Influence of aging treatment on the bacterial quality of South African springbok (Antidorcas marsupialis marsupialis) wholesale cuts

ELSEVIER

International

Journal

of Food

Short

Microbiology

36 ( 1997)

23 l-234

communication

Influence of aging treatment on the bacterial quality of South African springbok (Antidorcas marsupialis marsupialis) wholesale cuts

Kecelved

30 December

1996; received

in revised

form

17 January

1997; accepted

24 January

1997

Abstract The left sides of 20 springbok carcasses were aged with the hkin on (treatment I ), while the right sides were aped without the skin (treatment 2). Another 20 carcasses were skinned, halved and cut into wholesale cuts. The loin and leg cuts from the right sides were deboned before vacuum packaging (treatment 3), while the loin and leg cuts from the left sides were vacuum

packed

with the bone

in (treatment

4). All the carcass

sides

(36 h post mortem)

and vacuum

packed

cuts (36 h post

mortem) were aged for either 2, 5. 12 and 19 days respectively (IX. 0°C). The examined groups of bacteria indicate that, for an ageinp period of I2 days or less, vacuum packaging does not have an advantage over the hung in air method. However, when considering an extended aging period ( > I2 days) vacuum packaging ensures that spoilage bacteria are inhibited and that the Enrerobacteriaceae group of bacteria do not increase (ca. 0°C). while the result\ clearly show that this is not the case with the hung In air ageinp treatment5 (I and 2). 0 1997 El\evier Science BV Ke~rr~on~s:

Venison;

Apeinp;

Storage

life

1. Introduction

method of ageing (Smith et al., 1974; Ncwsome ct al., 1984). NortjC and Shaw (1989) concluded that ageing treatment can have considerable effects on the initial microbial population of the packaged retail meat cuts. The present study wau undertaken to determine the most effective way to age springbok meat in order to produce quality products to be marketed in South Africa and internationally. The aim of the study was to determine the influence of different ageing treat-

Although vacuum packaging of meat causes a shift in the microflora from a predominance of aerobic spoilage organisms to lactic acid bacteria, some researchers have suggested that vacuum packaging does not have an advantage over the conventional “Corresponding author. + 27 I2 6651.5.51. OlhX-l6O5/Y7/Rl7.00 P/I

SOl68-1605(97)01264-6

Tel.:

0

+ 27 I2 67291 I I / 6729347;

lYY7 Elsewer

Science

fax:

HV. All rights

reserved

ments on the microbiological characteristics springbok carcass sides and cuts.

2. Materials

of

and methods

2. I. Mrcrt Springbok rams (Atltidowcrs mrrr.wpiu~is mum supidi.v) obtained from the same geographical area (De Aar district. Northern-Cape Province. South Africa) were harvested by a professional culling team during 3 consecutive nights (ca. - 3 to + 2°C). The carcasses were bled ca. 2-5 min after being killed by shooting. and eviscerated in the veld ca. IO-30 min after bleeding. The carcasses were hung outside overnight (skin on, ca. ~ 2 to + 2°C) and transported (ca. 700 km) to the Meat Industry Centre (MIC) the following day (ca. 10°C). On arrival the carcasses were placed in a chiller (ca. 0 “C) overnight and the following morning (32-36 h post mortem, pH range 5.41-6.94) the carcasses were skinned. halved and packaged.

for either 2. 5. 12 and I9 days respectively (ca. 0 “C). After each respective ageing period five skin-on aged carcasses were skinned. These five carcass Gdes as well as five skin-off aged carcass sides were cut into wholesale cuts (loin and leg) and bacteriologically sampled. Five vacuum packed cuts from each ageing treatment (bone-in and withoutbone) were also bacteriologically monitored after each respective ageing period.

The springbok wholesale cuts were bacteriologically monitored. after each ageing period (2. 5. I2 or 19 days) usin? the excision technique. A measured area of I2 cm- was removed aseptically to a depth of ca. 5 mm from the upper surface of the sample. This was homogenised with a Colworth Stomacher 300 (N.T. Laboratories. South Africa) in a 100 ml ol one-quarter-strength Ringer diluent. Counts were obtained as follows: Aerobic mesophilic counts on Standard 1 nutrient agar (Std I : Merck, South Africa). incubated for 3 days at 25°C and MRS agar (De Man et al.. 1960, Oxoid) was used for determination of lactic acid bacteria (3 days at 30°C). P.crtrrlotrtot~~tsspp. were monitored on cetrimide fusidin ceporin agar (CFC) (Mead and Adams, 1977, Oxoid) incubated for 3 days at 25°C and DHL agar (Sakaraki et al.. 1960. Merck) was used to determine Enterobacteriaceae (3 days, 37°C).

