EFFECT OF CHLORINATED WASH WATER ON QUALITY OF HEAT SHOCKED MUSSEL MEAT

MA. PATRICIA V. AZANZA’,’, RHODORA V. AZANZA2 and SHARON R. VENTURA’

’ Department of Food Science and Nutrition College of Home Economics University of the Philippines

Diliman. Quezon City3 Philippines

Marine Science Institute College of Science

University of the Philippines Diliman, Quezon City, Philippines

Accepted for Publication September 21,2003

ABSTRACT

Chlorine-assistedchilledtumble washing ofgreen mussel meats was done using 5 and I0 ppm chlorine solutions maintained at 5 and IOC for 3 min. No significant difference (P 0.05) was established in terms of meat yield, pH, Aw or sensory qualities for tumble washed samples. The mussel meats were given sensory acceptance ratings of up to “like slightly”. A 2% weight gain of mussel meats was established afrer washing. Heat shocking in tandem with tumble washing 4ec ted 1-3 unit log reduction in TPC and coliform counts and about a 4 log reduction in Vibrio spp. counts of mussel meats. The 2 protocols were presented as value- adding steps to improve mussel meat quality. Philippine micro- and small-scale shellfish processors and vendors were identified as potential users of the technologypresented in the study.

INTRODUCTION

Green mussel, Perna viridis, is an undeveloped Philippine seafood resource of great market potential due to its fecundity and wide distribution in local coastal waters (Young and Sema 1982). Unfortunately, significant portions of green mussel harvests are channeled to local markets where it can command only minimal profit margins. Philippine green mussels are currently sold locally mainly as fresh

’Corresponding Author: Department of Food Science and Nutrition, College of Home Economics, University of the Philippines, Diliman 1101, Quezon City, Philippines. TEL: (+632) 920-5301 loc. 6552 or 9273828;FAX: (+632) 9262813 OK 9215967; EMAIL:rnagatricia.azanz@up.edu.ph or mpv-azanz@yahoo.com

Journal of Muscle Foods 14 (2003) 329-341, All Rights Reserved. 0 Copyright 2003 by Food & Nutrition Press, Inc.. Trumbull, Connecticut. 329

330 M.P.V. AZANZA. R.V. AZANZA and S.R. VENTURA

shellstock with almost no value-added postharvest process applied to it. In Thailand, a comparatively small volume of the green mussel harvest reaches the consumer as shellstock since the technology of heat shocking, shucking and ice storage are now combined for commercial use to produce processed forms of the raw material (Vakily 1986).

Motes (1982) and Chai et ul. (1984) described tumble washing as another value- added processing step for shucked meat of bivalves prior to packaging and storage. The application of tumble washing using potable water with a stream of clean, oil- free air to rid the shellstock of grit and bits of shell have been studied by Motes (1982). Chai et ul. (1984) reported the use of tumble washing of freshly shucked oysters by blowing in aerated chlorinated water prior to pasteurization in flexible pouches.

Local studies on mussel meat purification have focused mainly on the application of depuration procedures (Gacutan et al. 1984; Genesera 1992). Unfortunately, local commercial application of depuration is hindered by the required large capital outlay and operating costs. Moreover, the process requires fixed land-based facilities equipped with water disinfecting systems, water distribution lines and, large shellfish tanks which small shellfish industries could not normally provide.

Tumble washing of bivalve meat in chlorine-disinfected wash water is a procedure for green mussel processing that is yet to be explored locally. Although this procedure might be limited to disinfection of surface contamination of bivalve meats, it could be used to extend shelf-life and improve quality ofmussel meats that are intended for fiuther cooking. Tumble washing may be a more applicable value- added method for shellfish harvested in developing countries such as the Philippines considering the relative simplicity ofthe technology and lower financial investments needed for its implementation. The application of chlorine-assisted tumble washing protocols is being recommended based on the current Codex Alimentarius Commission stipulated allowable use of i 10 ppm chlorine in wash water that comes in contact with seafood (FAO/WHO 2000).

