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LWT 41 (2008) 730–738

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Characterization of fermented silver carp sausages inoculatedwith mixed starter culture

Yongjin Hua,b, Wenshui Xiaa,�, Changrong Geb

aKey Laboratory of Food Science and Safety, Ministry of Education, Southern Yangtze University, Wuxi 214122, Jiangsu, ChinabSchool of Food Science and Technology, Yunnan Agricultural University, Kunming 650201, Yunnan, China

Received 16 August 2006; received in revised form 5 April 2007; accepted 5 April 2007

Abstract

To improve the characteristics and functionality, and increase the use of fish muscle, three groups mixed starter cultures (group one:

Lactobacillus plantarum-15, Staphylococcus xylosus-12 and Pediococcus pentosaceus-ATCC33316 [S-PXP]; group two: Lactobacillus

planatrum-15, Staphylococcus xylosus-12 and Lactobacillus casei subs casei-1.001 [S-PXC]; and group three: Staphylococcus xylosus-12,

Lactobacillus casei subsp. casei-1.001 and P. pentosaceus-ATCC33316 [S-XCP]) were inoculated in minced silver carp muscle to produce

a fermented fish product. During the 48 h fermentation at 30 1C, silver carp muscle inoculated with mixed starter cultures resulted in a

rapid pH decrease, suppression in the increase of thiobarturic acid (TBARS) values, total volatile base nitrogen (TVB-N), trimethylamine

(TMA), and the growth of spoilage bacteria and pathogens, and had higher whiteness than the control (without any starter) (Po0.05).

The changes in SDS-PAGE indicated extensive hydrolysis of muscle protein occurred during fermentation. This study showed that the

mixed starter cultures could substantially improve the flavor, digestibility, and nutritional value of the silver carp muscle.

r 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.

Keywords: Silver carp; Lactic acid bacteria; Staphylococcus xylosus; Fermented sausage; Mixed starter cultures

1. Introduction

Silver carp (Hypophthalmichthys molitrix) may be thecheapest and most abundant freshwater fish due to itsquick growth and resistance to stress, disease and roughhandling. In China fresh water fish, unlike marine fish,mainly marketed for fresh condition consumption. Themain processed products are salted fish and fish sauce.However, these products have high salt concentration(15–25% w/w) and, therefore, have limited nutrient valuebecause they cannot be consumed in large quantities(Aryanta, Fleet, & Buckle, 1991). The development ofnew fish products, which would be free of the fishy odorand taste, and which retained all the nutritional advantagesof fish, would enlarge the range of applications of silvercarp muscle. A promising approach to the creation of suchfish products seems to be through the use of fermentation.

0 r 2007 Swiss Society of Food Science and Technology. Pu

t.2007.04.004

ing author. Tel.: +86510 85869455;

812812.

ess: xiawshsytu@yahoo.com.cn (W. Xia).

The fermentation of fish for human consumption has manybenefits (Cooke, Twiddy, & Alan Reilly, 1987; Gelman,Drabkin, & Glatman, 2000; Paludan-Muller, Madsen,Sophanodora, Gram, & Moller, 2002). it could be usedas a low cost, convenient method for the unrefrigeratedpreservation of fish muscle and improve the organolepticqualities of fish and increase the nutritional value and/ordigestibility of the raw material.Some fermented meats or fish are very popular in

oriental countries and also in parts of western countries. Inrecent years, using pure bacterial cultures to produce a fish-type product is attracting increasing interest. Variousresearchers have stated that using lactic acid bacteria(LAB) in fish meat has improved the quality of the endproduct. According to Kim and Hearnsberger (1994), usingPediococcus acidilactici to manufacture fish sausage couldaccelerate the formation of lactic acid and significantlyinhibit the growth of spoilage bacteria and pathogens,which consequently extended the shelf life and alsoenhanced the safety. Rapid decline of pH not only givesthe products a unique lactic acid flavor, but also increases

blished by Elsevier Ltd. All rights reserved.

ARTICLE IN PRESSY. Hu et al. / LWT 41 (2008) 730–738 731

the texture firmness and mouthfeel due to the aciddenaturation of muscle proteins (Palumbo et al., 1993).Gelman et al. (2000) applied LAB fermentation withLeuconostoc mesenteroides, Pediococcus pentosaceus andLactobacillus plantarum to the minced yellowfin tuna.Under chill conditions the presence of L. mesenteroides

gave changes towards a meaty flavour and juicy texture,low values for chemical indices of spoilage and extendedshelf-life (over 4 weeks). Yin, Pan, and Jiang (2002) usedLAB to ferment mined mackerel. The fermented productssubstantially inhibited the development of volatile basicnitrogen, suppressed the growth of other microflora, andhydrolyzed the muscle proteins during fermentation.

Using LAB fermentation in combination with coagulase-negative Staphylococci (CNS), such as Staphylococcus

xylosus can contribute to the control of microbial safetyand quality (hurdle technology). LAB ensures the safety ofproducts by reducing the pH through fermentation ofsugars, while CNS influence other technological propertiesof fermented meat products. Many authors (Molly et al.,1997; Talon, Walter, Chartier, Barriere, & Montel, 1999)suggested that Staphylococcus spp., rather than LAB, couldhave a predominant effect on the characteristic flavor offermented sausages. In particular S. xylosus with itscatalase activity prevents rancidity (Barriere et al., 2001;Mauriello, Casaburi, Blaiotta, & Villani, 2004), andproteolytic and lipolytic activities contributing to thearoma of fermented sausages by the formation of estersand other aromatic compounds from amino acids(Johansson, Berdague, Larsson, Tran, & Borch, 1994;Montel, Reitz, Talon, Berdague, & Rousset-Akrim, 1996).That is why mixed cultures are widely used in manufactur-ing dry fermented sausages. However, little is known of themicrobiological and biochemical changes that occur infreshwater fish sausage fermentation inoculated with thecombination of LAB plus S. xylosus.

