1. Introduction
Nowadays, meat burgers are one of the most popular products; however, their consumption in excess is related to unhealthy habits due to their high content of saturated fatty acids (SFA). These fatty acids are related to the risk of chronic, carcinogenic, and degenerative diseases [
1,
2,
3]. COVID-19 provoked an increase in interest in eating healthier foods and meat products were not the exception. Several studies have shown that consumers are willing to consume new or reformulated healthy meat products [
4,
5]. A feasible alternative to this situation is to replace fatty tissues (belly, lard, etc.) with gelled emulsions (GE). These emulsions are made with polyunsaturated oils such as walnut, almond, chia, hemp, soybean, sunflower, wheat, or algae oils, which are healthier than animal fats. The development of GE generated by gelation procedures can ensure health-enhancing nutritional properties and could reduce cardiovascular diseases within a balanced diet [
6,
7], without the loss of technological characteristics and sensory properties, making these types of products well appreciated by the consumers [
5,
8]. Some authors have obtained promising results for GE using various vegetable oils with healthy lipid profiles, such as the previously aforementioned oils with gelling agents such as starch corn, makgeolli, basil gum, gelatin, date flour, and amaranth flour [
9,
10,
11,
12,
13,
14]. All of these have been successfully used in low-fat meat products.
In the development of healthy meat products, gelled emulsions are used as fat analogs. One of the most important aspects when GEs are used is to improve the lipid profile, but their use can change the sensory characteristics and the technological qualities of these type of products [
3]. Therefore, it is very important to reformulate this type of product without any loss of important characteristics for consumers and industries [
8,
9,
11]. Animal fat substitution and the development of new healthy meat products presents a healthy and sustainable alternative diet based on traditional meat burgers. Thus, the substitution of PB with soybean oil (
Glycine max) and chincho (
Tagetes elliptica Sm.) essential oil could be an attractive, nutritious, and ethical alternative to conventional meat burgers.
Maca (
Lepidium meyenni) flour has beneficial health effects due to its content of bioactive compounds, including glucosinolates and flavonoids [
15]. From a technological point of view, the starch content in maca as a product of fractionation processing could be used as an emulsifier and stabilizer to give foods the desired texture and consistency [
16]. Furthermore, antioxidants derived from maca could be used to prevent lipid-rich foods from developing rancidity and to control enzymatic browning of fresh produce [
17]. Soybean oil is a worldwide and well-known oil for its content of tocopherols and polyunsaturated fatty acids, among other bioactive compounds [
18]. The most important polyunsaturated fatty acids found in soybean oil are linolenic and linoleic acids, while oleic acid is the main monounsaturated fatty acid [
19]. Thus, due to this composition, soybean oil could be a good lipid source for the elaboration of gelled emulsions to be used as fat replacers. On the other hand, healthy meat product developers must take into account that GEs elaborated with polyunsaturated oils are susceptible to lipid oxidation with unpleasant meat product characteristics such as rancidity, off flavors, and discolorations, among others [
20]. To avoid these negative aspects, essential oils could be an excellent alternative to avoid lipid oxidation in healthy meat product development [
21]. Several studies have shown that essential oils obtained from plants of the
Tagetes genus have demonstrated antioxidant and antimicrobial properties [
22,
23,
24]; for this reason, the use of the essential oil of
Tagetes elliptica Sm. could be a good option in the formulation of healthy meat burgers rich in polyunsaturated fatty acids.
T. elliptica, the binomial name of Chincho, is an ethnic aromatic plant cultivated in several regions of Central and South America [
25]. It has been used for many years as a species to enhance flavor in meat seasoning [
26]. Thus, the essential oil obtained from chincho could give healthy meat burgers antioxidant and antimicrobial properties and aromatic compounds [
27]. In this way, the elaboration of meat burgers partially substituted with GEs elaborated with soybean oil, maca flour, and chincho essential oil could be an excellent natural vehicle to improve the lipid profile of meat products, and represent a promising alternative to the gelled emulsions currently used in emulsion-type applications.
The aim of this study was to analyze the effect of partially replacing pork backfat with gelled emulsions elaborated with maca flour, soybean oil, and chincho essential oil on chemical composition, physicochemical and cooking properties, and lipid oxidation, as well as the sensory analysis of beef burgers.
