Proceeding of 2013 International Seminar on Climate Change and Food Security ISCCFS 2013
Palembang, South Sumatra -Indonesia, 24-25 October,2013
163
Minimal Cooking Time Determination of Pepes Nile Tilapia Processed By Microwave Oven
Riya Liuhartana
1+
, Gatot Priyanto
2
and Basuni Hamzah
2
1
The Fishery Faculty, University of PGRI Palembang
2
Department of Agricultural Technology, Faculty of Agriculture, University of Sriwijaya
Abstract.
The objective of this research was to determine the minimal cooking time of pepes nile tilapia Oreochromis niloticus processed by microwave oven. The treatment was the cooking time of raw pepes
using microwave oven which consists of three levels 3, 4 and 6 minutes with three replications. The observed parameter was the well done state of pepes which was determined by microbial total plate count
TPC, internal temperature and visual observation of pepes. The result of experiment show that all of the sample total plate count at three cooking time treatment levels were less than the maximum limit of microbial
total plate count regulated by SNI. The internal temperatures of pepes at three treatment levels were above the minimum limit regulated by FSIS-USDA. Visual observations indicated that pepes has been cooked
during 4 minutes was rare state while pepes processed for 5 and 6 minutes were well done state. It was concluded that minimal cooking time of pepes by microwave oven was five minutes.
Keywords:
Nile tilapia, microwave oven, pepes.
1. Background
Nile tilapia
Oreochromis niloticus
is a cultivable fish that its availability is not affected by the season. Nile tilapia can be processed into various products and dishes such as fish
pepes
, which is an traditional fish product from Indonesia. Fish
pepes
is prepared by steaming it for 30 minutes
[1]
. However, steaming could reduce the nutritional content of fish
[2][3][4]
. Beside steaming, microwave technology could be used to cook fish.
The term ‗microwaves‘ is used for wavelengths between 1 m and 0.1 cm or for bands of frequencies between 300 MHz and 300 GHz
[5]
. There are plenty of related research studying about the effects of microwave cooking on the nutrient content of fish
[6][7][8]
. The research investigated the effects of microwave processing on
pepes
product. Cooking
pepes
with microwave oven was expected to reduce heating time and consequently minimize the nutritional content loss.
The objective of this research was to determine the minimal cooking time of
pepes
nile tilapia
Oreochromis niloticus
by using microwave oven. Preliminary research indicated that nile tilapia fish can be cooked with
microwave oven for five minutes.
2. Literature Review
2.1. Nile Tilapia
Pepes
Nile tilapia
Oreochromis niloticus
is a nutritious animal food. Nutrient composition of fresh nile tilapia per 100 g edible portion is 77.81 of moisture, 1.04 of ash, 3.73 of fat and 19.04 of protein
content, respectively
[9]
. Mineral content of dried nile tilapia in 7.5 of moisture content is 0.23 of phosphorus , 0.20 of calcium , 0.32 of potassium , 0.23 of magnesium , 0.12 of iron and 0.80
of sodium, respectively
[10]
. Nile tilapia can be processed into various products such as nile tilapia fillet, baby nile tilapia chips, shredded nile tilapia, smoked nile tilapia, sweet and sour nile tilapia, nile tilapia with bali
seasoning
[11]
and
pepes
nile tilapia
[1]
.
Pepes
is an Indonesian traditional fish product made of fish and spices, wrapped with banana leaves and then cooked by steaming for 30 minutes. Fishes from seawater or freshwater could be used as raw materials
for
pepes
[1]
. Main spices which commonly used are shallot, garlic, red chilli, candlenut, ginger, turmeric,
+
Corresponding author. Tel.: +6282373631974
E-mail address
: riya.liuhartanarocketmail.com
Proceeding of 2013 International Seminar on Climate Change and Food Security ISCCFS 2013
Palembang, South Sumatra -Indonesia, 24-25 October,2013
164 lemon grass and salt, and alternatively
tempoyak
to produce
pepes tempoyak
.
Tempoyak
is a fermented durian product
[12]
.
