTEVILLE, Ark. — Research by the Arkansas Rice Processing Program is showing valuable insights for rice farmers that affect their take-home pay and the quality of rice for food makers.
Over the past two years, in cooperation with the global food corporation Mars and several rice farmers in Arkansas, researchers with the Arkansas Agricultural Experiment Station’s Rice Processing Program have dug into the problem with declining head rice yields, or the total weight of unbroken rice kernels after milling.
All signs point to the effects of commingling cultivars with variable milling rates as a primary cause for lower head rice yields, said Griffiths Atungulu, an agricultural engineer, professor of food science and director of the Rice Processing Program for the experiment station, the research arm of the University of Arkansas Division of Agriculture. Atungulu is also part of the Dale Bumpers College of Agricultural, Food and Life Sciences at the University of Arkansas.
“In general, head rice yields have been declining over time,” Atungulu said. “Rice acreage has also decreased. However, grain yield per acre has continued to increase, particularly with the adoption of hybrids.”
Milling rates evolve
While it was known that different rice cultivars have different milling rates, Atungulu said the rates are constantly evolving with the development of new varieties that improve yield and environmental adaptation. Milling rates are dictated by bran layer thickness, other husk characteristics and sometimes the inherent resistance of cultivars’ rice kernels to breaking.
To obtain representative data for the two major rice-growing regions of Arkansas, the research included the most popular rice varieties grown in the state on test plots at the Division of Agriculture’s Rice Research and Extension Center in Stuttgart and Northeast Rice Research and Extension Center in Harrisburg.
Be aware of cultivar milling rates
Bigger yields out of the field do not always translate to higher head rice yields, Atungulu said.
“We are showing here, very clearly, that we need to be very aware of the milling rates of different cultivars,” Atungulu said. “Some cultivars tend to mill faster and some mill more slowly. If you are going to do a commingling, then you want to commingle them in a manner that they are going to mill at the same rate.”
Some cultivars are more sensitive than others to milling, he noted, but over-milling by even 0.1 percentage point of surface lipid content, which indicates the degree of milling, can happen in seconds and cause a nearly 2 percent drop in head rice yield, he said.
“This is something that mills, if they are aware, can make room for, whenever possible,” Atungulu said. “We need to do identity preservation, and you will not hurt your mill’s milling rates. And then it’s better for them, better for the farmer, and the consumer. However, it is understandable that challenges can sometimes arise in practice when multiple varieties arrive at the mill simultaneously.”
Continual evaluation is necessary
Kaushik Luthra, an assistant professor in the department of biological and agricultural engineering and extension engineer at the Northeast Rice Research and Extension Center, has been a part of the studies in both his current role and previously as a postdoctoral fellow working with Atungulu. He works closely with farmers and industry partners to translate the research findings into practical strategies that improve rice quality and profitability.
“I have seen firsthand how differences in milling rates among cultivars can significantly impact head rice yield and commingling is a critical factor,” Luthra said. “I strongly agree with the emphasis on addressing commingling as a critical factor. It is also encouraging to see the end-use companies like Mars taking the lead in addressing these challenges.”
Some of the research into commingling different rice varieties overlapped with project funding from the Arkansas Rice Research and Promotion Board, Atungulu said, to address concerns over milling yields, which includes the weight of both whole and broken kernels after milling.
“We put the two projects together,” Atungulu said. “The continual evaluation and understanding of these dynamics are very important for the industry.”
Abhay Markande, principal scientist and manager of Mars Food and Nutrition’s rice program, said the research collaboration demonstrates how land-grant university research and industry engagement can drive lasting change in rice production and performance.
“What began as a research collaboration has evolved into a unified, science-led movement that strengthens resilience and unlocks future growth in rice,” Markande said.
The joint research is “delivering measurable impact that demonstrates how harvest conditions and rice variety influence head rice yield and end-use performance,” he added.
Impacts of harvest moisture content
The amount of moisture in the rice grain at harvest is also related to head rice yield, Atungulu said. Generally, the lower the harvest moisture, the lower the head rice yield.
“When you have a low moisture content, there is a high probability that rice has stayed in the field for a substantially long time,” Atungulu said. “It means it has absorbed moisture, released moisture, absorbed moisture, released moisture — that process leads to cracking in the field.”
The research indicated that the impacts would be the same for the long grain and medium grain rice varieties most commonly grown in Arkansas, Atungulu added.
Rice farmers commonly harvest rice once its moisture content reaches 20 percent. Some farmers also store their rice in silos and begin the drying process to an optimal range of 12.5 percent to ward off mold growth and help maintain the rice’s structural quality, improving head yield.
The Arkansas Rice Processing Program has developed guidelines for on-farm drying systems in silos that account for weather conditions and initial rice moisture content.
‘It all goes back to the milling’
Companies that use rice in food products depend on specific parameters for consistent operations, including functional qualities that depend on the chemical composition of the rice.
“The more you dig into the endosperm, the more you are losing on functionality — the way it's going to cook, the way it's going to absorb moisture, the way it is going to rehydrate, the viscosity … it's all going to depend on the chemistry of that rice,” he said. “All of that relies on how that rice was milled. It all goes back to the milling.”
The rice kernel consists of several parts, but the endosperm is the largest. It accounts for about 70 percent of the kernel’s weight and is mostly starch, the part that becomes white rice.
Heading into the Industry Alliance Meeting
Atungulu and Luthra will present related research findings at this year’s Rice Processing Program Industry Alliance Meeting, May 19, at the Don Tyson Center for Agricultural Sciences in Fayetteville.
“Working alongside industry partners, we are helping bridge the gap between research, growers and the food industry,” Luthra said.
To learn more about ag and food research in Arkansas, visit aaes.uada.edu. Follow the Arkansas Agricultural Experiment Station on LinkedIn and sign up for our monthly newsletter, the Arkansas Agricultural Research Report. To learn more about the Division of Agriculture, visit uada.edu. To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit uaex.uada.edu.
About the Division of Agriculture
The University of Arkansas System Division of Agriculture’s mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation’s historic land grant education system.
The Division of Agriculture is one of 20 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on three system campuses.
Pursuant to 7 CFR § 15.3, the University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services (including employment) without regard to race, color, sex, national origin, religion, age, disability, marital or veteran status, genetic information, sexual preference, pregnancy or any other legally protected status, and is an equal opportunity institution.
# # #
Media Contact:
John Lovett
U of A System Division of Agriculture
Arkansas Agricultural Experiment Station
(479) 763-5929
jlovett@uada.edu