Page 129 - Handbook of Properties of Textile and Technical Fibres

Physical, chemical, and tensile properties of cashmere, mohair, alpaca 109

consequence of ultraviolet (UV) irradiation during growth. The proportion of low-
sulfur helix-forming proteins was higher for the cashgora than the cashmere resulting
in a lower ratio of matrix forming to helix-forming proteins (0.28 vs. 0.41).
Only one report was found that investigated the impact of environmental, nutri-
tional, or productivity factors on the amino acid composition and nonfiber components
of cashmere (McGregor and Tucker, 2010). The amino acid composition of cashmere
was affected by energy and protein nutrition of the goats, feed type (grazing compared
with a high-quality high protein herbage diet), and country of origin. The country of
origin significantly affected the content of four amino acids that were higher in cash-
mere from China compared with cashmere from Australia, with the samples from Iran
intermediate between these two origins. The amino acids that were affected by country
of origin were different to the amino acids affected by nutrition and grazing manage-
ment. Cashmere from goats grazed on pasture had five amino acids that were lower and
two that were higher compared with some or all of the cashmere grown by goats
housed indoors and fed high-quality diets. For the cashmere grown by goats fed in-
doors a diet with protected protein, 13 amino acids had higher concentrations and
one amino acid had a lower concentration compared with the cashmere grown by goats
fed the same basal ration indoors but without the protected protein (McGregor and
Tucker, 2010). The tyrosine and phenylalanine content of Australian cashmere was
found to be lower than that of Chinese cashmere and the tyrosine and phenylalanine
content of cashmere was increased by the feeding of protected protein. If the same
mechanisms that operate in wool also operate in cashmere, then Chinese cashmere
and cashmere grown from goats fed high levels of protected protein may have a greater
propensity to yellow when exposed to UV light. This may explain the finding that the
origin of cashmere explains over 50% of the variation in the color of white cashmere,
and that processed Chinese white cashmere had lower lightness and greater yellowness
compared with Australian white cashmere (McGregor, 2000b).

4.2.1.2 Other fibers
Hunter (1993) provides an extensive summary of studies of the amino acid content of
mohair and other chemical comparisons with wool. Tucker et al. (1988) provides
amino acid composition for alpaca, llama, and vicu~ na. Zhang et al. (1994) provide
amino acid content for Chinese mohair. Limited amino acid compositions are available
for yak wool (Yan et al., 1998) and Table 4.1 provides composition for vicu~ na, qiviut,
and bison. Sahajpal and Goyal (2005) differentiated shatoosh (Tibetan Antelope) from
cashmere and angora fiber based on differences in keratin proteins.

4.2.1.3 Lipids and cell membrane complex
Animal fibers possess a chemical-bound (probably monolayer) of fatty acid on the fi-
ber surface. This layer is responsible for the hydrophobic nature of animal fibers and
affects processing behavior, finishing (dyeing) performance, and end-use (aesthetic)
properties such as handle, softness, washing shrinkage etc. Removal of this layer al-
lows specification and control of all surface properties. Early work on this topic was