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Food Science

Food Structure

Gels

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Full-Text Articles in Life Sciences

Microstructure And Rheological Properties Of Composites Of Potato Starch Granules And Amylose: A Comparison Of Observed And Predicted Structures, K. Svegmark, A.-M. Hermansson Jan 1993

Microstructure And Rheological Properties Of Composites Of Potato Starch Granules And Amylose: A Comparison Of Observed And Predicted Structures, K. Svegmark, A.-M. Hermansson

Food Structure

Potato starch granules were gelatinised in amylose solution to study the effect of adding amylose to a highswelling granular starch system. The effects of varying the amount of potato starch from 1-10% , added to a solution of 2% amylose, were studied by means of dynamic viscoelastic measurements and light microscopy.

The granules gelatinised in amylose solution had a lower degree of swelling than those gelatinised in water. The restricted swelling in amylose was reflected in a decrease in the complex shear modulus (G*) at 75'C. GeJatinisation in 2% amylopectin also caused a decrease in G*, but gelatinisation in 2 ...


Heat-Induced Structural Changes In Acid-Modified Barley Starch Dispersions, K. Autio, K. Poutanen, T. Suortti, E. Pessa Jan 1992

Heat-Induced Structural Changes In Acid-Modified Barley Starch Dispersions, K. Autio, K. Poutanen, T. Suortti, E. Pessa

Food Structure

The effect of heat treatment on the gel formation and microstructure of barley starch dispersions , hydrolyzed with I M HCI for 0.5, 1.0 and 4.0 hours , was studied by dynamic viscoelastic methods and by light microscopy . The effects of acid hydrolysis on the molecular weight of amylopectin and amylose were studied by high -performance liquid chromatography (HPLC) with post-column iodine staining.

Microstructural studies of 8% hydrolyzed barley starch dispersions heated to 90 0 C showed that even a short acid treatment induced considerable changes in the granule structure. The molecular weight of amylopectin decreased substantially. As the ...


Distribution Of Amylose And Amylopectin In Potato Starch Pastes: Effects Of Heating And Shearing, K. Svegmark, A. M. Hermansson Jan 1991

Distribution Of Amylose And Amylopectin In Potato Starch Pastes: Effects Of Heating And Shearing, K. Svegmark, A. M. Hermansson

Food Structure

The microstructure of potato starch pastes and gels in the concentration range 5-10% (w/w) was studied as a function of shear and heat treatment usi.ng light microscopy. Heating induced extensive swelling of potato starch granules, and the swollen granules filled the whole volume of the starch pastes that were subjected to a minimum of shear. The volume of the aqueous phase outside and in the center of the swollen granules is practically negligible compared to the volume occupied by the walls of the swollen granules. The granules with the lowest gelatinization temperatures swelled quickly without restrictions, so that ...


Rheological And Microstructural Changes Of Oat And Barley Starches During Heating And Cooling, K. Autio Oct 1990

Rheological And Microstructural Changes Of Oat And Barley Starches During Heating And Cooling, K. Autio

Food Structure

Microstructural and rheological changes in barley and oat starch dispersions during heating and cooling were studied by light microscopy and dynamic viscoelastic measurements. The two starch pastes showed similar viscoelastic properties after gelatinization, but during cooling the 20% barley starch pastes heated at 95°C underwent a sharp transition in viscoelastic behaviour probably due to the gelation of amylose. This transition was shifted to lower temperatures at 10% starch concentration.

Microstructural studies of an 8% barley starch dispersion heated to 90°C using the smear technique showed amylose to form a network structure around the granules. The granules in starch ...


Microstructural Changes In Wheat Starch Dispersions During Heating And Cooling, M. Langton, A. M. Hermansson Jan 1989

Microstructural Changes In Wheat Starch Dispersions During Heating And Cooling, M. Langton, A. M. Hermansson

Food Structure

Microstructural changes in 8-11% wheat starch dispersions during heating, cooling and cold storage have been evaluated by light microscopy and scanning electron microscopy.

Heat treatment of wheat starch dispersions gives rise to two stages of swelling and solubilization. During the first phase of swelling, solubilized amylose was observed ln the centre of the granules and, to some extent, outside the granules. Further swelling deformed the granules and more amylose was released. When the temperature treatment took place under shear, the outer layer of the swo llen granules fra ctured at 94°C and above, and amylopectin fragments were dispersed into ...


Changes In The Ultrastructure Of Emulsions As A Result Of Electron Microscopy Preparation Procedures, M. Liboff, H. D. Goff, Z. Haque, W. K. Jordan, J. E. Kinsella Jan 1988

Changes In The Ultrastructure Of Emulsions As A Result Of Electron Microscopy Preparation Procedures, M. Liboff, H. D. Goff, Z. Haque, W. K. Jordan, J. E. Kinsella

Food Structure

Various methods of preparing emulsions for electron microscopy were examined with peanut oil/protein and ice cream mix emulsions. For transmission electron microscopy {TEM) , fresh peanut oil/bovine serum albumin emulsions were mixed with 2% agar , fixed in phosphate-buffered (pH 7 . 0) 4% glutaraldehyde solution and postfixed in phosphate-buffered (pH ? . 0) 1% osmium tetroxide alternatively , the glutaraldehyde- fixed samples were briefly rinsed in acetone prior to postfixation . Both preparations yielded satisfactory fat globule preservation. Similar emulsions were prepared on loops and suspended over vapors of 25% gJ nt.RrBl r'lehyr'le Rnc'l 1% oRmi urn tetroxide . This preparation ...


Aspects Of Sample Preparation For Freeze-Fracture/Freeze-Etch Studies Of Proteins And Lipids In Food Systems. A Review, Wolfgang Buchheim Jan 1982

Aspects Of Sample Preparation For Freeze-Fracture/Freeze-Etch Studies Of Proteins And Lipids In Food Systems. A Review, Wolfgang Buchheim

Food Structure

To select optimum specimen preparation methods and to correctly interpret freeze-fracture/freezeetch micrographs of food systems a detailed knowledge of the individual steps of preparation -- i.e. chemical fixation of samples, their cryoprotective pretreatment, cryofixation, freeze-fracturing and -etching, and replication -- and of their influence on the appearance of different constituents, especially proteins and lipids, is necessary. Food systems show great variation in composition, structure and especially in their content of water -- e.g. molecular and colloidal solutions, oil-in-water and water-in-oil emulsions, gels suspensions, semi-solid systems such as cheese, dried systems such as milk powders -- thus requiring a careful variation of ...