Life Sciences Commons^™

A Low-Temperature Scanning Electron Microscopy Study Of Ice Cream. I Techniques And General Microstructure, K. B. Caldwell, H. D. Goff, D. W. Stanley

Food Structure

The objective of this study was to investigate techniques suitable for viewing the microstructure of ice cream in the frozen and fully hydrated state using low temperature scanning electron microscopy (L T-SEM), and to examine the microstructure of the frozen product. lee cream bad four distinct structural phases: ice crystals, air bubbles, fat globules and serum. Air bubbles, 10 to 60 ~-tm in diameter, were lined with fat globules, 0.5 to 2.5 J.tnl in diameter. Ice cry stals with a mean di ameter of 40 J.Lffi showed a characteri stic reticulat e structure after sublimation. The appearance of the ice …

A Low-Temperature Scanning Electron Microscopy Study Of Ice Cream. Ii. Influence Of Selected Ingredients And Processes, K. B. Caldwell, H. D. Goff, D. W. Stanley

Food Structure

The objective of this study was to examine the influence of processing parameters, viz., incorporation of polysaccharide stabilizers, freezing rates, and storage times and temperatures on the microstructure of ice cream. As the freezing rate was reduced, ice crystals and air bubbles increased in size. However, quenchfreezing also contributed to poor texture; thus an optimum freezing rate exists for the production of suitably- sized ice crystals and texture in ice cream. Model systems of polysaccharide stabilizer solutions were seen to have a characteristic network structure when quenchfrozen which was altered by the addition of sucrose. Stabilized ice cream initially had …

A Moving Optical Fibre Technique For Structure Analysis Of Heterogenous Products: Application To The Determination Of The Bubble-Size Distribution In Liquid Foams, C. G. J. Bisperink, J. C. Akkerman, A. Prins, A. D. Ronteltap

Food Structure

The bubble-size distribution in liquid foams measured as a function of time can be used to distinguish between the physical processes that determine the breakdown of foams. A new method based on an optical fibre technique was developed to measure various foam characteristics e.g. the rate of drainage, the rate of foam collapse, the change in gas fraction, interbubble gas diffusion (disproportionation) and the evolution of the bubble - size distribution during the ageing of the foam. The method consists of an optical sensor that can distinguish between phases with distinct refractive indexes as are found in liquid foams.

Cryo-Scanning Electron Microscopy Investigation Of The Texture Of Cooked Potatoes, J. T. Van Marle, A. C.M. Clerkx, A. Boekestein

Food Structure

The texture of steam-cooked potatoes was investigated by examining the fracture planes of four different cultivars, using cryo-scanning electron microscopy (cryo-SEM), which yielded a good preservation of the hydrated structures in potato tissue . For all cultivars , fracturing after steam -cooking took place between cells preferentially alongside the cell walls. However, textural difference appeared from the degree of intercellular contact, the cell shape and the appearance of cell surfaces. Cells in the fracture planes of firm potatoes had large intercellular contacts. In this case, most of the cells were flat and cell surfaces showed folds and cracks . For …

Relating Spectral Observations Of The Agricultural Landscape To Crop Yield, Craig L. Wiegand, Arthur J. Richardson

Food Structure

Remote sensing and microscopy share several common concerns including wavelength and sensor selection, signal processing, and image analysis. For crop yield assessments, multispectral observations are acquired photographically, videographically, or with opticalmechanical scanners from aircraft and spacecraft. Sensors are chosen at wavelengths of high atmospheric transmission and maximum contrast between the soil background and the vegetation growing out of it. Vegetation indices have been developed that maximize the information about the photosynthetic size of the vegetation in the landscape and, hence, about crop stresses and yield . Three such indices that reduce the multispectral observations to a single numerical index are …

Effect Of Draw Ph On The Development Of Curd Structure During The Manufacture Of Mozzarella Cheese, L. J. Kiely, P. S. Kindstedt, G. M. Hendricks, J. E. Levis, J. J. Yun, D. M. Barbano

Food Structure

The impact of varying the pH of whey at whey drainage (5.9, 6.15 or 6.4) on the development of curd structure during the manufacture of Mozzarella cheese was investigated using scanning electron microscopy. Dramatic changes in curd structure were apparent with stage of manufacture , in particular the stretching step which aligned the protein fibers.

