Our Salient Impacts of Recent Research

1. Putting Science to Work for You! Safe Production Practices for Pickled Vegetables and Dressings

Our research results and publications are used nationally and internationally as the basis for acid and acidified food-safety regulations, as well as safe production practices for manufacturers. This work has been used extensively by the pickled vegetable industry and FDA. Food safety publications can be found on the Web at https://www.ars.usda.gov/southeast-area/raleigh-nc/fsmqhru/docs/safety-of-acidified-foods/. Recent research includes the development of buffer capacity models that can be used to predict pH changes in acidic foods with the addition of food ingredients. The methods for modeling pH and results for selected salad dressing products have been published and can be accessed at https://www.ars.usda.gov/southeast-area/raleigh-nc/fsmqhru/docs/buffer-capacity-modeling/. Scientist Contact: Fred Breidt (fred.breidt@usda.gov)

 

2. Bloated and Floating Is Not How We Like Pickles. Let’s Deflate Them

New knowledge of the microbiome of fresh and fermented cucumbers has created opportunities to better understand the production of carbon dioxide in cucumber pickling. We identified two groups of bacteria that can produce carbon dioxide during a typical cucumber fermentation. Accumulation of the gas inside the fruit causes the displacement of the internal tissue that leads to the formation of hollow cavities, a defect known as “bloated cucumbers.” We further discovered that a carefully selected fermentation starter culture could prevent bloater defect by the culprit bacteria. We have named a starter culture prototype, VeggieLacto 2020. We aim to optimize the composition of VeggieLacto 2020 and develop guidelines for its incorporation in industrial-scale cucumber fermentations to prevent the defect and associated economic losses. The utilization of VeggieLacto 2020 promises to reduce the amount of carbon dioxide produced in fermentations and the need for air purging in the industrial setting. Scientist Contact: Ilenys M. Pérez-Díaz (ilenys.perez-diaz@usda.gov)

 

3. Making Sure Peanuts Are Everything You Expected

We have put into place a descriptive sensory panel for evaluation of peanuts, tree nuts, and related commodities. Members of the panel are trained using the Spectrum® Method. Some panel members have over 2,000 hours of experience using the peanut lexicon developed by our research unit in cooperation with Sensory Spectrum, Inc. The panel works with university breeding programs, other ARS units, and the private industry to describe characteristic flavors, off-flavors, texture, and appearance in peanuts and other food products for marketing purposes. Scientist Contact: Lisa Dean (lisa.dean@usda.gov)

 

4. Peanut Size and Maturity Tied to Good Taste

High-oleic peanuts have a fatty acid content that is less susceptible to rancidity and related off-flavors than peanuts with normal-oleic fatty acid content. Thus, the industry favors them given their better shelf stability in peanut-containing food products and popularity with consumers. However, there is no physical method to distinguish between the two types of peanuts, which leads to a mixed lot of peanuts in storage after shelling. Our research unit tackled the problem by determining the size and maturity relationship in the development of peanut lipids. This knowledge has helped farmers better understand the importance of producing a mature crop and enabled shellers to more efficiently use size as a factor in peanut quality. Scientist Contact: Lisa Dean (lisa.dean@usda.gov)

 

5. Establishing a Basis For Excellence in Cashew and Edamame

Sensory lexicons are the basis of descriptive sensory analysis. Each commodity needs to have a lexicon describing the attributes that define the quality of the commodity for effective sensory analysis. Our research unit has published lexicons for descriptive sensory analysis of cashews and edamame, allowing for better flavor evaluation of those products. Scientist Contact: Lisa Dean (lisa.dean@usda.gov)

 

6. The USDA-ARS Nutrient Database - FoodData Central

The USDA-ARS Nutrient Database “FoodData Central” gathers information from published evaluations of the nutrients in food products consumed in the United States. It is a singular place to find information necessary to make decisions about the nutrients provided by foods. The database can be accessed at https://fdc.nal.usda.gov/ and is regularly updated with information provided by contributors who are specialists in food analysis. Our research unit has provided updates for peanut composition to the database through cooperation with the major peanut commodity groups. Scientist Contact: Lisa Dean (lisa.dean@usda.gov)

 

7. Waste Not, Want Not?

The peanut kernel is enclosed in a thin paper-like material inside of the woody shell. This material provides protection to the peanut against both lipid oxidation and insect attack due to its high levels of chemical compounds containing phenolic moieties. These phenolic compounds taste bitter and are removed during normal peanut processing. This leads to the accumulation of hundreds of thousands of pounds of peanut skins at peanut blanchers, peanut butter manufacturing and other processing plants. This material is considered an agricultural waste product with very little economic value. Our research explored ways to change that. Using food-grade solvent extraction and encapsulation technologies, we produced a functional food additive with high antioxidant activity but no bitter taste. Further research showed its potential as a value-added food ingredient that can also increase the palatability of animal feed. Scientist Contact: Lisa Dean (lisa.dean@usda.gov)

