Food Science Commons^™

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 …

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 …

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.

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.

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 …

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.

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 …

Soluble And Insoluble Dietary Fiber In Cooked Common Bean (Phaseolus Vulgaris) Seeds, Joe S. Hughes, Barry G. Swanson

Food Structure

The common bean (Phaseolus vulgaris) requires cooking for extended periods of time prior to consumption. In this investigation both quantitative and microstructural changes in common bean dietary fiber as a result of cooking were examined. Cooking resulted in a slight decrease in soluble dietary fiber and a marked increase in insoluble dietary fiber. The increase in insoluble dietary fiber was responsible for a 15 -30 percent increase in total dietary fiber.

Scanning electron microscopy was used to examine the microstructure of uncooked and cooked bean flours and the insoluble and soluble dietary fiber fractions of these two fl ours. In …

Image Analysis Of The Fat Dispersion In A Comminuted Meat System, Peter A. Koolmees, Piet C. Moerman, Monique H.G. Zijderveld

Food Structure

In a series of experiments on a comminuted meat system, image analyses were conducted to quantify changes in structure as affected by polyphosphate, fat level, and chopping time and temperature. Four batches of comminuted meat were investigated which contained neck beef, pig head meat, rino, ice, salt (2%), fat at a level of either 27 or 40%, and polyphosphate at a level of either 0 or 0. 5%. Structural changes in different stages of comminution coincided with a shift in size distribution, shape factor, density and area percentage of fat particles. The density of the protein matrix (matrix defined as …

Vacuole Formation In Wheat Starchy Endosperm, D. B. Bechtel, A. Frend, L. A. Kaleikau, J. D. Wilson, P. R. Shewry

Food Structure

The formation of vacuoles in wheat (Triticum aestivum cv. Highbury) starchy endosperm cells was studied using electron microscopy. Some vacuoles were always present, even in the coenocytic cytoplasm. The first formed endosperm cells were highly vacuolated, but became filled with cytoplasm as they grew older. Various-sized pieces of cytoplasm were found in vacuoles of developing endosperm cells, probably as a result of autophagic sequestration. The membranes of the autographic vacuoles appeared to originate from the rough endoplasmic reticulum and from extensions of already-formed vacuoles. Autographic activity was confirmed by localizing the hydrolytic enzyme acid phosphatase within the vacuoles. The rough …

Effect Of Heating To 200 C On Casein Micelles In Milk: A Metal Shadowing And Negative Staining Electron Microscope Study, V. R. Harwalkar, Paula Allan-Wojtas, Miloslav Kalab

Food Structure

Milk was heated to 200 C for 3 min in sealed inverted-Y-shaped glass vials and reacted with a glutaraldehyde solution at that temperature. Electron microscopy of the metal-shadowed and negatively stained samples revealed that casein micelles in the milk did not disintegrate extensively at the high-temperature used but, rather, became enlarged. Some of them were found to be either clustered or distorted.

An Electron Microscopic Study Of The Adherence Of Lactobacillus Acidophilus To Human Intestinal Cells In Vitro, S. K. Hood, E. A. Zottola

Food Structure

In this study, transmission electron microscopy was used to visualize the adherence of Lactobacillus acidophilus to human intestinal tissue cells (HITC) in vitro. There appeared to be a layer of electron dense material on the bacterial cell and on the intestinal cell which may mediate adherence. When L. acidophilus attached to intestinal tissue cells after a short contact period, it did not appear to disrupt the integrity of the intestinal cell. Treatment of the bacterium with sodium periodate and concanavalin A reduced the adherence to HITC, suggesting that a carbohydrate was involved. Electron micrographs of periodate-treated cells revealed that the …

Microstructure And Texture Of Meat Emulsions Supplemented With Plant Proteins, Allan T. Paulson, Marvin A. Tung

Food Structure

A model meat emulsion system was used to evaluate the effects of cooking time and temperature on texture, microstructure and cook stability of meat emulsions containing soy or canola protein isolate. The plant proteins were incorporated either dry or rehydrated at replacement levels of 33.3% and 66.7% of the meat protein, and the emulsions were cooked at 70 or 95 C tor 25 or 50 min. Texture of the cooked emulsions was assessed by an instrumental texture profile analysis (TPA) using an lnstron tester . Analysis of TPA and stability data revealed several complex Interactions between experimental variables; however, level …

Advanced Techniques For Preparation And Characterization Of Small Unilamellar Vesicles, G. Masson

Food Structure

Lipid vesicles have become of considerable importance as model membranes and drug delivery systems . Recently , applications in the food industry have been suggested for microencapsulation and immobilization of enzymes.

