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Food Science

Food Structure

Rheology

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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 ...


Microstructural Studies In Fat Research, I. Heertje Jan 1993

Microstructural Studies In Fat Research, I. Heertje

Food Structure

Microstructural studies play an important role in establishing the relation between composition, processing and final properties of many food products. In order to arrive at a full description of microstructure many visualization- and preparation techniques are needed. A number of fatty products such as shortenings, margarine , butter, and low fat spreads are discussed from a microstructural point of view. Examples of the influence of process parameters on microstructure and rheological properties are given. In particular, attention is paid to the fat crystalline matrix and the emulsion structure.

Further, a new methodology is described making it possible to study interactions of ...


Microstructure And Texture Of Khoa, G. R. Patil, A. A. Patel, Paula Allan-Wojtas, Miloslav Kalab Jan 1992

Microstructure And Texture Of Khoa, G. R. Patil, A. A. Patel, Paula Allan-Wojtas, Miloslav Kalab

Food Structure

Khoa, a partially dehydrated milk product indigenous to India, was prepared from buffalo milk by boiling it vigorously in an open pan and reducing its volume to approximately 25% within 30 min. The hot semi-solid product (Khoa pat) was held at 20•c for 3 h (fresh, cooled Khoa) or 48 h (swred Khoa); the products were either worked with a pestle in a mortar for 5 min or were left without working.

Structural features of Khoa were studied by light microscopy and electron microscopy. Freshly prepared coo led Khoa had a granular structure consisting of protein granules several hundred ...


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 ...


Structure And Rheology Of Dairy Products: A Compilation Of References With Subject And Author Indexes, David N. Holcomb Jan 1991

Structure And Rheology Of Dairy Products: A Compilation Of References With Subject And Author Indexes, David N. Holcomb

Food Structure

No abstract provided.


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 ...


Changes In The Rheology And Microstructure Of Ropy Yogurt During Shearing, J. A. Teggatz, H. A. Morris Jan 1990

Changes In The Rheology And Microstructure Of Ropy Yogurt During Shearing, J. A. Teggatz, H. A. Morris

Food Structure

Rheological and microstructural changes that occurred in ropy yogurt during shearing were observed. Yogurt made with an exopolymer-producing (ropy) strain of Lactobacillus delbrueckii subsp. bulgaricus and non-ropy strain of Streptococcus thermophilus was subjected to an increasing shear rate from 0-833 s-1 using a Haake Rotovisco RV2. Shear stress niticeably increased to a peak value and then decreased to a plateau value as the shear rate continued to increase. Samples taken at eight different shear rates were examined by scanning electron microscopy (SEM). At low shear rates, the exopolysaccharide (EPS) existed as a filamentous network attached to the lactobacilli and casein ...


Textural Properties And Structure Of Starch-Reinforced Surimi Gels As Affected By Heat-Setting, J. M. Kim, C. M. Lee, L. A. Hufnagel Jan 1987

Textural Properties And Structure Of Starch-Reinforced Surimi Gels As Affected By Heat-Setting, J. M. Kim, C. M. Lee, L. A. Hufnagel

Food Structure

The gel forming behavior of red hake (Urophycis chuss) surimi with and without starch and its relationship to the structure of the gel matrix were studied. For surimi gels without starch, a combination of preheat- setting at 40 C and cooking at 90 C resulted in significantly greater gel strength than cooking alone. However, preheat - setting of gels containing wheat or potato starch had no significant effect on gel strength demonstrating an opposite trend in gel strength due to the differences in swelling power, water holding ability and gelatinization temperature between potato and wheat starches. This difference in gel forming ...


Observations On The Microstructure And Rheology Of Ovalbumin Gels, I. Heertje, F. S.M. Kleef Jan 1986

Observations On The Microstructure And Rheology Of Ovalbumin Gels, I. Heertje, F. S.M. Kleef

Food Structure

Understanding the gelation behaviour of proteins is of importance in order to be able to influence the properties of many food systems and it may lead to proposals for product or process improvement . In this context the formation of heat-set ovdl bumin gels. in different media , has been studied by microstrucmral. rheological and conformational observations. An oval bumin/ water geL prepared at pH 5, shows a granular. inhomogeneous microstructure. At this pH the re are both many interand intramolecu lar interactions. and network formation occurs via aggregates of folded, globular protein chains. On the other hand , gels prepared at pH ...


Rheological And Scanning Electron Microscopic Examination Of Skim Milk Gels Obtained By Fermenting With Ropy And Non-Ropy Strains Of Lactic Acid Bacteria, S. M. Schellhaass, H. A. Morris Jan 1985

Rheological And Scanning Electron Microscopic Examination Of Skim Milk Gels Obtained By Fermenting With Ropy And Non-Ropy Strains Of Lactic Acid Bacteria, S. M. Schellhaass, H. A. Morris

Food Structure

Physical and rheological parameters of skim milk gels fermented with slime producing (ropy) cultures and non-ropy cultures were compared. The skim milk gels were made from steamed reconstituted nonfat dry milk inoculated with 2% of a single strain starter culture and incubated at 32, 37, and 45°C until pH 4. 5 + 0.05 was attained.

Skim milk gels fermented by slime-producing strains of Streptococcus thermophilus, Streptococcus cremoris, and Lactobacillus bulgaricus exhibited similar rheological and physical characteristics. Electron micrographs of the ropy skim milk cultures showed that slime produced by the organisms was associated with the cell surface as well ...