A facile and efficient pressing method for improvement of chitin production

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58 • NHA TRANG UNIVERSITY

A FACILE AND EFFICIENT PRESSING METH OD

FOR IMPROVEMENT OF CHITIN PRODUCTION

Nguyen Cong Minh1, Pham Thi Dan Phuong2, Nguyen Van Hoa2,Trang Si Trung,2,*

Received: 01/8/2016; Revised: 20/9/2016; Accepted: 26/9/2016

ABSTRACT

Shrimp head waste has been used as raw materials for production of chitin and protein hydrolysate. In 
this study, a facile and efﬁ cient pressing method was developed to separate the solid and liquid phases from 
shrimp heads. The different solid/liquid ratios as well as the size of the solid component can be obtained easily 
by changing the pressing operating parameters. The solid fraction was used to prepare chitin and chitosan. 
This pressing method can save large amount of water and chemicals in the production of chitin and it can be 
used in the large-scale.

Keywords: shrimp head waste, chitin, pressing method, protein hydrolysate

1 Institute of Biotechnology and Environment, Nha Trang University 
2 Faculty of Food Technology, Nha Trang University

* Corresponding author: 
I. INTRODUCTION

Shrimp head waste is considered as a
source of valuable components including about
6% chitin and 66% protein on the dry basis of
the raw material [4,5,8]. In the original form,
chitin is linked to proteins by glycosidic bonds.

Therefore, the fabrication of chitin requires
deproteinization process which is commonly
accomplished by using alkali solution. However,
it is known that severe alkali treatment results
in degradation of chitin polymer chains
and also reduces the quality of the protein
hydrolysate [9,10].

So far, industrial methods use chemical
processes for preparation of chitin from shrimp
shells involving: (i) grinding; (ii) demineralization
with strong acids; (iii) deproteinization with
alkali medium at 90-1000C; (iv) pigment 
removal using solvent extraction or chemical
oxidation [2,3]. Unfortunately, this process
often consumes a large amount of chemicals
and water due to the remaining protein
and others from shrimp meat and viscera.
Moreover, this organic fraction can cause an
environmental issue.

Based on the above problems, it is necessary
to develop a facile and efﬁ cient method for
pretreatment of shrimp waste before the
production of chitin. In this study, a pressing
method was used to separate the shrimp head
waste into two fractions, solid and liquid, with
various solid/liquid ratios. The solid fraction
contains chitin and small amount of protein
and minerals that was used to prepare chitin.

This pressing step helps to consume smaller
amounts of water and chemicals, which were
used to produce chitin.

II. MATERIALS AND METHODS

1. Materials and chitin production

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NHA TRANG UNIVERSITY • 59
deproteinized by 4 wt.% NaOH to fabricate

chitin. For rough comparison, the collected
shrimp heads were directly used to produce
chitin using the same acid and alkaline
solutions without a pressing step.

2. Proximate Analysis

The moisture was measured by the weight
loss during drying the samples at 105oC for 24 h. 
Ash was determined by burning the samples
at 600oC in a mufﬂ e furnace [1]. Protein of 
shrimp was measured by Kejldahl method [1].
Protein of chitin was measured by using the
standard micro-Biuret protein assay using

bovine serum albumin as standard. Astaxanthin
was determined according to the method of
Simpson and Haard [6]. The degree of
deacetylation (DD) was measured according

to Tao and Svetlana [7]. Typically, 100 mg
chitosan was dissolved in a 20 mL concentrated
H3PO4 solution (85%) at 600C for 40 mins. 
Then, 1 mL above solution was diluted with
25 - 30 mL distilled water (25-30 times) and
kept at that temperature for 2h. After cooling
down to room temperature, samples were
measured at 210 nm. The DD was calculated
according to the following equation (1) and (2):

DD = 100 *

[

1-

mM Glc NAc

]

(1)

mM Glc NAc + mM Glc

mM Glc =

w - mM Glc NAc * 0.2032

(2)

0.16117

where w is the sample weight (mg) in 1 mL, 0.2032 is the factor to convert the amount of l mol/mL
anhydro Glc NAc moiety in the sample into mg anhydro NAc moiety in 1 mL. For Glc, this factor
amounts to 0.16117. mM Glc NAc was calculated according to standard curve of Glc NAc.

