EFFECT OF EXTRACT OF GRAPEFRUIT SEEDS AND BAIKAL SKULLCAP ROOT ON CHEMICAL COMPOSITION AND SENSORY TRAITS OF FEMALE TURKEY MEAT

Elżbieta Rusinek-Prystupa¹, Krzysztof Szkucik², Ryszard K. Pisarski³, Michał Gondek^2
1 Department of Biochemistry and Toxicology, Faculty of Biology and Animal Breeding, University of Life Sciences in Lublin, Poland
² Department of Food Hygiene of Animal Origin, Faculty of Veterinary Medicine, University of Life Sciences in Lublin, Poland
³ Institute of Animal Nutrition and Bromatology Faculty of Biology and Animal Breeding, University of Life Sciences in Lublin, Poland

ABSTRACT

The objective of the research was to determine the effect of grapefruit seeds extract (Citrosept) and Baikal skullcap root on chemical composition and sensory attributes of turkey meat. The research material comprised pectoral, thigh and shank muscles of BIG 6 heavy-type female turkeys maintained from 6 till 15 week of age and fed standard complete pelleted diets. The turkey hens were assigned into control and 6 experimental groups, the latter ones had different doses of the studied preparations added to drinking water. The muscles of the left-side half carcass were examined for a content of crude ash, crude protein and ether extract, whereas the muscles in the right-side were evaluated for sensory characteristics, i.e. flavor intensity and desirability, tenderness and juiciness were assessed. The studies have shown that neither of the evaluated preparations changed significantly a content of protein and ether extract, the essential meat components – determinants of its nutritional and biological value. Only the maximum dose of grapefruit extract and skullcap extract (irrespective of a dose) has changed significantly the crude ash level in pectoral muscles. Alike, muscle tissue sensory characteristics were not positively modified through the investigated preparations, while their maximum doses decreased flavor intensity and desirability.

Key words: turkey hen meat, meat quality, feed additives, chemical and sensory analysis, nutritional value, antibiotic growth promoters.

INTRODUCTION

Since the usage of antibiotic growth promoters (AGP) was banned and consumer’s demand for so-called “healthy food” markedly increased, herbs and plant extracts have been included into animal diets and veterinary practice for therapeutic and prophylactic purposes more frequently [4, 5]. Implementation of herbal raw materials of appropriate botanical composition in animal feeding is a subject of extensive studies that analyze, among others, their impact of chemical composition of muscles, fatty acid profile and basic sensory attributes of meat [11, 23].

In light of the above, derivatives of grapefruit and Baikal skullcap commercially available as ready-to-use preparations appear to be very promising. Citrosept, i.e. grapefruit seed extract was examined for its antibacterial, antifungal and antiviral properties. It was recommended for prophylactic use as a flavonoid-rich food supplement. Flavonoids are among the most ubiquitous compounds and they show substantial biological activity [20]. Dried root of Scutellara baicalensis Georgi (Labiatae) is officially listed in the Chinese Pharmacopoeia. This perennial herb has been long used in the official and traditional medicine, mainly in Russia, Japan, Korea and Mongolia. Although less known in Poland, it grows well under our climate conditions. It is characterized by particularly high content of compounds that serve as modifiers of inflammatory processes, e.g protect against bacterial infections. Besides, they possess antiviral, anticancer, antioxidative and hepatoprotective properties [5, 6, 7]. These beneficial and very promising characteristics encouraged to undertake studies on potential influence of mentioned preparations on some traits of turkey meat which has increased in popularity among consumers.

The objective of the researches was to determine the effect of Citrosept preparation and Baikal skullcap root on chemical composition of muscle tissue and some sensory characteristics of turkey hen meat. Another aim was to establish the optimal dose of the preparations applied.