2.2. Food Cooking by Microwave Oven
The heating of foods by microwave energy is accomplished both by the absortion of microwave energy by dipolar water molecules and ionic components of the food. Thus, both the water content and the
dissolved ion content often salt are dominating factors in the microwave heating of foods. When the dipolar water molecule is subjected to a microwave field, with the field rapidly changing its direction, the dipole
tries to align itself with the field direction. There is a time lag, as some response time is required for the water molecule to overcome the inertia and the intermolecular forces in the water. The electric field thus
provides energy for the water molecule to rotate into alignment. The energy is then lost to the random thermal motion of the water and results in a temperature rise. When ionized compounds are subjected to a
microwave field, they randomly collide with nonionized groups in an electric field. The kinetic energy of these ions is transmitted into heat during the collisions
[13]
. Temperature distribution in cooking using microwaves may not be uniform. Consequently, food could
not be cooked uniformly
[14]
. The measurement of food temperature at several parts was important in order to confirm that the food temperature has reached recommended temperature sufficient to kill pathogenic
microbes. In other words, cooked fish should reach 145 °F
[15]
. Measurements of fish temperature can be carried out in several parts based on consideration of the difference in thickness. When the shape of food is
irregular, the thinner and the narrower parts tend to be hot more rapidly in microwave cooking
[16]
.
3. Materials and Method
3.1. Experiments and materials preparation
Fresh nile tilapia
Oreochromis niloticus
250g ± 20 in weight, tamarind, shallot, garlic, red chilli, salt, sugar, ginger, candlenut, turmeric, galangal, lemon grass and banana leaves were purchased from local
traditional market in Palembang, South Sumatera. The materials were brought to WSTPHP Workshop Teknologi Pengolahan Hasil Perikanan of The Fishery Faculty of University of PGRI Palembang in
Palembang South Sumatra. Fresh fish were eviscerated, descaled and then washed with tap water. Raw
pepes
was prepared according to a modified method of Diana et al. 2010
[1]
with a slight modification, namely unit conversion of material from piece to weight weighted, and the use of tamarind juice and refined sugar
to improve flavor of
pepes
. The following equipments were used in this research, including commercial microwave oven Sharp model R-2491NW, 2450 MHz, 800 W, pot steamer, thermometer insertion
digital thermometer Krisbow KW06-308, temperature range -40°C to 250°C and other equipments for microbial analysis. The research was conducted from January 2013 to March 2013.
One factor was investigated in this research, namely cooking time of
pepes
with microwave oven and consisted of three following levels: 4 A
1
, 5 A
2
and 6 minutes A
3
with three replications. In addition,
pepes
was heated in microwave oven for additional 3 minutes before removed. The observed parameters were total plate count TPC, internal temperature and visual observation. TPC analysis was conducted at
LPPMHP Laboratorium Pembinaan dan Pengujian Mutu Hasil Perikanan Palembang in Palembang South Sumatra, whereas internal temperature measurement and visual observation were conducted at WSTPHP
Workshop Teknologi Pengolahan Hasil Perikanan of The Fishery Faculty of University of PGRI Palembang in South Sumatra.
3.2. Samples Analysis 3.2.1. Microbial content TPC
The microbial load of
pepes
was determined with total plate count TPC SNI 01-2332.3-2006
[17]
. The maximum limit of microbial content should not exceed 5x10
5
CFUg SNI 7388:2009
[18]
. TPC analysis principle was the growth of microorganisms after incubating on agar media at 35 °C for 48 hours. The
growing microorganisms will form colonies that could be directly calculated and expressed in log CFUg.
Proceeding of 2013 International Seminar on Climate Change and Food Security ISCCFS 2013
Palembang, South Sumatra -Indonesia, 24-25 October,2013
165
3.2.2. Internal temperature
Pepes
internal temperature was measured using a thermometer insertion at four points, namely in abdomen belly, near the head anterior, in the middle of the body middle and near the tail. Average
internal temperature were expressed in Celcius degrees °C. A safe minimum internal temperature for fish is 145°F or 63 °C
[15]
.
3.2.3. Visual observation
Visual observation of well done state of
pepes
was conducted by using Suwandi 1990 method
[2]
with a slight modification, namely additional characteristics of fish, including fat color and texture of spices.
4. Result and Discussion
4.1. Microbial content TPC
In general, microbial content of
pepes
measured as total plate count TPC showed that the populations were under standard maximum limits, namely 5x10
5
CFUg or 5.70 log CFUg. Increasing cooking time led to a decrease in the number of microbial colonies. The average value of TPC was 4.89 log CFUg for A
1
treatment: cooking for 4 minutes, 4.77 log CFUg for A
2
treatment: cooking for 5 minutes and 4.75 log CFUg for A
3
treatment: cooking for 6 minutes Figure 1.
