Journal of Stored Products Research 43 (2007) 118–122
Studies on insect infestation in chocolates
Khamrunissa Begum, P. Vanitha Reddy, B.C. Leelaja, Y. Rajashekar, S. Rajendran
Food Protectants and Infestation Control Department, Central Food Technological Research Institute, Mysore 570020, India
Accepted 22 February 2006
The ability of stored-product pests including the cigarette beetle, Lasioderma serricorne, the sawtoothed grain beetle, Oryzaephilus
surinamensis, the rust-red ﬂour beetle, Tribolium castaneum, and the almond moth, Ephestia cautella, to infest chocolates under packaged
and unpackaged conditions was investigated in the laboratory at 25711C and 6575% r.h. Four types of chocolates were investigated:
milk, nut, dried fruit and nut, and wafer chocolates. Adults (beetles only, 20 per replicate) or eggs (30 per replicate) were released on
unpackaged and packaged chocolates and infestation levels (number of living adults and larvae) were determined 45 days later. When
adult beetles were released on unpackaged chocolates, the degree of infestation varied depending on the species and the type of chocolate.
The highest infestation observed in unpackaged chocolate was that of O. surinamensis in wafer chocolate (mean 138.4). When eggs were
released on unpackaged chocolates, the most numerous species was E. cautella in dried fruit and nut chocolate (mean
population ¼180.8). With packaged chocolates exposed to adults or eggs, insect infestation was nil or negligible (mean population
o6.0). Although infestation levels were low, infestations were found in 50% of treatments over all. Damage to the packaging material
along the folds or edges was observed in infested chocolates. The study has shown that milk, nut, dried fruit and nut, and wafer
chocolates can support insect infestation and therefore, insect-proof packing of the chocolates and storage under hygienic conditions are
important to avoid customers’ complaints.
r2006 Elsevier Ltd. All rights reserved.
Keywords: Chocolates; Insect infestation; Ephestia cautella;Oryzaephilus surinamensis;Lasioderma serricorne;Tribolium castaneum
Chocolate products in many forms and ﬂavours are
relished by people of all ages for their sweetness and
richness in nutrition. The global confectionery market
including chocolate products has been estimated to exceed
$73.2 billion per annum and the annual global consump-
tion of chocolate confectionery has been estimated as 6.5
million tonnes (CAOBISCO, 2004). Chocolate is prepared
from a mixture of one or more of the following ingredients:
cocoa bean/ nib/ press cake, cocoa dust, sugars, cocoa
butter, milk solids and ﬂavouring agents. Depending on its
composition, chocolate is known as plain chocolate, milk
chocolate, white chocolate, blended chocolate, bitter
chocolate or composite chocolate. Cocoa, the basic
ingredient in these chocolates varies from 20% to 60%.
The type of packaging material used for chocolates varies;
generally, aluminium foil, composite ﬁlms, paper or plastic
trays are used. The packaged chocolates are known to keep
their quality up to 5 months when stored at 10–18 1C and
60–70% r.h. The actual storage period, however, may
extend for a longer duration in the distribution network/
Insect infestation in chocolates may occur at any stage
from production to consumption. Insect infestations in and
around chocolate manufacturing facilities have been
reported in some countries (Bowditch and Madden, 1997;
Wohlgemuth, 1992). It is recommended that chocolate
products are stored in hygienic conditions in well-
ventilated locations at 18–20 1C and o50% r.h. (ICCO,
2000). In the retail market, however, hygiene varies and
accordingly the products are prone to infestation. When
insects are found in the chocolates, consumers often direct
their complaints to the manufacturer and the image of
the company is affected (Highland, 1984). Customers’
ARTICLE IN PRESS
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Corresponding author. Tel.: +91 821 2513210; fax: +91 821 2517233.
E-mail address: firstname.lastname@example.org (S. Rajendran).
complaints about insect infestation in chocolates in the
retail market in both developed and developing countries
have been reported (Scheurer and Dubau, 1999).
Data on the infestability of different types of chocolates
under packaged and unpackaged conditions by insect pests
are lacking. Experiments, therefore, were conducted to
study the infestability of different types of chocolates under
packaged and unpackaged conditions by four common
stored-product insect pests viz., the rust-red ﬂour beetle,
Tribolium castaneum (Herbst),the sawtoothed grain beetle,
Oryzaephilus surinamensis (L.), the cigarette beetle, Lasio-
derma serricorne (L.), and the almond moth, Ephestia
cautella (Walker), over a storage period of 45 days.