A total of 40 carcasses were used during this trial. Twenty carcasses were aged hung in air and the other 20 carcasses were vacuum packaged. The left sides of 20 springbok carcasses were aged with the skin on (treatment 1). while the right sides were aged without the skin (treatment 2). The skin was removed from the right side of the carcass before it was sawn in half and the resulting skin then draped around the left sides. The 20 remaining (vacuum packaged) carcasses were skinned. halved and cut into wholesale cuts. namely: loin and leg. The cuts from the right sides were deboned before vacuum packaging (treatment 3). while the cuts from the left sides were vacuum packed with the bone in (treatment 4) (45 ml/m’/24 h atm at 23°C and 75% R.H.. Kholer Packaging, South Africa) with a Multivac (B.T. Enterprises, South Africa). All the carcass sides and vacuum packed cuts were placed in a chiller (ca. 0°C) for ageing.

3. Results and discussion

The 20 carcass sides (36 h post mortem) and vacuum packed cuts (36 h post mortem) were aged

The statistical analysis of all the examined groups of bacteria on the springbok leg samples indicated that the different ageing treatments ( t-4) did not differ significantly (P = 0.5390) from each other,

75 -._

Stcitis/ictrl

rmtthxis

The loin and leg data were analysed by analyses of variance to determine which factors: ageing meatment (skin-on = I. skin-off = 2. vacuuin packed bone-out = 3. vacuum packed bone-in = 4) or ageing period (3. 5, I2 or I9 days) and interaction between factors differed significantly regarding the initial microbial quality. Levels of P 5 0.05 were taken to be significant.

although the counts recorded at the different ageing periods did (days 2, 5, 12 and 19) (P = 0.0156). Although, the initial aerobic mesophilic counts (day 2) recorded for treatments 1 and 2 were lower (log 4 cm-‘) than those recorded for treatments 3 and 4 (log 6 cm-‘), these counts increased to reach significantly higher levels of log 7 cm-” after an ageing period of 19 days (Table 1). In contrast, the counts of treatments 3 and 4 decreased initially, but reached similar levels (log 6 cm-‘) to the initial count, on day 19. The pseudomonad counts recorded followed a similar trend to that of the aerobic mesophilic counts. The lactic acid bacteria counts of all four treatments increased during the ageing period to reach significantly higher levels of 5 log 5 cm-’ on day 19, although, the day 19 lactic acid bacteria counts for treatments 1 and 2 were 2 log units lower than the pseudomonad counts, while the respective counts for treatments 3 and 4 were similar (log 5 cm-‘). Although the Enterobacteriaceae counts recorded (treatments l-4) followed a similar trend to that of the aerobic mesophilic counts, treatments 1 and 2 recorded unacceptably high counts after 19 days ageing (2 log 5 cm-‘). The statistical analysis of all the groups of bacteria Table

I

Mean

bacteriological

or 19 days Ageing

counts

(log/cm’)

obtained

from

leg wholesale

monitored on the springbok loin samples was similar to that of the leg samples. Regarding the aerobic mesophilic counts, Table 2 clearly shows that while the initial counts of treatments 3 and 4 decreased to reach lower levels (log 7-5 cm-’ and log 7-6 cm-’ respectively) on day 19, the counts of treatments 1 and 2 steadily increased to reach higher levels at the end of the ageing period (log 2-7 cm-: and log O-6 m -’ respectively). The pseudomonad and Enterobacteriaceae counts reacted similarly to the aerobic mesophilic counts. Similarly to the leg wholesale cut the Enterobacteriaceae counts of treatments 1 and 2 also reached unacceptably high numbers at the end of the ageing period ( 2 log 5 cm-‘). Regarding all the examined groups of bacteria the results indicate that, for an ageing period of 12 days or less, vacuum packaging does not have an advantage over the hung in air method. NortjC and Shaw ( 1989) reported that beef carcasses aged for ca. 1 week either as hung carcasses or primal joints in vacuum packs gave a similar product. This trend was also described by Silliker et al. (1977) and Buys et al. ( 1993), who reported that at 7 days storage the differences between pork stored in air as compared with pork stored in modified atmospheres were trivial.

cut!, from

sprinzbok

carcasses

(32-36

h

povt rwrtrrrr) aged

for 2, 5 I2

(0°C)

treatment

Ageing

Total

Standard

Pseudo-

Standard

Lactic

Standard

Entero-

Standard

period

count

error

monads

error

acid

error

bacteriaceae

error

(day\)

(log

(lop

cKZ’)

cm

-I

bacteria

)

(log

cm

-)

(log cm-‘)

