In a ground-breaking study, ARS scientists screened broccoli varieties to see if they induce activity of a key enzyme in the human body that may protect against certain cancers. Working with researchers at Johns Hopkins University's School of Medicine, Baltimore, MD, the scientists evaluated a diverse collection of broccoli (Brassica oleracea) varieties for their ability to stimulate what's called a "mammalian detoxification enzyme," which helps protect mammals-including humans—against development of cancer. In 1996 and 1997, the scientists grew 71 USDA broccoli varieties and 5 commercial hybrids in the field and took extracts from each. The team looked for a chemoprotective compound called glucoraphanin in the extracts. A derivative of glucoraphanin spurs mammals to activate detoxification enzymes. Broccoli florets and young seedlings are rich sources of glucoraphanin and its breakdown product, sulforaphane, which is a potent inducer of mammalian detoxification enzyme activity and inhibits early tumor growth in rodent models. The scientists found a 30-fold variation in glucoraphanin content and enzyme activity among the broccoli varieties tested. Breeders may be able to exploit such variation to develop new broccoli varieties with greater levels of the protective compounds.

U.S. Vegetable Laboratory, Charleston, SC
Mark Farnham, (843) 556-0840, mfarnham@awod.com

When cooking ground beef, relying on color to determine doneness may be a mistake, according to ARS researchers. They made this finding while testing a summer ritual: cooking burgers on a gas grill. As expected, the longer the burger was cooked, the less pink the center portion. But burgers removed from the grill with pink centers continued to brown for several minutes. Ground beef cooked to 135 degrees F and allowed to sit for about 4 minutes looked the same as a burger cooked to 160 F. Burgers with a brown center are not necessarily safe to eat. Premature browning was not evident in frozen patties that were thawed and then cooked. But beef frozen in bulk, thawed, formed into patties, and immediately cooked showed brown color at unsafe temperatures. Only 5 percent of consumers use a meat thermometer during cooking. Most rely on color as an indicator of when meat is done. The temperature at which E. coli is killed, 160 dgrees F, is considered the threshold for safe consumption of ground beef.

Food Technology and Safety Lab, Beltsville, MD
Bradford W. Berry, (301) 504-8994, bberry@anri.barc.usda.gov

The Hydrodynamic Pressure (HDP) Process–known to make whole-muscle meats more tender-may also reduce foodborne pathogens like Escherichia coli, ARS researchers report. E. coli and other pathogens can live and grow on meat and cause foodborne illness if the meat is improperly handled and eaten. In conducting tenderizing experiments with HDP, an added benefit arose—treated meats seemed to have less bacteria on the surface of the meat than before. Scientists already proved that HDP penetrated throughout whole cuts of meat, making them more tender. At that point, they wanted to see if bacteria were reduced throughout ground meats as well. Ground meat samples examined immediately after HDP treatment showed reduced levels of shelf-life bacteria. Additional studies showed HDP-treated ground beef, seeded with E.coli 0157:H7 before treatment, had no detectable levels of the organism afterward. While these bacterial reductions are encouraging, further studies are necessary to determine if HDP can be commercially viable for microbial supression.

Food Technology and Safety Laboratory, Beltsville, MD
Morse Solomon, (301) 504-8463, msolomon@anri.barc.usda.gov

Dioxins, a family of chlorinated compounds which includes some that are highly toxic, can be detected in concentrations as low as 0.1 parts per trillion in fat samples. New, cost-saving technologies that ARS scientists developed to detect the dioxins can help provide assurance that food produced, consumed, or exported is safe. When the researchers began dioxin research in 1994, analysis cost nearly $2,000 per sample. Even though it's now down to about $600 to $800 per sample, the scientists are developing an even more efficient procedure—an immunoaffinity column method—which requires minimal use of chemical solvents and is expected to reduce present analysis costs by half. Dioxins, produced by natural or industrial processes, are chlorinated aromatic compounds that can build up in the fat of humans and animals and may increase the risk of tumors and possibly other undesirable health effects. In a mid-1990s study on the extent of dioxin contamination in livestock, the scientists researched dioxin levels in beef produced in 13 states. They found that, with some outstanding exceptions in the kidney fat of some individual carcasses, samples were generally "clean." Now, USDA's Food Safety Inspection Service is again surveying meats for dioxin contamination to get a better picture of the background levels in the U.S. food supply. ARS scientists are researching ways to minimize the burden of dioxin compounds that persist in the animals' bodies.

