Article pp.124-127 du Vol.23 n°1 (2003)

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124-127 Sci. Aliments 23(1), 2003 I. Sebastián et al.

FOCUS : JSMTV

Colour image analysis for the classification of turkey breast meat according to cooking yield

I. Sebastián

¹

, V. Santé

²

, G. Le Pottier

¹

,

P. Marty-Mahé

³

, P. Loisel

³

, D. Brossard

³

, G. Monin

²

INTRODUCTION

The technological quality of breast meat is an increasingly critical factor for the production of processed turkey meat products. The cooking yield is a major quality feature for processed products such as cooked turkey breast ham. Coo- king yield is closely dependent upon the water holding capacity (WHC) of the meat. Water binding additives are not required for the process of meats with high WHC; their use, however, is made necessary to improve the cooking yield of meats with low WHC up to acceptable levels.

Colour is a potential indicator of the WHC and cooking yield of poultry meat.

Its measurement by image analysis is fast, non-invasive and compatible with the production constraints in meat processing plants. The objective of the present work is to evaluate the potential of colour image analysis for the classification of turkey breast muscles used for the production of turkey breast ham.

MATERIAL AND METHODS

One hundred and seventy turkey breast muscles were harvested in the same slaughterhouse on 4 different dates. The muscles were obtained from 15-week old male turkeys (line BUT 9) after conventional chilling over a minimum of 8 hours. The muscles were selected visually to obtain the largest range of colour, from lightest to darkest. The ultimate pH value (pHu), was determined 24 h post mortem using a portable pH meter equipped with a glass electrode

1. Comité Interprofessionnel de la Dinde française (CIDEF), 35310 Mordelles, France.

2. INRA, Station de Recherches sur la Viande, Theix, 63122 St-Genès -Champanelle, France.

3. CEMAGREF, 17, avenue de Cucillé, 35044 Rennes, France.

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Colour image analysis for the classification of turkey breast meat according to cooking yield 125

directly inserted into the muscle. A video colour image was obtained using a tri- CCD DXC 990 P SONY camera and was analysed according to the method developed by CEMAGREF. The results were expressed as L*, a*, b*, C* et h*

coordinates for lightness, redness, yellowness, chroma (C= (a*²+b*²)^1/2) and hue angle (h=arc tang (b*/a*)), respectively. The breasts were subsequently vacuum packaged, immediately frozen and stored at –20˚C for further analysis. After thawing, the cooking yield was measured on a muscle sample of standard size (15 _✕ 5 _✕ 2,5 cm; 337 ± 14 g, n=170) after injection of brine (136 g of nitrite salt

✕ l^-1) at the rate of 15%, vacuum packaging and cooking in a water bath until a 68˚C internal temperature was reached. The data were subjected to analysis of variance using the general linear model procedure of SAS, and the means were separated using the Scheffe's test.

RESULTS

The muscle samples were distributed in 4 groups according to their L* value obtained by image analysis: 45-48 (class 1), 49-52 (class 2), 53-56 (class 3), and 57-60 (class 4). The proportion of the total number of muscles studied for each class was 10, 39, 33 and 18%, respectively. As expected, the average cooking yield decreased as the L* value increased (or the muscles were lighter; Table 1).

Significant differences between mean pHu values according to the treatment were observed, with the exception of classes 1 and 2.

Table 1

Colour, pHu and cooking yield according to lightness (L* value) as measured by image analysis

Class of lightness

(limit values of L* by image analysis)

1 2 3 4 SEM Effect

(45-48) (49-52) (53-56) (57-60)

No. of muscles 18 66 56 30

Image analysis:

L* 47.7 ^a 51.3 ^b 55.3 ^c 58.2^d 1.1 ***

a * 19.5 ^a 19.4^a 17.7 ^b 17.4 ^b 1.28 ***

b* 9.2 â 9.8 â 10.1â 11.0 ^b 1.29 ***

C * 21.6 ^{a b} 21.8 ^a 20.5 ^b 20.7 ^b 1.63 ***

h * 0.44 ^a 0.47 ^a 0.52 ^b 0.57 ^c 0.04 ***

pHu 5.95 ^a 5.94 ^a 5.85 ^b 5.79 ^c 0.1 ***

Cooking yield (%) 93.7 ^a 92.6 ^a 90.5^b 89.2 ^b 2.76 ***

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126 Sci. Aliments 23(1), 2003 I. Sebastián et al.

In the present sampling conditions, lightness showed a bimodal distribution (Figure 1). The peaks were observed at L* values of 51 and 56, and one may assume that they consisted of populations of muscles of normal quality and deficient quality, respectively. Similarly, the distribution of cooking yields shows two populations with a transition at around 90% yield (Figure 2). When L*

exceeded the value of 55, there was a greater number of muscles with cooking yield ≥ 90% than those with cooking yield < 90%.

Figure 1

Distribution of lightness values (L*, image analysis)

Figure 2

Distribution of cooking yield 0

5 10 15 20 25 30

45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 L* (image analysis)

Number of samples Cooking yield < 90%

Cooking yield ≥ 90%

0 2 4 6 8 10 12 14 16 18

>96 94 92 90 88 86 84 82

Cooking yield (%) Frequency (% of muscles)

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Colour image analysis for the classification of turkey breast meat according to cooking yield 127

The result of a selection of muscles on the basis of a L* value greater than a limit value is presented in Table 2. The cooking yield showed a marked decrease with the increase in the L* value above 55. If this value is chosen as a threshold, 69% of the breast muscles would be selected, with an average cooking yield of 91.5%

Table 2

Selection among the breast muscles: percentage of muscles selected and corresponding average cooking yield (CY).

CONCLUSIONS

The results of this study showed that a relationship exists between the cooking yield of brine injected turkey breast muscles without water binding additive and the colour coordinates measured by image analysis. This method does not discriminate accurately the muscles according to their cooking yield. However, it allows to distri- bute the muscles in two groups with contrasting average processing qualities, to which the most appropriate technological treatments can be applied.

ACKNOWLEDGEMENTS

This work was financed by the OFIVAL (Office National Interprofessionnel des Viandes, de l'Elevage et de l’Aviculture).

L* limit value

% muscles Average CY Selected CY ≥ 90% (%)

<48 8.8 100.0 93.7

48 10.6 94.4 93.7

49 17.1 96.6 93.3

50 21.2 94.4 93.3

51 41.8 87.3 92.2

52 49.4 86.9 92.9

53 50.6 81.4 91.2

54 60.6 81.6 91.1

55 68.8 80.3 91.5

56 82.4 73.6 89.4

57 91.2 69.0 89.4

> 57 100.0 67.3 89.1