 

8. Poultry Go NUTS for Peanuts!

In various parts of the world, peanut meal from normal-oleic peanuts (groundnuts) is commonly fed to livestock as a source of protein. In the United States, 80 percent of the peanut crop is grown to make peanut butter, cooking oil, and snack foods. Our research unit conducted poultry feeding trials utilizing unblanched high-oleic peanuts as an alternative feed ingredient for egg-producing hens and meat-type broiler chickens. These studies demonstrated that eggs produced from hens fed a diet containing unblanched high-oleic peanuts had darker yolk color and greater monounsaturated fatty acids and β-carotene content than a control group we used for comparison. Eggs produced in the control group had significantly greater saturated and trans-fat content. Moreover, chicken breast samples produced from broiler chickens fed diets containing unblanched high-oleic peanuts had reduced saturated fatty acid content relative to conventional chicken breast samples. These studies validated the use of unblanched high-oleic peanuts as an alternative poultry feed ingredient that can nutritionally enrich the birds’ eggs and meat—a win for poultry producers, consumers, and the peanut industry! Scientist Contact: Ondulla Toomer (ondulla.toomer@usda.gov)

 

9. Your Liver May Love Skins!!

Peanuts provide a dietary source of biologically active polyphenols, with the peanut skin (coat) providing the primary source of these compounds. Plant polyphenolic compounds found in green tea, blueberries, broccoli, and grape seeds have been shown experimentally to improve insulin sensitivity glucose tolerance as well as suppress inflammation and oxidative stress. Our research unit investigated the effect of dietary supplementation with peanut skin polyphenolic extracts (PSPE) on lipid and carbohydrate metabolism in mice that were placed on a long-term diet high in cholesterol and saturated fat. Study results indicated that PSPE-supplemented mice had significantly improved body weights and reduced hepatic cholesterol and lipid content compared to mice given the same diet but without the polyphenols. These findings suggest peanut skin extracts have potential as a functional food ingredient that can help prevent and/or treat fatty liver disease. Scientist Contact: Ondulla Toomer (ondulla.toomer@usda.gov)

 

10. A Quicker Way to Detect Acrylamide in French Fries

When potatoes are cooked to a golden brown or overcooked, a potentially toxic compound called “acrylamide” may form. Our research unit developed an analytical method based on near-infrared spectroscopy (NIRS) that rapidly estimates the amount of acrylamide in French fries and other fried potato products. Food processors typically spend about $250 per sample to have fries or other products analyzed for acrylamide using convention analytical procedures. With the NIRS method, this cost can drop to $25 or less per sample and takes less time for results. We also developed a predictive model that both potato and sweet potato breeders can use to develop varieties that will produce less acrylamide when fried for fries, chips, and other products. Scientist Contact: Suzanne Johanningsmeier (Suzanne.Johanningsmeier@ars.usda.gov)

 

11. The Makings of a Good Sweetpotato

Sweetpotatoes are packed with beneficial nutrients like beta carotene, calcium, fiber, and a host of vitamins. American consumers also want a sweetpotato with a deep-orange flesh color, good shape and size, and a skin color of light to medium rose, copper, or red. Sweetness, flavor, and moist texture of the cooked sweetpotatoes are also desired by consumers. Our research unit, together with our university colleagues, has worked hard to meet those expectations through a joint sweetpotato breeding program that also factors in the needs of growers and processors. ‘Covington’ and ‘Evangeline’ are examples of two recently tested varieties. We learned that consumers preferred both varieties when prepared by oven-baking compared to microwave cooking due to the contribution of the former heat treatment to heightened sweetness, flavor, and softer texture. In another study, a wide range of sweet potato varieties were studied for their chemical composition and sensory textures to find the ideal characteristics of varieties for production of sweetpotato French fries. Sweetpotato varieties grouped into those that exhibited differences in French fry inner moistness, smoothness, and cohesiveness and those that differed in overall hardness, crust crispness, and interior denseness. Several of the sensory attributes correlated with total dry matter content, which could serve as a screening tool for selecting varieties that are especially suited for French fries with consumer-desired texture attributes. Scientist Contact: Suzanne Johanningsmeier (Suzanne.Johanningsmeier@ars.usda.gov)

 