The objective of this study was to establish the effects of chlorine-assisted tumble washing on the physical, sensory and microbiological qualities of heat shocked green mussels. The application of chlorinated wash waters was the identified washing protocol because chlorine is a common, cheap form of food disinfectant available in the Philippines. Results of this study was envisioned to help micro- and small-scale industries in the production of value-added green mussel products.

MATERIALS AND METHODS

Sample Preparation

Fresh green mussels with a marketable size of 40 to 60 mm ranging in age from 4 to 6 months were collected from Bacoor, Cavite, Philippines, over the period of

CHLORME-ASSISTED WASHING OF MUSSEL MEAT 33 1

September to October 2002. The mussels were collected in Styrofoam containers with ice then transported to the laboratory within 1 h of harvest. The freshly collected mussel shellstocks were declustered and washed with tap water under high-pressure to remove dirt and byssal threads. Gaped shellstocks and those exhibiting foul odors were sorted out and discarded.

The freshly collected shellstocks were heat shocked using hot water treatments prior to shucking and tumble washing. Five kilogram mussel shellstocks, evenly distributed into 2 draw-string nylon mesh bags were submerged into boiling water for 1 min at a ratio of 1 :4 mussel to water ratio (w/v). Shucking of shellstocks was done manually by inserting a blunt knife through the gaped shell halves and sliding it underneath the mantle towards the shell hinge to sever the posterior and anterior adductor muscles of the mussel meat from the shell. The shucked meats were collected and drained during the shucking procedure in an ice-jacketed container. The tumble washing of the collected meat occurred within 30 min from heat shocking and shucking of the green mussels.

Tumble Washing Procedure

A top loading laundry washing machine was modified for use as a mechanical washing system for the tumble washing experiments of heat shocked mussel meats by furnishing tubular plastic grids as agitator guards and as supports to hold the plastic vessels containing shucked mussel meats. Tumble washing was conducted in the washing tub equipped with a vertical-axis agitator at 400-500 rpm. Shucked mussel meats were evenly distributed in 3 mesh plastic boxes (22 x 12 x 7.5 cm) and were exposed to chilled chlorine solutions of calcium hypochlorite (Ca(OC1)J at concentrations of 5 or 10 ppm maintained at 5 and 1 OC for 3 min. A ratio of 1 : 10 meat to chlorine solution (w/v) was maintained during the tumble washing experiments. Within 2 h of the tumble washing experiments, the washed meats were subjected to physical, sensory and microbiological analyses. Samples were refrigerated at 5-8C until subjected to analyses.

Analyses of Physical Properties of Perna viridh

The meat yield (%), pH and water activity (Aw) of the heat shocked and tumble washed green mussel meats were established. The weight gain (YO) of the final product was determined based on the weight of the tumble washed mussel meats relative to the weight of the heat shocked mussels.

For the measurement of pH, test samples were homogenized in a blender at high speed and diluted with distilled water to make a 1 5 (w/v) mussel meat to water ratio (AOAC 1990). The pH values of the samples were determined using the Suntex Digital pH meter (Model SP-7). The Aw of the test samples was determined using the Wert-Messer Aw value analyzer (Model 583, Germany). A (BaCl), solution was used to calibrate the Aw meter. All analyses were conducted in 3 trials.

332 M.P.V. AZANZA. R.V. AZANZAand S.R. VFNTUR4

Evaluation of Sensory Qualities

A 40 member consumer type panel assessed the general acceptability and described the sensory characteristics ofthe heat shocked and tumble washed mussel samples. Samples were evaluated for acceptability of overall quality, color, odor and texture. The 9-point hedonic scale, ranging from 9=like extremely to 1= dislike extremely, was used to determine the degree of acceptability of the test samples. The descriptive attributes of the test samples were evaluated using a 3-point labeled scale. Panelists evaluated the samples for texture (l=gluey, viscous and slimy, 3 = f m , moist and springy), odor (l=fecal, ammoniacal, nauseating, 3=fresh seaweedy, seawater odor), and, perceptible residual chlorine odor (1 =imperceptible chlorine odor, 3=distinct chlorine odor). For color description, each panelist was presented with separate sets of male and female mussel samples and asked to describe the color of the male (l=cream, 3= milky white) and female (1 =light yellow, 3=red orange) bivalve meats. For color acceptance rating, each panelist was asked to make only a single rating for all samples assessed.

