Life Sciences Commons^™

The Application Of Light And Scanning Electron Microscopy During Flour Milling And Wheat Processing, R. Moss

Food Structure

Light and scanning electron microscopy have been employed as part of an on-going study on the effect of the milling system on flour composition and quality. Examples are given of some areas where microscopy has been particularly useful in understanding the functional changes that take place during milling or the subsequent processing of the flour . The use of heavy reduction roll pressures was shown to modify gluten protein quality as well as produce the desired increase in starch damage. The use of in-line impact machines not only disrupted flaked flour particles but also fragmented wheat germ and allowed it …

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 …

Observations On The Air-Serum Interface Of Milk Foams, B. E. Brooker

Food Structure

A new rapid method for the preparation of milk foams for transmission electron microscopy is described . The air-serum interface of foams made from skimmed milk consists of a uniform electron dense layer (5 nm thick) to which casein micelles become secondarily attached . Changes in bubble volume lead to the formation of folds of excess interfacial material which project into the aqueous phase. Using collapsed bubble ghosts to study the attachment of micelles to the airserum interface it was concluded that neither disulphide bridge formation nor hydrophobic interactions were of major importance. Similar preparations of interfacial material but without …

Rheological And Ultrastructural Studies Of Wheat Kernel Behaviour Under Compression As A Function Of Water Content, A. Al Saleh, D. J. Gallant

Food Structure

The rhea logical behaviour of two wheat varieties (Triticum durum), cultivated at different sites, was studied by INSTRON* as a function of water content. Patterns of crushed grains were investigated by scanning electron microscopy . The apparent modulus of elasticity of the wheat grains was apparently re 1 a ted to their vitreosity. The mealy grain generally had an apparent modulus of elasticity lower than that of the vitreous one and the modulus appeared to be related to the air spaces in mealy endosperm. Humidification favoured the conversion of vitreous endosperm to the mealy state. Grain morphology and particularly the …

Structure Formation In Acid Milk Gels, I. Heertje, J. Visser, P. Smits

Food Structure

The structure formation in acid milk gels is influenced by many factors such as heat, salt system, pH, culture and thickening agents. Understanding of the mechanism of structure formation is important in order to be able to influence the final texture of these products.

In the present study the network formation in acid milk gels during acidification is monitored by freeze-fracture electron microscopy. Network formation appears to be a much more complex process than just an aggregation of the original milk casein micelles; it is accompanied by subtle dissociation and association phenomena of the milk caseins. The observed sequence of …

Ultrastructural And Biochemical Investigations Of Mature Human Milk, Robert J. Carroll, Jay J. Basch, John G. Phillips, Harold M. Farrell Jr.

Food Structure

The casein complexes (casein micelles) of human skim milk were evaluated by electron microscopy. Fourteen samples of human milk were obtained from seven donors whose stage of lactation varied from 1 to 23 months. Compositional and biochemical parameters were measured to evaluate the nature of these samples. For mature human milks, 2-13 months of lactation, average percentage of solids-notfat was found to be 8.32 ± 0.16. Protein compositions of the skim milks were studied by the Coomassie blue dye binding method and by SDS-gel electrophoresis; total protein and casein were found to be 0.62 ± 0.18 and 0.29 ± 0.02 …

The Size Distribution Of Bovine Casein Micelles: A Review, C. Holt

Food Structure

This review considers the average size and size distribution of bovine casein micelles as measured by electron microscopy, light scattering and controlled pore glass chromatography, and the origin and biological function of the size distribution.

Recent work by electron microscopy has given average sizes in reasonable agreement with measurements on the same milk sample by light scattering . It is suggested that natural variations in averaqe micelle size and overestimation of micelle radii by light scattering methods as well as deficiencies in electron microscopical methodology were responsible for past discrepancies.

Electron microscopy and controlled pore glass chromatography provide evidence that …

Seed Structure And Composition Of Potential New Crops, D. W. Irving, R. Beckler

Food Structure

Prosopis , Ol neya , and Amaranthus have potenti a l economic value as food or feed crops fo r a rid /semi- arid r egions. Ma ture seeds of these genera we r e examined using scanning e l ec tron and fluoresce nce microscopy to define a natomy and localize s t or age s truc tures in cells . Pro t ein bodies, some co nt a ini ng phytin inc lu sions , were l oca li zed in the embryos of five Prosopi s s peci es . Prosopis chilensis wa s the only one …

The Combined Effects Of The Calcium Activated Factor And Cathepsin D On Skeletal Muscle, E. A. Elgasim, M. Koohmaraie, A. F. Anglemier, W. H. Kennick, E. A. Elkhalifa