2. Materials and methods
Milk chocolate (ingredients: milk solids, cocoa butter,
cocoa solids, sugar, emulsiﬁers etc.), nut chocolate
(ingredients: almonds+other ingredients as in milk choco-
late), dried fruit and nut chocolate (ingredients: raisins,
cashew nuts, apricot kernels+other ingredients as in milk
chocolates) and wafer chocolate (ingredients: wheat ﬂour,
hydrogenated vegetable oil, edible starches+other ingre-
dients as in milk chocolates) of the same brand were
obtained from the local market. The type of packaging
material used on the chocolates and their unit weight
varied. The chocolates were not checked for damage or
defects in the packaging materials prior to use in the
experiment. The moisture content of the chocolates as
determined by the toluene distillation method ranged from
1.1% to 3.2% (Table 1).
Tribolium castaneum and L. serricorne cultures were
maintained on whole wheat ﬂour+5% yeast, O. surina-
mensis on broken wheat+rolled oats+yeast at a 5:5:1 ratio
and E. cautella on broken wheat+5% yeast+5% glycerol
in the laboratory at 25711C and 6575% r.h. From these
cultures, unsexed 1–2 week old adults of T. castaneum and
O. surinamensis and 2–3 day old adults of L. serricorne
were taken for infestation studies. For the collection of
eggs of T. castaneum, L. serricorne and O. surinamensis,
wheat ﬂour was passed through an 85-mesh standard sieve
(pore size 180 mm). Into the sieved ﬂour (200 g) c. 250
adults were released for oviposition for 48 h. At the end of
48 h, the adults were removed from the ﬂour using standard
25- or 44- mesh sieves (pore sizes 600 and 335 mm,
respectively). The ﬂour was subsequently sieved through
an 85-mesh sieve to separate the eggs, which were then
placed on the chocolates. To collect E. cautella eggs, newly
emerged adults were released into a metal cage having a
mesh bottom, which allows eggs to pass through. Eggs,
0–2 days old, were collected in a tray under the cage and
then placed on the chocolates. Viability of eggs of
individual species was checked as described in Rajendran
et al. (2004). Eggs (four replicates per species) were placed
individually in the wells of ELISA plates that were cut
into half so as to have only 48 wells and egg hatch was
observed under a binocular microscope, daily, until there
were no more emergences. Viability (% hatched) of eggs
was: T. castaneum (91.075.9), L. serricorne (79.2712.3),
O. surinamensis (86.877.8), and E. cautella (76.1714.5).
2.3. Infestation studies
The studies were carried out on chocolates (70–84 g per
replicate) under packaged conditions as well as without any
packaging materials. Chocolates were placed in bottles
(size 13 cm 9 cm) for 45 days at 25711Cand6575% r.h.
There were 2 sets of experiments. In the ﬁrst set, adults (20
per replicate) were released on to chocolates with and
without packaging material. In the second set, 1–2 day old
eggs (30 per replicate) of the individual species were placed
on both unpackaged and packaged chocolates. There were
5 replicates for each type of chocolate. After the addition of
insects, the bottles containing chocolates and reference
diets were covered with pieces of cloth, tied with rubber
bands and held at 25711C for 45 days. At the end of 45
days, insect populations (live larvae and adults) in
chocolates were recorded. In packaged chocolates, when-
ever infestation was found, the packaging materials of the
ARTICLE IN PRESS
Details of the types of chocolates used for the experiments
Chocolate type Unit weight (g) Moisture content
Packaging material used
Milk chocolate 42 1.1 12 mm foil/25 mm polyethylene Printed paper
Nut chocolate 35 2.8 25 mm biaxially oriented
Dried fruit and nut chocolate 80 3.2 12 mm foil/25 mm polyethylene Printed paper
Wafer chocolate 15 2.4 Nil 12.5 mm polyethylene
17.5 mm biaxially oriented
K. Begum et al. / Journal of Stored Products Research 43 (2007) 118–122 119
chocolates were examined for the presence of damage or
2.4. Data analysis
Data on insect populations in the four types of
chocolates were transformed to logarithmic (for unpack-
aged chocolates) or O(x+0.5) (for packaged chocolates)
values and subjected to ANOVA followed by Duncan’s
New Multiple Range test to determine signiﬁcant differ-
ences in infestation (of the individual species) between
In unpackaged chocolates, all four species could infest
but the degree of infestation varied between chocolate
types and insect species (Table 2). In general, populations
were greatest in dried fruit and nut chocolate. Where adults
were released in the chocolates, O. surinamensis (average
counts, 52–138) and L. serricorne (45–86) populations were
higher than T. castaneum (12–23). Oryzaephilus surinamen-
sis infestation levels in the chocolates were: waferodried
fruit and nutomilk ¼nut. No signiﬁcant differences in the
levels of T. castaneum and L. serricorne infestation between
chocolate types were observed.
