Food Science Commons^™

Vegetable Freezing Methods, Georgia C. Lauritzen, Charlotte P. Brennand

All Archived Publications

No abstract provided.

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. …

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 …

An Apparatus For A New Microcube Encapsulation Of Fluid Milk In Preparation For Transmission Electron Microscopy, M. C. Alleyne, D. J. Mcmahon, N. N. Youssef, S. Hekmat

Food Structure

A simple apparatus has been developed for a new "microcube" encapsulation of fluid milk samples in their prefixation preparation for electron microscopy. The new technique is based on making cubic wells in an agar gel layer, filling them with fluid milk samples, and sealing them with another agar gel layer . The individual wells are then separated by cutting from the initial block, providing 0.5 mm walls around the samples. The embedded material (milk, buttermilk, yogurt, etc.) is fixed, dehydrated , and embedded in a resin for transmission electron microscopy. The procedure is simpler, and more versatile, reliable, and reproducible …

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 …

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 , …

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% …

Relationship Between The Starch Granule Structure And The Textural Properties Of Heat-Induced Surimi Gels, V. Verrez-Bagnis, B. Bouchet, D. J. Gallant

Food Structure

Starch, used as a textural additive in heat-induced surimi gel, influences the rigidity of the protein gel matrix and hence the gel strength according to its botanical characteristics. The present study focuses on the correlations existing between the textural properties of heatind uced surimi gels obtained by physical measurements and the characteristics of different commercial starches. The gelatinization temperature of starch was closely related to the expressible moisture, work to fracture, and elongation. Behaviour of starchy components during thermal processing and its relationship to fish protein gel matrix were studied by light and electron microscopy. These studies showed differences in …

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 …

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. …

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 …

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 …

Hydrocolloids As Food Emulsifiers And Stabilizers, Nissim Garti, Dov Reichman

Food Structure

Hydrocolloids are water-soluble biopolymers consisting of high molecular weight polysaccharides known as viscosity builders, gelification agents and stabilizers of food systems.

Several hydrocolloids such as gum arabic (acacia), tragacanth, xanthan and certain modified gums have been mentioned as food additives having special functions such as: "retardation of precipitation of dispersed solid particles and coalescence of oil droplets". The role of these gums as emulsifiers remained somewhat obscure. The present review is an attempt to bring the relevant studies together and to throw some light on the functionalities of the gums as surface active agents and food emulsifiers. In addition, some …

Can Antibiotic Test Kits Be Useful?, Bart Weimer

Archived Food and Health Publications

Publication discusses whether or not antibiotic test kits are useful and what the various results mean.

Proceedings From The 29th Annual Marschall Italian Cheese Seminar, Various Authors

Cheese Industry Conference

Three 375 lb vats of cultured low moisture pan skim Mozzarella cheese were produced from the same batch of standardized milk and rennet, but using three different rod (Lactobacillus bulgaricus - Marschall ProduciS - Thennorod) and coccus (Streptococcus thermophilus - Mar chall Product - Thennococcus) ratios (9R:IC, 5R:5C, and !R:9C). The total volume and total colony fonning units of culture added was kept constant for all ratios (i.e., I 02 ml/375 I b). Cheese was made with the ·'no-brine·· chee e making method using a I06°F (41° ) cook temperature, 6.4 draw pH *whey), 5.25 milling pH, and 135°F (57°C) …

Changes Over Time In Sensory Thresholds Of Individuals With Diabetes Mellitus And The Relationship To Food Preference, Marnie Ricks Spencer

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The effect of time on taste threshold was examined in 30 diabetics and 30 control subjects (ages 22-30) who had participated in a sensory study 14 years previously. Detection and recognition taste thresholds for sweet (sucrose), salty (sodium chloride), sour (citric acid), and bitter (quinine sulfate) were assessed using triangle testing. Food preferences related to concentration of the stimuli in model food systems were tested using a nine-point hedonic scale. Mashed potatoes were used as the carrier for different levels of salt. A beverage composed of water, sucrose, and citric acid was varied to measure preferences for sweet and sour …

The Role Of Lactose In The Age Gelation Of Ultra-High-Temperature Processed Concentrated Skim Milk, Venkatachalam Narayanaswamy