Fig. 1: The average values of total plate count TPC of
pepes
heated with microwave oven
The results were in accordance with those of Hollywood, Varabioff and Mitchell 1991
[19]
who studied the effect of microwave cooking and conventional oven on temperature profiles and microbial flora of beef.
Mesophilic microbial colony counts contained in beef studies showed a decrease with increasing time after the cooking and standing. The conclusion of that study was food cooking by microwave need adequate
procedure and standing time after the food was cooked in order to achieve the balance of temperature and exposure to microbes. The destruction of microorganisms during microwave heating was mainly caused by
the heat generated by microwaves
[20]
. Heat caused denaturation of proteins that destroy the activity of the enzyme which controls the metabolism of microorganisms
[21]
. TPC data of
pepes
were then used to determine D value with reference to Winarno 1994
[22]
. Linear equation obtained from the relationships of heating time of microwave oven and the number of survived
microbes in
pepes
was shown on Figure 2. D value was then calculated from the resulting equation of y = - 0.070 x + 5.156 and gave 14.28 minutes. The following conditions of microwave oven were applied: power
800 W and frequency 2450 MHz. In other words, killing of 90 of the microbial population in
pepes
could be accomplished in 14.28 minutes. Jeng
et al.
1987 showed that the sporicidal mechanism of microwave
was caused by thermal effects
[23]
. That study showed that D value on sterilization of dried spores of
Bacillus subtilis
subsp.
niger
are 88, 14 and 7 minutes at 117, 130 and 137 °C, respectively.
Proceeding of 2013 International Seminar on Climate Change and Food Security ISCCFS 2013
Palembang, South Sumatra -Indonesia, 24-25 October,2013
166 Fig. 2: Effects of microwave oven heating time on the number of microbes in
pepes
4.2. Internal temperature
The measurements of
pepes
internal temperature showed that all treatments exceeded the minimum standard of internal temperature of 63 °C. The average internal temperature
pepes
are 73.8 °C of A
1
treatment cooking for 4 minutes, 76.1 °C of A
2
cooking for 5 minutes and 81.7 ° C of A
3
cooking for 6 minutes Figure 3. Increasing cooking time caused increase in
pepes
internal temperature. Similar result has been reported for cooked meat by microwave oven
[19]
.
Fig. 3: Internal temperature of
pepes
processed by microwave oven Cooking could increase
pepes
internal temperature due to heat transfer from heat source. There are three modes of heat transfer, which contribute to the overall heat transfer process in differing proportions namely
conduction, convection and radiation. Conduction is the transfer of heat by molecular motion in solid bodies. Convection is the transfer of heat by fluid flow, created by density differences and buoyancy effects, in fluid
products. Radiation is the transfer of electromagnetic energy between two bodies at different temperatures
[24]
.
4.3. Visual Observation
Visually,
pepes
from A
1
treatment cooking time of 4 minutes produced rare state of
pepes
. This was shown by clear, reddish flesh, a transparent fat in the abdominal area and in the abdominal cavity, moist and
chewy texture of flesh, flesh was attached to bone and moist texture of spices. Both A
2
cooking for 5 minutes and A
3
treatments cooking for 6 minutes produced a well done state of
pepes
and shown by typical brownish white-coloured flesh, white fat in the abdominal area and in the abdominal cavity, moist
and tender texture of flesh and spices, and flesh was easily removed from bone. Fish heating converts the translucent, jelly-like cellular mass into an opaque, friable, slightly firm and
springy form. Synaeresis or shrinkage occurs and fluid is release, the proteins in which may coagulate to
Proceeding of 2013 International Seminar on Climate Change and Food Security ISCCFS 2013
Palembang, South Sumatra -Indonesia, 24-25 October,2013
167 form curd separately from the main solid mass. As noted above, the connective tissue holding the cells
together is easily degraded and blocks of cells or the cells themselves become readily separated from one another. Thus, unlikely many meats, cooked fish easily falls apart and becomes palatable on mild heating
[25]
.