The main aim of this study was to determine the effect ofthe three groups mixed starter cultures on the character-ization of silver carp sausage during the manufacture.Quality parameters of fermented silver carp, which areTBARS, pH, water activity, microbial counts, TMA andTVB-N, were determined. In addition to these, proteolysischaracteristics and whiteness were also analyzed, whichmight provide further information on the characterization.

2. Materials and methods

2.1. Preparation of starter culture

Lactobacillus casei subsp. casei-1.001 and P. pentosaceus-

ATCC 33316 were purchased from China GeneralMicrobiological Culture Collection Center, Beijing; L.

plantarum-15, and S. xylosus-12 were obtained from theTechnology Center of the Shuanghui Group (a leadingmeat-processing company in China). The LAB wasseparately subcultured twice in DeMan Rogosa Sharpe(MRS) broth (Difco, Detroit, MI, USA) at 30 1C for 2

days. Cell pellets were harvested by high-speed refrigeratedcentrifuge (Model HSC-20RA, Tuman, Jilin, China) at10,000g for 15min at 4 1C and washed with 20mmol/l KCl-phosphate buffer, pH 7.0 and then the cell pellets wereresuspended in the same buffer. S. xylosus-12 wassubcultured twice in Nutrient Broth at 30 1C for 3 dayseach time. Cells were harvested by centrifugation at 2000g

for 15min at 4 1C, washed with saline water (0.9% NaCl)and then resuspended in saline water. Finally, the numberof bacterial cells in each suspension was adjusted to reachthe range of 7–8 logCFU/ml of saline solution by using aspectrophotometer (Model WFZ-UV-2100, Unico TM,Shanghai, China) (Fadda, Vignolo, Holgado, & Oliver,1998).

2.2. Silver carp sausage preparation

Frozen silver carp (2.5–3 kg/fish), purchased from a localmarket (Wuxi, Jiangsu, China), was thawed in running tapwater and then gutted, eviscerated, deboned, removed thescale, skin, pin bones, debris, and filleted. Silver carp filletswere minced through a deboner (Model 694, New Bedford,MA, USA) with a drum having 5mm-diameter perfora-tions. The processed samples were then mixed with 1volume of sterile water, 3% NaCl, 3% glucose. Startercultures were inoculated to a final level of 6–7 logCFU/gfish mince and well mixed using a sterile glass rod. Threeseparated batches were prepared with different mixedstarter cultures that are S-PXP (L. plantarum-15,S. xylosus-12, and P. pentosaceus-ATCC 33316 [1:1:1]);S-PXC (L. plantarum-15, S. xylosus-12 and L. casei

subsp. casei-1.001 [1:1:1]), S-XCP (S. xylosus-12, L. casei

subsp. casei-1.001 and P. pentosaceus-ATCC33316 [1:1:1])and a batch without any starter (NS) as control wereprepared. Each sausage batters was stuffed into collagencasings (+38mm, RL2, Naturin, Weinheim, Germany)with a filling machine (SZ-200, Guangzhou, China) andfermented at 30 1C, RH 85% for 48 h. Samples were takenevery 12 h for analysis.

2.3. Microbiological analyses

Silver carp sausage samples (25 g) were asepticallytransferred to a sterile plastic bag and pummeled for1min in a Stomacher (IUL Instrument, Barcelona, Spain)with 225ml 0.1% peptone water. Appropriate decimaldilutions of the samples were prepared using the samediluent and 0.1ml of each dilution was plated in triplicateon different growth media (Table 1). Results wereexpressed as colony forming units per gram (logCFU/g).

2.4. Proximate chemical analyses

The water activity (Aw) was carried out by using a digitalwater activity meter (Rotronic Hygroskop DT, Zurich,Switzerland) after equilibrium at 25 1C. Protein contentswere determined by the Kjeldahl Method (AOAC, 2002).

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Table 1

Media and incubation conditions of testing microorganism

Media Microflora Conditions for incubation Source

PCA Agar Total aerobic bacteria 37 1C for 48 h Plate Count Agar (Oxoid, CM325 )

MRS Agar Lactic acid bacteria 37 1C for 48 h Man Rogosa Sharpe (Oxoid, CM361 )

VRBD Agar Enterobacteriaceae 37 1C for 48 h Violet-Red-Bile-Dextrose-Agar (Oxoid, CM485)

MS Agar Staphylococcus 30 1C for 72 h Mannitol Salt Agar (BD Difco)

GSP Agar Pseudomonas 26 1C for 72 h Pseudomonas-Aeromonas-Selective-Agar-Base (Merck, Nr 10230)

YM Agar Yeasts and molds 25 1C for 96 h Yeast Malt Agar (BD Difco)

Y. Hu et al. / LWT 41 (2008) 730–738732

the crude fat content was determined by a Soxhletextraction apparatus using the solvent diethyl etheranhydrous (40–50 bp) (AR, Shanghai, China) (AOAC,2002).

