Influence of Nigella sativa L. Oil Addition on Physicochemical and Sensory Properties of Freezer-Stored Ground Pork for Pâté

Abstract

The purpose of this study was to investigate the effect of Nigella sativa L. (NS) oil addition on the quality of ground pork for pâté stored for one month and two months (−20 ± 1 °C). The study was conducted on a negative control (C), a positive control with the addition of antioxidant (CB) butylated hydroxyanisole (E320), and two groups with the addition of NS oil at the level of 1.9% (O1) and 3.8% (O2). The quality parameters tested in the meat were colour (measured in the CIELab system), lipid oxidation products, the fatty acid profile, thrombogenicity (T1), atherogenicity (A1), and the ratio of hypocholesterolemia to hypercholesterolemia (h/H). After roasting the pâtés, their volatile compound profiles were studied and sensory tests were conducted. A significant effect of NS oil additive on meat colour was found and ΔE for C-O2 increased faster during storage than for C-O1 and C-CB. NS oil additive in pork pâté improved the fatty acid profile. Significant differences in the rate of the fatty acid profile change during storage were observed with the addition of 3.8% NS oil compared to the other groups. Only the O2 group showed no change in PUFA content, while the h/H ratio was approximately 20% higher in the groups with added oil. The addition of NS oil also slowed the growth of TBARSs compared to the C and CB groups. The volatile compound profile of the raw pâté was most influenced by the proportion of terpenes in the NS oil. After two months of meat storage, the O1 pâté received the highest sensory ratings.

1. Introduction

Pork meat is valued by consumers and producers for its palatability and wide use in processing. According to the OECD and FAO of the United Nations, average global meat consumption per person was 33.7 kg in 2020, including pork at 10.7 kg. By 2032, per capita meat consumption is expected to increase by an average of 2%. The increase in consumption will vary geographically and will be higher in low-income countries, while it may be lower in the European Union [1]. Because meat consists mainly of protein, fat, and water, it is mainly susceptible to oxidation and decomposition processes [2]. Oxidation processes occurring in meat cause negative changes in nutritional values as well as undesirable sensory changes. The course of oxidation reactions is complex and, simplifying, one can distinguish between photosensitised oxidation and auto-oxidation. Oxidation processes are accelerated by so-called prooxidants contained in meat, among other food items, ions of metal elements such as iron (Fe³⁺) and copper (Cu²⁺) [3], and technological processes to which meat is subjected. The latter include the slaughtering process and subsequent portioning or grinding operations. The process of grinding meat, during which cell membranes are damaged, can particularly accelerate the oxidation of phospholipids and proteins [4,5]. Meat storage is an important process in economic, technological, and logistic terms. Depending on the storage conditions, negative changes in meat quality can occur. Refrigeration and freezer storage significantly slow down oxidation processes, extending the shelf life of meat, though not indefinitely [6]. The shelf life of meat can be prolonged by adding antioxidants to meat in the form of synthetic chemical compounds or natural plant extracts, herbs, spices, or oils [7]. Consumers are wary of synthetic antioxidants and they trust natural oxidative compounds more to extend the shelf life of meat and meat products. The addition of natural ingredients enhances processed meat products and is increasingly used in the production of functional foods. Different natural ingredients are often rich in various substances such as antioxidants and antimicrobial and anti-inflammatory substances. However, the key aspect to be considered is whether the natural antioxidant is acceptable to the consumer. The highest levels of natural antioxidants (such as phenolic acids and flavonoids) can be found in spices and herbs. Therefore, they are also used as antioxidant additions to meat products [8,9].

