News Release

Purple sweet potatoes among 'new naturals' for food and beverage colors

Peer-Reviewed Publication

American Chemical Society

INDIANAPOLIS, Sept. 8, 2013 — Mention purple sweet potatoes, black carrots or purple carrots, and people think of dining on heirloom or boutique veggies. But those plants and others have quietly become sources of a new generation of natural food colorings that are replacing traditional synthetic colors and colors derived from beetles.

That back-to-the-future trend is on the agenda here today at the 246th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society. The meeting, which features almost 7,000 reports on new discoveries in science and other topics, continues through Thursday in the Indiana Convention Center and downtown hotels.

Speakers described how natural colors used centuries ago are making a resurgence in response to consumer preferences, manufacturers' needs and the promise that these antioxidant-rich substances may have health benefits.

"The natural colors industry for foods and beverages is gaining in value as U.S. and international companies move towards sustainable and affordable crop alternatives to synthetic red colors and red colors derived from insects," explained Stephen T. Talcott, Ph.D., who spoke at the session. "In addition to adding eye appeal to foods and beverages, natural colorings add natural plant-based antioxidant compounds that may have a beneficial effect on health."

One major change, he said, is the appearance of root crops like black carrots and purple sweet potatoes (PSPs), which are grown specifically for the natural colors industry. They have become primary agricultural products, compared to fruits such as grapes, which are grown for other purposes and used as secondary or byproduct-based colors.

Talcott, who is with Texas A&M University, focused on the range of colors — from light pink to rose, red and deep purple — that can be obtained through use of the pigments in PSPs. Available commercially in the United States since 2006, but still hard to find in stores, PSPs have the same anthocyanin pigments found in black cherries. Baked, used for french fries or prepared in other ways, PSPs taste like regular sweet potatoes, Talcott noted.

PSP anthocyanins have proven to be among the best for food and beverage coloring, he said, citing fruit drinks, vitamin waters, ice cream and yogurt. They are stable, for instance, and do not break down easily; have superior coloring properties; and have a relatively neutral taste (in contrast to the slightly earthy, bitter taste from grape-based colorings). The pigments, however, are very difficult to extract.

Likewise, PSP anthocyanins have advantages over traditional synthetic red food colorings and the "carmine" reds extracted from cochineal insects. Those include sustainability and ease of production. Cochineal insects feed on a certain type of cactus native to South America and Mexico. It takes about 2,500 bugs to produce one ounce of cochineal extract, used in ice creams, yogurts, candy, beverages and other foods.

However, PSP anthocyanins are difficult to extract. Talcott reported on development of a new process that extracts larger amounts of pigment from PSPs. Byproducts of the process include starch and fiber, which could be used as animal feed, in various food applications or as a raw material for biofuel production. Alternatively, the byproducts could simply be composted and used as a soil conditioner for producing more PSPs or other crops.

Such processes could encourage development of a domestic natural food coloring industry, with agriculture spreads devoted specifically to growing foods for use in making food and beverage coloring. Currently, the United States imports much of the natural food coloring it uses commercially. The small amounts of PSPs grown domestically go mainly to sales of fresh potatoes for the table.

Talcott spoke at a symposium, "The Chemistry of Functional Beverages," which are beverages that go beyond the basics of quenching thirst or providing nutrition: They prevent disease or promote general good health. Abstracts for the symposium appear below.


A press conference on this topic will be held Sunday, Sept. 8, at 9:30 a.m. in the ACS Press Center, Room 211, in the Indiana Convention Center. Reporters can attend in person or access live video of the event and ask questions at

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Purple sweet potato as a natural food color with bioactive properties

Steve T. Talcott, Ph.D., Nutrition and Food Science, Texas A&M University, College Station, TX 77843, United States,

The natural pigment industry is a valuable and growing segment of the US food industry, with market trends towards stable and affordable alternatives to synthetic colors. Among the natural red colors, purple sweet potatoes (PSP) is becoming an industry standard for color stability with added benefits of a healthy halo that accompanies a vegetable juice concentrate. Limited PSP processing is conducted in the US due to crop limitations and challenges related to efficient pigment extraction and isolation. The starch content of the PSP along with an exceptionally high polyphenol oxidase activity not typically found in orange varieties create additional processing challenges. During pigment extraction, these native enzymes are activated and oxidize chlorogenic acids and result in co-oxidative reactions that destroy the targeted anthocyanins. Treatments were developed to evaluate pre-heating and anti-browning agents for their role on PSP extraction and subsequent stability and their combined role served to reduce oxidation and aid in overall pigment recovery. When used in beverage applications, PSP concentrates are expected to be free of residual sugars and earthy flavor defects and exhibit excellent color stability from their varied content of acylated anthocyanins that may also possess bioactive properties beneficial for human health. Changes in phytochemistry and stability during processing and its use in food formulations will be discussed along with applications of these novel ingredients in context to food quality and potential health benefits.

