Curious Cook in the New York Times: Heating with microwaves

In this month's Curious Cook column I write about the peculiarities and powers of the microwave oven.

Curious Cook in the New York Times: Heat

In today's Curious Cook column, I write about the ins and outs of an important but invisible ingredient in most cooking: heat energy.

Curious Cook in the New York Times: Potato chips

In today's Dining section of the Times I write about potato chips: the sounds they make, the music that has been made from them, and the forces that shape them.

My source for those shaping forces was Paul Green, a professor of plant biology at Stanford, and a friend. Paul died in 1998. In the column he became "Mr. Green." When I find a near-perfect chip and think of him, I don't think of Mr. Green, I think of Paul.

For helping me understand and explain the physics of chip shape, I thank two people who worked with Paul as postdoctoral fellows: Jacques Dumais of Harvard University and Sidney Shaw of Indiana University. Of course the simplifications and approximations are my doing, not theirs.

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Kim, S.-E. et al. Development of a method for the musical expression of cognitive food taste. Food Sci. Biotechnology 2005, 14, 738-42.

Zampini, M. and C. Spence. The role of auditory cues in modulating the perceived crispness and staleness of potato chips. Journal of Sensory Studies 2004, 19, 347-63.

Green, P. Transductions to generate plant form and pattern: An essay on cause and effect. Annals of Botany 1996, 78, 269-81.

Curious Cook in the New York Times: Vodka in the fish fry

My column in today's New York Times Dining section is about a batter for fried fish developed at The Fat Duck, Heston Blumenthal's restaurant west of London. I first enjoyed the very crunchy crust it makes last spring, when Christopher Young, the restaurant's research manager--yes, they do enough research at The Fat Duck that it needs managing!--demonstrated it at the Greystone campus of the Culinary Institute of America. The key ingredient is alcohol. In an email, Chris explained how vodka ended up in a beer batter. Heston and his colleagues were doing a cookbook and TV series on popular British foods, and developing an updated recipe for fish and chips.

The story with the fish batter was that we had developed a really fantastic batter recipe using special starches from National Starch. By using these, along with the siphon to create a very irregular foam structure (an idea that based on the work of Julian Vincent at Bath University and the mechanics of brittle fracture) we created a really outstanding batter that would cook fast enough so that the fish wasn’t over cooked, but stay crisp for a good 20+ minutes. The only downside to this was that no one could recreate this batter at home.

We mostly dealt with this “pickle” by waiting for divine inspiration. That occurred one afternoon at my house when I was reducing alcohol for a sauce and while I had my back turned it boiled away to nothing. I was reminded that alcohol takes far less energy to evaporate than water. I thought it might be possible to reduce the amount of water in the batter by replacing it with alcohol and creating a batter that would cook faster. The added bonus was that alcohol destabilizes the foam, which creates a more inhomogenous structure, which makes the batter crisper!

There was a bit of trial and error, because you do need some gluten or the batter just “blows” off the fish. It seems that a final alcohol content of around 20% seems about right.

Inspiration favors the prepared mind!
For the other big advantage that alcohol brings to a batter, see my column. The Times also gives an adaptation of the Fat Duck's recipe for siphonless cooks.

Rice: Old and new flavors; cooking; parboiled

A last installment (for the time being) of rice news.

Old and new Japanese As I've mentioned, Japan generally prefers their rice as fresh as possible; new-harvest rice is prized. Japanese scientists looked at the flavor changes that take place during aging, and found some pretty significant changes. The acidity of the grain increases, probably because oils are broken down into free fatty acids--the same molecules that also cause a firmer, dryer texture. This effect can be minimized if the rice is washed before cooking. The sucrose sugar in the grain is broken down into a mixture of glucose and fructose, which is slightly sweeter, and which is faster to undergo browning reactions and discolor if the grains dry out slightly at the end of cooking. And the mouth-filling umami sensation, caused by natural monosodium glutamate and ribonucleotides, declines with time. So for real rice connoissseurs, people who eat it every day and notice the nuances of its flavor and texture, it makes sense to buy rice labelled "new harvest" and use it quickly.


Cooking water and times From France and Switzerland, a study of the basic cooking properties of different milled rice types. The scientists looked at how much water the rices absorbed, how long they took to cook, and what might account for the differences.

They found that the kernel size and shape are what determine cooking times: not surprisingly, the thicker the longer. (There are three dimensions to a rice kernel: the length; the height, from back to belly; and the thickness through the sides). They found that both short- and long-grain rices absorbed about the same amount of water to give an al dente texture, with 95% of the grain starch soft and gelated; the workable ratio was 2.55 parts water to 1 of rice by weight, giving a grain that's about 75% water, 25% solids (dry rice is about 10% water). Short-grain rices were somewhat better at a ratio of 2.0, and long-grain at 3.0. The usual cooking instructions on packages and in books call for more water, probably to compensate for losses to steam that escapes around the edges of the lid.