I

Day

2

3.1

0.98

I.31

0.82

I.21

0.74

0.53

Day

5

1.05

0.61

2.59

I.21

I.71

0.70

I .x2

I .2s

Day

12

4.77

0.34

4.14

0.21

3.30

0.85

3.07

0.86

Day

I9

7.20

0.29

7.04

0.33

4.92

0.49

5.61

0.23

Day

2

4.16

0.79

2.99

I .27

I.15

0.70

1.60

0.9x

Day

9

6.23

1.80

4.04

2.00

I.57

0.07

3.43

2.00

Day

12

2.44

0.62

I .97

0.81

0.78

0.78

2.60

0.66

Day

19

7.9-l

I .29

7.60

I.11

5.63

0.62

6.59

0.93

0.53

Day

2

6.36

I.31

6.22

0.99

2.41

0.62

3.32

I.86

Day

5

5.35

1.87

3.36

2.00

I .x7

0.77

2.13

1.46

Day

12

4.89

0.75

1.58

I .32

4.72

0.67

2.55

I.18

Day

19

6.12

0.51

5.53

0.79

5.57

0.35

3.90

0.64 0.62

Day

2

6.X9

I.56

5.46

I .67

1.79

0.73

2.48

Day

5

5.26

2.00

3.84

2.00

0.00

0.00

I .4s

0.88

Day

12

4.91

0.84

2.89

I.35

3.88

0.33

3.02

0.89

Day

19

6.S.1

I .06

5.31

0.58

5.13

1.33

3.34

I .04

Ageing

treatment

Ageiny

Total

Standard

Peudo-

Standard

Lactic

Standard

Entero-

Standard

period

Count

erro,-

monad

error

acid bacteria

error

bacteruccar

crrw

0.S~

(log Cl,,

?)

(log cm

?)

(103 cm

(day\)

(logcm

.SkiWO~l

Day 2

2.53

O.f>fI

0.70

0.70

(I? = -5)

Day 5

3.46

0.63

3.89

0.6X

I .w

I .07

Day 12

-1.43

0.G

5.70

0.52

-1.02

O.YO

Day 19

7.52

0.26

7.20

0.32

5.96

0.23

Ski,I-Off

Daq 2

0.00

0.00

I .5x

I .Oh

I .62

0.x I

(/I = 5)

Day 5

5.17

1.73

h. I8

2.00

I .Oh

0.78

Day 12

5.77

0.57

4.w

0.79

1.Xh

I .oo

Day 19

6.46

0.10

6.21

0. I2

1.75

0.38 I .67

(log cc’)

Vocxur~~ ptrc~hcd.

Day 2

7.19

I .6X

S.74

0.6X

I.91

horwout

Day 5

4.29

I.10

I.51

Day 12

5 .oo

I.51 3.95

I..51

(II = 5)

1.31 1.07

0.1 I

1.03

I .02

Day I9

5.90

0.21

4.6’)

l.IX

O.lS

0.75

Vtrcurtn~ /xrc~hrtl.

Day

2

7.37

I.53

S.XI

I .80

I .32

I Y-l

hoIlr~irl

Day 5

S.30

O.YS

I .S7

2.02

(II = S)

Day 12

3.07

0.17

5.05 ? ?7 -._-

0 0.3

3.7Y

I..59 0.15

Day I9

0.38

053

-1.51

1.3-1

5.3Y

I.31

However, when considering an extended ageing period ( > I2 days) vacuum packaging ensures that spoilage bacteria are inhibited and that the Enterobacteriaceae group of bacteria do not increase (CU. 0°C). while the results clearly show that this is not the case with the hung in air ageing treatments ( I and 2).

( I Yf)O) A

De Man. J.C., Kogosa. M. and Sharpr. M.E. the cultivation Mead.

G.C.

of Lactobncilli.

and Adams.

rapid Iwlation RI-. Poultry

?)

0.64

J. Appl. Bacttxiol.

B.W. (1977)

of P~rudomonad~

medium

Ibr

23. I X-135.

A elective

medium

associated with poultry

t’ol

meat.

SCI. 18. 661.

Ncwsonle.K.L.. Langlois. Fox. J.D. ( 19X-I) tffrct m~crohiolo,gcal

qualit)

B.E..

Moocly,

W.G.

Nelwn.

ti.

and

of time and method of apriq

on the

of beef loins and cot-respondin:r

atcal\\.

J. Food Protect. 17, 12% I25

Acknowledgments The authors wish to thank Mrs. D. from the Pretoria Technicon and Dr. for initiating this study; the FRD for study and J. Kriiger, R.P. Greebe and their technical assistance.

van Rensburg I.B. Zondagh financing this E. van Zyl for

Sakauhl.

R.. Nanolha.

hactrrlx

Japanese J. Med. 30. 13-X.

D.

J.H.. Woodruff.

dioxide

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