Life Sciences Commons^™

The Retention Of Contractility Of Rabbit Myofibrils During Storage At 25 C, Makoto Nakamura, Michio Muguruma, Toshiyuki Fukazawa, Mamoru Yamaguchi

Food Structure

During postmortem storage of muscle at 25 degrees C, myofibrils retained the ability to contract for more than 400 hours under experimental conditions used to prevent bacterial contamination of the meat surface. During t his time, rapid breakdown of troponin T was observed. Storage beyond 500 hours resulted in rapid loss of contractility correlating with proteolysis of the heavy chain of myosin, an din this stage some granules were observed along the whole A-band within the sarcomere.

Characterization Of Hypercontracted Fibers In Skeletal Muscle Of Domestic Turkey (Meleagris Gallopavo), A. Sosnicki, R. G. Cassens, D. R. Mcintyre, R. J. Vimini, M. L. Greaser

Food Structure

Several different muscles from a population of thirty Large White male turkeys were studied by histological and histochemical methods, and a high incidence of hypercontracted fibers was noted . The fibers were characterized in cross-section by an apparent swelling, a rounded rather than polygonal shape and a homogenous appearance. They were eosinophilic, positive to Gomori-trichrome and appeared to have an elevated lipid content. An unusual histochemical profile was noted. It was postulated that the hypercontracted fibers were real , not artifnctual, and resulted from some change occurring in the muscle.

Microstructure Of Shortenings, Margarine And Butter - A Review, A. C. Juriaanse, I. Heertje

Food Structure

Fat spreads are composed of liquid oil, fat crystals and water. The fat crystals in these products give the product the required consistency and stabilize the water droplets. Shortenings are waterfree products , the rheology of which depends on the solid fat content and interactions between fat crystals. Size and interaction between crystals is influenced by both composition and processing. Crystals form a three - dimensional network. Recrystallization phenomena, especially formation of large beta- crystals , can create product defects like sandiness. Margarines and halvarines are water- in - oil emulsions and have a relatively simple product structure. Because of …

The Microstructure Of Spray-Dried Microcapsules, M. Rosenberg, Y. Talmon, I. J. Kopelman

Food Structure

A newly developed technique for SEM sample preparation has been applied in the study of the effects of process parameters on the microstructure of gum arabic spray-dried microcapsules. The technique, that employs embedding in an apolar resin and partial polymerization makes it possible to simultaneously observe the inner and outer structure of microcapsules. Our results show how the core material is organized in the solid wall matrix, existence of one or more internal voids in the microcapsule, indentation and caps in the exterior of the microcapsules, and how these microstructural features are affected by solids concentration in the sprayed emulsion, …

The Effects Of Gamma Irradiation And Calcium Treatment On The Ultrastructure Of Apples And Pears, E. Kovacs, A. Keresztes, J. Kovacs

Food Structure

The post-storage quality of fruits depends on the ultrastructure of the outer tissues and on the fruit mineral composition (mostly on calcium). Pectins and their bonds with calcium play a central role in the tissues during ripening.

During senescence the middle lamella disappears from the cell walls, the fruits become soft and cell wall reticulation can be seen. There are changes within the cells too; plasmalemma separates from the wall, tonoplast from the cytoplasm, and plastids, mitochondria and nuclei are disorganized.

The ultrastructure of the skin and flesh of apples and pears were studied as a function of treatments (calcium, …

Effects Of Lignification, Cellulose Crystallinity And Enzyme Accessible Space On The Digestibility Of Plant Cell Wall Carbohydrates By The Ruminant, M. S. Kerley, G. C. Fahey Jr., J. M. Gould, E. L. Iannotti

