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Microbiological quality of 18 jC ready-to-eat food

products sold in Taiwan

Tony J. Fang a,*, Que-King Wei b, Chia-Wei Liao a, Min-Ju Hung a, Tzu-Hui Wang a

aDepartment of Food Science, National Chung Hsing University, 250 Kuokuang Road, Taichung 40227, Taiwan, ROCbChung Hwa Institute of Technology, Tainan, Taiwan, ROC

Received 18 October 2001; received in revised form 11 January 2002; accepted 15 April 2002

Abstract

A total of 164 samples of 18 jC ready-to-eat (RTE) food products, purchased in 19992000 from convenience stores and

supermarkets in central Taiwan, were examined to determine the microbiological quality of these products. The 18 jC RTE food

products, manufactured by 16 factories, were divided into groups based on the type of food and their major ingredients. Aerobic

plate count, coliforms, Escherichia coli, Bacillus cereus, Staphylococcus aureus and psychrotrophic Pseudomonas spp. were

evaluated. The incidence of E. coli and coliforms in these 18 jC RTE food products was 7.9% and 75.0%, respectively, while

49.8% and 17.9% of the samples were found to contain B. cereus and S. aureus, respectively. Among the samples tested, 1.3%

of the food products contained more than 105 CFU g1 ofB. cereus and 0.7% contained more than 105 CFU g1 ofS. aureus.

The pH values of the samples were all below 7.0, except for cold noodles, which had pH values ranging from 5.18 to 8.20.Among the five types of 18 jC food products tested, the highest incidence of E. coli (16%) and Pseudomonas spp. (64.0%)

were detected in hand-rolled sushi in a cone shape. On the other hand, the highest incidence rate of coliforms, B. cereus, and S.

aureus were found in sandwiches (88%), cold noodles (66.7%) and rice balls rolled in seaweed (25.0%), respectively. Food

products made of ham contained the highest incidence of coliforms (88.0%) and E. coli (16.0%), while food products

containing meat and ham as the major ingredients had the highest incidence rates of B. cereus (62.5%) and S. aureus (26.1%),

respectively. For coliforms, E. coli, B. cereus and S. aureus, the percentage of 18 jC RTE food products exceeding the

microbiological standards for RTE food accepted by Republic of China was 75.0%, 7.9%, 49.8% and 17.9%, respectively.

D 2002 Elsevier Science B.V. All rights reserved.

Keywords: 18 jC foods; Microbiological quality; Ready-to-eat (RTE)

1. Introduction

In Taiwan, Republic of China, there has been a

marked increase in the sales of so-called 18 jC

ready-to-eat (RTE) food products in recent years.

The concept of 18 jC RTE food products was

originally developed in Japan and adopted by the

food industry in Taiwan. In the production of such

food products, emphasis is placed on controlling the

processing conditions. For example, in the case of 18

jC box meals, the critical control points include

controlling cooking time and temperature. In addition,

after the box meals are packaged, they are vacuum

0168-1605/02/$ - see front matterD 2002 Elsevier Science B.V. All rights reserved.P I I : S 0 1 6 8 - 1 6 0 5 ( 0 2 ) 0 0 1 7 2 - 1

* Corresponding author. Tel.: +886-4-2286-1505; fax: +886-4-

2287-6211.

E-mail addresses: [email protected],

[email protected] (T.J. Fang).

www.elsevier.com/locate/ijfoodmicro

International Journal of Food Microbiology 80 (2003) 241 250

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cooled to 18F2 jC within 5 min. By this rapid

cooling method, the growth of contaminating micro-

organisms is retarded. In general, the shelf life of 18

jC RTE food products is about 20 h when they are

placed in stores and actually kept at 18 jC. Rice balls

rolled in seaweed, sandwiches, sushi and cold noodles

are the most common 18 jC RTE food products sold

in convenience stores in Taiwan (Fang, 2000).

Although the 18 jC RTE food products have become

more popular in recent years, the microbial quality of

these products needs to be taken into consideration

since they are processed and held before consumption

at 18 jC, which is a temperature in which most

microorganisms grow well.

The RTE food products provide a source of readily

available and nutritious meals for the consumer.

However, questions have been raised about the safety

and microbiological quality of these food products.

