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SINGAPORE JOURNAL OF PRIMARY INDUSTRIES
PUBLISHED BY THE AGRI-FOOD AND VETERINARY AUTHORITY OF SINGAPORE
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Vol. 31
ISSN 0129-6485
2003/04
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CONTENTS
Page
Analysis of polychlorinated biphenyls in fish by accelerated solvent extraction
Neo L P, Chew C F, Ch’ng A L, Chew S T and Chua S B ………………………………………………
1
A comparison of the headspace and iso-octane methods for the analysis of dithiocarbamates in fruits
and vegetables
Loh C K, Chua J, Chua G C, Luk S C, Chew S T and Chua S B ………………………………………..
9
Dietary influence on the growth performance of the early and fingerling stages of the flower
horn fish (Cichlasoma sp.)
Lim L Y, Ling K H, Wong C C and Tan E L ……………………………………………………………
15
Guppy breeding: A comparison between different set-ups for guppy fry collection
Tan E L, Ling K H, Wong C C and Lim L Y …………………………………………………………..
21
Plug transplants for leafy vegetable production
Poh B L, Leong W H, Yap-Koh T K and Ong PH ………………………………………………………
27
Fatty acid composition of traditional seafood products.
Teo P H and Low L K ………………………………………………………………………………….
35
Use of GMO analytical methods for regulatory functions at Veterinary Public Health Laboratory
Koh M C, Chong P S, Lim C H, Chew S T and Chua S B ………………………………………………
45
Characteristics of Escherichia Coli serotype O157:H7 isolates from cattle and goat farms in Singapore
Toh S L, Goh Y H, Lee W Y, Teo T P, Tay Y H, Lee S K, Tong C W and Loh H …………………….
53
Changes in biochemical constituents of ‘Golden Gate’ cut rose petals as affected by pre-cooling,
pulsing and packaging
Mwangi M, Chatterjee S R and Bhattacharjee S K …………………………………………………………
65
SHORT COMMUNICATIONS
Developments in large scale fish fry production and the Marine Aquaculture Centre Hatchery
on St John’s Island
Chow M, Wang K L and Lim H S …………………………………………………………………….
73
Bacteriological safety of ready-to-eat raw fish (yu sheng)
June CH, Wong K O and Seah H L …………………………………………………………………...
77.
ANALYSIS OF POLYCHLORINATED
BIPHENYLS IN FISH BY ACCELERATED
SOLVENT EXTRACTION
Neo LP*, Chew CF*, Ch'ng AL*, Chew ST* and Chua SB*
ABSTRACT
The use of accelerated solvent extraction technique for extraction of polychlorinated
biphenyls (PCBs) in fish was investigated. A comparison of the effectiveness of
Hydromatrix® and sodium sulphate as the drying agents and the efficacy of different types of
clean-up sorbents (namely, silica, alumina neutral, alumina acid, alumina basic) for removal
of fat from the sample during the extraction process were carried out. The results obtained
showed that using a combination of Hydromatrix® and silica with this technique gave the best
recoveries of PCBs.
A COMPARISON OF THE HEADSPACE AND
ISO-OCTANE METHODS FOR THE ANALYSIS
OF DITHIOCARBAMATES IN FRUITS AND
VEGETABLES
Loh C K*, Chua J*, Luk S C*, Chua G C*, Chew S T* and Chua S B*
ABSTRACT
Headspace gas analysis by gas chromatograph-flame photometric detector(GC-FPD)
has traditionally been used in the determination of dithiocarbamate fungicides as total
carbon disulphide (CS2) in vegetable crops and many other commodities. The isooctane method is an alternative method to ascertain fungicide residue levels. Both
methods were used for the determination of dithiocarbamates (maneb, zineb, mezineb,
mancozeb, ferbam, manam, sodium dimethyl dithiocarbamate and ziram) in
vegetables and fruits. Tin (II) chloride in aqueous hydrochloric acid was used in these
two methods to reduce the fungicides to CS2 before detection by flame photometry.
The only difference between these methods is the manual injection of the headspace
gas compared to autoinjection of an extract by iso-octane. This study showed that the
iso-octane method is as accurate as the headspace method but was better in terms of
run time and labour savings.
1
DIETARY INFLUENCE ON THE GROWTH
PERFORMANCE OF THE EARLY AND
FINGERLING STAGES OF THE FLOWER HORN
FISH (CICHLASOMA SP.)
Lim L Y*, Ling K H*, Wong C C* and Tan E L*
ABSTRACT
In the Early stage, (Week 0 to 5) Artemia nauplii were found to be best when given in
the
larval
phase
of
the
Flower
Horn
fish.
