Life Sciences Commons^™

The Structure Of Gluten Gels, A. M. Hermansson, K. Larsson

Food Structure

This paper reports on a combined electron microscopy and X-ray diffraction study of gluten gel, in which conventional gluten, a delipidized gluten sample and a storage protein fraction obtained by salt-fractionation were used. It can be concluded that the gluten gel is a continuous phase of densely packed protein units. Other structural components such as air ce lls, lipid droplets, liposomes, fiber residues, starch granules etc. are dispersed in the continuous matrix. The space available for water is strictly limited in the continuous phase due to the dense packing of protein molecules. Water that is not completely separated from the …

Determination Of Internal Color Of Beef Ribeye Steaks Using Digital Image Analysis, K. Unklesbay, N. Unklesbay, J. Keller

Food Structure

Objective measurements of beef ribeye steaks were made to determine the color distribution throughout their interior after heat processing. Steaks from eight animals were grilled to five degrees of doneness according to traditional internal temperature specifications. Images of the interior of these steaks, as seen by a digital image processing system through red, green, and blue filters were analyzed. The mean, standard deviation, skewness, and kurtosis of the histograms of light intensity at all points throughout the surface were determined. The steaks were also analyzed raw and it was determined that little variation in the color of muscle tissue occurred …

Relationship Between Microstructure And Susceptibility To Syneresis In Yoghurt Made From Reconstituted Nonfat Dry Milk, V. R. Harwalkar, Miloslav Kalab

Food Structure

Increase in the density of protein matrices i n yoghurt samples conta ining 10 to 30% total milk sol ids was studied by scanning electron micros copy and was corr e lated with a decrease in syneresis. Casein particles which formed chains and clusters in the protein matrix were largest in the 10% total solids yoghurt and their dimensions were decreased as the total solids contents were increased. This observation was confirmed by transmission electron microscopy of thin sections. An attempt has been made to explain the discrepancy between results on syneresis obtained by a drainage and a centrifugation method …

Features Of Food Microscopy, D. F. Lewis

Food Structure

The value of food microscopy is judged by its practical application to food handling. Hence microscopists must explain the relevance of their findings to food technologists. The food microscopist has to deal with materials that are particularly difficult to prepare for microscopy because they often contain high levels of fat, air, sugar, salt, starch or acid. Sometimes the methods used are unorthodox and could be regarded as questionable by microscopists in more traditional disciplines. This paper considers the relationship between food microscopists, food technologists and other microscopists. An approach to interpretation of images is based on the following features. 1) …

Texture And Microstructure Of Soybean Curd (Tofu) As Affected By Different Coagulants, J. M. Deman, L. Deman, S. Gupta

Food Structure

The coagulating properties of five coagulants and the nature of the curd obtained from soymilk was investigated . Viscosity changes during coagulation were studied using a Namctrc Vibrating Sphere Viscometer and texture measurements were made by compression and computer assisted analysis. pH and amount of solids in the whey were determined. The microstructure of the tofu was examined by sca nning electron microscopy. It was observed that CaCI2.2H20 and MgCI2.6H20 coagulaled the milk in stantl y while CaS04 .1/2H20. glucono delta l a~tonc (GOL) and MgS04 .7H20 acted comparatively slowly. The t exture of the curd was greatly influenced by …

Cryo-Scanning Electron Microscopy Of Microorganisms In A Liquid Film On Spoiled Chicken Skin, T. A. Mcmeekin, D. Mccall, C. J. Thomas

Food Structure

Cryo-scanning electron microscopy was used to examine bacteria which had grown in a liquid film on the skin surface of poultry carcasses. Pits or void zones surrounding bacteria on ethanol-dehydrated, critical point dried (CPD) samples were not found on washed or untreated specimens frozen prior to examination by scanning electron microscopy (SEM). However, pits equivalent to those produced during chemical fixation and dehydration were formed when skin tissue was treated with ethanol prior to freezing. We conclude that the pits are dehydration artifacts caused by the chemical preparative methods employed rather than the result of degradation of film proteins by …