Functional properties of orange juice on lipid and glucose metabolism, appetite, and oxidative stress on humans

Thais B. Cesar, Ph.D., Department of Food and Nutrition, Faculty of Pharmaceutical Science, Sao Paulo State University - UNESP, Araraquara, Sao Paulo 14802-901, Brazil,

We have conducted several studies to evaluate the effect of orange juice consumption on the risk factors for metabolic syndrome and cardiovascular diseases. In all these studies the participants have consumed orange juice regularly or an acute dose. Anthropometric, hemodynamic, biochemical, oxidative status and appetite parameters were assessed. The regular consumption of orange juice did not change the patient's body weight, percentage of fat mass, and waist circumference, suggesting that orange juice did not contribute to weight or fat mass gain. The consumption of orange juice improved the diet quality by adding important nutrients as folate, vitamin C, and calcium. The results also showed that orange juice significantly reduced serum total cholesterol, LDL-C, insulin resistance, C-reactive protein, blood pressure and increased serum antioxidant activity. We also verified in an transversal study that long term orange juice consumption, one year, was associated with low LDL-C and apolipoprotein B in normal and moderately hypercholesterolemic subjects. Appetite was also influenced by the acute intake of orange juice, and low levels of the insulin was showed after the consumption of orange juice, and leptin and adiponectin will be evaluated. In conclusion, our studies showed that orange juice consumption has promoted lipid-lowering, anti-inflammatory and antioxidant activities, which contribute to the prevention of the oxidative stress and the risk factors for diabetes and cardiovascular diseases.

Formation of polymeric pigments during chokeberry juice processing and storage

Luke R. Howard, Ph.D., Department of Food Science, University of Arkansas, Fayetteville, AR 72704, United States,

Chokeberries are a rich source of anthocyanins and procyanidins, but these compounds are unstable during juice processing and storage. Losses are accompanied by increased polymeric color values, indicating anthocyanins react with procyanidins to form polymeric pigments. In this study, polymeric pigments in samples at various stages of juice processing and pasteurized juices stored over six months at 25oC were measured by MALDI-TOF-MS in linear mode. Monomeric anthocyanins were analyzed by HPLC. Polymeric pigment signal intensities were strongest in the protonated molecular ion form [M+]. Cyanidin 3-galactoside with one (m/z 737) up to 12 (m/z 3903) flavan-3-ol units was present in all samples during processing and storage. The largest increase in polymeric pigments occurred following pasteurization, coinciding with a marked loss of monomeric anthocyanins. Polymeric pigments changed little over six months of storage despite a linear decline in monomeric anthocyanins. Thermal treatment appears to promote the formation of polymeric pigments in chokeberry juice.

Untapped capacity of phenolics

Jungmin Lee, Ph.D.,Horticultural Crops Research Unit worksite, USDA-ARS, Parma, ID 83660, United States,

My research focuses on understanding the dynamics of plant primary and secondary metabolites. Though plant metabolites, including phenolics, only make up a small portion of the compounds found in a fruit or its final product, they are crucial for their contribution towards appearance (color), taste (bitterness and astringency), storability, and potential health benefits. Everyday consumers automatically and unknowingly make purchasing decisions based upon their judgment of phenolic attributes. Precise identification of phenolic compounds is key to discerning how cultivar selection, breeding strategies, environment, post-harvest conditions, and processing methods ultimately influence beverage quality. Highlights on the elucidation and quantification of phenolics in black raspberries, elderberries, wine grapes, cranberries, and the resulting products will be presented; data can improve production and processing. Presentation will also include how (1) characterizing cultivar variability in polyphenolics aids enhanced germplasm selection in berries; (2) vineyard management regimes alter metabolites in wine grapes; (3) winemaking conditions influence wine structure; (4) fruit processing methods effect efficiency of phenolic extraction in berry products.

Modification of phytochemicals for enhancing their functional properties

Inwook Choi, Ph.D., Division of Metabolism and Functionality Research, Korea Food Research Institute, Sungnam-Si, Kyunggi-Do 463-746, Republic of Korea,,

Alcoholic liver disease (ALD) is considered as a leading cause for a liver injury in modern dietary life. This study was aimed to investigate the effects of orally administrated citrus flavonoids (CFs) and their enzymatically modified ones (EM-CFs) to prevent ALD. This study also presented effectiveness of controlling hepatic metabolism of some flavonoids to improve their anti-inflammatory activities. Through such efforts, bioavailability and functionalities of flavonoids were proven to be improved.