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The purpose of this research was to relate lactose reactivity and age gelation of UHT processed concentrated milk. Skim milk was pasteurized, diafiltered batchwise to reduce lactose concentration to less than 0.05%, and UF concentrated to 3X (one-third volume reduction). Lactose and sucrose were then each added at 3% or 6% w/v to part of the concentrate. The five samples, control (

All samples stored at 4°C and 20°C gelled after 21 weeks of storage. The viscosity changed slightly during the first 19 weeks of storage but increased suddenly (> 100 cPs) just before gelation. Samples stored at 35°C did …

Effects Of Stabilizers And Ph Adjustments On Milk Proteins In Uht-Treated Citrus Juice/Skim Milk Blend Drink, Sandra M. Newman

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A UHT-processed skim milk (85%)/orange juice (15%) drink was developed. Product integrity and stability were maintained by two methods. Proper homogenization of the blend before UHT processing stabilized a drink formulation containing .25% carboxymethyl cellulose and .025% carrageenan. Adjusting the pH of the blend (pH 6.3 and 6.5) resulted in a different stabilization. After 28 days at room temperature, settling of milk solids was 5.2% of volume height in the prehomogenized sample and 86.9% of volume height in the same blend that had not been homogenized prior to UHT processing. After storage, the two treatments were analyzed to verify that …

A New Method For Measuring Macroparticulate Systems Applied To Measuring Syneresis Of Renneted Milk Gels, Jonathan R. Maynes

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Syneresis is an integral part of cheese manufacture. The rate and extent of syneresis affect the properties of cheese. There are many factors that affect syneresis, but measured results vary because of inaccuracies in measuring techniques. To better control syneresis, an accurate mathematical description must be developed. Current mathematical models describing syneresis are limited because of inherent error in measuring techniques used to develop them. Developing an accurate model requires an accurate way to measure syneresis.

The curd becomes a particle in a whey suspension when the coagulum is cut. The most effective technique to measure particle size, without interference, …

Effects Of Potassium Lactate, Encapsulated Citric Acid And Storage Temperature On Microbial Growth And Shelf Life Of Pork Sticks, Yen-Kan Su

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A new product, pork sticks, was developed. Optimum shelf life and safety were major concerns associated with this product. Potassium lactate (3%) or citric acid (0.5%, 0.56%, 0.60% or 0.66%) was added to pork sticks to determine their effects on microbial growth, sensory evaluation, and shelf life when stored frozen (-20°C), refrigerated (2°C), or at room temperature (22°C). Two raw materials, pork blade meat (shoulder meat; 91% lean, 9% fat) and regular 80:20 pork trim (80% lean, 20% fat) were used. The consumer panel preferred lean pork sticks made from blade meat over high-fat pork sticks made from regular 80:20 …

Properties Of Low-Fat Yogurt Made From Ultrafiltered And Ultra-High Temperature Treated Milk, Richard Alan Dargan

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Yogurts were made from intermediate-high temperature (100, 110, 120, and 130°C for 4 or 16 s), ultra-high temperature (140°C for 4 or 16 s), and vat heat (82°C for 20 min) treatments of skim milk fortified to 5% protein by either ultrafiltration or the addition of nonfat dry milk (NDM). Whey protein denaturation in heated milks increased with temperature and holding time from indirect plate heating and was highest in vat-heated milks. Whey protein denaturation and yogurt water-holding capacity increased with protein levels in the fortified milks compared to skim milk. Penetrometer gel strength and stirred viscosity in 21 day-old …

Zeta-Potential Of Casein Micelles As A Factor In Age Gelation Of Ultra-High Temperature Processed Concentrated Skim Milk, Douglas W. Olson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The effect of ultra-high temperature processing by direct steam injection and room temperature storage of pH-adjusted and unadjusted 3X (volume reduction) skim milk retentate and the effect of storage at various temperatures of 3X skim milk retentate without pH adjustment on their ζ-potential, viscosity, and pH were determined. Pasteurized skim milk was concentrated to 3X by ultrafiltration. In the pH study portions of skim milk retentate were adjusted to pH 6.38 ± .02 with HCl and 6.85 ± .01 and 7.32 ± .02 with NaOH between ultrafiltration and ultra-high temperature processing. In the storage temperature study, storage temperatures used for …