12. In a Pickle: Benefits of Fermented Cucumbers

Americans consume more than 9 pounds of pickles per year. Thus, the health of consumers in the US can be enhanced by consuming pickles enriched with certain bioactive peptides, which are short chains of amino acids that can trigger a beneficial health effect. Together with university colleagues, we developed a novel mass-spectrometry technique to study the peptides indigenous to acidified and fermented pickles, an endeavor that had previously been complicated by the high salt content of such food products. Using such novel technology, we identified, for the first time in fermented cucumbers, four peptides known to have anti-hypertensive properties—a discovery that supports the historical evidence pointing to the healthfulness of pickles. Scientist Contact: Suzanne Johanningsmeier (Suzanne.Johanningsmeier@ars.usda.gov)

 

13. Calcium Makes for an Environmentally Friendly Pickle

The U.S. pickle industry needed a way to address environmental concerns over the disposal of the salty brining solution used in pickling. Indeed, brine disposal was one of the factors that helped push the California olive pickling and processing industry out of that state and overseas in the 1980s. We set to work and found that using calcium chloride not only retained desirable firmness in cucumbers as they pickled, but the compound’s use also sped up the microbiological work of fermentation. Spent brine may even help calcium poor soils. Our unit’s close collaboration with a local pickle company facilitated the first testing of the fermentations brined with calcium chloride instead of sodium chloride on a commercial scale, starting in 2010. Scientist Contacts: Ilenys M. Perez-Diaz (Ilenys.Perez-Diaz@usda.gov) or Suzanne Johanningsmeier (Suzanne.Johanningsmeier@ars.usda.gov)

 

14. Functional Fermented Foods: Prospects for Health-Promoting Pickles

A non-protein amino acid that may be present in both fresh and fermented vegetables, gamma-amino butyric acid (GABA) has been shown to promote anti-hypertensive and anti-anxiety effects as well as improve cognitive function. We optimized a mass spectrometry-based method to quantify amino acids, including health-promoting GABA in raw, acidified, and fermented cucumbers. This showed us that the content of several amino acids differed between acidified and fermented cucumbers, including production of GABA during cucumber fermentation. Brining in lower salt (2 % sodium chloride) increased GABA formation during natural cucumber fermentation. Commercially prepared dill pickles that were fermented and packed in their original fermentation brines had the highest GABA content. These studies show that bioactive compounds were formed during natural, lactic acid fermentation of cucumber, and process modifications (i.e. lower salt fermentation without desalting or brine replacement) would further enhance and retain the content of health promoting bioactive compounds in finished pickle products. Scientist Contact: Suzanne Johanningsmeier (suzanne.johanningsmeier@usda.gov)

 

15. Accelerating Quality Determinations in Pickled Vegetables

The shelf-life of pickled vegetables is influenced by the development of an off-flavor described as “oxidized,” “old,” or “metallic.” Previous studies focused on major lipid oxidation products, which are more commonly perceived as “green” or “fatty.” We used advanced mass-spectrometry technology to investigate changes in composition that relate to the development of off-flavors during real-time and accelerated (high temperature) shelf storage of pickled cucumber. In the process, we identified several compounds highly associated with off-flavor development in cucumber pickles. Different modes of flavor deterioration occurred depending on the storage temperature. However, the speed of overall “oxidized” off-flavor development at elevated storage temperatures could be used to predict off-flavor development during long-term storage at ambient temperature. These results suggest that accelerated shelf-life models could be used by industrial producers to quickly estimate the timeline for off-flavor development and predict shelf-life. However, the models would not be appropriate for studying the chemical changes that lead to the end of shelf-life in pickled vegetables. Scientist Contact: Suzanne Johanningsmeier (suzanne.johanningsmeier@usda.gov)

 

16. An International Sensory Lexicon for Sweetpotato: Phase 1 – Uganda, Africa

Consumers all over the world enjoy sweet potato as a flavorful, nutritious, plant-based food. It is also an important staple crop in the US and around the world including sub-Saharan Africa, where the introduction of more orange-fleshed sweetpotatoes could help combat vitamin A deficiency. The adoption of new sweet potato varieties depends on market acceptance. Before that can happen, however, breeders need quantitative information on the sensory characteristics of sweetpotato to ensure the varieties they develop possess consumer-desired traits. We collaborated with the International Potato Center and RTB foods on a project to generate a universal sensory lexicon for quantitative descriptive sensory analysis of widely varying sweetpotato genotypes from different growing regions. Ugandan panelists trained in the basic tastes and principles of descriptive sensory analysis participated in a 4-day workshop for sweet potato lexicon development. Sweetpotato cultivars that varied in sensory characteristics and ranged in flesh color from cream to deep orange were selected from one of the International Potato Center’s sweetpotato breeding trials in Namulonge. Sweetpotatoes were washed, peeled, wrapped in banana leaves, and steamed. Steamed sweetpotato roots were divided into portions, individually wrapped, and served to the panelists warm. Independent sensory terms were generated to describe the appearance, aroma, flavor, and texture of sweetpotato. The sweetpotato lexicon is being used for panelist training and descriptive sensory analysis in Uganda and provided the basis for further development into a universal sweetpotato lexicon. Scientist Contact: Suzanne Johanningsmeier (suzanne.johanningsmeier@usda.gov)