One of the spices that has been known for centuries, used in herbal medicine and recognised as a natural antioxidant, is Nigella sativa L. (NS) [10]. Nigella sativa L. is commonly known as black cumin. Nigella sativa L. seeds have a pungent, spicy flavor. As a seasoning and natural preservative, NS seeds are used in dairy products such as Mediterranean cheeses [11]. Black cumin seeds are popular as an additive in functional foods, meat dishes and baked goods [12]. It has also been found that the addition of nigella to food products is often viewed positively by consumers [13]. Black cumin is rich in sterols, tocopherols, saponins, alkaloids, bio-elements, and essential oil. Nigella has proven antioxidant, antimicrobial, antifungal, antiparasitic, and antiviral activities [14,15] and it is also an immunostimulant [16,17]. Among compounds contained in NS such as nigelle-dynein, α-hederin, hederagenin, thymohydroquinone, and thymoquinone, an affinity for SARS-CoV-2 enzymes and protein has been found, indicating that these phytochemicals, among others, have the potential to inhibit SARS-CoV-2 replication [18]. Regarding food applications, black cumin can be a valuable functional additive [19]. A popular product from black cumin is oil, which has a high content of polyunsaturated fatty acids (above 50%), including approximately 3% eicosadienoic acid. Thanks to its essential oils, black cumin oil is a fairly stable oil that is not very susceptible to oxidative changes [12,20,21]. The stability of black cumin oil and its health-promoting properties make it readily used in the food industry. Examples in the literature include the use of black cumin as a pathogen inhibitor in stored ground beef [22] and as a natural antioxidant to extend the shelf life of refrigerated stored beef patties [23], pork patties [24], and chicken meatballs [25]. Black cumin may also be an inhibitor of carcinogenic and mutagenic heterocyclic aromatic amines formed during the heat treatment of meat, which was demonstrated during a study of the use of black cumin in the production of beef meatballs [26]. In contrast, no studies were found on the effect of black cumin oil on the quality of minced pork intended for pâté which was stored under freezer conditions.

The purpose of this study was to investigate the effect of the addition of Nigella sativa L. oil on the quality of minced pork intended for pâté and stored frozen for one and two months. The quality parameters studied in the meat after thawing were colour, the fatty acid profile, lipid oxidation products, and, after roasting the pâté, the profile of volatile compounds and sensory evaluation.

2. Materials and Methods

2.1. Sample Preparation

Cold pressed Nigella sativa L. oil was purchased from a local health food shop. According to the producer’s declaration, the oil contained 18–20 g of SFA, 22–26 g of MUFA, and 54–57 g of PUFA. Fresh pork (loin and jowl in a ratio of 1:0.2) was purchased from a local shop and delivered to the laboratory (at 4 ± 1 °C). The meat was separately chopped and ground (ZMM1089I grinder with an 8-mm plate, Zellmer, Poland) and then thoroughly mixed to obtain an average fat content of 13 ± 0.5%. Sodium chloride (0.5%) was added to the raw pâté thus prepared and thoroughly mixed again. The raw pâté was divided into equal parts and assigned to four treatments with different levels of NS oil addition: C (negative control, no additive), O1 (with 1.9% NS oil addition), O2 (with 3.8% NS oil addition). The oil addition was based on the oil producer’s daily dosage indication. The fourth group (CB, positive control) consisted of meat with 0.01% butylated hydroxyanisole (BHA, E320). Each of the four prepared groups was further divided into three equal parts and vacuum-packed separately in polythene bags. One set of samples (C, CB, O1, O2) was placed in a refrigerator (4 ± 1 °C) for analysis on the same day. The other two sets of samples (C, CB, O1, O2) were placed at −20 ± 1 °C and stored for one and two months, respectively. Analyses of colour, thiobarbituric acid reactive substances (TBARSs), and fatty acids in the raw pâté on day zero and after one and two months of freezer storage were performed. In addition, volatile compound profile and sensory analyses were carried out on the same dates for meat roasted in aluminium moulds. The pâté was roasted (CPE 110 convection-steam oven, K€uppersbuch, Großkuchentechnik, Galsenkirchen, Germany) at 100 °C until 75 °C was reached inside the pâté (approximately 35 min.).

2.2. Colour Determination

Colour measurements were carried out using a Minolta chromameter (CR-400, Konica Minolta Inc., Tokyo, Japan) with an 8 mm measuring head and a D65 illuminant at a standard observation of 2°. The chromameter was calibrated using a white plate. Colour measurements were made according to Wyrwisz et al. [27]. Furthermore, the total value of the colour difference, ΔE, was calculated according to the equation:

ΔE* = sqr([L₀* − L_i*]² + [a₀* − a_i*]² + [b₀* − b_i*]²),

• Sqr: the square root;
• L₀*, a₀*, b₀*: the colour of fresh meat;
• L_i*, a_i*, b_i*: the colour of thawed meat.

