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Changes In The Microstructure Of A Comminuted Meat System During Heating, Peter A. Koolmees, Gerrit Wijngaards, Monique H.G. Tersteeg, Jan G. Van Logtestijn Jan 1993

Changes In The Microstructure Of A Comminuted Meat System During Heating, Peter A. Koolmees, Gerrit Wijngaards, Monique H.G. Tersteeg, Jan G. Van Logtestijn

Food Structure

As part of a series of experiments on heating of a comminuted meat system , image analyses were conducted to quantify microstructural changes that could be visualized by light microscopy. Three different batches of comminuted meat were investigated. Two batches (A and B) were prepared without polyphosphate; one of these (B) was deliberately overchopped. One batch containing 0. I% polyphosphate was prepared (C). All batches were heated at I I different temperatures ranging from 40 to 115 °C. The microstructure of the three types of meat batte rs at the end of the com minu tion process differed. These types of ...


Critical Point Drier As A Source Of Contamination In Food Samples Prepared For Scanning Electron Microscopy, Gisele Larocque, A. F. Yang Jan 1993

Critical Point Drier As A Source Of Contamination In Food Samples Prepared For Scanning Electron Microscopy, Gisele Larocque, A. F. Yang

Food Structure

A valve in a critical-point drier regulating the flow of liquid carbon dioxide was found to be the source of minute metal particles which contaminated the fragments resulting from freeze-fracturing of food samples.


Lactose Crystallization In Spray-Dried Milk Powders Exposed To Isobutanol, Carlos A. Aguilar, Gregory R. Ziegler Jan 1993

Lactose Crystallization In Spray-Dried Milk Powders Exposed To Isobutanol, Carlos A. Aguilar, Gregory R. Ziegler

Food Structure

A study was undertaken to establish whether suspension of dry milk powder in isobutanol and 1-octanol during particle size analysis and preparation for scanning electron microscopy introduced artifacts. The median , volume-based diameter, d[v, 0.5], of spray-dried milk powders containing 27-67% lactose changed over time of exposure to isobutanol. No changes in median diameter were observed when powders were exposed to 1-octanol. Changes in particle si ze resulted from solubilization of amorphous lactose and/or recrystallization of lactose on the particle surface. Both a- and ,6 -lactose were formed during contact with isobutanol as indicated by X-ray diffraction and ...


The Surface Coverage Of Fat On Food Powders Analyzed By Esca (Electron Spectroscopy For Chemical Analysis), Pia Faldt, Bjorn Bergenstahl, Gilbert Carlsson Jan 1993

The Surface Coverage Of Fat On Food Powders Analyzed By Esca (Electron Spectroscopy For Chemical Analysis), Pia Faldt, Bjorn Bergenstahl, Gilbert Carlsson

Food Structure

ES.A (electron spectroscopy for chemical analysis) was used to estimate the fat coverage on different spray-dried food powder surfaces. The method presented here represents a new way of estimating the actual surface coverage of fat on a food powder. The ESCAmethod is illustrated with three different series of experimen ts. The results obtained with the ESCA-technique are combined with the results obtained from the conventional free fat extraction technique for different spray-dried powders.

In the first series , emulsion s containing different ratios of protein to fat were spray-dried. An increase in the amount of fat in the emulsion gives ...


High-Resolution Scanning Electron Microscopy Of Milk Products: A New Sample Preparation Procedure, William R. Mcmanus, Donald J. Mcmahon, Craig J. Oberg Jan 1993

High-Resolution Scanning Electron Microscopy Of Milk Products: A New Sample Preparation Procedure, William R. Mcmanus, Donald J. Mcmahon, Craig J. Oberg

Food Structure

A metal-impregnation technique (tannin-ferrocyanide- osmium tetroxide) and thin metal coating imparted excellent preservation , and electric and thermal properties to milk products for scanning electron microscopy, resulting in high- resolution images. Three nanometer resolution was obtained, with minimal edge effects, charging , thermal drift, and decoration. Samples were fixed in 2% gluta raldehyde, cryoprotected in 70% ethanol, and cryofractured, exposing internal structure. Fat was extracted with Freon 113 and the sample were metal -impregnated with 1.0% osmium tetroxide and 1.5% potassium ferrocyanide, reduced with 1% hydroquinone, dried using !he critical-point drying melhod , and ion beam sputter-coated with 2-5 nm of ...