Animal Metabolism-Agricultural Chemicals Research, Fargo, ND
Janice K. Huwe, (701) 239-1288, huwej@fargo.ars.usda.gov

Honeydew aficionados gave a higher thumbs-up to fresh, ripe honeydew melons if they were dunked whole into a calcium solution before going into commercial storage for up to 3 weeks. ARS consumer preference panelists evaluated cut melon cubes for appearance, texture, and taste. Earlier research had shown the new handling procedure prolonged the market life of ripe melons up to 2 weeks beyond the normal shelf life of 7 to 12 days. The soaking supplied extra calcium that, in ripe melons, steadily migrates from the rind to the seeds. Rinds need calcium to maintain a degree of firmness that protects against spoilage. Even before the latest findings, growers and melon marketers were taking interest in the treatment to prolong shelf life and maintain quality. Now, Albion Laboratories, Inc., Clearfield, UT, a manufacturer and exporter of dietary supplements, vitamins, and minerals, is planning to expand production of amino acid-calcium chelate to help meet new worldwide demand for melons. The company has entered into a 1-year cooperative research and development agreement with ARS to study treatments of honeydews and cantaloupes still on the vine as a supplement or alternative to postharvest treatments. Per capita melon consumption in the U.S. reached new highs in the 1990s, thanks largely to sweeter, more nutritious varieties. The calcium treatment may further boost melon consumption by paving the way for extensive domestic and export marketing of vine-ripened fruit.

Crop Quality and Fruit Insect Research, Weslaco, TX
Gene E. Lester, (956) 447-6322, glester@weslaco.ars.usda.gov

More phytosterols–plant compounds associated with lowering cholesterol in humans—can be extracted from corn fiber and bran oil using an ARS-refined processing method. ARS researchers joined two environmentally friendly processing techniques, supercritical fluid extraction (SFE) and supercritical fluid fractionation (SFF), in laboratory studies that yielded up to 11 times more phytosterols from corn bran oil and 2.3 times more from corn fiber oil. Phytosterols and other "nutraceuticals," as they are also called, occur in low levels in plants. The researchers increased the amount of phytosterols from 1.3 to 14.5 percent per 100 grams of corn bran. Applying the extraction methods to corn fiber increased yield of phytosterols from 23 percent to 53 percent. Other ARS scientists have recently shown that ferulate phytosterol ester (FPE), compounds in corn bran, can lower cholesterol in humans. Commercial products containing FPEs include margarine spreads. Using "green" processing to provide alternative sources of phytosterols will also enhance agriculture by increasing value-added uses for by products of the oilseed and milling industries. Other plant sources of important phytosterols include rice bran and soybeans.

National Center for Agricultural Utilization Research, Peoria, IL
Scott L. Taylor, (309) 681-6204, taylorsl@ncaur.usda.gov

Edible films made from pureed produce can add shelf life, flavor, and nutrition to food products. Use of fruits and vegetables can also be increased through this technology. ARS researchers developed the films from produce such as apples, oranges, carrots, and strawberries. The thin, opaque films can be applied to everything from sliced apples to cuts of meat. In laboratory experiments, the films controlled browning and prevented moisture loss better than several other types of coatings. The films could also provide new flavor combinations, such as a strawberry film on cut bananas or an apple glaze on pork. Sheets containing pureed fruit have long been available as snack foods. But this is the first time thin sheets of up to 100 percent fruit or vegetable material have been tested to enhance storage and flavor. ARS has applied for a patent on the edible films (Application No. 09/330,365).

Process Chemistry and Engineering Research Unit, Albany, CA
Tara McHugh, (510) 559-5864, thm@pw.usda.gov

ARS researchers are closer to providing industry with tools to develop a delicious, vine-ripened tomato that survives a week of shipping and handling and still remains firm on the kitchen counter for another week or more. They have identified new genes involved in turning a firm tomato into mush. In the process, they produced vine-ripened tomatoes that were 40 percent firmer than unmodified siblings and stayed firmer for at least 2 weeks. The plants were engineered with a reversed gene for an enzyme that removes a sugar from cell walls. The reversed gene actually blocks removal of the sugar galactose, thus helping to keep the tomato's cell walls firm. Those firm tomatoes support the theory that loss of galactose plays a key role in the loss of structural integrity of cell walls. Structurally sound cell walls are essential to tomato firmness. The researchers focused on galactose because it's the sugar that changes most throughout fruit development. They actually identified and sequenced seven different genes that code for the galactose-removing enzyme, called beta galactosidase. They have inserted five of those genes into the tomato genome but have so far tested tomatoes with only one of the reversed, or antisense, genes—number 4. U.S. and international patent applications on all seven genes has been filed for ARS. With growing competition in today's fresh tomato market—worth nearly $1 billion in 1999—the time may be ripening for a tasty tomato that ages gracefully.

ARS Produce Quality and Safety Laboratory, Beltsville, MD
Kenneth C. Gross, (301) 504-6128, grossk@ba.ars.usda.gov
David L. Smith, (301) 504-6128, smithd@ba.ars.usda.gov