When eggs were used, high population levels of
E. cautella (180.8750.9) were noted in dried fruit and
nut chocolate. Among the beetle pests, high average counts
were recorded of O. surinamensis (5–27) and L. serricorne
(6–17). The levels of infestation when eggs of
O. surinamensis were placed in unpackaged chocolates
was: dried fruit and nutomilk ¼nut ¼wafer, whereas, for
L. serricorne as well as T. castaneum the infestation levels
were: milk ¼nut ¼dried fruit and nutowafer.
With packaged chocolates exposed to adults or eggs,
insect infestations were nil in 50% of the treatments and in
the remaining treatments very low infestation levels (mean
populationo6.0) were observed (Table 3). No signiﬁcant
differences in the level of infestation between species and
between chocolate types were noted. No infestations were
found from T. castaneum adults released on wafer or nut
chocolates nor from eggs of either O. surinamensis or
E. cautella in dried fruit and nut, nut or wafer chocolates.
Damage to inner or primary packaging material (12 mm
foil/ 25 mm polyethylene) along the folds or edges was
observed in milk and dried fruit and nut chocolates infested
with the adults of O. surinamensis as well as L. serricorne
and with the eggs of E. cautella. Damage to the packaging
material (12.5 mm polyethylene terephthalate/metallization/
17.5 mm biaxially oriented polypropylene) along the seal
was also noticed in wafer chocolate infested with the adults
of O. surinamensis.
Stored-product insects have different food preferences.
Chocolates contain various ingredients such as cocoa, tree
nuts, dried fruits and wheat ﬂour that are favourable for
the growth and multiplication of insects. Lasioderma
serricorne is a major pest on cocoa and cocoa products
and can breed readily in all four types of chocolates in
addition to tobacco. Oryzaephilus surinamensis, a common
pest on processed foods and tree nuts, also breeds readily
on chocolates (Table 2). The omnivorous T. castaneum,
however, produced only low-level populations in the
chocolates tested. Population levels of E. cautella, a pest
on a variety of foodstuffs including cereals, cereal
products, cocoa, oilseeds, tree nuts and dried fruits were
ARTICLE IN PRESS
Populations of Tribolium castaneum,Lasioderma serricorne,Oryzaephilus surinamensis and Ephestia cautella in unpackaged chocolates at the end of a
45-day storage period at 25711C
Insect No. of insects (mean7SD) recorded in different types of chocolates
Milk Nut Dried fruit and nut Wafer
Tribolium castaneum 23.078.7ax 17.4713.3ax 22.8710.8ax 11.672.6ax
Lasioderma serricorne 58.2723.0bx 45.2712.3bx 86.0715.5bx 79.0775.6bx
Oryzaephilus surinamensis 53.275.0bx 52.076.0bx 95.6720.3by 138.4722.5cz
Tribolium castaneum 9.274.7aby 10.678.2ay 11.674.2ay 3.673.7ax
Lasioderma serricorne 16.075.1by 11.277.7ay 17.472.8aby 6.274.9ax
Oryzaephilus surinamensis 6.876.0ax 8.477.4ax 27.4710.0by 5.475.4ax
Ephestia cautella 18.674.1bx 71.6745.4by 180.8750.9cz 14.876.2bx
20 adults per each of 5 replicates released.
30 eggs per each of 5 replicates released.
Means in the same column of adults or eggs followed by different letters (a, b, c) differ signiﬁcantly according to Duncan’s new multiple range test
Means in the same row of adults or eggs followed by different letter (x, y, z) differ signiﬁcantly according to Duncan’s new multiple range test
K. Begum et al. / Journal of Stored Products Research 43 (2007) 118–122120
high on the chocolates particularly in fruit and nut as well
as nut chocolates.
The susceptibility of the ingredients used in chocolate
manufacture to insect pests such as E. cautella and the
Indian meal moth, Plodia interpunctella (Hu
¨bner) has been
studied (Locatelli and Garavaglia, 1995). It was noted that
raw hazel nuts used in the manufacture of chocolates were
more susceptible than the basic ingredients of the
Insect infestation in chocolates may depend on (1)
storage conditions, (2) storage temperature, (3) type and
thickness of the packaging materials, and (4) storage period
(Collins, 2003). The extent of infestation also depends on
the insect pest complex occurring in the premises. The
storage period of manufactured chocolates generally varies
from 3–6 months in the retail market. During longer
storage, more insects are likely to invade or penetrate the
packaging material causing more damage to the choco-
lates. The longer storage period facilitates insect develop-
ment to a life stage, i.e., larva or adult that is capable of
damaging the packaging material and/or the insects have
sufﬁcient time to chew or damage the packaging material
(Kelly, 2004). Rapid turnover of the stocks will discourage
insect pest attack during storage (Anonymous, 1984).
