Life Sciences Commons^™

The Observation Of The Displacement Of Emulsifiers By Confocal Scanning Laser Microscopy, I. Heertje, J. Nederlof, H.A.C.M. Hendrickx, E. H. Lucassen-Reynders

Food Structure

The stability of food emulsions is an important aspect of the processing and the shelf life of many food systems. In order to control the stability, knowledge of the competitive adsorption of different emulsifiers is required. Current methods to study the displacement of emulsifiers from interfaces are rather laborious. A new method has been developed which is based on the observation of a planar interface between oil and water by fluorescent Confocal Scanning Laser Microscopy (CSLM). The displacement of fluorescein isothio-cyanate- labeled sodium caseinate by monoacylglycerols and proteins has been studied. Quantitative information on the competitive adsorption as a function …

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 paste heated …

Emulsifiers As Additives In Fats: Effect On Polymorphic Transformations And Crystal Properties Of Fatty Acids And Triglycerides, J. Aronhime, S. Sarig, N. Garti

Food Structure

The role of emulsifiers in polymorphic transformations of fats and fatty acids is treated in this paper. Their effect as crystal modifiers in solution-mediated transformations (in fatty acids) is compared to that of a dynamic controller of polymorphic transformations in triglycerides. The importance of chemical structure both in the hydrophilic and in the hydrophobic moieties of the emulsifier for an inhibitory effect on phase transitions has been emphasized. The emulsifier solubility and crystallization behavior in different solvents are probably the main factors affecting its ability to interfere with the kinetics of solution-mediated transformations. On the other hand, certain requirements for …

Gelatin Of Myosin Filament Under High Hydrostatic Pressure, Katsuhiro Yamamoto, Takeo Miura, Tsutomu Yasui

Food Structure

Gelation of myosin filaments under high hydrostatic pressure was investigated. At room temperature myosin filaments in 0.1 M KCl and 20 mM phosphate, pH 6.0, formed gels at 280 MPa and a protein concentration above 2 mg/ml or at 210 MPa and 3 mg/ml. However, no pressure-induced gelation was observed at 140 MPa. The gel strengths of pressure-induced gels were almost proportional to the protein concentration and they were comparable to those of heat-induced gels. The association of myosin filaments and the structural disturbance seemed to coincide with the formation of the gel. The microstructure of the pressure-induced myosin gel …

Crystal Morphology Of Shortenings And Margarines, P. Chawla, J. M. Deman, A. K. Smith

Food Structure

An improved method is proposed for isolation of fat crystals with isobutanol, followed by fixation using osmium tetroxide vapours or cryo-fixation and visualization in the Scanning Electron Microscope (SEM). The cryo-fixation method revealed the presence of well defined needle-shaped or rod-shaped fat crystals. The osmium fixed crystals did not appear as distinct. The crystals existed as single crystals, platelets and spherulites. Polarized light micrographs did not show the details of the crystal morphology that were observed in the SEM.

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 …

The Microstructure Of Raw Meat Batters Prepared With Monovalent And Divalent Chloride Salts, Andre Gordon, Shai Barbut

Food Structure

Cold stage scanning electron microscopy (cryo-SEM), transmission electron microscopy (TEM) and light microscopy (LM) were used to examine the effect of NaCl (2.5%), MgC1₂ , CaC1₂ , KCl, LiCl (calculated ionic strength, IS = 0.43) and 1.5% NaCl (IS = 0.26) on the microstructure of comminuted raw meat batters (fat added) and comminuted meat mixes (no fat added). Cryo-SEM revealed that comminuting the lean meat with different chloride salts resulted in the formation of different types of gel structures. Differences were mainly in gel strand thickness, the degree of interlinking between strands and the size of pores within …

Polymorphism Of Triglycerides A Crystallographic Review, L. Hernqvist

Food Structure

In order to understand I he role of fat in food systems detailed knowledge about the arrangement of triglyceride molecules is useful. The triglyceride molecules in a fat can be packed in alternative ways, each crystal form having different melting points. This phenomenon is called polymorphism.

Based mainly on X-ray studies (single-crystal, powder diffraction , scattering) and Raman spectroscopy the structure of the different polymorphic forms, a, sub-a, P'2. P't and~. are explained. The emphasis is on work done in the author's laboratory.

