Agriculture Reference
In-Depth Information
Controlled and modified atmospheres
The keeping quality of fresh herbs is improved under
conditions of reduced O
2
and elevated levels of CO
2
, and
so fresh and pureéd herbs may be sealed under modified
atmospheres (MA) during packing, although the
technique is not widely used for fresh herbs because of
their relatively short post-harvest life (Aharoni
et al
.
1993; Saltveit 1997). The value of modified atmospheres
is somewhat degraded if packs are sold in illuminated
display cabinets, since these increase photosynthesis and
may reduce CO
2
, making it difficult to sustain the
modified atmosphere within the pack and so reducing the
quality of the contents. Modified atmosphere packaging
will lengthen the shelf life of coriander (Loaiza &
Cantwell 1997), chervil (Aharoni
et al
. 1993) fennel
(Artés
et al
. 2000) and basil (Lange & Cameron 1998),
and CO
2
and gibberellic acid combinations have been
assessed on parsley (Lers
et al
. 1998).
Fresh herbs may be bought pure or in mixed packs, in
cellophane bags or trays, and sold on refrigerated display
cabinets. They are marketed as
bouquet garni
and as
components of bags of mixed
Cruciferae
(e.g. rocket, lollo
verde, lollo rossi and cos lettuce or rocket, coriander, chive,
spinach and baby leaf). Pack weights of mixed herbs range
from 90 to 120 g. Fresh herbs may also be sold as separate
leaves or bunches in MA bags or trays (e.g. coriander,
parsley, sage, rosemary, mint and basil) in which case
weights are smaller at 12-15 g per pack. They may also be
marketed as small, rooted plants in pots (such as chives,
thyme, parsley and coriander) at room temperature.
Dried herbs and spices are usually sold pre-packed in
small quantities (1-12 g) in supermarkets or convenience
stores, or loose by weight in traditional markets.
Puréed formulations are a relatively recent introduction to
the marketplace. Herb concentrations in these formulations
range from 40% to 60% with syrups, emulsifiers, stabilizers
and flavourings comprising the balance. In the puréed form
the product is packed in plastic squeezable tubes in modified
atmospheres with a pack weight of 110-120 g. If kept
refrigerated a shelf life of three to four months is possible,
with an extra six months if the tubes are frozen.
Ethylene
Ethylene production is low in fresh herbs but sensitivity
to the gas can be high (Wright 2002b). As shown in
Table 15.5, ethylene will affect some herbs causing leaf
yellowing, leaf drop and epinasty. Many herbs exhibit
epinasty but only the most sensitive species succumb to
yellowing and abscission. These effects can be minimised
by careful control of storage temperatures, preferably
maintained at 0°C (Cantwell 1997; Cantwell & Reid
1993), except for basil. MA packaging would also
reduce the effect of ethylene.
An alternative approach involves the inhibition of
ethylene action using 1-methylcyclopropene (1-MCP).
Regulation of senescence in coriander leaves using 1-MCP
has been reported by Jiang
et al
. (2002).
Insects
Insect contamination in spices is not usually of concern,
though some products are subject to post-harvest insect
attack. For example, the drugstore beetle (
Stegobium pani-
ceum
(L.) ) and the cigarette beetle (
Lasioderma serricorne
(Fab.) ) can cause problems on dried herbs and chillies
(Berke & Shieh 2001). Also on chillies, the mite
Curimosphena villosa
(Haag-Rutenberg) has been reported
from Ethiopia and
Cryptolestes
spp. beetles from Thailand
(Haynes 1991).
Lasioderma serricorne
and
Caulophilus oryzae
(Gyllenhal) have been found on ginger from the West
Indies and
Gnatocerus cornutus
(F.) on ginger in Africa.
The nitidulid beetle
Lasiodactylus tibialis
Boheman were
reported on cloves from Madagascar and
Caryedon
serratus
(Olivier) and
Sitophilus linearis
(Herbst) on
tamarind pods. In Sri Lanka
Cryptolestes klapperichi
Lefkovich and beetles of the family Scolytidae have been
found on nutmeg. In addition, the moths
Ephestia cautella
(Walker) and
Corcyra cephalonica
(Stainton), and the
beetles
S. linearis
,
Tribolium castaneum
(Herbst),
Oryzaephilus surinamensis
(L.),
Henoticus californius
(Mannerheim),
Araecerus fasciculatus
(Degeer) and
Necrobia rufipes
(Degeer) have all been found on spices
but are not considered as major pests (Haines 1991). These
insects can be controlled by fumigation.
Handling and packing
The leaves of fresh herbs can be easily bruised by rough
handling, particularly mint, basil and coriander, because
they are of relatively low mechanical strength. Sites of the
damage may provide entry for pathogens, thus speeding up
decay, but will in any case lead to discolouration, yellowing
and browning. Careful handling and rigid packaging will
limit this type of damage. Thus bags of fresh herbs may be
further protected by being packed in waxed cartons of
corrugated card or plastic boxes. Much work has been done
recently on modified atmosphere packaging; increased use
of and improvements in intelligent packaging solutions
such as ethylene and moisture absorbers have increased the
shelf life of fresh produce by 50% in the United Kingdom
over the last decade (Anon. 2003).