2. Materials and Methods
2.1. Food Materials
In the present study, different gelled emulsions were prepared with the following ingredients: organic Peruvian maca flour (MF) (protein 11.9%, carbohydrates 61.5%, fat 0.7%, and dietary fiber 15.1%) and soybean oil (SO) (48.22% linoleic acid, 30.26% oleic acid, 11.07% palmitic acid, and 5.36% linolenic acid) were purchased in a local supermarket (Orihuela, Spain). Beef meat (72.30% moisture, 1.85% fat, 24.96% protein, and 0.87% ash) and pork backfat (11.20% moisture, 75.60% lipids, 12.43% protein, and 0.77% ash) were acquired from a local butchery provider (Orihuela, Spain). Chincho essential oil was obtained by directed steam distillation of chincho leaves collected in the province of Chupaca, Junin Region, Peru (3263 m above sea level). Gelatin of animal origin (pork) with 180 bloom was obtained from Sosa Ingredients S.L. (Barcelona, Spain)
2.2. Preparation of Oil in Water Gelled Emulsions GEs
The gelled emulsions were prepared with maca flour, soybean oil, and chincho essential oil according to Botella-Martinez et al. [
28]. Four gelled emulsion were formulated (GE
1, GE
2, GE
3, and GE
4) and their composition is described in
Table 1. The emulsions obtained were kept at 4 °C until the production of the burgers.
2.3. Formulation and Processing of Burgers Containing Gelled Emulsions GEs
Five batches of meat burgers were prepared by partially replacing animal fat with gelled emulsions prepared with soybean oil, maca flour and chincho essential oil. A total of 90 burgers (18 burgers for each treatment) with an approximate weight of 29.5 ± 0.05 g each were prepared. The traditional formula was used as a control sample (BC), while for the other four treatments, pork backfat was replaced by a gelled emulsion (GE
1, GE
2, GE
3 and GE
4), as indicated in
Table 2. The samples were shaped with industrial-type burger equipment to obtain samples approximately 0.90 ± 0.05 cm thick and 6.3 ± 0.29 cm in diameter. The burgers were packed into bags and stored at 4 °C until further analysis. Six burgers of each formulation were cooked on a griddle to an internal temperature of 71 °C, taken in the geometrical center of each burger through a hypodermic-type thermometer (Model HVP-2-21-V2-TG-48-OCT-M Omega, Stanford, CT, USA) approximately 2.5 min per side.
2.4. Proximate Composition
Moisture, protein (using N × 6.25 as conversion factor), fat, and ash contents were determined according to the official methods of the Association of Official Agricultural Chemists (AOAC) [
29].
2.5. Lipid Profile and Health Indices
2.5.1. Fatty Acid Profile
To analyze the fatty acids profile, burger fat was obtained from 5 g of sample (raw and cooked burger) according to the methodology of Folch et al. [
30]; then, the lipid phase was transmethylated following the method and conditions described by Golay and Moulin [
31]. The fatty acid methyl esters (FAMEs) were separated and quantified using a gas chromatograph—Hewlett-Packard 6890—with a flame ionization detector (FID) and a Suprewax 280 capillary column (30 m, 0.25 µm film thickness, 0.25 mm i.d.; Tecknokroma Barcelona, Spain), was carried out according to the chromatographic conditions described by Pellegrini et al. [
32], and was expressed as g/100 g of fat.
2.5.2. Health Indices
To evaluate the nutritional quality of burgers, the health indices of beef burgers were calculated. Total fat content and fat composition, measured as total saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids contents, and the n-3 and n-6 fatty acid ratio, the PUFA and SFA ratio were obtained. In the same way, n-6/n-3 and PUFA/SFA ratios and atherogenic index (
AI), thrombogenic index (
TI), and hypocholesterolemic/hypercholesterolemic (h/H) were calculated following Equations (1)–(3), respectively, using the equations developed by Ulbricht and Southgate [
33].