Food Structure

Intrinsic characteristics of plant cell walls limiting susceptibility of structural carbohydrates to microbial attack in the ruminant's gastrointestinal tract are lignification of the cell wall, covalent bonding of phenolic acids to cell wall polysaccharides, the crystalline structure of cellulose and limited fibrolytic enzyme accessible space. The exact mechanism by which or degree to which each of these characteristics affect rate and/or extent of cell wall polysaccharide hydrolysis by gastrointestinal tract microbes is not well understood. Lignification and limited enzyme accessible space probably affect the extent of cell wall degradation by preventing contact between microbial enzymes and cell wall polysaccharides. Phenolic …

Lactose Crystallization In Commercial Whey Powders And In Spray-Dried Lactose, Zenichi Saito

Food Structure

Two kinds of whey powder, one containing only amorphous lactose, and the other containing precrystallized lactose, and spray-dried amorphous lactose were examined for particle structure by scanning electron microscopy. Lactose crystallization under 75th relative humidity was studied by X-ray diffraction analysis. Scanning electron microscopy appeared to detect changes due to lactose crystallization on the smooth surface of the particles examined. Lactose crystallization s tarted within 30 minutes after exposure to the humid atmosphere. Both a-lactose hydrate and B-lactose crystals were detected in the s pray- dried amorphous lactose by X -ray diffraction within 40 minutes under the humid conditions. Only …

Development Of Microstructure In Raw, Fried, And Fried And Cooked Paneer Made From Buffalo, Cow, And Mixed Milks, Miloslav Kalab, S. K. Gupta, H. K. Desai, G. R. Patil

Food Structure

Paneer was made from cow, buffalo, and mixed cow and buffalo milk by coagulation with citric acid at pH 5.5. All milk samples were heated to 90°C. Cow milk was coagulated at this temperature but buffalo and mixed milks were cooled to 70°C before coagulation. Differences in the composition and the treatments of the cow and buffalo milks were reflected in the composition and structure of the paneers. Electron microscopy revealed that raw paneer samples had a granular structure consisting of protein particles having a core-and-lining ultrastructure. Deep-frying in vegetable oil at 175'C for 4-5 min led to the compaction …

Changes In The Microstructure Of Saint Paulin Cheese During Manufacture Studied By Scanning Electron Microscopy, Micheline Rousseau

Food Structure

The Saint Paulin cheese used in this study contains 45% fat. Changes in curd structure were followed during syneresis until the end of ripening. Two scanning electron microscopy (SEM) techniques were used: the conventional technique with sample fracture after critical point drying, and cold-stage SEM after rapidly freezing samples at -160 C. The two techniques are complementary since the first leads to satisfactory observation of casein, while the other is more suitable for observing fat globules.

Sample Holders For Solid And Viscous Foods Compatible With The Hexland Cryotrans Ct 1000 Assembly, Miloslav Kalab, Paula Allan-Wojtas, Ann Fook Yang

Food Structure

A brass block., 3 .7 mm high and 10 mm in diameter, which has three openings to accommodate rivet-type or plain tubular specimen holders for scanning electron microscopy at low temperature, has been designed to fit the Hexland Cryotrans CT 1000 assembly in place of the original aluminum disc. Viscous food samples are placed in two-piece tubular holders (0.9 mm inner diameter, 1.2 mm outer diameter) made from sterling silver, and rapidly frozen. The holders are inserted into the brass block under 1 iquid nitrogen and tightened with individual setscrews. A handle screwed into the central hole of the block …

The Application Of Cold Stage Scanning Electron Microscopy To Food Research, J. A. Sargent

Food Structure

Host foods and associated microorganisms contain water which in the vacuun of an electron microscope would rapidly evaporate at ambient temperature . In addition constituent fats may melt under the electron beam. Cryopreservation and examination at low temperature avoids these problems. The structure of emulsified or foamed products can be revealed by freeze-fracture techniques. Products such as ice cream which are not stable even under normal pressures at ambient temperature can be prepared rapidly and examined for prolonged periods.

Application Of Scanning Electron Microscopy And X-Ray Microanalysis To Investigate Corrosion Problems In Plain Tinplate Food Cans And Examine Glass And Glass-Like Particles Found In Canned Food, James E. Charbonneau

Food Structure

Scanning Electron Microscopy (SEM) and X-ray Microanalysis (EDS) have been used to investigate product container interaction problems in plain tinplate metal food containers and to examine glass and glass-like particles that were found in canned food.

