Life Sciences Commons^™

Microstructure Of Whey Protein/ Anhydrous Milkfat Emulsions, M. Rosenberg, S. L. Lee

Food Structure

Research has been undertaken in order to determine the microstructure of emulsions consisting of whey proteins and anhydrous milk fat. The results revealed that whey protein films were formed at oil/water interfaces. Scanning electron microscopy (SEM) analysis of chemically fixed specimens1 and cryo-SEM analysis of partially etched, fro zen specimens revealed that the ad sorbed protein layer (coating the fat droplets) had a granular, aggregated appearance. Emulsions with a high fat load prepared under high homogenization pressure exhibited a bimodal particle-size distribution. Clu!;tering of the protein-coated droplets, and sharing phenomena at the oil / protein interfaces were evident in these …

A Comparison Of The Effects Of Oven Roasting And Oil Cooking On The Microstructure Of Peanut (Arachis Hypogaea L. Cv. Florigiant) Cotyledon, Clyde T. Young, William E. Schadel

Food Structure

Peanut (Arachis hypogaea L. cv. Florigiant) cotyledon microstructure after oven roasting and oil cooking at 160 C was documented with scanning electron microscopy, light microscopy and transmission electron microscopy . Changes in peanut cotyledon microstructure were compared as thermal processing time at 160°C was increased for both oven roasting and oil cooking. The purpose was to evaluate thermal modifications in the cytoplasmic network, protein bodies and cell-to-cell junctions as thermal processing time in creased for each heating method. Principal findings included differences in the times at which these modifications occurred during the two thermal processes. Oven roasting a t 160 …

Microstructural Approach To Legume Seeds For Food Uses, Kyoko Saio, Michiko Monma

Food Structure

This review summarizes the microstructures of several seed legumes based on previous work and some new findings. Fifteen species of tropically grown legumes , adzuki bean and soybeans (a leading variety and two local va rietie s) were examined by light and transmission electron microscopy in relation to food uses. Processing of adzuki beans to form Q!l bean paste is dis cussed to illustrate the effects of processing on microstructure of starch g rains. Differences in contents, shape and size of starch grains are emphasized in a comparison of soybeans wi th other legumes.

Structure-Compressive Stress Relationships In Mixed Dairy Gels, J. M. Aguilera, J. E. Kinsella, M. Liboff

Food Structure

Mixed dairy gels (including a control without fat) of skim milk powder (SMP) and whey protein isolate (WPI) containing fat globules were formed by heating protein emulsions to 90°( and by acid release from glucono- 0-lactone to provide a pH of 4.3-4.4 . Fat globules with artificial protein membranes (FGAPM) were prepared by homogenization of a butter oil /water mixture in the presence of WPI while fat globules without membranes were stabili zed with polyoxyethylene sorbitan monolaurate (Tween 20). Both emulsions were added at a 4% (w/w) leve l to solutions having 3% SMP and 8.3% WPI. The gel contai …

An Apparatus For A New Microcube Encapsulation Of Fluid Milk In Preparation For Transmission Electron Microscopy, M. C. Alleyne, D. J. Mcmahon, N. N. Youssef, S. Hekmat

Food Structure

A simple apparatus has been developed for a new "microcube" encapsulation of fluid milk samples in their prefixation preparation for electron microscopy. The new technique is based on making cubic wells in an agar gel layer, filling them with fluid milk samples, and sealing them with another agar gel layer . The individual wells are then separated by cutting from the initial block, providing 0.5 mm walls around the samples. The embedded material (milk, buttermilk, yogurt, etc.) is fixed, dehydrated , and embedded in a resin for transmission electron microscopy. The procedure is simpler, and more versatile, reliable, and reproducible …

Identification Of Proteins And Complex Carbohydrates In Some Commercial Low-Fat Dairy Products By Means Of Immunolocalization Techniques, Barbara L. Armbruster, Nitin Desai

Food Structure

Macromolecular assemblies of proteins and hydrocolloids in low-fat dairy products contribute to the structure and texture of these foods. Immunolocalization techniques were used to identify B-lactoglobulin, casein, bovine whey proteins, and egg albumin in low-fat frozen desserts, reduced fat process cheese, and salad dressings. SimpJesse18 I 00 protein particles were examined and characterized by these methods and compared to naturally occurring protein structures in the low-fat foods. Hydrocolloid identification in low-fat salad dressing was accomplished by complexing cellulase and hemicellulase with colloidal gold and applying the probe as a pre-embedding step, on sections of embedded specimens or on material dried …