Larvae
of
0.78
+
0.03 cm and wet weight of 0.0042 g attained a mean total length of 3.04 + 0.08 cm
and wet weight of 0.44 + 0.02 g which are 58.33 % and 308.41 % better than those
fed Moina (Moina category) acting as the control. Those fed pellets (Pellet category)
had intermediate performance achieving 2.35 + 0.02 cm (22.40 % better) in mean
total length and 0.21 + 0.03 g (93.46 % better) in mean wet weight respectively
compared to those fed Moina. Among the three categories, Moina category (the
Control) had the worst performance. In the Fingerling stage of the Flower Horn fish,
(Weeks 6 - 13) Artemia nauplii and Moina were replaced by Oxheart and Tubifex
Worms respectively since the former two have been shown to be nutritionally
inadequate at this stage. The main reason is because young fish larvae require higher
fat intake for normal body needs and growth whereas fingerlings needs more protein
for growth and synthesizing of new body tissues and enzymes. As such, Oxheart and
Tubifex Worms, which are richer in protein content, are preferred over Artemia
nauplii and Moina. Oxheart was found to be the best diet for Flower Horn fingerlings
with optimal growth of 5.47 + 0.06 cm (20.48 % better) and 2.72 + 0.05 g (92.17 %
better) in mean total length and wet weight compared to those fed Tubifex Worms
category which was the control. Those in the Pellet category had intermediate
performance achieving 4.58 + 0.15 cm and 1.45 + 0.10 g in mean total length and wet
weight, which were 19.60 % and 2.54 % respectively, better than the control. In the
Fingerling stage, those in the Tubifex Worms category (the Control) had the worst
performance, only achieving 4.54 + 0.08 cm and 1.42+ 0.08 cm and 1.42 + 0.08 cm in
mean total length and wet weight respectively.
GUPPY BREEDING: A COMPARISON BETWEEN
DIFFERENT SET-UPS FOR GUPPY FRY
COLLECTION
Tan E L*, Ling K H*, Wong C C*, Lim L Y*
ABSTRACT
This paper describes a new set-up (Set-up 1) for Guppy breeding. In order to test its
efficiency in Guppy fry collection, the new set-up is compared with two other
conventional set-ups used currently used by local Guppy farmers. On average, 2,450
fry were harvested from Set-up 1, which was 1.6 times higher than Set-up 2 (940 fry)
and 2.05 times higher than Set-up 3 (803 fry) respectively. The results show that Setup 1 is the best set-up for Guppy fry collection, and the new set-up will be
recommended to local Guppy farmers.
1
PLUG TRANSPLANTS FOR LEAFY
VEGETABLE PRODUCTION
BL Poh*, Leong WH *, Yap-Koh TK * and Ong PH *
ABSTRACT
The experiments on plug transplanting carried out by Horticulture Branch, Agri-Food
and Veterinary Authority (AVA) as well as the status and effectiveness of this
transplanting system for the local vegetable industry are reviewed. Use of plug
transplanting for soil vegetable cultivation was introduced to local vegetable farmers
in year 2000. Theoretically, more crops could be produced per year since the
transplanted seedlings were grown in the nurseries for more crop cycles in the field.
Transplants in the nurseries occupied only a small area, allowing easier management
of irrigation, fertilising and pest and disease control. Brewery waste compost, MG
mix and SS peat moss with about 1% N were suitable growing media for caixin
seedlings. Brewery waste compost, in particular, could support growth of the
seedlings till 20 days old. Seedlings should be transplanted at 12-16 days and
harvested at 34-38 days after seed sowing to get good marketable yields. Plug
transplanting is gaining popularity despite production costs increasing from higher
investment in media, plug trays and additional labour.
FATTY ACID COMPOSITION OF TRADITIONAL
SEAFOOD PRODUCTS
Teo P H* and Low L K*
ABSTRACT
Total lipid and fatty acid composition of eleven traditional seafood products were studied.
They included two types of dried fish (salted threadfin and boiled-dried anchovies), five types
of dried shellfish (oysters, mussels, prawns, scallops and cuttlefish), three types of fermented
fish products (fish sauce, belachan or prawn paste and cinchalok or fermented shrimps) and
one type of fish jelly product (boiled fishballs). Fish sauce had very low lipid content of
0.02% and thus it was not feasible to analyse for fatty acid composition.
Both dried oysters and mussels gave the highest lipid content of 10.52% and 9.82%
respectively. These were followed by boiled-dried anchovies (5.23%), dried cuttlefish
(5.01%), dried prawns (2.93%), dried scallops (1.94%), dried threadfin (1.31%), cinchalok
(1.22%), belachan (3.13%) and boiled fishballs(0.38%).
