BIOTROPIA No. 10, 1997 : 42-62

THE EFFECTS OF MILLING DEGREE AND TYPE OF BAG

ON FUNGAL INFECTION AND SOME CHEMICAL CONTENTS

OF STORED MILLED RICE

OKKY SETYAWATI DHARMAPUTRA

SEAMEOBIOTROP, P.O. Box 116, Bogor, Indonesia, and
Department of Biology, Faculty of Mathematics and Natural Sciences, Bogor Agricultural University,

Bogor, Indonesia

ABSTRACT

The effects of milling degree and type of bag on fungal infection of stored milled rice were investigated together
with some chemical contents (glucose, amylose, p rotein and total lipid contents), and changes in moisture content.

Rice var. IR 64 with different milling degrees (85, 90, 95 and 100%) packed in jute and polypropylene bags (1 kg
of milled rice/bag) were stored under laboratory conditions with temperature between 24.3-27.3 C and relative humidity
52.6-81.9% for 3 months. The initial moisture content (m.c.) of milled rice was ± 14%. Three replications (3 bags) were
used for each treatment. Each bag was put individually and was arranged randomly on a wooden pallet.

The results showed that in general, the increase of milling degree and duration of storage decreased the m.c. Type
of bag did not give significant differences on the m.c.

Twenty eight fungal species were isolated from rice with different milling de gree and bag type during storage. The
predominant species was Aspergillus Candidas. Total fungal population decreased with the increase of milling degree
and duration of storage. Bag type did not give significant differences on total fungal population.

In general, the increase of milling degree increased glucose content. Glucose content in milled rice packed in jute
bag was higher than that in polypropylene bag. Glucose content tended to decrease with the increase of storage duration.

The increase of milling degree increased amylose content in milled rice. Amylose content of milled rice packed in
jute bag was lower than that in polypropylene bag. The increase of storage duration decreased amylose content in milled
rice.

In general, protein content decreased with the increase of milling degree and duration of storage. 1 type did not give
significant differences on protein content.

Total lipid content decreased with the increase of milling degree and duration of storage. Total lipid content of
milled rice packed in jute bag was lower than that in polypropylene bag, but based on chemical analysis the difference
was not significant.

Based on statistical analyses, correlation between the m.c. and total lipid content with total fungal population was
positive. There was no correlation between glucose, amylose and protein contents with total fungal population.

Rice with high milling degree can be stored safely for long period, but it has low chemical (nutritional) contents.

Key words: Milling degree/Bag type/Fungal infection/Chemical content/Milled rice.

INTRODUCTION

Rice (Oryza saliva L.) is the primary foodcrop in Indonesia. The National Logistics Agency

(BULOG) buys and stores a large amount of milled rice as national stock to maintain price

stability.

The effects of milling degree and type of bag on fungal infection - Okky Setyawad Dhannaputra

During storage rice could be infested by insects, mites, microorganisms and rodents.

Among the microorganisms, fungi are the most important cause of deterioration of stored

products (Christensen and Kaufmann 1974).

The tropical climate of Indonesia provides a favourable condition for fungal growth.

According to Garraway and Evans (1984) the development of fungi was affected by the

nutritional content of the substrate.

The degree of milling is one of the physical characters of rice that may influence the

fungal development. Another factor that may affect the fungal development is the type of bag

used to store milled rice.

The objective of the study is to get information on the effects of milling degrees and bag

types on moisture content, fungal population, and some chemical contents (glucose, amylose,

protein and total lipid) of milled rice during 3 months of storage.

MATERIALS AND METHODS

Rice variety, milling degree, bag type, and storing of milled rice

Rice var. IR 64 was used in this study, because it is widely cultivated in Indonesia. The paddy

was obtained from Food Technology Research and Training Centre (Balai Penelitian Teknologi

Pangan) BULOG, Tambun, and it was stored for 2 weeks from the harvest time.

The paddy was milled with different milling degrees, i.e. 85, 90, 95 and 100%. Rice with 85%

milling degree was enclosed by 15% of bran layer and embryo, while rice with 100% milling degree

was die rice that had neither bran layer nor embryo (Juliano 1972; BULOG 1994). Two types of bag

were used, i.e. jute and polypropylene bags.