MATERIALS AND METHODS

The study was carried out in a farm in Nowy Uścimów included BIG 6 heavy-type slaughter turkey females raised from 6th till 15th week of age, housed in pens under litter management system. The turkeys were randomly allocated into 7 groups: control (K) and 6 experimental groups (C1, C2, C3, B1, B2, B3), 45 birds each. Each group consisted of 3 replications of 15 birds, raised in separate pens. The fattening of tested turkeys lasted 15 weeks. The control birds did not receive any experimental additives, while those from groups C1-C3 and B1-B3 obtained preparations added to drinking water, in accordance to the experimental design presented in Table 1. It should be noticed that both preparations are available as food additives in pharmacies as so called OTC (Over The Counter), and certainly they are standardized, which makes possible to repeat experimental conditions.

Table 1. Experimental design

Specification	Group
	K	C1	C2	C3	B1	B2	B3
Preparation	–	Grapefruit seed extract (Citrosept)			Baikal skullcap
Preparation dose [mL kg-1 b.w.]	0	0.011	0.021	0.042	0.009	0.018	0.036

The preparations under study were administered throughout the entire raising period, except for 10th and 11th weeks of age. The introduction of a two-week long break was due to the rules for the application of natural immunostimulating substances, as it was ascertained that better results are achieved for a discontinuous than continuous therapy. During the experiment, the turkey hens from all the groups were fed standard complete pelleted mixtures ad libitum (Tab. 2), accordingly to the Poultry Nutrition Standards [21] for 5-phase feeding program. The female turkeys were provided with constant veterinary supervision.

Table 2. Composition of mixtures [%] and their nutritive value

Component	Mixture and feeding period [weeks]
	Starter 2 (6.)	Grower 1 (7.-9.)	Grower 2 (10.-12.)	Grower 3 (13.-15.)
Protein – mineral concentrate	15.0	15.0	15.0	12.0
Wheat, ground	33.6	38.9	44.6	51.3
Corn, ground	20.0	20.0	20.0	20.0
Soybean meal, solvent	30.0	24.0	18.0	14.0
Vegetable oil	1.4	2.1	2.4	2.7
Nutritive value
Crude protein [%]	24.5	22.5	20.5	18.0
EM [kcal/kg]	2875	2980	3040	3130
Lysine [%]	1.56	1.42	1.28	1.09
Methionine [%]	0.60	0.57	0.54	0.50
Met. + Cyst. [%]	1.01	0.96	0.90	0.83
Threonine [%]	0.89	0.81	0.72	0.62
Tryptophan [%]	0.31	0.28	0.25	0.22
Ca [%]	1.25	1.15	1.10	0.99
P available [%]	0.63	0.63	0.59	0.56
Na [%]	0.16	0.16	0.16	0.15
Coccidiostat	+	+	+	–

On the last day of raising period, all the birds underwent 12h pre-slaughter fasting (with unlimited access to drinking water) and then were transported to poultry slaughter plant and slaughtered in accordance to the relevant technology [3]. After the 24-hour post slaughter period, the bird carcasses chilled to +4ºC were analyzed using the simplified dissection technique [2]. The left pectoral muscle, thigh and shank muscle were used for chemical analyses, whereas the muscles of the right-side carcass were evaluated for sensory characteristics. Chemical analyses were performed on three samples randomly collected from each replication of carcasses and five samples for sensory attributes.

Chemical analysis of meat included dry matter content determination with the drier method [13], crude ash content by incineration [15], crude protein using Kjeldahl method [12] and ether extract according to Soxhlet [14].

The sensory assessment in 5-point scale, with scores of half-point use, was performed by a team of six panelists of recognized high sensory acuity. The sensory evaluation test included determination of flavor (intensity and desirability), tenderness and juiciness. The panelists rate each sensory characteristics and the test scores plus the panelists overall impression (amplitude) make up the complete sensory assessment. Sample preparation for analysis and point-rated criteria were based on the guidelines available in literature and Polish Standards [9, 10, 16, 17, 22].

The obtained results were analyzed statistically using variance analysis, while the significance of differences between the control and the experimental groups were established on the grounds of Duncan confidence intervals.

