New pastas or cookies that melt in your mouth like butter are a step closer, thanks to a key discovery about wheat proteins. ARS scientists identified the molecular basis for one of wheat's most important qualities: texture, known as hardness or softness. Bakers use hard wheats to make bread and soft wheats for cookies and cakes. Scientists have known since the 1970's that one gene controls wheat texture. It directs wheat kernel cells to make proteins called puroindolines. Until now, scientists haven't understood the relationship between puroindolines and hardness. But ARS researchers found that specific types of puroindolines (known as pinA and pinB) correlate perfectly with wheat texture. All soft wheats, including wheat's wild ancestors, have pinA and a certain form of pinB. This pinB has glycine as the 46th amino acid in the protein. The scientists tested more than 200 North American hard wheats. Most differ from soft wheat by a single amino acid, serine, as the 46th amino acid in pinB. All the other hard wheats have the glycine pinB but don't have pinA. Breeders can use this information to develop custom-designed varieties with specific puroindoline combinations, using either traditional breeding or biotechnology.
Western Wheat Quality Laboratory, Pullman, WA
Craig Morris, (509) 335-4055, morrisc@wsu.edu

A new batter being developed by ARS researchers could reduce the oil in fried chicken, fish and other foods that otherwise add fat to consumer diets. The new batter is made from rice flour rather than wheat and absorbs 60 percent less oil when fried. The difference is in the chemical constituents of the two grains. Wheat flour, the chief ingredient in standard commercial batters, helps give fried chicken its moist, golden coat and mouth-watering flavor. But gluten, an important wheat flour protein, binds tightly with oil, so more is absorbed into food. That's less of a problem with the rice-based batters, thanks to the grain's different proteins, starch and other components. Initially, scientists noticed that the rice batter didn't properly fluff up and stick to chicken meat. But they overcame the problem by first modifying the rice with several processing techniques. They are now collaborating with A and B Ingredients of Fairview, NJ, to explore the batter's commercial potential as a low-oil product for the food industry and health-conscious consumers.
Southern Regional Research Center, New Orleans, LA
Fred Shih/Kim Daigle, (504) 286-4354, fshih@nola.srrc.usda.gov

Tortilla chips fried in a monounsaturated vegetable oil produced by new sunflowers stayed fresh tasting longer than chips fried in commercial sunflower oil. The new sunflower hybrids are called NuSun. ARS food technologists say NuSun oil has a more favorable balance of fatty acids--several times more oleic acid than traditional sunflower oil and less than half as much linoleic acid. Some studies have indicated that in moderately low fat diets, a high proportion of fat such as oleic acid can lower serum cholesterol and the risk of coronary heart disease. With its lowered linolenic acid content, NuSun oil holds up well in frying vats, even without hydrogenation, a chemical process that stabilizes oils. In field tests, ARS geneticists have shown commercial and experimental NuSun hybrids equal traditional sunflower varieties in agronomic qualities such as yield potential. The researchers also found that a single dominant gene ensures any number of such hybrids can be bred to produce oil ranging from 60 to 75 percent oleic acid. This year, for the first time, NuSun is being grown on some 100,000 acres. According to industry officials, the new hybrids could well provide an impetus for doubling U.S. acreage of oilseed sunflowers from its present 2.2 million acres by 2001.
Red River Valley Agricultural Research Center, Fargo, ND
Jerry F. Miller, (701) 239-1321, millerjf@fargo.ars.usda.gov
National Center for Agricultural Utilization Research, Peoria, IL
Kathleen Warner, (309) 681-6555, warnerk@ncaur.usda.gov

E. coli bacteria that have been subjected to only a sublethal dose of heat can become more heat-resistant than bacteria that have not been exposed to such heat, ARS scientists have found. This means cooking regimens designed to kill these deadly bacteria must be based on the pathogen being in its most heat-resistant state. Pathogens previously subjected to lower heating temperatures are tougher to kill, so it's vital to adequately cook food to kill food-borne pathogenic bacteria. In tests, ARS scientists heated beef gravy samples contaminated with E. coli 0157:H7 to 114.8 F for 15 to 30 minutes. The heat did not kill the bacteria, but stimulated it so that it could adapt to the stressful heating conditions. The scientists then cooked the gravy to a final internal temperature of 140 F, killing the bacteria. Preheated E. coli survived longer--with a 1.5- fold increase in heat resistance--than other E. coli not subjected to the sublethal heat treatment. Food processors should take note that slowly heating foods to the final cooking temperatures normally used won't kill bacteria. Heat-shocking conditions may occur in minimally processed, refrigerated, cook-in-the-bag foods such as beef stew, roasts, and soups. Induced heat resistance could also be a concern in meat products kept on warming trays before final heating or reheating. Adequate cooking remains the primary means to kill pathogens in food.
Eastern Regional Research Center, Wyndmoor, PA
Vijay K. Juneja, (215) 233-6500, vjuneja@arserrc.gov

Several compounds in corn inhibit Aspergillus flavusfungi from producing aflatoxin. Among the compounds are alpha-carotene and other carotenoids that impart yellow color to modern corn hybrids. Scientists pinpointed the compounds with a new test they've developed that extracts aflatoxin from fungus cultures. The new procedure requires less extraction solvent, takes less time than previous tests, and works with samples of 1 milligram or less. In experiments, the scientists extracted aflatoxin from cultures containing compounds identical to ones found in corn. They found that A. flavus cultures grown in the presence of inhibitory compounds such as alpha-carotene contained significantly less aflatoxin. A. flavus thrives in the corn kernel's oil-rich germ and produces a majority of aflatoxin in this part of the kernel. Not surprisingly, the aflatoxin-inhibiting compounds occur more heavily in other parts of the kernel. The researchers hope their work will lead to genetically engineered corn lines that produce ample amounts of inhibitory compounds in the germ. Corn with more than 20 parts per billion of aflatoxin-- equal to just 1 ounce in 3,125 tons--is deemed unfit to feed animals that produce meat or milk for humans.
National Center for Agricultural Utilization Research, Peoria, IL
Robert A. Norton, (309) 681-6251, nortonra@mail.ncaur.usda.gov

Texture, or firmness, is vitally important to the quality and shelf life of produce. ARS scientists have cloned part of a gene responsible for making an enzyme that breaks down the cell wall in tomatoes, causing softening and other texture changes that lead to decay. Enzymes cause several changes in cell walls as tomatoes ripen; these enzymes include a group called beta- galactosidases. ARS scientists identified and cloned a family of seven beta-galactosidase genes in tomatoes, including one that degrades cell walls. Two research groups in Great Britain are collaborating on studies to understand the gene's role in fruit softening. Transgenic plants carrying the cloned gene are expected in a year.
Horticultural Crops Quality Laboratory, Beltsville, MD
David Smith, (301) 504-6128, dsmith@asrr.arsusda.gov

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