The Microstructure Of The Hen's Egg Shell - A Short Review, R. M. G. Hamilton

Food Structure

The structure of the hen's egg shell can be divided into five separate layers . The Innermost layer consists of two distinct membranes known as the inner and outer shell membranes. These membranes are compos ed of networks of protein/polysaccharide fibres and are =70 mm thick. Attached to the outer fibres of the outer membrane are polycrystals of calcite (calcium carbonate) which extend outward in an inverse conical manner until the cones from several sites of crystal i nit iation fuse together. The fibre/ crystal attachment sites, known as basal caps, and the cones form the mammillary knobs layer which …

Mucilage In Yellow Mustard (Brassica Hirta) Seeds, I. R. Siddiqui, S. H. Yiu, J. D. Jones, M. Kalab

Food Structure

Release of mucilage from yellow mustard (brassica hirta, also known as Sinapis alba) seed coats (hulls) was studied by optical and scanning electron microscopy. Micrographs were obtained of the mucilage which had exuded from briefly moistened seeds and dried subsequently in the form of small droplets on the seed surface.

The mucilage collected from the seed surface and mucilage isolated on a larger scale from seed hulls was hydrolyzed with sulfuric acid and the hydrolyzates were analyzed for sugar composition. Galactose, glucose, and galacturonic acid were found to be major components and mannose, arabinose, xylose, and rhamnose were minor components. …

Accuracy And Utility Of Sarcomere Length Assessment By Laser Diffraction, Peter A. Koolmees, Frank Korteknie, Frans J.M. Smulders

Food Structure

In two experiments the computation of sarcomere length from laser diffraction patterns was tested for accuracy against phase-contrast microscopy . Particular attention was paid to methodological factors such as sampling location and computation formulae. Correlation coefficients between the laser diffraction technique and the microscopical method were high (r= 0.96) in both experiments. However, when computed from a simplified formula, the sarcomere length values, determined by laser diffraction patterns tended to be approximately 0. 10 lJm lower. It is recommended to use the correct formula in computing the laser diffraction data and to investigate a limited number of fibres (3) in …

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 …

Ultrastructure Of Cooked Spaghetti, M. A. Pagani, D. J. Gallant, B. Bouchet, P. Resmini

Food Structure

Several electron microscopy (EM) complementary techniques (scanning electron microscopy, freeze-fracturing and thin-sectioning) have been applied in the ultrastructural study of spaghetti.

Experimental spaghetti have been produced starting from two semolinas from the same wheat cultivar and using a low temperature (LT) and very high temperature (VHT) drying schemes.

Cooking quality of these products was not related to the quantity of the main components present in semolina. however, the drying conditions (temperature and humidity) and the nature of the cooking water greatly influenced cooking characteristics.

The three EM techniques were used to detected differences in protein and starch organization in relationship …

Ultrastructure Of Maize Starch Granules. A Review, Daniel J. Gallant, Brigitte Bouchet

Food Structure

History of starch granule ultrastructure and the principal data obtained on maize starch granules are analyzed. New results are developed: i) growth and development of the maize starch granules during maturation depend on the maize varieties and the tissue site in the kernel, especially the horny and flloury endosperms; ii) cytochemical studies of the starch granules differing from their amylose/amylopectin ratio show important differences in the distribution of their crystalline and amorphous zones that explain their behaviour under some hydrolytic treatments; iii) complexing between colloidal gold labelled concanavalin-A and starch (amylopectin) permits new and greater specificity to ultrastructural study of …

Mechanical Properties Of Cheese, Cheese Analogues And Protein Gels In Relation To Composition And Microstructure, M. L. Green, K. R. Langley, R. J. Marshall, B. E. Brooker, A. Willis, J. F. V. Vincent

Food Structure

Samples of commercial Cheddar cheese, experimental Cheddar cheeses made from heated, ultrafiltration-concentrated mllks, processed cheese analogues and whey protein gels of defined composition were examined microscopically and some fracture and deformation properties were determined. Surfaces of cheese prepared by critical point drying and those examined frozen were comparable in microstructure. As the concentration factor of the milk used for experimental c heesemaking increased, the cheese became more resistant to reversible deformation, the work required to cut with a wire or break wf th a hammer increased and the microstructure showed that the protein matrix was coarser. The force to deform …