2.5. Determination of pH and titratable acidity (TA)

pH measurements were done according to the procedureof Wang (2000). Ten gram samples were homogenized with90ml deionized water and the pH was measured with adigital pH meter (Mettler Toledo 320-s, Shanghai, China).Titratable acidity (TA) expressed as percent lactic acidwere determined according to the method described byIkenebomeh (1989).

2.6. Determination of weight loss

Weight loss was determined as described by Nakao et al.(1991). A sample with casing (100 g) was accuratelyweighed before fermentation using an analytical balance(ESJ120-4, Fuzhou, China). During the manufacture,sample was taken and then reweighed. Difference in weightof sausage before and after fermentation was referred to asweight loss.

2.7. Determination of TVB-N, TMA contents and TBARS

TVB-N and TMA contents were determined by themicro-diffusion method of Conway (Cobb & Thompson,1973).

TBARS was determined according to the method ofBuege and Aust (1978). A sample (5 g) was homogenizedwith 25ml of TBARS solution (0.375% TBA, 15% TCA,and 0.25N HCl). The mixture was heated for 10min inboiling water (95–100 1C) to develop a pink color. Then themixture was cooled with running water and centrifuged at5500g for 25min. The absorbance of the supernatant wasmeasured at 532 nm using a spectrophotometer (Model 135WFZ-UV-2100, UNICOTM, Shanghai, China). TheTBARS value was calculated from the standard curve ofmalonaldehyde and expressed as mg malonaldehyde/kgsample.

2.8. Sodium dodecyl sulfate polyacrylamide gel

electrophoresis (SDS-PAGE)

The water-soluble proteins were isolated by homogeniz-ing 10 g of mince with 90ml chilled distilled water andcentrifuging at 5000g for 20min. The supernatant was usedto determinate the water soluble muscle proteins. The salt-soluble proteins were isolated by homogenizing 10 g ofmince with 90ml 0.6M NaCl-phosphate buffer (pH 7.2).After 20min centrifugation at 5000g, the supernatant wascollected and used as the salt soluble muscle proteins.SDS-PAGE was done using a vertical gel electrophoresis

unit (Mini-Protean-3 Cell. Bio-Rad, Richmond, CA, USA)according to the methods of Laemmli (1970) and a runninggels containing 10% T (acrylamide plus bisacrylamide),and a stacking gel containing 4% T (0.125mol/l Tris, pH6.8). Aliquots of 15 ml were injected in each well includingstandard markers. Electrophoresis was done at 100–120V.After electrophoresis was completed, gels were stained at25 1C, using Coomassie Brilliant Blue R-250 (0.1%) anddestained with a solution of aqueous methanol (methano-l:acetic acid:water ¼ 1:1:8) until a clear background wasobtained. A high molecular weight (HMW) calibration kits(Pharmacia, BD, Sigma) (myosin [200 kDa], calmodulin[160 kDa], galactosidase [116 kDa], phosphorylase-b[97.4 kDa], serum albumin [66.2 kDa], actin [43 kDa],arbonicanhydrase [29 kDa], trypsin inhibitor [25 kDa] andlactalbumin [14.2 kDa]) were used as protein markers.

2.9. Color evaluation

The color of the samples was measured as the L�; a�; b�

values of CIE using a color meter (Model TC-Pa G, Beijingoptical Instruments Factory, Beijing, China). L�, a� and b�

indicate lightness, redness/greenness and yellowness/blueness,respectively. Whiteness was calculated using the followingequation (Lanier, Hart, & Martin, 1991):

Whiteness ¼ 100� ½ð100� L�Þ2 þ ða�Þ2 þ ðb�Þ2�1=2.

2.10. Statistical analyses

Duncan’s multiple range test was employed to determinethe significance of difference within treatments for eachtreatment. Three replicates were performed and the mean

ARTICLE IN PRESSY. Hu et al. / LWT 41 (2008) 730–738 733

values were calculated. Values were considered significantlydifferent when Po0.05. Date were analyzed for degree ofvariation and significance of difference using an analysis ofvariance (ANOVA) (Ramsey & Schafer, 1997). Allstatistical analyses were performed using SPSS statisticprogram (Version 11.0 for windows, SPSS Inc., Chicago,USA, 2001).

3. Results and discussion

3.1. Microbiological analyses

The initial total aerobic plate count (APC) in the sausagebatter was in the range of 3.7–4.7 logCFU/g. However,during 48 h fermentation at 30 1C, the batches with addedcultures significantly increased (Po0.05) to the level ofhigh logCFU/g after 36 h fermentation and then started tostabilize or decline during later stages (Table 2). It isseemed likely that the higher acidity and bacteriocinproduced by starters could have suppressive action againstthe growth of APC in the end product (Yin et al., 2002).