Rice with milling degree of 85, 90, 95 and 100% were stored in jute and polypropylene bags (1

kg/bag) under laboratory conditions for 3 months. The initial moisture content of milled rice was

± 1 4 % . Before storage rice was fumigated with phos-phine at dosage rates 2 g/tonne of rice for 6

days. Three replications (3 bags) were used for each treatment. Each bag was arranged randomly on

a wooden pallet (Figure 1). During storage the temperature and the relative humidity of the storage

were recorded using a thermohygrograph.

Obtaining working samples

Initial samples were obtained from each replication (bag) of treatment at the beginning of

storage, and then at 1, 2 and 3 months of storage. A sample from each bag was divided using a

sample divider into 4 sub samples for (1) moisture content analysis, (2) fungal analysis, (3) some

chemical content analyses, and (4) reserve sample.

Figure 1. Milled rice packed in jute (a) and polypropylene (b) bags, and arranged randomly on a wooden pallet.

Moisture content, fungal and chemical content analyses

Moisture content was determined using an oven method (BSI 1980). Fungi were

isolated using dilution method on Dichloran 18% Glycerol Agar (DG 18) (Pitt and

Hocking 1985). The glucose, amylose, protein and total lipid contents were determined

using modified Anthrone, Williams, Kjeldahl and Soxhlet extraction methods, respectively

(Yoshida et al. 1976).

Identification of the fungi

Fungal identification was carried out according to Samson et al. (1984), Pitt and

Hocking (1985).

Experimental data were analysed using Completely Randomized Factorial Design

with 3 factors. The 1st, 2nd, and 3rd factors were milling degree, type of bag, and duration of

storage, respectively.

RESULTS AND DISCUSSIONS

Moisture content

Moisture content (m.c.) is the most important factor in determining the development of

microorganism, insect and chemical reaction hi stored products (Muir 1973; Sinha 1973).

BIOTROPIA No. 10, 1997

The effects of milling degree and type of bag on fungal infection - Okky Setyawati Dharmaputra

Based on statistical analysis, milling degree, duration of storage, interaction be tween bag

types and duration of storage, interaction among milling degree, bag types and duration of storage

gave very significant differences on the m.c., while interaction between milling degree and bag type

was significantly different. Type of bag and interaction between milling degree and duration of

storage were not significantly different.

The increase of milling degree decreases the m.c. (Table 1). The m.c of rice with 85, 90, 95,

and 100% milling degree were 14.18, 14.04, 13.91 and 13.73%, respectively.

Table 1. The effect of milling degree, duration of storage, interaction between milling degree and bag type, interaction
between bag type and duration of storage, and interaction among milling degree, bag type, and duration of storage
on moisture content of rice

According to Dharmaputra et al. (1993) the increase in milling degree increased the m.c. of milled
rice that was stored under laboratory conditions for 3 months with temperature of 25 ± 2 C and

relative humidity (RH) of 80 ± 5%. In this study the result was not the same; the increase of milling

degree decreased the m.c. It was assumed that the milled rice was stored at higher temperature
(24.3-27.3 C) and lower RH (52.6-81.9%) (Table 2).

BIOTROPIA No. 10, 1997

Table 2. Range of temperature and relative humidity at storage condition

The endosperm and the embryo of milled rice were enclosed by bran layer. The layer
consists of pericarp, legmen and aleuron (Figure 2). The three layers contain more lipid
and protein than the endosperm, while the latter contains more carbohydrate. The
higher milling degree causes the higher loss of the three layers. Water could be easily
bound by carbohydrate compared to lipid or protein. It was assumed that the high
temperature and the low RH during storage caused the evaporation of water in the grain.

Although the pores of polypropylene bag was smaller than jute bag, type of bag did
not give a significant difference on the m.c. It was assumed that only one bag (with 1 kg
of rice) was put on the wooden pallet, so that air circulation did not affect the m.c. of rice.