2.3. Fatty Acids Profile Analysis

The fatty acid methyl esters (FAMEs) were synthesised according to the direct method [28]. Samples of 1 g of raw pâté were analysed. However, the FAMEs of black cumin oil were prepared according to the AOCS Ce 1b-89 method. A total of 0.09 g of oil was taken for analysis. The fatty acid profile analyses were performed using a gas chromatograph with a flame ionisation detector (Shimadzu GC-2010, Kyoto, Japan) and equipped with an RT^®-2560 column (100 m × 0.25 mm ID and 0.2 μm film thickness) (RESTEK, Bellefonte, PA, USA). The oven temperature program was: 4 min of isothermal heating at 140 °C, then an increase of 4 °C/min to 240 °C, which was held for 25 min. The injector temperature was 240 °C and the detector temperature was 260 °C. The sample volume injected was 1 µL with a split ratio of 70:1. The Supelco 37 FAME component standard (Supelco, CRM47885) was used to recognise the peaks. The flow rate of the carrier gas (helium) was 1.0 mL/min. Each sample was analyzed in triplicate. Based on the results of fatty acid profiles, three nutritional indices were calculated: thrombogenicity (TI) [29], atherogenicity (AI) [29], and the ratio of hypo- and hypercholesterolemic fatty acids (h/H) [30]:

$$\begin{gathered} \mathrm{T}\mathrm{I}=\frac{\mathrm{C}14:0+\mathrm{C}16:0+18:0}{\left(0.5\times \Sigma \mathrm{M}\mathrm{U}\mathrm{F}\mathrm{A}\right)+\left(0.5\times \Sigma \mathrm{n}-6\right)+\left(3\times \Sigma \mathrm{n}-3\right)+(\frac{\Sigma \mathrm{n}-3}{\Sigma \mathrm{n}-6})} \\ \mathrm{A}\mathrm{I}=\frac{\mathrm{C}12:0+\left(4\times \mathrm{C}14:0\right)+16:0}{\left(\Sigma \mathrm{P}\mathrm{U}\mathrm{F}\mathrm{A} \mathrm{n}-3\right)+\left(\Sigma \mathrm{P}\mathrm{U}\mathrm{F}\mathrm{A} \mathrm{n}-6\right)+\left(\Sigma \mathrm{M}\mathrm{U}\mathrm{F}\mathrm{A}\right)} \\ \frac{\mathrm{h}}{\mathrm{H}}=\frac{\mathrm{C}18:1\mathrm{n}9+\Sigma \mathrm{P}\mathrm{U}\mathrm{F}\mathrm{A}}{\mathrm{C}14:0+\mathrm{C}16:0} \end{gathered}$$

2.4. Volatile Compounds Profile

Volatile compound analysis was performed in accordance with the method described by Górska-Horczyczak et al. [31]. For the study, the Heracles II electronic nose (Alpha MOS Co., Toulouse, France), based on ultra-fast gas chromatography with two capillary columns (DB-5 and DB-1701) with headspace, was used. Hydrogen was taken as a carrier gas. For the study, 20 mL vials with 2.5 g samples were incubated at a temperature of 55 °C for 15 min. The temperature program was: isothermic heating at 40 °C for 5 s, then an increase of 4 °C/s to 270 °C, which was held for 30 s; FID1/FID2 were held at 270 °C and the injector was held at 200 °C. A standard mixture of alkanes (C6–C16, Restek, Bellefonte, PA, USA) was used. Each sample was analyzed in triplicate.

