Food Science Commons^™

Food Microscopy And The Nutritional Quality Of Cereal Foods, Suk Hing Yiu

Food Structure

The nutritional quality of cereal foods is directly related to the nature of nutrient storage in cereal grains. Most cereal nutrients, such as carbohydrates and minerals , are st ructurally bound. Processing alters the structural organization of the cereal grain. Results obtained from many nutritional studies indicate that the structure and physical form of a cereal food greatly influence the availability of its nutrients.

Using oats and wheat as examples, this review demonstrates how microscopy contributes to understanding the relationship between cereal structures and the availability of nutrients in cereal foods. Various forms of food microscopy play important roles in …

Physico-Chemical Changes Occurring In Gamma Irradiated Flours Studied By Small-Angle X-Ray Scattering, K. Ciesla, T. Zoltowski, R. Diduszko

Food Structure

Commercial samples of wheat, rye and potato flour and flaked oats, as well as ground flaked oats and fresh potatoes were gamma-irradiated (20 or 30 kGy dose). The products and appropriate control samples were inves tigated by small-angle X-ray scattering (SAXS) in the range of 28 from 0.357 to 6.46 degree (CuKa radiation). The results were compared with those obta ined for pure potato starch. Effects of grinding and heating at 100° Con SAXS results were also examined.

Different scattering curves were obtained for various unirradiated products. Refl ect ions derived from starch were de tected for some uni rradiated …

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 …

Microstructure Of Whey Protein/ Anhydrous Milkfat Emulsions, M. Rosenberg, S. L. Lee

Food Structure

Research has been undertaken in order to determine the microstructure of emulsions consisting of whey proteins and anhydrous milk fat. The results revealed that whey protein films were formed at oil/water interfaces. Scanning electron microscopy (SEM) analysis of chemically fixed specimens1 and cryo-SEM analysis of partially etched, fro zen specimens revealed that the ad sorbed protein layer (coating the fat droplets) had a granular, aggregated appearance. Emulsions with a high fat load prepared under high homogenization pressure exhibited a bimodal particle-size distribution. Clu!;tering of the protein-coated droplets, and sharing phenomena at the oil / protein interfaces were evident in these …

Water-Holding Properties Of Milk Protein Products - A Review, W. Kneifel, A. Seiler

Food Structure

Water-holding properties have been well recognized by food technologists among !he diversity of functional properties attributed to milk protein products. In general , water-holding is accomplished by a complexity of interactions between water and milk proteins. Besides the term water-holding, synonyms such as water retention, imbibing and hydration have been used to describe this phenomenon. This paper provides a clearer understanding of this parameter by considering some fundamentals of both the molecular structure of milk proteins and the physical in terrelationships between water and milk protein powder particles. Differences in water-holding properties of milk protein products are frequently observed and …

Baking Properties And Microstructure Of Yeast-Raised Breads Containing Wheat Bran: Carrageenan Blends Or Laminates, P. R. Belisle, B. A. Rasco, K. Siffring, B. Bruinsma

Food Structure

Breads prepared using a commercial prototype sponge-and·dough formulation with no added gluten and containing white wheat bran:carrageenan blends or white wheat bran:carragcenan laminates (I 0% by weight nour replacement) had acceptable loaf volumes and crumb grain scores. Doughs con taining white wheat bran:carragccnan blends had a hi gher water absorption and longer mi xing time than doughs con taining wheat bran: carragecnan laminates wi th the same quantity of carrageenan . The addi tion of carrageenan to doughs resu lted in a hi gher water absorpti on va lue compared to the doughs contai ning wheat bran only. Breads made …

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 …

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 scanning electron …

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 …

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 …

A Comparison Of The Effects Of Oven Roasting And Oil Cooking On The Microstructure Of Peanut (Arachis Hypogaea L. Cv. Florigiant) Cotyledon, Clyde T. Young, William E. Schadel

Food Structure

Peanut (Arachis hypogaea L. cv. Florigiant) cotyledon microstructure after oven roasting and oil cooking at 160 C was documented with scanning electron microscopy, light microscopy and transmission electron microscopy . Changes in peanut cotyledon microstructure were compared as thermal processing time at 160°C was increased for both oven roasting and oil cooking. The purpose was to evaluate thermal modifications in the cytoplasmic network, protein bodies and cell-to-cell junctions as thermal processing time in creased for each heating method. Principal findings included differences in the times at which these modifications occurred during the two thermal processes. Oven roasting a t 160 …

Three-Dimensional Molecular Modeling Of Bovine Caseins, Harold M. Farrell Jr., Eleanor M. Brown, Thomas F. Kumosinski