Figure 2. Structure of the rice grain (cited from Grist, 1969).

The effects of milling degree and type of bag on fungal infection - Okky Setyawati Dharmaputra

During storage the m.c. of rice decreased, although the m.c. of rice at 2 months of storage was

not significantly different from that at 3 months of storage (Table 1). This was probably because of

the higher temperature and the lower RH during storage.

The lowest m.c. was found in rice with milling degree of 100% packed in polypropylene bag at

2 months of storage (13.39%); while the highest was in rice with milling degree of 85% packed in jute

and polypropylene bags at the beginning of storage (14.59% respectively).

Species and fungal population

Twenty eight species of fungi were isolated from rice with different milling degrees

and bag types during storage. They were Aspergillus candidus, A. flavus, A. fumigatus, A.

niger, A. oryiae, A. penicilloides, A. sydowii, A. terreus, A. versicolor, A. wentii, Cladosporium

cladosporioides, Curvularia lunala, Eurotium chevalieri, E. repens, Endomyces fibuliger,

Fusarium moniliforme, Nigrospora oryzae, Paecilomyces varotii, Penicillium sp. nr.

adametzioides, P. chrysogenum, P. citrinum, P. corylo-philum, P. herquei, P. islandicum, P.

raistrickii, Rhizopus microsporus, Synce-palastrum racemosum and Wallemia sebi. The

predominant fungus was A. candidus. It was assumed that the m.c. of milled rice during storage was

suitable for its growth, or the fungus was able to compete with other fungal species in colonizing the

substrate.

Among the above species, there were some species of field fungi i.e. Cladosporium

cladosporioides, Curvularia lunata, F. moniliforme, and N. oryzae. It was assumed that the

fungi infected the grain before harvest and they survived during storage. According to Christensen

and Kaufmann (1969) field fungi need m.c. in equilibrium with the high RH (90%) or more for their

growth.

The presence of each fungal species on rice with different milling degree during storage is

presented in Table 3. A. candidus, C. cladosporioides and P.. citrinum were always isolated, while

A. flavus and E. chevalieri were often isolated.

Most of the fungi isolated belong to genera Aspergillus, Eurotium, and Penicillium.

According to Christensen and Kaufmann (1974) fungi that belong to genera Aspergillus and

Penicillium caused deterioration in grain during storage. Pitt and Hocking (1985) reported that

Eurotium is a teleomorph stage of Aspergillus which is a xerophilic fungus.

Based on statistical analysis, milling degree, duration of storage, and interaction between

milling degree and duration of storage gave very significant differences on total fungal population,

while bag type, interaction between milling degree and bag type, interaction between bag type and

duration of storage, and interaction among milling degree, bag type, and duration of storage were

not significantly different.

BIOTROPIA No. 10, 1997

Table 3. The presence of each fungal species on rice with different milling degree during storage

Total fungal population (transformed into log x) on rice with milling degree of 85, 90,
95 and 100% during 3 months of storage were 2.94, 2.50, 2.08 and 1,73 colonies/g,
respectively (Table 4). Total fungal population decreased with the increase of milling degree.
The total fungal population was related to the nutritional content of the rice. Protein, lipid,
some organic acids, and vitamins decreased with the increase of milling degree. They are
micro and macro-elements needed for fungal growth. According to Juliano (1972) the
nutritional content of the rice with high milling degree was low because the outer layer of the
rice was removed during milling, consequently a part of the nutrition found in this layer was
lost.

The effects of milling degree and type of bag on fungal infection - Okky Setyawati Dharmaputra

Table 4. The effect of milling degree, bag type, duration of storage, and interaction between milling degree and duration of
storage on total fungal population of nee

Type of bag did not give a significant difference on the total fungal population (Table 4).

The m.c. is the environmental factor in determining the fungal growth and type of bag did not give

a significant difference on it, so that the bag type did not also give a significant difference on total

fungal population.

