Research Note: Effect of packaging atmosphere on the fatty acid profile of intramuscular, subcutaneous fat, and odor of goose meat.

The aim of the study was to investigate changes of the fatty acid profile in the intramuscular and subcutaneous fat as well as odor sensory evaluation of goose packaged under different conditions of modified atmosphere (vacuum and high-oxygen modified atmosphere of 80% O2 and 20% CO2 composition) and stored under refrigeration (4°C) for 11 D. Packaging in a high-oxygen modified atmosphere had a negative impact on goose meat quality due to the reduction of polyunsaturated fatty acids (PUFA), PUFA/saturated fatty acids (SFA) and the increase of SFA, which means a substantial loss of its nutritional value. Goose meat can be stored for 11 D without changes in the fatty acid profile, provided that a vacuum is used that limits oxygen exposure. At the end of storage, a better sensory evaluation of the odor intensity in the vacuum-packed samples was also observed in comparison to high oxygen modified atmosphere. Vacuum packaging turned out to be a better method for preserving fatty acid profile and the odor of goose meat during 11 D of storage.

INTRODUCTION

Among the different meat species, goose supplies fat with one of the highest unsaturated/saturated fatty acids (SFA) ratios. However, the high percentage of unsaturated fatty acids (UFA) makes goose meat susceptible to oxidation, and off-odor may be formed during storage.

The production of goose meat in Poland is carried out mainly with the W-31 hybrids (♂♀), obtained as a result of cross-breeding a W-33 gander and a W-11 goose, i.e. based on the White Kołuda goose, which is characterised by good reproductive and meat ratios—e.g., high protein content and low lipid content, in which UFA constitute more than 70% of total content (Biesiada-Drzazga, 2014).

To increase the durability of food products, modified atmosphere packaging is used in the industry. Owing to the oxygen content in the modified atmosphere (MA), the packaging of high or low (including vacuum) oxygen content is distinguished. The high-oxygen MA (70% ÷ 80% O2, 20% ÷ 30% CO2) is commonly used in the food industry to preserve and even improve the red color of meat, especially for meat with high heme pigments content, including goose meat (Fernandes et al., 2014; Santos et al., 2015; Bonny et al., 2017). However, such atmospheric composition has limitations due to its oxidative activity. Poultry meat and particularly goose meat is susceptible to oxidation processes due to high content of UFA. In contrast, the maximum shelf life is achieved by an oxygen-free atmosphere, because in an anaerobic atmosphere increases meat oxidative stability (Alvarez et al., 2006; Seydim et al., 2006). Changes in fatty acid (FA) composition are essential indirect indicators of lipid oxidation in stored meat. Polyunsaturated fatty acids (PUFA) oxidation results in off-odor, off-flavors and reduction of food quality (Tao, 2015; Hęś, 2017). Particular importance for the nutritional value of edible fats lies in the composition of FA. Research shows that lauric acid (C12:0), myristic acid (C14:0), and palmitic acid (C16:0), which are SFA, raise blood cholesterol levels in low-density lipoproteins (LDL), increasing their coagulability, contributing to atherosclerosis and ischemic heart disease (WHO/FAO, 2008). Replacing products rich in SFA with foods containing PUFA lowers the concentration of cholesterol contained in LDL and the ratio of total cholesterol to cholesterol contained in the high-density lipoprotein (WHO/FAO, 2008), thereby reducing the risk of coronary heart disease (Williams and Salter, 2016).

The effect of modified atmosphere packaging on the FA profile from goose breast muscle lipids and subcutaneous fat has not been extensively studied. Therefore, the objective of the study was to evaluate changes in the FA profile of intramuscular and subcutaneous fat as well as odor sensory evaluation (SE) of goose packaged under different conditions of MA (vacuum and high-oxygen MA of 80% O2, 20% CO2 composition) during refrigerated (4°C) storage.

MATERIALS AND METHODS

Meat Preparation

Birds were kept in uniform conditions. Their rearing and fattening was organized in accordance with a prepared (Bieliński, 1983) and constantly improved rearing technology (Rosiński, 2000) to obtain a quality product termed as “the young Polish oats-fed goose”.

