MINISTRY OF EDUCATION AND TRAINING
NHA TRANG UNIVERSITY
DAO TRONG HIEU
STUDY ON THE CHANGES OF CHEMICAL
COMPOSITION, PHYSICAL PROPERTIES AND PROPOSED
MEASURES FOR IMPROVING THE QUALITY OF DRIED
ANCHOVIES (Spratelloides gracilis) BY INFRARED DRYER
FOR EXPORT
Speciality: Seafood processing technology
Code:
62 54 01 05
ABSTRACT OF PHD THESIS
KHANH HOA – 2013
The thesis was completed at Nha Trang University
Supervisors:
1. Prof.Dr. Tran Thi Luyen
Nha Trang University
2. Ass.Prof.Dr. Ngo Dang Nghia
Nha Trang University
Defence 1: Prof. Dr. Nguyen Thi Hien
Defence 2: Prof. Dr. Nguyen Trong Can
Defence 3: Dr. Do Van Ninh
The thesis was defended at Thesis Assessment Committee of Nha
Trang University
at 8.30am, date 29 month 03 year 2013
The thesis can be found at:
- National library
- Library of Nha Trang University
1
INTRODUCTION
1. Rationale
Mainly, the exported items of Vietnam fisheries products are
frozen and dried ones. However, technology of dried fish
processing particularly for anchovy is mainly sun dried, heat
emitted from brazier or gas sources, therefore quality of the
products is not high, high proportion of byproduct, unstable
quality lead to reduce economic efficiency.
Thus there is a need to seek and apply new technology and
methods for drying fish are necessary for current state while
quality and hygiene of fish products are being paid more and
more attention.
Technology of the selective infrared ray (IR) is one of new
technologies, which having number of advantages such as:
reduce drying time, low temperature of dry therefore dried
products have low rate of weight loss and ensure quality;
product
surface
sterilized,
product
preservation
longer;
guarantee hygiene for food products as well as for human and
environment...
Based on the significance and actual requirements
mentioned above, the project of ”Study on the changes of
chemical composition, physical properties and proposed
measures for improving the quality of dried anchovies
(Spratelloides gracilis) by infrared dryer for export” aiming to
modernize drying technology for fisheries, save time and
energy, improve quality and economic efficiency of dried fish
products.
2
2. Scientific and realistic significances of the thesis
Results of the thesis will contribute more to scientific base
for seafood drying technology, will be references and
documents used for training activities in seafood processing
field. Provide new drying method for seafood processing
enterprises in Vietnam.
3. Objectives of the study
The objective of the thesis is to study the changes of some
physical
characteristics,
chemical
components,
sensory
properties and micro-organisms of dried anchovy product
during drying process by the selective IR method, propose a
drying technology for anchovy which quality assurance, food
safety and economic efficiency.
4. Contents of the study
1) Define some basic chemical components, physical
characteristics, micro organisms of fresh anchovy;
2) Conduct study on changes of some chemical components,
physical characteristics, sensory
properties and micro-
organisms of dried anchovy product during drying process by
the selective IR method;
3) Determine the appropriate drying mode and build process
of drying technology with selective IR for anchovies;
4) Compare the quality of dried anchovy by the selective IR
with different methods (sun drying, hot air);
3
5) Primarily estimate production cost of 1 kg dried anchovy
by the selective IR, assessment and analyse feasibility of this
technology;
6) Propose some solutions to improve quality of dried
anchovy in general and by the selective IR in particular.
5. The new conclusion of the thesis
- Provide a set of data of chemical components, physical
characteristics, micro-organism of anchovy caught in Khanh
Hoa’s seawater;
- Define changes in criteria of quality of anchovy during dry
process by the selective IR;
- Propose a process of anchovy dried by the selective IR and
compare quality of anchovies dried by IR with other methods
such as sun drying, hot air.
6. Structure of thesis
The thesis includes 154 pages, divided into 3 chapters, 47 tables
of data and 43 pictures/figures and 138 references in which 33
in Vietnamese and 105 in English.
4
Chapter I.
LITERATURE REVIEW
The industry of fish processing in Vietnam has achieved a
considerable achievements, number of fish processing plants
increased rapidly, huge capacity of production, large consumed
markets for fish products, total fisheries exported turnover has
been increasing continuously for years. In order to meet the
growth objectives of the sector in the near future, improvement
of product’s quality, reduce post harvest loss, investment in
deep processing, production of value added products, ensure of
products’ higiene and improvement of economic efficiency are
interested.