Total fungal population decreased with the increase of storage duration (Table 4). The total

fungal population (transformed into log x) at the beginning of storage was significantly different

from that at 1, 2 and 3 months of storage, while after 2 and 3 months of storage they were not

significantly different, although their population tended to decrease. The decrease of total fungal

population was presumably related to the decrease of nutritional and moisture contents in rice.

The total fungal population (not transformed into log x) at the beginning of storage, and at 1, 2 and
3 months of storage were 650.48, 410.79, 390.15 and 183.81 colonies/g, respectively.

The lowest total fungal population was found in rice with milling degree of 100% after 3

months of storage (32.17 colonies/g), while the highest was in rice with milling degree of 85% at

the beginning of storage (1505.92 colonies/g).

Fungi in rice with milling degree of 85%

BULOG (1994) determined that rice with 85% milling degree was enclosed by 15% of bran

layer and embryo.

Twenty four fungal species were isolated from rice with 85% milling degree at the beginning

of storage, and at 1, 2, and 3 months of storage. They were Aspergillus candidus, A. flavus, A.

fumigatus, A. niger, A. oryzae, A. penicilloides, A. sydowii, A. versicolor, A. wentii,

Cladosporium dadosporioides, Curvularia lunata, Eurotium

BIOTROPIA No. 10, 1997

chevalieri, E. repens, Endomyces fibuliger, Fusarium moniliforme, Nigrospora oryzae,

Penicillium sp. nr. adametzioides, P. chrysogenum, P. citrinum, P. herquei, P. raistrickii,

Rhizopus microsporus, Syncephalastrum racemosum and Wallemia sebi. Population of each

fungal species is presented in Table 5.

Fungal species at the beginning of storage, and at 1, 2, and 3 months of storage were

dominated by A. candidus with the population of 1474.33, 947.67, 1045.59 and 372.09

colonies/g, respectively.

Fungi in rice with milling degree of 90%

BULOG (1994) determined that rice with 90% milling degree was enclosed by 10% of

bran layer and embryo.

Twenty one fungal species were isolated from rice with 90% milling degree at the

beginning of storage, and at 1, 2, and 3 months of storage. They were Aspergillus candidus, A.
flavus, A. fumigatus, A. penicilloides, A. sydowii, A. terreus, A. ver-sicolor, Cladosporium

dadosporioides, Curvularia lunata, Eurotium chevalieri, E. re-pens, Endomyces fibuliger,

Nigrospora oryzae, Paecilomyces varotii, Penicillium sp, nr. adametzioides, P. chrysogenum,

P. citrinum, P. islandicum, P. raistrickii, Rhizopus microsporus and Syncephalastrum

racemosum. Population of each fungal species is presented in Table 5.

Fungal species at the beginning of storage, and at 1, 2, and 3 months of storage were

dominated by A. candidus with the population of 656.08, 332.41, 355.83 and 84.67

colonies/g, respectively.

Dharmaputra (1994) reported that milled rice with the same variety (IR 64) and milling

degree (90%) stored for 3 months under laboratory conditions (in jars), was infected by

eleven fungal species i.e. A. candidus, A. flavus, A. niger, A. penicilloides, A. versicolor, A.

wentii, C. dadosporioides, E. chevalieri, E. repens, P. citrinum and P. herquei. The

predominant species was A. flavus. The difference in fungal species that infected milled

rice was presumably due to the difference of location where the paddy was cultivated.

Fungi in rice with milling degree of 95%

BULOG (1994) determined that rice with 95% milling degree was enclosed by 5% of

bran layer and embryo.

Twenty two fungal species were isolated from rice with 95% milling degree at the

beginning of storage, and at 1, 2, and 3 months of storage. They were Aspergillus candidus, A.

flavus, A. fumigatus, A. oryzae, A. penicilloides, A. sydowii, A. terreus,

The effects of milting degree and type of bag on fungal infection - Okky Setyawati Dharmapuera

BIOTROPIA No. 10, 1997

A. versicolor, Cladosporium cladosporioides, Curvularia lunata, Eurotium chevalieri,

Endomyces fibuliger, Fusarium moniliforme, Nigrospora oryzae, Paecilomyces varotii,

Penicillium sp. nr. adametzioides, P. chrysogenum, P. citrinum, P. islandicum, P. raistrickii,

Rhizopus microsporus and Syncephalastrum racemosum. Population of each fungal species is

presented in Table 5.

