Life Sciences Commons^™

Stranded Structure Development In Thermally Produced Protein Concentrate Gel, T. Beveridge, L. Jones, M. A. Tung

Food Structure

Scanning electron micrographs of thermally induced whey protein concentrate gels were taken. Sample preparation was accomplished by glutaraldehyde fixation, osmium tetroxide post fixation and critical point dehydration. Stranded or beaded gel structures were observed on the external surface of a gas bubble, suggesting that a "string-of-beads" gel microstructure may result from bubble formation during thermal treatment.

The Effects Of Commercial Processing On The Structure And Microchemical Organization Of Rapeseed, S. H. Yiu, I. Altosaar, R. G. Fulcher

Food Structure

Rapeseed samples collected from different processing stages were obtained from one commercial crushing plant for the present investigation. The samples included (A) whole seeds, (B) flaked seeds, (C) press cakes, (D) solvent extracted meal, (E) desolventized meal and (F) cooled, desolventized meal . Frozen and/or glycol met hacrylate-embedded sections of the samples were examined using the techniques of fluorescence microscopy. Mechanical crushing tended to disrupt cell walls. After cooking and expeller pressing, individual protein bodies fused to form large masses encompassing phytin containing globoids. Storage lipids also coalesced into larger droplets. Most of the oil was removed after solvent extraction …

Microstructure Of Winged Beans, K. Saio, Y. Nakano, S. Uemoto

Food Structure

Microstructures of seven plant introductions of winged beans (Psophocarpus tetragonolobus) produced in Okinawa, Japan were investigated. In cotyledonary cells of winged beans, protein bodies plus numerous lipid bodies were distributed in a cytoplasmic network. Starch granules were often found in some introductions but rarely in others. All seven introductions had very thick cell walls. The high protein, fat and hemicellulose contents of winged beans are consistent with the numerous protein bodies, lipid bodies and thick cell walls in the mature cotyledonary cells. The cell walls contained a number of depressions or cavities 1 to 2 lJ m deep which frequently …

B-Glucans In The Caryopsis Of Sorghum Bicolor (L.) Moench, C. F. Earp, C. A. Doherty, R. G. Fulcher, L. W. Rooney

Food Structure

Fluorescence microscopy was used to determine the location of B- glucans in sorghum. Sections from three genetically different sorghum cultivars were stained with Calcofluor or Congo Red , fluorochromes which have been reported to react with 13-glucans. Autofluorescence, indicative of ferulic acid in other cereals, was observed in untreated sections. When stained sections were treated with endo -B-glucanase , fluorescence was reduced or entirely eliminated in pericarp, aleurone and endosperm cell walls. 13-Glucans were i so lated from the endosperm of three sorghum cultivars. When reacted with the two dyes, Calcofluoror Congo Red , precipitates formed immediately, a reaction which …

Field Spectroscopy In The Food Production Chain, E. J. Brach

Food Structure

This paper reviews the application of field spectroscopy in the food production chain, particularly how field spectroscopy aids research and production of agricultural crops , and helps to understand the process of converting these crops into food.

The review discusses the nondestructive application of field spectroscopy such as ultraviolet, reflective , visible, near infrared and fluorescence techniques using conventional or laser light sources, to determine qualitative and quantitative properties of agricultural crops and produce.

Field spectroscopy can provide data on soil constituents and moisture, crop maturity, crop vigor, crop health, variety, variety within crops , and protein and moisture content …

Endosperm Degradation In Barley Kernels That Synthesize Amylase In The Absence Of Embryos And Exogenous Gibberellic Acid, A. W. Macgregor, P. B. Nicholls, L. Dushnicky

Food Structure

During germination at l6°C, whole seeds and distal half-seeds of Klages barley and two types of Clipper barley (Types A and B) were analyzed for a -amylase . Structural changes in the endosperms of these seeds and half-seeds were examined by scanning electron microscopy. In Clipper B half-seeds, Q-amy base activity increased significantly , there was a detectable amount of starch granule hydrolysis and endosperm structure was markedly degraded. No starch hydrolysis and only trace amounts of a-amylase and endosperm degradation were detected i.n Clipper A and Klages halfseeds. The rewns significant a -amylase synthesis, starch hydrolysis and endosperm degradation …

Composition And Microstructure Of Soft Brine Cheese Made From Instant Whole Milk Powder, Mohamed M. Omar, Wolfgang Buchheim

Food Structure

Comparative studies were made on the composition, microstructure and organoleptic quality of soft brine cheese made from instant whole miIk powder and from raw miIk. The chemical analysis of young and ripened (one and two month) cheese revealed similarity except for a higher salt content in the cheese made from reconstituted milk at the end of ripening . Electron microscopic studies showed distinct differences in the structure of the protein matrices in the ripened cheese samples , i .e . a very homogeneous structure in the cheese made from raw milk compared with a slightly aggregated state of the protein …

