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 *Corresponding author.

Email: tasnia2009@yahoo.com

eISSN: 2550-2166 / © 2020 The Authors. Published by Rynnye Lyan Resources

  Food Research 4 (4) : 1297 - 1302 (August 2020)
  Journal homepage: http://www.myfoodresearch.com

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Microbiological quality analysis of different types of popular dried food items

*Ahmed, T., Sharmin, A.,  Paul, A., Dipu, M.R. and Islam, T.

Department of Microbiology, Stamford University Bangladesh, 51. Siddeswari Road, Dhaka 1217,

Bangladesh

Article history:

Received: 26 February 2020

Received in revised form: 7

March 2020

Accepted: 9 March 2020

Available Online: 3 April

2020

Keywords:

Contamination,

Pathogenic bacteria,

Production,

Quality

DOI:
https://doi.org/10.26656/fr.2017.4(4).080

Abstract

The study was carried out to investigate the microbiological quality of dried foods which

are very popular among kids. Moreover, people from all age groups like it, although adults

do not take it on a regular basis, the total consumed amount among the adults are not

negligible. Chips, biscuits, muesli, salted peanuts all are dried foods, and all of these can

undergo microbial contamination due to the remaining water activity, environmental

condition, production processing faults, humidity, temperature etc. In the current study,

twenty-four samples were analyzed for microbial quality analysis. Six samples from each

category of dried food were subjected to study for the presence of mesophilic organisms,

coliforms, molds and other specific food pathogens. Of the samples studied, almost all

were found to be contaminated with the mesophilic bacteria (104-107CFU/g) and fungus

(105-107CFU/g). Survival of Vibrio spp. was absent and Salmonella spp. was found in

only one sample. Escherichia coli, Pseudomonas spp., Staphylococcus spp. and Shigella

spp. were found in many of the samples indicating the poor quality of the dried food items.

Overall, the present study revealed that potato chips were highly contaminated by bacteria

and fungi. Consuming such contaminated chips may cause foodborne illness that is a great

threat to our health.

1. Introduction

Dried foods like chips, biscuits, muesli or roasted

nuts are very popular snack items all over the world

which are available in every grocery shop, super shops as

well as in the remote areas. These are enjoyed most

during vacation, journey, picnic and even as school

tiffin. The principal of production of potato chips are

cooked and salted potatoes pieces mixed with different

kinds of flavorings and ingredients including herbs,

spices, cheeses, natural or artificial flavors and additives.

A survey results published (Berry and Norman, 2014)

that the world potato chip market collected total revenues

of US$16.49 billion in 2005 that was 35.5% of the total

market of snacks in that year ($46.1 billion) (Savory

Snacks: Global Industry Guide, 2016). Nuts are a source

of protein, fat and minerals. People who are more

considerate about their health prefer nuts that junk

snacks (Bhat and Vasanthi, 2003). Dried cereals are best

suited for a modern busy life as they can be eaten

directly with milk without further processing. Cereals are

produced by mixing different cereal grains and

processing them together (like roasting, grinding,

swelling, shredding, flaking and so on). They are a good

source of vitamins, minerals, zinc, phosphorus and

calcium (Williams, 2014; Mbaeyi-Nwaoha et al., 2016).

Another popular dry food is biscuit which mostly

contains carbohydrate, and some protein, gluten and fat

content (Shewry et al., 2002; Adobowale et al., 2012).

Potato Chips are not only tasty and easily available

snack, but also inexpensive. The major fact is the impact

of chips on our body is not sound. Due to high oil

contents, it is harmful to the peoples suffering from

chronic heart diseases and obesity (Consensus Action on

Salt and Health, 2004; Prajapati et al., 2003).

There are international standards for the

microbiological limit of foods and beverages. These

standards can be modified slightly by locally. Almost

every country has its own regulations and monitoring

body to check the quality of the food, exclusively the

ready to eat foods due to its high alarm for human health

hazard. As a ready to eat foods, chips, biscuits, salted

nuts and muesli have a risk for microbial contamination

on its production, packaging, transportation or storage

(Fraizer and Westhoff, 1995; Eze et al., 2011; Oladipo et

al., 2019). Escherichia coli O157: H7, Salmonella spp.,

 Ahmed et al. / Food Research 4 (4) (2020) 1297 - 1302

eISSN: 2550-2166 © 2020 The Authors. Published by Rynnye Lyan Resources

Shigella spp., Bacillus spp., Mycobacterium spp.,

Brucella spp., Listeria monocytogenes, Yersinia

enterocolitis, Pseudomonas spp.; Clostridium

perfringens, Klebsiella spp., Vibrio spp., Campylobacter

jejuni and Staphylococcus aureus have been reported to

be the common food spoilage bacteria (Fraizer and

Westhoff, 1995; Beuchat et al., 1996; Torquato et al.,

2004; Jay et al., 2005; Nordmann et al., 2009; Rahman

and Noor, 2012; Acharjee et al., 2013; Hassan et al.,

2013; Noor et al., 2014; Oladipo et al., 2019).

Furthermore, it contains toxic and carcinogenic

byproducts which are not found in the uncooked foods

(Exon, 2006).

Potato Chips contaminated by microorganisms

(bacteria, yeasts, viruses, and protozoa) can cause health-

related issues (Jaykus, 2000; Drury, 2012).

Contaminated nuts with fungus and associated toxin can

cause liver damage, cancer, abortion etc. (Abbas et al.,

2005; Drury, 2012).

The objective of the current study was to identify the

existence and amount of bacteria (Escherichia coli,

Klebsiella spp., Pseudomonas spp., Staphylococcus spp.,

Shigella spp., Salmonella spp., Aeromonas spp., Vibrio

spp.) and fungi in different types of dried foods (potato

chips, muesli, biscuits, salted peanuts) to determine their

overall quality for assessing the public health risks.