Microbiological Analyses

To compare the effects of combined heat shocking and tumble washing using 10 ppm chlorine concentration maintained at 5C for 3 min on the microbiological quality of the mussels relative to heat shocked and untreated control samples, tests for total plate count (TPC), coliforms, Escherichia coli and Vibrio spp. were conducted. Tests for the presence of Salmonella spp. per 25 g sample was also done. All microbial analyses were conducted in triplicate.

The TPC of the meat samples for each treatment was determined as described in the U.S. Bacteriological Analytical Manual (Peeler and Maturin 1992). Pour plating of peptone saline dilutions into Standard Methods Agar (Pronadisa Hispanlab, Spain) were conducted in duplicate. Inoculated plates were incubated at 35C for 24 h. Results of TPC are reported as cfdg sample.

Coliform counts were conducted based on a 3-tube Most Probable Number (MPN) method (Brenton et al. 2001). Triplicate tubes of Lauryl Sulfate Tryptose (LST) broth (Pronadisa Hispanlab, Spain) were inoculated with peptone saline dilutions of the mussel samples and incubated at 35C for 24 h. Negative tubes, showing absence ofturbidity and gas production, were reincubated for an additional 24 h. Positive LST tubes were streaked onto dry plates of solid Eosin Methylene Blue (EMB) agar (Pronadisa Hispanlab, Spain) to c o n f m the presence of coliforms. Streaked plates were incubated at 35C for 24 h. Flat, dark-centered colonies with a metallic sheen on EMB agar were recorded as coliforms and test results were reported as coliform MPN per gram of sample.

Escherichia coli (EC) counts were also determined using a 3-tube MPN method (Weiss et al. 1983; Hitchins et al. 1992). Loopfuls from the positive LST tubes from the coliform analysis were subcultured to EC broth (Pronadisa Hispanlab,

CHLORINE-ASSISTED WASHING OF MUSSEL MEAT 333

Spain) and incubated at 44.0-44.5C for 24 and 48 h. Inoculated EC tubes were examined for gas formation and turbidity after 24 h. Negative tubes were reincubated for another 24 h. Positive EC tubes were streaked onto dry plates of EMJ3 agar and incubated at 35C for 24 h. The EMB plates were examined for flat, dark-centered colonies with a metallic sheen. Results are reported as E. coli MPN/g sample.

Vibrio spp. counts in the mussel samples were determined using the pour plate method described by Swanson et al. (1992). Twenty-five gram samples of the mussel meats were homogenized with 225 mL alkaline peptone water (APW). Serial dilutions of APW were pour plated onto Thiosulfate-citrate-bile salts-sucrose (TCBS) agar (Pronadisa Hispanlab, Spain). Inoculated plates were incubated at 35C for 24 h. Colonies were counted and are reported as Vibrio spp. cfdg sample.

Tests for the detection of Salmonella spp. were based on the procedure described in the Bacteriological Analytical Manual (Andrews et al. 1992). Twenty- five gram samples were homogenized and placed in buffered peptone water for microbial resuscitation and incubated for 16-20 h at 37C. One milliliter each of resuscitated culture was transferred to 10 mL Selenite Cystine (SC) broth (Pronadisa Hispanlab, Spain) in duplicate. The inoculated SC broth tubes were incubated for 18-24 h at 37C. Loopfils of culture suspension from incubated SC broth tubes were streaked onto dry solid Bismuth Sulfite (BS) agar plates (Pronadisa Hispanlab, Spain) and incubated at 37C for 24-48 h. Typical Salmonella spp. isolates, which appeared black, gray or brown, with or without a metallic sheen, were subjected to biochemical tests to c o n f m the presence of Salmonella spp. Confirmed Salmonella spp. isolates were those which showed positive reactions for glucose fermentation, H,S production, Simmon’s citrate utilization and agglutination by omnivalent anti-Salmonella A67 sera (Safm, Germany), and negative for indole formation and urease activity. Presence of Salmonella spp. is reported as positive or negative per 25 g sample.