2.5. Lipid Oxidation Product TBARSs

Thiobarbituric acid reactive substances were determined according to the method described by Brodowska et al. [32], which was based on the method of Robles-Martinez et al. [33]. The absorbance was measured at 532 nm using a spectrophotometer (Shimadzu UV-1800, Kyoto, Japan). For testing, 2.5 g of minced meat was taken and 25 mL of trichloroacetic acid solution with antioxidant was added. The mixture was homogenised for approximately 30 s. The samples were centrifuged (10,000 rpm; MPW-352R, Warsaw, Poland) and 2 mL of the supernatant was collected for analysis. Then, 2 mL of a 0.02 M 2-thiobarbituric acid solution was added. The samples were heated at 90 °C for 40 min, then cooled, and absorbance measured against a blank. The recovery and calibration curve were performed under the same conditions. For testing, 1,1,3,3-tetramethoxypropane (TMP) was used as the standard. The calibration curve was in the concentration range of 0.1–3.0 μM of TMP. The recovery was carried out in triplicate. The results were presented as mg of malonoaldehyde per kg of test sample.

2.6. Sensory Evaluation

The roasted pâtés were subjected to sensory evaluation. The evaluation was carried out according to ISO 13299 [34] using a 10-point hedonic linear scale (extremely undesirable, extremely desirable). The following attributes were assessed: appearance, colour, taste, flavour, juiciness, texture, and the overall acceptability. The evaluation involved 11 experienced panelists (women) aged between 25 and 38 years. The panelists were employees of the University of Life Sciences. The panelists met the conditions of the ISO 11132 standard [35]. The pâtés were roasted and evaluated on day zero and after one month and two months of frozen storage of the minced meat. The coded samples for evaluation were served on paper trays. The sensory evaluation was repeated three times.

2.7. Statistical Analysis

Statistica v. 12 software (StatSoft Inc., Tulusa, OK, USA) was used for statistical analysis. Linear correlation was assessed with Pearson’s coefficient. Analysis of variance (ANOVA) and Tukey’s post-hoc test were performed with a significance level of α ≤ 0.05. Heracles II AlfaSoft 14.2 software with statistical quality control (SQC) was used to compare the profiles of volatile compounds.

3. Results and Discussion

3.1. Changes in Colour during Storage

With storage time, metabolic changes such as the oxidation of myoglobin and lipids occur in meat, which consequently affect the quality and colour of the product [36]. The effect of Nigella sativa L. oil addition on the colour (measured in CIELab) of fresh and frozen ground meat stored in the freezer (−20 ± 1 °C) is shown in

Table 1. Colour parameters of the raw pork pâté stored frozen for one month and two months (−20 ± 1 °C).

Group	L*	a*	b*	ΔE
D0; Fresh meat
C	63.37 ± 0.66 A	11.41 ± 0.25 A	9.06 ± 0.1 A	-
CB	63.94 ± 1.33 A	11.16 ± 0,74 A	8.90 ± 0.58 A	0.76
O1	63.96 ± 0.95 A	10.91 ± 0.17 A	10.13 ± 0.18 B	1.36
O2	65.92 ± 2.16 B	8.80 ± 1.01 B	12.59 ± 1.02 C	5.13
M1; Meat after a month of frozen storage (−20 ± 1 °C)
C	65.28 ± 0.47 B	11.35 ± 0.44 A	11.02 ± 0.06 C	-
CB	65.22 ± 1.69 B	11.99 ± 1.13 B	11.28 ± 1.01 C	0.69
O1	68.75 ± 1.44 C	9.86 ± 0.14 B	11.54 ± 0.44 C	3.81
O2	65.81 ± 0.54 B	8.71 ± 1.69 B	11.63 ± 0.84 C	2.76
M2; Meat after two months of frozen storage (−20 ± 1 °C)
C	65.51 ± 2.09 B	10.22 ± 0.83 A	9.86 ± 0.36 B	-
CB	65.19 ± 2.37 B	10.66 ± 1.10 A	9.33 ± 0.82 B	0.76
O1	69.24 ± 0.66 C	8.15 ± 0.69 B	12.63 ± 0.48 D	5.09
O2	68.05 ± 0.9 C	6.54 ± 0.49 D	13.18 ± 0.45 D	5.57

C, negative control; CB, positive control with 0.01% BHA; O1, group with 1.9% Nigella sativa L. oil; O2, group with 3.8% Nigella sativa L. oil. The parameters in the columns (value ± standard deviation) denoted with different letters (A–D) differ significantly at the confidence level of p < 0.05.