2. Materials and methods

2.1 Study area, sampling

A total of twenty-four samples of chips, biscuits,

muesli and salted peanut (six sample per category of

food) with valid manufacturing and expiry dates were

collected from April 2017 to May 2017. These samples

were collected from different retailer store in Dhaka city,

Bangladesh and then transported to the laboratory to

determine the microbiological quality of the respective

chips.

2.2 Sample processing

For each dried food samples, 10 g were weighed and

homogenized with 90 mL normal saline and serial

dilutions were prepared up to 10-4 and the dilution was

used for plating purpose according to the standard

protocols (Cappuccino and Natalie, 1983; Cappuccino

and Sherman, 1996).

2.2.1 Enumeration of total viable count (TVC) and

total fungal count (TFC)

For the quantification of total viable count (TVC)

and total fungal count (TFC), 0.1 mL of the 10-3 and 10-4

dilutions were spread onto the Nutrient agar (NA) and

Sabouraud’s dextrose agar (SDA) (Oxoid Ltd.,

Basingstoke, Hampshire, England) plates, respectively,

by means of spread plate technique. Plates were

incubated at 37°C for 24 hrs and 25°C for 48 hrs for total

viable bacteria and fungi, respectively (Atlas et al., 1995;

Cappuccino and Sherman, 1996; Downes and Ito, 2001;

Deak, 2003).

2.2.2 Enrichment of samples

An aliquot (1 mL) of the homogenized sample was

transferred into 9mL of selenite cysteine broth (SCB)

and alkaline peptone water (APW) (Oxoid Ltd.,

Basingstoke, Hampshire, England) for the enrichment of

Salmonella, Shigella, and Vibrio spp., Aeromonas spp.

respectively and incubated at 37°C for 4-6 hours .

Samples were then diluted up to 10-3 and 0.1mL of

samples from each of the 10-2  and 10-3 dilutions were

spread onto Salmonella-Shigella (SS) agar and

thiosulfate citrate bile salt sucrose (TCBS) agar (Oxoid

Ltd., Basingstoke, Hampshire, England) for the isolation

of Salmonella spp., Shigella spp., and Vibrio spp.,

Aeromonas spp. respectively. Plates were incubated at

37°C and the appearance of typical colonies (if any) was

noticed within for 24-48 hrs (Samia et al., 2014).

2.2.3 Isolation and enumeration of Staphylococcus

spp. and Pseudomonas spp.

   From the 10-3 and 10-4 dilution of each suspension,

0.1 mL of sample was spread onto Mannitol salt agar

(MSA) and Pseudomonas agar (PA) media for the

enumeration of Staphylococcus spp. and Pseudomonas

spp. consecutively. All the plates were incubated at 37°C

for 24 hrs (Samia et al., 2014).

2.2.4 Isolation and enumeration of Escherichia coli,

Klebsiella spp.

From the 10-3 and 10-4 dilutions of each suspension,

0.1 mL of sample was spread onto MacConkey agar

media for the enumeration of E. coli and Klebsiella spp.

All the plates were incubated at 37°C for 24 hrs (Samia

et al., 2014).

3. Results

3.1 Microbiological analysis of chips

From Table 1, we can see that Total viable count

(TVC) higher than Total fungal count (TFC) for sample

C1,C2,C5,C6 and in the case of sample C3, C4 TFC are

higher than TVC. The highest count of TVC (2.8×107

CFU/g) and TFC (1.1×106 CFU/g) was found in sample

C2 and the lowest count of TVC (3.0×105 CFU/g) and

TFC (6.0×104 CFU/g) was found in sample C1. In our

study, we also tried to detect the existence of some

specific bacteria in potato chips. We found Salmonella

spp. (7×104 CFU/g) only in sample C3. Pseudomonas

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spp. (ranging from 2.5×104 CFU/g to 2.8×105CFU/g),

Staphylococcus spp. (ranging from 4×104 to

5.2×105CFU/g), Shigella spp. (ranging from 1.0×104

CFU/g to 7×105 CFU/g) was found in all the samples

which means that all the samples were produced in such

a condition which made the quality unsatisfactory for

consumption. E. coli was found only in 3 samples

(sample C1, C3, C4).

3.2 Microbiological analysis of biscuits

Table 2 shows the overall microbiological quality of

biscuits. The highest total bacterial count and total fungal

count was found in sample B5. Salmonella spp. and

Vibrio spp. were absent. Aeromonas spp. (1.0×103 CFU/

g) was found only in sample B5. E. coli, Klebsiella spp.

and Shigella spp. was found in 2 samples each.

Staphylococcus spp. (ranging from 4.0×103 CFU/g to

2.6×104 CFU/g) and Pseudomonas spp. (ranging from

2.5×104 CFU/g to 1.4×105 CFU/g) were found in all

samples.

3.3 Microbiological analysis of muesli

From Table 3 (muesli) we can observe that TVC was

higher than TFC for all samples. The highest count of

TVC (2.7 × 106 CFU/g) and TFC (1.1×106 CFU/g) was

found in sample M2 and the lowest count of TVC

(3.0×105 CFU/g) and TFC (1.9×105 CFU/g) was found in

sample M6. Salmonella spp. and Vibrio spp. were totally

absent. Pseudomonas spp. (ranging from 1.7×103 CFU/g

to 2.5×105 CFU/g), Staphylococcus spp. (ranging from

2.0×104 to 2.9×105 CFU/g), Shigella spp. (ranging from

1.0×103 CFU/g to 2.4×104 CFU/g) were also was found

in all the samples. Klebsiella spp. was present only in

sample M4 whereas E. coli was found in sample M3 and

sample M6.

3.4 Microbiological analysis of salted peanut

Table 4 (salted peanut) depicts the highest count of

TVC (2.2×106 CFU/g) in sample P3 and TFC (1.1×106

CFU/g) in sample P2. The lowest count of TVC (2.0×105

CFU/g) was found in sample P2 and TFC (6.0×105 CFU/

g) was found in sample P1. Salmonella spp. and Vibrio

spp. was absent like all other dry foods under this study.