Mosupye and Von Holy (1999) investigated the

microbiological quality of RTE street-vended food

products in Johannesburg, South Africa. In that study,

51 samples were taken for determination of the micro-

biological quality; Bacillus cereus was detected in

22%, Clostridium perfringens in 16%, Salmonella

spp. in 2% and Escherichia coli (non-O157:H+) in

2% of the 51 food samples. Chiou et al. (1996)

examined the microbial quality of 300 RTE food products sold in southern Taiwan, which were kept

hot. Their results indicated that the percentage of food

products not meeting the microbiological standards

accepted by the Republic of China regarding aerobic

plate count, coliform and E. coli were 17.7%, 20.3%

and 8.0%, respectively.

Since outbreaks of illness in human beings are

understood to be caused by consumption of contami-

nated vegetables, several reports have been published

that describe the bacterial contamination of RTE

vegetables. For example, Kaneko et al. (1999) col-lected 196 samples from two food factories located in

the suburbs of Tokyo to examine the bacterial con-

tamination of RTE vegetables in the various process-

ing steps including trimming, washing, slicing, soak-

ing, dehydrating, blending and packaging. High

aerobic plate counts were found in most samples even

after preparation. B. cereus was detected at rates of

10.5% and 20% before and after preparation, respec-

tively. In their investigation, Listeria monocytogenes

was not found in the samples (Kaneko et al., 1999).

However, Garca-Gimeno et al. (1996) reported that,

out of a total of 70 ready-to-use mixed vegetable salad

samples, 21 (30%) were observed to contain L.

monocytogenes. In Taiwan, few outbreaks of food-borne diseases caused by L. monocytogenes have been

reported. According to epidemiological data, in the

period between 1986 and 1995, bacterial pathogens

were reported to be the major causes of foodborne

disease outbreaks in Taiwan (555 out of the 852

outbreaks, 65%). The three most commonly involved

bacteria were, Vibrio parahaemolyticus (197 of the

555 outbreaks, 35%), Staphylococcus aureus (169 of

the 555 outbreaks, 30%) and B. cereus (104 of the 555

outbreaks, 18%) (Pan et al., 1997).

Although there is a growing demand for 18 jC

RTE food products, no information is available

regarding the microbiological quality of these prod-

ucts in Taiwan. The present study was hence under-

taken to determine the microbiological quality of a

variety of 18 jC RTE food products retailed in central

Taiwan. Since this was the first investigation of 18 jC

RTE food products in this country, these results

provide basic information about the microbiological

quality of these products.

2. Materials and methods

2.1. Samples

A total of 164 samples were obtained for bacter-

iological examination. Various types of 18 jC RTE

food products were obtained from convenience stores

and supermarkets in central Taiwan periodically from

September 1999 through May 2000. Among the 164

samples, there were 25 samples of hand-rolled sushi

in cone shape, 50 samples of sandwich, 15 samples of

cold noodles with entree, 52 samples of seaweedrolled rice ball and 22 samples of sushi. The 164

samples, which were manufactured by 16 factories,

were also grouped on the basis of their major compo-

nents, i.e., 25 samples were mainly composed of ham,

50 samples were mainly made of seafood, 44 samples

were mainly made of meat, while 45 samples were

mainly composed of vegetables. All the samples were

transported to the laboratory at low temperature (

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25 g of each sample was homogenized for 2 min with

225 ml of 0.1% sterile peptone water using a Stom-

acher (model 400, Seward Medical, London, UK).

Serial dilutions were performed as required. The pHof the food samples was measured using a digital pH

meter (Hanna 8417, Italy) in a 1:10 (w/v) mixture of

the homogenate in distilled water.

2.2. Microbiological analyses

The total aerobic bacteria were enumerated by

using Plate Count Agar (PCA, Difco, Detroit, MI,

USA) and incubating the plates at 37 jC for 48 h.

ChromocultR coliform agar plate (Merck, Darmstadt,

Germany) were used for the enumeration of E. coli

and coliforms. For S. aureus enumeration, serial

dilutions of vegetarian food homogenates were plated

on BairdParker Agar (Oxoid, Hampshire, England)

with egg yolk emulsion (50 ml l1) a n d K 2TeO3solution (10 ml l1), and incubated at 37 jC for 48

h. Typical colonies were confirmed by using a Sta-

phaurex rapid test kit (Welcome Diagnostics, Eng-

land) (Fang et al., 1999). The number ofB. cereus was

determined by using the surface plating technique on

B. cereus agar base (Oxoid) as described by Vander-

zant and Splittstoesser (1992). Typical B. cereus

colonies were counted, transferred to nutrient agarslants, and further confirmed by microscopic and

biochemical characterizations using API 50 CHB

identification kit (API laboratory products, Basingsto-

ken Hants, England). Pseudomonas agar F (Oxoid)

plates were used for the enumeration of Pseudomonas

spp. based on manufacturers procedures. A spiral

plater (Spiral system, Model DU2, Cincinnati, OH)

was used to enumerate the isolates from 18 jC RTE

food samples (Fang et al., 1997b). All plates wereincubated under aerobic conditions. Duplicate agar

plates of between 30 and 300 colonies were counted,

and mean counts were calculated.