Packaging plays an important role in maintaining the
shelf life of chocolates and as a physical barrier against the
entry of insect pests. The penetrability of the packaging
material by insect pests varies between species and among
the active stages of a particular species (Cline, 1978).
Stored-product insects have been classiﬁed as invaders and
penetrators of packed foodstuffs. Invaders (e.g. adults as
well as larvae of O. surinamensis) can gain entry into
the product through pinholes/punctures or imperfect
sealing, whereas penetrators (e.g. adults of L. serricorne,
larvae of E. cautella) with powerful mouthparts can
pierce or damage the packaging materials. In the current
study, damage to the packaging material along the folds or
edges due to insects (O. surinamensis, L. serricorne and
E. cautella) was noticed. In the present experiment on
packaged chocolates, out of a total 28 treatment combina-
tions, 50% of treatments had at least one infested replicate
(Table 3). Although infestation levels were low, any
infestation is important from a retailer or customer’s point
While examining the barrier properties of different
packaging materials that were used for chocolate products,
Schmidt (1979) observed that even aluminium foil was not
100% insect proof. In the present study, insects could
penetrate along the folds or edges of 12 mm aluminium foil
combined with 25 mm polyethylene packaging material in
milk and dried fruit and nut chocolates. Insect pests could
gain entry into the packaged products through minute
holes and defective sealing of the packaging material.
Sealing defects are likely to occur during manufacture of
chocolates. For the entry of insects (adults or larvae),
depending on the species, minute holes ranging from 560 to
1700 mm are enough for penetration (Cline and Highland,
1981). Due to variations in the extent of damage/defects in
the packaging materials of the four types of chocolates and
invasion potential of individual insect species, infestation in
packaged chocolates was sporadic in the present study
Food aroma/volatiles escaping from defective sealing or
damaged packaging material may attract insects for
oviposition or feeding. In laboratory studies, Mowery et
al. (2002) showed that female adults of O. surinamensis
were attracted towards packaged products for oviposition.
In another study, it was noted that E. cautella females were
attracted towards the grain odour, which stimulated their
oviposition (Barrer and Jay, 1980). In laboratory tests on
insect resistance to packaging materials, it was shown that
P. interpunctella, an important pest on chocolate products,
could distinguish sealed packets with and without food
items for oviposition (Mullen, 1994).
ARTICLE IN PRESS
Populations of Tribolium castaneum,Lasioderma serricorne,Oryzaephilus surinamensis and Ephestia cautella in packaged chocolates at the end of a 45 days
storage period at 25711C
Insect No. of insects (mean7SD) recorded in different types of chocolates
Milk Nut Dried fruit and nut Wafer
Tribolium castaneum 0.871.1 0 3.678.0 0
Lasioderma serricorne 0 0.270.4 1.671.8 5.479.9
Oryzaephilus surinamensis 5.8713.0 0 0.671.3 1.072.2
Tribolium castaneum 1.872.2 0.270.4 0 0
Lasioderma serricorne 0 0 0.871.8 0.470.9
Oryzaephilus surinamensis 0.270.4 0 0 0
Ephestia cautella 1.873.6 0 0 0
No signiﬁcant differences were observed between columns or rows of adults or eggs according to Duncan’s new multiple test (Po0.05).
20 adults per each of ﬁve replicates released.
30 eggs per each of ﬁve replicates released.
K. Begum et al. / Journal of Stored Products Research 43 (2007) 118–122 121
Insects such as T. castaneum (24 days as adults and 9–12
days as larvae) and L. serricorne (9 days as adults as well as
larvae) are highly tolerant of starvation (Cline, 1978;
Koura and El-Halfawy, 1973). Starved insects have a
greater tendency to attack packed products than normal
insects. In laboratory tests it was observed that starved
larvae are more aggressive in penetrating into the packa-
ging material (Cline, 1978). Therefore, in the absence of
any other food commodities, insects present in the vicinity
of chocolates would be more likely to penetrate the
packaging material of the products. In the present study
it was noted that a few adults of T. castaneum survived
during the storage period (45 days) probably by feeding on
the packaging material of the chocolates.
Chocolates have ingredients such as cocoa, tree nuts and
dried fruits and therefore are susceptible to insect infesta-
tion during storage. The present study has shown that all
four stored-product species tested could establish different
levels of infestation on four types of chocolates. In
packaged chocolates, however, only negligible levels of
infestation were established. To discourage infestation,
there must be rigorous quality checks on packaging
materials and their sealing during production and the
chocolates must be stored under hygienic conditions away
from infested foodstuffs.
The authors thank the Director, Central Food Techno-
logical Research Institute, Mysore, for encouragement and
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