Food Structure

Myofibrils were isolated from atdeath ovin elongissimus muscles and incubated with crude calcium activated factor prepared from the same muscle and with purified cathepsin D. Myofibrils we reincubated with these enzymes separately (first incubation) and successively (second incubation). The major changes induced by cathepsin D first incubation include degradation of myofibrillar proteins with molecular weight > 200 K, myosin, actin, troponin- T and troponin 1. Also new bands appeared at the 140- 160 K, 80 K, 68 K and 30 K regions. Similar changes were obtained 1v hen myofibrils were incubated first with CAF then with cathepsin D (second incubation). On …

A Fluorescence Microscopic Study Of Cheese, S. H. Yiu

Food Structure

Fluorescence techniques were used to study the microstructure of several varieties of cheese. The size and distribution of fat globules in various cheeses were demonstrated by fluorescent staining using Nile Blue A as a marker. Acridine Orange was used as a dye to detect structural differences between casein matrices of various cheese varieties. Differences between the ripe and the less- ripe zones of Ca membert cheese were detected by staining the cheese sections with Acridine Orange and Nile Blue A separately, and then comparing the re sults of the stainings. The Nile Blue A stain ing s howed that fat …

The Microstructure Of Wheat: Its Development And Conversion Into Bread, D, B. Bechtel

Food Structure

Wheat endosperm development has been studied in numerous laboratories. The genera 1 i zed scheme of protein body formation assembled from these data indicates that storage proteins are initially formed in the rough endoplasmic reticulum (RER). The storage proteins in RER may be processed via the Golgi apparatus into vesicles that enlarge by several mechanisms into membrane-bounded protein bodies. The prote in bodies are transported through the cytoplasm to the vacuole where they fuse with the tonoplast and deposit the protein granules into the vacuoles. The protein granules fuse with one another, lose water, and eventually become transformed into the …

Comparison Of The Microstructure Of Firm And Stem-End Softened Cucumber Pickles Preserved By Brine Fermentation, W. M. Walter Jr., H. P. Fleming, R. N. Trigiano

Food Structure

Soft and firm stem end tissues of cucumbers fermented at a low concentration of sodium chloride were examined by a combination of light microscopy {LM), transmission electron microscopy { TEM), and scanning electron microscopy { SEM) . When compared to firm tissue, softened tissue cell walls were swollen and striated, and the middle lamellae were poorly stained by the uranyl acetate-1 ead citrate used in TEM . When the tissue was penetrated by a circu l ar punch {1.5 mm diameter), cells in soft tissue tore along the middle l arne ll ae rather than across cell walls, as did …

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 …

Thermal Analysis Microscopy For The Study Of Phase Changes In Fats, J. M. Deman, A. N. Mostafa, A. K. Smith

Food Structure

An investigation was carried out using the Mettler FPBOO Thermosystem to study polymorphic transitions of several monoacid triglycerides and hydrogenated Canola oil. The system includes a central processing unit connected with a thermal microscopy hot stage that allows the measurement of heat flow to the scrnple . Scanning electron microscopy was also used to examine the same samples after osmium tetroxide fixation . The results obtained relate phase transitions occurring during heating and cooling with the morphology of the various crystal structures.

Crystal Morphology Of Cocoa Butter, D. M. Manning, P. S. Dimick

Food Structure

The multiple melting points of triglycerides have been known and studied for more than a century by numerous workers. The ability of fat to undergo polymorphic changes is important mainly due to its effect on product texture and appearance. Polymorphic resolidification during storage of cocoa butter into higher melting forms can destroy the smooth glossy appearance of a confectionery product. This manuscript will review the polymorphic characteristics and composition of cocoa butter from Theobroma cacao. A discussion of common fat behavior relative to tempering and bloom formation will be included. Scanning electron microscopy and polarized light microscopy aided in visually …

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 …

Properties Of Calcium Caseinates With Disparate Performance In Imitation Cheese, K. Fleming, R. Jenness, H. A. Morris, R. Schmidt

Food Structure

Two commercial lots of calcium caseinate preparations differing in performance imitation cheese were analyzed for various characteristics. A imitation process cheese manufacturing classified the caseinates as good or poor based on appearances of the finished cheese, emulsification of fat, oiling-off during sheeting and melting properties. The sample which exhibited good functional properties in imitation cheese, had slightly higher calcium (16.4 mg/g protein), non-casein protein (2.87%) and y-casein contents, a higher formal titre (8.95 mg free amino N/g protein), lower water absorption (138 mg/100 g protein), and lower stability to added calcium (8.0 min) than did the other sample (14.6 mg/g, …