Fungal species at the beginning of storage, and at 1, 2, and 3 months of storage were

dominated by A. Candidas with the population of 211.50, 95.17, 125.00 and 50.25

colonies/g, respectively.

Fungi in rice with milling degree of 100%

Rice with 100% milling degree had neither bran layer nor embryo. It had only an

endosperm (Juliano 1972; BULOG 1994).

Eighteen fungal species were isolated from rice with 100% milling degree at the

beginning of storage, and at 1, 2, and 3 months of storage. They were Aspergillus Candidas,

A. flavus, A. fumigatus, A. niger, A. oryzae, A. penicilloides, A. sydowii, A, versicolor, A. wentii,

Cladosporium cladosporioides, Curvularia lunata, Eurotium chevalieri, Fusarium

moniliforme, Nigrospora oryzae, Penicillium sp. nr. adametzioides, P. citrinum, P.

corylophilum, and P. raistrickii, Population of each fungal species is presented in Table 5.

Fungal species at the beginning of storage, and at 1, 2, and 3 months of storage were

dominated by A. Candidas with the population of 84.17, 41.34, 35.75 and 19.34 colonies/g,

respectively.

Glucose content

Most of fungi use glucose (D-glucose) for their growth (Moore-Landecker 1982). Glucose

is a form of monosaccharide with six carbon atoms (hexose). Mono -saccharide is considered as

carbohydrate which cannot be hydrolized into a simple form and has a very simple bond compared

to polysaccharide. Consequently, their chemical bond can be easily separated by enzymes

compared to amylose, a polysaccharide which has a more complex chemical bond than

monosaccharide (Mayes 1981).

Based on statistical analysis, milling degree, bag type, duration of storage, interacti on

between milling degree and bag type, and interaction among milling degree, bag type and

duration of storage gave very significant differences on the glucose content, while interaction

between milling degree and duration of storage was no! significantly different. Interaction

between bag type and duration of storage was noi significantly different.

The effects of milling degree and type of bag on fungal infection - Okky Setyawati Dharmaputra

Glucose content increased with the increase of milling degree (Table 6). The higher

milling degree caused the higher loss of the bran layer and embryo. Therefore, the percentage

(w/w) of glucose content in rice with high milling degree was higher than that of low milling

degree. Glucose content on rice with milling degree of 85, 90, 95 and 100% were 2.99, 3.50,

3.27 and 3.41%, respectively.

Milled rice packed in jute bag had glucose content higher than packed in polypropylene

bag. It was assumed that total fungal population in milled rice packed in jute bag was lower

than in polypropylene bag, although based on statistical analysis it was not significantly different

(Table 4).

Glucose content tended to decrease with the increase of storage duration. It was attributed

that the glucose was used for the fungal growth (Moore-Landecker 1982) and as energy source

for grain respiration (Pomeranz 1992). Glucose content at the beginning and one month of

storage were significantly different from that at 2 and 3 months of storage. The glucose

content of milled rice at the beginning of storage, and at 1, 2, and 3 months of storage were 3.74,

3.86, 2.84 and 2.73%, respectively.

Table 6. The effect of milling degree, bag type, duration of storage, interaction between milling degree and bag type,
interaction between nulling degree and duration of storage, and interaction among milling degree, bag type and
duration of storage on glucose content of rice.

