Food Science Commons^™

Mechanisms Of Hard-To-Cook Defect In Cowpeas: Verification Via Microstructure Examination, Keshun Liu, Yen-Con Hung, R. Dixon Phillips

Food Structure

It has been hypothesized that part of the hard-to-cook (HTC) defect in cowpeas is due to decreases in solubility and thermal stability of intracellular proteins during storage since coagulated proteins would limit water to starch and prevent full swelling during cooking. To verify this hypothesis, effects of soaking and heating temperature on texture, water absorption, protein water extractability and microstructure of control and HTC cowpea seeds (aged or treated) were studied. Scanning electron microscopy showed no structural difference between dry control and dry aged seeds. However, after soaking, in contrast to the control, aged seeds exhibited a coarse protein matrix …

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 …

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. …

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 …

Fluidization And Its Applications To Food Processing, N. C. Shilton, K. Niranjan

Food Structure

This paper is a comprehensive review of the science behind fluidization of food materials, and its applications in food processing. Fluidization is a process by which a bed of particulate materials exhibts fluid -like behaviour as a result of fluid flowing through it. Fluidization can be carried out by liquids or gases and different forms of fluidization occur depending on the type of fluidizing medium and the properties of the particulate material , this can have an important effect on the type of processes that can be carried out using fluidization.

Typical food processing applications of fluidization include freezing and …

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 …

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 …

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 …

Whey Proteins As Microencapsulating Agents. Microencapsulation Of Anhydrous Milkfat - Structure Evaluation, M. Rosenberg, S. L. Young

Food Structure

Microencapsulation of milkfat may open new fields of application for this milk constituent by transforming it into dry and stable powder. Research has been undertaken to study the microstructure of whey protein based, anhydrous milkfat-containing, spray-dried microcapsules. Whey protein concentrates of 50% and 75% protein and whey protein isolate were evaluated as microencapsulating agents (wall materials). The effects of wall composition, fat load , and drying conditions on the capsule's structure were studied by scanning electron microscopy (SEM). Spherical capsules with smooth , wrinkle-free surfaces were observed in all cases. Whey protein isolate-based microcapsules dried at a temperature higher than …

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 …

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 …

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 …

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.

Microstructural Studies In Fat Research, I. Heertje

Food Structure

Microstructural studies play an important role in establishing the relation between composition, processing and final properties of many food products. In order to arrive at a full description of microstructure many visualization- and preparation techniques are needed. A number of fatty products such as shortenings, margarine , butter, and low fat spreads are discussed from a microstructural point of view. Examples of the influence of process parameters on microstructure and rheological properties are given. In particular, attention is paid to the fat crystalline matrix and the emulsion structure.

Further, a new methodology is described making it possible to study interactions …

The Stabilisation Of Air In Foods Containing Fat - A Review, B. E. Brooker

Food Structure

Foods containing aqueous solutions of proteins readily foam when air is introduced into them. When fat is also present, interaction between the two components at the air/water interface may produce a stable foam with characteristic bulk properties. In the case of dairy foams (such as whipped cream), bubbles produced in the whipping process are initially stabilised by the adsorption of protein at the air/water interfaces.

Commonly encountered defects in whipping cream arise when large triglyceride crystals, formed in masses of free fat, adsorb to the air/water interface during whipping at the expense of fat globules.

In other food systems , …

Practical Aspects Of Electron Microscopy In Dairy Research, Miloslav Kalab

Food Structure

Milk products are based mostly on casein micelles, fat globules, and whey proteins. The former two constituents are corpuscular and whey proteins become corpuscular when coagulated. Structural changes in these basic constituents during processing have been studied by electron microscopy. This review discusses the structures of yoghurt, curd, cheeses (hard cheeses, mould-ripened cheeses, cream cheeses, and process cheese), cream, milk powders, and nontraditional dairy products. Defects and deviations from traditional structures of these products are explained where the causes are known. Examples of such causes are foaming of milk, presence of unusual ingredients (bacterial polysaccharides, whey protein concentrates), and alterations …

Microstructure And Rheological Properties Of Composites Of Potato Starch Granules And Amylose: A Comparison Of Observed And Predicted Structures, K. Svegmark, A.-M. Hermansson

Food Structure

Potato starch granules were gelatinised in amylose solution to study the effect of adding amylose to a highswelling granular starch system. The effects of varying the amount of potato starch from 1-10% , added to a solution of 2% amylose, were studied by means of dynamic viscoelastic measurements and light microscopy.

The granules gelatinised in amylose solution had a lower degree of swelling than those gelatinised in water. The restricted swelling in amylose was reflected in a decrease in the complex shear modulus (G*) at 75'C. GeJatinisation in 2% amylopectin also caused a decrease in G*, but gelatinisation in 2% …

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 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 …

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 …

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.

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. …

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 …

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 …

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 …

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 …

Structure-Compressive Stress Relationships In Mixed Dairy Gels, J. M. Aguilera, J. E. Kinsella, M. Liboff

Food Structure

Mixed dairy gels (including a control without fat) of skim milk powder (SMP) and whey protein isolate (WPI) containing fat globules were formed by heating protein emulsions to 90°( and by acid release from glucono- 0-lactone to provide a pH of 4.3-4.4 . Fat globules with artificial protein membranes (FGAPM) were prepared by homogenization of a butter oil /water mixture in the presence of WPI while fat globules without membranes were stabili zed with polyoxyethylene sorbitan monolaurate (Tween 20). Both emulsions were added at a 4% (w/w) leve l to solutions having 3% SMP and 8.3% WPI. The gel contai …

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 …