Effects Of Processing And Cooking On The Structural And Microchemical Composition Of Oats, S. H. Yiu

Food Structure

Fluorescence microscopy was used to analyze the structural and microchemical organization of oat constituents in cooked and uncooked products of whole grain and three commercial ly available rolled oats. Results of the microscopic examination indicated that proteins and lipids in the endosperm tissue were most susceptible to processing. Instead of being individually packaged in distinct structural units like those found in unprocessed groats, both proteins and lipids appeared as aggregated masses after processing. Cooking induced further aggregation. Starch grains in the uncooked rolled oat samples still retained their granular. polygonal structures. although some compound grains were broken up into individual …

Structural Characteristics Of Eleusine Corocana (Finger Millet) Using Scanning Electron And Fluorescence Microscopy, C. M. Mcdonough, L. W. Rooney, C. F. Earp

Food Structure

The objective of this study was to document the microstructure of finger millet wlth scanning electron and fluorescence microscopies. Finger millet is an utricle which is spheri ca 1 and about 1 . 5 ITlT1 in diameter. The membranous peri carp of finger millet was loosely associated with the seed at maturity. Beneath the loose pericarp wa s a five-layered testa that varied from red to purple in color. The outer layer was the only testa layer that autofl uoresced, suggesting the presence of phenolic acids, i .e., ferulic acid. The aleurone layer was beneath the testa , and was …

Fluorescence Characterization Of The Mature Caryopsis Of Sorghum Bicolor (L.) Moench, C. F. Earp, L. W. Rooney

Food Structure

Fluorescence microscopy was used to characterize the mature car yaps is of Sorghum bicolor (L.) Moench . Acid Fuchsin, a protein specific dye used in bright field microscopy, caused protein bodies and matrix in the sorghum endosperm to fluoresce. ANS (8-ani lino-1- naphthal e ne sulfonic acid) also caused the protein bodi es and matrix in the endosperm to fluoresce. Varietal differences in endosperm protein dist r ibution were evident when viewed after sta · ning with Acid Fuchsin . Nile Blue A caused fl uorescence in neutral lipids such as those in :he lipid bodies in the aleurone and …

Fixing Conditions In The Freeze Substitution Technique For Light Microscopy Observation Of Frozen Beef Tissue, M. N. Martino, N. E. Zaritzky

Food Structure

The freeze substitution histological technique allows the indirect light microscopicobservation and the quantitative evaluation of ice crystal size in frozen tissues. Theuseofchemical fixatives in substitu ting fluids improves morphological and histochemical preservation of the tissue. Fixation conditions become important since this step can introduce modifications in crystal sizes . Effects of temperature on: a) diffusion rate of fixing solution in tissue, b) recrystallization rate of ice in frozen beef and c) variations of the froze~ water fraction were ana lyzed, establishing that 1sothermal freeze fixation constitutes an appropriate method for histological observation. Fixing at temperatures lower than that of the …

Changes In The Microstructure Of Skipjack Tuna During Frozen Storage And Heat Treatment, L. E. Lampila, W. D. Brown

Food Structure

Samples of fresh, frozen and heat- treated skipjack tuna muscle were observed by scanning electron mieros copy. The photomicrographs were used to assess changes in the microstructure of fish muscle during frozen storage and thermal processing . Differences noted in frozen tissue could be related to the formation of gaps between fibers and the deformation of muscle fibers . No freeze mediated damage to the cell wall was observed at the lower limits, 20,000x, of high resolution scanning electron microscopy. The degree of muscle fiber shrinkage and erosion and the behavior of certain protein fractions was found to be affected …

Freeze Texturation Of Proteins: Effect Of The Alkali, Acid And Freezing Treatments On Texture Formation, Frisco I. Consolacion, Paul Jelen

