Chemical modification of soy

This selective review, which deals primarily with the chemical modification of soy proteins, is further limited to nondestructive chemical reactions which alter physical and biochemical properties of importance in food systems. Soy protein products have been modified by various chemical reactions including (a) treatment with alkalies and adds, (b) acylation, (c) alkylation and esterification, and (d) oxidation and reduction. In most instances these reactions have been applied to heterogeneous protein mixtures containing nonprotein impurities, and often to proteins of unknown prior history. Nonetheless, these reactions indicate that protein functional properties of value in food fabrication can be altered significantly through reaction with chemical reagents. It is recognized that chemically modified proteins must be critically evaluated for food safety. 

Examination of the literature on the chemical modification of proteins and protein-containing products derived from soybeans reveals that the major motivation for such studies was often the development of improved products for industrial rather than food or feed utilization (21, 22, 23, 24). Such research activity was at the heart of the Chemurgic movement begun in the early thirties. Hence it becomes understandable that the patent literature dealing with the chemical modification of soy protein products is much more extensive than the periodical literature. This, together with our imperfect understanding of the basic structure of the soy proteins, explains why many of the reactions cited in this... 

A review of the patent and periodical literature reveals that the intentional chemical modification of soy protein products for food use has received little attention. Such work as has been described is concerned with crude protein-containing fractions and heterogeneous protein mixtures. The full nature and extent of these chemical reactions have not been defined. In spite of the lack of definitive chemical modification studies, there is evidence of the beneficial alteration of gross properties related to potential food use. 

Liu, Y. K. Li. Chemical modification of soy protein for wood adhesives. Macromol. Rapid Commun. 2002,23, 739-742. 

Chemical modification of simple sugars during drying, baking, or roasting operations can either have a desirable or undesirable effect upon the organoleptic quality of the final product. We have become accustomed to the characteristic roasted or baked flavors of coffee, peanuts, popcorn, and freshly-baked bread. The color and flavor and aroma of caramel make it a useful additive for the food industry. On the other hand, the burnt flavor of overheated dry beans or soy milk reduces marketability of these products. 

Improvement in functionality of the major soy globulins can be obtained by structural modification of the proteins. Frequently this is done by chemical modification of the lysine epsilon-amino groups or by alkaline or heat treatment. We have described a procedure for preparation of a superior soy product without alteration of the amino acids (1). 

It is possible to remove the soy bean oil in order to produce a de-oiled lecithin but in confectionery use there is little point in using a de-oiled product. Chemical modification of lecithins is possible but this would cause them to lose their natural status. Another way of modifying the properties is to fractionate the raw lecithin in order to yield products that are richer in one of the components. The resulting products, of course, retain their natural status. 

Coward, L., Smith, M., Kirk, M., and Barnes, S. 1998a. Chemical modification of isflavones in soy foods during cooking and processing. Am. J. Clin, Nutr. 68(suppl) 1486S-1491S. 

The chemical modification of a soy protein can be made by the reaction with some functional groups such as carboxyl or amino groups in the protein. Also a low molecular weight PCL/hexa-methylene diisocyanate (HDI) prepolymer can be used for the modification. 

Another way to increase the phosphatidylcholine content in lecithin is enzymatic transesterification after the addition of choline. Alternatively, modification can be achieved by the addition of free fatty acids, which make the product more fluid. Chemical modification of lecithin (hydrogenation and hydroxylation of the double bonds of fatty acids) is used to increase its stabihty against oxidation. For specific purposes, a phosphohpid concentrate (>90% ofphospho-hpids) is produced by a selective extraction that separates neutral hpids, especially triacylglycerols and free fatty acids. The most important product for industrial purposes is soy lecithin. Its composition is shown in Table 3.33. Rapeseed lecithin and sunflower lecithin have quite a different phosphohpid fraction composition. 

The first soybean protein ingredients made commercially available for food use included full-fat and defatted soy flours and grits (3, 7, 8). These products contain ca. 46-59% protein (NX 6.25) on a moisture-free basis and are available with various heat treatments for specific end-use. Soy protein concentrates and soy protein isolates were introduced into the market about 15 years ago (3, 9, 10, II). By definition soy protein concentrates must contain no less than 70% protein (N X 6.25) and isolates no less than 90% protein (N X 6.25), all on a moisure-free basis. In the past several years there has been much activity in the commercialization of textured soy protein products intended for the extension and replacement of meat. These textured products may be obtained through fiber spinning, shred formation, extrusion, or compaction (12, 13, 14, 15). In addition, soybean milk solids and the heterogeneous proteins in soybean whey might serve as useful substrates in chemical modifications for food use. This short recitation of commercial products illustrates the type of crude protein fractions available for practical modification. Many useful functional properties have been ascribed to these new food proteins. 