Of additional interest is the effect of draw pH on the structure of curd at whey drainage. When whey was drained at pH 6.4, an open poorly fused network of paracasein particles was observed in the cheese curd. Jn contrast, lowering the draw pH (6.15 …

Ultrastructural Changes In Cherimoya Fruit Injured By Chilling, Margarita Gutierrez, Maria Del Mar Sola, Luis Pascual, Maria Isabel Rodriguez-Garcia, Alberto M. Vargas

Food Structure

Cherimoya (Annona cherimola Mill.) is an important fruit crop that is grown in the South of Spain. Ultrastructural modifications of cherimoya fruit were studied after low-temperature storage. When cherimoya was stored at 4 oc for 6 days, the starch grains did not suffer degradation and the cell walls remained intact. The membrane systems were severely damaged , result ing in a loss of cell compartmentalization. Cherimoya rewarmed to 22 0 C after 9 days of low temperature storage is not able to recover , showing the irreversibility of the ultra structural changes. In addition, disorgani zation of the internal lamella …

The Cellular Structure Of Selected Apple Varieties, K. G. Lapsley, F. E. Escher, E. Hoehn

Food Structure

Apple cultivars (Sauergrauech, Klarapfel, James Grieve, Granny Smith, Mcintosh, Robinette) which had different textures based on sensory and instrumental analysis (particularly in firmness and mealiness) were examined by conventional scanning electron microscopy (SEM), cold-stage SEM (cryoSEM) and confocal scanning laser microscopy (CSLM) using various preparative procedures. Advantages, lim itations and artifacts of each technique are discussed.

SEM with glutaraldehyde-fixation and criticalpoint- drying produced minimal tissue distortion and the fracture pattern and appearance of mealy versus non mealy tissue was different. Freeze-drying unfixed tissue caused cell collapse and firm versus soft varieties could not be differentiated. Freeze-fracturing and cryoSEM of apple …

Thermal Processing Effects On Rice Characteristics, Shuh-Ming Chang, Hsiu-Chen Yang

Food Structure

Whole kernels of four cultivars of milled rice were treated under different conditions according to our traditional methods such as boiling, steaming, autoclaving or roasting with sand. During the vari ous processing conditions, the moisture contents of the kernel , heating temperatures, pressures and heating times were varied. In this paper, the physicochemical properties of those processed samples were investigated and compared.

Based on degree of gelatinization , water absorption index , water solubility index , swelling power, viscoamylograms and X-ray diffraction patterns, the propenies of waxy rice samples arc different from that of non -waxy rice samples. They are …

Distribution Of Aromatic Compounds In Coastal Bermudagrass Cell Walls Using Ultraviolet Absorption Scanning Microspectrophotometry, Nancy P. Ames, Roy D. Hartley, Danny E. Akin

Food Structure

The distribution of aromatic constituents, including lignin , in the leaf cell walls of "Coastal" hermudagrass (Cynodon dacrylon (L.) Pers.) was investigated using scanning ultraviolet (UV) microspectrophotometry. Leaf blade sections and individual tissue types were scanned at three wavelengths representing the absorbance maxima (318, 287 and 250 nm) of aromatic constituents present in bermudagrass leaves. The measured absorbance data were printed in a geometric arrangement to produce an image of the distribution and amount of aromatic constituents among and within cell wall types which vary in digestibility . Differences in absorbance were observed among cell wall types, among walls of …

Molecular Strategies To Improve Protein Quality And Reduce Flatulence In Legumes: A Review, Benito O. De Lumen

Food Structure

The application of recombinant DNA and related techniques to plants opened up the potential to improve agronomic characters. food processing traits and food quality properties of plants as food sources. This review focuses on molecular approaches to improving the protein quality and reducing flatulence in beans. Much is now known about the regulation of seed-specific expression and organization of seed storage protein genes. Several attempts have been made to increase the methionine content of tobacco seeds using heterologous seed protein genes from peas, common bean and soybean. Such techniques could also be used to modify lysine, tryptophan and threonine contents …

Effects Of Processing On The Microstructure Of Oat (Avena Sativa) Bran Concentrate And The Physicochemical Properties Of Isolated B-Glucans, K. Autio, Y. Malkki, T. Virtanen