3. Results

The microbial analyses of 18 jC RTE food sam-

ples are presented in Table 1. Regarding the distribu-

tion of microbial populations, 59.8% of the samples

were found to have an aerobic plate count of >105

CFU g1. The largest population distribution for

coliforms was found in the range of 104 to

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range of aerobic plant count, coliform, E. coli, B.

cereus, S. aureus and Pseudomonas spp. in the tested

samples are shown in Table 2. The pH values of all

samples were below 7.0, except for the cold noodles,which had pH values that ranged from 5.18 to 8.20,

depending on the amount of sodium bicarbonate

added to the noodle (Table 2). A higher percentage

of coliforms was detected in sandwiches (88.0%) and

hand-rolled sushi in cone shape (84.0%), as compared

to sushi (68.2%), seaweed rolled rice balls (65.4%)

and the cold noodle (60.0%). Although hand-rolled

sushi in cone shape and sandwiches showed a higher

incidence of E. coli, i.e., 16.0% and 10.0%, respec-

tively, as compared to the rest of the three types of 18

jC RTE food samples, seaweed rolled rice balls had

the highest level of contamination with E. coli (5.15

log CFU g1), among the five types of samples tested

in this investigation. B. cereus was present in 66.7%

of cold noodles, with the highest levels of the

pathogen being found in seaweed rolled rice balls

(5.51 log CFU g1). S. aureus was found in 25.0% of

seaweed rolled rice balls (2.30 to 5.00 log CFU g1)

as compared to 11.9% in sandwiches (2.30 to 5.07

log CFU g1). The highest percentage of contami-

nation with psychrotrophic Pseudomonas spp. was

found in hand-rolled sushi in a cone shape (64.0%),

followed by sandwiches (58.0%)(Table 2). The per-centage of various types of 18 jC RTE foods not

meeting the microbiological standard accepted by the

Republic of China Government is shown in Fig. 1.

Many of the food samples exceeded the microbio-

logical standards accepted by this country for coli-

forms, with sandwiches showing the highest rate

(88.0%) of noncompliance with standards. On theother hand, the percentage of noncompliance with

standards for E. coli was much lower, as compared to

the coliforms, with the hand-rolled sushi in a cone

shape showing the highest rate of noncompliance

(16.0%), followed by sandwiches (10.0%). The foods

with the highest percentages that failed to meet the

standards for B. cereus and S. aureus were cold

noodles (66.7%) and seaweed rolled rice balls

(25.0%), respectively (Fig. 1).

The samples were also divided into four groups

based on the major components, i.e., ham, seafood,

meat and vegetable groups. The detection range for

aerobic plant counts, coliforms, E. coli, B. cereus, S.

aureus and Pseudomonas spp. in these four groups are

given in Table 3. The highest percentage of coliforms

was observed in ham (88.0%) and seafood (80.0%) as

the major component of the 18 jC foods when

compared to the RTE foods made up of meats

(72.7%) and vegetables (62.2%) (Table 3). Although

18 jC foods made up of ham showed the highest

incidence rates ofE. coli (16%), samples composed of

seafood contained the highest levels of E. coli (5.15

log CFU g

1). B. cereus was present in 62.5% of meatsamples, but the highest levels of this pathogen were

observed in seafood (5.59 log CFU g1). S. aureus

was found in 26.1% of the ham samples (2.60 to 4.58

Table 2

pH values and detection range of aerobic plant count, coliform, E. coli, B. cereus, S. aureus and Pseudomonas spp. in various types of 18 jC

RTE food products

Types of No. of pH Range of microbial count (log CFU/g)

products samplesAPC Coliform E. coli B. cereus S. aureus Pseudomonas

spp.