Aeromonas spp. was found only in sample P2 and P6. E.

coli, Klebsiella spp. and Shigella spp. was found to be

present in 50% samples (3 out of 6). The highest number

of Staphylococcus spp. and Pseudomonas spp. was found

in sample P1.

4. Discussion

All the samples have a noticeable amount of TFC

and TVC that lies on the unsatisfactory levels. According

to East African Standard 747, 2010, if the count for chips

(per gram) for TVC is >104 and TFC is >103 then it is

unacceptable. The presence of Staphylococcus spp.,

Shigella spp., and Vibrio spp. is not satisfactory to be

present as they are potent food spoilers and can cause

disease in human upon consumption. Their presence

must be controlled to keep consumers safe. Salmonella

spp. and E. coli must also be absent in chips (Harris et

al., 2002; East African Standard 747, 2010).

If any bacteria from the fecal group (in our study E.

coli, Klebsiella spp.) is present it means that the quality

of the food is not safe to eat. The presence of any amount

of fecal bacterium is not acceptable according to the

safety guideline of ready dried foods.

In this study, most of the samples showed the

presence of E. coli and Klebsiella spp. Other pathogenic

bacteria (Pseudomonas spp. and Salmonella spp.) were

present in a lower amount (Guan and Holley, 2003).

The presence of such bacteria in dried food items can

come during the production process and also after

storage if the packaging material is not intact or the

storage condition is not good for storing food items.

During the production process, many steps are carried

out and in many of these steps, there are possible

chances of contamination to occur (Figure 1).

Mechanical areas in processing line like hopper with

feeder, grader, peeler, feed conveyor, slicer, flavor

applicator etc. are the areas where attention should be

maximized to prevent such unwanted contamination.

   Biscuits can be spoiled by different ways like

physical, chemical and microbial spoilage. Microbial

spoilage often depends on some factors like storage

temperature, humidity, storage hygiene, packaging

material, the moisture content in the storage area etc.

(Ooaraikul, 1991). Peanuts often get contaminated with

aflatoxin while storing in conditions with high

atmospheric temperature, high humidity, low light and

long-term storage (Ostadrahimi et al., 2014).

   Dried foods are quite popular fast food item around

the world and often we ignore the quality as it is a dry

food item. But there are possibilities to become

contaminated during production and processing of these

foods. Several food poisoning bacteria and fungi can be

present if proper good manufacturing practice is not

maintained and the people (especially children and other

young adults among who such food items are very much

popular) consuming such contaminated chips can face

serious health issues. Attention should be kept on dry

food items like chips to process in such a way to prevent

any contamination.

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C1 3.0 ×105 6.0 ×104 4 × 104 7.0 ×104 1.2 × 105 1.4 ×105 2.5 × 105 0 8.0 ×104

C2 2.8× 107 1.1 × 106 0 0 2.8 ×105 4.5× 105 1.9 × 105 0 4.7 × 104

C3 1.3× 105 2.6× 105 2 ×104 1.0 × 104 8.8 ×104 4 × 104 1.1 × 105 7 ×104 0

C4 2.1  ×106 1.4 × 105 1.5×105 4 ×104 7.5× 104 1.7 × 105 1.4 ×105 0 1.8 ×105

C5 2.8 × 106 7.5×104 0 4.6× 105 2.5 ×104 4.8 ×105 7.0 × 105 0 0

C6 2.2 ×106 1.7 ×105 0 1.3 × 105 1.4 × 105 5.2 × 105 1.0 × 104 0 1.0 × 104

Table 1. Microbiological analysis of chips (CFU/g)

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B1 2.2 ×105 2.0 ×104 4 × 104 0 2.8 ×104 2.0 ×104 0 0 0
B2 2.0× 104 1.6 × 105 0 0 1.2 × 105 1.8× 104 0 0 0
B3 1.0× 105 1.4× 104 0 1 × 104 1.4 × 105 4.0 × 103 1.0 × 103 0 0
B4 2.6  ×104 2.4 × 105 1.5 ×105 0 8.8 ×104 1.7 × 104 0 0 0
B5 2.1 × 106 2.7×105 0 0 2.5 ×104 2.6 ×104 0 0 1.0 × 103
B6 2.1 ×105 1.0 ×102 0 1.3 × 103 7.5× 104 2.2 × 104 1.1× 103 0 0

Table 2. Microbiological analysis of biscuits (CFU/g)

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M1 1.9×105 2.9 ×104 0 0 1.0 × 104 2.4 ×105 2.0 × 103 0 0
M2 1.6× 106 1.1 × 104 0 0 1.8 ×103 2.8× 104 1.3 × 104 0 0
M3 2.2× 105 1.6× 105 1.0 ×103 0 1.0 ×104 2.0×104 2.1 × 103 0 2.7 ×103
M4 2.8×105 2.1 × 104 0 4 ×104 2.5× 105 2.4 × 105 2.4 ×104 0 0
M5 2.8×105 2.0×105 0 0 2.1×104 2.9×105 1.0× 103 0 1.5 ×104
M6 2.7×106 1.9×105 1.5 ×105 0 1.7×103 2.2 × 104 1.6×104 0 1.2 ×103

Table 3. Microbiological analysis of muesli (CFU/g)

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P1 1.6× 106 6.0×105 0 5.2 ×103 1.0 × 105 2.4 ×105 1.5 × 104 0 0

P2 2.0 × 105 1.1×107 4.4 ×103 1.0 × 104 0 1.1× 105 0 0 1.1× 103

P3 2.1 × 106 2.6× 105 1.2 ×103 0 8.8 ×103 1.5 × 104 1.1 × 104 0 0

P4 2.2 ×105 1.4 ×106 2.5 ×104 2.8 ×104 7.5× 103 1.0 × 105 0 0 0

P5 2.1 × 105 7.5×105 0 0 2.5 ×104 4.8 ×103 1.2 × 103 0 0

P6 2.2 ×106 1.7×106 0 0 1.4 × 104 5.2 × 103 0 0 1.4× 103

Table 4. Microbiological analysis of salted peanut (CFU/g)

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4. Conclusion

Foodborne illness can result in death of people from

all age range with a higher ratio for children. Our result

indicated that dried foods are contaminated by bacteria

and fungi. If people consume such contaminated these

contaminated foods, they will suffer from various

foodborne diseases. Therefore, routine microbiological

analysis of different dried foods is necessary to protect

public health. The Government should also take

necessary steps to monitor the food quality on a regular

basis and enforce the law against those who will fail to

produce safety foods.