A number of methods for the preparation and characterization of liposomes have long been available. For the production of small unilamellar vesicles we have used a microfluidization technique. Microfluidization is based on a submerged jet principle in which two fluidized streams collide at extremely high velocities in a precisely designed interaction chamber.

Advantages of this technique include the absence of organic solvents or detergents, the high lipid concentrations that …

Changes In The Ultrastructure Of Beef Muscle As Influenced By Acidic Conditions Below The Ultimate Ph, M. V. Rao, N. F. S. Gault, S. Kennedy

Food Structure

Ultrastructural changes in meat incubated with different concentrations of acetic acid were investigated by transmission electron microscopy. Discs of bovine M. longissimus dorsi (48 h postmortem) were incubated at 46 C for 48 h in various acetlc acid solutions, giving discs with pH values ranging from 5.1 to 3.9 . Below pH 4. 5 , the volume of the discs increased markedly due to water absorption.

Discs incubated in 0.01M acetic acid had a pH of 5.1, lower swelling ratios and shorter sarcomeres than control samples at pH 5. 5. Structural studies of the samples at pH 5.1 revealed that …

The Size Distribution Of Casein Micelles In Camel Milk, Z. Farah, M. W. Ruegg

Food Structure

The size distribution of casein micelles in camel milk has been determined by electron microscopy. Individual and pooled samples were cryo-fixed by rapid freezing and freeze-fractured. Electron micrographs of the freeze-fracture replica revealed a relatively broad size distribution, with an average micelle dimeter around 280 nm in the volume distribution curve. The distribution was significantly broader than that of the particles of cow's or human milk and showed a greater number of large particles. The submicelles were also somewhat larger than those observed in cow's and human milk (approx. 15, 10 and 7 nm, respectively). The average values for the …

Cereal Structure And Its Relationship To Nutritional Quality, S. H. Yiu

Food Structure

Factors that determine the digestibility of carbohydrates and minerals in cereals are examined . Most carbohydrates and minerals in cereals are structurally bound, either surrounded by or associated with cell wall components not easily digested by non-ruminant animals and humans. Treatments such as mechanical grinding and heat improve the digestibility of nutrient s . Further processing and cooking result in structural and physeochemical changes of cereal starch, phytate, and dietary fiber. Such changes greatly Influence the physiological and metabolic effects in animals and humans. The digestive breakdown of most nutrient components is also dependent on the activities of enzymes in …

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

Food Structure

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

Effects Of Protein Concentration In Ultrafiltration Milk Retentates And The Type Of Protease Used For Coagulation On The Microstructure Of Resulting Gels, Dragoljub D.J. Gavaric, Marijana Caric, Miloslav Kalab

Food Structure

Milk retentates (35~ total solids, 13~ protein) obtained by ultrafiltration were diluted with the permeate to 3 . 2, 5.0, 6.5, 10.0, and 13.0% protein and coagulated using conrnerc1al proteases. Rennet or one of microbial proteases isolated from Bacillus potymlxa , Endothla parasfttca, Mucor mtehel, or Mucor pusfllus were used . Coagulation times were decreased with the Mucor proteases as the protein concentrations in the retentates were increased but the coagulation times were increased with B. potymlxa and f. parasltlca proteases under similar conditions . Firmness was higher in gels made from homogenized retentates than from nonhomogenized retentates of the …

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

Food Structure

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

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

Use Of Image Analysis To Predict Milling Extraction Rates Of Wheats, A. D. Evers, R. P. Withey

Food Structure

Image analysis of grain morphological characteristics was examined as a possible means of predicting extraction rates of a wide variety of wheat types.

Two elevations of grain were examined and measured for the top view whole grains were used, while for the lateral view grains were sagittally bisected in the plane of the crease. Extraction rate was assessed on laboratory mills and expressed as flour yield.

Milling extraction rate correlated with one shape factor with a coefficient of 0.78. Inclusion of a second factor in a stepwise regression increased the correlation coefficient to 0.925.