5. Conclusion
It was concluded that minimal cooking time of
pepes
by microwave oven was five minutes. The resulting
pepes
meets microbiology criteria shown with TPC, internal temperature and physical characteristics in term of visual observation.
6. References
[1]
Diana, H. Muaris, G. Hendro dan I. Hardiman. 2010. Yuk Makan Ikan, Sedapnya Pepes Ikan. Gramedia Pustaka Utama, Jakarta, Indonesia. 55 hal.
[2]
Suwandi, R. 1990. Pengaruh Proses Penggorengan dan Pengukusan terhadap Sifat Fisiko - Kimia Protein Ikan Mas Cyprinus carpio L.. Tesis Fakultas Pascasarjana Institut Pertanian Bogor tidak dipublikasikan. 108 hal.
[3]
Al-Saghir, S, K. Thurner, K. Wagner, G. Frisch,W. Luf, E. Razzazi-Fadeli and I. Elmadfa. 2004. Effects of Different Cooking Procedures on Lipid Quality and Cholesterol Oxidation of Farmed Salmon Fish Salmo salar. J.
Agric. Food Chem. 52, 5290-5296.
[4]
Aisyah, E.N. 2012. Perubahan Kandungan Mineral dan Vitamin A Ikan Cobia Rachycentron canadum Akibat Proses Pengukusan. Skripsi Departemen Teknologi Hasil Perairan Fakultas Perikanan dan Ilmu Kelautan Institut
Pertanian Bogor tidak dipublikasikan. 47 hal.
[5]
Saxena, V.K. and U. Chandra. 2011. Microwave Synthesis : A Physical Concept. In U. Chandra editor. Microwave Heating page 3-22. InTech, Rijeka, Croatia. 370 p.
[6]
Kolakowska, A and G. Bienkiewicz, 1999. Stability of fish lipids during microwave heating. Acta Ichthyologica Et Piscatoria Vol. XXIX, Fasc. L. : 101-110.
[7]
Ashgari, L, F. Zeylani and M.A. Sahari. 2013. Effects of boiling, deep-frying, and microwave treatment on the proximate composition of rainbow trout fillets: changes in fatty acids, total protein, and minerals. J. Appl. Ichthyol.
1 –7.
[8]
Oz, F, G. Kaban and M. Kaya. 2010. Effect of Cooking Techniques and Levels on the Formation of Heterocyclic Aromatic Amines in Chicken and Fish. J. Anim. Vet. Adv. 9 8: 1259-1264.
[9]
Foh, M.B.K, M.T. Kamara, I. Amadou, B.M. Foh and X. Wenshui. 2011. Chemical and Physicochemical Properties of Tilapia Oreochromis niloticus Fish Protein Hydrolisate and Concentrate. Int. J. Biol. Chem 51: 21-
36.
[10]
Fawole, O.O., M.A. Ogundiran, T.A. Ayandiran and O.F. Olagunju. 2007. Proximate and Mineral Composition in Some Selected Fresh Water Fishes in Nigeria. Internet J. Food Saf. Vol.9., p. 52-55.
[11]
Permadi, A dan N. Dharmayanti. 2011. Modul Penyuluh Perikanan : Pengolahan Ikan Nila Oreochromis niloticus
. Pusat Penyuluhan Perikanan, Badan Pengembangan SDM Kelautan dan Perikanan, Kementrian Kelautan dan Perikanan, Jakarta, Indonesia. 47 hal.
[12]
Yulia T dan A. Utomo. 2008. 668 Resep Masakan Khas Nusantara dari 33 Provinsi. AgroMedia Pustaka, Jakarta, Indonesia. 420 hal.
[13]
Li, H and H. Ramaswamy. 2008. Microwave Drying. In Hui Y.H, C.Clary, M.M. Farid, O.O.Fasina, A. Noomhorm and J. Welti-Chanes editor. Food Drying Science and Technology page 127-148. DESTech Publications,
Pennsylvania, USA. 781 p.
[14]
Vadivambal, R. and D.S. Jayas, 2010. Non-uniform Temperature Distribution During Microwave Heating of Food Materials-A Review. Food Bioprocess.Technol. 3:161-171.
[15]
FSIS-USDA Food Safety and Inspection Service United States Departement of Agriculture, 2011. Food Safety Information : Microwave Ovens and Food Safety. 6 p.