 

17. Dairy-Alternative: A Probiotic, Refrigerated Pickle?

Live microbes able to confer health benefits for consumers, also known as probiotics, are desirable in a number of fermented dairy products. A probiotic pickle product would offer consumers a non-dairy, low-calorie alternative to the predominantly dairy-based probiotic food products that are currently available. Our Unit determined that probiotic cultures survive for 2 months in a simulated refrigerated pickle product with the incorporation of an ambient temperature incubation step and arginine supplementation in cover brines. Arginine is an amino acid naturally found in foods and produced by human. It was found that the use of commercial probiotic starter cultures for pickle products supplementation, that proliferate slowly in such matrix, offers an opportunity to extend the survival of beneficial microbes in finished products. To date, experimentation suggests it is possible to maintain up to 200 million of the beneficial microbes per serving, which would enable the production of healthy probiotic pickles with a 2 months shelf life. Probiotics confer therapeutic effects at a level of 1 billion cells per dose. It is predicted that increasing the number of probiotics added to the product would increase the survival proportionally, resulting in the ability to deliver enough probiotic organisms in one serving of pickles to confer health benefits. Scientist Contact: Ilenys M. Pérez-Díaz (Ilenys.Perez-Diaz@usda.gov)

 

18. Winterizing Outdoor Fermentation Tanks

Freeze damage of fermented stocks in bulk storage in outdoor tanks is of concern for pickle processors in the US as it results in yield and quality loss, primarily associated with water and tissue firmness loss. We explored opportunities to minimize freeze damage in fermented cucumbers contained in fiberglass tanks by adding insulation on the perimeter of the vessels and on top using a cover. Changes in temperature in in-tank pickles exposed to freezing temperatures were studied in the typical fermentation vessel and tanks equipped with additional insulating top covers and/or external linings. A mathematical model was developed to simulate temperature profiles. The mathematical model allowed for calculations of energy input and of the thickness of the insulating material needed for perimeter and top covers so that in-tank freezing could be minimized. Comparisons of the insulated tank configurations using the model, suggested a significant difference (up to 30 °F) in internal tank temperatures between insulating configurations. However, no significant differences in internal tank temperature profiles were observed among the insulating configurations tested in the field when ambient temperatures were below 25 °F, suggesting that hot air purging or an in-tank heating coil are necessary to prevent in-tank freezing at temperatures below 25 °F. Interestingly, the data showed that the addition of NaCl did not significantly alter freezing patterns of insulated tanks, suggesting savings may come from reduced salting without compromising the quality of the fermented stocks. Scientist Contact: Ilenys M. Pérez-Díaz (Ilenys.Perez-Diaz@usda.gov)

 

19. Winning the Bacterial Battle in a Pickle!

The development of low salt cucumber fermentations for the manufacture of a greener cucumber pickle requires the addition of a robust bacteria capable of converting the sugars naturally present in the fruit to lactic acid to assure safety and consistency in the process. Such bacteria, also known as starter cultures, are absent in culture company’s catalogs and thus unavailable to processors. Moreover, most of the commercially available starter cultures are produced in ways incompatible with the kosher requirements for vegetable products to be consumed with meats, such as hamburgers. A collection of 1200 bacteria isolated from commercial cucumber fermentation cover brines was created. Bacterial isolates identified as Lactobacillus plantarum, Lactobacillus pentosus and Lactobacillus brevis predominated in the collection and were further characterized as candidates for starter cultures. A method to produce starter cultures by the gallon in ways that Kosher requirements are met was designed in collaboration with the Orthodox Union and tested in the laboratory. To date we have identified three robust starter cultures that can be produced in-house at pickling facilities following a process that meets Kosher guidelines. We have also made one starter culture available to processors in the lyophilized (powdered) form by partnering with the private sector. Scientist Contact: Ilenys M. Pérez-Díaz (Ilenys.Perez-Diaz@usda.gov)

 