Vietnam’s main fisheries exported items are in frozen and
dried forms. Among dried products, anchovy account for an
important proportion in terms of volume and value. However,
the current technology of dry for anchovy are handicraft,
majorly sun dried and some dried by heat released by brazier,
therefore, the quality of the product is not high, proportion of
production loss is high and hygiene is not ensured as well as
problems with environmental pollution...
Technology of IR, especially the selective IR has been
applied widely in food industry, particularly in dry, grill and
sterilization for agriculture products due to it has many
advantages such as fast, quality and hygiene of the products
guaranted, stored duration of the products can be extended,
equipments are small, safety and easy to control, have little
impacts to human and environment...
5
Study object is anchovy is a species which has high catch
and values of nutrien and economics, small size, relatively
uniform, thus they are suitbale to use the IR for drying
(disavantage of IR is weak capacity of penetration).
Applications of IR, particularly the selective IR in dry fish in
Vietnam and on the world are limited. Majorly, studies stopped
at applications of normal methods of IR (wide spectrum) such
as infrared light, resistive wire,… in dry agriculture products.
Futhermore, these studies aimed to find out the optimum regime
of fish dry by changes specifications such as temperature, wind
speed, distance from source of IR to dried items, thickness of
dried items. So far, there has not been any study done which are
sufficient and systematic assessments on effects of these factors
including chemical components, physical characteristics, microorganisms and sensory quality of anchovy during the selective
IR dried process.
Therefore, this study is to assess the impacts of following
factors: temperature, radiated distance of IR and wind speed
during fish dried by the selective IR, and propose technological
process for high quality anchovy dried which meet the current
hygiene requirements, safety, and environmental pollution free
and improve economic efficiency for dried fish products in
general and for dried anchovy in particular are significane
works in both senses of sciences and reality.
6
Chapter 2.
RESEARCH SUBJECT AND METHODS
2.1. Research subject
Research subject of the thesis is a spcies of anchovy: Order
Clupeiformes; Family Clupeidae; Genus Spratelloides; Species
S.gracilis. This species is captured in Khanh Hoa’s seawater
with
average
forklength
of
5-7cm,
fresh
and
whole
body/individual.
2.2. Research methodology
Methods used in this study are normalized, and modern
methods used such as: use of radiated equipments of the
selective wavelength, high pressure liquid chromatography, gas
chromatography, electronic microscope.
Descriptive analysis and statistical softwares were used
including Modde 5.0, Design Expert 8.0 to develop models
and find out optimum parameters during fish dried following
guidance of Box-Wilson’s method.
2.3. Research materials
- IR equipments with ceramic bars which allow to select
wavelengths were used, liquid chromatography and gas
chromatography; equipment of NH3 distiling; electronic
microscope; some relevant portable measurement devices and
laboratory equipments.
- All chemicals and adjuvants used for the research have
clear origin, highly pure, ensure accuracy for analysed criteria.
7
Chapter 3.
RESULTS AND DISCUSSION
3.1. Results of analysis of
some chemical components,
physical characteristics and micro-organisms of research
material – anchovy.
Results showed that the anchovy has water of 74.7%, protein
of 20.05%, lipid of 1.8%, minerals of 2.2%, NH3 4.65mg/100g
and histamine of 3.5ppm. Meat of this anchovy species has 30
fat acids in which SFA accounts for 44.0%, PUFA (32.0%) and
MUFA (24.0%). And this pecies has 18 amino acids, with 7 of
unreplaceble amino acids and totaly accounts for 11.57%.
Structure of the fresh anchovy’s texture is relatively loose.
Criteria of micro-organisms met current requirements, with total
aerobic micro-organisms of 5.4x105 cfu/g.
3.2.
Changes
in
chemical
components,
physical
characteristics, perception and micro-organisms of anchovy
dried by the selective IR
After treament (washing, boiling), fish were taken and
placed in dried equipment of the selective IR, fish were dried
following experiments designed (distance from materials to
sources of IR is changing from 5 – 25 cm, temperature dried of
40 – 70 oC; wind speed of 1 – 3 m/s). Results of analyses of
hanges in dried duration, chemical components, physical
charateristics, perception and micro- organisms are presented in
the following parts:
8
3.2.1. Variation in dried durarion of anchovy by the selective
IR (Y1)
Results of study about variation in dried duration of anchovy
with the selective IR method, in the required moistureity of
(20±2%) can be reflected by the following regression equation:
Y1 = 5.86 + 0.69x1 - 0.94x2 + 0.94x3 + 0.3x1x3 – 0.3x2x3 (3.1)
When the temperature (x2) increases then fish dried duration
decreased. High wind speed (x3) fast formulate a hard layer
cover the surface of the product which blocks the internal
diffusion lead to partial moisture happened, thus dried duration
is longer and the longer the distance between fish and source IR
(x1) the longer time for fish dried.