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60 • NHA TRANG UNIVERSITY
III. RESULT AND DISCUSSION

Table 1 shows the composition of shrimp
head waste, liquid and solid fractions at four
different liquid/solid ratios of 30:70, 40:60,
50:50 and 60:40. The protein, ash and chitin
contents are 55.3, 23.4, and 15.7 wt.% (dry
basis). This is in agreement with previous

published papers on the similar shrimp waste
sources [2, 8-10]. By using different pressing
conditions, the compositions of both obtained
liquid and solid fractions were changed. In
the liquid fraction, when the liquid/solid ratios
increased from 30:70 (liquid 1) to 60:40 (liquid 4),
the protein content was increased from 58.2

to 60.2 wt.%, respectively. Similarly, the
chitin content increased from 9.2 to 10.3 wt.%
as increase in the liquid/solid ratio from 30:70
to 60:40, respectively. It can be attributed to the
crumby of shrimp head waste with small solid
pieces presented in the liquid fraction. The
astaxanthin amount increased signiﬁ cantly
from 335.3 to 342.4 ppm as increase of the
liquid/solid ratio from 30:70 to 60:40, respectively.
On the other hand, in the solid fraction, the
moisture content is a range of 68 - 77% which
is lower than that of shrimp head (81,6%). The
protein content is approximately 55 wt.% for all
samples at different solid/liquid ratios.

Figure 2. The diagram of pressing process. (1) Feeder, (2, 3) Rollers, (4) Cable-stayed

Table 1. The composition of shrimp head waste, liquid 
and solid fractions at different pressing processes

# Pressing ratio (Liquid/Solid) Weight (kg) Moisture (wt.%) Protein (wt.%)* Ash (wt.%)* Chitin (wt.%)* Astaxanthin (ppm)* pH

1 NA 10 ± 0.05 81.6 ± 1.2 55.3 ± 1.4 24.4 ± 0.8 17.5 ± 1.3 155.2 ± 24
2

30/70 3.0 ± 0.03 94.2 ± 0.3 58.2 ± 0.3 23.0 ± 0.5 9.2 ± 0.7 335.3 ± 14 6.9
3 7.0 ± 0.04 77.2 ± 1.4 55.8 ± 0.5 22.8 ± 0.4 18.5 ± 0.5 135.1 ±15
4

40/60 4.0 ± 0.04 93.7 ± 0.5 58.1 ± 0.5 21.0 ± 0.6 9.5 ± 0.6 326.2 ± 20 7.1

5 6.0 ± 0.05 75 ± 1.5 55.1 ± 0.6 22.9 ± 0.5 18.1 ± 0.4 134.3 ± 16

50/50 5.0 ± 0.02 93.2 ± 0.3 59.0 ± 0.5 20.0 ± 0.4 9.5 ± 0.4 337.7 ± 15 7.3
7 5.0 ± 0.03 70.8 ± 1.7 55.2 ± 0.8 23.1 ± 0.3 19.5 ± 0.5 134.2 ± 16
8

60/40 6.0 ± 0.02 92.8 ± 0.4 60.2 ± 0.7 20.1 ± 0.5 10.3 ± 0.2 342.4 ± 22 7.3

9 4.0 ± 0.04 68 ± 0.8 56.2 ± 0.4 23.2 ± 0.4 20 ± 0.3 134.1 ± 18

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Table 2 shows the comparison of total
amount of chemicals and water, which are
used for chitin production from 10 kg of raw
material with and without pressing step. In the
demineralization process, the consumed HCl
volumes were 3.7, 3.3, 2.6 and 2.2 L by pressing
at liquid/solid ratios of 30/70, 40/60, 50/50 and
60/40, respectively. In the deproteinization
process, the consumed NaOH amounts

were 1.4, 1.2, 1.0 and 0.8 kg by pressing at
liquid/solid ratios of 30/70, 40/60, 50/50 and 60/40,

respectively. However, it required 5.4 L
of HCl and 2 kg of NaOH for production of
chitin without pressing. Therefore, this
pressing process can save up to 60% amount
of acid and alkaline. In addition, large amount
of water can be saved by using pressing
process. The consumed water volume were
64.3, 56.8, 45.5 and 38.8 L by pressing at
liquid/solid ratios of 30/70, 40/60, 50/50 and
60/40, respectively, which were much lower
than that of no pressing (94.6 L).