RESULTS

Chemical composition of muscles
The effect of each preparation was analyzed as related to the control group results; no comparisons between the results obtained in the experimental groups were considered. None of preparations has changed significantly a content of dry matter and organic constituents in muscles (Tab. 3). The influence was noticeable only in the case of crude ash, i.e. the maximum dose of grapefruit extract and Baikal skullcap extract (irrespective of amount) increased significantly a content of minerals in the pectoral muscles (group C3, B1, B2 and B3 – 45.6, 35.9 and 34.8%, respectively). The analysis of thigh muscles showed that crude ash level grew substantially at the medium – (14.5%) and not maximum-dose administration, whereas the highest dosage produced the opposite response (-25.4%), alike the medium and maximum dose of skullcap (-18.2 and -10.0%).

Table 3. Chemical composition of turkey muscles [%]

Muscles	Group							SEM
	K	C1	C2	C3	B1	B2	B3
Dry matter
Pectoral	25.91	25.66b	26.17	27.38a	26.98	26.33	26.64	0.195
Thigh	25.56	26.26	25.22	26.24	25.37	25.47	26.03	0.136
Shank	23.70	23.66	23.74	24.91	23.32c	23.18A	25.18Bc	0.194
Crude protein
Pectoral	25.00	25.17	24.78	26.49	26.32	26.45	25.33	0.236
Thigh	20.82	21.47A	20.79	21.00	20.22B	19.92B	20.02B	0.129
Shank	20.40	21.31	21.30	21.23	20.42	20.54	21.10	0.136
Ether extract
Ppectoral	1.08	1.07	1.01A	1.06	1.14	1.25	1.35B	0.032
Thigh	5.36	5.82	4.52a	5.07	5.43	5.47	6.13	0.161
Shank	3.23	2.60	2.73	3.32	2.66	2.66	2.93	0.070
Crude ash
Pectoral	0.92Aa	1.14	1.10	1.34B	1.25B	1.19b	1.24B	0.031
Thigh	1.10a	1.04a	1.26b	0.93cd	1.07ae	0.90d	0.99de	0.024
Shank	0.89	0.85a	0.83a	0.95	0.88	0.99b	0.99b	0.017
a, b, ... – Means in lines denoted with small letters differ significantly at p ≤ 0.05. A, B  – Means in lines denoted with capital letters differ significantly at p ≤ 0.01.

Organoleptic evaluation of meat
Flavor intensity of breast meat of turkeys receiving the maximum dose of grapefruit extract was evaluated significantly higher than the intensity of meat flavor of the control birds (Tab. 4). The extract was found to affect significantly flavor desirability as, apart from its dose, it decreased the scores given to breast meat while in the case of shank meat, similar but not such considerable effect was observed for only the maximum extract dose applied.

Table 4. Sensory assessment of turkey hen meat [pts]

Muscles	Group							SEM
	K	C1	C2	C3	B1	B2	B3
Flavor – intensity
Pectoral	3.52A	3.43	3.32	3.27B	3.50	3.38A	3.23B	0.025
Thigh	3.52	3.45	3.40	3.32B	3.57A	3.42	3.37	0.023
Shank	3.37	3.30	3.32	3.32	3.50	3.42	3.33	0.028
Flavor – desirability
Pectoral	3.38A	2.95B	2.88B	2.67Bc	3.03Bd	3.00Bd	2.75B	0.046
Thigh	3.28A	3.30A	3.27A	2.97	3.07	2.83	2.63B	0.056
Shank	3.40a	3.17	3.03	2.92b	3.35	3.37	3.18	0.057
Tenderness
Ppectoral	4.72A	4.65	4.47	4.18B	4.52	4.45	4.33	0.048
Thigh	4.15	4.05	3.85	3.75	3.95	3.87	3.68	0.047
Shank	3.72	3.83	3.78	3.68	3.95	3.87	3.95	0.039
Juiciness
Pectoral	4.47ABa	4.43AB	4.52A	4.05BCb	3.93C	4.28ABC	4.33ABC	0.050
Thigh	3.80	3.85	3.88	3.73	3.98	3.87	3.85	0.032
Shank	3.77	3.87	3.75	3.83	3.85	3.85	3.93	0.040
Overall rating
Pectoral	4.62a	4.43	4.52	4.20b	4.18b	4.43	4.35	0.043
Thigh	3.83	4.07	3.82	3.78b	4.00	4.10a	3.85	0.037
Shank	3.77	3.72	3.72	3.88	3.90	3.93	3.98	0.044
a ,b, ... – Statistically significant differences in lines at p ≤ 0,05. A, B, ...–  Statistically significant differences in lines at p ≤ 0,01.