Food Structure

Three-dimensional (3 -D) structures derived from X-ray crystallography are important in elucidating structure- function relationships for many proteins. However, not all food proteins can be crystallized. The casei ns of bovine milk are one class of non-crysta11izable proteins (a, 1-, K-, and /3-). The complete primary and partial secondary structures of these proteins are known, but homologous proteins of known crystallographic structure cannot be found. Therefore , sequence based predictions of secondary structure were made and adjusted to conform with data from Raman and Fourier-transformed infra- red spectroscopy. With this information, 3-D structures for these caseins were built using the …

Microstructure And Fat Extractability In Microcapsules Based On Whey Proteins Or Mixtures Of Whey Proteins And Lactose, D. L. Moreau, M. Rosenberg

Food Structure

Research was undertaken to determine the microstructure of whey protein/lactose-based , anhydrous milk fat- containing , spray -dried microcapsules and to study the relationship between core extractability and the state of lactose in these microcapsules. Spherical microcapsules nearly free of surface dents were obtained in a ll cases The milkfat was found to be organized in the form of small droplets (0.2-0.8 um) embedded in the capsule wall. The surface topography of the capsul es ex hibited features that may be li nked to removal of mil kfat drop lets from th e outer surfaces at early stages of the …

Microstructure Of Black, Green And Red Gram, Enamuthu Joseph, Shelly G. Crites, Barry G. Swanson

Food Structure

The three most commonly consumed legumes (grams or pulses) in India, black gram (Vigna mungo (L.) Hepper), or urd , green gram (Vigna radiata (L.) Wilczek) or mung, and red gram (Cajanus cajan (L.) Millsp.) or tur, were examined by scanning electron microscopy . Seed coat and internal features were examined to differentiate these legumes from common beans (Phaseolus vulgaris) , adzuki beans (Vigna angu/aris) and lentils (Lens culinaris). Cross-sections of the seed coats of black, green and red gram contained single layers of columnar palisade cells extending as double palisade layers at the hilum regions. The funiculi located above …

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 …

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, …

The Stabilisation Of Air In Cake Batters - The Role Of Fat, B. E. Brooker

Food Structure

The role of fat crystals in the stabilisation of air bubbles in cake batters was studied with aqueous phase aerations prepared by the "all in one" method using shortening containing emulsifier. During mixing, fat crystals become coated with an interfacial layer of ad sorbed protein (crystal -water interface). They adsorb to the surface of bubbles (that have been transiently stabilised by egg proteins) by a process which involves the fu sion of the crystal-water interface with the air-water interface.

The adsorption of fa t crystals helps to stabilise large numbers of small bubbles which must expand without rupturing during baking …

Composition And Microstructure Of Commercial Full-Fat And Low-Fat Cheeses, V. V. Mistry, D. L. Anderson

Food Structure

The objective of this study was to analyze the composition of commercial full-fat and low-fat cheeses and to evaluate their microstructure. Commercial cheeses evaluated included full-fat and low-fat Cheddar, Mozzarella , processed, and Swiss cheeses. Cheddar cheeses ranged from 8.2% fat and 5 1.1% moisture in the 75% low-fat product to 33.2% fat and 35.9% moisture in the full-fat cheese . Mozzarella cheeses ranged in fat from a low of 2. I% to a high of 24% with corresponding moisture content of 56.6 to 45.5% respectively. Fatfree processed cheese had 0. 9% fat and 58.7% moisture , while the full …

Development Of The Food Microscopist, D. F. Lewis

Food Structure

This paper describes the processes through which the food microscopist develops his/her skills. It is based around a framework of Shakespeare's seven ages of man. The first stage is learning about equipment: how it works and how not to abuse it. Next, attention turns to how to prepare samples for examination whilst maintaining the validity of the observations and avoiding damage to the instrument. The "Lover" is the time at which an understanding of the basic structures of food products is gained and the "Soldier " starts to interpret these structures in terms of the performance of the foodstuff. Next, …

Properties Of Irradiated Starches, A. S. Sokhey, M. A. Hanna

Food Structure

Properties of irradiated starches have been outlined in this review . ')' -radiation generates free radicals on starch molecules which cause changes in starch properties . The intensity of free radicals is dependent upon starch moisture content , and temperature and duration of storage. Increasing dosages of -y-irradiation creates in creasing intensities of free radicals on carbohydrates. These free radicals are responsible for bringing about molecular changes and fragmentation of starch molec ules. Increasing ')' -irradiation dosages cause an in crease in acidity , and decreases in viscosity and water solubility of starches. The granule structure remains visually undamaged at …

Microstructural Approach To Legume Seeds For Food Uses, Kyoko Saio, Michiko Monma

Food Structure

This review summarizes the microstructures of several seed legumes based on previous work and some new findings. Fifteen species of tropically grown legumes , adzuki bean and soybeans (a leading variety and two local va rietie s) were examined by light and transmission electron microscopy in relation to food uses. Processing of adzuki beans to form Q!l bean paste is dis cussed to illustrate the effects of processing on microstructure of starch g rains. Differences in contents, shape and size of starch grains are emphasized in a comparison of soybeans wi th other legumes.