The research material was the breast muscle of the White Kołuda female goose (average weight about 0.5 kg) from industrial slaughter. Cuts after cooling and qualitative and weight classification were divided into culinary elements. Breast muscles with skin were individually packed in a slaughterhouse, using type R-230 Multivac packaging machine (Multivac, Germany) in polyamide-polyethylene foil (permeability: O2 = 25 cm3/m2·24h·0.1 MPa; CO2 = 85 cm3/ m2·24h·0.1 MPa; N2 = 7 cm3/m2·24h·0.1 MPa; water vapor < 3 g/m2·24 h) in a vacuum (99% vacuum is equal to 1.3 KPa) and a high-oxygen MA with a composition of 80% of O2 and 20% of CO2. Samples for experiments were chosen randomly.

Overall 250 goose breast muscles were tested—equal number of samples (100) were packed in vacuum and in a high-oxygen MAseparately. The control group comprised of 50 unpacked muscles, which were examined 24 h after the slaughter. Packed muscles were stored at 4°C in a refrigerator equipped with automatic temperature control and examined on the 4th, 7th, 9th, and 11th Dof storage (for each atmosphere 25 samples were used in the examination procedure). And as a result determinations were performed for each muscle.

Fatty Acids Analysis

Preliminary ground meat tissues (4.0 g) and subcutaneous fat (3.0 g) (removed from the breast muscle using knife) were homogenized with a model T 25 homogenizer (Ika Ultra-Turrax Corp.). Extraction of lipids was carried out according to the method described by Folch et al. (1956). The FA profiles were determined by the capillary gas chromatography technique. For the determination of FA composition the lipid samples were converted to their corresponding methyl esters by AOCS official method Ce 2–66 (AOCS,1997). The FA methyl esters were analyzed using an Agilent Tech. 7890 A series gas chromatograph (Agil. Tech. Inc., St. Clara, USA) equipped with a flame-ionization detector (FID) and a silica capillary column HP 88 J&W Scientific series–100 m × 0.25 mm × 0.20 µm film thickness (Agil. Tech. Inc., St. Clara, USA).

Helium was used as the carrier gas at a head pressure of 2.0 mL/min constant flow. Air, hydrogen and helium make-up gas flow rates by FID detector were: 450, 40, and 30 mL/min, respectively. The injector and detector were maintained at 250°C and 280°C, respectively. The chromatographic conditions were as follows: the initial column temperature of 120°C was held for 1 min, increased to 180°C at 10°C/min and held for 10 min. Finally, the column temperature was elevated to 230°C at a rate of 5°C/min, and maintained for 5 min. The quantification of FA methyl esters of muscle lipids was carried out using non-adecanoic acid (C 19:0) as an internal standard. The peaks were identified by comparing the retention times with those of a mixture of external standard methyl esters (Supelco 37 F.A.M.E. Mix C 4–C 24 Component). The FA content was calculated as percentage of a sum of FA with the ChemStation Agilent Technologies program (Agil. Tech. Inc., St. Clara, USA).

The proportions of SFA, monounsaturated fatty acid (MUFA) and PUFA were obtained from the sum of all the identified SFA, MUFA and PUFA, respectively, expressed as percentage of the total FA.

Sensory Evaluation

The SE of odor intensity of goose breast muscles and subcutaneous fat was carried out at the sensory laboratory with all requirements according to the international standard (ISO,1988). A trained, 7-member sensory panel participated in SE. A 6-point hedonic scale was used, 1 point meaning the lowest and 6 points the highest evaluation (criteria of a 6-point scale of the SE of odor intensity: 1–completely changed, putrid; 2–strongly changed; 3–slightly changed; 4–typical but less intense; 5–typical; and 6–ideal, typical. Surface odor intensity was assessed 30 min. after the pack was opened. A score < 3 was regarded as unacceptable. The intensity of the odor was expressed in conventional units (CU) (Stone et al.,1980).

Statistical Analysis

The data were performed with Statistica version 12.0 (StatSoft, Inc. 2012, Statistica software program). ANOVA was used to analyze differences between the type of packaging atmosphere and particular storage time within analyzed atmospheres. Post-hoc analysis was undertaken using Duncan's multiple range test at a 5% level of significance. Results were given as mean ± standard error of 5 independent determinations.

RESULTS AND DISCUSSION

The FA profile of intramuscular and subcutaneous goose fat is summarized respectively in Tables 1 and 2.

Table 1

Mean values (±standard error) of fatty acid profile (% of the total fatty acids) of goose meat packed in different atmospheres and stored at 4°C for up to 11 D.