Statistical Analysis

A 2x2 design was used to evaluate the effects of chlorine-assisted tumble washing for heat shocked samples based on the physical and sensory qualities of the mussels. The factors considered were chlorine concentrations (5 or10 ppm) and temperature (5 or 1OC). Analysis of variance (ANOVA) and Duncan’s Multiple Range Test (DMRT) were used to detect significant differences in the mean values of physical and sensory qualities ofthe mussel meat samples (P < 0.05) (Gatchalian 1989).

Results of microbiological tests for Vibrio spp., coliform counts and TPC of untreated (control), heat shocked and tumble washed mussel meats using 10 ppm chlorine concentration at 5C for 3 min were compared. The mean values of the 3 trials for each microbiological test were analyzed for significant difference (P < 0.05) using ANOVA and DMRT. For a microbial count where less than (<) a value of a number (n) was established, the equivalent value of n-1 was assigned based on

334 M.P.V. AZANZA. R.V. AZANZAand S.R. VENTURA

the method used by Barile (1990) and Brenton et al. (2001) for statistical evaluation of microbial data. Specifically, coliform counts with values of < 0.300 x 10' W N / g and Vibrio spp. counts of < 1 .OOO x 10' cfu/g were assigned the equivalent values of 0.200 x 10' MPNlg and 0.900 x 10' cfu/g, respectively. The percent change in microbial counts of untreated, heat shocked and combined heat shocked and tumble washed mussel meats were also calculated.

RESULTS AND DISCUSSION

Physical Properties of Tumble Washed Mussels

Table 1 details the effects of the tumble washing treatments on the meat yield (%), pH and Aw of mussel meats. All the test temperature-chlorine concentration combinations applied in the tumble washing experiments effected no significant difference (P < 0.05) on any of the physical characteristics of washed mussel meats evaluated. The meat yield (%) of the heat shocked mussel shellstocks ranged from 32.36 to 33.70%. The various tumble washing protocols effected about a 2% increase in the meat weight of the mussels that were sequentially heat shocked, shucked, and, tumble washed. Cunningham and Lawrence (1977) similarly demonstrated that exposure of pieces of pork, beef and chicken lean meat to chlorinated wash waters at 200 ppm concentration for 2 h brought about increase in weights at about 10.00, 1.60 and 8.30%, respectively. The tumble washed mussel meats in this study obtained fmal meat yield ranging from 33.04-34.38% relative to the initial shellstock weight.

TABLE I . PHYSICAL CHARACTERISTICS OF TUMBLE WASHED, HEAT SHOCKED P. VIMDIS MEATS* -_I _.___.___

Wash Water Mussel Meat -

Chlorlne Temperature pH Aw Meat Weld (%) concentration (C) Heal Tumble Weight Gain '

Shocked" Washed+* (PPW ..

5 5 6.877' 0.965' 32.440' 33.130' 2.126' 10 6.887' 0.965' 32.360' 33.036' 2.079'

10 5 6.893' 0.965. 33.493' 34.186' 2.031' 10 6.890. 0.970' 33.703' 34.380' 1.914'

--_ -- . -_l_l-._-,--l_ --..lllll-.l-,..- __.- _I_ - _ _ .__- ._- _.-_. * Vdues are means of 3 trials **Heat shocked meat yield (%) is the ratio ofthe weight ofthe recovered meat after exposure to boiling water for 1 min, relative to the initial weight of raw shellstocks, multiplied by 100 ***Tumble washed meat yield (%) is the ratio of the weight of the recovered meat after exposure to chlorine-assisted wash water using 10 ppm chlorine concentration at 5C and 3 min exposure time 'Weight gain (%) is the ratio of the weight of tumble washed mussel meat less the weight of heat shocked mussel meat relative to the weight of the tumble washed mussel meat, multiplied by 100 'Values in the same column with the same letter are not significantly different (P < 0.05)