[16]
George, R.M. and S-A. Burnett. 1991. General guidelines for microwavable products. Food Control-January : 35- 43.
[17]
BSN Badan Standardisasi Nasional. 2006. Cara uji mikrobiologi-Bagian 3: Penentuan angka lempeng total ALT pada produk perikanan SNI 01-2332.3-2006. Badan Standardisasi Nasional, Jakarta. 11 hal.
[18]
BSN Badan Standardisasi Nasional. 2009. Batas maksimum cemaran mikroba dalam pangan SNI 7388:2009. Badan Standardisasi Nasional, Jakarta. 37 hal.
[19]
Hollywood, N.W, Y. Varabioff and G.E. Mitchell. 1991. The effect of microwave and conventional cooking on the temperature profiles and microbial flora of minced beef. Int. J. Food Microbiol., 14 : 67-76.
[20]
Anantheswaran, R.C and H.S. Ramaswamy. 2001. Bacterial Destruction and Enzyme Inactivation During Microwave Heating. In A.K. Datta and R.C. Anantheswaran editor. Handbook of Microwave Technology for
Food Applications page 191-213. Marcel Dekker, New York, USA. 511 p.
Proceeding of 2013 International Seminar on Climate Change and Food Security ISCCFS 2013
Palembang, South Sumatra -Indonesia, 24-25 October,2013
168
[21]
Fellows, P. 2000. Food Processing Technology, Principles and Practice. Woodhead Publishing Limited, Cambridge, England. 575 p.
[22]
Winarno, F.G. 1994. Sterilisasi Komersial Produk Pangan. Gramedia Pustaka Utama, Jakarta, Indonesia. 180 hal.
[23]
Jeng, D.K.H, K.A. Kaczmarek, A.G. Woodworth and G. Balasky. 1987. Mechanism of Microwave Sterilization in the Dry State. Appl. Environ. Microbiol., Vol. 53, No. 9, p. 2133-2137.
[24]
Holdsworth, D. And R. Simpson. 2007. Thermal Processing of Packaged Foods. Springer Science+Business Media, New York, USA. 407 p.
[25]
Aitken, A and J.J. Connell. 1979. Fish. In R.J. Priestley editor. Effects of Heating on Foodstuffs page 219-254. Applied Science, London, England. 427 p.
Proceeding of 2013 International Seminar on Climate Change and Food Security ISCCFS 2013
Palembang, South Sumatra -Indonesia, 24-25 October,2013
169
Toxicity Characteristics of Bacillus Thuringiensis Strain MSP-02 Agricultural Insect Pests
Yulia Pujiastuti
1+
, A. Muslim
1
, Hisanori Bando
2
, and Shin-Ichiro Asano
2
1
Dept. of Plant Pests and Diseases, Faculty of Agriculture, Sriwijaya University, Indonesia
2
Lab. of Applied Molecular Entomology, Faculty of Agriculture, Hokkaido University, Japan
Abstract.
Insects play important roles in reduction of crop production. They need to be control. One technique to control them is the used of entomopathogenic bacteria.Bacillus thuringiensis is a gram-positive
bacterium, rod-shaped, aerobic and spore-forming.The protein crystals will be produced by B. thuringiensis during sporulation.This protein is toxic to insect pests. The objectives of research were to investigate the
characters of B. thuringiensis isolated from swamp land in South Sumatera including their toxicity against armyworm Spodoptera litura Lepidoptera:Noctuidae. The result of preliminary bioassay showed that one
isolate was very toxic to larvae of S. litura. It was named MSP-02 strain. This strain was further investigated of its protein and cell formation by Scanning Electrone Microscope SEM, its molecular weight of protein
and bioactivity towards Popilliae japonica larvae and S. litura larvae. After collecting crystal protein by LB mass production, bioassay test against insect pests was conducted. The result showed that strain MSP-02 was
very toxic to armyworm S.litura 100. However when conducting bioassay to P. japonica, its toxicity was not higher as those in armyworm67.7. Crystal protein was measured its molecular weight by SDS-PAGE
electrophoresis. It was assumed that the molecular weight of protein was about 135 kDa indicated that this strain belonged to Cry1 protein group. This strain was then chosen as a candidate to produce mass production
of bioinsectide.
Keywords:
Bacillus thuringiensis, Spodoptera litura, toxicity
1. Introduction