3.2.2. Variation in structure of fish texture (Y2)
Results of pictures taken by elec-microscope showed that
dried temperature and windspeed have significant impacts to
structure, the higher dried temperature and windspeed, the more
solid structure of fish texture and darker color, muscle fibres
distributed discretely, some parts contracted lead to higer fibre
density and form more solid organizations.
3.2.3. Variation in capacity of re-absorbent (Y3)
Study results of capacity of re-absorbent (%) of anchoby
dried by the selective IR is reflected by the following equation:
Y3 = 63.98 – 5.37x2 – 2.75x3 + 1.85x1x2 (3.2)
The factor of distance seems not effect on re-absorbent of
fish dried. Temperature has significantly effect, when
temperature highly increased the proportion of protein
denatured more, the solid struture of fish texture lead to
considerably reduce capacity of re-absorbent. Similarly,
9
windspeed also make fish high dehydration at the surface of the
fish texture, the holes of capillary were blocked therefore the reabsorbent of dried fish’s meat decreased.
3.2.4. Variation in total content of protein(Y4)
Variation in total content of protein (%) of anchovy dried by
the selective IR is described in the following regression
equation:
Y4 = 61.13 + 0.175x1 – 0.35x2 - 0.175x3 + 0.25x1x2 (3.3)
Temperature factor has biggest effect on the total content of
protein, when temperature increased the total content of protein
decreased, followed by dried windspeed and radiated distance.
When the radiated distance decreased and windspeed increased
the external diffusion increased lead to the surface meat of the
fish strongly and fast dehydration and protein diffusion,
promote reactions of generating colour and smell compounds
lead to loose a certain amount of amino acids. However, totally
the total content of protein of the anchovy dried by the
seclective IR changed minor according to the dried regime
(only 60.2 – 61.8%).
3.2.5. Variation in total content of amino acids (Y5)
Variation in the total content of aminacid of anchovy dried
by the selective IR is descibed in the following regression
equation:
Y5 = 39.24 + 0.175x1 - 0.35x2 - 0.175x3 + 0.25x1x2 (3.4)
Factor of temperature has biggest impact on the total content
of amino acids; temperature increased the content of aminacid
decreased, followed by windspeed and radiated distance, when
10
radiated distance decreased, windspeed increased, the external
diffusion increased lead to surface meat of fish fast dehydration
and protein denatured and promote reactions of generating
colour and smell compounds which made some certain amount
of amino acids lost. Nevertheless, total content of protein of
anchovy dried by the selective IR varied little, only from 38.28
– 39.88%.
3.2.6. Variation in total content of lipid lipit (Y6)
Variation of total content of lipid (%) of the anchovy dried
by the selective IR is described in the following equation:
Y6 = 6.65 + 0.113x1 – 0.238x2 - 0.138x3
(3.5)
Temperature factor has strongest impacts on total content of
lipid, when temperature increased total content of lipid
decreased. Radiated distance and windspeed also effected total
content of lipid of anchovy. Radiated distance decreased,
windspeed increased lead to increase in external diffusion, the
surface layer of fish fast dehydrated which made lipid denatured
and promote oxidation reactions of generating colour and smell
compounds that made a certain amount of amino acid lost.
However, total content of lipid of anchovy dried by the
selective IR was not significantly changed by dried regimes
(only varied from 6.1 to 7.1%).
3.2.7. Variation in content of unsaturated fatty acid (PUFA)
(Y7)
Variation in content of unsaturated fatty acid of anchovy
dried by the selective IR is reflected by the following regression
equation:
Y7 = 29.04 + 0.31x1 – 1.14x2 – 0.51x3 + 0.16x1x2 (3.6)
11
Factor of temperature had largest effect on content of PUFA,
followed by windspeed and infrared distance. With the
experiments designed under this study, PUFA varied from 26.6 –
30.7%. This change was not considerable due to short dried time,
on the other hand, IR has capacity to made micro-organisms and
enzyme motionless... therefore they had a litte effect on the
content of PUFA.