LAB counts increased during fermentation for both thecontrol and starters added samples (Table 2). Initial LABcounts in the starter cultures added samples were

Table 2

Microbiological changes in silver carp sausage during fermentation

Microorganisms Sample� Ferment time (h)

0 12

Aerobic bacteria NS 3.7870.22 6.717S-PXC 4.6870.15 7.627S-PXP 4.4270.20 7.327S-XCP 4.6270.12 7.627

LAB NS 4.1170.14a 6.437S-PXC 6.0670.13b 7.227S-PXP 6.1270.10b 7.047S-XCP 5.8670.13b 7.127

Enterobacteriaceae NS 2.5670.11 5.827S-PXC 2.3670.12 2.767S-PXP 2.1870.11 2.317S-XCP 2.3670.13 2.767

Micrococaceae NS 4.2170.18a 5.527S-PXC 6.2170.21b 7.687S-PXP 6.3170.21b 7.427S-XCP 6.3570.24b 6.897

Pseudomonas NS 3.5670.22 5.667S-PXC 3.2170.28 3.447S-PXP 3.2870.20 3.167S-XCP 3.3670.22 3.687

Yeasts and molds NS 1.5670.12 4.257S-PXC 1.3670.12 2.567S-PXP 1.4470.11 2.787S-XCP 1.3270.14 2.667

�NS: no starter added; S-PXP: L. plantarum-15, S. xylosus-12 and P. pento

and L. casei subsp. casei-1.001 mixed culture; S-XCP: S. xylosus-12, L. casei sa–cValues with unlike superscript letters in the same column are significantly

significantly higher than in the control samples (Po0.05)due to the inoculation of starter strains. During 36 hfermentation, LAB numbers increased and reached levelsup to 9.2 logCFU/g of sausage in all batches of sausageinoculated with mixed starters, which indicated that silvercarp is suitable for the growth of LAB. In contrast, thecontrol samples LAB increased more slowly, LAB countsincreased to 7.32 logCFU/g during 36 h. Likewise, theinitial counts for Micrococcaceae among samples rangedfrom 4 to 7 logCFU/g, increasing with starters addition.The counts of Micrococcaceae were significantly increasedin the batches inoculated with mixed starters to a level of7–8 logCFU/g at 12 h, thereafter, the counts decreasedsignificantly in all batches except the control (Table 2).Several authors have reported that the acidification andanaerobic conditions inhibited the growth of Micrococca-

ceae during ripening of fermented sausages (Hugas &Monfort, 1997; Aksu & Kaya, 2004).

Enterobacteriaceae and Pseudomonas counts of sausageswith or without starters were between 2.1 and 3.6 logCFU/gat the beginning of fermentation; no differences betweenbatches were observed. After 48 h of fermentation, thesausages inoculated with starter cultures significantlyinhibited the growth of Enterobacteriaceae and Pseudomonas

24 36 48

0.18a 7.5870.22a 8.7970.20a 8.9270.16a

0.16b 9.1270.23b 9.7670.14b 9.4270.13b

0.18b 9.2470.17b 9.5870.15b 9.2870.19b

0.14b 9.3470.16b 9.8870.14b 9.6870.20b

0.16a 6.8870.20a 7.3270.18a 7.3870.21a

0.12b 9.2270.16b 9.6470.14b 9.4270.24b

0.22b 9.4670.16b 9.7870.13b 9.6270.19b

0.16b 9.0270.20b 9.3470.18b 9.2270.18b

0.18a 8.1270.23a 8.6670.20a 8.1370.24a

0.21b 2.8870.16b 3.2870.14b 2.5670.20b

0.17b 2.5270.12b 2.7870.12b 2.1270.14b

0.12b 2.8870.11b 3.2870.18c 2.5670.20c

0.11a 5.7870.21a 6.8870.25a 7.2170.22a

0.25b 7.4370.17b 7.0270.22b 6.8870.13b

0.19b 7.2670.21b 7.1670.14b 6.6570.20b

0.17b 7.1670.14b 7.1270.20b 6.4270.17b

0.20a 7.6570.25a 8.1370.31a 8.5870.22a

0.15b 3.6270.22b 2.6670.20b 1.6870.15b

0.19b 3.4370.17b 2.4470.24b 1.9870.14b

0.24b 3.8870.20b 2.9670.22b 2.2270.17b

0.20a 6.6870.17a 6.7270.24a 6.9070.19a

0.18b 4.2670.20b 2.3370.16b 1.3270.14b

0.15b 4.0370.13b 2.1370.18b 1.0170.18b

0.21b 4.3270.16b 2.6270.11b 1.6870.14b

saceus-ATCC33316 mixed culture; S-PXC: L. plantarum-15, S. xylosus-12

ubsp. casei-1.001 and P. pentosaceus-ATCC33316 mixed culture.

different (Po0.05).

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Table 3

Proximate chemical composition of fermented silver carp sausages

Parameter Sample�

BF NS S-PXP S-PXC S-XCP

Moisture (g/100 g) 78.6870.69a 77.4270.09c 78.1670.10b 78.1270.12b 78.3270.10ab

Protein (g/100 g DM) 31.201470.20a 24.2470.20b 23.5670.20c 22.6870.32c 22.7270.42c

Fat (g/100 g DM) 5.6470.31 5.2670.20 5.2870.10 5.3470.15 5.2670.10

Ash (g/100 g DM) 1.2170.02 1.2170.01 1.2070.01 1.1970.02 1.2070.01

NaCl (g/100 g DM) 1.5570.01 1.6270.01 1.4670.02 1.5270.01 1.5070.01

DM ¼ dry matter.�BF: before fermentation; NS: no starter added; S-PXP: L. plantrum-15, S. xylosus-12 and P. pentosaceus-ATCC33316 mixed culture; S-PXC: L.

plantrum-15, S. xylosus-12 and L. casei subsp. casei-1.001 mixed culture; S-XCP: S. xylosus-12, L. casei subsp. casei-1.001 and P. pentosaceus-ATCC33316

mixed culture.a–cValues with different superscript letters in the same row are significantly different (Po0.05).