Characterization Of Pigments Responsible For Red Or Pink Discoloration In Cooked Pork, Viswasrao M. Ghorpade

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The pigments responsible for pink or red discoloration in cooked vacuum-packaged meat products {bratwurst (pork and beef), ground pork, and pork roasts} were investigated. In bratwurst, this study attempted to characterize the red pigment that appears upon refrigerated storage, and to determine the effect of pH, cooking and storage temperature, and sodium lactate on incidence of red discoloration. Myoglobin was identified in the exudate of samples with red discoloration. Myoglobin levels of cooked products were significantly lower in samples of low initial pH (5.5) or cooked to higher than normal internal temperature (74°C). Red discoloration was associated with microbial growth. …

Influence Of Process Parameters In The Manufacture Of Cottage Cheese Curd From Ultrafiltered Skim Milk, Ronald Michael Raynes

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A processing procedure for the manufacture of directly acidified cottage cheese curd from 16% total solids ultrafiltered retentate was developed. The effects of preacidification of skim milk before ultrafiltration and heat treatment of retentate were investigated to improve the functional and sensory qualities of retentate curd.

Retentate directly acidified with phosphoric acid and glucono-delta-lactone to pH 4.7 formed a dense, rubbery curd that could not be handled well in a vat. A heat treatment of 71.1°C for 30 min applied to the retentate resulted in a curd with acceptable handling properties. However, this heat treatment caused the curd to shift …

Estimation Of Selected Milk Protein Genetic Variants By Multi-Component Analysis Of Amino Acid Profiles, Carol M. Hollar

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Cation-exchange fast protein liquid chromatography separated whole casein into β-casein A², A¹, and B, K-casein, α_s1-casein, and α_s2-casein fractions as well as γ-caseins and several unidentified peaks using a urea-acetate buffer at pH 5 and a NaCl gradient. The whole casein fractions eluted in the following order: breakdown products of β-casein and unidentified peaks; β-casein A², A^l, and B; additional breakdown products of β-casein and unidentified peaks; K-casein; α_s1-casein; and α_s2-casein. The calculated composition of the four major caseins correlated well with values obtained …

A Low-Temperature Scanning Electron Microscopy Study Of Ice Cream. Ii. Influence Of Selected Ingredients And Processes, K. B. Caldwell, H. D. Goff, D. W. Stanley

Food Structure

The objective of this study was to examine the influence of processing parameters, viz., incorporation of polysaccharide stabilizers, freezing rates, and storage times and temperatures on the microstructure of ice cream. As the freezing rate was reduced, ice crystals and air bubbles increased in size. However, quenchfreezing also contributed to poor texture; thus an optimum freezing rate exists for the production of suitably- sized ice crystals and texture in ice cream. Model systems of polysaccharide stabilizer solutions were seen to have a characteristic network structure when quenchfrozen which was altered by the addition of sucrose. Stabilized ice cream initially had …

Effect Of Draw Ph On The Development Of Curd Structure During The Manufacture Of Mozzarella Cheese, L. J. Kiely, P. S. Kindstedt, G. M. Hendricks, J. E. Levis, J. J. Yun, D. M. Barbano

Food Structure

The impact of varying the pH of whey at whey drainage (5.9, 6.15 or 6.4) on the development of curd structure during the manufacture of Mozzarella cheese was investigated using scanning electron microscopy. Dramatic changes in curd structure were apparent with stage of manufacture , in particular the stretching step which aligned the protein fibers.

Of additional interest is the effect of draw pH on the structure of curd at whey drainage. When whey was drained at pH 6.4, an open poorly fused network of paracasein particles was observed in the cheese curd. Jn contrast, lowering the draw pH (6.15 …

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

Food Structure

Cherimoya (Annona cherimola Mill.) is an important fruit crop that is grown in the South of Spain. Ultrastructural modifications of cherimoya fruit were studied after low-temperature storage. When cherimoya was stored at 4 oc for 6 days, the starch grains did not suffer degradation and the cell walls remained intact. The membrane systems were severely damaged , result ing in a loss of cell compartmentalization. Cherimoya rewarmed to 22 0 C after 9 days of low temperature storage is not able to recover , showing the irreversibility of the ultra structural changes. In addition, disorgani zation of the internal lamella …