The cooking experiments were done in Volvic mineral water with 0.35% salt, about a tenth the concentration of seawater. The rice was added to the boiling water and cooked just until all the rice starch had gelated. The cooking times ranged from 9.5 to 15.4 minutes. Smaller grains generally took less time to cook. But there were deviations from this rule, and they probably have to do with the effects of aging on rice, which slow the penetration of water into the grain and then into the starch granules. The scientists also looked at the microstructure of the grains, and suspect that the rice cell walls and their carbohydrates are arrayed differently in different varieties and may influence water penetration during cooking.

The takehome lesson from this paper is that long- and short-grained rices take about the same amount of water to develop a fully cooked texture, but cooking times vary by 50% or more, and there's no way to predict that. Longer cooking times may require more water to replenish the steam losses during prolonged cooking.


Parboiled rice: color and flavor From Belgium, a study of the qualities of parboiled rice, which is soaked, steamed, and dried before the bran is removed. (Normally the brain is milled away first, and the rice packaged raw.) Parboiling allows some of the bran nutrients to penetrate into the grain; and it results in a firmer rice that doesn't get as soft or leak sticky starch as much as standard rice, so the cooked grains are more tolerant to overcooking and remain separate and loose. They have their own distinctive flavor, with overtones of vanilla and nuttiness that come from the cooking and drying processes. Parboiling goes back thousands of years in India and is also used to manufacture packaged rices.

The Belgian scientists looked at the the typical yellowish color and the flavor of parboiled rice. They found that despite the high water content and moderate temperature, the rice bran underwent browning reactions. The soaking step encouraged rice enzymes to release reactive reducing sugars, and the steam heat encourages them to combine with amino acids from the proteins, generating brown pigments and toasty flavors. Both the native bran pigments and the browning-reaction products diffused into the rice gain during steaming and drying, giving it both it yellowish color and added flavor.

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Tran, T.U. et al. Detection in changes in taste of japonica and indica brown and milled rice during storage . . . . J Agric. Food Chem. 2005, 53, 1108-18.

Vidal, V. et al. Cooking behavior of rice in relation to kernel physicochemical and structural properties. J Agric. Food Chem. 2006, 54, 336-46.

Lamberts, L. et al., Impact of browning reactions and brand pigments on color of parboiled rice. J Agric. Food Chem. 2006, 54, 9924-29.

Curious Cook in the New York Times: Colorful garlic

In today's debut of my occasional column in the New York Times Wednesday food section, I write about the strange, blue-green colors that can develop when garlic and onions are handled in certain ways. The information in the column comes from several recent papers on the subject from labs in Japan and China. For readers who would like to follow up, here are a few (slightly confusing!) chemical details, and the references.

The reactions involve two special sulfur-containing chemicals from the garlic and onions, ordinary amino acids from both, and one enzyme from the garlic.

Step 1: the garlic enzyme alliinase converts the special garlic compound alliin (an allyl cysteine sulfoxide) to a pungent garlic flavor compound, allicin.

Step 2: the garlic enzyme alliinase also converts the special onion chemical (a propenyl cysteine sulfoxide) to two substances: the "lachrymatory factor" that irritates our eyes and has nothing to do with color development, and a colorless "color developer" (a propene thiosulfinate).

Step 3: this color developer reacts with an amino acid to produce a colorless "color precursor."

Step 4: the color precursor reacts with allicin to make the pigment molecules, the pyrroles, which range from reddish to green.

Because enzymes are inactivated at temperatures above 140 degrees F or so, moderate heat moderately speeds all these reaction steps, while high heat stops the first two steps and greatly accelerates the last two.

When freshly harvested garlic is stored at cool temperatures, it slowly accumulates alliin, the precursor to pungent allicin. Stored garlic thus gets progressively more pungent and more prone to developing color.



Bai, B. et al. Increase in the permeability of tonoplast of garlic by monocarboxylic acids. J. Agric. Food Chem. 2006: 54, 8103-07.

Ichikawa, M. et al. Changes inorganosulfur compounds in garlic cloves during storage. J. Agric. Food Chem. 2006: 54, 4849-54.

Imai, S. et al. Identification of Two Novel Pigment Precursors and a Reddish-Purple Pigment Involved in the Blue-Green Discoloration of Onion and Garlic.
J. Agric. Food Chem. 2006, 54, 843-847.

Imai, S. et al. Model Studies on Precursor System Generating Blue Pigment in Onion and Garlic. J. Agric. Food Chem. 2006: 54, 848-852.