Hand-rolled sushi

in cone shape

25 4.35 6.05 3.30 9.45

(96.0)a2.607.18

(84.0)

2.302.90

(16.0)

2.303.78

(41.7)

3.604.58

(18.2)

2.306.26

(64.0)

Sandwich 50 4.34 6.72 3.60 8.64

(94.0)

2.909.60

(88.0)

2.304.00

(10.0)

2.304.95

(53.3)

2.305.07

(11.9)

2.306.07

(58.0)

Cold noodles 15 5.18 8.20 3.00 8.65

(86.7)

2.305.45

(60.0)

0.002.30

(6.7)

2.304.33

(66.7)

2.603.30

(14.3)

3.304.30

(20.0)

Rice balls rolled

in seaweed

52 4.49 6.50 3.30 8.60

(98.1)

2.306.11

(65.4)

2.975.15

(3.9)

2.305.51

(56.0)

2.305.00

(25.0)

2.304.30

(30.8)

Sushi 22 4.51 6.11 2.30 8.16

(95.5)

2.307.55

(68.2)

3.263.45

(4.6)

2.303.51

(18.2)

2.304.26

(13.6)

2.784.30

(22.7)

a Numbers in parentheses indicate percentage of positive samples.

T.J. Fang et al. / International Journal of Food Microbiology 80 (2003) 241250244

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log CFU g1), as compared to 13.6% of samples

containing vegetables as their major component,which contained the highest levels of this pathogen

(5.07 log CFU g1). The highest percentage of con-

tamination with psychrotrophic Pseudomonas spp.

was found in products made up of ham and seafood

(both were 48.0%), followed by meat (43.2%) and

vegetables (33.3%) as the major components (Table

3). The percentages of 18 jC RTE foods made of

various major components, which were not compliant

with microbiological standards accepted by Taiwan, isshown in Fig. 2. A high portion of the food samples

exceeded the microbiological standards accepted by

this country for coliforms; products made of ham had

the highest rate (88.0%) of noncompliance with stand-

ards. On the other hand, the percentage of noncom-

pliance with standards for E. coli was much lower as

compared to coliforms, with ham products showing

Table 3

Detection range of aerobic plant count, coliform, E. coli, B. cereus, S. aureus and Pseudomonas spp. in 18 jC RTE food products made from

various major raw materials

Major ingredients of No. of Range of microbial count (log CFU/g)

the RTE products samplesAPC Coliform E. coli B. cereus S. aureus Pseudomonas spp.

Ham 25 3.78 9.45

(96.0)a2.909.60

(88.0)

2.303.88

(16.0)

2.304.36

(41.7)

2.604.58

(26.1)

3.305.14

(48.0)

Seafood 50 3.30 7.30

(98.0)

2.306.11

(80.0)

2.305.15

(6.0)

2.305.59

(46.8)

2.305.00

(21.4)

2.304.88

(48.0)

Meat 44 3.30 8.65

(93.2)

2.306.38

(72.7)

2.302.60

(4.5)

2.304.80

(62.5)

2.303.60

(15.4)

2.306.26

(43.2)

Vegetable 45 3.30 8.64

(93.3)

2.307.55

(62.2)

2.303.60

(4.4)

2.304.95

(42.2)

2.605.07

(13.6)

2.305.32

(33.3)

a Numbers in parentheses indicate percentage of positive samples.

Fig. 1. Percentage of various types of 18 jC RTE food products that did not comply with the microbiological standards imposed by the Chinese

Government regarding aerobic plate count (APC), coliforms, E. coli (EC), B. cereus (BC) and S. aureus (SA). The 18 jC RTE food products are

divided into five groups: hand-rolled sushi in cone shape ( ); sandwiches ( ); cold noodles (5); rice balls rolled in seaweed ( ); and sushi ( ).

The microbiological standards for ready-to-eat foods are as follows: coliforms, less than 10 MPN/g; E. coli and S. aureus, not detectable; B.

cereus, less than 100 CFU/g.

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Fig. 2. Percentage of aerobic plate count (APC), coliforms, E. coli (EC), B. cereus (BC) and S. aureus (SA) not meeting the microbiological

standards imposed by the Chinese Government in 18 jC RTE food products made from four types of major component. The 18 jC RTE food

products are divided into four groups based on their major ingredients: ham ( ); sea foods ( ); meats (5); and vegetables ( ). The

microbiological standards for ready-to-eat foods are as follows: coliforms, less than 10 MPN/g; E. coli and S. aureus, not detectable; B. cereus,

less than 100 CFU/g.

Fig. 3. Incidence of aerobic plate count (APC), coliforms, E. coli (EC), B. cereus (BC), S. aureus (SA) and Pseudomonas spp. (PS) in 18 jC

RTE food products with different pH values. The food samples were divided into three groups based on their pH values: 4.00 4.99 ( ), 26

samples; 5.00 5.99 ( ), 100 samples; and z6.00 (5), 38 samples.