It is now evident that acylation with anhydrides (such as acetic and succinic anhydrides) and with lactones (such as -propiolactone) is being proposed (< ) for improving the solubility of soy protein isolates at acidic pH, particularly for the preparation of coffee whiteners. Moreover, this chemical modification has been evaluated for altering the food-use properties of several milk proteins (40), egg protein (41), wheat protein (42), fish protein (43), and single-cell protein (44). 

Primarily small components are linked to polymers by means of chemical synthesis. These monomers, in turn, are either entirely naturally synthesised - as in the case of lactic acid - or are slightly changed by chemical modification as in the case of different epoxydated sunflower, rapeseed, flax, or soy oils. The latter basic components are still reticulated with hardeners obtained with petrochemicals (some products are, e.g.. Tribest of the 3000 row, PTP, or Elastoflex). But also other natural raw materials such as... 

Proteins are natural, renewable, and biodegradable polymers which have attracted considerable attention in recent years in terms of advances in genetic engineering, eco-friendly materials, and novel composite materials based on renewable sources. This chapter reviews the protein structures, their physicochemical properties, their modification and their application, with particular emphasis on soy protein, zein, wheat protein, and casein. Firstly, it presents an overview of the structure, classification, hydration-dehydration, solubility, denaturation, and new concepts on proteins. Secondly, it concentrates on the physical and chemical properties of the four important kinds of proteins. Thirdly, the potential applications of proteins, including films and sheets, adhesives, plastics, blends, and composites, etc. are discussed. 

Method of production soybean processing first the oil and husk are removed, the remaining flakes are subjected to protein extraction pH control permits Isolation of required range of protein molecules next step involves chemical modification, which Imparts required properties grades obtained In this technology include unhydrolyzed grades, hydrolyzed grades, carboxylated soy protein, and proteinates ... 

Soybean oil is an abundant annually renewable resource. It is composed of triglycerides with long chain saturated and unsaturated hitty acids. The presence of these unsaturated tty acids results in poor oxidative stability. However, this enhanced reactivity also allows for chemical modification to introduce new functionalities to the oil. A novel single-step catalytic ozonolysis and in-situ reaction will be described. The reaction proceeds rapidly and efficiently at room temperature in the absence of solvents. The catalytic ozonolysis reaction has been used to reduce the unsaturation in soybean oil, and successfiiliy prepare a number of potentially useful materials such as bio-lubricants with good thermal/oxidative stability, bio-diesel with thermal properties comparable to that of Diesel Fuel 2, and bio-plastic intermediates such as polyols, polyesters, and polyamides. This new class of soy-based materials is competitive both in cost and performance to petroleum based nuterials and offers the added advantage of being environmentally friendly and sustainable. 

The catalytic ozonation process is fairly general and provides us with a broad platform for modifications of vegetable oils. In this article we have used it to enhance the thermal stability of soy-based lubricants, chemically modified soy oil to introduce primary alcohol groups which can then be further condensed to yield polyurethanes and polyester, and to resolve the oxidative and storage stability of biodiesel. 

Soya Proteins. Early attempts to make albumen substitutes from soya protein also ran into problems. A bean flavour tended to appear in the finished product. A solution to these problems has been found. Whipping agents based on enzyme modified soy proteins are now available. The advantage of enzymatic modification is that by appropriate choice of enzymes the protein can be modified in a very controlled way. Chemical treatment would be far less specific. In making these materials the manufacturer has control of the substrate and the enzyme, allowing the final product to be almost made to order. The substrates used are oil-free soy flakes or flour or soy protein concentrate or isolate. The enzymes to use are chosen from a combination of pepsin, papain, ficin, trypsin or bacterial proteases. The substrate will be treated with one or more enzymes under carefully controlled conditions. The finished product is then spray dried. 

Biodiesel (fatty acid methyl ester (FAME)) production is based on transesterification of vegetable oils and fats through the addition of methanol (or other alcohols) and a catalyst, giving glycerol as a by-product (which can be used for cosmetics, medicines and food). Oil-seed crops include rapeseeds, sunflower seeds, soy beans and palm oil seeds, from which the oil is extracted chemically or mechanically. Biodiesel can be used in 5%-20% blends with conventional diesel, or even in pure form, which requires slight modifications in the vehicle. 

The basis for contrast agents derived from nutrional products was Intralipid, which had been prepared from phospholipids obtained from soy bean oil and egg yolk [86]. Intralipid was chemically modified by iodination into Intraiodol, which contained 50 mgl mbThe particles formed in the emulsion were mostly taken up by the hepatocytes and to a lesser extent by the RES [87,88]. Intraiodol was better tolerated than EOE-13 or its precursor, AG 60.99. The addition of cholesterol to Intraiodol resulted in NRI 757 with an iodine concentration of 42 mg mL b Further modifications by replacing the iodinated triglycerides of Intraiodol by ethiodized poppy seed oil and reducing the cholesterol content to... 

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