Conflict of Interest

The authors have no potential conflict of interest.

Acknowledgement

Authors would like to thank Stamford University

Bangladesh for the financial and technical supports.

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Figure 1. Chips production line. (Green parts are safe and red parts are the areas where contamination can occur)

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 *Corresponding author.

Email: rosnahs@upm.edu.my

eISSN: 2550-2166 / © 2020 The Authors. Published by Rynnye Lyan Resources

  Food Research 4 (4) : 1172 - 1180 (August 2020)
  Journal homepage: http://www.myfoodresearch.com

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Effects of various grated sago sizes, steeping periods and trunk sections on sago

starch recovery (Metroxylon spp.)

1,2Wan Mohd Fariz, W.A., 1*Rosnah, S., 1Mohd Zuhir, M.N., 2Azman, S. and 3Noramina, H.

1Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
2Engineering Research Center, MARDI Headquarters, 43400 Persiaran MARDI-UPM, Selangor, Malaysia

3CRAUN Research Sdn Bhd, 93050 Kuching, Sarawak, Malaysia

Article history:

Received: 4 February 2020

Received in revised form: 6

March 2020

Accepted: 8 March 2020

Available Online: 30 March

2020

Keywords:

Sago palm,

Starch,

Grated sago size,

Steeping,

Extraction

DOI:
https://doi.org/10.26656/fr.2017.4(4).053

Abstract

The sago palm stored a native starch between the trunk fiber gap. The trunk needed to be

crushed into a fine size using a mechanical system. In general, the grated sago size affects

the extraction efficiency, which depends on sago starch that dissolved in water during an

extraction process. Therefore, the aim of this study was to determine the effect of grated

sago sizes on starch recovery at different steeping periods and trunk sections. The sago

trunks used were selected at three palm section (Top, Middle and Bottom). After the

grating process using Sago Grater, the grated sago was dried and sieved at different sizes

(2.80 mm, 2.00 mm, 1.00 mm, 0.85 mm, 0.45 mm and 0.30 mm). Furthermore, the grated

sago with different sizes was steeped in sodium metabisulphite (Na2S2O5) at different

periods (5 mins, 24 hrs, 48 hrs and 72 hrs) for starch extraction. The results showed that

the independent variables of grated size most significantly affected starch recovery

(P<0.05). A substantial amount of starch could be recovered from grated sago by reducing

the grated size at X<0.30 mm which was up to 58% of the extraction efficiency. The

increment of the steeping period from 5 mins up to 24 hrs increased the starch recovery;

however, a longer steeping period showed an insignificant difference (P>0.05).

Additionally, the trunk selection also affects the starch recovery, however, it does not

influence the extraction efficiency.

1. Introduction

In Malaysia, more than 90.0% of sago planting areas

are in Sarawak state since most of the state areas were

covered by wetland that is very suitable for sago

cultivation and it has become one of the important

industries. Nowadays, Malaysia has become the third

main sago producer in the world (Naim et al., 2016).

Previously, the Malaysia Department of Statistics (2005)

reported that Malaysia exported 45,300 metric tons

weight of sago starch, approximately RM 40.40 million.

In 2017, there was an increment in the annual sago

production to 212,447 metric tons of sago starch (DOA,

2017), estimated to be equivalent to RM 189.47 million.

This indicates that the increase of production was due to

the increase of current demand which is in line with the

growth of starch utilization in manufacturing industry

applications. Furthermore, even though the source of

starch from sago was optional, sago starch is

advantageous because it contains four times greater

starch content than rice (Yamamoto, 2014). Starch is an

important raw material for the processing operations in

the manufacturing industries such as agro industries,

biopesticides, bio-ethanols, cosmetics, and

pharmaceutical industry (Bintoro, 2011). In addition, its

microbial resistant ability is advantageous as additional

material in the production of biodegradable material in

packaging technology. However, it has low durability in

a single form. Therefore, it is essential to blend it with

additional material to produce long-lasting and durable

composite material (Yajie et al., 2020).

Nowadays, in the sago palm industry processing

method, both in traditional or modern handling, the sago

processing procedures remain the same. Briefly, it

involves peeling, size reduction, grating, extraction and

sedimentation. Before the processing begins, usually the

trunk barks need to be removed or peeled manually using

axes and then grated using sharp nails. During the

grating process, water is added continuously to the

grated trunks in order to transfer them to a rotating mesh

screener that functions as an extractor. The extracted

water solution from the grated trunk contains starch that

is channeled to the sedimentation tank. After two hours,

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the starch will settle down at the bottom of the tank and

the excess water on the top layer inside the tank is

removed (Yamamoto, 2014; Darma et al., 2017).

According to Abd Aziz (2002), 65.7% of the grated

residue after the extraction process contained starch.

Linggang et al. (2012) also stated that about 58% of the

residue was recorded still contained starch. Since the

residue is mostly dumped into the river, using the total

loss rate (assuming about 65.7%), it was estimated about

406,932 metric tons of sago starch is wasted based on the

total sago production reported by DOA (2017). The

losses occur due to the inefficiency of the extraction

process. One of the factors that influence the extraction

efficiency is the proportion of the sago trunk structure

that ruptured which is producing various of grated sago

size (Tay et al., 2013). The native sago starch extraction

is different from roots and cereals as it is more

complicated. The mean diameter of native sago starch

granule was 29.4 µm (Kaur et al., 2011) and stored in the

parenchyma cells of the coarse vascular bundles that

contain a high amount of lignin. The lignins had

important roles in the lodging resistance (Hu et al.,

2017). Furthermore, the native starch granules also fill

up the empty spaces between the lignins and bond the

lignins together. As a result, the separation of sago native

starch from the trunk is a challenge. Therefore, the size

of the grated sago trunk plays an important factor to

increase extraction efficiency and high recovery.