3.2.8. Variation in content of NH3 (Y8)
Study result of variation in content of NH3 (mg/100g) of
anchovy dried by the selective IR is described in the following
regression equation:
Y8 = 11.26 + 0.675x1 – 0.9x2 + 0.8x3 + 0.3x1x3 – 0.275x2x3 (3.7)
Variation in content of NH3 during dried duration was not
significantly due to short dried time, and ability of motionless
of micro-organisms and enzyme lead to slowdown formulation
of NH3. However, temperature is factor that had largest impact
on formulation of NH3, when temperature increased the capacity
of motionless of mirco-organism and enzyme significantly
increased and dried duration shortern therefore the content of
NH3 slightly increased, this increasing is relatively, mainly due
to de-hydration of the product. Windspeed is a factor which
promotes process of oxidation lead to increase content of NH3
when windspeed in the dried chamber. When infrared distance
descreased, dried time would be shortern lead to increase
content of NH3 little.
3.2.9. Variation in content of histamine (Y9)
12
Variation in content of histamine (ppm) of anchovy dried by
the selective IR is described in the following regression
equation:
Y9 = 7.31 + 0.85x1 – 1.12x2 + 1.03x3 + 0.39x1x3 – 0.41x2x3 (3.8)
Temperature has largest impact on content of histamine,
when
temperature
increased
the
content
of
histamine
descreased, infrared distance descreased and windspeed
descreased lead to dried duration shortern, enzyme and microorganisms becoming rapidly motionless or reduce activeness
therefore the formulation of histamine slowdown. The content
of histamine of anchovy dried by the selectibve IR in different
dried regimes was varying from 5,22 – 11,07ppm, this content
was very low compared to content of histamine allowed in
fisheries products (100 ppm- Decision No 2670/QĐ-BNNQLCL dated August 29th 2008).
3.2.10. Variation in perceptile quality (Y10)
Variation in sensory quality (score) of anchovy dried by the
selective IR can be described in the following regression
equation:
Y10 = 18.93 + 0.175x1 – 0.35x2 - 0.175x3 + 0.25x1x2 (3.9)
The infrared distance and windspeed have not much effect
on sensory quality of the product, however they have more
effect in condition of high temperature and short distance
infrared. Temperature is the factor which has the largest impact,
when temperature increased, proportion of denatured protein
increased, structure of fish texture becoming solid, reactions of
formulation colur and smell compounds...significantly effect on
characteristics of product’s perception. Nevertheless, majorly
13
product of anchovy dried by the selective IR is remained in
good band score (>18.6 - TCVN 3215-79), only two
experiments got products of level fairly good. The study results
shown that the anchovy dried by the selective IR can have good
sensory quality.
3.2.11. Variation in micro-organisms (Y11)
The following regression equation presents the variation in total
micro-organisms (cfu/g) of anchovy dried by the selective IR:
Y11 = 207.73 + 25.62x1 – 173.13x2 (3.10)
Dried temperature has biggest impact on total aerobic microorganism. At the same infrared distance and wind speed (k =
5cm and v = 1m/s), at dried temperature of 400C, total aerobic
bacterial of 3.3x102CFU/g but at 70oC total aerobic bacterial
remained only 0.25x102CFU/g. Infrared distance also impacted
on total aerobic bacterial, the shorter infrared distance lead to
micro-organisms absorb radiated energy more and killed more.
Wind speed also effect on total aerobic micro-organisms, when
wind speed increased number of total aerobic bacterial
increased, however this impact was not significantly (P< 0.05).
Process of experiments, analyses of criteria of chemical,
physics, perception and micro-organism of anchovy dried
by the selective IR showed that the criteria of chemical
varied little, sensory quality
of product is good, and
particularly the micro-organisms decreased significantly
after fish dried. With the above results, the selective IR has
far advance for dry fisheries products compared to the
other method currently used now in Vietnam.
14
3.3. Optimization of stages of anchovy dried by the selective
IR
Results presented in section 3.2 showed that quality of fish
dried by the selective IR in different dried regimes (k = 5 25cm, t = 40 - 700C, v = 1 - 3m/s) were good, criteria of
hygiene were guaranted in allowable thresholds. Thus the
purpose of optimization of dried stages is to find out reasonable
infrared distance, temperature and wind speed to reduce dried
duration and cost of energy consumed.