Fatty acids	Packaging atmosphere	Storage time1 (D)					Significance effects
		0	4	7	9	11	PA	ST	PA × ST
SFA							***	***	***
	MA	29.66 ± 0.23a	30.13 ± 0.07b,x	31.14 ± 0.03c,x	31.56 ± 0.08d,x	33.11 ± 0.06e,x
	Vacuum	29.66 ± 0.23	29.59 ± 0.07y	29.5 ± 0.04y	29.68 ± 0.04y	29.65 ± 0.08y
C 12:0							ns	ns	ns
	MA	0.24 ± 0.01	0.24 ± 0.004	0.24 ± 0.006	0.23 ± 0.009	0.25 ± 0.004
	Vacuum	0.24 ± 0.01	0.23 ± 0.007	0.24 ± 0.004	0.22 ± 0.009	0.24 ± 0.002
C 14:0							***	***	***
	MA	0.78 ± 0.004a	0.87 ± 0.007b,x	0.93 ± 0.01c,x	0.95 ± 0.006c,d,x	0.96 ± 0.01d,x
	Vacuum	0.78 ± 0.004	0.78 ± 0.007y	0.79 ± 0.008y	0.77 ± 0.009y	0.79 ± 0.006y
C 15:0							***	***	***
	MA	0.23 ± 0.01a	0.26 ± 0.01a	0.34 ± 0.01b,x	0.50 ± 0.01c,x	0.67 ± 0.01d,x
	Vacuum	0.23 ± 0.01	0.24 ± 0.007	0.25 ± 0.006y	0.25 ± 0.006y	0.25 ± 0.006y
C 16:0							***	***	***
	MA	24.04 ± 0.21a	24.11 ± 0.08a	24.87 ± 0.01b,x	24.95 ± 0.03b,x	25.98 ± 0.02c,x
	Vacuum	24.04 ± 0.21	23.96 ± 0.05	23.94 ± 0.04y	24.00 ± 0.07y	23.96 ± 0.06y
C 17:0							ns	ns	ns
	MA	0.13 ± 0.006	0.13 ± 0.006	0.12 ± 0.009	0.12 ± 0.007	0.12 ± 0.006
	Vacuum	0.13 ± 0.006	0.13 ± 0.005	0.13 ± 0.004	0.13 ± 0.004	0.13 ± 0.004
C 18:0							***	***	***
	MA	4.24 ± 0.10a	4.53 ± 0.03b,x	4.63 ± 0.03b,x	4.83 ± 0.08c,x	5.14 ± 0.05d,x
	Vacuum	4.24 ± 0.10	4.25 ± 0.03y	4.31 ± 0.03y	4.31 ± 0.08y	4.30 ± 0.003y
MUFA							***	***	***
	MA	42.89 ± 0.16a	44.11 ± 0.07b,x	44.37 ± 0.06b,x	45.13 ± 0.07c,x	45.55 ± 0.12c,x
	Vacuum	42.89 ± 0.16	42.91 ± 0.26y	43.20 ± 0.28y	42.98 ± 0.18y	42.95 ± 0.09y
C 16:1							*	ns	ns
	MA	3.89 ± 0.25a	3.95 ± 0.10a	4.12 ± 0.05a,b	4.31 ± 0.08a,b	4.41 ± 0.09b,x
	Vacuum	3.89 ± 0.25	3.93 ± 0.07	4.03 ± 0.07	4.01 ± 0.07	3.88 ± 0.10y
C 17:1							***	***	***
	MA	0.06 ± 0.000a	0.07 ± 0.004a,b	0.08 ± 0.004b,c,x	0.09 ± 0.004c,d,x	0.10 ± 0.002d,x
	Vacuum	0.06 ± 0.000	0.07 ± 0.004	0.07 ± 0.005y	0.06 ± 0.002y	0.07 ± 0.004y
C 18:1							***	***	***
	MA	38.8 ± 0.14a	39.92 ± 0.14b,x	39,99 ± 0.07b,x	40.54 ± 0.11c,x	40.84 ± 0.07c,x
	Vacuum	38.8 ± 0.14	38.79 ± 0.25y	38.94 ± 0.27y	38.74 ± 0.15y	38.86 ± 0.11y
C 20:1							***	***	***
	MA	0.16 ± 0.004a	0.18 ± 0.004b,x	0.19 ± 0.004b,c,x	0.20 ± 0.008c,x	0.20 ± 0.002c,x
	Vacuum	0.16 ± 0.004	0.15 ± 0.004y	0.16 ± 0.004y	0.17 ± 0.006y	0.15 ± 0.004y
PUFA							***	***	***
	MA	25.90 ± 0.13a	24.64 ± 0.23b,x	23.19 ± 0.10c,x	21.39 ± 0.09d,x	20.10 ± 0.22e,x