0 12 24 36 48

0.825

0.850

0.875

0.900

0.925

0.950

0

1

2

3

4

5

6

7

8

Weig

ht lo

sses (

g/1

00g)

Aw

Fermentation time (h)

Fig. 1. Changes in Aw and weight losses in silver carp sausage with/

without starters during fermentation (NS O; S-PXC K; S-PXP&; S-XCP

’). NS: no starter added; S-PXP: L. plantarum-15, S. xylosus-12 and P.

pentosaceus-ATCC33316 mixed culture; S-PXC: L. plantarum-15, S.

xylosus-12 and L. casei subsp. casei-1.001 mixed culture; S-XCP: S.

xylosus-12, L. casei subsp. casei-1.001 and P. pentosaceus-ATCC33316

mixed culture.

Y. Hu et al. / LWT 41 (2008) 730–738734

(Table 2). Our result was agreement with the result ofAryanta et al. (1991) who reported that Enterobacteriaceae

counts were significantly decreased with starter culturesadded to Turkish Soudjoucks (a fermented meat product)after fermentation. This result was also similar to thatobtained by with LAB fermented mackerel (Yin et al.2002). The yeast and mold counts increased in the batchesinoculated with mixed starters to a level of 4.0–4.5 logCFU/g at 24 h, thereafter, the counts decreased signifi-cantly (Po0.05) with processing time to 1–2 logCFU/g. Incontrast, the control showed higher (Po0.05) counts ofyeasts and molds in final products (Table 2).

3.2. Proximate chemical composition, Aw, weight losses,

and WHC

No significant differences (P40.05) were seen for fat,ash and salt content among all batches of sausages (Table3). However, moisture content was significantly (Po0.05)lower in the control resulting in a higher protein content.Initially, the Aw for sausages was 0.91, which decreasedsignificantly (Po0.05) with fermentation to a final range of0.82–0.89. Mixed starter culture batches showed a slightlyhigher Aw than the control (Fig. 1). Weight lossessignificantly increased with processing time and reachedto maximum of 7.78% in the control. In contrast, silvercarp sausages inoculated with mixed starter culturesshowed a lower weight losses than the control (Fig. 1).

3.3. pH value and TA

As fermentation time increased, silver carp sausagesinoculated with mixed starter showed a lower pH than thecontrol (Fig. 2). The pH gradually decreased to 4.24, 4.31,and 4.40 within 48 h for S-PXP, S-PXC and S-XCP,respectively. The pH values for all batches of silver carpsausages inoculated with mixed starters were not signifi-cantly different (P40.05). Since fermented sausage isnormally eaten uncooked to eat, it is recommended thatsilver carp sausage with pH lower than 4.4 is safe forconsumption (Paukatong & Kunawasen, 2001), i.e., free of

pathogenic microorganisms that natural contaminants insilver carp. The samples without a starter decreased slightlythe first during the 12 h of fermentation and then increasedgradually to 7.2. The pH rose in the control was probablydue to the formation of TVB-N (Table 4). An appreciableincrease in TA was noted in the silver carp sausagesinoculated mixed starter cultures after 24 h of fermenta-tion. At the end of 48 h fermentation, TA in the samplesinoculated starters increased from 0.28% to 5.98%, whileTA declined from 0.3% to 0.24% in the control.

3.4. Lipid oxidation

The highly unsaturated lipids in fat-rich fish are easilysusceptible to oxidation that results in a rancid smell andtaste as well as alterations in texture, color and nutritional

ARTICLE IN PRESSY. Hu et al. / LWT 41 (2008) 730–738 735

value (Olafsdottir et al., 1997). TBARS value is a widelyused indicator for the assessment of degree of lipidoxidation. It has been suggested that a maximum TBARSvalue, indicating the good quality of the fish, is 5mgmalonaldehyde/kg (Sikorski, Kolakowska, & Burt, 1990).In the present study, the initial TBARS values ranged in0.16–0.18mg of MDA/kg in samples. After 48 h fermenta-tion, the control sample had the highest TBARS value(1.46mg MDA/kg), whereas starter S-PXP inoculatedsausages had the lowest (1.05mg MDA/kg) (Fig. 3). Sincethe LAB, particularly P. pentosaceus-ATCC33316 and S.

xylosus-12 showed their antioxidant effects on unsaturatedfatty acids, the TBARS values for products added withsuch organisms could be definitely lower than the TBARSvalues found in the control. This result also confirmed theresult of Talon, Walter, and Montel (2000), who have beenreported that the antioxidant action of starter P. pentosa-

ceus in lipid oxidation.

0 12 24 36 480

1

2

3

4

5

6

7

8

9

10

11

12

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

pH

Titra

tab

le a

cid

ity (

%)

Fermentation time (h)

Fig. 2. Changes in TA and pH in silver carp sausage with/without starters

during fermentation (NS O; S-PXC K; S-PXP &; S-XCP ’). NS: no

starter added; S-PXP: L. plantarum-15, S. xylosus-12 and P. pentosaceus-

ATCC33316 mixed culture; S-PXC: L. plantarum-15, S. xylosus-12 and L.

casei subsp. casei-1.001 mixed culture; S-XCP: S. xylosus-12, L. casei

subsp. casei-1.001 and P. pentosaceus-ATCC33316 mixed culture.