The purpose of this study was to determine the effect

of various grated sago sizes on the starch recovery

during the extraction from sago palm at different

steeping periods. Furthermore, this study also evaluated

the effect of sago trunk at different sections (Top, Middle

and Bottom) to the grated size and starch yield.

2. Materials and methods

2.1 Raw material selection

The selection of sago palm for the assessment is

based on the tree’s maturity stage, which contains the

maximum starch content. As reported by Jong (1995a),

the stage was between growing and flowering. The sago

palms were harvested at Labu in the State of Negeri

Sembilan. After harvesting, the sago palm trunks were

categorized into three sections: Top (T: 1 m from frond

base), Middle (M: between 5 m to 6 m from the ground

surface) and Bottom (B: up to 1 meter from the ground

surface) as shown in Figure 1. Each identified section of

sago trunk was cut into 50 cm length. The trunk barks

were peeled off using handheld chainsaws (OG6816,

Ogawa, Japan) and cut into square blocks of 10 cm × 10

cm × 10 cm. The lignin orientation direction (the sago

palm lignin orientation was parallel to the trunk’s

vertical axis) was marked as an arrow.

2.2 Raw material grating process

The purpose of the grating process was to break the

trunk structures into a finer size in order to remove or

loosen the native starch from the trunk structures. The

grating process of sago trunk block was conducted using

a Sago Grater with the grating direction being parallel to

the vertical axis of the sago trunk lignin orientation.

According to the report by Wan Mohd Fariz et al.

(2018), grating at the parallel direction to the vertical

axis of sago trunk lignin orientation produced finer

grated trunk and higher starch yield recovery compared

to the perpendicular direction. Therefore, the sago blocks

were placed on the feeding platform in a position where

the sago trunk lignin orientation (arrow mark) pointed to

the grater blade direction as previously done by Wan

Mohd Fariz et al. (2018). The grating process was

carried out and the repeated six times for each sago block

section. The grated sago trunk blocks from each section

(T, M and B) were collected separately.

2.3 Assessment of grated sago size distribution

The sieving process was conducted to separate the

grated sago particles according to size. First, the grated

sago was dried at 68°C (Jong,1995a) using an air-drying

oven (FAC-100, Protech, Malaysia). The drying process

was stopped when the moisture content (MC) value

showed a constant value for three consecutive readings

taken at every half an hour. After drying, 100 g of dried

grated sago was sieved using a sieve shaker (Endecott,

United Kingdom). At every 10 mins interval of the

sieving process, the total weight of the sieve and content

were measured. The sieving process was stopped when

three consecutive readings of the total weight showed a

constant value (ASTM, 2001). Referring to the grated

sago distribution assessment by Wan Mohd Fariz et al.

(2018), the selected grade of sieved sizes used were 2.80

mm, 2.00 mm, 1.00 mm, 0.85 mm, 0.45 mm and 0.30

mm. The sieving process was repeated six times to get an

average (µ) and standard deviation (SD: ±). The weight

for each sieve product according to the grade of sieved

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Figure 1. Sago palm trees section (Wan Mohd Fariz et al.,

2018)

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sizes was recorded. Finally, the Weight Percentage

Ratios (WPR) for each sieve product were calculated

(equation 1). Additionally, the MC of the grated sago

before and after drying were measured using digital

measuring devices (HE53 230V, Mettler Toledo, USA).

2.4 Starch extraction using steeping method

The steeping method used water as solvent in order

to extract the native starch. Dried grated material (sago

trunk) of 2 g according to the grade sizes (2.80 mm, 2.00

mm, 1.00 mm, 0.85 mm, 0.45 mm, 0.30 mm and <0.30

mm) were steeped in 0.2% sodium metabisulphite

(Na2S2O5) (Tay et al., 2013) which was dissolved in

water (H2O) at room temperature as shown in Figure 2.

The steeping period was set at 5 mins, 24 hrs, 48 hrs and

72 hrs. The ratio of dried grated material to the steeping

solution was 1:6 (w/w). The extracted liquids were

centrifuged at 2000 rpm for 10 mins and analyzed to

determine the value of starch content using VIS

spectrophotometer (Lambda 35, Perkin Elmer, USA) at

650 nm wavelength. An iodine solution was added into

the solution as a starch indicator (Tay et al., 2013). The

experiments were repeated six times. The starch recovery

percentage at different grated sizes was calculated

(equation 2).

2.5 Chemical composition and extraction efficiency

A dry grated sago trunk (sample: T, M and B) was

subjected to chemical determination for total starch

according to AACC 76-13.01 (2000) method by using a

kit by Megazyme International Ireland Ltd (AACC,

2000). The experiments were repeated six times. In

addition, the extraction steeping method efficiency was

calculated using equation 3.

2.6 Data analysis

The statistical data and variance analysis (ANOVA)

were analyzed using IBM SPSS Statistics 25.0 software

to test the main effects of independent and interaction

parameters. The significant difference was measured at a

confidence level of 95% (P<0.05).

3. Results and discussion

3.1 Grated sago size distribution assessment produced

by grating machine

The determination of moisture content (MC) on the

material to be grated was important because it affects the

trunk toughness which in turn influenced the grating

capability. As the MC of wood increased, the ductility

eventually increased. Furthermore, higher MC increased

the specific toughness (Oyedeji et al., 2017). Figure 3

shows the MC of sago trunk according to sections (T, M

and B). The average MC between the sago trunks

sections (T, M, B) showed an insignificant difference in

values (p>0.05), ranging between 51.23 to 62.34%

(µ=59.00±4.21). Therefore, the MC factor may not affect

the trunk toughness at the different palm trunk sections

(T, M, B) for this study. In addition, according to the

report by Yamada et al. (2010), the MC of sago trunk

was lower than that oil palm trunk which was 78%, 75%

and 67% (µ=74.00±4.58%) with a percentage difference

of 20.27% (P<0.05). Furthermore, the sago trunk (palm

type) MC is extremely high compared to ordinary wood

timber which normally ranges between 40% to 50% as

stated by Yamada et al. (2010).