Omega-3 fatty acids were present in all samples analysed, and were highly abundant in dried
oysters (2837 mg/100g), dried cuttlefish (1782 mg/100g), dried mussels (1459 mg/100g) and
boiled-dried anchovies (1408 mg/100g). The boiled fishballs had the lowest amount of
omega-3 fatty acid content of 94 mg/100g). The ratio of the omega-3 to omega-6 fatty acid
was good in all products and ranged between 2 in dried threadfin to 7 in boiled-dried
anchovies.
1
USE OF GMO ANALYTICAL METHODS
FOR REGULATORY FUNCTIONS
AT VETERINARY PUBLIC HEALTH
LABORATORY
Koh M C, Chong P S, Lim P C, Lim C H, Chew S T and Chua S B
ABSTRACT
In this paper, two techniques are discussed that are used by the Veterinary Public
Health Laboratory (VPHL) for detection of transgenic DNA and protein in food of
both maize and soya origin. This work, which consists of a series of surveillance
testing, is initiated as part of the preparatory program for establishing Genetically
Modified Organisms (GMO) testing capability in VPHL for regulatory purposes.
Polymerase Chain Reaction (PCR), a DNA based method and Enzyme Linked
Immunosorbant Assay (ELISA) that detects proteinaceous analytes are the two
techniques employed. For assessment, the two methods are concurrently applied for
testing on all samples which primarily consisted of products available in local retail
markets. In addition, rapid screening protocols utilizing commercial test kits are
adopted, as these are ideally suited for handling the large volume of samples typically
encountered in regulatory testing. Using PCR reagent-primer tablets, transgenic DNA
was successfully detected in both raw grains as well as processed products. Although
ELISA-based techniques allow quantification of GM proteins down to 0.1% GMO/
non-GMO (w/w), this is only possible with materials in the form of raw primary
produces.
CHARACTERISTICS OF ESCHERICHIA COLI
SEROTYPE O157:H7 ISOLATES FROM CATTLE
AND GOAT FARMS IN SINGAPORE
Toh S L*, Goh Y H*, Lee W Y*, Teo T P*, Tay Y H*, Lee S K*,
Tong C W* and Loh H**
ABSRACT
Cattle and goat farms in Singapore are routinely surveyed for Escherichia coli
serotype O157:H7 through sampling of faecal swabs and milk for cultural
examination. From 1996 to 2002, 25 isolates of E. coli O157:H7 were cultured from
faecal swabs of animals in 2 cattle farms and 1 goat farm, with the last detection
occurring in February 2000. All isolates were found to be positive for the verotoxin 2,
intimin and enterohaemolysin genes by multiplex polymerase chain reaction, although
most of the isolates were tested negative for verotoxin production using a reversed
passive latex agglutination kit. With the use of phage typing and antibiogram typing,
the 25 E. coli O157:H7 isolates were classified as 2 different strains: phage type 14
(sensitive to all antibiotics tested) and phage type 38 (resistant to Sulfathiazole and
Streptomycin). This is the first report of E. coli O157:H7 detection from livestock in
Singapore. As a precautionary measure, all E. coli O157:H7 culture-positive animals
were either isolated or removed from the affected farms. Testing of the other animals
from the same farms yielded negative results thereafter. In the same period between
1996 and 2000 when E. coli O157:H7 was isolated from our local cattle and goat
farms, there were no reports of E. coli O157:H7 in humans in Singapore except for an
imported case of gastroenteritis caused by the pathogen.
1
‘GOLDEN GATE’ CUT ROSE PETALS AS
AFFECTED BY PRE-COOLING, PULSING AND
PACKAGING.
.
Mwangi M∗, Chatterjee S.R. **, Bhattacharjee S. K. ***
ABSTRACT
Four different packaging materials namely butter paper, brown paper, polythene sheet
(80gauge) and single layer corrugated fibre board sheet were used with two different
storage durations of 6 hours and 20 hours each in order to find out the effects of
precooling, pulsing and packaging on the postharvest life and biochemical
constituents of ‘Golden Gate’ rose petal tissues. Flowers precooled with cool storage
at 40C for 24 hours and pulsing with dimethyl sulphoxide (DMSO) at 2% for 15 min.
and packed with butter paper packaging material for six hours recorded maximum
increase in the content of total starch, total soluble sugars (TSS), total phenols and
minimum increase in the content of total free amino acids (TFAA) in the petal tissues
on the third day in vase as well as at the senescence stage. It also resulted in longer
vase life than the control treatment.