Microstructural Studies in Fat Research

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 of emulsifiers at interfaces between oil and water. In this context , the displacement, at a planar interface, of sodium caseinate by low-molecular mass emulsifiers such as monoacylglycerols and phospholipids has been studied. It appears that saturated monoacylglycerols are more active in displacing the protein than unsaturated monoacylglycerols. With phospholipids, complicated phenomena such as spontaneous emulsification, occur at the oil / water interface . Phospholipids , in general, appear to be much more surface-active than monoacylglycerols. This type of work generates ideas to control and manipulate the microstructure and product properties of fatty products

Structure and Function of Food Products: A Review

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, protein/ protein, protein carbohydrate, and fat crystal/ fat crystal interactions. Finally, it is indicated how these elements cooperate in the formation of structure and contribute to function and macroscopic behavior of food products. Particular attention is given to fat spreads, processed cheese, protein gelation, and examples of the mutual interaction of milk proteins and of carbohydrates with milk proteins. It is expected that a proper understanding of the relation between structure and function will help us to design new ways of structuring in our continuing efforts to manufacture high quality, healthy and tasty food products

Structure Formation in Acid Milk Gels

The structure formation in acid milk gels is influenced by many factors such as heat, salt system, pH, culture and thickening agents. Understanding of the mechanism of structure formation is important in order to be able to influence the final texture of these products. In the present study the network formation in acid milk gels during acidification is monitored by freeze-fracture electron microscopy. Network formation appears to be a much more complex process than just an aggregation of the original milk casein micelles; it is accompanied by subtle dissociation and association phenomena of the milk caseins. The observed sequence of events can be explained from the course of the zeta potential , the association of the beta casein, the release of colloidal calcium phosphate from the micelle, the influence of heat treatment and from some observations on the internal structure of the casein micelle

Microstructure of Shortenings, Margarine and Butter - A Review

Fat spreads are composed of liquid oil, fat crystals and water. The fat crystals in these products give the product the required consistency and stabilize the water droplets. Shortenings are waterfree products , the rheology of which depends on the solid fat content and interactions between fat crystals. Size and interaction between crystals is influenced by both composition and processing. Crystals form a three - dimensional network. Recrystallization phenomena, especially formation of large beta- crystals , can create product defects like sandiness. Margarines and halvarines are water- in - oil emulsions and have a relatively simple product structure. Because of the wettability of fat crystals, part of the solids are present in the water/oil interface, and influence the stability of the emulsion. Depending on the type of application, tropical margarines, table margarines, halvarines , puff-pastry, c reaming margarines, etc. , the ratio of solidlliquid and water content can be varied. No essential differences exist in the microstructure of products for different applications. Butter differs in its microstructure from margarines because of different processing and raw materials. Butter still contains a number of fat globules (derived from the cream) in its final product structure. These globules are dispersed in a matrix of fat crystals and oil desc ending from fat globules that were broken during churning. Also the moisture is present in different forms ranging from droplets to free moisture . Differences in microstructure can be introduced by different processing regimes

Instant polysaccharide-based emulsions: impact of microstructure on lipolysis

The development of emulsion-based products through optimisation of ingredients, reduction in energy-input during manufacture, while fulfilling healthy attributes, are major objectives within the food industry. Instant emulsions can meet these features, but comprehensive studies are necessary to investigate the effect of the initial formulation on the final microstructure and, in turn, on the in vitro lipolysis, comprising the double aim of this work. The instant emulsion is formed within 1.5–3 min after pouring the aqueous phase into the oil phase which contains a mixture of emulsifier (Tween 20), swelling particles (Sephadex) and thickeners (hydroxypropylmethylcellulose, HPMC, and guar gum, GG) under mild shearing (180 rpm). The creation of oil-in-water emulsions is monitored in situ by viscosity analysis, the final microstructure visualised by microscopy and the release of free fatty acids under simulated intestinal conditions quantified by titration. Increasing the concentration and molecular weight (Mw) of GG leads to smaller emulsion droplets due to increased bulk viscosity upon shearing. This droplet size reduction is magnified when increasing the Mw of HPMC or swelling capacity of viscosifying particles. In addition, in the absence of the emulsifier Tween 20, the sole use of high-Mw HPMC is effective in emulsification due to combined increased bulk viscosity and interfacial activity. Hence, optimisation of the ingredient choice and usage level is possible when designing microstructures. Finally, emulsions with larger droplet size (>20 μm) display a slower rate and lower extent of lipolysis, while finer emulsions (droplet size ≤20 μm) exhibit maximum rate and extent profiles. This correlates with the extent of emulsion destabilisation observed under intestinal conditions