.

The addition of Nigella sativa L. oil (O1, O2) caused an a* saturation change by decreasing the proportion of red colour and a b* saturation change by increasing the proportion of yellow colour. Meat stored in the freezer becomes discoloured. The value of the a* component was reduced, meaning the redness of the meat was reduced, while the L* parameter was increased [37]. Such changes were observed for negative control C (no additive) and CB (0.01% BHA), where significant differences in colour were found between the fresh and freezer-stored meat. Larger changes in colour occurred in the groups with oil addition, which were significantly different from the C and CB groups. Changes in the saturation of red, blue, green, and yellow hues were due to the addition of black cumin oil. Depending on the extraction method, black cumin oil is characterised by the colour parameters: L*, 28.8; a*, 0.5; and b*, 1.36 [38]. Assessment of colour differences using ΔE showed that the differences between C and CB for fresh meat and meat stored for one and three months are not noticeable. In contrast, only the addition of 1.9% oil made the difference between fresh meat without the additive (C) and the O1 group barely noticeable to the human eye at ΔE = 1.36 on day zero [39]. The difference increased in subsequent storage periods and the colour change was clearly noticeable.

3.2. Fatty Acids

The fatty acid profile on day zero was as follows: C: 47.5% MUFA, 12.7% PUFA, 38.8% SFA; CB: 46.9% MUFA, 13.6% PUFA, 38.3% SFA; O1: 44.1% MUFA, 19.6% PUFA, 35.5% SFA; O2: 42.8% MUFA, 22.4% PUFA, 33.5% SFA. The change index of the fatty acid profile in meat stored for one month and two months in a frozen state at −20 ± 1 °C is presented in Figure 1.

The fatty acid profile of Nigella sativa L. oil consisted of 24.6% MUFA, 58.4% PUFA, 16.9% SFA. NS oil additive in pork pâté improved the fatty acid profile. The principal change observed was a reduction in SFA fatty acids: C16 was reduced from 25% (C, CB) to 23.7% (O1) and 23% (O2) while C18 was reduced from 12.4% (C, CB) to 10.7% (O1) and 10% (O2). Significant changes (p < 0.05) were observed in the group of unsaturated fatty acids; in particular, the proportion of oleic acid was reduced from 43% (C, CB) to 40% (O1) and 39.5% (O2). In the case of linoleic acid content, the share was increased from 11% (C, CB) to 17.4% (O1) and 20% (O2). Oil from Nigella sativa L. is a major source of fatty acids such as linoleic acid [40,41].

For minced pork, after one month of storage at –20 °C, the content of PUFAs decreased in variants C, CB, and O1, while saturated acids increased. A similar trend in variants C, CB, and O1 was observed after two months of storage. This trend is due to the effects of lipolysis and oxidation that can occur during frozen storage, resulting in a decrease in product quality. Meat phospholipids as well as polyunsaturated fatty acids are the lipid fraction most susceptible to oxidation. Therefore, after the thawing process, they can lead to secondary lipid oxidation [42]. Similar tendencies during pork storage were observed in studies by Medić et al. [43], Feng et al. [44], and Shimizu and Iwamoto [45]. The change index analysis of the fatty acid profile shows that the addition of butylated hydroxyanisole during storage (−20 °C, after one and two months) contributed to an increased loss of PUFAs compared to the other variants tested. This result may be due to the pro-oxidant effect of the antioxidant used [46,47]. Significant differences in the rate of change in the fatty acid profile during storage were observed with the addition of 3.8% Nigella sativa L. oil compared to the other groups. There was no change in the PUFA content of O2 after either the first or second month of storage. On the other hand, the increase in SFA content after the second month (O2) of storage was significantly lower than in the C, CB, and O1 groups. This confirms the ability of NS oil to inhibit lipid oxidation [22].