A Tutorial And Comprehensive Bibliography On The Identification Of Foreign Bodies Found In Food, D. F. Lewis Jan 1993

A Tutorial And Comprehensive Bibliography On The Identification Of Foreign Bodies Found In Food, D. F. Lewis

Food Structure

The paper presents a philosophical approach to the investigation of foreign body incidents in food. The suggested procedure has similarities with "key" procedures used for taxonomy. However, the wide diversity of materials encountered and the need to determine something of the history of the offending item demands modifications to this process. The categorisation may be made on instinct or experience, and appropriate confirmatory tests will be applied in the light of the initial categorisation. Cardinal rules are proposed: firstly , the receipt of the items should be well documented; and secondly, the initial observations should be as non-destructive as possible. The ...


Structure And Function Of Food Products: A Review, I. Heertje Jan 1993

Structure And Function Of Food Products: A Review, I. Heertje

Food Structure

A proper understanding of the behavior of food products requires knowledge of its structure, i.e., the spatial arrangement of the various structural elements and their interactions. The structure can properly be studied by visual observation techniques. In products such as fat spreads, creams, dressings, cheese, bread , milk , yoghurt , whipped cream, and ice cream , different structural elements can be distinguished. A number of those elements a re discussed, viz. , water droplets, oil droplets, gas cell s, particles, fat crystals and strand s. In addition examples of interactions between structural element s are presented, viz., oil droplets/matrix, protein/ protein, protein ...


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 Jan 1993

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 than ...


Age Related Changes In The Microstructure Of Mozzarella Cheese, L. J. Kiely, P. S. Kindstedt, G. M. Hendricks, J. E. Levis, J. J. Yun, D. M. Barbano Jan 1993

Age Related Changes In The Microstructure Of Mozzarella Cheese, L. J. Kiely, P. S. Kindstedt, G. M. Hendricks, J. E. Levis, J. J. Yun, D. M. Barbano

Food Structure

Changes that occurred in the microstructure of low-moisture, part skim Mozzarella made with a mixed starter consisting of Streptococcus salivarius ssp. thermophilus and Lacwbacillus delbrueckii ssp. bulgaricus and coagulated with fermentation -produced chymosin , were examined during 50 days of ripening at 4 °C. Im mediately after manufacture (day 3), a homogeneous and continuous phase of amorphous paracasein represented a three-dimensional protein network in the cheese. A large number of irregularly shaped and sized microcavi ties were present. During 50 days of aging , an increase in the porosity of the defatted paracasein matrix was apparent. These changes were coincidental with a ...


Interfacial Viscoelasticity In Emulsions And Foams, E. H. Lucassen-Reynders Jan 1993

Interfacial Viscoelasticity In Emulsions And Foams, E. H. Lucassen-Reynders

Food Structure

Both the generation and the stability of emulsions and foams depend on interfacial properties induced by adsorbed surfactants. The essential function of surfactants during emulsification and foaming is not that they reduce the equilibrium interfacial tension, but they impart specific dynamic properties to the interface. A surfactant- covered interface behaves as a two-dimensional body with its own elasticity and viscosity, which a re related to the non-equilibrium values of the interfacial tension. Such viscoelasticity is a significant factor in any liquid flow near the interface, and in the stability of the thin films separating emulsion drops or foam bubbles. Numerically ...


Liquid Holding Capacity And Structural Changes During Heating Of Fish Muscle: Cod (Gadus Morhua L.) And Salmon (Salmo Salar), Ragni Ofstad, Siw Kidman, Reidar Myklebust, Anne-Marie Hermansson Jan 1993

Liquid Holding Capacity And Structural Changes During Heating Of Fish Muscle: Cod (Gadus Morhua L.) And Salmon (Salmo Salar), Ragni Ofstad, Siw Kidman, Reidar Myklebust, Anne-Marie Hermansson

Food Structure

The loss of water and fat in cod and salmon muscle was studied as a function of heating temperature from 5-70 C. The liquid-holding capacity was measured by a low speed centrifugation net test leading to the separation of released liquid. To obtain a better understanding of the liquid-holding properties, the microscopic changes of the samples were evaluated by light microscopy. Two different preparation techniques were used . Cod lost twice as much water as salmon upon beating. After an initial delay , the water loss increased at 20-35°C, attained a maximum at 45-50°C, and thereafter decreased in both fish ...