Determination of grated sago distribution was

conducted according to sizes: X<0.30 mm, 0.30≤X<0.45

mm, 0.45≤X<0.85 mm, 0.85≤ X<1.00 mm, 1.00≤X<2.00

mm, 2.00≤X<2.80 mm and X≥2.80 mm, where X refers

to the grated sago size range. In order to perform the

sieving process, the grated sago needed to be dried as

high MC affected the efficiency of the sieving process,

causing the material to clump together during the sieving

process. The results showed that the average MC of dried

grated sago for each trunk section (T, M, B) ranged

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(2)

(3)

(1)

Figure 2. Grated sago (2.80 mm, 2.00 mm, 1.00 mm, 0.85

mm, 0.45 mm 0.30 mm and <0.30 mm) was soaking in

0.2% of Na2S2O5 and dissolved in H2O.

Figure 3. The moisture content (MC%) of sago trunk at Top

(T), Middle (M) and Bottom (B) sections. Error bars were

expressed as mean ± SD; n = 12

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between 5.18% to 6.11% with an average of

5.53±0.44%, which is close to the value reported by Wan

Mohd Fariz et al. (2018) (5.15±0.37%; p>0.05). Figure 4

shows the WPR of grated sago at different sizes (mm).

The error bars referred to the standard deviation (±) for

each average data of WPR. The mesh sizes of X<0.30

mm, 0.30≤X<0.45 mm, 0.85≤X<1.00 mm, 2.00≤X<2.80

mm and X≥2.80 mm showed that the WPR was less than

12%, while the mesh size of 0.45≤X<0.85 mm showed

that the WPR value ranged between 28 to 32%. The

highest WPR was recorded at mesh size of 1.00≤X<2.00

mm, which ranged between 25 to 35%. Cumulatively,

the X<1.00 mm (initial assumption as finer grated sago)

showed that the highest total WPR was produced by the

top section of the trunk (61.36%), followed by the

middle and bottom sections at 52.06% and 51.76%

respectively and a significant difference (P<0.05)

between the trunk sections. This might be due to the

different hardness of each trunk sections. Naturally, the

upper section of the tree trunk is softer than the bottom.

Based on a study, the tree trunk hardness was inversely

proportional to the tree height (Matsuoka, 2008.).

Furthermore, the grated sago size barplot (Figure 4)

showed the similar size distribution when the sago block

fiber was grated parallel to the direction of the roller

grater teeth during the grating process as reported by

Wan Mohd Fariz et al. (2018).

3.2 Native starch extraction using steeping method

according to grated sago size

Producing finer grated sago is important to increase

the starch dissolve percentage during an extraction

process (Wan Mohd Fariz et al. 2018). Finally, yet

importantly, an increase of pulp particle size resulted in a

decrease in the starch extraction efficiency since the pulp

has a complex structure (Saengchana, 2015). Therefore,

a study was conducted to identify the optimal grated

sago size to obtain high extracted native starch weight.

Figure 5, 6 and 7 show the native starch weight (MC:

10.33±0.55%) extracted from 2 g of dried grated sago

trunk (T, M and B section) according to sizes (X<0.30,

0.30 ≤ X< 0.45 mm, 0.45 ≤ X< 0.85 mm, 0.85 ≤ X< 1.00

mm, 1.00≤ X< 2.00 mm, 2.00 ≤ X <2.80 mm and X ≥

2.80 mm) at different steeping period  (5 mins, 24 hrs, 48

hrs and 72 hrs). The grated sago at the size of X<0.30

mm showed higher extracted native starch weight (0.71

g, 0.68 g, 0.67 g; T, M, B) compared to that of the size of

0.30 ≤ X< 0.45 mm (0.65 g, 0.60 g, 0.59 g; T, M, B) for

all sections with a significant difference (P<0.05).

Furthermore, the extracted starch weight at size 0.30 ≤

X< 0.45 mm also showed a significant difference

(P<0.05) compared to that of 0.45 ≤ X< 0.85 mm (up to

0.59 g; all sections) for the top section but with no

observed significant difference (P>0.05) for the middle

and bottom. The size from 0.45≤X<0.85 mm to

1.00≤X<2.00 mm did not show significant differences

(P>0.05) of extracted starch weight (ranging between

0.55 to 0.59 g) between sizes and sections. To further

elaborate, at size 1.00≤ X<2.00 mm and 2.00≤X<2.80

mm, based on observed showed no significant difference

(P>0.05) of extracted starch weight for T and M section

but observed otherwise for B trunk section (P<0.05).

Meanwhile, there was a significant difference (P<0.05)

in extracted starch weight between size 2.00≤X<2.80

mm and X≥2.80 mm. Overall, the bar graphs (Figure 5, 6

and 7) show the same distribution pattern of extracted

starch weight (g) according to the grated sago size

produced by the different sections of sago trunk (T, M

and B) at different steeping period. The extracted starch

weight showed an inversely proportional pattern to the

grated sago size: the larger the grated sago size, the less

native starch weight was recorded. The present study is

in agreement with Wan Mohd Fariz et al. (2018) in

which the finer size of grated sago produced higher

starch recovery compared to rougher size. Furthermore, a

similar starch extraction study by Tay et al. (2013) stated

that the increase of the mesh number (sieve mesh size

decreases) showed a significant increase of starch yield

due to the larger surface area that allowed more material

extraction into the steeping solution. Additionally, Mary

Anupama et al. (2010) also showed that smaller particle

size has contributed to a larger contact surface area,

resulting in an increase of starch yield during extraction.