Table 2. The comparison of amount of chemicals and water used for chitin production

No pressing Pressing 1 Pressing 2 Pressing 3 Pressing 4

Sample (kg) Before pressing 10.0 ± 0.05 10.0 ± 0.05 10.0 ± 0.05 10.0 ± 0.05 10.0 ± 0.05

After pressing 10.0 ± 0.05 7.0 ± 0.02 6.0 ± 0.01 5.0 ± 0.03 4.0 ± 0.03

Demineralization

VHCl (L) 50.0 ± 0.2 34.0 ± 0.1 30.0 ± 0.1 24.0 ± 0.1 20.5 ± 0.5
H2O (L) 44.6 ± 0.3 30.3 ± 0.4 26.8 ± 0.3 21.4 ± 0.5 18.3 ± 0.3
VHCl 37% (L) 5.4 ± 0.2 3.7 ± 0.1 3.3 ± 0.2 2.6 ± 0.1 2.2 ± 0.1

Deproteinization

VNaOH (L) 50.0 ± 0.5 34.0 ± 0.4 30.0 ± 0.2 24.0 ± 0.4 2 ± 0.5
H2O (L) 50.0 ± 0.5 34.0 ± 0.4 30.0 ± 0.2 24.0 ± 0.4 2 ± 0.5
mNaOH (kg) 2 ± 0.1 1.4 ± 0.1 1.2 ± 0.1 1.0 ± 0.1 0.8 ± 0.1
Table 3 presents the properties of chitin

which was prepared from shrimp head waste
before and after pressing at different liquid/
solid ratios. All obtained chitins have the same
light pink color and similar DD (about 9.5 wt.%).
However, the content of protein and ash is
reduced signiﬁ cantly by using pressing step.
The protein content is 0.82% for the case
without pressing and it reduces to 0.76, 0.74,
0.70 and 0.68 wt.% at liquid/solid ratios of
30/70, 40/60, 50/50 and 60/40, respectively.
The ash content is reduced from 0.76%

(no pressing) to 0.68, 0.65, 0.65 and 0.56% at
liquid/solid ratios of 30/70, 40/60, 50/50 and
60/40, respectively. On the other hand, when
the liquid/solid ratio increased, both the amount
of chemicals used and the size of chitin were
reduced so much. Based on obtained results,
although there is not much different result
among samples from pressing processes, the
liquid/solid ratio of 50/50 is recommended to
get high quantity chitin as well as save amount
of chemicals and water.

Table 3. Properties of chitin prepared from different raw materials

Parameter Chitin

Chitin 0 Chitin 1 Chitin 2 Chitin 3 Chitin 4

Color Light pink Light pink Light pink Light pink Light pink

Appearance Flake, tough Flake, tough Flake, tough Flake, tough Flake, crumby

Ash (wt.%) 0.76 ± 0.2 0.68 ± 0.1 0.65 ± 0.3 0.65 ± 0.1 0.56 ± 0.2

Protein (wt.%) 0.82 ± 0.1 0.76 ± 0.4 0.74 ± 0.2 0.70 ± 0.3 0.68 ± 0.3

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62 • NHA TRANG UNIVERSITY
IV. CONCLUSION

A facile and efﬁ cient pressing method was
developed to separate shrimp head waste into
solid and liquid fractions with different ratios.
This step encourages using smaller amounts
of chemicals and water in the production of
chitin. The solid/liquid ratio of 50/50 is the most
suitable condition to produce high quantity

chitin. This method is potential way to apply in
the large scale.

ACKNOWLEDGMENT

The authors wish to thank the Ministry of
Science and Technology, Vietnam for their kind
funding to this research.

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