20. Are There Viruses That Infect Bacteria? Yes, And They Like Pickles Too!

Bacteria are commonly infected by viruses, known as bacteriophage, that are naturally present in the environment. While some bacteriophage infect bacteria that make human sick, those that target the microbes that make delicious fermented foods a possibility, also exist. We explored the population of bacteriophages in commercial cucumber fermentations and found eight different types able to infect undesired bacteria in cucumber fermentations and six able to invade fermenting bacteria. We continue to develop applications for these viruses intrinsic to foods. Scientist Contact: Ilenys M. Pérez-Díaz (Ilenys.Perez-Diaz@usda.gov)

 

21. A Greener and Natural Cucumber Acidification Method to Reduce Environmental Impact

Importation of gherkins or small cucumbers causes environmental pollution in the USA due to the elevated levels of acid, salt and sulfite needed to microbiologically stabilize them during long term transit from overseas. Moreover, salty preserved gherkins must be rinsed prior to their conversion as a finished product, which increases the demand for water needed for processing. Additionally, consumer trends have been demanding the removal of traditional preservatives, such as sodium benzoate, from many products, including pickles. It was determined that the preservation of cucumbers in a cover brine solution containing 1% acetic acid, 0.1% sodium benzoate, and 1.1% calcium chloride was sufficient to maintain firmness of the fruits and microbiological stability for six months of storage under anaerobic conditions. This treatment eliminates the need to desalt the preserved cucumbers reducing waste waters and water usage. Brine formulations without sodium benzoate and containing ingredients perceived as natural and healthy by consumers were also conducted. Combinations of fumaric acid or lauric arginate with several plant derived extracts were determined to prevent the growth of LAB and yeasts, respectively, during long term storage. The new preservation treatments effectively achieve microbial stability during long term storage and produce pickles with acceptable texture. The newly formulated acidification brine is been evaluated for the preservation of vegetables other than cucumbers as an alternative to reclaim vegetables and reduce food waste. Scientist Contact: Ilenys M. Pérez-Díaz (Ilenys.Perez-Diaz@usda.gov)

 

22. Learning Who is a Brigand in Brines and Who is Beneficial For Life

Understanding the roles of the indigenous microbes in fresh and fermented cucumbers needed to start with the revelation of their identities. Application of current DNA sequencing technology and bioinformatics identified the dominance of the lactic acid producing bacteria, Lactobacillus plantarum, Lactobacillus pentosus, Leuconostoc mesenteroides and Weisella cibaria in commercial fermentations. These bacteria and their metabolic activity limit or enable the growth of others such as Enterobacter cloacae and Pantoea agglomerans, which are involved in the development of bloater defect. After the lactic acid bacteria convert most of the sugars to acid, other microbes in fermentations emerge causing spoilage characterized by a rising pH and the production of malodorous compounds such as butyric acid and propionic acid. Understanding the microbial interactions naturally taking place in a fermentation system is enabling the purposeful modulation of its composition to achieve higher quality pickles with enhanced nutrition and safety. Scientist Contact: Ilenys M. Pérez-Díaz (Ilenys.Perez-Diaz@usda.gov)

 

23. Natural Probes to Validate Thermal Processing

Ways to monitor the efficacy of thermal treatments on acid and acidified foods are lacking within the food industry. We proposed the use of the artificial replication of DNA to measure the extent of a thermal treatment application in a paradigm shift. Instead of using the artificial replication of DNA using a technique known as PCR to obtain identical copies of the genetic material, we use it to evaluate DNA fragmentation as the result of thermal processing. Correlations are established between the coefficient that quantifies the difficulty in DNA replication and the magnitude of the temperature applied in a food for a given time. This technology enables the validation of thermal processes within the food industry, creating an opportunity for processors to comply with new process validation requirements imposed by the Food Safety Modernization Act. Scientist Contact: Ilenys M. Pérez-Díaz (Ilenys.Perez-Diaz@usda.gov)

 

24. Perspicacious Pickling Preservation Processes

Our research unit is the only national laboratory that works full-time on the processing of commercial pickled vegetables. With support and funding from the pickle industry, for example, we investigated how to consistently achieve Federal food safety standards without harming the quality of pickle products. In investigating pickling, we discovered that the acid itself and the low pH killed harmful bacteria and identified the conditions that are effective in killing acid resistant pathogens such as Escherichia coli. We’ve a long history of working with the industry and regulatory entities such as the FDA. You can read more about our historical accomplishments reported in Agricultural Research magazine in 2014 at https://agresearchmag.ars.usda.gov/2014/jul/pickle. For additional information please contact Muquarrab Qureshi (muquarrab.qureshi@usda.gov).