Through the use of SEM-EDS, it was determined that: sulfate containing particles from the cannery cooling water reacted with exposed iron or tin-iron alloy on the tinplate surface causing an external rusting problem; sulfur dioxide was responsible for a container discoloration and a pitting corrosion problem in canned fruit nectar; hydrogen sulfide produced from the SO2-tinplate reaction was the cause of an associated off-odor …

The Role Of B-Lactoglobulin In The Development Of The Core-And-Lining Structure Of Casein Particles In Acid-Heat-Induced Milk Gels, V. R. Harwalkar, Miloslav Kalab

Food Structure

Acid-heat-induced gels were obtained by coagulating casein micelle dispersions at 90 C using glucono-and-lactone. The casein micelles used were isolated from raw skim milk by centrifugation, washed free of whey proteins and soluble salts, and dispersed in water or a milk dialyzate. The pH values of the gels varied from 4.7 to 6.3. A core-and-lining ultrastructure developed in casein particles coagulated at pH 5.2 to 5.5 from casein micelle dispersions in the milk dialyzate provided that B-lactoglobulin or whey proteins (10 mg/ml) were added to them prior to coagulation. Addition of B-lactoglobulin to aqueous casein micelle dispersions led to the …

Functional And Microstructural Effects Of Fillers In Comminuted Meat Products, Frederick W. Comer, Paula Allan-Wojtas

Food Structure

Fillers are used in comminuted meat products such as wieners to increase yield, improve stability, and modify textural properties. Light microscopy, scanning electron microscopy and transmission electron microscopy show that comminutred meat products are mechanical mixtures in which the microstructural features of starch and insoluble protein ingredients are largely retained. The water absorption and gelation properties of these ingredients contribute to the stability and textural firmness. Soluble proteins may improve stability through emulsion formation but the role of emulsion formation i s clearly secondary to that of gelation. The characteristic springy gel structure of wieners is determined by the gelation …

The Use Of Transmission Electron Microscopy To Study The Composition Of Pseudomonas Fragi Attachment Material, Paula J. Herald, Edmund A. Zottola

Food Structure

Electron microscopy techniques were used to study the attachment matrix of Pseudomonas fragi used to demonstrate the presence of attachment fibrils of P. fragi adhered to stainless steel. Transmission electron microscopy (TEM) was used to examine thin sectioned cells strained with ruthenium red or alcian blue. Extracellular substances surrounding cells stained with ruthenium red or alcian blue had a mat- or spike-like morphology. This indicated that these substances were acidic mucopolysaccharides that may be involved in the attachment of P. fragi to food contact surfaces.

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 . …

Amino Acid Composition And Structure Of Cheese Baked As A Pizza Ingredient In Conventional And Microwave Ovens, Alenka Paquet, Miloslav Kalab

Food Structure

Amino acid compositions of stirred-curd Mozzarella, stretched Mozzarella, and process Cheddar cheeses were similar and did not change as the result of baking in a conventional oven. D-glutamic acid (D0Glue) and D-phenyl-alanine (D-Phe) were present at low concentrations in all cheese samples, the lowest concentrations having been found in unbaked stirred-curd Mozzarella cheese (2.7% D-Glu of total Glu present and <1.0% D-Phe of total Phe present). The highest concentrations were detected in unbaked stretched Mozzarella cheese (5.6% and 1.2%, respectively). Thechanges were not significant and were not the result of aking, indicating that the heat treatment during baking did n ot cause racemization of the amino acids.