The fatty acid profile was utilised to determine three nutritional indicators: TI, AI, and h/H. The findings are shown in

Table 2. Nutritional indicators: thrombogenicity (TI), atherogenicity (AI), and the hypo-and hypercholesterolemic ratio (h/H) for raw pâté.

Group	C	CB	O1	O2
D0; Fresh meat
TI	1.20	1.17	1.05	0.99
AI	0.52	0.52	0.46	0.43
h/H	2.10	2.12	2.41	2.55
M1; Meat after a month of frozen storage (−20 ± 1 °C)
TI	1.22	1.22	1.07	1.00
AI	0.52	0.52	0.45	0.42
h/H	2.08	2.1	2.44	2.61
M2; Meat after two months of frozen storage (−20 ± 1 °C)
TI	1.23	1.24	1.11	1.04
AI	0.52	0.52	0.46	0.43
h/H	2.10	2.08	2.35	2.52

C, control group; CB, group with 0.01% BHA; O1, group with 1.9% Nigella sativa L. oil; O2, group with 3.8% Nigella sativa L. oil.

.

According to Barros et al. [48], it is advisable for meat products to have minimal AI and TI values and a high h/H ratio. The higher the value of the h/H ratio, the more the product may contribute to cardiovascular health improvement [49]. TI and AI indices for the groups with the addition of Nigella sativa L. oil were lower than for C and CB in the fresh pâté as well as the pâté stored for one and two months. The h/H ratio was about 20% higher in the oil-added groups, indicating that the addition of NS oil improves the nutritional value of the pâté. Zhao et al. [50] also studied the thrombogenic index (TI) and atherogenic index (AI) in modified pork meat batter. However, replacing the fat in pork meat with oil-modified crosslinked starch did not result in an improvement in TI and AI. This was due to the lack of the added oil effect on the fatty acid profile of the pork meat batter. However, replacing 50% of animal fat in burgers with a hydrogel emulsion of linseed oil and pea protein increased the PUFA to SFA ratio and reduced AI and TI [51], which, similarly to our studies, improved the nutritional quality of burgers.

3.3. TBARSs

Meat minced into pâté immediately after preparation had TBARS values of approximately 0.95 mg MDA/kg for CD0 and CBD0 samples, and these were already increased values, indicating oxidative processes. Above the level of 0.5 mg MDA/kg, consumers may already notice rancidity [52,53]. The addition of black cumin oil significantly raised the TBARS values to 1.15 for O1D0 and 1.25 for O2D0. The level of lipid oxidation in meat stored one and two months frozen compared to fresh meat on day one is shown in Figure 2. The lowest index of lipid oxidation change in pork pâtés was for variants with 1.9% and 3.8% of Nigella sativa L. oil O1 (1.46) and O2 (1.38), respectively, when stored for the first month at −20 ± 1 °C. The highest TBARS change index after the first month of storage was observed for the negative control variant (C, 1.88). On the other hand, after two months of storage, the lowest oxidative changes were observed for the variant with 3.8% nigella oil and the highest were observed for the negative control variant C (1.98).

In the O1 and O2 groups with NS oil, a slower increase in TBARSs was observed than in the group with BHA after both one and two months of storage. The use of 1.9% black cumin oil in pork pâté after two months of storage showed the same effect as the addition of 0.01% BHA, with change index values remaining between 1.64 and 1.76. The results indicate that the oil’s antioxidant properties can be used to slow down the oxidative changes of pork pâtés during storage. A study by Sallam et al. [54] showed the antioxidant effect of black cumin oil at 1%, 2%, and 3% concentrations when used as an additive to beef patties. Furthermore, a study by Wojtasik-Kalinowska et al. [25] showed that storage of raw minced pork at 4  ±  1 °C for eight days with an additive of 1.88% oil was as effective as using the synthetic antioxidant BHA. The antioxidant properties of Nigella sativa L. oil were also confirmed by Soleimanifar et al. [55], Bordoni et al. [56], and Mukhtar et al. [19]. The oil’s antioxidant properties are due to the presence of bioactive compounds such as sterols (β-sitosterol, avenasterol, stigmasterol, campesterol, and lanosterol), tocopherols (α, β, and γ), thymoquinone, and retinol (vitamin A) [57].