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the highest rate of noncompliance (16.0%), followed

by seafood (6.0%). Foods that contained meat and

ham were the samples with the highest percentages

that failed to meet the standards for B. cereus and S.aureus, with a rate of 62.5% and 26.1%, respectively

(Fig. 2).

Fig. 3 shows the incidence of aerobic plate count,

coliforms, E. coli, B. cereus, S. aureus and Pseudo-

monas spp. in 18 jC RTE foods with different pH

values. The foods were divided into three groups,

which were a pH range of 4.004.99, 5.005.99 and

z6, with sample sizes of 26, 100 and 38, respectively.

The highest levels of APC, coliforms, B. cereus, S.

aureus and Pseudomonas spp. were found in the pH

range of 4.00 to 4.99, with positive samples of 80.8%,

42.3%, 69.6%, 95.7% and 69.6%, respectively (Fig.

3). On the other hand, the highest rate of positive E.

coli sample was found in the pH range z6 (94.4%).

The percentage of 18 jC RTE foods, manufactured by

different factories, that were not in compliance with

the microbiological standards of the Republic of

China Government are shown in Table 4. In general,

a higher percentage of samples not in compliance with

the coliforms standards of Taiwan were found, as

compared to the samples that did not meet the E. coli

standards (Table 4). Seven factories, which produced

more than 80% of 18 jC ready-to-eat foods, did not

meet the coliforms standard. On the other hand, the

highest incidence rate among the 18 jC RTE foods

produced by the 16 factories, which were not com-pliant with the E. coli standard, was 37%.

4. Discussion

The large number of aerobic plate count, psychro-

trophic Pseudomonas spp., indicator organisms (coli-

forms and E. coli) and pathogens ( B. cereus and S.

aureus) detected in the 18 jC RTE food samples

surveyed in this investigation revealed that contami-

nation of these foods presented a potential health

hazard to consumers. The results presented in this

paper had submitted to Department of Health in

Taiwan. Local authorities to improve the safety of

these products have carried follow-up assessments of

the factories that produce 18 jC RTE food products.

Ren et al. (1997) discussed the potential sources of

microbial contamination of 18 jC box meal process-

ing. After running a critical control point (CCP)

decision tree of the hazard analysis critical control

point (HACCP) system, five CCPs were chosen by

the authors. They reported that at each CCP, corrective

Table 4

Percentage of aerobic plate count, coliform, E. coli, B. cereus and S. aureus not meeting the microbiological standard established by the Chinese

Government in 18 jC RTE food products made by different factories

Factories No. of samples Percentage of samples not meeting the microbiological standarda

APC Coliforms E. coli B. cereus S. aureus

A 2 50.0 0.0 0.0 0.0 0.0

B 8 47.0 75.0 37.0 50.0 12.5

C 19 84.0 84.0 0.0 57.9 27.3

D 3 67.0 67.0 0.0 66.7 33.3

E 17 47.0 47.0 0.0 58.8 29.4

F 6 67.0 83.0 0.0 33.3 0.0

G 28 50.0 75.0 14.0 84.9 21.4

H 7 34.0 14.0 0.0 78.6 0.0

I 1 0.0 100.0 0.0 100.0 0.0

J 3 67.0 33.0 0.0 33.3 0.0

K 1 0.0 0.0 0.0 0.0 0.0

L 3 67.0 100.0 0.0 0.0 33.3

M 1 100.0 100.0 0.0 0.0 0.0

N 9 33.0 78.0 22.0 44.4 11.1

O 34 79.0 88.0 15.0 58.8 20.6

P 22 82.0 86.0 0.0 57.2 14.3

a The microbiological standards for ready-to-eat foods are as follows: coliforms, less than 10 MPN/g; E. coli and S. aureus, not detectable;

B. cereus, less than 100 CFU/g. For the aerobic plate count, for quality control purpose, 105 CFU/g was chosen as the limit in this investigation.


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actions were immediately taken during the 18 jC box

meal production. The bacteriological quality of the 18

jC box meal was significantly increased (P6

log CFU g1, indicates contamination and poor

microbiological quality. The reason may be contami-

nated raw material, cross-contamination during prep-

aration or high storage temperature. Most 18 jC RTE

foods used in this investigation contain fresh vegeta-

bles. Coliforms on these products reflect the initial

microflora of the vegetables in the growing fields andthe recontamination during cutting and further pro-

cessing.