Meat tenderness appeared to be slightly sensitive to the grapefruit whose only maximum dose has significantly declined breast meat evaluation, yet it did not influence the thigh and shank meat whatsoever. Its impact on meat juiciness and consequently, the overall organoleptic assessment was similar.

The studies have shown the effect of Baikal skullcap as well. Flavor intensity of breast meat of turkey hens fed maximum dose of extract was rated significantly lower. Besides, the extract additive decreased the score for flavor desirability and notably, a growing dose tended to lower the ratings. It is noteworthy however, that the lowest skullcap dose (but not higher) had significant influence on meat juiciness and the total score.

DISCUSSION

One of the prior conditions for further development of poultry meat production is to ensure its high quality and this prerequisite must be met being the demand of both, consumers and poultry processing plants. According to the sensory evaluation the following attributes are prominent: appearance, color, palatability – overall impression of chiefly aroma and flavor and finally, texture with its major characteristics, i.e. tenderness and juiciness [18].

The organoleptic attributes of meat depend on, among others, feeding [19] and the effect of basic nutrients on poultry meat qualities has been thoroughly studied and recognized [22]. The current research is focused on feed additives, in particular those of natural origin, which are believed  to be beneficial not only for animal organism but human health as well.

The most important source of meat aroma are water-soluble small-molecule compounds [1, 8] and their level in the pectoral muscles must have been changed significantly under the influence of maximum dose of grapefruit extract and Baikal skullcap as well. However, the investigated preparations caused deterioration of desirable flavor of the breast muscles to a great extent. Leg muscles, though, turned out to be far less sensitive (only in the case of thigh muscles, the maximum dose of Baikal skullcap lowered flavor desirability, while the same amount of grapefruit extract produced similar effect in shank muscles).

Neither of the preparations under study has improved meat tenderness – the primary quality assessment criterion, on the contrary, in some cases significant deterioration was noted. Alike, juiciness evaluated on the basis of the amount of water released from the sample at its chewing, depending on tenderness, marbling content, aroma and flavor as well as the thermal treatment time and technique, was not improved [2]. As a consequence the total sensory evaluation was not positively modified through the studied preparations application, either.

The literature available for review indicates that the organoleptic parameters of poultry meat under Citrosept preparation additive have not been studied as yet, while only few papers addressing Baikal skullcap root extract [5] are not consistent with the findings in the present research.

Summing up, the studies have indicated that neither of the evaluated preparations changed significantly a content of protein and fat – the essential meat constituents – responsible for its nutritive value. Alike, the sensory attributes of muscle tissue were not positively modified by the discussed preparations, while their maximum doses were found to decrease flavor intensity and desirability.

REFERENCES

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Accepted for print: 13.02.2014

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Elżbieta Rusinek-Prystupa
Department of Biochemistry and Toxicology, Faculty of Biology and Animal Breeding, University of Life Sciences in Lublin, Poland
Akademicka 13 St.
20–950 Lublin, Poland

Krzysztof Szkucik
Department of Food Hygiene of Animal Origin, Faculty of Veterinary Medicine, University of Life Sciences in Lublin, Poland
Akademicka 12 St.
20–950 Lublin, Poland

Ryszard K. Pisarski
Institute of Animal Nutrition and Bromatology Faculty of Biology and Animal Breeding, University of Life Sciences in Lublin, Poland
Akademicka 13 St.
20–950 Lublin, Poland

Michał Gondek
Department of Food Hygiene of Animal Origin, Faculty of Veterinary Medicine, University of Life Sciences in Lublin, Poland
Akademicka 12 St.
20–950 Lublin, Poland

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