Milling Bag
degree ( % ) type

Glucose content ( % )
Duration of storage (month)

85 Jute

3.29uvw

3.85 stu

2.57 wx

2.56 wx

3.07 ij
Polypropylene

3.29 uvw

3.66 stu

2.23 x

2.47 z

2.91 j

3.29 mno

3.76 kiln

2.40 r

2.52 qr

2.99 a
90 Jute

3.78 stu

3.79 stu

4.06 st

3.43 tuv

3.78 g
Polypropylene

3.78 stu

3.68 stu

2.84 vwx

2.61 wx

3.23 ij

3.78 kl

3.74 klm

3.45 lmn

3.02 nop

3.50 b
95 Jute

3.94 stu

3.43 tuv

2.47 x

2.78 vwx

3.15ij
Polypropylene

3.94 stu

4.30 st

2.69 wx

2.61 wx

3. 38 hi

3.94 kl

3.86kl

2.58 pqr

2.69 pqr

3.27 ab
100 Jute

3.94 stu

4.89s

2.94 vwx

2.87 vwx

3.66 gh
Polypropylene

3.94 stu

3.24 uvw

2.93 vwx

2.50 x

2.15ij

3.94 kl

4.06k

2.93 opq

2.68 pqr

3.41 b
y Jute

3.41c
Polypropylene

3.17d

3.74 e

3.86e

2.84 f

2.73 f

—

Numbers followed by the same letter do not differ significantly according to Tukey Multiple Range Test at
95% confidence level
*Not significantly different

BIOTROPIA No. 10, 1997

The highest glucose content was found in rice with milling degree of 100% packed in
jute bag at one month of storage (4.89%), while the lowest was in rice with milling degree of

85% packed in polypropylene bag at 2 months of storage (2.23%).

Although a sugar other than glucose may give maximum growth of a fungus, it appears
that the more closely the configuration of a sugar resembles glucose, the more fungi use it. This

might be due to the ability of a fungus to use a particular sugar depending on how easy it can

be converted into a phosphorylated derivative of glucose which can enter the respiratory

pathways (Moore-Landecker 1982).

Amylose content

Most of the carbohydrate found in rice is in the form of starch (90% of dry weight) and

only a very small part is in the form of hemicellulose, cellulose and some free sugars such as

sucrose, raffinose, glucose and fructose (Juliano 1972).

Starch is a polysaccharide that can be separated into two fractions depending on their

ability to dissolve hi water, that is amylose (± 20%) and amylopectin (± 80%) (Mayes 1981).

Juliano (1972) reported that based on dry weight, the amylose content of milled rice was

between 7-33% depending on rice variety.

Based on statistical analysis, milling degree and duration of storage gave very significant

differences on the amylose content, while bag type gave a significant difference. Interaction

between milling degree and bag type, interaction between milling degree and duration of storage,

interaction between bag type and duration of storage, and interaction among milling degree, bag

type and duration of storage did not give significant differences.

The increase of milling degree increased amylose content (w/w) in milled rice. The

amylose content of milled rice with milling degree of 85, 90, 95 and 100% were 23.84, 23.99.

24.98 and 25.50%, respectively (Table 7).

Amylose content of milled rice packed in jute bag (24.09%) was lower than that in

polypropylene bag (25.07%). It was assumed that the pores of jute bag was bigger than that of

polypropylene bag, so that the air surrounding jute bag could make easier to hydrolize the

amylose to form maltose or glucose.

The increase of storage duration decreased amylose content in milled rice. The amylose

content at the beginning of storage, and at 1, 2 and 3 months of storage were 26.72, 25.40, 24.29

and 21.90%, respectively. Presumably the phenomena was due to the activities of (3-amylase and

fungal enzymes which infected the molecule a-glucans and supported the hydrolization of

amylose to disaccharide and mono- saccharide.

The effects of milling degree and type of bag on fungal infection - Okky Setyawati Dharmaputra

Table 7. The effect of milling degree, bag type, and duration of storage on amylose content of rice

Amylose content ( % )

Milling Bag

Duration of storage (month)

degree (%) type

23.84 a
90

23.99 ab
95

24.98 be
100

25.50 c
y Jute

24.09 d
Polypropylene

25.07 e

26.72 f

25.40 g

24.29 h

21.90i

Numbers followed by the same letter do not differ significantly according to Tukey Multiple Range Test a t
95% confidence level
* Not significantly different

Protein content

Rice is one of the cereals which contains a higher percentage of lysine (± 4%) than other
cereals. Lysine is an essential amino acid which is found in very small quantities in other food stuff
(Juliano et al. 1973).