Development Of Microstructure In Set-Style Nonfat Yogurt - A Review, Miloslav Kalab, Paula Allan-Wojtas, Beverley E. Phipps-Todd

Food Structure

The development of microstructure in natural set-style nonfat yoghurt was stud i ed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition to thin-sectioning and conventional SEM described in the literature, this review illustrates gelation of milk with micrographs obtai ned by rotary shadowing of casein micelles and their clusters. The existence of void spaces occupied by lactic acid bacteria in yoghurt was con finned by cold-stage SEM of uncoa ted specimens. The microstructure of yoghurt is affected by the preheat treatment of milk, bacterial starter cultures, total solids content , and the presence of thickening agents. …

Evaluation Of Selected Properties Of Chlorinated Wheat Flours In A Lean Cake Formulation, J. Grider, E. A. Davis, J. Gordon

Food Structure

Cake flours treated with different levels of chlorine were evaluated by use in a Kissell cake formulation. Flour particle size distributions varied with chlorination level, but pH and specific gravity of the batters did not differ. Batter viscosity differences were observed at specific temperatures during heating of total batters. Temperature profiles differed positionally in the cakes, but these patterns of heat penetration were not related to level of chlorine treatment. However, water loss rates differed depending on the level of chlorine treatment indicating a more pronounced effect of chlorination level on the water loss characteristics of the cakes during the …

Some Effects Of Lipids On The Structure Of Foods, K. Larsson

Food Structure

The functional properties of different lipids in foods are demonstrated and related to the structure of lipid or lipid-water phases. On the basis of new X-ray data on the crystal structure of the B'-form and the a + B' transition in fats, the polymorphic transitions are considered as different lateral arrangements of triglyceride dimers. The physical properties of fat crystals can be explained from the structures, as well as possibilities to influence the polymorphic transitions.

Molecular interaction between polar lipids and proteins or starch is discussed, and the effect of the amylose-lipid inclusion complex on gelatinization temperature and water penetration …

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 …

Microscopy In The Study Of Fats And Emulsions, J. M. Deman

Food Structure

Plastic fats consist of a three dimensional network structure of crystals in which liquid oil is trapped. This crystal network is held together by weak attractive forces, the nature of which is nut definitely e stablished. Crystal size is dependent on temperature history and is subject to polymorphic transitions which greatly affect the microstructure of the system. The microstructure of fats has been investigated by using polarized light microscopy, electron microscopy and X-ray diffraction analysis . Recently, a permeametric method has been developed which enables the determination of the specific surface area of the crystals in a fat. This method …

Structure And Properties Of The Particulate Constituents Of Human Milk. A Review., M. Ruegg, B. Blanc

Food Structure

Milk contains different types of colloidal or coarsely dispersed particles, such as casein micelles, membrane fragments, fat globules and cells. The fat globules are composed of subpopulations of differently sized particles. In contrast to COW 1S milk, the overall average diameter (dys), increases with advancing lactation from about 1.8 ~min colostrum to 4.0 ~min mature milk. Membrane materials originating from the milk fat globule membrane, plasma membrane, secretory vesicles and other sources can be found in milk serum. These particles have also been called lipoprotein particles. Their size ranges from about 10 - 400 nm. New results concerning the structure …

Freeze-Induced Fibre Formation In Protein Extracts From Residues Of Mechanically Separated Poultry, R. A. Lawrence, P. Jelen

Food Structure

Coagulated protein obtained by alkali extraction and acid precipitation from the bone containing residues discarded after mechanical separation of chicken was textured by freezing in semi-infinite cylinders followed by heat-setting in a microwave oven. Macrophotography was used to illustrate textural differences resulting from pH variations (4.5-6.0) in the precipitated protein, and changes in the ambient temperature used for freezing (-5°C to -32°C). Well identified, permanent fibres were fanned by the process under all conditions studied. The thickness of the fibres decreased and their radial orientation increased with increasing pH and decreasing ambient temperature of freezing. Cross-linkages between parallel fibres of …

Correlation Of Microscopic Structure Of Corn Starch Granules With Rheological Properties Of Cooked Pastes, D. D. Christianson, F.L. Baker, A.R. Loffredo, E. B. Bagley

Food Structure

The progressive geometric changes that occur in swelling of corn starch granules during heating throughout the range of gelatinization (63-72°C) and at higher temperatures when substantial amount s of soluble starch are released from the granule were observed by scanning electron microscopy (SEM). Corn starch granules begin to swell radially, then undergo radial contraction and random tangential expansion. They form complex geometrical structures at the midpoint range (67-70°C) unlike the more uniform single-dimensional tangential swelling that occurs with lenticular granules of wheat starch . At higher temperatures, when starch begins to solubilize, corn starch granules lose their distinct ridges and …