Estimated outputs based on model and experiments showed
that the optimum regime for silve stripe round herring dried by
the selective IR was: distance from source of IR (ceramic bar)
to matterial was 10 cm; temperature in the dried chamber was
55 oC; wind speed throught matterial was 1.4 m/s. With this
regime, it took 3.5 hours, the fish’s moisture met requirement
(20±2%) and also ensured fish quality.
6
5.5
h o i g ia n s a y
Drying Ttime(hr)
5
4.5
4
3.5
3
1.00
30.00
1.50
36.00
2.00
42.00
48.00
0
Temperature
B: Nhiet do ( C)
2.50
54.00
Wind
(m/s)
A: Toc go speed
gio
60.00 3.00
Figure 3.15. Model of relationships between factors and
drying duration in optimum drying regime
15
90.0
20.0
80.0
Đ ộ ẩ m (% )
70.0
T ố c đ ộ s ấ y (% W / h )
y = 79.389e-0.3587x
R2 = 0.9896
60.0
50.0
40.0
30.0
20.0
10.0
0.0
18.0
16.0
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0.0
10.0
Thời gian sấy (h)
20.0
30.0
40.0
50.0
60.0
70.0
80.0
Độ ẩm (%)
(a)
(b)
Figure 3.16. Drying curve (a) and drying velocity (b) of
anchovy dried by the selective IR in optimum conditions
3.4. Propose process of the selective IR dry for anchovy
Based on the research results, process of dy by the selective
IR for anchovy can be described as figure 3.17.
Raw Materials
- Saline 2-3%
- Add salt, replace
water
Washing
Boiling
- Radiated distance IR:
10cm
- Drying temperature: 550C
- Wind speed: 1,4m/s
- Fresh fish, whole body
- Size 5-7cm
- preservation by grilled ice
- Boiling water: 1000C
- Time: 5 minutes
IR drying
Product
Packaging
- Cold storage: - 18±2 0C
- Time: 12 months
- 3kg/PE
- Put in Carton box
Preservation
Figure 3.17. Process of dry by the selective IR for anchovy
16
3.5. Comparision of fish quality by different drying methods
3.5.1. Some basic chemical criteria
Samples of the anchovy dried by three methods: Infrared
(IR), Hot Air (HA), Sun Drying (SD) were analysed chemical
components. Analysis results are presented in table 3.37.
Table 3.37. Basic chemical components of fish (% dried
substances)
Rank
Criteria
Unit
Drying methods
IR
HA
SD
1
Moisture
%
22.10 22.50 22.30
2
Total protein
%
61.02 59.25 58.54
3
Total amino acid
%
39.23 36.26 36.65
4
Total lipid
%
7.03
5
Fatty acid
%
28.50 26.40 27.40
%
11.32 11.42 11.51
PUFA/∑FA
6
Minerals
7
NH3
8
Histamine
6.62
6.48
mg/100g 12.08 16.53 29.38
Ppm
5.23
8.54
16.73
3.5.2. Some physical criteria
1) Structure of fish texture
Different methods of fish dried lead to significant
differences in fish texture. Study results are presented in figure
3.19.
17
(a)
(b)
(c)
(d)
Figure 3.19. Texture of raw material (a), dried fish by SD
(b), dried fish by HA (c) and dried fish by IR (d)
2) Proportion of re-absorb water
Proportion of re-absorbent of anchovy dried by different
methods are considerably difference. Fish dried by the selective
IR had proportion of re-absorbent highest (70.4%), followed by
fish sun dried (61.7%) and fish heat dried only 54.3%.
3) Proportion of product broken
Proportions of fish broken in different dry methods were
analysed for comparision purpose. Fish products dried by the
18
selective IR had lowest broken proportion (1.8%), followed by fish
heat dried (4.07%) and fish sun dried (5.42%).
3.5.3. Sensory quality
Sensory quality of anchovy dried by the selective IR is
highest (19.24 scores), followed by fish sun dried (17.08
scrores) and lowest is fish dried by heater (only 16.2 scores).
(a)
(b)
(c)
(d)
Figure 3.24. Pictures of anchovy after boiling/ steaming (a),
dried fish by SD (b), dried by HA (c), dried by IR (d)
3.5.4. Quantity and type of micro-organisms
Variations in mirco-organisms of anchovy dried by different
methods is presented in table 3.38.
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