Formulation and dosing strategies to improve bioavailability of flavan-3-ols

Mario G. Ferruzzi, Ph.D., Department of Food Science, Purdue University, West Lafayette, IN 47907, United States,

Flavan-3-ols are a sub-class of plant-derived flavonoids commonly found in beverage products such as tea, cocoa, grapes and apples. Consumption of flavan-3-ol rich beverages has been associated with several health benefits including a reduced risk of several chronic and degenerative diseases. Several flavan-3-ol forms have demonstrated biological activities consistent with health promoting effects including the ability to modulate oxidative and inflammatory stress. While promising, physiological delivery (bioavailability) of flavan-3-ols or their bioactive metabolites from these beverages remains a critical step to positively affecting tissue specific disease risk and outcomes. Bioavailability of flavan-3-ols is dependent on numerous factors including: digestive release, intestinal transport, metabolism and distribution/elimination. This talk will focus on the impact of the food matrix (physical form, flavan-3-ol form and dose, macro/micronutrient profile) on the bioavailability and metabolism of flavan-3-ols. Formulation factors impacting stability in the GI tract and intestinal transport will be described. Additionally, the impact of repeated exposure to dietary polyphenols on absorption and metabolism of individual bioactive flavan-3-ol derivatives will be described in the context of ongoing studies defining brain-bioavailable polyphenol metabolites. Defining key factors that impact tissue specific profiles of flavan-3-ol metabolites is critical to the design of functional beverages consistent with delivery of desired health benefits.

Tannin-protein interactions -- in the lab, in beverages, and in the gastrointestinal tract

Ann E. Hagerman, Ph.D., Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, United States,

Interactions between polyphenols and proteins have been studied for many decades, with a primary focus on the noncovalent, reversible complexes that form rapidly in aqueous solution. These interactions have long attracted the interest of food and beverage scientists, since they are factors in important properties including haze formation and astringency. Recent appreciation of the beneficial health effects of polyphenols has driven additional research into interactions with proteins that may control bioactivity or bioavailability. This review will focus on the fundamental basis for polyphenol-protein interactions, with emphasis on methods used to explore the interactions, and the molecular forces that drive the interaction. Non-covalent interactions with proteins ranging from salivary proteins to therapeutic target proteins, as well as food and gastrointestinal proteins, will be described. The role of polyphenols as antioxidants will be integrated into the study of polyphenol-protein interactions by exploring the covalent bonds that form when a polyphenol is oxidized in the presence of proteins. Unanswered questions and directions for future research will be highlighted.

Antioxidant activity and chemical composition of coffees roasted under various conditions

Masumi Kamiyama, Ph.D., Department of Environmental Toxicology, University of California, Davis, Davis, CA 95616, United States,

One of the most important bioactive components in food and beverage is antioxidants, which are known to prevent various diseases caused by oxidative damage. In this study, the inhibitory effect of samples from nine commercial brewed coffees toward malonaldehyde formation from an oxidized lipid ranged from 63% to 97%. Among possible antioxidant principles, chlorogenic acids contained the highest level, followed by quinic acid, and caffeic acid. When chlorogenic acid, quinic acid, and caffeic acid were heated under various coffee roasting conditions, phenol and its derivatives were identified in the largest quantities in the heated samples. These phenols -- in particular, catechol (76%) and 4-ethylcatechol (75%) -- exhibited potent antioxidant activities. Degradation of chlorogenic acid, quinic acid and caffeic acid upon heat treatment produced additional antioxidants in roasted coffees. The results suggest that continuous ingestion of antioxidants by habitual coffee drinkers has the beneficial effect of offering protection from in vivo oxidative damage.

Determination of carcinogenic 4(5)-methylimidazole and its precursors, α-dicarbonyl compounds in Maillard model systems and commercial soft drinks

Hae Won Jang, Ph.D., Environmental Toxicology, University of California, Davis, Davis, CA 95616-5374, United States,

Caramel colors prepared for soft drinks have been known to produce bioactive compounds, such as α-dicarbonyl compounds and heterocyclic compounds via the Maillard reaction. In the present study, formation mechanisms of toxic glyoxal, methylglyoxal, diacetyl, and 4(5)-methylimidazole were investigated using Maillard reaction systems. When aqueous sucrose solutions with different pHs were heated, methylglyoxal was formed in the greatest amounts (245 µg/mL), followed by glyoxal (32.90 µg/mL), and diacetyl (14.83 µg/mL). When Maillard reaction systems consisting of D-glucose and ammonia were heated with or without sodium sulfite, diacetyl (1,588.45 µg/mL) formed in the greatest amounts, followed by 4(5)-methylimidazole (1,269.71 µg/mL) methylglyoxal (160.05 µg/mL), and glyoxal (46.12 µg/mL). Ammonia acted as a catalyst for diacetyl formation. Addition of sulfite reduced the formation of 4(5)-methylimidazole by 46%, glyoxal by 93%, methylglyoxal by 90%, and diacetyl by 80%. The results of the present study provide important information to mitigate the formation of these toxic chemicals in beverages.

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