	Vacuum	25.90 ± 0.13	25.85 ± 0.15y	25.77 ± 0.14y	25.86 ± 0.08y	26.00 ± 0.04y
C 18:2n-6							***	***	***
	MA	18.92 ± 0.02a	18.01 ± 0.07b,x	17.47 ± 0.07c,x	16.19 ± 0.06d,x	15.17 ± 0.14e,x
	Vacuum	18.92 ± 0.02	18.86 ± 0.05y	18.73 ± 0.06y	18.82 ± 0.04y	18.88 ± 0.05y
C 18:3n-3							***	***	***
	MA	1.76 ± 0.04a	1.58 ± 0.02b,x	1.48 ± 0.02c,x	1.44 ± 0.02c,x	1.30 ± 0.04d,x
	Vacuum	1.76 ± 0.04	1.78 ± 0.01y	1.78 ± 0.03y	1.76 ± 0.02y	1.79 ± 0.03y
C 20:2n-6							***	***	***
	MA	0.13 ± 0.002a	0.10 ± 0.004b,x	0.10 ± 0.005b,x	0.08 ± 0.004c,x	0.07 ± 0.004c,x
	Vacuum	0.13 ± 0.002	0.13 ± 0.007y	0.13 ± 0.007y	0.13 ± 0.006y	0.12 ± 0.002y
C 20:3n-6							***	***	***
	MA	0.23 ± 0.006a	0.22 ± 0.007a	0.19 ± 0.004b,x	0.19 ± 0.006b,x	0.16 ± 0.002c,x
	Vacuum	0.23 ± 0.006	0.24 ± 0.004	0.22 ± 0.008y	0.23 ± 0.004y	0.22 ± 0.008y
C 20:4n-6							***	***	***
	MA	4.46 ± 0.12a	4.39 ± 0.15a	3.68 ± 0.03b,x	3.29 ± 0.07c,x	3.21 ± 0.03c,x
	Vacuum	4.46 ± 0.12	4.45 ± 0.09	4.49 ± 0.11y	4.51 ± 0.07y	4.58 ± 0.04y
C 20:5n-3							***	***	***
	MA	0.14 ± 0.01a	0.10 ± 0.006b,x	0.06 ± 0.008c,x	0.05 ± 0.004c,x	0.05 ± 0.004c,x
	Vacuum	0.14 ± 0.01	0.14 ± 0.01y	0.14 ± 0.009y	0.14 ± 0.01y	0.14 ± 0.009y
C 22:6n-3							***	***	***
	MA	0.28 ± 0.01a	0.25 ± 0.009a	0.21 ± 0.008b,x	0.16 ± 0.007c,x	0.14 ± 0.008c,x
	Vacuum	0.28 ± 0.01	0.26 ± 0.01	0.28 ± 0.009y	0.27 ± 0.01y	0.25 ± 0.008y
Σ UFA							***	***	***
	MA	68.78 ± 0.27a	68.75 ± 0.28a	67.58 ± 0.10b,x	66.50 ± 0.08c,x	65.65 ± 0.27d,x
	Vacuum	68.78 ± 0.27	68.76 ± 0.36	68.57 ± 0.26y	68.84 ± 0.17y	68.93 ± 0.06y
PUFA/SFA							***	***	***
	MA	0.88 ± 0.01a	0.82 ± 0.006b,x	0.75 ± 0.004c,x	0.68 ± 0.004d,x	0.61 ± 0.007e,x
	Vacuum	0.88 ± 0.01	0.87 ± 0.005y	0.87 ± 0.005y	0.87 ± 0.003y	0.88 ± 0.001y
n-6							***	***	***
	MA	23.73 ± 0.11a	22.72 ± 0.22b,x	21.45 ± 0.09c,x	19.75 ± 0.08d,x	18.61 ± 0.18e,x
	Vacuum	23.73 ± 0.11	23.67 ± 0.12y	23.57 ± 0.12y	23.69 ± 0.06y	23.80 ± 0.02y
n-3							***	***	***
	MA	2.17 ± 0.03a	1.93 ± 0.02b,x	1.75 ± 0.03c,x	1.64 ± 0.03d,x	1.50 ± 0.04e,x
	Vacuum	2.17 ± 0.03	2.18 ± 0.02y	2.20 ± 0.03y	2.17 ± 0.01y	2.17 ± 0.03y
n-6/n-3							***	**	***
	MA	10.92 ± 0.12a	11.80 ± 0.09b,x	12.29 ± 0.25b,c,x	12.03 ± 0.22b,c,x	12.47 ± 0.30c,x
	Vacuum	10.92 ± 0.12	10.86 ± 0.07y	10.74 ± 0.13y	10.91 ± 0.05y	10.96 ± 0.16y