Table 4

Changes in TMA and TVB-N in silver carp sausages during fermentation

FT� (h) TMA (mg/100 g)

NS�� S-PXP S-PXC S-XCP

0 0.8670.02 0.8670.01 0.8570.02 0.8670.02

12 0.9870.02 0.9370.04 0.9170.02 0.9370.02

24 1.3870.03a 0.9970.05b 1.0670.03b 1.1070.03

36 4.2270.04a 1.7670.06b 1.8270.03b 1.8870.02

48 10.1670.06a 2.6270.04b 2.7870.02b 2.8670.04

�FT: fermentation time.��Refer to the footnote of Table 1.a–cValues with unlike superscript letters in the same row are significantly di

3.5. TMA, TVB-N, and proteolysis

TVB-N and TMA are directly related to the microbialspoilage in various species of fish during their processingand storage (Dalgaard, 2000). The changes in TMAcontent in the fermented silver carp sausages and thecontrol are shown in Table 4. The initial TMA valueranged from 0.85 to 0.86mg/100 g muscle, which thenincreased very slowly during the first 24 h of fermentation,reaching low values of 1.38, 0.99, 1.06, and 1.10mg/100 gfor each of the control, S-PXP, S-PXC, and S-XCPsamples, respectively. By the 36 h of fermentation andthereafter, the TMA value of control samples increasedrapidly, attaining 10.16mg/100 g by the end of thefermentation (48 h), whereas significantly (Po0.05) lowervalues of 2.62, 2.78, and 2.86mg/100 g sausages weredetected for the samples fermented with S-PXP, S-PXC, S-XCP, respectively. Formation of TMA in the fish muscle is

TVB-N(mg/100 g)

NS S-PXP S-PXC S-XCP

1.170.22 1.1470.11 1.1170.12 1.1270.11

9.5470.06a 1.2970.22b 1.2470.31b 1.2970.16b

b 16.3570.32a 1.8870.18b 1.8970.13b 1.9370.42b

b 38.6670.26a 3.2470.55b 3.6470.32b 3.7570.43b

b 56.7170.19a 5.7870.32b 5.0170.48b 5.9270.71b

fferent (Po0.05).

0 12 24 36 480.0

0.5

1.0

1.5

2.0

2.5T

BA

RS

(m

g o

f m

alo

nd

iald

eh

yd

e/k

g)

Fermentation time (h)

Fig. 3. Changes in TBARS in silver carp sausage with/without starters

during fermentation (NS O; S-PXC K; S-PXP &; S-XCP ’). NS: no

starter added; S-PXP: L. plantarum-15, S. xylosus-12 and P. pentosaceus-

ATCC33316 mixed culture; S-PXC: L. plantarum-15, S. xylosus-12 and L.

casei subsp. casei-1.001 mixed culture; S-XCP: S. xylosus-12, L. casei

subsp. casei-1.001 and P. pentosaceus-ATCC33316 mixed culture.

ARTICLE IN PRESS

Fig. 4. Changes in SDS-PAGE profile of salt-soluble protein (A) and water-soluble protein (B) in fermented silver carp sausages. (S: protein markers, BF:

before fermentation, NS: no starter added; S-PXP: L. plantarum-15, S. xylosus-12 and P. pentosaceus-ATCC33316 mixed cultures; S-PXC: L. plantarum-

15, S. xylosus-12 and L. casei subsp. casei-1.001 mixed cultures; S-XCP: S. xylosus-12, L. casei subsp. casei-1.001 and P. pentosaceus-ATCC33316 mixed

cultures).

Y. Hu et al. / LWT 41 (2008) 730–738736

mainly by the bacterial action on the TMAO content andthe presence of specific spoilage organisms in the fish(Huss, 1988). Mixed starters cultures treated samplesshowed relatively lower amount of TMA values than inthe control. The decrease in pH inhibits the growth ofcontaminant microorganisms present in the raw materials,which suppress the accumulation of TMA.

The initial TVB-N values were in the range of1.11–1.14mg/100 g, which significantly increased withprocessing time and reached to maximum of 56.71mg/

100 g in the control (Table 4). In contrast, only slightincrease in the TVB-N values was observed in the silvercarp sausages inoculated with mixed starter cultures. Thisresult agreed to the result of Yin et al. (2002), who reportedthat the use of LAB in meat fermentation could inhibit theaccumulation of TVB-N by producing lactic acid andbacteriocins, which could neutralize the TVB-N or inhibitthe growth of spoilage bacteria and pathogens.Salt and water soluble proteins were noticeably degraded

during fermentation of silver carp muscle and the intensity

ARTICLE IN PRESS

Table 5

Hunter color analysis for silver carp sausages

Parameter Sample��

BF NS S-PXP S-PXC S-XCP

L* 38.7870.56a 44.6870.45b 63.2871.02c 63.6471.12c 65.4271.26c

a* �2.1170.11a �1.1270.12b �0.5770.22c �0.5070.12c �1.3970.18c

b* 7.8670.48a 9.770.78b 15.8070.36c 15.6270.40c 15.2270.18c

Whiteness 38.2871.66 43.8370.96a 60.0271.16b 60.4271.04b 62.2070.68b

��Refer to the footnote of Table 3.a–cValues with different superscript letters in the same row are significantly different (Po0.05).