Structure And Rheology Of String Cheese, S. Taneya, T. Izutsu, T. Kimura, T. Shioya

Food Structure

String cheese samples ranging in pH from 5.0 to 5.9 were prepared by kneading Mozzarella curd and stretching it 2 to 80 times. Rheological properties were examined by compression, stress relaxation , and flow property tests. Stringiness was tested by a device specifically designed for this purpose: a standardized string was pulled from the sample at a direction perpendicular to the orientation of the curd and the amount of fibres resulting from this process was quantitated using digital image analysis.

Force-deformation curves implied that the curd prepared by kneading may be considered to be an incompressible viscoelastic body similar to …

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

Food Structure

No abstract provided.

Ultrastructural Evidence For Temperature-Dependent Ca2+ Release From Fish Sarcoplasmic Reticulum During Rigor Mortis, Hideki Ushio, Shugo Watabe, Muneaki Iwamoto, Kanehisa Hashimoto

Food Structure

The release or leakage of ca2+ from the sarcoplasmic reticulum (SR) during rigor mortis of fish muscle was investigated by transmission electron microscopy using pyroantimonate and related biochemical changes.

Ca2+ -pyroantimonate deposits were observed in the SR immediately after spiking the fish. At the onset of rigor for fish stored at 0°C, no deposits were found in the SR; however, fish stored for the same period at woe which were still in the pre-rigor state, clearly showed Ca2+ deposits in the SR.

In association with the Ca2+ translocation, ATP degraded faster at 0 c than at 10 °C, probably due …

Microstructure Of Peanut Seed: A Review, Clyde T. Young, William E. Schadel

Food Structure

Mature peanut seed microstructure of importance to the food industry is examined with regard to: (1) anatomy and cytology of peanut seed; (2) the effects of environment on peanut seed; and (3) the effects of various processing procedures on peanut seed. Current peanut seed microstructure research by the authors is directed toward evaluation of the quality of processed peanuts including using TEM, SEM and LM to evaluate the effects of different times of oven roasting at the same temperature, and a method for evaluating quality of homogenization of broken cell and tissue fragments, protein bodies and starch in stabilized peanut …

Preparation Of Cereals And Grain Products For Transmission Electron Microscopy, Donald B. Bechtel

Food Structure

This tutorial specifically addresses the techniques used in the processing of cereals and grain products for various aspects of transmission electron microscopy. Methods covered include sample treatment, chemical and physical fixation, dehydration, embedding, sectioning techniques, immunocytochemistry, enzymatic digestions, carbohydrate localization, and lectin binding. The primary goal is to provide information on the preparation of cereals and cereal-based products for microscopic analysis and to assist the reader in solving technical problems associated with studying cereals or other difficult-to-prepare samples.

Effect Of High-Pressure Homogenization On A Sterilized Infant Formula: Microstructure And Age Gelation, Y. Pouliot, M. Britten, B. Latreille

Food Structure

Age thickening and gelation of an Infant formula was Induced by applying high pressure homogenization prior to in-can sterilization. The Initial viscosity of the preparation increased with Increasing homogenization pressure. Thickening rate upon storage, as monitored by viscosity changes, was also proportional to the pressure applied during homogenization. Optical and electron micrographs of 6 month-old samples showed evidence of aggregation. The effect of dissociating agents on the viscosity and microstructure of these samples suggested a contribution of hydrogen bonds and calcium bridges to the gel integrity. The alteration of the mineral balance of aged samples also Indicated a gel strengthening …

Transmission And Scanning Electron Microscopy Of Peanut (Arachis Hypogaea L. Cv. Florigiant) Cotyledon After Roasting, Clyde T. Young, William E. Schadel

Food Structure

Changes in the microstructure of peanut (Arachis~ L. cv. Florigiant) cotyledon after roasting at a temperature of 160°C for 16 minutes were investigated with transmission and scanning electron microscopy. Thermal modifications were documented with photomicrographs of t he cytoplasmic network , protein bodies, starch grains and cell-to-cell junctions after oven roasting. These thermal modifications include disruption of the cytoplasmic network, distension of protein bodies, decreased stain affinity of starch grains , and disintegration of middle lamellae in some cell-t o-cell junctions.

