Physical Modification Processes

Heat treatment of milk has been one of the most common methods used to alter its functionality. Other processing treatments such as the alteration of pH, mineral adjustment, or homogenization or a combination of these can affect the physical functionality of milk. Processes used in the production of dried dairy ingredients also can influence their fimctional properties, particularly in the manufacture of powders with high protein content. 

Increasing pH above the natural pH of milk markedly accelerates the rate of denaturation of p-lactoglobulin. The denatured whey proteins associate with the casein micelles or remain in the serum phase as complexes of denatured whey proteins or denatured whey protein in association with K-casein. 

Generally a decrease in the pH of milk systems prior to heating results in more association of the denatured whey proteins to the casein micelle (Corredig and Dalgleish, 1996 Oldfield et al., 2000 Vasbinder and de Kruif, 2003). Even small changes in pH can shift the distribution of the association of the denatured whey protein with the casein micelle. For example, at a level of 95% whey protein denaturation, there is 70% of the denatured whey proteins associated with the casein micelle at pH 6.55 and this is decreased to 30% when the pH of milk prior to heating was 

Characterization of the aggregates in heated milk revealed that the serum aggregates are mainly disulphide-linked complexes of whey protein and K-casein (Jean et al., 2006). Increasing the pH of milk from 6.5 to 

2 produces smaller aggregates with a higher content of K-casein (Renan et al., 2006). In contrast to the whey proteins, caseins are more stable to heat. However, at high temperatures for long times (120-150 °C up to 60 min), there is aggregation, fragmentation, and dephosphorylation of casein and destruction of some amino acids (Guo et al., 1989). 

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The mechanical properties of composites are mainly influenced by the adhesion between matrix and fibers of the composite. As it is known from glass fibers, the adhesion properties could be changed by pretreatments of fibers. So special process, chemical and physical modification methods were developed. Moisture repel-lency, resistance to environmental effects, and, not at least, the mechanical properties are improved by these treatments. Various applications for natural fibers as reinforcement in plastics are encouraged. 

Unnecessary derivatization (use of blocking groups, protection/de-protection, and temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste. 

The band gap energy of modified catalysts decreased down to 1.6 eV, and the basic structure and physical properties of the catalysts were not changed during modification process. All of the synthesized Ti02 were anatase structure but commercial Ti02 were contained 30% rutile structure. However, the catalytic activity of modified catalysts using two different Ti02 were almost the same in this reaction conditions. 

Modification, which involves the alteration of the physical and chemical characteristics of the native potato starch to improve its fimctional characteristics, can be used to tailor it to specific food applications. The rate and efficacy of any starch modification process depend on the botanical origin of the starch and on the size and structure of its granules. This also includes the surface structure of the granules, which encompasses the outer and iimer surface depending on the pores and channels, which cause the development of the so-called specific surface (Juszczak, 2003). Potato starch modification can be achieved in three different ways physical, conversion, and chemical (derivatization) (Table 10.6). 

Substrate Treatment. When the desired image is developed in the resist, the pattern created provides a template for substrate modification. The various chemical and physical modifications currently used can be classified into additive and subtractive treatments. Examples of additive treatments include the insertion of dopants (by either diffusion or ion implantation) to alter the semiconductor characteristics and metal deposition (followed by lift-off or electroplating) to complete a conduction network. In most cases, however, the substrate material is etched by a subtractive process. 

This book emphasizes chemical conversions, which may be defined as chemical reactions applied to industrial processing. The basic chemistry will be set forth along with easy-to-understand descriptions, since the nature of the chemical reaction will be emphasized in order to assist in the understanding of reactor type and design. An outline is presented of the production of a range of chemicals from starting materials into useful products. These chemical products are used both as consumer goods and as intermediates for further chemical and physical modification to yield consumer products. 

Modification of zeolites, based on chemisorption of silane or diborane and subsequent hydrolysis of the chemisorbed hydride groups can also be applied for encapsulating gas molecules in zeolites. For example, krypton and xenon can be encapsulated in mordenite combining the modification process with a physical adsorption of the noble gases at moderate pressures and temperatures (e.g. 100 kPa, 300 K). The encapsulates are homogeneous and stable towards acids, mechanical grinding and y-irradiation. By controlling the pore size reduction however, the thermal stability can be controlled. 

For all these reasons, most of the acoustical energy involved in generating the cavities and in their collapse is ultimately spent in decomposing water into H2 and 02. This is the main factor affecting sonochemical efficiency (i.e., the ratio between the rate of the reaction of interest and the applied power density, W/L). In order to improve the efficiency of a sonochemical process, chemical or physical modifications can be introduced into the system, which may reduce this loss (see Sec. IV.G). The efficiency can also be affected by the presence of other chemicals in the solution, which may react with the radicals, thus reducing the number of reactive species available to the target molecules. A preprocess might be conceived to separate some of these unwanted chemicals from the solution prior to sonochemical treatment. 

A variety of physical treatments are used to alter food starches, including heat with or without moisture, radiation and mechanical processing. These treatments provide improved processability or improved texture and stability.79 Moreover, physical modification (e.g. pregelatinization) may be used, as well as chemical modification for maximum overall performance. The following sections review the types of physical modification used or described for use in foods. A discussion of control of flow will be followed by a review of pregelatinization and physical modifications intended to otherwise alter starch performance. 

The whey produced during cheese and casein manufacturing contains approximately 20% of all milk proteins. It represents a rich and varied mixture of secreted proteins with wide-ranging chemical, physical and functional properties (Smithers et al., 1996). Due to their beneficial functional properties, whey proteins are used as ingredients in many industrial food products (Cheftel and Lorient, 1982). According to Kinsella and Whitehead (1989), functional properties of foods can be explained by the relation of the intrinsic properties of the proteins (amino acid composition and disposition, flexibility, net charge, molecular size, conformation, hydrophobicity, etc.), and various extrinsic factors (method of preparation and storage, temperature, pH, modification process, etc.). 

This chapter is focussed on the post-farm modification of milk fat by physical, chemical or enzymic means. The use and control of these processes for differentiation of milk fat to widen its application range or tailor it for specific end-applications (Mortensen, 1983 Mogensen, 1985 Boudreau and Arul, 1991 Rajah and Burgess, 1991) will be discussed. The effects of the modification processes and minor lipid components on the texture and crystallization behavior of milk fat are covered. The potential for applying modification processes to improve the nutritional quality of milk fat is also considered. 

Milk fat may be chemically modified to obtain products with altered functionality. In contrast to physical modification of milk fat where the position and nature of the fatty acid chains of the triacylglycerols are maintained, the use of chemical processes results in modification of the composition of the fatty acid chains or their positions in the triacylglycerol molecule. 

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