Food Structure

The effects of alkali extraction, isoelectric precipitation, and rate of ice crystal formation on protein interaction in the freeze texturization process were studied , The protein isolate was obtained from mechanically deboned poultry meat residues by extraction with NaOH at pH 10.5 and precipitation by HCl at pH 5, 0, The presence of large molecular weight subunits in the protein isolate was revealed by SDS-polyacrylamide gel electrophoresis. Scanning electron microscopy demonstrated the nature of the fiber formation and protein cross-linking as affected by freezing at -25'C or -196'C. The transformation of the level of protein organization from the lumpy or …

Action Of Polyphosphates In Meat Products, D. F. Lewis, Kathleen H.M. Grooves, J. Hilary Holgate

Food Structure

The action of polyphosphates on meats has been examined in studies using different meats and has been compared with other treatments. The results were monito red by recording cooked yield and observing changes in structure by electron microscopy. Four possible characteristics of polyphosphates are considered: pH, sequestering action, ionic strength and as an ATP (adenosine triphosphate) analogue. In the conditions used in these experiments, the pH-buffering effect of polyphosphates is found as the principal characteristic in meat products.

Some meats were found to be more affected by polyphosphates than others and:. hypothesis is developed to explain this. It is proposed …

Microscopal Observations On The Structure Of Bacon, C. A. Voyle, P. D. Jolley, G. W. Offer

Food Structure

Commercially processed salt-treated pig longissimus dorsi muscle, in the form of bacon slices, sometimes shows localized variations in the light-scattering properties of the tissue. The phenomenon is described as 'tiger-stripe'. A study of areas of tissue showing such variations, using electron microscopy, has revealed differences in the structure at the myofibrillar level. Areas which appear dark when viewed by incident illumination show ordered myofibrillar structure, whereas areas which appear light under similar viewing conditions appear to be disordered.

Microstructure Of Mealy And Vitreous Wheat Endosperms (Triticum Durum L.) With Special Emphasis On Location And Polymorphic Behaviour Of Lipids, A. Al Saleh, D. Marion, D. J. Gallant

Food Structure

Dark inclusions observed in osmiophilic zones, already described in mature wheat endosperm using transmission electron microscopy, were confirmed by freeze-fracture electron microscopy to be lipids. The polar lipids (glycolipids, phospholipids, free fatty acides, monoglycerides) were organized in a liquid crystalline phase. The reversed hexagonal or HII phase should be the main lattice which might arise from the transition of lipids present in membranous structures as a lamellar phase. This transition was caused by dehydration occurring during maturation. It is suggested that the water-dependent lamellar hexagonal phase transitions are of considerable importance in cereal food technology.

Rheological And Particle Size Changes In Corn Oil-In Water Emulsions Stabilized By 7s Soybean Proteins, M. Reeve, P. Sherman

Food Structure

The viscoelastic properties and mean drop size (Om) of corn oil-in-water emulsions stabllized by 0.5-1.5% (wt/wt) 7S soybean proteins have been examined at various pH•s . Changes 1n these parameters when the ernul sions were stored at 4-5°C were measured also. Viscoelasticity ~arameters were derived from time-dependent strain behaviour at a constant low shear stress of 41 .7 dyne cm- 2. Although each emulsion showed a continuous increase in D during storage, due to drOIJ coalescence, 1l"s instantaneous elastic modu l us (G) rose initially over several days to an op£imum value and then subsequently decreased, The trends in D …

The Skinned Fiber Technique As A Potential Method For Study Of Muscle As A Food, R. G. Cassens, T. J. Eddinger, R. L. Moss

Food Structure

Skeletal, smooth and cardiac muscle cells can be skinned by physical means or a variety of chemical techniques. The skinned fibers have been used to study the molecular mechanisms of contraction and the regulation of contraction by ca++. Skinned fiber preparations are also useful for study of muscle as a food. For example, it is now possible to determine fiber type of skinned fibers following study of their physical properties.