Y. Hu et al. / LWT 41 (2008) 730–738 737

of proteolysis was more intense in the mixed culture addedsamples (Fig. 4). Compared with the samples before thefermentation and the control, the bands at 200, 160, 116,and 105 kDa molecular weight for the salt soluble proteinsdisappeared as a result of fermentation and the intensity ofthe band at 70 kDa for the water soluble proteins markedlydecreased. The bands 66, 26, 22, and 14 kDa appeared tobe more intense during fermentation. These results for thedegradation were very similar to the results of Hugheset al.(2002) for semi-dry fermented sausages, where starterculture had a more pronounced effect on protein degrada-tion than the control without starters. These phenomenasuggested that the proteolysis occurred rapidly duringfermentation because of the action of proteinases from S.

xylosus or LAB as well as the hydrolysis of muscle proteinscaused by acid (Astiasaran, Villanueva, & Bello, 1990).

3.6. Color

Table 5 shows the effects of mixed starter cultures on theHunter L�, a�, b� values and the texture profile for fourdifferent batches of fermented sausage. The Hunter L* andwhiteness of samples with starter cultures were significantlyhigher than those without starter and those beforefermentation (L�: increased from 38.78 to 63.28 to 65.42,whiteness: from 38.28% to 60.02% to 62.20%, Po0.05).However, the Hunter a� value of those samples withstarters was significantly lower than that without starterand that before fermentation (Po0.05). Hashimoto andWatabe (1988), and Ochiai, Chow, Watabe, and Hashi-moto (1988) ascribed the increase in Hunter L of frozentuna meat to the decrease in water holding capacity, whichmight be due to the hydrolysis of muscle proteins oraggregation of myofibrillar proteins during frozen storage.In this study, the decrease in Hunter a� and the increase inHunter L� and whiteness might be due to the hydrolysis ofwater-soluble and salt-soluble proteins (Yin et al., 2002)and pigment proteins, which consequently make thefermented products more transparent and much whiter.The whiter color of Som-fug, an indigenous fermented fishmince of Thailand, was reported to contribute to consumeracceptability (Riebroy, Benjakul, Visessanguan, Kijron-grojana, & Tanaka, 2004).

4. Conclusions

Using the combinations of LAB along with S. xylosus

could substantially inhibit the accumulation of TVB-N andTMA, suppress the growth of the main microflora presentin the raw materials, and hydrolyze the muscle proteins anddecreased lipid oxidation during fermentation. In addition,sausages with mixed starter cultures added had lowerTBARS values, which indicating less lipid oxidation. Theseresults suggest the high potential in using mixed startercultures in the fermented fish products and developingnovel fish food products.

References

Aksu, M. I., & Kaya, M. (2004). Effect of usage Urtica dioica L. on

microbiological properties of sucuk, a Turkish dry-fermented sausage.

Food Control, 15(8), 591–595.

AOAC. (2002). Official methods of analysis (17th ed.). Arlington, VA,

USA: Association of Official Analytical Chemists.

Aryanta, R. W., Fleet, G. H., & Buckle, K. A. (1991). The occurrence and

growth of microorganisms during the fermentation of fish sausage.

International Journal of Food Microbiology, 13(2), 143–155.

Astiasaran, I., Villanueva, R., & Bello, J. (1990). Analysis of proteolysis

and protein insolubility during the manufacture of some varieties of

dry sausage. Meat Science, 28, 111–117.

Barriere, C., Centeno, D., Lebert, A., Leroy-Setrin, S., Berdague, J. L., &

Talon, R. (2001). Roles of superoxide dismutase and catalase of

Staphylococcus xylosus in the inhibition of linoleic acid oxidation.

FEMS Microbiology Letters, 201(2), 181–185.

Buege, J. A., & Aust, S. D. (1978). Microsomal lipid peroxidation.

Methods in Enzymology, 52, 302–304.

Cobb, G. F. A. I., & Thompson, C. A. (1973). Biochemical and microbial

studies on shrimp: Volatile nitrogen and amino acid analysis. Journal

of Food Science, 38(3), 431–437.

Cooke, R. D., Twiddy, D. R., & Alan Reilly, P. J. (1987). Lactic-acid

fermentation as a low-cost means of food preservation in tropical

countries. FEMS Microbiology Letters, 46(3), 369–379.

Dalgaard, P. (2000). Fresh and lightly preserved seafood. In C. M. D.

Man, & A. A. Jones (Eds.), Shelf-life evaluation of foods (2nd ed.,

pp. 110–139). Gaithersburg, MD, USA: Aspen Publishing Inc.

Fadda, S., Vignolo, G., Holgado, A. P. R., & Oliver, G. (1998).

Proteolytic activity of Lactobacillus strains isolated from dryfermented

sausages on muscle sarcoplasmic proteins. Meat Science, 49(1), 11–18.

Gelman, A., Drabkin, V., & Glatman, L. (2000). Evaluation of lactic acid

bacteria, isolated from lightly preserved fish products, as starter

cultures for new fish-based food products. Innovative Food Science and

Emerging Technologies, 1(3), 219–226.

ARTICLE IN PRESSY. Hu et al. / LWT 41 (2008) 730–738738

Hashimoto, K., & Watabe, S. (1988). Changes in color and water holding

capacity of tuna meat during frozen storage. Nippon Suisan Gakkaishi,

49(6), 639–648.