The data are average values of 50 tests for storage time 0; 25 tests for storage time 4, 7, 9, 11 D.

Means with different letters in the same row, differ at P < 0.05 in view of the time of storage.

Means with different letters in the same column, differ at P < 0.05 in view of the packaging atmosphere.

Significance effects: *P < 0.05; **P < 0.01; ***P < 0.001; ns—not significant.

PA: packaging atmosphere, ST: storage time, MA: modified atmosphere (80% O2 and 20% CO2), SFA: saturated fatty acid, UFA: unsaturated fatty acid, MUFA: monounsaturated fatty acid, PUFA: polyunsaturated fatty acid.

Table 2

Mean values (±standard error) of fatty acid profile (% of the total fatty acids) of subcutaneous goose fat packed in different atmospheres and stored at 4°C for up to 11 D.

Fatty acids	Packaging atmosphere	Storage time1 (d)					Significance effects
		0	4	7	9	11	PA	ST	PA ×ST
SFA
	MA	28.80 ± 0.31a	29.34 ± 0.05a	30.53 ± 0.10b,x	31.16 ± 0.02c,x	31.56 ± 0.10c,x	***	***	***
	Vacuum	28.80 ± 0.31	28.86 ± 0.13	28.86 ± 0.08y	28.85 ± 0.08y	28.85 ± 0.12y
C 12:0							***	***	***
	MA	0.21 ± 0.005a	0.24 ± 0.002a	0.27 ± 0.004b,x	0.31 ± 0.006c,x	0.37 ± 0.008d,x
	Vacuum	0.21 ± 0.005	0.22 ± 0.007	0.21 ± 0.005y	0.23 ± 0.006y	0.22 ± 0.008y
C 14:0							***	***	***
	MA	0.67 ± 0.005a	0.81 ± 0.007b,x	0.89 ± 0.009c,x	1.06 ± 0.009d,x	1.16 ± 0.01e,x
	Vacuum	0.67 ± 0.005	0.69 ± 0.004y	0.71 ± 0.008y	0.70 ± 0.008y	0.70 ± 0.009y
C 15:0							***	***	***
	MA	0.32 ± 0.006a	0.35 ± 0.006a	0.45 ± 0.009b,x	0.48 ± 0.007c,x	0.55 ± 0.01d,x
	Vacuum	0.32 ± 0.006	0.33 ± 0.009	0.33 ± 0.009y	0.32 ± 0.009y	0.31 ± 0.008y
C 16:0							***	***	***
	MA	22.20 ± 0.11a	22.43 ± 0.01a	23.20 ± 0.09b,x	23.50 ± 0.03b,c,x	23.62 ± 0.08c,x
	Vacuum	22.20 ± 0.11	22.24 ± 0.09	22.21 ± 0.07y	22.23 ± 0.09y	22.20 ± 0.09y
C 17:0							ns	ns	ns
	MA	0.11 ± 0.004	0.12 ± 0.006	0.11 ± 0.000	0.11 ± 0.000	0.11 ± 0.003
	Vacuum	0.11 ± 0.004	0.10 ± 0.004	0.12 ± 0.008	0.10 ± 0.007	0.11 ± 0.009
C 18:0							***	***	***
	MA	5.29 ± 0.01a	5.41 ± 0.01b,x	5.62 ± 0.009b,x	5.71 ± 0.01b,x	5.76 ± 0.01d,x
	Vacuum	5.29 ± 0.01	5.27 ± 0.01y	5.29 ± 0.01y	5.28 ± 0.01y	5.31 ± 0.01y
MUFA							***	***	***
	MA	50.41 ± 0.29a	51.33 ± 0.24a,b,x	51.95 ± 0.07b,x	53.00 ± 0.03c,x	53.99 ± 0.06d,x
	Vacuum	50.41 ± 0.29	50.62 ± 0.08y	50.50 ± 0.19y	50.93 ± 0.15y	50.75 ± 0.13y
C 16:1							***	***	***
	MA	3.39 ± 0.11a	3.78 ± 0.06b,x	4.14 ± 0.08c,x	4.39 ± 0.07c,d,x	4.60 ± 0.05d,x