The statistical analysis data (Table 1) showed that

the independent parameters (Trunk Section: TS, Grated

Sago Size: GS and Steeping Period: SP) and their

interaction parameters (TS*GS, GS*SP and TS*GS*SP)

significantly affected (P<0.05) the extracted starch

weight except for the interaction between TS*SP.

Furthermore, by comparing the F-values, the effect of

GS parameter on the extracted starch weight was the

most significant between the independent parameters

followed by the TS parameters. Meanwhile, TS*GS

interaction had the highest F-values compared to other

interactions since both of them had independent

parameters with the highest F-values. In addition, GS*SP

and TS*GS*SP interactions showed the lower F-values

because the interactions between independent parameters

were lower.

Although all the independent parameters and some

of the interactions showed a significant effect on the

extracted starch weight, the effect was very low when

compared to the F-values. In other words, it means that

there were groups of data that had no significant

difference in values. Therefore, Post Hoc Tests were

conducted by comparing the values between groups in

independent parameters, SP and TS. The data of multiple

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Figure 4. The WPR % of grated sago at different sieve mesh sizes (mm) according to trunk sections (T, M and B). Error bars

were expressed as mean ± SD; n = 6.

Figure 5. The extracted native starch weight at the top section (T) of sago trunk palm according to grated sago sizes (mm) at

different steeping periods (5 mins, 24 hrs, 48 hrs and 72 hrs). Error bars were expressed as mean ± SD; n = 6.

Figure 6. The extracted native starch weight at the middle section (M) of sago trunk palm according to grated sago sizes (mm)

at different steeping periods (5 mins, 24 hrs, 48 hrs and 72 hrs). Error bars were expressed as mean ± SD; n = 6.

Figure 7. The extracted native starch weight at the bottom section (B) of sago trunk palm according to grated sago sizes (mm)

at different steeping periods (5 mins, 24 hrs, 48 hrs and 72 hrs). Error bars were expressed as mean ± SD; n = 6.

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comparison between the steeping periods showed that

only the steeping period of 5 mins had a significant

difference (P<0.05) compared to other steeping periods

(24 hrs, 48 hrs, and 72 hrs), showing that there was an

increase in extracted starch weight when the steeping

period increased from 5 mins to 24 hrs. However, further

increase of the steeping period from 24 hrs to 48 hrs and

72 hrs did not yield a significant difference in the

extracted starch weight. The extraction reached

equilibrium beyond 24 hrs because when the steeping

period was at 24 hrs, most of the loose starch granules in

the trunk lignin were released (Tay et al., 2013). Another

possibility could due to the increased slurry viscosity

since the starch granules were hydrated for a longer

period, thereby allowing low release of starch (Mistry et

al., 1992).

Meanwhile, the data of multiple comparisons

between the trunk sections showed that the Top section

had a significant difference (P<0.05) of extracted starch

weight compared to the other sections. However, the

Middle and Bottom sections had no significant

difference of extracted starch weight due to the uneven

distribution of total starch content along the palm trunk

as shown in Table 5. The sago starch content distribution

depends on the palm tree’s maturity as reported by Jong

(1995b).

3.3 Extraction efficiency and starch recovery according

to grated size

The extraction process of native starch normally

used water as solvent to extract the starch from fiber

while the recovery efficiency depends on the grated sago

sizes. In order to determine the extraction efficiency, it is

necessary to determine the Total Starch Content (TSC) in

the fiber (grated sago) using chemical methods. Table 2

shows the TSC according to the trunk sections and the

extraction efficiency according to the grated sizes at

different steeping periods. The TSC showed no

significant difference between trunk sections (P>0.05),

ranging between 38.98 to 45.40%. Furthermore, the TSC

pattern between sections indicates that the palm trees

matured at stage nine (flowering stage), corresponding to

12.5 years old as reported by Jong (1995b). The results

showed that the sago trunk TSC was higher than an oil

palm trunk (2.12%) by assuming that the fresh input

material was at MC=74.00±4.58% (Yamada et al.,

2010).

Furthermore, the results showed that the highest

efficiency of extraction occurred when the steeping

periods is 24 hours for grated sago at the size of X<0.30

mm to all trunk sections  (the extraction efficiency were

52.87±1.12%, 56.95±0.70% and 58.06±0.47% for T, M

and B trunk sections respectively). In addition, there was

no significant difference of extraction efficiency between

the sections (P>0.05), showing that the selection of the

sago trunk section did not influence the extraction

efficiency because the grated sago sizes were the same.

Moreover, there were slight differences in extraction

efficiency between the grated sizes of X<0.30 mm and

0.30≤ X<0.45 mm (P<0.05). At the grated size of

0.45≤X<0.85 mm, the extraction efficiency began to

decrease until the size of 0.85≤X<1.00 mm and then

became constant at 1.00 ≤X<2.00 mm. Furthermore, the

extraction efficiency continued to decrease until X≥2.80

mm. This decreasing pattern happened because the

embedded native starch in smaller fiber size was easy to

be released. On the contrary, there was a slight increase

in extraction efficiency between 5 mins and 24-hour

steeping period (P<0.05) with an average percentage

difference of 1.80±1.13%. However, when the steeping

period was further increased from 24 to 72 hrs, the

increment of extraction efficiency was not significant

(P>0.05), meaning that the increase of extraction

efficiency with steeping period was stopped at a rate

beyond 24 hrs. This observation reflected the starch

recovery results as stated earlier since the extraction

efficiency depended on starch recovery weight, showing

a correlation between extraction efficiency and starch

recovery.

The total starch recovery is the total weight of sago

starch extracted from the grated sago which was a mix of

various sizes produced by the grating machine. Figure 8

shows the total starch recovery percentage for T, M and

B trunk sections at different steeping periods. The result

F
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Source DF Mean Square F Value P Value

Trunk Section 2 0.01 202.28 0

Grated Size 6 0.13 2367.96 0

Steeping Period 3 0 22.33 0

Trunk Section * Grated Size 12 0 53.21 0

Trunk Section * Steeping Period 6 0 2.56 0.02

Grated Size * Steeping Period 18 0 2.88 0

Trunk Section * Grated Size * Steeping Period 36 0 2 0

Table 1. Summary of ANOVA for mean extracted starch weight using different trunk sections, grated sago sizes and steeping

periods.