Heat-Set Gels Based On Oil/Water Emulsions: An Application Of Whey Protein Functionality, R. Jost, F. Dannenberg, J. Rosset

Food Structure

The microstructure of portein/lipid gels produced by heat treatment of whey protein stabilized oil-in-water(O/W) emulsions was studied. Scanning electron microscopy as well as transmission electron microscopy was performed on glutaraldehyde/osmium tetroxide fixed, and critical point-dried samples. Microstructure analysis showed that in the case of homogenized O/W emulsions, extensive coating of the fat globule surface with coagulated protein led to a "cauliflower - like" structure. In such gels, uncoated fat globules having smooth surfaces were not present. This specific microstructure was not obtained with protein/lipid gels in which whey protein was added in the continuous phase and mixed with a O/W …

Rheology And Microstructure Of Strained Yoghurt (Labneh) Made From Cow's Milk By Three Different Methods, A. Y. Tamime, M. Kalab, G. Davies

Food Structure

Labneh is the name for strained yoghurt, i.e., yoghurt made with an elevated solids content, which has originated in the Middle East. For this study , three types of Labneh were made from cow' s milk: (a) "Traditional Labneh" was produced by straining yoghurt in a cloth bag, (b) "UF Labneh" was made by ultrafiltration of warm yoghurt , and , (c) "UF Retentate Labneh" was obtained by culturing homogenised ultrafiltration (UF) milk retentate. A 11 products were passed through a lactic curd homogen is er to smoothen the Labneh curd . Total solids contents of t he products were …

Influence Of The Extrusion Process On Characteristics And Structure Of Pasta, M. Ambrogina Pagani, Plerpaolo Resmini, Gerardo Dalbon

Food Structure

The effects of the kneading and forming process or pasta quality have been investigated. Using the same blend of wheat flour and keeping mixing and drying conditions constant, three types of spaghetti were produced using the following three kneading and forming processes: A) kneading with a continuous press and forming by pressure-extrusion; B) kneading and forming by sheeting-rolls; C) kneading by hand and forming with sheeting-rolls. These three processes impart different mechanical work on the dough.

The three types of dried spaghetti exhibited differences in cooking requirements and in cooing quality. Spaghetti (A) absorbed water more slowly and showed poor …

The Effect Of Irradiation On Starch Content In Golden Delicious Apples, E. Kovacs, A. Keresztes

Food Structure

Starch content in apple (Golden Delicious) skin and flesh was studied as a function of radiation dose (0, 0.5, 1, 2 and a 5kGy) after 8 weeks shelf life (16 C, 80-90% RH).

Starch was generally not found in the flesh with the exception of the 5 kGy sample. Starch grains were observed, however, in plastids of the epidermis and especially in the hypodermis in correlation with the radiation dose. 1 kGy dose caused a significant effect (p>99, 98%) on retardation of starch breakdown measured by electron microscopic morphometry and chemical analysis.

Analysis showed that increasing radiation dose increased …

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, …

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.

Effect Of Ionizing Irradiation And Storage On Mushroom Ultrastructure Ii. The Stipe And The Upper Part Of The Cap Of Agaricus Bisporus (Lge. Imbach), A. Keresztes, E. Kovacs

Food Structure

After having investigated t he ultra structural effects of ionizing irradiation used for shelf -life extension , on the gills of Agaricus bisporus and Pleurotus ostreatus previously , it was of interest to examine how other parts of the fruit body were affected by t he same treatment . Samples were taken from the lower and upper parts of the stipe and from the upper part of t he cap of the control , stored , and irradiate d (2.5 kGy ) t he n stored A. bisporus fruit bodies. Transmission electron microscopy sh owed that irradiated samples generally retained …

Internal Porosity Of Corn Extrudate Air Cell Wall, Samuel H. Cohen, Charles A. Voyle

Food Structure

Transmission electron microscopy was used to observe structures within the air cell wall of a corn-based extrudate. Modified fixation and embedding techniques were employed to obtain optimum thin sections. Photomicrographs from these sections showed minute air cells measuring approximately 5 um or less. The size of air cells might impose a limiting factor on the infusion of particulate materials throughout the extrudate matrix.

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 …

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.