There is a close relationship between the polymorphic forms which is persistent also in the liquid state …

Particle Characteristics Of Flake-Cut Meat, P. R. Sheard, A. Cousins, P. D. Jolley, C. A. Voyle

Food Structure

The size of flake-cut meat is an Important quality determinant of comminuted meat products which. potentially. depends upon a large number of factors. Temperature and whether or not the meat is pre-broken have a major Influence on the resulting particle size distribution, as does aperture size. Meat flaked at -7'C produced two to three times more flakes than at -3' C. Under some conditions the particles produced were as little as 0.4 mm thick and characteristically were thicker at one end.

High speed photography, used to visualise the cutting action. Indicated that size reduction occurs In a controlled manner providing …

The Role Of The Interfacial Protein Film In Meat Batter Stabilization, A. Gordon, S. Barbut

Food Structure

The microstructure of meat batters made with equal ionic strengths of NaCl, MgC1 2 , CaCl2 and KCl (IS- 0.43) and a reduced-NaCl batter (IS- 0.43) were examined by scanning and transmission electron microscopy. Micrographs revealed that fat globules with smooth and rough protein coats were present in all treatments. The roughly-coated globules were prevalent in the unstable batters. Pores were observed in the interfacial protein film (IPF) surrounding the globul es and were more prevalent in the globules with rough protein coats. Fat was seen to exude from the pores in both types of globules, Fat globules were shown …

Encapsulation Of Viscous High-Fat Foods In Calcium Alginate Gel Tubes At Ambient Temperature, Ivan A. Veliky, Miloslav Kalab

Food Structure

Viscous high-fat foods such as cream, egg yolk, or mayonnaise are co-extruded with a 3% sodium alginate solution from a syringe into a 50 mM calcium chloride solution. The food sample passes through the inner tube of a double needle assembly while the alginate solution is simultaneously extruded through a mantle surrounding the inner needle. As the sodium alginate solution forms a gel on contact with calcium ions, the food sample becomes encapsulated in the calcium alginate gel formed on the surface of the food sample. The encapsulation procedure may be carried out within a temperature range between 0 C …

Simulation Of A Penetrometric Test On Apples Using Voronoi-Delaunay Tessellation, Alain-Claude Roudot, Francois Duprat, Eric Pietri

Food Structure

A penetrometer is very useful for evaluating fruit firmness, but no systematic study yet exists on the physical significance attributed to the curve variations. A tissue model, based on computer graphic methods, allows the simulation of penetrometric tests on apples. There are varying physical factors such as intercellular space, cell arrangement, cell stiffness and tissue cohesion. The real forward limit of the plunger may take, and curve fluctuations are due to the periodic evacuation of those cells. The most influential factor in a penetrometric measurement is individual cell stiffness, its variation with depth can be evaluated with the curve mean …

Development Of Sorghum (Sorghum Bicolor (L.) Moench) Endosperm In Varieties Of Varying Hardness, J. M. Shull, A. Chandrashekar, A. W. Kirleis, G. Ejeta

Food Structure

Factors responsible for grain hardness in sorghum are not well understood. Therefore, a study was undertaken to observe differences in the developmental processes of three sorghum varieties which vary in endosperm texture: hard, intermediate, and soft. Grain samples were collected at 5 day intervals beginning at 5 days after half-bloom (DAHB) until physiological maturity (40 DAHB) and prepared for viewing with scanning electron microscopy and transmission electron microscopy.

Comparisons were made between vitreous and floury endosperm portions of each variety and among the three varieties. The major difference between vitreous and floury endosperm was the degree to which the protein …

Identification And Characterization Of Cocoa Solids And Milk Proteins In Chocolate Using X-Ray Microanalysis, B. E. Brooker

Food Structure

X-ray microanalysis was used to compare the elemental composition of isolated cocoa solids with milk powder. Whereas mllk powder contained similar high levels of calcium and potassium, cocoa sol ids were rich in potassium but contained very small amounts of calcium.

This difference in elemental composition allowed the two populations of particles to be distinguished in digital X-ray maps of frozen and fractured samples of plain , milk and white chocolates examined by cryo-scanning electron microscopy. The size distributions of particles imaged in this way were determined using standard software and were used to distinguish between two white chocolates whose …

An Enzyme/Surfactant Treatment And Filtration Technique For The Retrieval Of Listeria Monocytogenes From Ice Cream Mix, Kelly-Ann Hale, Stephanie Doores, Rosemary A. Walsh

