Sweeteners, natural, sources

Although more limited in scope than the BINAP-Ru(II)-catalysed hydrogenations, rhodium-catalysed hydrogenations are of enormous commercial importance because of the demand for both natural and unnatural amino acids on a vast scale. It is even economical for the more expensive of the natural amino acids to be made synthetically rather than isolated from natural sources—phenylalanine, for example, of industrial importance as a component of the artificial sweetener aspartame, is manufactured by enantiosfelective hydrogenation. 

Morris, J.A. (1976). Sweetening agents from natural sources. Lloydia 39, 25-38. 

Phenylalanine (Phe or F) (2-amino-3-phenyl-propanoic acid) is a neutral, aromatic amino acid with the formula HOOCCH(NH2)CH2C6H5. It is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. Tyr and Phe play a significant role not only in protein structure but also as important precursors for thyroid and adrenocortical hormones as well as in the synthesis of neurotransmitters such as dopamine and noradrenaline. The genetic disorder phenylketonuria (PKU) is the inability to metabolize Phe. This is caused by a deficiency of phenylalanine hydroxylase with the result that there is an accumulation of Phe in body fluids. Individuals with this disorder are known as phenylketonurics and must abstain from consumption of Phe. A nonfood source of Phe is the artificial sweetener aspartame (L-aspartyl-L-phenylalanine methyl ester), which is metabolized by the body into several by-products including Phe. The side chain of Phe is immune from side reactions, but during catalytic hydrogenations the aromatic ring can be saturated and converted into a hexahydrophenylalanine residue. ... 

As with the sweetening application our most common need for CO2 removal is from natural gas prior to liquefaction. In this application we are often faced with amounts of oxygen in the feed that may range up to several hundred ppm by volume. The process is often limited to adsorption at a total pressure of about 3 5 bar. In this application however the feed gas is most often pipeline natural gas which gas will have been pre-dried to pipeline standards or about seven pounds (1 lb = 0.45 kg) of water per MMSCF of gas. In some cases the gas source may be other than pipeline and the water load needs to be estimated based on a given mole fraction. The liquefaction process, which runs at -260°F (127°C), demands very low levels of water in the product as well as trace levels of CO2 so that the heat exchangers in the downstream process remain clean. 

Aspartame is unique among the intense sweeteners in that the intake of its component parts can be compared with intakes of the same substances from natural foods. It is clear that the consumption of aspartame represents only a minor source of aspartic acid, phenylalanine or methanol in the diet. (SCF, 2002)... 

Depending on source, geographic location, and the extent of extraction, the acid gas content of fuel gases often exceeds pipeline specifications. Certain natural gases and landfill gases can contain up to 50% carbon dioxide. Bulk removal of both carbon dioxide and hydrogen sulfide from such sources, i.e., the process of sweetening, not only improves the fuel value of the gas, but also helps reduce corrosion of pipelines and transmission equipment. Membranes are suitable for this application especially where the scale is relatively small and the economics favor scalable membrane systems. 

Pilnik, W. and Vervelde, G.J., Jerusalem artichoke (Helianthus tuberosus L.) as a source of fructose, a natural alternative sweetener, Z. Ackerund Pflanzenbau, 142, 153-162, 1976. 

Recently, much attention has been given to the production of liquid sweeteners as an alternative to cane sugar using inexpensive starch-containing natural materials as the primary feed stock. This situation exists in the United States as this country is not self sufficient in the production of cane, but must rely heavily on importation mainly from South America and the Caribbean. The main source of sta rch in the United States comes from corn (Zea mays) and the liquid sweetener commercially produced from this material is called high fructose corn syrup (HFCS). The current method of production of HFCS is via wet milling which exploits the physical properties of the whole corn constituents (oil, starch, gluten, and fiber) for their separation coupled with enzymatic hydrolysis of the starch fraction to monosaccharides. 

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