Post #9 From Dr. Delwen Samuel, London.
Date: 06/08/2000
Subject: The effects of heating on starch (A reply to Post #6).
This message is in response to Kristen's query about the effects of heating on starch granules. My information is based on cereal starches; I don't know what the effects of heating on starch from other sources would be, but they may be much the same. It would be an interesting area for experimentation, since most of the literature to date concentrates on cereal starches.
The effects of heating depend on the matrix in which the starch granules were contained. If starch granules are heated dry, they can maintain their morphology more-or-less unchanged, even at surprisingly high temperatures, until they are eventually pyrolysed (chemically decomposed). At the higher temperatures, birefringence is lost and the surfaces of the granules can be come rough and uneven. The term "dry" depends on which source you read: moisture figures at which cereal starch is said to remain unchanged range from 13% to 45% (Hansen and Jones, 1977; Ghiasi et al. 1982: 258; Wootton and Chaudry 1980: 1784 - see below for references). This may well vary depending on the starch source.
If starch is heated in water it gelatinises ("melts") and loses its morphology - but the extent to which this happens depends on the moisture content. In limited water systems the starch distorts but the granules do not lose their individual boundaries. In higher water content systems the starch granules disrupt (see Rockland et al 1977). To add to the complications the extent of gelatinisation depends on other ingredients in the mixture: sugars for example affect the degree of gelatinisation. However, well-cooked starch can still be detected using a simple staining technique: the use of Lugol's solution (see Ethnobotanical Leaftlets Starch Research Page web site, page 2, "Coloration".) Gelatinised starch takes up the stain but may be paler than the native starch. Ancient emmer wheat and barley starch, both native and gelatinised, maintains this reaction with iodine and takes on a pale purple coloration: paler than modern gelatinised starch but distinct. I have successfully stained starch in this way, from ancient Egyptian bread and beer remains dating to over 3,000 years old, and so have other workers. This ancient material was preserved in dry conditions. I have no idea whether gelatinised starch is as stable as native starch in moist conditions such as eastern North America.
Kirsten, if you are successful in detecting starch, whether native granules or gelatinised, in your scrapings, I would be interested to know.
Following are some relevant references. Hansen and Jones (1977) and Rockland et al (1977) are particularly useful with good scanning electron micrographs, and see also Greenwood (1967).
Blanshard, J. M. V., 1979 "Physicochemical aspects of starch gelatinization", in J. M. V. Blanshard and J. R. Mitchell (ed.), Polysaccharides in foods, London, Butterworths, p. 139-52.
Cunin, C., Handschin, S., Walther, P. and Escher, F., 1995 "Structural changes of starch during cooking of durum wheat pasta", Food Science and Technology, 28/3, p. 323-8.
Derby, R. I., Miller, B. S., Miller, B. F. and Trimbo, H. B., 1975 "Visual observation of wheat-starch gelatinization in limited water systems", Cereal Chemistry, 52/5, p. 702-13.
Ghiasi, K., Hoseney, R. C. and Varriano-Marston, E., 1982 "Gelatinization of wheat starch. III. Comparison by differential scanning calorimetry and light microscopy", Cereal Chemistry, 59/4, p. 258-62.
Greenwood, C. T., 1967 "The thermal degradation of starch", in M. Wolfrom and R. S. Tipson (ed.), Advances in carbohydrate chemistry, 22, New York, Academic Press, p. 483-515.
Hansen, L. P. and Jones, F. T., 1977 "A microscopic view of thermal-processed wheat flour", Journal of Food Science, 42/5, p. 1236-42.
Hoseney, R. C., Atwell, W. A. and Lineback, D. R., 1977 "Scanning electron microscopy of starch isolated from baked products", Cereal Foods World, 22/2, p. 56-60.
Kawabata, A., Takase, N., Miyoshi, E., Sawayama, S., Kimura, T. and Kudo, K., 1994 "Microscopic observation and X-ray diffractometry of heat/moisture-treated starch granules", Starch, 46/12, p. 463-9.
Lineback, D. R. and Wongsrickasem, E., 1980 "Gelatinisation of starch in baked products", Journal of Food Science, 45/1, p. 71-4.
Liu, J.-M. and Zhao, S.-L., 1990 "Scanning electron microscope study on gelatinization of starch granules in excess water", Starch, 42/3, p. 96-8.
Rani, M. R. S. and Bhattacharya, K. R., 1995 "Microscopy of rice starch granules during cooking", Starch, 47/9, p. 334-7.
Rockland, L. B., Jones, F. T. and Hahn, D. M., 1977 "Light and scanning electron microscope studies on dry beans: extracellular gelatinisation of lima bean starch in water and a mixed salt solution", Journal of Food Science, 42/5, p. 1204-7, 12.
Samuel, D., 1996 "Investigation of ancient Egyptian baking and brewing methods by correlative microscopy", Science, 273, p. 488-90.
Wootton, M. and Chaudhry, M. A., 1980 "Gelatinization and in vitro digestibility of starch in baked products", Journal of Food Science, 45/6, p. 1783-4.
*****
Delwen Samuel
Institute of Archaeology
University College London
31-34 Gordon Square
London, WC1H 0PY
UK
d.samuel@ucl.ac.uk
Post #8 From Pkam.
