Curious Cook in the New York Times: Organic produce and yak cheese

In today's Curious Cook column I write about nutritional claims made for organic fruits and vegetables and for yak cheese made in Nepal.

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Benbrook, C. et al. New Evidence Confirms the Nutritional Superiority of Plant-based Organic Foods. The Organic Center, March 2008.
http://www.organic-center.org/science.nutri.php?action=view&report_id=126

Or-Rashid, M.M. et al. Fatty acid composition of yak (Bos grunniens) cheese including conjugated linoleic acid and trans-18:1 fatty acids. J. Agricultural and Food Chemistry 2008, 56: 1654-60. http://dx.doi.org/10.1021/jf0725225

Curious Cook in the New York Times: Wild and crazy apples

In the November 21st issue of the New York Times, I write about rare and wild apples, and apples of the future.

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Curious Cook in the New York Times: Chemical signals that boost basil flavor

In today's Curious Cook column I write about the elusive flavor advantage of organic foods, and about a simple treatment that can increase the flavorfulness of basil and quite possibly other herbs and vegetables.


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P. Maeder et al., Wheat quality in organic and conventional farming: results of a 21 year field experiment. J. Science of Food and Agriculture, 2007, 87, 1826-35. http://dx.doi.org/10.1002/jsfa.2866


H.-J. Kim et al. Effect of chitosan on the biological properties of sweet basil (Ocimum basilicum L.). J. Agriculture and Food Chemistry 2005, 53, 3696-3701. http://dx.doi.org/10.1021/jf0480804

New developments in tomato flavor, part 2: How about some lemon basil in that tomato?

The second of two recent studies of tomato flavor involves genetic engineering, and offers a scent of tomorrow's tomatoes. 

A group of plant scientists in Israel and at Rutgers and the University of Michigan reported their success in transferring a gene from the basil plant into tomato plants. This particular gene diverts molecules in the pathway toward becoming the red pigment lycopene, and sends them instead onto the pathway that generates aroma molecules. The engineered tomato plants produced fruits that were paler than usual, but also had a stronger aroma and smelled distinctly of perfume, rose, geranium, and lemongrass. More than half of a panel of taste testers preferred the engineered tomato to its unengineered parent. 

This experiment may be a harbinger of things to come, a new era of plant modification in which flavor combinations once created by cooks will be re-created--or precreated--by breeders in the plants themselves. 

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Davidovich-Rikanati, R. et al., Enrichment of tomato flavor by diversion of the early plastidial terpenoid pathway. Nature Biotechnology 2007, online publication 24 June.
doi:10.1038/nbt1312

Olive oil pungency and bitterness

Here are a couple of interesting details to add to the story of olive oil's back-of-the-throat, peppery pungency.

In 2003, a research group at Unilever reported on the sensory effects of several of the phenolic compounds found in olive oil, including the cough-inducing substance later named oleocanthal. Oleuropein, the phenolic compound that makes the fruit of the olive bitter, is water-soluble rather than fat-soluble, so it doesn't get transferred into the oil when the fruit is pressed. But a number of oleuropein relatives do end up in the oil, and the Unilever researchers tasted them in pure form. They found these compounds to contribute mainly bitterness and drying astringency, along with some numbing, cooling, sour, salty, and tingling sensations. Relatives of pungent oleocanthal also taste somewhat astringent and bitter. So an oil rich in phenolics can have a very complex taste and mouthfeel indeed.

Other studies have found that heating olive oil reduces the levels of most phenolic compounds. And pepperiness gradually fades as an oil ages. The balance of flavors in an excellent olive oil is thus temporary and so especially worth savoring when you find it. The deterioration of olive oil is slowed by keeping it cool and protected from light.

The balance of phenolics and of so of an oil's taste depends on the variety of olive, the way the oil is pressed and handled, and on the growing conditions for olive trees--especially the water supply. The olive tree is native to the arid Mediterranean and can get by with very little water. According to a number of recent reports, including one from the University of California at Davis, water stress produces very bitter and astringent olives, while copious irrigation produces olives and oils with very little bitterness, astringency, or fruity flavors. So the olive is another example of the many fruits and vegetables whose quality suffers when the plants are pampered.
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Andrewes, P. et al. Sensory properties of virgin olive oil polyphenols: identification of deacetoxy-ligstroside aglycon as a key contributor to pungency. J. Agric. Food Chem. 2003, 51, 1415-20.