	Vacuum	3.39 ± 0.11	3.41 ± 0.11y	3.45 ± 0.06y	3.47 ± 0.07y	3.39 ± 0.07y
C 17:1							***	***	***
	MA	0.05 ± 0.000a	0.06 ± 0.000b,x	0.07 ± 0.000b,x	0.08 ± 0.000c,x	0.09 ± 0.000d,x
	Vacuum	0.05 ± 0.000	0.05 ± 0.000y	0.05 ± 0.000y	0.05 ± 0.000y	0.05 ± 0.000y
C 18:1							***	***	***
	MA	46.8 ± 0.18a	47.32 ± 0.19a,b	47.52 ± 0.02b,x	48.62 ± 0.08c,x	49.04 ± 0.02d,x
	Vacuum	46.8 ± 0.18	46.99 ± 0.08	46.83 ± 0.13y	47.23 ± 0.13y	47.14 ± 0.16y
C 20:1							***	***	***
	MA	0.17 ± 0.000a	0.19 ± 0.000b,x	0.22 ± 0.000c,x	0.25 ± 0.001d,x	0.25 ± 0.001d,x
	Vacuum	0.17 ± 0.000	0.17 ± 0.000	0.17 ± 0.000	0.17 ± 0.000y	0.17 ± 0.000y
PUFA							***	***	***
	MA	19.34 ± 0.42a	18.20 ± 0.20b,x	17.03 ± 0.19c,x	15.50 ± 0.18d,x	13.72 ± 0.31e,x
	Vacuum	19.34 ± 0.42	19.28 ± 0.23y	19.60 ± 0.21y	19.15 ± 0.22y	19.28 ± 0.21y
C 18:2n-6							***	***	***
	MA	17.32 ± 0.19a	16.45 ± 0.17b,x	15.53 ± 0.17c,x	14.22 ± 0.14d,x	12.61 ± 0.20e,x
	Vacuum	17.32 ± 0.19	17.40 ± 0.11y	17.40 ± 0.09y	17.48 ± 0.20y	17.29 ± 0.18y
C 18:3n-3							***	***	***
	MA	1.56 ± 0.02a	1.41 ± 0.03b,x	1.23 ± 0.02c,x	0.83 ± 0.03d,x	0.80 ± 0.03e,x
	Vacuum	1.56 ± 0.02	1.53 ± 0.02y	1.54 ± 0.02y	1.49 ± 0.02y	1.53 ± 0.02y
C 20:4n-6							***	***	***
	MA	0.28 ± 0.000a	0.21 ± 0.000b,x	0.17 ± 0.000c,x	0.16 ± 0.000d,x	0.09 ± 0.000e,x
	Vacuum	0.28 ± 0.000	0.30 ± 0.000y	0.30 ± 0.000y	0.29 ± 0.000y	0.30 ± 0.000y
C 20:5n-3							***	***	***
	MA	0.18 ± 0.000a	0.13 ± 0.000b,x	0.11 ± 0.000c,x	0.07 ± 0.000d,x	0.04 ± 0.000e,x
	Vacuum	0.18 ± 0.000	0.18 ± 0.000y	0.19 ± 0.000y	0.18 ± 0.000y	0.18 ± 0.000y
Σ UFA							***	ns	**
	MA	69.75 ± 0.26a	69.53 ± 0.44a,b	68.99 ± 0.25a,b	68.50 ± 0.14b,c,x	67.72 ± 0.40c,x
	Vacuum	69.75 ± 0.26	69.90 ± 0.30	70.10 ± 0.40	70.08 ± 0.35y	70.03 ± 0.39y
PUFA/SFA							***	***	***
	MA	0.67 ± 0.01a	0.62 ± 0.007b,x	0.56 ± 0.007c,x	0.50 ± 0.005d,x	0.43 ± 0.01e,x
	Vacuum	0.67 ± 0.01	0.67 ± 0.007y	0.68 ± 0.007y	0.66 ± 0.006y	0.67 ± 0.01y
n-6							***	***	***
	MA	17.6 ± 0.35a	16.66 ± 0.17b,x	15.70 ± 0.17c,x	14.38 ± 0.14d,x	12.69 ± 0.20e,x
	Vacuum	17.6 ± 0.35	17.62 ± 0.21y	17.83 ± 0.19y	17.50 ± 0.21y	17.52 ± 0.18y
n-3							***	***	***
	MA	1.74 ± 0.08a	1.55 ± 0.03b	1.34 ± 0.02c,x	1.12 ± 0.03d,x	0.83 ± 0.04e,x
	Vacuum	1.74 ± 0.08	1.66 ± 0.02	1.76 ± 0.02y	1.66 ± 0.02y	1.76 ± 0.02y
n-6/n-3							***	***	***
	MA	10.11 ± 0.28a	10.79 ± 0.14a	11.75 ± 0.19b,x	12.92 ± 0.28c,x	15.36 ± 0.50d,x
	Vacuum	10.11 ± 0.28	10.62 ± 0.12	10.11 ± 0.07y	10.54 ± 0.13y	9.95 ± 0.07y