3.4. Changes in the Volatile Compounds Profile

Meat aroma is correlated with fat content, quality, and composition. The profile of volatile compounds is shaped by fatty acids and their transformations during storage and thermal processes, among other things. In the raw meat samples prepared for the pâté, more than 60% of the fatty acids were unsaturated acids, from which volatile compounds such as aldehydes, alcohols, and ketones are formed during oxidation processes [58]. A total of 24 volatile compounds were identified in the baked pâté. The most abundant group were terpenes (six compounds) found only in the pâtés with added nigella. Other volatile compounds belonged to the groups of aldehydes (five compounds), N-compounds (four compounds), and S-compounds (three). Two ketones, one alcohol and one organic acid were also present. The profile of volatile compounds in terms of the proportion of compound groups is shown in Figure 3. In contrast, Figure 4 shows the differences in the profile of volatile compounds using odour distances determined on the basis of Euclidian distance.

Aldehydes proved to be the group of compounds with the highest percentage of contribution to the volatile compound profile of the pâtés without added black cumin oil. During roasting, the Strecker amino acid degradation and Maillard reaction produced 3-methylbutanal and 2,3-butanedione and other amino acid degradation products such as the aldehydes 2-methylpropanal and 2-methylpentanal [59]. Propanal was predominantly found in meat pâtés after freezer storage in the CM1, CM2, CB0, CBM1, CBM2 groups, which could also be due to lipid autooxidation [60]. These processes are confirmed by the positive correlation between TBARSs and propanal and pentanal, with values of 0.69 and 0.52, respectively. Many researchers report strong correlations between TBARSs and the sum of aldehydes such as hexanal, propanal, pentanal [61,62,63]. In contrast, propanal appeared in minimal amounts in the groups supplemented with nigella oil, which could indicate an effect of nigella antioxidants in slowing the rate of autooxidation. Similarly, Rahman et al. [23] found a positive effect of black cumin extract on lipid stability in beef pâtés during refrigerated storage. Slower formation of alcohols was observed in all pâtés from the O1 and O2 groups, in contrast to the negative control after two months of freezer storage. Alcohols can be formed as a result of various processes in the meat, including reactions with acids as well as reductions in aldehydes. The formation of alcohols is favoured by the increased presence of aldehydes [64]. Figure 3 shows the increase in the alcohol content and the decrease in the aldehyde content in the CM2 group. However, a similar tendency was observed in the CBM2 group, but with a smaller increase in alcohols due to the presence of BHA. Maillard-derived nitrogen-containing and sulfur-containing compounds were found in all the pâté variants tested with and without nigella. This group of compounds included pyrazine, 2,5-dimethylpyrazine, and 2,3-dimethylpyrazine, which shape the characteristic odour description of the roasted, sweet, potato-like aroma of heat-processed meat [65,66]. The S-compounds group included methyl disulfide, dimethyl disulfide, and thiophene, which contribute to the distinctive flavor of meat [67]. Thiophen was mainly found in the variants without the addition of black cumin oil. The correlation between the content of black cumin in the pâté and thiophene was −0.87 and was strongly negative. In general, thiophenes are the result of the degradation of cysteine and carbonyl compounds due to the oxidation of lipids during the thermal processing of meat [68]. Figure 3 shows a 10-fold decrease in S compounds, mainly thiophen, in pâtés with added nigella oil. The verified correlations between the content of black cumin and dimethyl sulfide and 2-methylpropanal were −0.88 and −0.94, respectively, which may indicate the slowing down of oxidation processes with an increase in the addition of NS oil. Zwalan et al. [25] noticed a slowdown in oxidative changes in refrigerated poultry meatballs with added NS ethanol extract. Terpenes and esters predominated in all O1 and O2 samples. The source of these compounds was black cumin oil [40,69]. Terpenes and esters had a significant impact on the profile of volatile compounds (Figure 4) as well as on the sensory evaluation of roasted pâtés (Figure 5).