Each cheese had a characteristic structure before baking. The structures of the Mozzarella cheeses were altered by baking in the conventional oven and also in a microwave oven and their original features such as curd granule junction and fat globule …

Ultrastructural And Textural Properties Of Restructured Beef Treated With A Bacterial Culture And Splenic Pulp, E. A. Elkhalifa, N. G. Marriot, R. L. Grayson, P. P. Graham, S. K. Perkins

Food Structure

Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Instron measurements were used to evaluate the effects of an Achromobacter iophagus culture {BC) and splenic pulp (SP) treatments one structural and textural properties of flaked and restructured beef steaks. Both treatments improved the textural character is tics of the product when conditioned at 35°C . Electron microscopy studies revealed that the bacterial culture treatment caused a greater effect than SP on the connective tissue elements, with a degradation of the endomysial sheath and sarcolemma. Treatment with splenic pulp produced an overall excessive disruption a t the Z-lines with little definition …

Porosity, Specific Gravity And Fat Dispersion In Blue Cheeses, K. M. K. Kebary, H. A. Morris

Food Structure

Porosity was measured in Blue cheeses made from (i) homogenized butter oil - reconstituted nonfat dry milk (4% fat). (ii) homogenized butter oil reconstituted nonfat dry milk (14% fat) standardized to 4% fat with reconstituted nonfat dry milk , (iii} homogenized raw c ream (14% fat) standardized to 4% fat with raw skim milk , and (iv) homogenized pasteurized cream (14% fat) standardized to 4% fat with pasteurized skim milk. Cheeses made from (i) were the most porous and were significantly different from the other cheeses . In cheeses made from (i) and (ii) , about 40% of the holes …

The Effect Of Processing On Some Microstructural Characteristics Of Fat Spreads, I. Heertje, J. Van Eendenburg, J. M. Cornelissen, A. C. Juriaanse

Food Structure

The processing and the composition of fat spreads determine to a large extent the final product properties such as hardness, spreadability, mouthfeel, emulsion stability and salt release. In establishing the relation between composition, processing and final product properties, microstructural studies play an important role. In this context the influence of some process parameters in the production of shortenings and 80% fat spreads on microstructure and product properties has been investigated. Shear, cooling regime and crystallization conditions influence both the emulsion structure and the fat crystalline matrix. In general, working leads to softer products with a more granular crystalline fat matrix, …

The Effect Of Storage, Processing And Enzyme Treatment On The Microstructure Of Cloudy Spartan Apple Juice Particulate, D. L. Mckenzie, T. Beveridge

Food Structure

The effect of blanching, post-harvest refrigerated (4C) storage and enzyme treatment with poly-galacturonase on the microstructure of Spartan apple juice was examined by thin sectioning and negative staining transmission electron microscopy. Particles were categrized as granules (3-54 nm), spheres (20-368 nm) and aggregates (12-2519 nm). Enzyme treatment with polygalacturonase significantly decreased granule size (P < 0.01). Storage of apples significantly decreased both granule size (p < 0.01) and aggregate length (p < 0.05) and also resulted in a web-like aspect in the microscopic appearance of juice particulate. The web-like aspect of the particulate was removed either through enzyme treatment with polygalacturonase or by blanching. Blanching of puree significantly increased granule (p < 0.05) and sphere size (p < 0.01) while significantly decreasing aggregate length (p < 0.01). In addition, blanching stabilized suspended particulate by what appeared to be the formation of a protective colloid which prevented particle aggregation through electrostatic repulsion.

Scanning Electron Microscopy Of Cellular Structure Of Granny Smith And Red Delicious Apples, Gassinee Trakoontivakorn, Max E. Patterson, Barry G. Swanson

Food Structure

Immature and mature Granny Smith and Red Delicious apples (Malus domestica Borkh . ) were studied with scanning electron microscopy (SEM). Parenchyma cells were observed to form a net-like pattern in sections transverse to the stem-calyx of the apple. Bundles of about six intact cells were connected, creating large intercellular spaces. The intercellular spaces were different in shape from different perspectives to the cut surfaces ; round in stem-calyx transverse sections and elliptical in stem-calyx cross sections. Cell areas, cell lengths and intercellular space areas were determined with image analysis. The patterns of mature apple cell structure of both cultivars …