Brown rice contained ± 8% protein, 75% carbohydrate and a small amount of lipid, fibre and
ash, while milled rice contained ±7% protein (Juliano 1976).

Based on statistical analysis, milling degree and duration of storage gave very significant
differences on the protein content, while interaction between milling degree and duration of
storage was significantly different. Bag type, interaction between milling degree and bag type,
interaction between bag type and duration of storage, and in teraction among milling degree, bag
type and duration of storage did not give significant differences.

The protein content tended to decrease with the increase of milling degree and duration of
storage (Table 8). The protein content in rice with milling degree of 85 and 100% during 3 months
of storage were significantly different. They were 9.14 and 8.84%, respectively. According to
Juliano (1972) the decrease of milling degree decreased the nutritional content (including protein).
Dharmaputra et al. (1993) reported that total protein in milled rice var. Cisadane decreased with
the increase of milling degree.

At the beginning of storage the protein content in milled rice was 9.44%, and then decreased
to 9.18% at 3 months of storage. Dharmaputra et al. (1993) reported that the increase of storage
duration decreased the protein content in milled rice.

BIOTROPIA No. 10, 1997

Table 8. The effect of milling degree, duration of storage, and interaction between milling degree and duration of storage on
protein content of rice

According to Sinha and Muir (1973), the decrease of protein content may also
be caused by degradation of amino acid and non-protein nitrogen such as vitamin B

and phospholipid. .

The lowest protein content was found in rice with milling degree of 100% after 1 month

of storage (8.28%), while the highest was in rice with milling degree of 90% at the beginning of

storage (9.77%).

In general, the increase of milling degree and duration of storage decreased the protein

content hi milled rice.

Total lipid content

According to Juliano (1976), brown rice contained ±1.9% lipid, while milled

rice contained ± 0.5% lipid. Pomeranz (1974) reported that lipid was convened into

free fatty acid and glycerol with the aid of lipase enzyme during storage. T his con

version was accelerated with the existence of storage fungi because the fungi have high

ly poly tic activity.

Based on statistical analysis, milling degree, duration of storage, and interaction between

milling degree and duration of storage gave very significant differences on the total lipid content,

while bag type and interaction among milling degree, bag type and duration of storage gave

significant differences. Interaction between milling degree and bag type, and interaction between

bag type and duration of storage did not give significant differences.

Total lipid content decreased with the increase of milling degree and duration of storage

(Table 9). Total lipid content in milled rice with milling degree of 85, 90, 95 and 100% were 0.26,

0.23, 0.20 and 0.15%, respectively. Juliano (1972) reported;

The effects of milling degree and type of bag on fungal infection - Okky Setyawati Dharmaputra

Table 9. The effect of milling degree, bag type, duration of storage, interaction between milling degree and duration of stor age,

and interaction among milling degree, bag type and duration of storage on total lipid content of nee

that milling removes the embryo and the bran layer, therefore total lipid found in this pan will
decrease.

Total lipid content of milled rice packed in jute bag (0.20%) was lower than packed in
polypropylene bag (0.21 %), but chemical analysis showed no significant difference.

Total lipid content in milled rice at the beginning of storage, and at 1, 2 and 3 months of

storage were 0.28, 0.25, 0.17 and 0.14%, respectively.

Dharmaputra et al. (1993) reported that the increase of milling degree and du ration of

storage, decreased total lipid content. According to Pomeranz (1992) degra dation of fat or oil in

grains can be affected by several factors, such as 1) oxydative process which gives rancid odour

and taste, and 2) hydrolytic process which results to free fatty acid and glycerol.

The lowest total lipid content was found in rice with milling degree of 100%, packed in jute

bag at 3 months of storage (0.10%), while the highest was in rice with milling degree of 85%,

packed in jute bag and polypropylene bags at the beginning of storage (0.34% respectively).

BIOTROPIA No. 10, 1997

Correlation between moisture content and total fungal population

Based on statistical analysis, the m.c. and total fungal population were positively related

with coefficient correlation (r) = 0.52. The increase of m.c. increased total fungal

population (Figure 3).