Figure 4 confirms that the volatile compound profile was influenced the most by the addition of black cumin oil. Similarly, in the study of Andaleeb et al. [70] the aromatic hydrocarbons from Chinese five-spice and garam masala spices had a dominant role in the profile of volatile compounds of chicken breast with spices. Many researchers have found that the volatile compound profile of the product is dependent on the added aromatic spices [71,72]. In comparative studies of stored food products, faster changes in the volatile compound profile of products without spices were observed [23,72,73]. Despite the use of two levels of oil addition, the volatile compound profiles were very similar. Only on day zero did the O1D0 variant of the pâté differ slightly from O2D0. In contrast, the profile of volatile compounds changed during storage of the raw pâtés in the negative control and in the positive control with the addition of BHA. At day zero and after one month of storage, the profile in the negative control without additives changed minimally, while in the group with BHA it practically remained the same. In contrast, a marked change was observed after two months of storage. In the negative control, there was a difference of about 18 units between day zero (variant CD0) and after two months of storage (variant CM2). A smaller change was observed in the group with added BHA between variants CBD0 and CBM2, i.e., by about 13 units on average.

3.5. Sensory Acceptability

On day zero, the roasted pâtés with the addition of NS oil received higher scores than the others (Figure 5a).

In particular, groups O1 and O2 were characterised by a higher aroma intensity and a higher juiciness and appearance. Rahman et al. [23] noticed that 0.3% of black cumin in beef pâté resulted in a higher flavour rating for the pâté stored in the refrigerator. On the other hand, Vargas-Ramella et al. [74] replaced the pork fat in the pork pâté with encapsulated fish oil. Consumers noticed a fishy flavor in the pâtés. However, the overall liking did not change regardless of the level of addition of microcapsules with fish oil instead of pork fat. On the other hand, sensory evaluation of pork pâté with pre-emulsified canola showed no differences compared to pâté with full fat [75]. After the first month of frozen storage, the pâtés from the O2 group, with a higher level of black cumin, received the highest ratings in terms of flavour and juiciness. The highest overall acceptability was given to the O1 group. After two months of frozen storage of minced meat for pâté, the sensory evaluation of the pâté decreased in all criteria and in all experimental groups. For appearance, colour, flavour, juiciness, texture, and overall acceptability, the O1 pâté received the highest scores. Only taste was rated highest in the O2 group. Regarding colour, the O1 group was characterised by a significantly higher brightness (L*) after two months of storage compared to the groups without black cumin. Pâtés with black cumin oil had a very similar profile of volatile compounds throughout the storage period and were dominated by terpenes and esters, i.e., compounds that are perceived as a sign of freshness. Rahman et al. [23] explained the deterioration in the taste of patties during storage of meat without black seed oil in terms of increased lipid oxidation, the release of free fatty acids, and the dispersion of volatile compounds.

4. Conclusions

The use of Nigella sativa L. oil as a functional additive for meat positively affected its quality and consumer acceptance. The fatty acid profile was improved by decreasing the proportion of saturated acids and increasing the linoleic acid content in the O1 and O2 groups. In the O2 group (3.8% NS oil), there was no decrease in MUFA or increase in SFA after two months of freezer storage, in contrast to the CB group (0.01% BHA). Nutritional indices were also improved in both groups with NS oil. Pâtés with NS oil showed a slower increase in TBARSs compared to CB. Relative changes in the value of TBARSs in meat stored one month and two months frozen (−20 ± 1 °C) compared to fresh meat on day zero for the 02 group were significantly lower than for the CB group. The profile of volatile compounds in the stored pâtés was stable in the groups with the addition of nigella, which was decisively influenced by terpenes. Sensory analysis showed that after two months of meat storage (−20 ± 1 °C), the sensory appeal of the pâtés from all four groups decreased. In contrast, the pâté from group O1 with an added NS oil level of 1.9% was rated the best of all groups. It can be seen that the addition of Nigella sativa L. oil to the pork mince at 1.9% and 3.8% had a favourable effect on its quality during freezer storage.