Volatile composition of red clover (Trifolium pratense L.) forages
in Portugal: The inﬂuence of ripening stage and ensilage
Ricardo Figueiredo, Ana I. Rodrigues
Instituto Nacional de Engenharia, Tecnologia e Inovacßa
o I.P., Estrada do Pacßo do Lumiar, 22, Ed. F, 1649-038 Lisboa, Portugal
Received 27 June 2006; accepted 12 February 2007
The volatile organic compounds (VOCs) of three diﬀerent red clover (Trifolium pratense L.) forages, fresh plant, hay and silage, were
analyzed using GC and GC/MS. Comparing the volatile composition of hay and silage forages of red clover with the corresponding
green plant, the eﬀects of ripening and postharvest secondary metabolism can be noticed in hay and in ensilage. In hay, reductions
of the percentages of alcohols, such as 3-methylbutanol and 1-hexanol, of aldehydes and of low boiling point ketones are observed.
A sesquiterpene (b-farnesene; ca. 10%) and a phytol degradation product (6,10,14-trimethyl-2-pentadecanone; ca. 12%) were the most
abundant compounds detected in hay. In silage, as a result of the fermentation of fresh red clover, esters (ca. 46%) are a more represen-
tative class of compounds.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Red clover; Trifolium pratense L.; Volatile compounds; Hay; Silage
Red clover (Trifolium pratense L.) is a perennial herb,
native in Mediterranean and Red Seas countries. It is used
in rotations for soil improvement and has also some medic-
inal applications, such as cancer, mastitis, joint disorders,
jaundice, bronchitis, spasmodic coughing, asthma, and
skin inﬂammations, e.g. psoriasis and eczema. Isoﬂavone
products isolated from red clover have shown promising
eﬀects on conditions associated with menopause, such as
hot ﬂushes, cardiovascular health and the bone loss associ-
ated with osteoporosis (Atkinson, Compston, Day, Dow-
sett, & Bingham, 2004; Clifton-Bligh, Baber, Fulcher,
Nery, & Moreton, 2001).
However, the main application of red clover is its use as
grazing food for cattle and other livestock. In fact, red clo-
ver is a high quality forage that can be either grazed or used
for hay. The use of this herb has some known advantages:
in the form of hay it has a slightly higher net energy value
and total digestible nutrients than has alfalfa hay (alfalfa
being the most widely used forage in the USA), and two-
thirds its digestible protein; protein in red clover has also
been found to be degraded less extensively in the rumen
than are proteins in other herbs that, like red clover do
not contain condensed tannins (Broderick, Albrecht,
Owens, & Smith, 2004; Owens, Albrecht, Muck, & Duke,
1999). A major disadvantage of preserving forage as hay
is the risk of exposure to adverse weather conditions, since
several days are usually required for drying (Owens et al.,
Ensiling of crops is a popular method for preserving for-
age for animal feed, especially in humid regions (Sullivan,
Hatﬁeld, Thoma, & Samta, 2004). In the early 20th century,
Hunter and Bushnell (1916) referred to the limited literature
involving biological studies of silages at the time. Already
then, the authors wrote that the chemical changes resulting
from fermentation in silage, were caused by enzymes of the
plant cells or microorganisms acting upon the cut forage
plant. Two dependent processes were, therefore, involved
0308-8146/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
Corresponding author. Tel.: +351 217168100; fax: +351 210924749.
E-mail address: firstname.lastname@example.org (A.I. Rodrigues).
Food Chemistry 104 (2007) 1445–1453