Ultrastructural Study Of Yam Tuber As Related To Postharvest Hardness, L. Sealy, S. Renaudin, D. J. Gallant, B. Bouchet, J. M. Brillouet

Food Structure

Usually, parenchyma cell walls of monocotyledons do not develop secondary walls; however a few days after harvesting, the yam tuber of Dioscorea dumetorum starts to harden. Two or three weeks Iater, hardness is so pronounced that the tubers cannot be eaten, even after a long cooking time.

Cytochemical studies using autofluorescence or some fluorescent dyes, such as phloroglucinol hydrochloride showed that the thin, and flexible cell walls of parenchyma tubers very quickly became fully lignified after harvesting. Ultrastructura 1 stud ies of the hardened ce 11 wa 11 s showed very thick secondary wa 11 s and very deep pit …

Ultrastructural Studies On The Cultivation Processes And Growth And Development Of The Cultivated Mushroom Agaricus Bisporus, D. A. Wood, G. D. Craig, P. T. Atkey, R. J. Newsam, K. Gull

Food Structure

Scanning electron microscopy (SEM) , transmission electron microscopy and light microscopy have been used to study various processes in the cultivation of the edible mushroom Agaricus bisporus . Mushrooms are cultured on composted wheat straw. The microbial degradation processes during composting have been visualised by TEM and SEM and correlated with microbiological studies . Various modes of attack by the microorganisms on the plant cell walls can be seen. Most rapid degradation occurred on the cuticle and phloem and spread to other cell types. Microbial attack was found to be nonuniform between tissue types and individual cells. The mycelium of …

Relation Between Microstructure, Destabilization Phenomena And Rheological Properties Of Whippable Emulsions, W. Buchheim, N. M. Barfod, N. Krog

Food Structure

The structure of spray-dried whippable emulsions (toppings) containing different types of lipid surfactants, was investigated by electron microscopy using the freeze-fracture technique. The size distribution of the lipid particles within the powders varied with the type of the surfactant used. After reconstitution of the topping powders in water. a strong destabilization phenomenon took place to an extent depending on the type of the surfactant. Simultaneously a crystallization of coalesced lipid particles occurred along with an increase in viscosity of the emulsions. The degree of crystallization was measured by p-NMR. It has been concluded that these phenomena are closely related to …

Effects Of Emulsifying Agents On The Microstructure And Other Characteristics Of Process Cheese - A Review, Marijana Caric, Miroslav Gantar, Miloslav Kalab

Food Structure

Sodium phosphates , polyphosphates, and citrates are melting salts (emulsifying agents) most commonly used in the manufacture of process cheese either alone or in mixtures . Their role during processing is to sequester calcium in the natural cheese, to solubilize protein and increase its hydration and swelling, to facilitate emul sification of fat , and to adjust and stabilize pH.

Changes taking place in natural cheese during processing can be studied by microscopy. Micrographs demonstrating the emulsification of fat , presence of salt crystals, and partial solubilization of protein in labo ratory- made and commercial process cheeses have been used …

Microstructural Changes In Winged Bean And Soybean During Fermentation Into Miso, K. Saio, H. Suzuki, T. Kobayashi, M. Namikawa

Food Structure

Miso was prepared from winged bean, being substituted for soybean. Microstructural changes of winged bean miso at various stages of the manufacturing processes were studied by means of light and transmission electron microscopies. Soybean was also studied for comparison.

After steaming , winged bean and soybean cells were shrunken and intracellular spaces enlarged and cell wall structure was degraded, showing layered structures and aggregated lumps in intraspaces between cell walls during fermentation into misc . At the end of the fermentation , the PAS reaction with cell walls almost disappeared. Surprisingly the thick cel l walls of winged bean degraded …

Microstructure Of Set-Style Yoghurt Manufactured From Cow's Milk Fortified By Various Methods, A. Y. Tamime, M. Kalab, G. Davies

Food Structure

Five different batches of skim milk were prepared and fortified by the addition of skim milk powder (SMP) or sodium caseinate (Na-cn) or by concentration using a vacuum evaporator (EV), ultrafiltration (UF), or reverse osmosis (RO) to contain similar levels of protein (5.0-5.5%). Yoghurts were made by inoculating the milks with one of 3 commercial yoghurt starter cultures and by incubating the mixes at 42°C for 2.5 h. The following factors were found in this study to affect firmness of the yoghurts: (a) Lactic acid production (acidity) - Yoghurts containing 1.02% of lactic acid or more (pH 4.54 or less) …