Luminescence Techniques To Identify The Treatment Of Foods By Ionizing Radiation, G. A. Schreiber, B. Ziegelmann, G. Quitzsch, N. Helle, K. W. Bogl Jan 1993

Luminescence Techniques To Identify The Treatment Of Foods By Ionizing Radiation, G. A. Schreiber, B. Ziegelmann, G. Quitzsch, N. Helle, K. W. Bogl

Food Structure

About a decade ago two luminescence techniques, thermoluminescence (TL) and chemiluminescence (CL), were first described as methods for the detection of irradiated spices. It has now been established that the CL method can be used to screen only certain foodstuffs for irradiation. The TL method, instead, has been developed for clear identification of foods irradiated with at least 1 kGy and contaminated by minerals. The method is therefore suitable for a wide range of foodstuffs and it has been applied by laboratories for routine control. The latest findings prove that even irradiation with very low doses used to inhibit the ...


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 Jan 1992

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 ...


Microstructure And Texture Of Khoa, G. R. Patil, A. A. Patel, Paula Allan-Wojtas, Miloslav Kalab Jan 1992

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 ...


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 Jan 1992

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 ...


Effect Of Chemical Modifications On The Stability, Texture And Microstructure Of Cooked Meat Batters, Andre Gordon, Shai Barbut Jan 1992

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 ...


A Low-Temperature Scanning Electron Microscopy Study Of Ice Cream. I Techniques And General Microstructure, K. B. Caldwell, H. D. Goff, D. W. Stanley Jan 1992

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 ...


Computer Modeling: The Adjunct Micro Technique For Lipids, J. W. Hagemann, J. A. Rothfus Jan 1992

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 ...


Distribution Of Aromatic Compounds In Coastal Bermudagrass Cell Walls Using Ultraviolet Absorption Scanning Microspectrophotometry, Nancy P. Ames, Roy D. Hartley, Danny E. Akin Jan 1992

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 the same ...


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 Jan 1992

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.


Structure Of Margarines Made With Low Erucic Acid Rapeseed Oil, J. Hojerova, S. Schmidt, J. Krempasky Jan 1992

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 ...


Effect Of Lactose And Protein On The Microstructure Of Dried Milk, V. V. Mistry, H. N. Hassan, D. J. Robison Jan 1992

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 ...


Image Analysis To Determine Intramuscular Fat In Muscle, T. Ishii, R. G. Cassens, K. K. Scheller, S. C. Arp, D. M. Schaefer Jan 1992

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.


Characterization Of The Pore Structure Of Starch Based Food Materials, Z. Hicsasmaz, J. T. Clayton Jan 1992

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 ...


Functional Properties And Microstructure Of Chicken Breast Salt Soluble Protein Gels As Influenced By Ph And Temperature, S. F. Wang, D. M. Smith Jan 1992

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 ...


Scanning Electron Microscopy Studies Of A Typical Spanish Confectionery Product: "Xixona Turron", M. A. Lluch, M. J. Galotto, A. Chiralt Jan 1992

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 the ...


Cryo-Scanning Electron Microscopy Investigation Of The Texture Of Cooked Potatoes, J. T. Van Marle, A. C.M. Clerkx, A. Boekestein Jan 1992

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 mealy potatoes , it ...


Microstructural Differences Among Adzuki Bean (Vigna Angularis) Cultivars, Anup Engquist, Barry G. Swanson Jan 1992

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 four ...


Light Microscopy Measurements Of Ice Recrystallization In Frozen Corn Starch Pastes Using Isothermal Freeze Fixation, C. Ferrero, M. N. Martino, N. E. Zaritzky Jan 1992

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 ...


Ultrastructural Changes In Cherimoya Fruit Injured By Chilling, Margarita Gutierrez, Maria Del Mar Sola, Luis Pascual, Maria Isabel Rodriguez-Garcia, Alberto M. Vargas Jan 1992

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 of chloroplasts ...