Microstructure Of Idli, Enamuthu Joseph, Shelly G. Crites, Barry G. Swanson

Food Structure

The microstructure of idli prepared from seeds of common beans (Phaseolus vulgaris) and rice, and Indian black gram seeds ( Vigna mungo) and rice in the ratio 1:2 was examined . Intact starch granules and protein bodies were observed in the unfermented idli batter. Starch granules disappeared as fermentation time increased to 18 hours and 36 hours. The surface of idli prepared from 36-hour fermented batter was cohesive , dense and sponge- or foam-like. The microstructure of idli prepared from common beans and rice was similar to the microstructure of idli prepared from Indian black gram and rice. Common beans …

An Overview Of The Role Of Fat In Nutrition And Formulation And Its Measurement In The Live Animal, Meat Carcass And Processed Meat Products, Paul B. Newman

Food Structure

The role of fat in nutrition and health is complex but one about which consumers have only recently become aware. As a consequence of changing consumer attitudes and because fat affects many physical attributes in food, raw material suppliers and food manufacturers have attempted to improve the range and nutritional composition of available foodstuffs. However, with a substantial price difference between fat and lean, and ever-increasing demands for improved throughputs and operational cost performance, producer and manufacturing sectors require rapid, accurate methods of fat measurement suitable for commercial application. These are only just beginning to become available but should ultimately …

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 …

Distribution And Intracellular Localization Of Titanium In Plants After Titanium Treatment, G. Kelemen, A. Keresztes, E. Bacsy, M. Feher, P. Fodor, I. Pais

Food Structure

The physiological role of titanium in plants has not been elucidated yet, but a higher rate of growth , greater chlorophyll content and higher productivity, among others , may be attributed to this element. We have investigated the distribution of titanium in wheat seedlings after Titavit (a Ti ·ascorbate containing plant conditioner) treatment applied either through the leaf or through the root. In field experiments, we also sprayed spinach plants with Titavit. We have found a practically unidirectional tran slocation of Ti from the shoot into the root, and a preferential local ization of Ti in the nuclear cell fraction …

Structure And Composition Of Apple Juice Haze, T. Beveridge, V. Tait

Food Structure

Haze obtained from commercial apple juice over the 1991 season contained from 11.4 to 29.0% protein (w/w) , trace quantities of both metal cations and polymeric carbohydrate, and gave strong responses to tests for phenolic compounds indicating a protein-phenol haze. SDS-PAGE of the 2-mercaptoethanol reduced , guanidinium hydrochloride dissaggregated haze particles gave a continuous smear indicating a population of molecules ranging from 29K to greater than 205K daltons. Transmission electron microscopy of negatively stained preparations revealed the presence of spherical bodies only partially penetrable by stain and possessin g a suhunit structure. These particles were embedded in a material presumably …

Microstructure Of Mozzarella Cheese During Manufacture, Craig J. Oberg, William R. Mcmanus, Donald J. Mcmahon

Food Structure

Scanning electron microscopy was used to examine structural developments during the manufacture of low-moisture, part-skim Mozzarella cheese made by a stirred curd procedure. The micrographs showed changes in the protein matrix , dispersion of fat globules, and bacteria during processing. Most curd knitting occurred during the curd stirring step, particularly dry stirring. A thin (5 ,urn) curd skin was observed on curd particles at the end of dry stirring. Dry salting prior to stretching resulted in the rapid loss of whey from the curd particle. Protein fibers were aligned and longitudinal columns of whey and fat were formed when the …

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 …

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.

Interfacial Interactions, Competitive Adsorption And Emulsion Stability, Jianshe Chen, Eric Dickinson, Graeme Iveson

Food Structure

Food emulsion stability is strongly influenced by the interactions in the adsorbed layer around emulsion droplets. Competitive adsorption of pure milk proteins (13-casein or 13 -lactoglobulin) with nonionic surfactants in oil-in-water emulsions is shown to depend on the age of the adsorbed protein layer. Evidence is presented for slow accumulation of protein at the oil-water interface and/or partition of protein into the oil phase of emulsion droplets containing oil-soluble surfactant associated in reversed micelles. Small amounts of added water-soluble surfactant or calcium ions are shown to have a pronounced effect on the droplet coalescence rate under turbulent shear flow conditions. …