The data are average values of 50 tests for storage time 0; 25 tests for storage time 4, 7, 9, 11 D.

Means with different letters in the same row, differ at P < 0.05 in view of the time of storage.

Means with different letters in the same column, differ at P < 0.05 in view of the packaging atmosphere.

Significance effects: *P < 0.05; **P < 0.01; ***P < 0.001; ns—not significant.

PA: packaging atmosphere, ST: storage time, MA: modified atmosphere, 80% O2 and 20% CO2; SFA: saturated fatty acid, UFA: unsaturated fatty acid, MUFA: monounsaturated fatty acid, PUFA: polyunsaturated fatty acid.

It has been determined that the type of atmosphere during storage influenced the FA profile of intramuscular and subcutaneous goose fat. But in the experiment described there was neither any change in the FA profile in samples packed in vacuum nor any difference in the proportion of SFA, MUFA, and PUFA in muscle lipids and subcutaneous fat throughout the whole storage time. In case of lipid samples packed in oxygen atmosphere, a decrease of PUFA and an increase of SFA and MUFA was noticed. Up to the 11th storage day the percent of SFA increased gradually in lipids samples packed in MA, mainly due to increased palmitic (C16:0) and stearic (C18:0) acids. The increase in SFA during storage in samples packed in MA could probably result from the degradation of PUFA, which generated low molecular weight compounds and possibly short chain FA.

Likewise the MUFA percentage rose gradually up to the 11th D due to increase in oleic (C18:1) and palmitoleic (C16:1) acids. Unfavorable in terms of nutrition was the lowering, in comparison to unpacked samples, the percentage of PUFA in both intramuscular and subcutaneous goose fat, due to the reduction of all types of PUFA individually. On the 11th D, the percentage of linoleic (C18:2), linolenic (C18:3), eicosadienoic (C20:2), eicosatrienoic (C20:3), arachidonic (C20:4), eicosapentaenoic (C20:5), and docosahexaenoic (C22:6) acid in intramuscular fat had fallen, in comparison to unpacked samples, respectively by: 19.82, 26.14, 46.15, 30.43, 28.03, 64.29, and 50.00% (Table 1); in case of subcutaneous fat the percentage of linoleic, linolenic, arachidonic, and eicosapentaenoic acid had lowered, in comparison to control samples, respectively by: 27.19, 48.72, 67.86 and 77.78% (Table 2).

The ratio of PUFA to saturated ones is an important indicator of fat quality, and its recommended dietary allowance should be higher than 0.40 (Simopoulos, 2003). It was demonstrated that the PUFA/SFA ratio did not change during sample storage in vacuum, but decreased in fat packaged in MA (Table 1; Table 2). Therefore, from the point of view of human nutritional, both the intramuscular fat and the subcutaneous fat of goose packaged in vacuum have a better PUFA/SFA ratio than those packaged in a high-oxygen modified atmosphere and stored in refrigerated conditions.