CHLORINE-ASSISTED WASHING OF MUSSEL MEAT 335

The pH of the heat shocked and tumble washed mussel meats ranged from 6.88- 6.89.Genesera (1992) reported that the pH values of untreated green mussel meats harvested from the same sampling site for the test shellfishes used in this study ranged from 6.38-6.47.The alkaline nature of solutions of Ca(OCl), used as wash water (York 1987) may be the reason for the relatively higher pH of the tumble washed meat samples compared to the previously reported pH of untreated samples (Genesera 1992). Kim et al. (1999) reported that the interaction between chlorine wash waters and proteins in seafood increased the pH of washed meat samples.

The Aw values of the heat shocked and tumble washed mussel meats were in the range of0.95-0.97 (Table 1). These levels of Aw of tumble washed mussels indicate high perishability of the product. These Aw values were found not to be significantly different from each other (P < 0.05).

Sensory Quality of Tumble Washed Mussel Meats

Results of the sensory evaluation of the tumble washed mussel samples are shown in Table 2. The acceptance ratings of the heat shocked and tumble washed mussel samples for overall acceptability, color, texture, odor and perceptible residual chlorine ranged fiom “neither like nor dislike” to “like slightly”. Considering that the evaluated green mussel meat samples were minimally processed and were intended for final cooking, higher acceptance ratings for sensory parameters than those established in this study were not expected. As described by Quayle (1980), the heat shock method is a procedure intended to separate the valves of molluscs to facilitate shucking without necessarily cooking the meats.

The sensory characteristics of the tumble washed P . viridis meats ranged from a milky white color for male mussel samples to yellow-orange for female mussel samples, with a typical fishy odor, imperceptible to slightly detectable chlorine odor, and a soft and watery to finn, moist and springy texture. Generally, the various tumble washing protocols did not result in significant differences between the descriptive ratings of odor, residual chlorine odor, or female color of the tumble washed meat samples (P < 0.05). Watson and Rout (2000) similarly reported that shrimps dipped in 50 ppm NaOCl solutions effected no apparent change in sensory characteristics.

Microbiological Quality of Tumble Washed Mussel Meats

Results of the microbial analyses for untreated, heat shocked and tumble washed P. viridis are shown in Table 3. The tumble washing protocol applied using 10 ppm wash water at 5C was found to effectively reduce the microbiological concentration in washed mussels in terms of TPC and coliform counts by 1-3 log units and Vibrio spp. counts by 4 log units. The chlorine concentration used in the tumble washing protocol was also found effective in reducing the count of Salmonella spp. to negative per 25 g mussel sample.

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c

5 5

2.m

2.00

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2.325'

2.100*

1.775'

6.400'

6.275'

6.425.

5.675.

5.550'

$ 10

1.846.

1.85

7'

2.325'

2.250-

1.750.

5.825'

6.100.

6.275.

5.750.

5.650.

B vl

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5 2.154'

1.643.

2.42

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1.875.

6.225'

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5.975'

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ptib

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the

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with

the

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re n

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5)

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M

ICR

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QU

ALI

TY O

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SHO

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ND

TU

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M C

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Mus

sel M

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eter

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cked

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b'e

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ashe

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Tota

l Red

uctio

n u

TPC

(cfu

/g)

1.75

9 x

10%

5.

560

x 10

- (9

6.84

) 2.

061

x I@

(62.93)

(98.

83)

s 2

Co

liom

(MPN

/g)

8.62

0 x

lp

4.000 x

10%

(53.

60)

3.45

3 x

10''

(91.

37)

(95.

99)

0

Tota

l Vib

no (

cfdg

) 3.

047

x I

F

1.43

3x iO

lb (9

9.95

) 0.