Food Structure

This study combines an enzyme/surfactant treatment with centrifugal ion and prefiltration to solubilize food constituents in a dairy product containing listeria monocytogenes, remove the constituents by a second filtration and examine the isolated bacteria under the scanning electron microscope. Treatment of an ice cream mix with a combined 2% (w/w} trypsin and 2% (w/w) Tween 80 so lution for 20 minutes at 35 °C resulted i n proteolysis of the dairy mix without lysing the bacteria. Centrifugation at 4300 x g for 20 minutes at 5°C concentrated the bacteria in the form of a pellet which was subsequently purified through …

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

Food Structure

Changes in the microstructure of peanut (Arachls ~ L. cv Florunner) cotyledons after roasting at a temperature of 160°C (16 min) were investigated with light and scanning electron microscopy. Major changes included: (1) pitting and pock -marking of the epidermis of the cotyledons caused by the escape of steam and on released during roasting; (2) loss of cellular organization of the cytoplasmic network surrounding the Jipid bodies, protein bodies, and starch grains ; (3) alteration of the structures of cytoplasmic network. lipid bodies, and protein bodies; and (4) heat destruction of some middle lamellae of cell - t o-cell junctions.

Microscopic Measurement Of Apple Bruise, N. K. Kim, Y. C. Hung

Food Structure

Microstructural differences between unbruised and bruised apple tissues were evaluated. Cell connections appeared to be looser in bruised tissue than in unbruised tissue. Bruised tissue exhibited more empty regions which are not occupied by cells than unbruised tissue. Empty reg ions in unbruised and bruised tissues were about 0.7 and 2.4 per mm2, respectively, comprising 0.7% and 2.7% of the respective total volume. Stereology is a body of mathematical methods relating three-dimensional parameters defining a structure to two- dimensional measurements. Two methods based on a stereological principle were also used to quantify the fraction of total volume occupied by cells. …

Scanning Electron Microscopy: Tissue Characteristics And Starch Granule Variations Of Potatoes After Microwave And Conductive Heating, J. Huang, W. M. Hess, D. J. Weber, A. E. Purcell, C. S. Huber

Food Structure

In order to determine cytological effects of microwave heating compared to conductive heating, whole potatoes were heated in a microwave oven in plastic bags for 0.5, 1 and 2 minutes and in boiling water for 5. 10 and 20 minutes. Both heating treatments caused swelling and partial disruption of starch granules. However, as observed with scanning electron microscopy, swelling patterns of starch granules were different in potatoes using the two heating processes. In conductive heating potatoes were heated from the outside to the inside. Microwave heated potatoes were heated fairly uniformly in different regions of tubers. The weight loss of …

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 …

The Role Of Cell Wall Structure In The Hard-To-Cook Phenomenon In Beans (Phaseolus Vulgaris L.), Ilan Shomer, Nachman Paster, Pinhas Lindner, Rosa Vasiliver

Food Structure

Differences in structure, water uptake and efflux of solubles were found between normal and hard-to-cook beans (Phaseolus vulgaris L.) The staining characteristics of hard beans were different from those of the normal in both non-cooked and cooked tissue, especially in the cell walls. The three zones of the cell wall - the middle lamella, the primary and the secondary walls - were found in both normal and hard-to-cook beans. The primary cell wall of both normal and hard beans was partially degraded upon cooking, as seen by bright fields within the fibrillar pattern. The ultrastructure of the non-cooked secondary cell …

The Use Of The Scanning Electron Microscope In Investigating Container Corrosion By Canned Foods And Beverages, E. J. Helwig, H. E. Biber

Food Structure

Over the years the canned food industry has experienced corrosion problems with some foods packed in metal containers. Although most of these are minor, the net e ffect can represent significant financial loss in the industry. It is important to determine the cause of these problems, not only to assign proper responsibility but a lso to avoid recurrence of the probl em in the future. The scanning electron microscope SEM, coupled with energy dispersive x-ray microanalysis, plays an important role in these studies. Stress corrosion cracking in packs of tuna and potatoes, pitting corrosion related to light colored fruits, and …

The Structure-Function Relationship Of Polymeric Sorbents For Colloid Stabilization Of Beer, Gabriela Basarova

Food Structure

This review considers the research relating to the formation of non-biological haze in beer. The basic information regarding mutual interactions of haze-causing substances with precipitating, enzymatic, and adsorptive stabilizers of beer is discu ssed. The main haze-causing compounds in beer are polypeptides and polyphenols. To reduce the levels of these compounds in beer, adsorptive stabilizing agents are usually used during filt ration. Electron microscopy and methods measuring the surface and dimensions of adsorbent particles and the volumes and diameters of their pores make it possible to assess morphological properties and suitability of the stabilizers for beer filtration. Determination of the …

The Adsorption Of Crystalline Fat To The Air-Water Interface Of Whipped Cream, B. E. Brooker

Food Structure

The interfacial structure of air bubbles in normal and defective whipped creams were compared, using freeze fracturing and transmission electron microscopy , in an attempt to understand the underlying mechanism of t he observed gross differences in their whipping times and overruns . In normal whipped creams sparsely distributed fat crystals were found to have penetrated some of the bubbles and were lying in the plane of the air/water interface.

