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Spectroscopy Can Help Bakers Make Bread

Photonics Spectra
Mar 2008
Researchers characterize compounds in rising bread and determine the optimum rise time.

David L. Shenkenberg

When bread dough rises in a small amount of time, the yeast does not produce much carbon dioxide gas, resulting in bread that is too flat and too hard. Longer rise times, however, result in bread that is too fluffy. Bakers currently rely on personal experience to produce bread in the optimum amount of time. As such, they would benefit from using a more precise and more objective method for determining the optimum rise time, especially because overly long baking times unnecessarily increase costs.


Researchers used a near-IR spectrometer and this FTIR spectrometer (pictured) to study bread as it rises. The lower figure is a close-up of the bread.

Spectroscopy can profile rising bread, providing the baker with the information necessary to make an excellent loaf, according to researchers from the University of Milan, Italy, and from Teagasc, Ashtown Food Research Centre, in Dublin, Ireland. They have investigated rising bread with both near-infrared and attenuated total reflectance Fourier transform infrared (FTIR) spectroscopy. University professor Ernestina Casiraghi said that they used both techniques because each gives unique information about changes in the relative abundance of compounds in bread as it rises.

The investigators used a Foss NIRSystems spectrometer for near-infrared spectroscopy and a Bio-Rad spectrometer for FTIR spectroscopy. To establish the attenuated total reflectance condition, they used a germanium crystal at 45° with 11 internal reflection points. They analyzed all of the spectroscopy data with The Unscrambler software from Camo of Trondheim, Norway, and used baker’s, retail and gluten-free flour to make the bread dough.

No matter which type of flour the researchers used, the near-infrared spectra clearly exhibited a singular peak at 982 nm. They performed principal component analyses on the second derivative of the spectra and found that they could monitor changes in water and starch structure with near-infrared spectroscopy, whereas they could observe changes in protein conformation with FTIR spectroscopy.

The scientists described spectral changes during bread rising with a sigmoid function, in which the maximum of the first derivative yields the maximum velocity of bread rising while the maximum of the second derivative yields the acceleration of the process. The minimum of the second derivative corresponds to the optimum rise time, in which the dough is neither too hard nor too soft. “What we found is that it is possible to follow bread rising when it is at its maximum,” Casiraghi said.

The optimal time for bread dough to rise corresponds to the minimum of the graph of the second derivative of the spectrum, which is shown here for dough made from baker’s flour. Reprinted with permission of the Journal of Agricultural and Food Chemistry.

All three types of flour yielded similar data in the case of near-infrared spectroscopy, but the FTIR spectrum of gluten-free flour differed from that of the other flours. However, she cautioned, “we are more sure about NIR spectroscopy because, compared with IR, we have a deeper penetration into the dough.”

She said that it is now possible to use spectroscopy to align the exact time in which the rising gets faster with the exact time in which the rising process ends.

Journal of Agricultural and Food Chemistry, Feb. 13,2008.

Basic Sciencecarbon dioxide gasnear-infraredResearch & TechnologyspectroscopyTech Pulse

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