900

x 10

lb (3

7.20

) (9

9.97

) 0

3

G Sa

lmon

ella

(+/-

per 2

59)

+

z NA

- -1_1__

-

ij; F

*Val

ues a

re m

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of 3

tria

ls **

NA

, not

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licab

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ues i

n pa

rent

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are

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ctio

ns in

micr

obia

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in p

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ange

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4

338 M.P.V. AZANZA, R.V. AZANZAand S.R. VENTURA

Analysis of the fresh, untreated control mussel meat samples showed a mean TPC of about lo5 cWg. The regulatory limit set by ICMSF (1986) for TPC of fresh and fi-ozen shellfish is 10’ cWg. This regulatory standard for TPC of fresh and frozen bivalves is also followed in the Philippines (BFAR 2003). The sequential heat shocking and tumble washing protocols were able to effect a 2 log reduction from the initial TPC of untreated mussels which is equivalent to a 98.83% reduction. Kim et al. (1999) reported a 1 log reduction in the bacterial counts of scallops treated with 40-200 ppm of Cl0,using 5 min exposure time. According to Kim and Foegeding (1993), NaOCl and Ca(OCl), give the most active chlorine in sanitizing solutions among the various chlorine compounds. The additive cidal effects of heat shocking and chlorine-assisted tumble washing using Ca(OCl), effected higher reductions in the microbial load of the mussel samples than those previously reported for bivalves treated with chlorine washing alone.

The coliform counts of the control mussel samples were about 10’ MPN/g (Table 3). Considering that the shellfish growing waters in Cavite, Philippines, is known to be greatly affected by pollution (Aypa 1979; Barile 1990), the green mussel samples harvested &om Bacoor Bay, Cavite, for this study were expected to contain high coliform numbers. The combined heat shocking and tumble washing procedures were effective in decreasing coliform counts to about 10’ MPN/g, a total reduction of 95.99% from the initial coliform count (Table 3).

This study found E. coli counts in the control, heat shocked and tumble washed mussel meat samples to be < 3.00 MPN/g. Barile (1990) reported nondetection of E. coli using a 3-tube MPN method of analysis for oysters and mussels harvested from Bacoor Bay, Cavite, Philippines, during the months of June through November, 1987. The mussel samples harvested from the same site for this study were collected during the months of September through October, 2002. The high levels of coliforms in mussel meats evaluated in this study, despite the observed low recovery of E. coli, may be explained by the fact that the presence of coliforms in food does not necessarily indicate fecal contamination. Craven et al. (1997) reported that coliforms could survive and grow in microcosms associated with food in which enteric pathogens like E, coli are consistently absent.

Counts of Vibrio spp. up to lo4 cfdg for the untreated control mussel meat samples were established (Table 3). Barile (1990) reported similarly high levels of Vibrio spp. counts of up to 1 O5 cWg for mussels harvested from the same site where samples for this study were collected. The results of this study showed that heat shocking in tandem with tumble washing was effective in reducing the levels of Vibrio spp. counts by 4 logs, an equivalent of a 99.97% reduction. Studies by Varma et al. ( 199 1) demonstrated that direct exposure of Vibrio cholerae cells to 10 and 15 ppm chlorine concentrations for 3 min effected a decrease of 4 log units.

The tumble washing protocol was able to effectively reduce the Salmonella spp. concentration in green mussels to negative Salmonella spp. per 25 g sample (Table 3). Absence of Salmonella spp. per 25 g of fresh and processed samples is normally

CHLORINE-ASSISTED WASHING OF MUSSEL MEAT 339

set as an acceptable quality index in bivalve molluscs (ICMSF 1986; Shapton and Shapton 1991). Ridenour and Ingols (1993) previously reported that hypochlorite solution with 0.02 ppm of free available chlorine could effect 99.90% inactivation of Salmonella spp. after 5 min exposure.

CONCLUSIONS

This study established the physical, sensory and microbiological qualities of heat shocked and tumble washed Philippine green mussels. A meat recovery of about 30% was established for the treated mussels. The highest acceptance rating for the minimally processed meat samples intended for hrther cooking was "slightly accetable". The combined treatment of heat shocking and tumble washing using a 10 ppm chlorine solution maintained at 5C for 3 min effected 2 95% reduction in TPC, coliform, and Vibrio spp. counts in mussel meat. With the 2 treatments, Salmonella spp. counts were also reduced to negative per 25 g mussel sample.