Protein Bodies In Dormant, Imbibed And Germinated Sunflower Cotyledons, R. D. Allen, H. J. Arnott

Food Structure

Scanning electron microscopy was used to observe the morphology and structure of protein bodies in dormant and imbibed sunflower cotyledons and to document the morphological changes in protein bodies during germination and seedling growth. In order to clearly visualize dormant seed structure, anhydrous fixation techniques were employed. Definite differences in cellular structure are seen in comparisons of dry and imbibed seed tissues. As germination proceeds, protein bodies lose their smooth spherical shape and become indented and pitted. Protein body coalescence and fusion precedes the formation of a central protein vacuole. As protein is hydrolyzed, protein vacuole density decreases, and its …

Effect Of High Hydrostatic Pressure On Meat Microstructure, E. A. Elgasim, W. H. Kennick

Food Structure

Bovine longissimus muscle was prerigor pressure treated at 103.5 MNm- 2 at 37 °C for 2 min and immediately sampled, fixed and examined by light microscopy, scanning and transmission electron microscopy. Parameters like pH, Warner-Bratzler shear force values and sarcomere length were measured and related to the microscopic observations. Pressure treated samples have shorter sarcomere length, lower pH and W-B values. Physical changes include separation of sarcolemmal and endomysial sheath, contraction bands, disruption of myofibrillar structure and increased interfibrillar and intermyofibrillar spaces. At the subcellular levels, disappearance of glycogen granules, appearance of swollen mitochondria, sarcoplasmic reticulum and in some cases …

Instrumental And Sensory Analysis Of The Action Of Catheptic Enzymes On Flaked And Formed Beef, S. H. Cohen, R. A. Seagars, A. Cardello, J. Smith, F. M. Robbins

Food Structure

Texture profile analysis, Instron punch and die testing, laser diffraction measurements and scanning electron microscopy (SEM) were used to evaluate the effects of catheptic enzymes on flaked and formed beef. Although salt (NaCl) and sodium tripolyphosphate (TPP) have often been used to improve the textural quality of flaked and formed beef, the catheptic enzymes used in this study were shown to be as effective as NaCl/TPP, and in many cases more effective, in improving the textural characteristics of this product. Instron punch and die and scanning electron photomicrographic analysis showed that the enzyme and NaCl/TPP samples were quite similar; however, …

Grain Structure And End-Use Properties, Y. Pomeranz

Food Structure

Practical implications of grain structure relate to every step from grain development and production through market ing to processing, utilization, and consumption . The structure and adherence of the hulls may contribute to protection of grain during germination or malting and protection against insect infestations . Germ retention during threshing and separation during processing depend on the germ structure and location in the kernel. The subaleurone and central endosperm layers differ in cell size, shape, and structure and in composition, especially with regard to protein contents and quality. The main factors in grain hardness are the intrinsic hardness of the …

Scanning Electron Microscopy Of The Pericarp And Testa Of Several Sorghum Varieties, C. F. Earp, L. W. Rooney

Food Structure

Pericarp thickness (determined by Z gene) varies greatly among sorghum varieties ranging· from very thin (8 ~ m) to very thick (160 ~m ) . Pericarp thickness also varies within an individuual kernel. The areas below the style and near the hilum are the thickest with the sides of the kernel being thinnest . Scanning electron microscopy was used to document differences in pericarp thickness and to explain milling differences . Varieties with a thick pericarp had starch granules in the mesocarp cell layers. Sorghums with a thin pericarp did not have starch granules in the mesocarp except near the …

Freeze-Etch Of Emulsified Cake Batters During Baking, J. D. Cloke, J. Gordon, E. A. Davis

Food Structure

Cryofixation, freeze-etch techniques were used to study the structure of cake batters made from a lean cake formulation before heating and after heating to temperatures up to l00-l02°C. Batters were prepared without added emulsifiers and with saturated and unsaturated monoglycerides replacing 5 and l 0% of the oil. Unsaturated monoglyceri des were more effective than saturated monoglycerides in dispersing oil droplets through the batter. Saturated monoglycerides formed liquid crystals during baking. The temperature at which starch granules began to swell was slightly higher for saturated monoglyceride containing cakes. The batter matrix between starch granules was more clearly defined in unsaturated …

Morphological And Textural Comparisons Of Soybean Mozzarella Cheese Analogs Prepared With Different Hydrocolloids, C. S. Yang, M. V. Taranto

Food Structure

The morphology and texture of mozzarella cheese analogs prepared from soy protein isolate, gelatin, fat and different hydrocolloids (gums) were evaluated and compared. The fracturability, hardness and adhesiveness of the cheese analog gels were found to be proportionally related to the amount of fat and gelatin, and concentration and viscosity of gums. However, the stretchability of the cheese analog progels was not controlled by the viscosity of gums, but by the amount of gum and gelatin in the formulation. Fat content affected the fracturability and hardness, but did not have a significant effect on the other textural parameters or stretchability. …