Food Structure

Fluorescence microscopy was used to study the microstructure of oat cell walls during concentration of oat bran and isolation of ,B-glucans. The bran concentrate separated from c.v. Nasta contained mainly the aleurone and subaleurone endosperm layers, whereas that separated from a commercial bran mixture contained more endosperm . In contrast to Nasta, the commercial bran mixture contained ,B-glucan degrading enzymes, which survived the ,B-glucan isolation procedure. In the presence of enzymes, the solubility and yield of ,B-glucans improved but the viscosity decreased when it was measured at the same ,B-glucan concentration. For inactivation of the enzymes, 80% ethanol at 78 …

Structure Of Margarines Made With Low Erucic Acid Rapeseed Oil, J. Hojerova, S. Schmidt, J. Krempasky

Food Structure

Margarine based on hydrogenated low erucic acid rapeseed oil shows a strong tendency to produce an unacceptable grainy structure. This is caused by rapid transition of the B-form into the B-form of fat crystals. Sorbitan esters, monoacylglycerols, and a blend of acylglycerols were investigated as possible B-stabilizers. Polymorphic transitions were evaluated by visual assessment, examination by polarized light microscopy, and x-ray diffraction analysis in margarines prepared on a laboratory scale and containing varying amounts of stabilizers. The evaluation was extended over a 7-week period of storage at 10 C. Sorbitan esters of fatty acids were found to be the most …

Microstructural Differences Among Adzuki Bean (Vigna Angularis) Cultivars, Anup Engquist, Barry G. Swanson

Food Structure

Scanning electron microscopy (SEM) was used to study microstructural differences among five adzuki bean cultivars: Erimo, Express, Hatsune, Takara and VBSC. Seed coat surfaces showed different patterns of cracks, pits and deposits . Cross-sections of the seed coats revealed well organized layers of elongated palisade cells followed by many layers of amorphous parenchyma cells. Typical sub-epidermal layers of organized columnar, hour-glass cells were characteristica11y absent in the five cultivars of adzuki beans. The cross-sections of the cotyledons revealed intercellular materials between storage cells. Storage cells in Hatsune cultivar were loosely packed with many intercellular spaces as compared to the other …

Influence Of Addition Of Polyols And Food Emulsifiers On The Retrogradation Rate Of Starch, M. Muira, A. Nishimura, K. Katsuta

Food Structure

The influence of polyols and emulsifiers on hardening of non-glutinous rice starch gels has been investigated. The polyols and emulsifiers were added at concentrations of 6% (w/w) and 0.2% (w/w), respectively , to starch gels (starch content, 30%). The hardening rate and the initial viscoelastic values of gels were computed by analyzing static linear viscoelastic parameters (creep compliance) of the gels stored at 0 C for up to 3,000 minutes.

Hardening of gels, i.e., retrogradation of starch, could be described by a first order kinetic equation. Polyols prevented the retrogradation of starch, and formed rigid and stable gel matrices. Emulsifiers …

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 …

Image Analysis To Determine Intramuscular Fat In Muscle, T. Ishii, R. G. Cassens, K. K. Scheller, S. C. Arp, D. M. Schaefer

Food Structure

The area of intramuscular fat in Holstein steer longissimus was determined using an image analyzing system. Slaughter weights of 500, 636 and 773 kg differed (p < 0.05) for intramuscular fat area, marbling score, and ether extractable lipid . Repeated measurements of intramuscular fat area in a given section showed high accuracy . However, comparing two sections from the same sample, there was often a large difference in fat content between the sections. Fat content determined by the imaging system was correlated significantl y with marbling score (r = 0.49) and ether extractable lipid (r = 0.34). Sampling is critical, and in order to obtain a high correlation several samples would be required from each muscle.

