Fungal Infection and Toxigenicity Aspergillus flavus Isolated from

Cacao and Coffee Beans in North Sumatera

Kiki Nurtjahja, Liana Dwi Sri Hastuti, Atika Nurfalah and Ramayani

Department of Biology, Faculty of Science and Technology, Universitas Medan Area, Medan, Indonesia

Keywords: Cacao, Collector chain, Fungal infection, Aspergillus flavus

Abstract: Cacao (Theobroma cacao) and coffee beans (Coffea sp,) in Indonesia produced mostly by small-scale

plantation by farmers. This study was aimed to investigate fungal infection and toxigenicity of Aspergillus

flavus strains on dried-stored cacao and coffee beans at collector distribution chain. As much as five

kilogram dried-stored of the beans were collected from collector distribution chain at Karo Regency, North

Sumatra.. The moisture content were determined by oven drying metthod. The percentage of beans infected

by each fungal species was observed by direct plating on dichloran 18% glycerol agar (DG18) medium..

Fungal population was enumerated by a dilution followed by a pour plate in DG18 medium. Cultural

method in agar medium containing 10% coconut milk was used to determine toxigenicity of A. flavus.

Results showed moisture content cacao and coffee beans at collecto distribution chain was above National

Indonesia Standard. Eighty eight percent of cacao beans were infected by A. niger, whereas, coffee beans

were the most infected by A. flavus. (78.60%). A total of 14 strains of A. flavus were isolated, 4 strains

found at cacao and 10 strains at coffee beans. Among of the total A. flavus, 3 strains are aflatoxin producers

at cacao and 4 strains at coffee beans.

1 INTRODUCTION

Cacao (Theobroma cacao) and robusta coffee

(Coffea canephora L.) are important commodities

in North Sumatera. Most of cacao and coffee beans

are produced by farmers as small-scale plantation

(Direktorat Jenderal Perkebunan 2018). Preharvest

and postharvest handling of the commodities such as

harvesting, drying, and storing were conducted

traditionally. Therefore, quality of the commodities

under National Standard (Amaria et al. 2014).

Physical damage of the beans caused by insect or

inappropriate postsharvest handling accelerate

fungal infection and mycotoxin contamination (SNI,

2017; Nurhadi et al. 2019).

Among storage fungi that commonly

contaminate cacao beans are Aspergillus,

Botryodiplodia, Mucor, Fusarium, Neurospora,

Penicillium and Phytophthora (Fagbohun et al.

2011). Whereas, coffee beans were infected by

Aspergillus niger, Aspergillus flavus, and

Aspergillus ochraceus that produce ochratoxin A

(Dharmaputra et al. 1999; Klich 2007; Djossuo et al.

2015).

The purpose of the study was to enumerate

fungal infection and toxigenicity of A. flavus strains

on cacao and coffe beans at collector distribution

chain in North Sumatera.

2 MATERIALS AND METHOD

2.1 Sampling of Cacao and Coffee

As much as four kilogram each of intact, dried-

stored cacao and coffee beans as samples were

obtained at collector distribution chain at Karo

Regency, North Sumatera. Sample then was packed

in a sterile polyethylene bag and keep in cold at

±12°C for further use.

2.2 Determination of Fungal

Contamination

The percentage of beans infected by fungal species

was conducted by direct plating on dichloran 18%

glycerol agar medium. (DG18). Each sample was

surface disinfected using 1% sodium hypochlorite

solution for 1 minute, they were then dried using

sterilized filter paper and placed in petri dish

558

Nurtjahja, K., Hastuti, L., Nurfalah, A. and Ramayani, .

Fungal Infection and Toxigenicity Aspergillus ﬂavus Isolated from Cacao and Coffee Beans in North Sumatera.

DOI: 10.5220/0010613300002775

In Proceedings of the 1st International MIPAnet Conference on Science and Mathematics (IMC-SciMath 2019), pages 558-560

ISBN: 978-989-758-556-2

(diameter. 9 cm) containing DG18. The number of

cacao and coffee beans in petri dish was 5 and 10

respectively. Five replication were made for each

sample. All plates were incubated at 29°C for 5

days.

2.3 Enumeration of Fungal

Population

Fungal population on each sample was enumerated

by a dilution and followed by pour plate in dichloran

18% glycerol agar (DG18) medium. Each sample

bean was powdered and 25 g of which was placed in

to a 500 ml flask and homogenate with 250 ml of

sterile distilled water to obtain a 10

-1

suspension.