Date: 02/24/2000
Subject: Taro.
Do you know anything about taro starch?
I'm very interested.
Pkam1998@aol.com
Post #7 From Claus Skriver, Denmark.
Date: 02/19/2000
Subject: Some questions.
I am a Danish archeologist working with microwear analysis. After I heard about starch analysis, I became interested in the subject and would like to incorporate it in my anlysis of sickels from the danish neolitic and bronze age. Therefore, I would like to hear, do you think it would be possible to distinquish eksampel starch from wheat starch and from barley?
Another thing; Where and how do I start? Can you suggest some litterature that would be useful for a beginning?
Thanks for your help.
Claus Skriver
Denmark
claus.skriver@get2net.dk
Post #6 From Kristen J. Gremillion, Columbus, OH
Date: 02/02/2000
Subject:Starch grains in pots?.
Is it possible that starch grains might make their way from pot contents into pores in the paste and become lodged there? would they inevitably be destroyed or rendered unidentifiable by heating over 50 deg. C? I have found some grains by scraping out some material from a sherd interior, but not under very controlled conditions, so it could be contamination (I did take some precautions, but the pottery has been handled and exposed to the air). I'm trying to decide whether to try again under more controlled conditions and it would help to know whether it's worth pursuing.
I'm new to this area of research & hope to develop a comparative collection of starch grains from economic plants of eastern North America; I will also be looking at ground stone tools. Any thoughts on how to sample a bedrock mortar without actually removing a piece of it? In eastern Kentucky we find depressions in sandstone bedrock or roof fall within rockshelters that contain remains of early cultivated plants. An early report mentions wooden pestles that "fit into" one of these "hominy holes" (a misnomer--they predate maize), though unfortunately I could not locate these artifacts.
Any thoughts or advice on these topics would be greatly appreciated. I was
glad to find this site.
Kristen J. Gremillion
244 Lord Hall
Department of Anthropology
124 West 17th Avenue
The Ohio State University
Columbus, OH 43210
phone: 614.292.9769
FAX: 614.292.4155
gremillion.1@osu.edu
Post #5 From Jacques E. Brochier, Marseille cedex 3
France.
Date: 1/28/99
Subject: Archaeological Soil Samples.
There are a lot of papers dealing with extraction procedures of starch grains in tartar.
Is there any study with detailed (and standard ?) extraction procedure applied to sediment samples ?
A chapter on this topic in your great web page would be appreciated.
Jacques E. Brochier
Chargé de recherche au CNRS
Laboratoire de paléontologie humaine et de préhistoire
Faculté des Sciences, Bât. 10, Centre St Charles
Place Victor Hugo
13331 Marseille cedex 3
France
tel. +(33) 04 91 10 61 93
fax. +(33) 04 91 10 61 94
e-mail brochier@newsup.univ-mrs.fr
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Post #4 From Linda Perry, Carbondale, Illinois, USA.
Date: 12/08/98
Subject: Starch samples needed.
Greetings: I am currently analyzing archaeological samples from the Orinoco valley in Venezuela. I am looking for comparative specimens of Maranta arundinacea (other than grocery store arrowroot) and Calathea alouatta. Any assistance would be appreciated, Linda Perry.
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Post #3 From Peter Matthews, Osaka, Japan.
Date: 12/01/98
Subject: Starch granules do change as they mature.
Dear Jeff,
Yes starch granules do change, in various ways - with time, with
position in the plant, and with soil temperature, and they also behave
differently in different plant species. There are two good articles on
this in Japanese with English abstracts and figure titles:
Y. Sugimoto, K. Nishihara, K. Abe, S. Fujita, and H. Fuwa (1987) Developmental changes in starch properties of the taro (Colocasia esculenta (L.) Schott) Journal of the Japanese Soceity of Starch Science 34, 1-10.
With taro, size and shape remained similar at various stages of development, and in different categories of storage organ.
Y. Sugimoto, M. Yamamoto, K. Abe, and H. Fuwa (1987) Developmental changes in starch properties of the Chinese yam (Dioscorea batatas Decne) Journal of the Japanese Society of Starch Science 34, 11-20.
With this yam, granule size increased in the early stage of tuber development, and was greater in the central portion of the tuber.
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Post #2 From Jeff Parr, Casino, Australia.
Date: 11/30/98
Subject: Do starch grains mature differentially?
I have just looked at your web page..."Its great" just what starch researchers needed...some place where we can all interact and pool resources.
I have the following question:
Does anyone know whether starch grains change in their morphological attributes as they mature? I am interested in this as some of my starch samples seem to have very small grains which overlap in size and morphology with other species. However, the larger grains of these species appear to take a different form and do not overlap.
Jeff Parr
PO Box 555
Casino NSW, 2470 Australia
Phone 02 6662 7924
Email jparr@metz.une.edu.au
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Post #1
Date: 11/06/98
Subject: Welcome to the Starch Forum
Do you have news of interest to starch workers, or questions on methods of identifying ancient starch? We would love to hear from you!
Let us know what kinds of projects you are working on, and how our readers might be of help to you.
Please also use this open forum to let us know what kinds of articles, materials or resources you would like to see posted on the Starch Research Page.
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