Figure 3. Correlation between moisture content and total fungal population on milled rice during storage

Water is required for the growth of fungi just as for other organisms. Fungi usually

require a film of water around their cells through which nutrients and enzyme diffuse

(Garraway and Evans 1984).

Ramakrishna et al. (1993) reported that spore germination and initial growth of fungi

that infected the grain were affected by water activity and temperature of storage.

Correlation between glucose content and total fungal population

Statistical analysis showed no correlation between glucose content and total fungal

population. It was assumed that glucose was not only used for the fungal nutrition, but

also for respiration process of grains (Pomeranz 1992).

The effects of milling degree and type of bag on fungal infection - Okky Setyawati Dbarmaputra

According to Garraway and Evans (1984) glucose is a good carbon source for 4-5

fungal species. Most of the fungal species also used oligosaccharide and polysaccharide

as carbon source.

Correlation between amylose content and total fungal population

Based on statistical analysis, there was no correlation between amylose content and total fungal

population. It was assumed that amylose was hydrolized into disaccharide by fungi-infected milled

rice during storage. In this study twenty eight fungal species were isolated (Table 3). According to

Garraway and Evans (1984) each fungal species may have different enzyme to hydrolize carbon

sources, such as amylose.
1&

Correlation between protein content and total fungal population

Statistical analysis showed no correlation between protein content and total fungal population.

It was assumed that fungi require other nitrogen source for their growth and development. According

to Garraway and Evans (1984) most fungi are able to utilize simple inorganic nitrogen sources as

well as organic sources such as amino acids.

Correlation between total lipid content and total fungal population

Based on statistical analysis, the correlation between total lipid content and total fungal

population was positive with r = 0.64. The increase of total lipid content increased total fungal

population (Figure 4).

Fungi contain a specific enzyme that could hydrolize lipid from the substrate for their

development and growth (Patterson 1989). According to Garraway and Evans (1984), at first fungi

hydrolized lipid with lipase enzyme, then changed them into glycerol through (3-oxidation pathway.

CONCLUSIONS

In this study the increase of milling degree and duration of storage, decreased the m.c. of

rice. The type of bag did not give a significant difference on the m.c.

Twenty eight fungal species were isolated from rice with different milling degree and bag

type during storage. Most of the fungi isolated belong to genera Aspergillus, Eurotium and

Penicillium. The predominant species was A. candidus.

BIOTROPIA No. 10, 1997

Figure 4. Correlation between total lipid content and total fungal population on milled rice during storage.

Total fungal population decreased with the increase of milling degree and duration of

storage. Type of bag did not give a significant difference on the total fungal population.

Glucose content of milled rice increased with the increase of milling degree. When

packed in jute bag the glucose content was higher than packed in polypropylene bag, but it

decreased with the increase of storage duration.

Amylose content of milled rice increased with the increase of milling degree. When

packed in jute bag the amylose content was lower than packed in polypropylene bag, but it

decreased with the increase of storage duration.

Protein content in milled rice tended to decrease with the increase of milling degree

and duration of storage, but it was not affected by bag type.

Total lipid content of milled rice decreased with the increase of milling degree and
duration of storage. When packed in jute bag the lipid content differed significantly than

packed in polypropylene bag, but chemical analysis showed no significant difference.

The effects of milling degree and type of bag on fungal infection - Okky Setyawati Dharmiputn

Rice with low milling degree has high nutritional content, but it cannot be stored for long

period. On the other hand rice with high milling degree has low nutritional content, but it can

be stored for long period.

To get more information on the effect of bag type on fungal infection and chemical

contents of stored milled rice, a research using stack of rice is needed.

ACKNOWLEDGEMENT

The author gratefully acknowledges the financial support of the Government of Indonesia.

Thanks are due to Dr. Haryanto Susilo, Dr. Hariyadi Halid, Dr. Mulyo Sidik, Mr. Amad and Mrs.

Asmarina S.R. Putri for their valuable assistance, and to Dr. A.D. Hocking from CSIRO, Australia,

for the confirmation of fungal identification.

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