In defective whipped creams , large numbers of needle-like crystals had penetrated the air/water interface of every bubble and, as a consequence, reduced numbers of fat globules were found to …

Fat Polymorphism And Crystal Seeding Effects On Fat Bloom Stability Of Dark Chocolate, T. Koyano, I. Hachiya, K. Sato

Food Structure

The effects of seeding with fine crystal powders on the physical properties of dark chocolate are re viewed in terms of the polymorphism and crystallization behavior of cocoa butter (CBJ and of its major fat constituents. The polymorphic structure of four symmetric mixed acids saturated -oleic-saturated (Sat-0- Sat) triacylglycerols (TAGs I [POP (1 ,3-dipalmitoyl-2- oleoyl-glyceroll ;SOS I 1 ,3-distearoyl-2-oleoyl-glycerol); AOA (1 ,3-diarachidoyl-2-oleoyl-glycerol); and BOB 11 ,3-dibehenoyl-2-oleoyl-glyceroi)J. and of tristearoylglycerol (SSSI are briefly explained. An attempt is made at replacing the currently used tempering meth ~ ad in the chocolate solidification process, by a simple cooling technique using fat seed crystals. …

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 …

Microstructure And Firmness Of Processed Cheese Manufactured From Cheddar Cheese And Skim Milk Powder Cheese Base, A. Y. Tamime, M. Kalab, G. Davies, M. F. Younis

Food Structure

Processed cheese (10 different types) was made from Cheddar cheese and a cheese base produced from reconstituted skim milk powder by blending and melting with commercial emulsifying salts at 9Q<>C. In one experiment, the cheese base was subjected 10 accelerated cheese ripening by added enzyme. The finished products had 50.1- 53.5% total solids, 18.2-19.3% protein, 47.4-49.7% fat in dry matter, and 2.7-3.0% salt in water; pH was 5.3-5.4 after three months of storage at 10 C and 30 C.

The experimental cheeses were markedly firmer than the control cheeses. All processed cheeses exhibited a similar pattern of firmness whereby …

Porosity, Specific Gravity And Air Content In Blue Cheeses, K. M.K. Kebary, H. A. Morris

Food Structure

Porosity and specific gravity were determined in Blue cheeses made from (A) homogenized 14% fat pasteurized cream standardized to 3.9% fat with pasteurized skim milk, (B) homogenized 14% fat raw cream standardized to 3.9% fat with raw skim milk, and (C) pasteurized milk (3.9% fat). There were no significant differences between cheeses made from (A) a nd (B) in porosity and specific gravity. Cheeses made from (A) and (8) had greater porosity, lower specific gravity and more, but smaller holes than cheese made from (C). The negative linear relation ship between porosity and specific gravity, and the insignificant differences in …

The Effect Of Tumbling, Sodium Chloride And Polyphosphates On The Microstructure And Appearance Of Whole-Muscle Processed Meats, P. D. Velinov, M. V. Zhikov, R. G. Cassens

Food Structure

The properties of a whole-muscle processed meat were determined. The complex action of socium chloride, polyphosphates and mechanical agitation caused extraction of myofibrillar protein, swelling of fibers and loss of cross-strations. A new functional ability was found for the extracted proteins to form a fine cover or membrane on the surface of the whole muscle during cooking. These changes produced a product with improved cooking yield and color appearance.

A Method For The Examination Of The Microstructure Of Stabilized Peanut Butter, Clyde T. Young, William E. Schadel

Food Structure

A method for light and scanning electron microscopy of damaged resting peanut seed tissue was adapted as a research tool for evaluating the microstructural features of commercially available stabilized peanut butter. This method was used in the present study to evaluate the degree of homogenization of stabilized peanut butter by examining the spatial relationship which exists among the microstructural features. Light and scanning electron microscopy of three commercially available stabilized peanut butters revealed varying degrees of homogenization of broken cell and tissue fragments, protein bodies, and starch grains within a matrix of stabilized oil.