No satisfactory predictor of extraction rate …

Fluorescence Microscopy Studies On (1,3) - B-D-Glucan In Barley Endosperm, A. W. Macgregor, G. M. Ballance, L. Dushnicky

Food Structure

Development of (1,3;1,4)-B-D-glucan and (1,3)-B-D-glucan in kernels of Himalaya and Bonanza barley has been followed by fluorescence microscopy using calcofluor and aniline blue fluorochromes. Specific enzymes were used to confirm the identity of these two polysaccharides in sections of endosperm tissue. All barley lines tested contained both types of B-glucan but (1,3;1,4)-B-glucan was synthesized at an earlier stage of development than was (1,3)-BGlucan. Small bead-like deposits of (1,3)-B-glucan were detected in all cultivars examined. These deposits were present throughout the endosperm and appeared to be associated with the inner walls of endosperm cells. After treatment of sections with (1,3)-B-glucanase, these …

Electron Microscopic Localization Of Cholesterol In Bovine Milk Fat Globules, Robert W. Martin Jr.

Food Structure

An electron microscopic method designed for the detection of cholesterol in milk fat was evaluated for reliability. This method is based on the incubation of cream from raw milk with fillipin (a polyene antibiotic) which has a specific affinity for cholesterol followed by freeze fracturing and electron microscopic examination of fat globules. Cholesterol was localized within the membrane and the triglyceride core of milk fat globules. Cholesterol was highly organized within membrane portions and less organized within triglyceride portions of milk fat globules. The configuration of localized cholesterol was similar to configurations reported for plasma membranes.

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

Food Structure

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

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

Analysis showed that increasing radiation dose increased …

Microstructural Changes In Wheat Starch Dispersions During Heating And Cooling, M. Langton, A. M. Hermansson

Food Structure

Microstructural changes in 8-11% wheat starch dispersions during heating, cooling and cold storage have been evaluated by light microscopy and scanning electron microscopy.

Heat treatment of wheat starch dispersions gives rise to two stages of swelling and solubilization. During the first phase of swelling, solubilized amylose was observed ln the centre of the granules and, to some extent, outside the granules. Further swelling deformed the granules and more amylose was released. When the temperature treatment took place under shear, the outer layer of the swo llen granules fra ctured at 94°C and above, and amylopectin fragments were dispersed into the …

Structural Characteristics Of Pennisetum Americanum (Pearl Millet) Using Scanning Electron And Fluorescence Microscopy, C. M. Mcdonough, L. W. Rooney

Food Structure

Fluorescence bright field and scanning electron microscopy were used to characterize the structure of selected mature pearl millet caryopses from the World Germplasm Collection. Kernel shape (globose, lanceolate, obovate and hexagonal). kernel endosperm color (while. yellow and grey) and external appearance (color) of the samples were documented for 96 varieties. Color of the pearl millet kernel was due to the combined effects of pigmentation in the pericarp. aleurone and endosperm. as well as the pericarp thickness. White kernels had few pigmented areas. yellow kernels had pigments primarily in the epicarp and endosperm. and brown kernels had pigments in the epicarp. …

Grittiness In A Pasteurized Cheese Spread: A Microscopic Study, H. W. Modler, S. H. Yiu, U. K. Bollinger, M. Kalab

Food Structure

Coagulation of pasteurized (63 C for 30 min) milk and blending of the resulting curd with high-fat cream followed by heat treatment (44 to 80 C for 10 min) of the blend in preparation of a hot-pack cheese spread led to the formation of a gritty product. Microscopic examination of hard particles causing the grittiness indicated that they consisted of compacted protein. Staining for calcium failed to detect any elevated concentration of this element in the particles. They were amorphous and contained no crystalline structures.

Encapsulation of the gritty curd in agar gel tubes made it possible to freeze-fracture the …

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

Food Structure

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

A Method For Light And Scanning Microscopy Of Drought-Induced Damage Of Resting Peanut Seed Tissue, Clyde T. Young, William E. Schadel

Food Structure

Tissue damage creates numerous problems for the microscopic examination of resting peanut (Arachis hypogaea L. cv . Florunner) seed physical structure. This paper presents a method to deal with specific problems encountered in light microscopy (LM) and scanning electron microscopy (SEM) of drought - induced damage of peanut tissue . Major findings include: (1) improved SEM imaging through reduction of charging by increasing coating thickness from 25 nm to 30 nm; (2) improved stain affinity for LM tissue preparations by decreasing osmium tetroxide fixation time from 2 hours to 1 hour; and (3) im proved tissue fixation for LM and …