The application of the shellfish processing technology evaluated in this study could be considered for other edible Philippine bivalves aside from green mussels. The technology may provide an opportunity for the marketing of bivalve meats as a value-added convenience product. Its adaptation for use by micro- and small-scale investors is highly conceivable due to simplicity and low implementation costs.

ACKNOWLEDGMENT

This study was made possible through funding ofthe Department ofAgriculture- Bureau of Agricultural Research, Diliman, Quezon City, Philippines.

REFERENCES

ANDREWS, W.H., BRUCE, V.R., JUNE, G., SATCHELL, F. and SHERROD, P. 1 992. Salmonella. In USFDA Bacteriological Analytical Manual, 7"' Ed., pp. 5 1-69, United States Food and Drug Administration (USFDA), USA.

AOAC. 1990. Oflcial Metho& ofAnalysis, 15"' Ed. Assoc. of Official Analytical Chemists, Washington, DC.

AYPA, S.M. 1979. Various factors affecting recovery and growth rate of transplanted mussels Perna viridis (Lime). Phil. J . Fisheries I7 (l) , 115-146.

BARILE, L.E. 1990. Bacterial purification of Philippine shellfish. In Post-Harvest Technology, Preservation andQualiW ofFish inSoutheastAsia, (P.J.A. Reilley, R.W.H. Parry and L.E. Barile, eds.) pp. 119-129, Proceedings ofthe workshop on Post-Harvest Technology, Preservation and Quality of Fish in Southeast Asia. International Foundation for Science, Sweden.

340 M.P.V. AZANZA, R.V. AZANZA and S.R. VENTURA

BFAR. 2003. Recommended microbiological limits. Personal Communication. Bureau of Fisheries and Aquatic Resources. Quezon City, Philippines.

BRENTON, C.E., FLICK JR., G. J., PIERSON, M.D., CROONENBERGHS, R.E. and PEIRSON, M. 200 1. Microbiological quality and safety of quahog clams, Mercenaria mercenaria, during refrigeration and at elevated storage temperatures. J. Food Prot. 64 (3), 343-347.

CHAI, T.J., HAN, T.J. and COCKEY, R.R. 1984. Microbiological quality of shellfish-growing waters in Chesapeake Bay. J. Food Prot. 57 (4), 229-234.

CRAVEN, H.M., EYLES, M.J. and DAVEY, J.A. 1997. Enteric Indicator Organisms in Foods. In Foodborne Microorganisms of Public Health Signijkance, 5"' ed., (A.D. Hocking, G. Arnold, I. Jenson, K. Newton and P. Sutherland, eds.) pp. 139-168, Australian Institute of Food Science and Technology (AIFST) Ltd., New South Wales.

CUNNINGHAM, H.M. and LAWRENCE, G.A. 1977. Effect of exposure of meat and poultry to chlorinated water on the retention of chlorinated compounds and water. J. Food Sci. 42 (6), 1504-1505, 1509.

FAO/WHO. 2000. Discussion paper on the use of chlorinated water. Codex Committee on Fish and Fishery Products, 24" Session, June 5-9, Norway.

GACUTAN, R.Q. et al. 1984. Detoxification of Pyrodinium generated PSP toxin in Perna viridis from Western Samar, Philippines. In Toxic Red Tides and Shellfish Toxicity in South East Asia, (A.M. White, M. Ankm and K.K. Hooi, eds.) pp. 80-85, South East Asian Fishery Development Center and International Development Center, Singapore.

GATCHALIAN, M. 1989. Sensoty Evaluation Methods for Quality Assessment and Development. College of Home Economics, University of the Philippines, Diliman, Quezon City.

GENESERA, J.A. 1992. The efficacy of chlorine depuration in detoxifying mussels (Perna viridis) contaminated with Paralytic Shellfish Toxins from Pyrodinium bahamense var. compressum. MS Thesis. University of the Philippines, Diliman, Quezon City, Philippines.

