Functional and Microstructural Effects of Fillers in Comminuted Meat Products

Fillers are used in comminuted meat products such as wieners to increase yield, improve stability, and modify textural properties. Light microscopy, scanning electron microscopy and transmission electron microscopy show that comminutred meat products are mechanical mixtures in which the microstructural features of starch and insoluble protein ingredients are largely retained. The water absorption and gelation properties of these ingredients contribute to the stability and textural firmness. Soluble proteins may improve stability through emulsion formation but the role of emulsion formation i s clearly secondary to that of gelation. The characteristic springy gel structure of wieners is determined by the gelation of myofibrlllar meat prote1ns. Provided the structure of the meat protein gel is not disrupted, fillers will generally increase both textural firmness and stability. Starch and protein fillers have been shown to increase the stability of wiener homogenates prepared at a higher (26 \u27 C) temperature than that which is normally used (16°C) . Light microscopy revealed that the all-meat., wieners had a higher degree of fat agglomeration than did the more stable wieners containing added starch fillers. Electron microscopy revealed that the starch granules participated in the process of physically entrapping the fat globules. Fat globules varied in size and shape, and were observed in environments ranging from low to high protein densities. In surrmary, corrminuted meat pr oducts are shown to have a complex heterogeneous mi crostructure

A Simple Carrier for Freezing Difficult Food Samples in Preparation for Scanning Electron Microscopy

A thin aluminum foil carrier allows several pre-shaped samples to be plunge-frozen simultaneously. The disposable, inexpensive, simple-to-make carrier allows effective freeze-fracture electron microscopy of troublesome samples

Development of Microstructure in Set-Style Nonfat Yogurt - A Review

The development of microstructure in natural set-style nonfat yoghurt was stud i ed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition to thin-sectioning and conventional SEM described in the literature, this review illustrates gelation of milk with micrographs obtai ned by rotary shadowing of casein micelles and their clusters. The existence of void spaces occupied by lactic acid bacteria in yoghurt was con finned by cold-stage SEM of uncoa ted specimens. The microstructure of yoghurt is affected by the preheat treatment of milk, bacterial starter cultures, total solids content , and the presence of thickening agents. The microstructure was found to be related to firnmess and susceptibility to syneresis . Suggestions on the preparation of yoghurt samples for electron microscopy have been included in this review

A Simple Procedure for the Preparation of Stirred Yoghurt for Scanning Electron Microscopy

Stirred yoghurt is aspirated into agar gel tubes having 1.2 mm interior diameter, fixed in glutaraldehyde , dehydrated in ethanol freeze - fractured under liquid nitrogen and critical-point dried. Agar gel encapsulation protects the sample and prevents it from disintegration during the preparative steps. Scanning electron microscopy of the mounted fragments reveals the corpuscular microstructure of this type of yoghurt which develops due to stirring and pumping of the product during manufacture

Sample Holders for Solid and Viscous Foods Compatible with the Hexland Cryotrans CT 1000 Assembly

A brass block., 3 .7 mm high and 10 mm in diameter, which has three openings to accommodate rivet-type or plain tubular specimen holders for scanning electron microscopy at low temperature, has been designed to fit the Hexland Cryotrans CT 1000 assembly in place of the original aluminum disc. Viscous food samples are placed in two-piece tubular holders (0.9 mm inner diameter, 1.2 mm outer diameter) made from sterling silver, and rapidly frozen. The holders are inserted into the brass block under 1 iquid nitrogen and tightened with individual setscrews. A handle screwed into the central hole of the block facilitates manipulation of the block. The samples are fractured inside the Cryotrans CT 1000 assembly by knocking off the part of the sample located in the upper tube. The subsequent operations are the same as those suggested by Hexland. A second simple type of holder has been developed for low-moisture foods, such as cheese, which are resistant to ice crystal formation during freezing . This holder consists of a Hexland aluminum sample disc drilled with a single opening (4.0 mm in diameter) temporarily closed at the bottom with sticky tape. The food is sampled with a cork borer and the sample plug is then inserted into the 4.0 rrm opening, with a rivet covering the part of the sample protruding from the disc. Thermal contact between the sample, the disc, and a rivet that is used to cover the part of the sample protruding from the disc, is provided by Tissue Tek. The sample with the disc is rapidly frozen in nitrogen slush, mounted in the Hexland Cryotrans CT 1000 assembly, and inserted into the prechamber of the cold stage attachment where the rivet is knocked off. From that point on, the regular procedure recommended by Hexland is followed

Effect of Heating to 200 C on Casein Micelles in Milk: A Metal Shadowing and Negative Staining Electron Microscope Study

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

Microstructure and Texture of Khoa

Khoa, a partially dehydrated milk product indigenous to India, was prepared from buffalo milk by boiling it vigorously in an open pan and reducing its volume to approximately 25% within 30 min. The hot semi-solid product (Khoa pat) was held at 20•c for 3 h (fresh, cooled Khoa) or 48 h (swred Khoa); the products were either worked with a pestle in a mortar for 5 min or were left without working. Structural features of Khoa were studied by light microscopy and electron microscopy. Freshly prepared coo led Khoa had a granular structure consisting of protein granules several hundred micrometers in diameter. The granules consisted of intact and partly fused casein micelles and nonmicellar protein . The fresh product was only slightly sandy in the mouth. Large aggregates of lactose crystals developed in the intergranular spaces in unworked Khoa during swrage and sandiness in the stored product was markedly increased. Working reduced the dimensions of the protein granules and the intergranular void spaces and produced large amounts of fat globule membrane fragments. Individual lactose crystals in worked Khoa stored at 20°C for 48 h were more uniformly distributed than in unworked Khoa. Storage did not increase sandiness in the worked product; sensory analysis rated this product to be markedly smoother than unworked stored Khoa. Instrumental measurements showed that working significantly decreased hardness and springiness and increased adhesiveness and, to a smaller extent, cohesiveness