According to the Food Sanitation Standard (1993)

of Taiwan, ROC, coliform counts should not exceed

10 MPN g1 and E. coli should not be detected at all

in RTE foods. In addition, foodborne pathogens such

as S. aureus, Salmonella spp. and L. monocytogenes

should not be detected in RTE foods. On the other

hand, the limit forB. cereus in RTE foods is 100 CFU

g1. In this investigation, 25.0%, 92.1%, 50.2% and

82.1% of the 18 jC RTE food products fulfilled the

requirements when coliforms, E. coli, B. cereus and S.

aureus, respectively, were used as indicators. Seaweed

rolled rice balls and 18 jC stored foods made of ham

were found to have the highest rate of noncompliance

with the S. aureus standard in this study (Tables 3 and

4). The presence of S. aureus in the food samples

tested in this study indicates improper handling and

possible cross-contamination (Garcia et al., 1986;

Snyder, 1998). This microorganism not only plays

an important role in foodborne diseases in the United

States (Bean et al., 1990) but in Taiwan as well. S.

aureus is the second most commonly found foodborne pathogen in Taiwan. The number of outbreaks in

Taiwan due to this bacterium ranged from 11 to 24

annually, in the period from 1986 to 1995 (Pan et al.,

1997). The enterotoxin A-producing strains of S.

aureus were the most frequently isolated ones during

the outbreaks in Taiwan. Pan et al. (1997) reported

that 53.3% (8 out of 15) of the S. aureus outbreaks in

Taiwan in 1994 were associated with enterotoxin A.

B. cereus is emerging as an important foodborne

pathogen because of its cosmopolitan distribution. A

review by Granum and Lund (1997) indicated that B.cereus had become one of the more important causes

of food poisoning in the industrialized world. This

pathogen is usually isolated from samples of raw rice

and thus can be considered as being part of its normal

flora (Parry and Gilbert, 1980). Of the 18 jC RTE

food samples examined in this study, 49.8% contained

B. cereus, which is higher than in other investigations.

This microorganism was isolated from 3.4% of veg-

etarian food products (Fang et al., 1999), 22% of RTE

street-vended foods (Mosupye and Von Holy, 1999),


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4.8% of cold meals served by airlines (Hatakka,

1998a), 10.5% of RTE fresh vegetables (Kaneko et

al., 1999), 8.4% of rice products (Chyan et al., 1989)

and 2% of cooked rice (Nichols et al., 1999). How-ever, in one investigation, more than 83% of ready-to-

serve foods, including noodles, mashed potatoes, rice,

succotash, lima beans, skim milk, infant formula

(powdered), nonfat milk, chicken salad, egg salad,

turkey gravy, beef gravy and cauliflower, were found

to be contaminated with B. cereus (Harmon and

Kautter, 1991). During the years 1986 to 1995, 104

outbreaks caused by B. cereus were reported in

Taiwan, and this bacterium was noted to be the third

most commonly implicated foodborne pathogen in

this country (Pan et al., 1997). Cooked rice plays an

important role in meal in Asian countries, such as

Taiwan, Japan and China. Many of the 18 jC RTE

food products contain cooked rice, which has long

been recognized as a vehicle of B. cereus food

poisoning (Goepfert et al., 1972; Schiemann, 1978).

The high incidence of B. cereus (49.8%) in the 18 jC

RTE food products reveals a potential hazard to the

consumer. B. cereus has also been responsible for

illness transmitted by the consumption of fresh veg-

etables (Portnoy et al., 1976).

Although 18 jC RTE foods were developed in

Japan, the market share of this type of food has grownrapidly in Taiwan in recent years. Yau and Huang

(1994) established the sensory profile of 18 jC

cooked rice; the present investigation provides the

microbiological quality of 18 jC RTE food products.

The results of our study indicate that there are some

handling practices in the manufacture of 18 jC RTE

foods that require more attention. Temperature control

is a key issue in producing this type of food. In

addition, it is also important that the products are

manufactured under Good Hygienic Practices. Most

importantly, an appropriate hazard analysis criticalcontrol point (HACCP) system, which has been

implemented in some box meal factories in Taiwan

(Fang and Jeng, 2002), should be developed to

enhance food safety.

Acknowledgements

This work was supported by Department of Health,

Republic of China (Project DOH89-TD-1052). Any

findings, conclusions and recommendations expressed

in this paper are those of the authors and do not

necessarily reflect the official views of their sponsors.

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