Life Sciences Commons^™

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 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 …

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 …

The Adsorption Of Crystalline Fat To The Air-Water Interface Of Whipped Cream, B. E. Brooker

Food Structure

The interfacial structure of air bubbles in normal and defective whipped creams were compared, using freeze fracturing and transmission electron microscopy , in an attempt to understand the underlying mechanism of t he observed gross differences in their whipping times and overruns . In normal whipped creams sparsely distributed fat crystals were found to have penetrated some of the bubbles and were lying in the plane of the air/water interface.

In defective whipped creams , large numbers of needle-like crystals had penetrated the air/water interface of every bubble and, as a consequence, reduced numbers of fat globules were found to …

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

Food Structure

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

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

Food Structure

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

Structure And Properties Of The Particulate Constituents Of Human Milk. A Review., M. Ruegg, B. Blanc

Food Structure

Milk contains different types of colloidal or coarsely dispersed particles, such as casein micelles, membrane fragments, fat globules and cells. The fat globules are composed of subpopulations of differently sized particles. In contrast to COW 1S milk, the overall average diameter (dys), increases with advancing lactation from about 1.8 ~min colostrum to 4.0 ~min mature milk. Membrane materials originating from the milk fat globule membrane, plasma membrane, secretory vesicles and other sources can be found in milk serum. These particles have also been called lipoprotein particles. Their size ranges from about 10 - 400 nm. New results concerning the structure …