The dilution was carried out on 10

-2

, 10

-3

and 10

-4

One ml of the suspension was placed on DG18

medium in petri dish (diameter 9 cm).. Each dilution

was triplicates. All plates were incubated at 29

C for

5 days.

2.4 Moisture Content Determination

Bean moisture content was determined by oven

drying method according to Standard Nasional

Indonesia (SNI, 2017).

2.5 Identification of A. flavus

Each of A. flavus was isolated on potato dextrose

agar (PDA) medium then identified according to Pitt

and Hocking (2009).

2.6 Toxigenicity of A. flavus

The toxigenicity of each A. flavus was determined

by culturing in 10% coconut agar medium (CAM) in

petri dish (Lin and Dianese 1978). The presence of

yellow pigment at the reverse side of the medium

indicate as aflatoxin producer.

3 RESULTS AND DISCUSSION

3.1

Moisture Content and Percentage

of Fungal Contamination

Cacao and coffee beans at collectors distribution

chains stored at room temperature (23 to 25°C) and

packed in a 50 kilogram polyethylene and gunny

bags. The moisture content of cacao and coffee

beans was 8.2% and 12.5% respectively. The

moisture content was higher than that maximum

stndard moisture content for cacao (7.5%) (BSN

2017) and coffee beans (12 %) (SNI 2017). High

relative humidity during storage might the dried

stored cacao and coffee beans absorb water favor,

and might promote fungal growth (Godet and

Munaut 2010).

The percentage of the beans infected by fungal

species (Table 1) showed that three fungal species

were isolated. It was found that 88% of cacao beans

was infected by Aspergillus niger followed by A.

flavus (33.33%) and A. rubrum (28.88%. The results

was similar to the study by Wangge et al. (2012),

they found that cacao beans were common infected

by A. flavus and A, niger. In similar, coffee bean

was dominated by A. flavus (78.60%) followed by A.

niger (6%).

Table 1: The percentage of cacao and coffee beans

infected by fungi

Fungal species

% Beans infected by fungal

species

Cacao

ean Coffee

ean

illus

lavus 33.33 78.60

nige

88.88 6.00

rubrum. 28.88 0

Most storage fungi that contaminate agricultural

products was soil fungi, they contaminate during

harvesting Agricultural products that fallen on the

ground or contaminate to the soil during harvesting

were susceptible infected by fungi (Dharmaputra et

al. (2018). We assumed the infection of the

Aspergillus on cacao and coffee beans at collector

distribution chain occured during postharvest

handling.

3.2 Fungal Population

A total of six fungal species were isolated (Table 2).

Cacao beans more infected than that of coffee beans.

Aspergillus flavus and and A. niger were the most

found.

Table 2: Fungal population (cfu/g) isolated from dried-

stored cacao and coffee beans collected from collectors

distribution chain at Karo Regency, North Sumatera

Fungal species

Fungal population (cfu/g)

Cacao bean Coffee bean

illus

lavus 1×10

13×10

fumigatus 0 1×10

nidulan 0 0.3×10

nige

1×10

rubrum. 0.3×10

Penicillium sp.. 0 0.3×10

Yeast 0.3×10

Fungal Infection and Toxigenicity Aspergillus ﬂavus Isolated from Cacao and Coffee Beans in North Sumatera

559

High fungal population at moisture content 8.2%

in cacao and 12% in coffee beans indicate that most

storage fungi were able to grow at low moisture

content. The presence of yeast in cacao beans might

the single cellular yeast still viable after

fermentation stage before drying process. In

addition, a total of 14 A. flavus strains were isolated

from cacao and coffee beans. Higher moisture

content in coffee beans might more A. flavus was

found than that of cacao beans. The cacao bean was

colonized by 3 strains of aflatoxigenic A. flavus

while 4 strains on coffee beans.

4 CONCLUSION

The presence of fungal infection at cacao and coffee

bean at collector distribution chain was potentially

reduced quality and mycotoxin contamination.

Appropriate postharvest handling of cacao and

coffee beans was required to prevent fungal growth

during storage.

ACKNOWLEDGEMENT

The research was funded by Universitas Sumatera

Utara, contract DRPM Reseach grant no.

152/UN5.2.3.1/PPM/KP-DRPM/2021.

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