Carrasco-Pancorbo, A. et al. Evaluation of the influence of thermal oxidation on the phenolic composition and on the antioxidant activity of extra-virgin olive oils. J. Agric. Food Chem. 2007, 55, 4771-80. http://dx.doi.org/10.1021/jf070186m

Berenguer, M.J. et al. Tree irrigation levels for optimum chemical and sensory properties of olive oil. HortScience 2006, 41, 427-32.

Ancient chillis

Spices and herbs are stimulants. Not necessarily pharmacological, but sensory: they stimulate our senses of taste and smell in foods that are otherwise bland. The human diet must have gotten a little boring when our ancestors first learned to cultivate grains and root crops and began to lean heavily on these starchy staffs of life, after millions of years of eating this and that as hunter-gatherers. So when did humans start spicing up their monotonous new diet? Very early--in the Americas, even before the widespread use of cooking pots, according to a new report on the archaeology of the chilli "pepper." A group of fifteen scientists led by Linda Perry of the Smithsonian Museum of Natural History published their results in this week's Science.

Chillis (species of Capsicum) originated in the Americas and are not related to the Asian black and other peppers (species of Piper). Perry and colleagues were able to identify ancient starch granules--"microfossils"-- from domesticated species of Capsicum, by their larger size compared to the starch granules of wild plants. Domesticated starch granules were found in settlements in Central and South America going back as much as 6,000 years. This is as old as the earliest possible date for the oldest known chilli macrofossils, fruits found in the Tehuacan Valley of Mexico. The most ancient sites are in what is now southwestern Ecuador, which is not thought likely to have been a center of chilli domestication, so the spice was probably domesticated elsewhere even earlier and brought there. The starch granules were found on grinding tools and in food remains along with evidence of maize, achira and arrowroot and manioc (starchy rhizome and root vegetables), squashes, jack beans, and palms. The scientists also found domesticated chilli starch in somewhat later sites across a wide region, from central Panama to the Peruvian Andes, Venezuela, and the Bahamas.

Say Perry and colleagues: "The presence of domesticated plants used as condiments rather than as staple foods during the Preceramic period indicates that sophisticated agriculture and complex cuisines arose early throughout the Americas and that the exploitation of maize, root crops, and chili peppers spread before the introduction of pottery."

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Perry, L. et al. Starch fossils and the domestication and dispersal of chili peppers (Capsicum spp. L.) in the Americas. Science 2007, 315, 986-88. http://dx.doi.org/10.1126/science.1136914

Salting tomatoes in the greenhouse

Tomato lovers know that a sprinkling of salt enhances the flavor of even the best field-ripened specimen. Some recent news that bodes well for improved flavor in greenhouse tomatoes: you can enhance tomato flavor by salting the plant as the fruit grows! At the Institute of Vegetable Science in Freising, German scientists grew hydroponic tomatoes in a solution that was 0.1% sodium chloride, about one-thirtieth the salinity of seawater. The plants produced fruits with significantly higher levels of flavorful organic acids and sugars, and as much as a third more vitamin C and beta-carotene (the precursor to vitamin A) and the antioxidant red pigment lycopene. The researchers don’t say whether the tomatoes were saltier than usual. They were smaller, so salting the growing medium may be the hydroponic equivalent of dry-farming, which restricts the availability of water to the plant and the dilution of flavor and nutrients.

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Krauss, S. et al. The Influence of Different Electrical Conductivity Values in a Simplified Recirculating Soilless System on Inner and Outer Fruit Quality Characteristics of Tomato. J. Agric. Food Chem., 2006, 441 -448. http://dx.doi.org/10.1021/jf051930a

Organic vs. conventional agriculture: stressed syrah grapes

Stress on our food plants may be hard for the plants, but good for us. Scientists are now studying the biochemical effects of agricultural practices in great detail, and one consistent finding is that plant stress--from insects, heat, sunlight, water and mineral deficiencies--can induce plants to produce higher levels of antioxidants and other phytochemicals that may be good for human health. Organic agriculture, with no pesticides or mineral concentrates, usually exposes crops to more stress, and its produce is usually higher in phytochemicals. Now, in a study of syrah grapes grown near Chateauneuf du Pape in southern France, French scientists have found higher levels of antioxidant anthocyanin pigments in the conventionally grown crop. They attribute this to the possibility that, because the grapevines were already severely stressed by heat and drought, the spraying of pesticides constituted an additional, chemical stress. If this theory is correct, then pesticides may sometimes contribute more to human nutrition than just higher crop yields and less expensive produce.

Vian M.A. et al., J. Agric. Food Chem. 2006 54 (15) 5230