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 …

Effect Of Lactose And Protein On The Microstructure Of Dried Milk, V. V. Mistry, H. N. Hassan, D. J. Robison

Food Structure

Skim milk of approximately 3% total protein was ultrafiltered to 16.2% protein and 4.1 % lactose, and then diafiltered to reduce lactose to 2.1% and 0.9%. Total protein con ten t was maintained at approximately 17%. A ponion of the skim milk was condensed in a rising film evaporator to 14.7% protein and 15.7% lactose . All concentrates were spray dried at 120 to 125 °C inlet air temperature and 75 to 80 C outlet temperature using a rotary atomizer in a pilot plant spray dryer . Moisture content of the powders were 4.7 to 6.3% and lactose content ranged …

Computer Modeling: The Adjunct Micro Technique For Lipids, J. W. Hagemann, J. A. Rothfus

Food Structure

Chemistry by computer provides access to microsystem information not readily achieved by other means. Simple computational analysis of saturated triglyceride polymorphism by molecular mechanics within constraints provided by X-ray data show that polymethylene interactions determine hydrocarbon crystal properties when they account for more than 60 percent of the total molecular interaction energy. Modeling predicts multiple , nearly equivalent, a -form triglycerides and a -form character in liquid near-crystalline triglycerides. Symmetrical molecules pack better than asymmetric molecules in a-form configurations and transform readily to 13'forms if activated sufficiently to disrupt lateral chain interaction and allow dimensional displacements during transformation. The formation …

A Moving Optical Fibre Technique For Structure Analysis Of Heterogeneous Products: Application To Different Foodstuffs, J. C. Akkerman, C. G. J. Bisperink, A. D. Ronteltap

Food Structure

The macro structure of many soft heterogeneous products can be studied by a moving optical fibre technique . The method i s based upon an optical sensor that penetrates into the heterogeneous medium. The optical sensor discriminates between materials differing in refractive index or in scattering properties. Coupling of the signal of the optical sensor to its position reveals the spatial distribution of the materials in the product. Applications shown include bread, soft ice-cream, chocolate mousse and draining curd. The major advantages of the method are its speed and ease; moreover, the sample is hardly disturbed by the sensor. The …

Characterization Of The Pore Structure Of Starch Based Food Materials, Z. Hicsasmaz, J. T. Clayton

Food Structure

Macroscopic pore structure parameters (bulk density, true density and porosity) and microscopic pore structure parameters (percentage closed pore volume and pore size distribution) for a highly expanded type (Wonder White Sandwich Bread) and a relatively compact type (Chessmen Butter Cookies) starch based food material were determined and their pore structures were compared. Bulk density determined by solid displacement and true density determined by pycnometry yielded porosity measurement s o f 0.9 for bread and 0.6 for cookies. Percentage closed pore volume calculated by comparing the true density of porous samples of bread and cookies with the true density of !heir …

Effect Of Chemical Modifications On The Stability, Texture And Microstructure Of Cooked Meat Batters, Andre Gordon, Shai Barbut

Food Structure

The effects of five chemical agents on the stability, texture and microstructure of cooked comminuted meat batters were studied. B-mercaptoethanol (/3-ME), hydrogen peroxide (H20~, ethylenediaminetetraacetic acid (EDT A), urea, and polyoxyetbylene sorbitan monooleate (fween 80) were used. The reduction of disulphide bonds by 8-ME or the oxidation of free sulphydryls by H20 2 prior to cooking did not affect liquid and fat losses during cooking as compared to the control (2.5% NaCI). However, texture profile analysis (fPA) showed that treatment with H20 2 resulted in a harder, more cohesive product than the control and ,8-ME treatments because a more fine-stranded, …

Microstructure And Texture Of Khoa, G. R. Patil, A. A. Patel, Paula Allan-Wojtas, Miloslav Kalab

Food Structure

Khoa, a partially dehydrated milk product indigenous to India, was prepared from buffalo milk by boiling it vigorously in an open pan and reducing its volume to approximately 25% within 30 min. The hot semi-solid product (Khoa pat) was held at 20•c for 3 h (fresh, cooled Khoa) or 48 h (swred Khoa); the products were either worked with a pestle in a mortar for 5 min or were left without working.

Structural features of Khoa were studied by light microscopy and electron microscopy. Freshly prepared coo led Khoa had a granular structure consisting of protein granules several hundred micrometers …

Effect Of Ionizing Y-Radiation On Thermoluminescence And Electron Spin Rosonance Intensities In Milk Protein Concentrate Powders, J. Kispeter, L. I. Horvath, L. I. Kiss

Food Structure

Milk protein concentrate powder has found a wide application as a food ingredient. We investigated the effects of ionizing ')'-radiation at doses ranging from 2 to 20 kGy on electron spin resonance and thermoluminescence intensities in samples of milk protein concentrate powder with varying protein contents (36-73 %wt), containing addltional Fe++ ions (12-910 ppm) and stored under different conditions.