Ultrastructural Ultilization Of Plants By Herbivores, L. H. Harbers

Food Structure

Study of the patterns of ruminal digestion of forages enhances the nutritional knowledge of how specific plant tissues are digested and adds its own dimension by characterizing the specific cells and the complex interactions of ruminal microflora with those tissues. A common pattern of digestibility exists for mono- and dicotyledon leaves: mesophyll and phloem are degraded readily, and sclerenchyma slowly, whereas cuticle and the remaining vascular tissues are rarely utilized . Digestion of stems is limited to parenchymal tissues in monocotyledons and to cortex and parenchyma in dicotyledons. Epidermal silica and cuticle are undigestible and restrict microbial entrance. Calcium oxalate …

Scanning Electron Microscopic Study Of Rockfish Preserved At Either Ambient Temperature Or By Isothermal Freeze-Fixation, L. E. Lampila, V. Mohr, D. S. Reid

Food Structure

Fresh rockfish (Bocaccio, Sebastus paucispinis) fillets were blast frozen and stored at either -5 °C or -20 °C for 60 days . At defined sampling intervals, speci mens were removed and chemically fixed at either ambient temperature or isothermally, at the respective storage temperatures (-5 °C or -20°C) . The results indicated that isothermally freeze - fixed specimens showed a degree of crushing and/or distortion of the muscle fiber, the deposition of presumed ice crystals in the cell membrane, the multi-dimensionality of connective tissue and the preservation of fine detail . In specimens fixed at ambient temperatures , structura l …

Characterisation Of Milk Proteins In Confectionery Products, J. F. Heathcock

Food Structure

The proteins from milk play an important part in the structural properties of confectionery products. These properties will in turn influence texture and flavour. Electron microscopy techniques have been used to examine milk chocolate, caramel and fudge and to locate and characterise the milk proteins within their structures. Following scanning electron microscopy examination of the products at low temperature, thin sectioning and freeze-fracture were used to resolve the fine ultrastructure of casein and whey proteins.

A chocolate prepared from milk crumb could be distinguished from one made with a dry milk powder on the basis of a more even distribution …

The Light Microscopy Of Triglyceride Digestion, John S. Patton, Russel D. Vetter, Margit Hamosh, Bengt Borgstrom, Mats Lindstrom, Martin C. Carey

Food Structure

During fat digestion (lipolysis) a number of physiochemical events can be seen directly by light microscopy. Hydrolysis of emulsified fat droplets bylipases at pHs above about 6.5 proceeds with the formation of visible product phases that may include both crystalline as well as liquid crystalline phases. The crystalline phase is primarily calcium-fatty acid soap and its formation is favored by high calcium concentrations, alkaline pHs, and inhibited by low pH and monoglycerides. The formation of liquid crystalline product phases are favored by low calcium-concentrations. monoglycerides and lipid saturated bile salt solutions. Both phases are solubilized by bile salts but the …

Early Research On The Fibrous Microstructure Of Meat, H. J. Swatland

Food Structure

The older scientific literature on the histology of skeletal muscle describes the trans verse fragmentation of myofibrils to form sarcomere disks and the attachment of Z lines to the sarcolemma in contracted muscle. These phenomena may now be explained by recent research on the cytoskeletal framework of muscle fibers, particularly desmin and vinculin. The formation of sa rcomere disks might be developed as a simple method to study cytoskeletal integrity in meat. In early research, contraction bands and the disappearance of transverse striations during contraction caused considerable confusion with ordinary light microscopy. These problems were largely resolved by the use …

Application Of Electron Spin Resonance Techniques To Model Starch Systems, L. E. Pearce, E. A. Davis, J. Gordon, W. G. Miller

Food Structure

Starch model systems were examined by electron spin resonance (ESR) techniques with either 16-DOXYL-stearic acid or TEMPO spin probes in water or hexane. Room temperature starchwater- 16-DOXYL-stearic acid spectra showed strong adsorption occurred between the starch and probe. Starch-water-TEMPO spectra at room temperature did not show strong adsorption between starch and probe, but did show some slowed motion of the probe as a result of different local environments experienced by the probe within the starch granule. Starch-water-probe spectra from systems heated from 45-95° C showed no major differences from unheated samples. Also, no major spectral differences existed for each starch …

Development Of Microstructure In A Cream Cheese Based On Queso Blanco Cheese, Miloslav Kalab, H. Wayne Modler