2.6. Physicochemical Analysis
2.6.1. Color Parameters, pH, and Water Activity
The color of raw and cooked patties was evaluated using CIELAB color space (D
65 as illuminant and 10° as standard observer) and L*a* b* color coordinates (L*, a*, and b* represent lightness, red/green color, and yellow/blue color, respectively). Samples were measured using a Minolta CM-700 (Minolta Camera Co., Osaka, Japan) using SCI mode and a low-reflectance glass placed on the surface of the sample and equipment. AMSA guidelines for color evaluation were applied [
34,
35]. Before the measurements, the equipment was calibrated following the equipment recommendations (calibrate plate values of L* = 97.14, a* = 0.14 and b* = 2.40). Six random points from each sample were taken for color determination. The psychophysical magnitudes hue (H*) and chroma (C*) in raw and cooked burgers were also calculated using Equations (4) and (5), respectively.
The total color differences (ΔE*) of each reformulated sample with respect to the control burger were calculated with Equation (6).
where s: sample, and c: control beef burger.
Equations (4)–(6) were obtained according Cassens et al. [
36].
Water activity was determined in raw burgers using an electrolytic hygrometer (Novasina TH-500, Novasina, Pfaeffikon, Switzerland) at 22° C. The pH of the samples was measured with a digital portable pH meter using a penetration probe at different sites of the raw and cooked burgers using a Crison model 510 pH meter, (Barcelona, Spain).
2.6.2. Texture Profile Analysis
Texture profile analysis (TPA) was performed in six replicates in cooked burgers. The tests were performed in a TA-XT2i texture analyzer (Stable Micro Systems, Surrey, England). Cubic samples of (2 × 2 × 2 cm) were obtained for fresh and cooked samples, respectively. Samples were compressed to 75% of their original height with a cylindrical probe of 10 cm diameter at a compression load of 25 kg with a constant velocity of 1 mm/s at 15–20 °C. The following parameters were calculated: hardness (N), springiness, cohesiveness, chewiness (N), and gumminess [
37].
2.7. Cooking Properties
Cooking properties were determined using three burger samples for each treatment. Meat burgers from each batch at room temperature were weighed and their diameters were measured; these procedures were repeated after cooking. The reduction in diameter and the increases in thickness and cooking loss were calculated according to Equations (7)–(9).
2.8. Oxidative Stability
The evaluation of lipid stability was performed on raw and cooked burgers by measuring thiobarbituric acid reactive substances (TBARS) following the method proposed by Rosmini et al. [
38]. The TBARS value was calculated from a malonaldehyde standard curve expressed as mg of malondialdehyde (MDA)/kg of sample.
2.9. Statistical Analysis
Experimental data were expressed as mean ± standard deviation of three repeated measurements per sample (five treatments). Statistical analysis for chemical composition and physicochemical and cooking properties was performed by one-way analysis of variance (ANOVA). Oxidative stability was analyzed by means of a two-way ANOVA test with two factors: thermal treatment (two levels: raw or cooked) and treatments (five levels: BC, BSM, BSMC0.25, BSMC0.5, and BSMC1.0). Tukey’s post hoc test was applied for comparisons of means; statistical significance was accepted at a level of (p < 0.05) in all statistical analyses using the software SPSS® IBM® Statistics 22.0.0.0. (International Business Machines Corp., Armonk, New York, NY, USA).
4. Conclusions
Replacement of pork backfat with gelled emulsion GE reduced the content of saturated fatty acids (SFA) and increased that of polyunsaturated fatty acids (PUFA) (mainly linoleic acid); in addition, there was a considerable increase in the PUFA/SFA ratio and a decrease of up to 26.53 and 34.45% in the atherogenicity and thrombogenicity indices (BSMC0.5 and BSMC1.0), respectively. The h/H ratio increased to a value of 37% (BSMC1.0).
In addition, the addition of gelled emulsion decreased the amount of fat and protein, and lowered the pH; water activity in raw burgers was not modified. Hardness (p < 0.05), cooking losses, shrinkage, and thickness changes decreased with the addition of GE. Lipid oxidation levels were higher in cooked burgers and were significantly affected (p < 0.05) by GE substitution.
Therefore, replacing pork backfat with gelled emulsions containing maca flour, soybean oil, and chincho essential oil can be considered as an effective strategy to produce healthier burgers without negatively affecting their physicochemical and technological properties.