Commercial Purification And Synthesis Of Aas

101 Toxic Food Ingredients

101 Toxic Food Ingredients

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The isolation of protein from natural sources began as early as 1747 when Beccari reported on the isolation of gluten from wheat flour.2 However, the discovery of specific AAs started in 1806 with the isolation of asparagine from asparagus shoots. By 1935, with the isolation of threonine, all of the AAs commonly found in natural proteins had been isolated. The industrial production of isolated AAs began in 1909 when L-glutamic acid was first extracted from a hydrolysate of g

CO OH

CO OH

Tryptophan (Trp, W)

Tryptophan (Trp, W)

ol c

COOH

Methionine (Met, M)

COOH

Phenylalanine (Phe, F)

COOH

Isoleucine (Ile, I)

COOH

FIGURE 15.2 Non-polar AAs. Illustration, Irving Geis; Garrett RH, Grisham CM, Biochemistry, 3rd ed, Belmont, CA: Thomson Brooks/Cole, 2005. Rights owned by Howard Hughes Medical Institute. Not to be reproduced without permission.

Ki CO

COOH

Asparagine (Asn. N)

Asparagine (Asn. N)

COOH

Threonine (Thr. T)

COOH

Cysteine (Cys. C)

COOH

Thyrosine (Tyr. Y)

COOH

HjN-C-H

H NV/NH

Histidine (His, H)

HjN-C-H

HjN-C-H

Glutamine (Gin. Q)

FIGURE 15.3 Polar, uncharged AAs. Illustration, Irving Geis; Garrett RH, Grisham CM, Biochemistry, 3rd ed, Belmont, CA: Thomson Brooks/Cole, 2005. Rights owned by Howard Hughes Medical Institute. Not to be reproduced without permission.

COOH

HaN-C-H

COOH

Aspartic acid (Asp, D)

COOH

CH2 COOH

Glutamic acid (Glu, E)

FIGURE 15.4 Two acidic AAs. Illustration, Irving Geis; Garrett RH, Grisham CM, Biochemistry, 3rd ed, Belmont, CA: Thomson Brooks/Cole, 2005. Rights owned by Howard Hughes Medical Institute. Not to be reproduced without permission.

FIGURE 15.5 Basic AAs. Illustration, Irving Geis; Garrett RH, Grisham CM, Biochemistry, 3rd ed, Belmont, CA: Thomson Brooks/Cole, 2005. Rights owned by Howard Hughes Medical Institute. Not to be reproduced without permission.

TABLE 15.1

Classification of Essentiality

Essential Nonessential

Isoleucine

Leucine

Lysine

Methionine

Phenylalanine

Threonine

Tryptophan

Valine

Alanine Asparagine Aspartic acid Cysteine Glutamic acid

Glutamine

Glycine

Proline

Serine

Tyrosine

Semi-Essentiala

ARG Histidine a Due to their rate of synthesis within the body, ARG and histidine are considered semi-essential AAs. It appears that these AAs cannot be synthesized by the body at a rate that will support growth (especially in children).

From Spruce, N., Apex Fitness Group Certification Manual, 4th ed., p. 15. Reprinted with permission of Apex Fitness Group, Camarillo, CA, 2003.

wheat gluten. This marked the beginning of marketing the sodium salt of L-glutamic acid (monosodium glutamate) for use as a flavor enhancer in Japan. Initially, the major commercial use for isolated AAs was for food flavoring. After 1950, as lower-cost production methods were developed, isolated AAs were used in a variety of new ways such as in pharmaceuticals, animal feeds, and the nutritional enhancement of human foods.3

A variety of methods have been developed to produce isolated AAs. For industrial production, the method used is determined primarily by cost efficiency. Four methods are utilized and reviewed briefly in the following subsections.3

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