By discovering a secret about the way Salmonella enteritidis cells communicate with each other, ARS scientists may be a step closer to foiling this food-poisoning microbe. Laboratory studies revealed that this type of salmonella uses a chemical called acyl-homoserine lactone in a primitive form of cell-to-cell communication that enhances, by as much as 100 times, the cells' ability to grow. Cases attributed to S. enteritidis in eggs have quadrupled in America in the past 20 years. The pathogen causes a diarrheal disease, salmonellosis. Scientists have known since the late 1960s that microorganisms can use chemicals to communicate with each other—a phenomenon known as quorum sensing. But the ARS work was the first to show that S. enteritidis uses acyl-homoserine lactone for that purpose and that the chemical is a major factor in the pathogen's ability to contaminate eggs and to spread. Meanwhile, USDA's new Hazard Analysis and Critical Control Points inspection system for food-processing plants helps keep salmonella in check.

Southeast Poultry Research Laboratory, Athens, GA
Jean Guard-Petter, (706) 546-3446, jgpetter@seprl.usda.gov

Mangoes could become even more popular with U.S. consumers, thanks to natural compounds. U.S. consumption of mangoes increased about 77 percent from 1993 to 1998. More than 95 percent of mangoes sold here are imported from Mexico and Central and South America. ARS researchers have found they can protect the whole fruit against chilling injury during storage and keep fresh-cut slices from browning and drying. When the thermometer dips below 50 °F, mango skin becomes pitted and discolored, and the flesh darkens and becomes susceptible to decay. But methyl jasmonate—a sweet-smelling compound derived from jasmine and other plants—prevents chilling injury and dramatically improves overall fruit quality, compared to untreated fruit. Researchers gave mangoes a whiff of methyl jasmonate for 24 hours at 68 °F before storing the fruit for 2 weeks at 41 °F. The treatment didn't alter normal ripening and softening processes or increase water loss. And it worked on fruits at various stages of maturity. Methyl jasmonate is safe and relatively inexpensive. Mangoes could be an attractive addition to the growing market for fresh-cut produce, but browning and drying have prevented such marketing. Using food-safe compounds derived from natural products, the researchers preserved fresh-cut mangoes for 2 weeks when stored at 50 °F. They treated the slices with a combination of hexylresorcinol, isoascorbic acid, and potassium sorbate. Then they stored the slices in plastic containers to prevent drying.

Horticultural Crops Quality Laboratory, Beltsville, MD
Chien Y. Wang, (301) 504-6128, cwang@asrr.arsusda.gov

Winemakers and food and drink processors may be among the first to benefit from new technology to quickly and easily identify spoilage yeasts. ARS scientists and researchers at Boston Probes, Inc., Bedford, MA, used the company's patented technology to develop a test kit that detects unwanted yeasts among filter-collected microbial cells. In their part of the joint project, the ARS scientists obtained and provided information on unique DNA sequences in 500 representative strains of all known yeasts classified as Ascomycetes. Their effort was the first attempt to develop a commercial use for a genetic blueprint database of an entire set of microbes. Now the ARS researchers are genetically analyzing representative yeasts in the 80,000-sample ARS Culture Collection to find how closely certain species or strains are related. An understanding of the strains' links is important to epidemiologists, as well as to companies trying to protect their patents and to researchers who want to predict a microbe's usefulness for industrial purposes. Meanwhile, the new test kit is expected to help food and drink processors detect buildups of unwanted fermentation microbes and correct the condition before massive amounts of a product must be discarded.

National Center for Agricultural Utilization Research, Peoria, IL
Kurtzman, (309) 681-6561, kurtzman@mail.ncaur.usda.gov