Food Structure

A Cream cheese was made by mixing cultured high fat cream (5~% fat) with Queso Blanco curd and by homogenizing the mix at 70°C. The final product contained 30. 01. to 33.)% fat and 54.1 to 54.5% moisture. The Queso Blanco curd was obtained by precipitating the casein and denatured whey protein from heated whole milk (b2.~ to SI8.0°C) by bringing the pH to 5.3-5.5 with citric acid, using a continuous process. The extent of denaturation of the whey protein portion varied from 5 to 100%, depending on the heat treatment of the milk. Scanning and transmission electron microscopy revealed …

Small Angle X-Ray Scattering Of Hydrated Wheat Starch Granules, M. Yang, J. Grider, J. Gordon, E. A. Davis

Food Structure

Wheat starch:water (1:2) dispersions were studied by small angle x-ray scatter diffractometry (SAXS), and by light, polarizing microscopy, and scanning electron microscopy (SEM). X-ray scatter data were collected in the 64-661 A range. Radii of gyration (Rg) of spherically shaped regions and d-spacings were calculated for samples that were treated as follows: 25° C and run at 25° C; heated to 88° C and run at 82° C; heated to 88° C, stored at 25° C for 2 h or 3 days and run at 25° C; heated to 88° C, stored at 2° C for 3 days and run …

Seed Microstructure: Review Of Water Imbibition In Legumes, Barry G. Swanson, Joe S. Hughes, H. Paul Rasmussen

Food Structure

Scanning electron microscopy (SEM) is an invaluable tool for studying foods and food products. SEM has been particularly va luable in the study of seed microstructure and the ro le of microstructure in water imbibition by legumes. Controversy continues to surround the causes of hard ness in legumes as addi tional research revea ls differences between legumes that imbibe water and legumes that fail to imbibe water. SEM observation of the microstructural changes occurring in legumes during water imbibition ofkrs a better undcrstandi ng of d i ffc rcnces that ex ist betwee n hard and normal beans. Structural changes …

Microstructural Changes In Maturing Seeds Of The Common Bean (Phaseolus Vulgaris L.), Joe S. Hughes, Barry G. Swanson

Food Structure

Seeds of Phaseolus vulgaris L. beans were collected at weekly intervals throughout maturation and examined by scanning electron microscopy (SEM). No major structural changes were observed on the surface of the seed coat during the seven week study period. A cross-sectional examination of the seed coat revealed a substantial increase in thickness of the parenchyma cell layer in young seeds followed by a dramatic decrease in thickness as the seed approached maturity. In the cotyledons, the diameter of the storage cells and starch granules increased over time, with distinct protein bodies becoming visible only in the later stages of maturity. …

Changes In Typical Organelles In Developing Cotyledons Of Soybean, K. Saio, K. Kondo, T. Sugimoto

Food Structure

Soybean cotyledonary cells harvested every 5-10 days at 15 to 60 days after flowering (OAF), were investigated by means of light and transmission electron microscopy. In the early developing stages (15-20 OAF) most of the cells were occupied by large, centrally located vacuoles while the cytoplasm was restricted to a thin layer against the cell wall and contained numerous ribosomes, mitochondria, plastids, small amounts of endoplasmic reticulum (ER) and minute lipid bodies. At about 25 OAF, spherical organelles which contained protein, lipid and sugar (PLS bodies), appeared and then increased in number and in size. Vacuoles had protein deposits lining …

Structure Of Coarse And Fine Fractions Of Corn Samples Ground On The Stenvert Hardness Tester, Y. Pomeranz, Z. Czuchajowska

Food Structure

Kernels from a pair of isogenic lines (with regard to hardness) and two commercial hybrids of dent corn (that varied in hardness) were ground on the Stenvert Hardness Tester and separated by sieving into coarse (>0.710 mm) and fine (<0.500 mm) fractions. The corn samples differed little in oil contents. The coarse particles from the hard corn samples were angular and sharp-edged; those from the soft corn samples were rounded. The yield of coarse particles was higher and they contained less oil in hard than in soft corn. Fine particles from all four corn samples had higher oil content than the coarse particles. Visual examination, observation at low magnification under a light microscope, and use of a scanning electron microscope revealed consistent differences in the extent and mode of corn kernel breakdown during grinding. Particles in the coarse fraction from hard kernels were to a large extent intact with little exposure of their contents. In the soft kernels, particles in the coarse fraction were broken extensively and their contents exposed. It is postulated that differences in the extent of mechanical breakdown and oil content are related to differences in shelf life of corn grits.