The n-6/n-3 ratio is a useful indicator of the food's nutritional value. Ideally, this should be less than 4 to 5:1 (Geldenhuys et al., 2013), but in practice it is usually more than 20:1 (Simopoulos, 2003, 2008; Farrell 2013; Materac et al., 2013) due to over-consumption of n-6 FA and foods containing SFA. In the human body this imbalance n-6/n-3 ratio can lead to, e.g., cancer or cardiovascular disease (Simopoulos, 2008). At the end of the storage period, higher n-6/n-3 ratio was reported in samples packaged in MA, as compared to those packaged in vacuum (Tables 1 and 2). Although the n-6/n-3 ratio in intramuscular and subcutaneous fat, regardless of the type of atmosphere, was higher than the recommended value, it was clearly lower than in the typical diet of most developed countries. It has been shown that the packaging of goose meat in vacuum is a better method to protect the FA profile of both intramuscular fat and subcutaneous fat.

Packaging method had a significant effect on the SE of odor intensity in the goose meat and subcutaneous fat (Table 3). The odor of the unpacked breast muscles and subcutaneous fat was found to be ideal, characteristic for chilled goose meat and fat (Table 3). It was observed that the SE of odor intensity did not change for subcutaneous fat stored in vacuum, whereas in fat packed under MA, deterioration of the odor was noticed during storage. On the 11th D, the odor intensity of the subcutaneous fat in MA was still typical but less intense in comparison to control samples (4.28; Table 3). The odor intensity decreased with storage up to 11th D in breast muscles packed both in MA and vacuum. From 4th to 11th D goose meat stored under MA had lower SE intensity of odor than meat under vacuum (Table 3). At the end of storage, goose meat stored in vacuum was characterized by the typical odor but less intense in comparison to unpacked samples (4.12 CU; Table 3), whereas the odor intensity of MA packed samples was slightly changed (3.48; Table 3). It is hard to explain why the SE of odor intensity of muscles stored in vacuum was decreased while the FA profile did not change. Perhaps the growth of microorganisms was associated with a decrease of SE of odor intensity.

Table 3

Mean values (±standard error) of odor sensory evaluation (SE) of the goose breast muscles and subcutaneous fat packed in different atmospheres and stored at +4°C for up to 11 D.

	Packaging atmosphere	Storage time1 (d)					Significance effects
SE2 [CU]		0	4	7	9	11	PA	ST	PA × ST
Breast muscles							***	***	***
	MA	6.00 ± 0.00a	5.32 ± 0.09b,x	4.92 ± 0.05c,x	4.12 ± 0.06d,x	3.48 ± 0.10e,x
	Vacuum	6.00 ± 0.00a	5.84 ± 0.07a,y	5.24 ± 0.09b,y	4.48 ± 0.10c,y	4.12 ± 0.10d,y
Subcutaneous fat							***	***	***
	MA	5.64 ± 0.09a	5.24 ± 0.08b	4.64 ± 0.09c,x	4.40 ± 0.09c,d,x	4.28 ± 0.09d,x
	Vacuum	5.64 ± 0.09	5.48 ± 0.10	5.44 ± 0.10y	5.40 ± 0.09y	5.40 ± 0.10y

The data are average values of 50 tests for storage time 0; 25 tests for storage time 4, 7, 9,11 D.

Scale of scores: 6 = typical; 1 = completely changed; CU—conventional units.

Means with different letters in the same row, differ at P < 0.05 in view of the time of storage.

Means with different letters in the same column, differ at P < 0.05 in view of the packaging atmosphere.

Significance effects: *P < 0.05; **P < 0.01; ***P < 0.001; ns—not significant.

PA: packaging atmosphere, ST: storage time, MA: modified atmosphere, 80% O2 and 20% CO2.

The obtained data indicate negative effect of high oxygen MA storage on the FA profile and the nutritional value of goose meat and subcutaneous fat. The lower extent of oxidation in samples stored in vacuum resulted from to the fact that meat was not exposed to oxygen.

It can be concluded that packaging in a high-oxygen atmosphere facilitated the lipid oxidation of both intramuscular and subcutaneous goose fat during cold storage, resulting in changes in the FA profile, lowering the percentage of PUFA and increasing the SFA and MUFA content, and changing the odor intensity of breast muscles and the subcutaneous fat. Vacuum storage protects the intramuscular and subcutaneous fat from oxidation, so that the FA profile and the odor intensity of the subcutaneous fat during storage remain unchanged. The results of our research confirm that the lack of oxygen or its low concentration limits the oxidation processes in meat.