Detection Of Buttermilk Solids In Meat Binders By Electron Microscopy, Miloslav Kalab, Frederick Comer

Food Structure

Nonfat dry milk and buttermilk solids used as ingredients in meat binders can be differentiated by transmission electron microscopy. The meat binders are suspended in water and coarser ingredients such as wheat and mustard flours are separated from the milk solids by low-speed centrifugation (415 g for 30 min). The milk solids thus purified are concentrated by ultracentrifugation (8 x 104 g for 90 min) and the resulting pellets are embedded in a resin, thin-sectioned, stained, and examined by transmission electron microscopy. Buttermilk solids are revealed by the presence of fat globule membrane fragments. In the absence of buttermilk solids …

Ultrastructural Studies Of Milk Digestion In The Suckling Rat, P. B. Berendsen

Food Structure

The structure of milk in the stomach and proximal small intestine of suckling rats at 12 and 24 hours, 5, 10 and 15 days of age was examined by scanning and by transmission electron microscopy. The milk curd in the gastric lumen consisted of chains of casein micelles which entrapped milk fat globules. The appearance was similar to that reported for bovine milk curd and cottage cheese. The gastric milk curd at 12 and 24 hours also contained large masses of granules 4-8 nm in diameter. The relationship of these particles to casein micelles is unknown.

Casein micelles in the …

The Microscopic Structure And Chemistry Of Rapeseed And Its Products, S. H. Yiu, H. Poon, R. G. Fulcher, I. Altosaar

Food Structure

The location and distribution of some of the storage constituents in the structures of rapeseed and its products were investigated. Hand-cut or glycol methacrylate-embedded sections were stained with dyes or fluorochromes of known specificities and examined using fluorescence, bright-field and/or polarizing microscopy. Results obtained from the study were based upon observations of characteristics of the various stainings, birefringence, induced fluorescence and autofluorescence. The effects of enzymatic hydrolysis, solvents and processing on the cellular structures and their affinity for certain dyes/ fluorochromes were also investigated. Major and minor storage constituents were tentatively located in the structure of rapeseed. Lipids and proteins …

Light Microscopy Preparation Techniques For Starch And Lipid Containing Snack Foods, F. Olga Flint

Food Structure

Many processed foods lack the structural integrity associated with biological tissue so that the conventional methods of preparation and staining used in light microscopy may introduce misleading artifacts.

Taking as examples of starch-based processed foods, potato chips (UK potato crisps) and three distinct potato snack foods, methods for preparing and demonstrating the constituents present in cryosections of whole and masticated products are discussed. To show constituents in their true relative locations vapor staining and polarized light are used. Iodine vapor staining indicates the extent of starch gelatinisation in the dry snack and it is also used to show the structural …

Electron Microscopy Of Milk And Milk Products: Problems And Possibilities, D. G. Schmidt

Food Structure

Milk and dairy products have frequently been studied by transmission- and scanning electron microscopy. The specimen preparation procedure may considerably influence the final result, and formation of artefacts is frequently observed. In this respect, formation of ice crystals during cryofixation is a well-known phenomenon. But dehydration, to an extent such as is required for embedding procedures, also appears to be harmful to dairy products. Micrographs of thin sections of plastic- embedded samples of casein submicelles show threadlike material, whereas in freeze-etched specimens only spherical particles are found. Similar observations are made when samples of cheese and of concentrated milk are …

Fluorescence Microscopy Of Cereals, R. G. Fulcher

Food Structure

The fluorescence microscope is one of the most sensitive instruments available for morphological and microchemical analysis of biological material, and especially of cereal grains. Recent innovations in illuminating systems, fluorescence chemistry, and specimen preparation have combined to provide significant improvements over conventional bright-field microscopy in both specificity and sensitivity. A variety of relatively specific fluorescent markers has been devised for routine and high resolution detection of all major cereal components. Several examples of useful fluorescent markers are described, including appropriate methods for specimen preparation, fluorescence analysis, and photography.

Food Microstructure: An Integrative Approach, E. A. Davis, J. Gordon

Food Structure

The integration of information at all levels of organization in a food system - atomic and molecular through macroscopic properties is illustrated with cake batters as an example of a formulated food and bovine muscle as an example of a biologically intact, non-formulated food. Direct examples are given using macroscopic data collected in heat and water transport studies followed by integration of microscopical data for interpretive purposes.

The contribution of starch gelatinization to the characteristics of water loss in batter is related to events such as loss of brief ringence as seen by polarizing microscopy , differential heat input as …