Hugas, M., & Monfort, J. M. (1997). Bacterial starter cultures for meat

fermentation. Food Chemistry, 59(4), 547–554.

Hughes, M. C., Kerry, J. P., Arendt, E. K., Kenneally, P. M., McSweeney,

P. L. H., & O’Neill, E. E. (2002). Characterization of proteolysis

during the ripening of semi-dry fermented sausages. Meat Science,

62(2), 205–216.

Huss, H. H. (1988). Fresh Fish—Quality and Quality Changes FAO

Fisheries Series No. 29. Rome: FAO Danish International Develop-

ment Agency.

Ikenebomeh, M. J. (1989). The influence of salt and temperature on the

natural fermentation of African locust bean. International Journal of

Food Microbiology, 8, 133–139.

Johansson, G., Berdague, J. L., Larsson, M., Tran, N., & Borch, E.

(1994). Lipolysis, proteolysis and formation of volatile components

during ripening of a fermented sausage with Pediococcus pentosaceus and

Staphylococcus xylosus as starter cultures. Meat Science, 38(2), 203–218.

Kim, C. R., & Hearnsberger, J. O. (1994). Gram negative bacteria

inhibition by lactic acid culture and food preservatives on catfish fillets

during refrigerated storage. Journal of Food Science, 59(3), 513–516.

Laemmli, U. (1970). Cleavage of structural proteins during the assembly

of the head of bacteriophage T4. Nature, 227, 680–685.

Lanier, TC., Hart, K., & Martin, R. E. (Eds.). (1991). A manual of

standard methods for measuring, specifying the properties of surimi.

Washington, DC: National Fisheries Institute.

Mauriello, G., Casaburi, A., Blaiotta, G., & Villani, F. (2004). Isolation

and technological properties of coagulase negative staphylococci from

fermented sausages of Southern Italy. Meat Science, 67(1), 149–158.

Molly, K., Demeyer, D., Johansson, G., Raemaekers, M., Ghistelinck,

M., & Geenen, I. (1997). The importance of meat enzymes in ripening

and flavour generation in dry fermented sausages. First results of a

European project. Food Chemistry, 59(4), 539–545.

Montel, M. C., Reitz, J., Talon, R., Berdague, J. L., & Rousset-Akrim, S.

(1996). Biochemical activities of Micrococcaceae and their effects on

the aromatic profiles and odours of a dry sausage model. Food

Microbiology, 13(6), 489–499.

Nakao, Y., Konno, A., Taguchi, T., Tawada, T., Kasai, H., Toda, J., et al.

(1991). Curdlan: properties and application to foods 776. Journal of

Food Science, 56, 769–772.

Ochiai, Y., Chow, C. J., Watabe, S., & Hashimoto, K. (1988). Evaluation

of tuna meat discoloration by color difference scale. Nippon Suisan

Gakkaishi, 54(4), 649–653.

Olafsdottir, G., Martinsdottir, E., Oehlenschlager, J., Dalgaard, P.,

Jensen, B., Undeland, I., et al. (1997). Methods to evaluate fish

freshness in research and industry. Trends in Food Science and

Technology, 8, 258–265.

Paludan-Muller, C., Madsen, M., Sophanodora, P., Gram, L., & Moller,

P. L. (2002). Fermentation and microflora of plaa-som, a Thai

fermented fish product prepared with different salt concentrations.

International Journal of Food Microbiology, 73(1), 61–70.

Palumbo, S. A., Smith, J. L., Marmer, B. S., Zaika, L. L., Bhaduri, S.,

Turner-Jones, C., et al. (1993). Thermal destruction of Listeria

monocytogenes during liver sausage processing. Food Microbiology,

10(3), 243–247.

Paukatong, K. V., & Kunawasen, S. (2001). Hazard analysis and critical

control points (HACCP) generic model for the production of Thai

fermented pork sausage (Nham). Berl Munch Tierarztl Wochenschr,

114, 327–330.

Ramsey, F. L., & Schafer, D. W. (1997). The statistical sleuth: a course in

methods of data analysis. Belmont: Duxbury Press.

Riebroy, S., Benjakul, S., Visessanguan, W., Kijrongrojana, K., &

Tanaka, M. (2004). Some characteristics of commercial Som-fug

produced in Thailand. Food Chemistry, 88, 527–535.

Sikorski, Z. E., Kolakowska, A., & Burt, J. R. (1990). Postharvest

biochemical and microbial changes. In Seafood resources nutritional

composition and preservation (pp. 55–76). Boca Raton, FL, USA:

CRC.

Talon, R., Walter, D., Chartier, S., Barriere, C., & Montel, M. C. (1999).

Effect of nitrate and incubation conditions on the production of

catalase and nitrate reductase by staphylococci. International Journal of

Food Microbiology, 52(1–2), 47–56.

Talon, R., Walter, D., & Montel, M. C. (2000). Growth and effect of

staphylococci and lactic acid bacteria on unsaturated free fatty acids.

Meat Science, 54, 41–47.

Wang, F. S. (2000). Effects of three preservative agents on the shelf life of

vacuum packaged Chinese-style sausage stored at 20 1C. Meat Science,

56(1), 67–71.

Yin, L. J., Pan, C. L., & Jiang, S. T. (2002). Effect of lactic acid bacterial

fermentation on the characteristics of minced mackerel. Journal of

Food Science, 67(2), 786–792.