Electron spin resonance and thermoluminescence intensities increased unambiguously with absorbed -ydose. Added Fe++ ions showed a quenching effect as measured by both methods. Storage conditions affected strongly the decay of electron spin resonance signal intensity . Lineshape analysis of thermoluminescence curves …

Scanning Electron Microscopy Studies Of A Typical Spanish Confectionery Product: "Xixona Turron", M. A. Lluch, M. J. Galotto, A. Chiralt

Food Structure

The microstructure of "Xixona turron" , a typical Spanish confectionery product, made with toasted almonds, sugar and honey, was elucidated, in order to confirm the nature of those physical changes occurring in its manufacturing process, which has not been previously studied. The effect of the major components of "Xixona turron" (oil, proteins and sugar) on its structural c!Jange was established. The initial oil suspension of sugar syrup drops and proteins undergoes a phase inversion , becoming an oil /water emulsion when hot, and a solid-like structure, when the aqueous sugar continuous phase solidifies at room temperature. In order to determine …

Importance Of Enzymes To Value-Added Quality Of Foods, J. R. Whitaker

Food Structure

New uses of enzymes are of major importance for value-added quality of foods. At the production and postharvest handling levels, enzymes associated with maturation , color , texture, flavor and nutritional changes are important. Recent examples are discussed which include longer storage prior to initiation of ripening , deletion or control of genes that result in softening1 browning and other quality defects and the enhancement of genes that improve the nutritional quality of foods. At the processing level, new uses of enzymes are described to change the properties of proteins and lipids , to eliminate off-flavor in beers and sterilized …

Light Microscopy Measurements Of Ice Recrystallization In Frozen Corn Starch Pastes Using Isothermal Freeze Fixation, C. Ferrero, M. N. Martino, N. E. Zaritzky

Food Structure

Isothermal freeze fixation was used to analyze ice recrystallization by light microscopy in a 10 % (W/W) frozen corn starch paste during storage at temperatures in the range of -5 to -20 °C.

Different formulations were tested in order to obtain a suitable fixative for this method of indirect observation of the ice crystals. A solution of formaldehyde, ethanol and water (10:45:45 V:V) was selected because it minimized substitution-induced distortion and contraction of the matrix. The diffusion coefficients of the selected fixative in the frozen system were measured at different temperatures in conditions of unidirectional mass transfer in a semi …

Scanning Electron Microscopy And Ultraviolet Absorption Microspectrophotometry Of Plant Cell Types Of Different Biodegradabilities, D. E. Akin, L. L. Rigsby

Food Structure

Phenolic components within cell walls are the greatest limitation to biodegradation of plants, but the location and types of compounds within specific walls are poorly understood . Leaf blades of warm-season (Coastal and Coastcross-1 bermuda grasses and sudangrass) and cool-season grasses (orchardgrass and tall fescue) and leaflets of legumes (alfalfa and lespedeza) were evaluated before and after incubation with rumen microorganisms for 7 days to determine cell types and wall structures most resistant to biodegradation. UV absorption microspectrophotometry was used to characterize aromatics within selected undegraded cell types, which had been shown in digestion studies to vary in biodegradability, from …

Functional Properties And Microstructure Of Chicken Breast Salt Soluble Protein Gels As Influenced By Ph And Temperature, S. F. Wang, D. M. Smith

Food Structure

The effects of different pH's (4 .5 , 5.5, 6.5 and 7.5) and temperatures (30-80 •c) on the functional properties and microstructure of chicken breast salt soluble protein (SSP) in 0.6 M NaCI were investigated. Protein solubility decreased from 98% at pH 6.5 to less than I% at pH 4.3 and below. Salt soluble protein at pH 4.5 produced a discontinuous gel which could not be measured by back extrusion and had an expressible moisture above 80% at all heating temperatures . Aggregated globular microstructures were observed at pH 4.5 by scanning electron microscopy (SEM). Thin-sectioned images as seen by …