HITCHINS, A.D., FENG, P., WATKINS, W.D., RIPPEY, S.R. and CHANDLER, L. A. 1992. Escherichia coli and other coliform bacteria In USFDA Bacteriological Analytical Manual, 7"' Ed., pp.27-49, United States Food and Drug Administration (USFDA), USA.

products. International Commission for Microbiological Safety of Foods. http://www. health.act.gov.au/publications/foodsurvey/ 1996-971smoked.html. Date Accessed: December 20,2002.

KIM, J. and FOEGEDING P.M. 1993. Principles of control. In Clostridium botulinum. Ecology andControl in Fooh, (A.H.W. Hauschild and K.L. Dodds, eds.) pp. 123-126, Marcel Dekker, New York.

KIM, J.M., HUANG, T.-S., MARSHALL, M.R. and WEI, C . 4 1999. Chlorine dioxide treatment of seafoods to reduce bacterial loads. J. Food Sci. 64 (6),

ICSMF. 1986. Recommended microbiological limits for fish and fishery

1089-1093.

CHLORINE-ASSISTED WASHING OF MUSSEL MEAT 34 1

MOTES JR., M.L. 1982. A Research Note: Effect of chlorinated wash water on Vibrio cholerae in oyster meat. J. Food Sci. 47, 1028-1029.

PEELER, J.T. and MATURIN, L.J. 1992. Bacteriological Analytical Manual, 7'' Ed., pp. 17-26, United States Food and Drug Administration (USFDA), USA.

QUAYLE, D.B. 1980. Tropical oysters culture and methods. International Research Development Center, Ottawa.

RIDENOUR, G.M. and INGOLS, R.S. 1993. Bactericidal properties of chlorine dioxide. In Sanitizers: Halogens, Surface-Active Agents, and Peroxides, (B.R. Cords and G.R. Dychdala, eds.) In Antimicrobials in Foods, 2nd Ed., (P.M. Davidson and A.L. Branen, eds.) pp. 469-537, Marcel Dekker, New York.

SHAPTON, D.A. and SHAPTON, N.F. 1991. Principles andpractices for theSufe Processing of Foods. Butterworth-Heinemann Ltd., England

SWANSON, K.M.J., BUSTA, F.F., PETERSON, E.H. AND JOHNSON, M.G. 1992. Colony count methods. In Compendium of Methocis for the Microbiological Examination of Fooh, 3rd Ed., (C. Vaderzant and D.F. Splittstoesser, eds.) pp. 75-95, American Public Health Assoc. Washington DC.

VAKILY, M.J. 1986. Processing and marketing of green mussels (Perna viridis) in Thailand. In Cured Fish Production in the Tropics, (A. Reilley and L.E. Barile, eds.) Proceedings of a Workshop on the Production of Cured Fish.Apri1 14-25, University of the Philippines in the Visayas.

VARMA, P.R.G., IYER, T.S.G. and GOPAKUMAR, K. 1991. Incidence and viability of V. cholerae in seafood handling and processing. Food Technol. 45

WATSON, P. and PROUT, P. 2000. Technical development to improve hygiene in the inshore shrimp industry. In Discussion Paper on the Use of Chlorinated Water. F A O M O . Codex Committee on Fish and FisheIy Products, 24th Session, June 5-9, Norway.

M I S S , K. F., CHOPRA, N., STOTLAND P., RIEDEL G.W. and MALCOLM, S. 1983. Recovery of fecal coliforms and of E. coli at 44.5,45.0 and 45.5 C. J. Food Prot. 46, 172-177.

YORK, G.K. 1987. A guide to food plant sanitizers. Food Processing. 48(2), 118- 120.

YOUNG, A. and SERNA, E. 1982. Bivalve culture in the Philippines. In Culture in Asia and the Pa&. Proceedings of a Workshop Held in Singapore, Feb. 1 6- 19, (F.V. Davy and M. Graham, eds.).

(9), 188-193.