* Dependent Variable:   Extracted starch weight

1177

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eISSN: 2550-2166 © 2020 The Authors. Published by Rynnye Lyan Resources

showed that the total starch recovery was not significant

(P>0.05) between the steeping period with average

values of 19.86±0.14%, 19.03±0.08% and 19.03±0.11%

for T, M and B sections, respectively. The total starch

recovery was higher than obtained by Wan Mohd Fariz

et al. (2018) at about 7.73% to 9.5%. However, it was

slightly lower compared to a prior study by Siti Mazlina

et al. (2007) (25.76%). The difference might be due to

the wet grading process, causing an increased percentage

of ruptured sago trunk structure bonding. Siti Mazlina et

al. (2007) noted that the starch granules present in the

sago pith were subsequently released when they were

ruptured during the grinding process.

For further comparison, several previous studies

used wet-base starch as the calculation of starch recovery

input value. Therefore, the calculated values of starch

recovery using the wet-base as the input values ranged

from 24.04% up to 25.15% at MC of 35.80±0.43%

(starch MC before drying) for the present study. The

obtained values were in close agreement with Flach

(1997) and Darma et al. (2014) in which the starch

recovery ranged from 10 to 25% and 12.43 to 39.89%,

respectively. Furthermore, Darma et al. (2017) reported

that their starch recovery ranged from 23 to 27%, 15 to

25%, 35.45% and 43 to 48%, respectively. The variation

of starch recovery obtained between the studies might be

due to different grated sago sizes and extraction

methods. For the present study, the water extraction

method was conducted without repetition to ensure

optimal usage of water. Basically, the conventional sago

extraction method consumed high amounts of water due

to the repetition of adding water to grated sago (Jong,

1995a). Water was added during the extraction process

as a key element to dissolve and release the starch

granules from the pith (Kamal et al., 2007).

4. Conclusion

The result of the study showed that a substantial

amount of starch could be extracted from the grated sago

by reducing the grated size to X<0.30 mm, allowing up

to 58% efficiency of extraction. A smaller size of grated

sago facilitates the high release of native starch.

F
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S
ectio

n

Total
starch

content
(%)

Grated sago
size

Steeping period

5 min 24 hours 48 hours 72 hours

Starch
recovery

(%)

Efficiency
(%)

Starch
recovery

(%)

Efficiency
(%)

Starch
recovery

(%)

Efficiency
(%)

Starch
recovery

(%)

Efficiency
(%)

T
o
p

45.4

X<0.3 23.27 51.26 24.03 52.92 24.38 53.7 24.32 53.58

0.3≤X<0.45 21.71 47.83 22.52 49.61 22.53 49.63 22.74 50.1

0.45≤X<0.85 19.59 43.15 19.08 42.03 19 41.86 19.19 42.27

0.85≤X<1 18.94 41.71 18.94 41.71 19.04 41.93 19.08 42.03

1≤X<2 18.26 40.23 18.47 40.69 18.79 41.4 18.65 41.08

2≤X<2.8 17.61 38.79 18.25 40.2 18.32 40.35 18.41 40.54

X≥2.8 17.05 37.55 17.42 38.38 17.5 38.55 17.42 38.38

M
id

d
le

39.83

X<0.3 22.46 56.37 23.08 57.93 22.69 56.96 22.52 56.54

0.3≤X<0.45 19.73 49.54 20.29 50.94 19.94 50.07 19.66 49.35

0.45≤X<0.85 19.29 48.43 19.18 48.15 19.48 48.9 19.49 48.93

0.85≤X<1 18.69 46.93 18.52 46.49 18.64 46.79 18.98 47.65

1≤X<2 18.44 46.29 18.61 46.71 18.31 45.96 18.54 46.54

2≤X<2.8 17.49 43.9 18.01 45.21 18.03 45.27 17.39 43.65

X≥2.8 16.77 42.1 16.92 42.49 17.38 43.63 16.99 42.66

B
o

tto
m

38.97

X<0.3 22.37 57.4 22.77 58.42 22.74 58.37 22.62 58.05

0.3≤X<0.45 19.63 50.37 20.25 51.98 20.12 51.64 20.15 51.72

0.45≤X<0.85 19.28 49.48 19.45 49.91 19.65 50.42 19.67 50.47

0.85≤X<1 18.47 47.41 18.83 48.32 18.65 47.86 18.93 48.57

1≤X<2 18.45 47.35 18.62 47.78 18.46 47.38 18.53 47.55

2≤X<2.8 17.6 45.17 17.64 45.28 17.8 45.68 17.46 44.8

X≥2.8 16.81 43.15 17.01 43.66 17.04 43.72 17.19 44.11

Table 2. Chemical determination of TSC according to trunk sections and extraction efficiency according to grated sizes at

different steeping periods

Figure 8. The starch percentage recovery (%) produce by

grating machine. Error bars were expressed as mean ± SD;

n = 6.

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eISSN: 2550-2166 © 2020 The Authors. Published by Rynnye Lyan Resources

Independent variables such as grated size affected the

starch recovery the most. Furthermore, in order to

increase the recovery, it is suggested to increase the

steeping period up to 24 hrs but further increment of

steeping period is not necessary. The selection of sago

trunk also affected the starch recovery, but not the

extraction efficiency. Lastly, it is believed that further

development in extraction techniques will improve the

starch recovery and at the same time minimize the

extraction period.

Acknowledgement

The authors would like to express gratitude for the

research financial support by CRAUN Research Sdn Bhd

and MARDI (Project code: FS024210). A special

appreciation to the team members from MARDI and

UPM facilities in providing suggestions, encouragements

and coordination to this project.

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