Current Concepts Of Muscle Ultrastructure With Emphasis On Z-Line Architecture, M. Yamaguchi, H. Kamisoyama, S. Nada, S. Yamano, M. Izumimoto, Y. Hirai, R. G. Cassens, H. Nasu, M. Muguruma, T. Fukazawa

Food Structure

Invertebrate striated muscle, the Z-line, which defines the sarcomere length, presents diverse structural patterns both in cross section and in longitudinal section. Conflicting models have been proposed to explain the microscopic observations. The protein composition of the Z- line structure is unresolved. o: -Actin in is widely accepted as a Z-line component, and actin filaments extend into wide Z-lines. Based on recent findings from our laboratory and others, we developed a new model applicable to wide and narrow Z-lines. The model allowed the observed ultrastructural patterns of Z-lines to be simulated. Improved electron microscopic techniques should allow further progress to …

Comparative Microscopy And Morphometry Of Skeletal Muscle Fibers In Poultry, Carol S. Williams, John W. Williams, Ronald A. Chung

Food Structure

Two experiments comparing microscopic analyses were performed using two cooking methods an:t two different muscles from both chickens and turkeys. In the first experiment, breast (pectoralis) and thigh (quadriceps) muscle taken from male and female Rhode Island Red chickens at three ages (10 weeks, 25 weeks and 52 weeks) were cooked in a microwave oven . Samples were collected for observation with brightfield, phase contrast, interference contrast (Nomarski) and transmission electron microscopy. Samples from the same muscle areas were provided for taste pane l evaluation . In the second experiment, breast and thigh samples were collected from 10-week old male …

Microstructure Of Lentil Seeds (Lens Culinaris), Joe S. Hughes, Barry G. Swanson

Food Structure

Scanning electron microscopy (SEM) was used to investigate the microstructure of five cultivars of lentil seeds (Lens culinaris). Lentil cot yledons contain sphericai starch granules surrounded by protein bodies similar to starch granules and protein bodies observed in cotyledons of other food legumes. Examination of the lentil seed coat in cross - section revealed outer palisade and inner parenchyma layers characteris tic of legumes. The subepidermal layer, however, is comprised of hourglass cells and is found primarily in the area surrounding the hilum and the entire lentil seed coat is thinner than the seed coat s of most other food …

Lipolytic Changes In The Milk Fat Of Raw Milk And Their Effects On The Quality Of Milk Products, E. Kirst

Food Structure

Lipolytic changes in milk rat affect sensory attributes and techno logicaI properties of milk and milk products. They are affectcd by physiologal, thermal . and biochemical factors as well as by the mechanics of fluids Lipolytic processes in milk are intensified by modern processing methods.

In this review. special attention has been paid to runinant- related feeding of dairy cows. foaming of milk. mechanical and thermal influences and the growth of psycllrotrophic bacteria.

Feeds deficient in energy affect the chemical composition of the milk fat. Tests have shown that on an average. approximatey 55% of free fatty acids in the …

The Development Of Structure In Whipped Cream, B. E. Brooker, M. Anderson, A. T. Andrews

Food Structure

Interfacial changes occurring during the formation of whipped cream were followed using transmission and scanning electron microscopy. During the initial stages of whipping, air bubbles were stabilized by adsorbed 8-casein and whey proteins with little involvement of fat globules. The adsorption of fat to a i r bubbles occurred ~.then the globule membrane coalesced with the protein a ir-water i nterface . As a res ult, fat was brought into direct contact with air but only rarely did it spread at the ai.r-fat interface. The crosslinking of fat globules adsor bed t o adjacent air bubbles by chains of coalesced …

Electron Dense Granules In Yoghurt: Characterization By X-Ray Microanalysis, Estelle M. Parnell-Clunies, Yukio Kakuda, Richard Humphrey

Food Structure

A study was undertaken to investigate the influence of buffer composition, pH and glutaraldehyde fixation time on the appearance of electron dense granules in yoghurt. Yoghurt particles were fixed in 3.5% glutaraldehyde and postfixed in 2% osmium tetroxide in verona! acetate or phosphate buffer. Thin sections were examined unstained with an electron microscope equipped with a scanning transmission electron microscope module and energy dispersive X- ray analyser.

Electron dense granules appeared whenever glutaraldehyde and osmium tetroxide were utilized sequentially, irrespective of the type of buffer, pH (5.0 vs 6.75), or glutaraldehyde fixation time (2 or 24 h). Granules were absent …