Effects of Beef Fat Replacement with Gelled Emulsion Prepared with Olive Oil on Quality Parameters of Chicken Patties

Chicken breast and beef fat were purchased from a local market. Extra virgin olive oil was supplied from Taris Co. (according to the specifications of the supplier, it was consisted of 70.98% oleic acid (C18:1), 12.46% palmitic acid (C16:0), 11.4% linoleic acid (C18:2), 2.66% stearic acid (C18:0), 0.5% linolenic acid (C18:3) and 2243 ppm total sterol), oil phase emulsifier polyglyserol polyricinoleate (PGPR) was obtained from Çağdaş Chemicals Co. (Turkey). Gelatin was purchased from Sigma-Aldrich. Inulin powder (Ash Content: 0.05-0.15% Glucose: 0-1.6% Sacarose: 1.05-3.05% Dry Matter Content: 93-70.97% Carbohydrates: 94.90% Inulin: 88-92% Fructose: 1.2-3.2%) was obtained from BENEO-Orafti.

Gelled emulsion was prepared according to the method described by Poyato et al. (2014) with modifications. The oil phase (50 g/100 g emulsion) containing the PGPR as surfactant (6.4 g/100 g oil), was added to the aqueous phase containing 3 g gelatin/100 g emulsion and 9 g inulin/100 g emulsion and homogenized. Both phases were previously heated separately to 55°C on a hot plate stirrer. After the homogenization process (6000 rpm, Ultra-Turrax^® T25basic, UK), the emulsion was cooled to room temperature. The GE was kept for 12 h at 4°C until being used in chicken patties.

Four different chicken patties were formulated as indicated in Table 1. In control samples (C) 20 g/100 g of beef fat was added, whereas in the three experimental batches different percentages, 25% (G25), 50% (G50) and 100% (G100), of beef fat were substituted with gelled emulsion. Salt (2 g/100 g) was added to all formulations. Fat content of all samples were set as 20% (beef fat, GE or both). Chicken breast and beef fat were minced through a 3 mm plate grinder (Turkey), separately. Ground meat, fat source (beef fat and/or GE), and salt mixed in food processor for 2 min (Germany) and chicken patties were formed with the appropriate tool (d:9 cm, h:1.5 cm). During preparation of chicken patties the temperature of the mixture was kept below 10°C. After forming, the samples were cooked in electric oven (Turkey) at 180°C until core temperature reached to 73°C. Samples were cooled to room temperature and analyses were performed.

pH value of GE and chicken patties were measured in triplicate by using a pH-meter (WTW pH 3110 set 2, Germany) equipped with a glass penetration probe.

Color parameters of GE and cooked chicken patties were measured using a digital colorimeter (Chromameter CR 400, Minolta, Japan) to obtain the color coordinates lightness (CIE L*), redness (CIE a*) and yellowness (CIE b*).

Syneresis (S) was measured in triplicate according to Bot et al. (2014). A sample was cut in half in the tub, and one of both halves was removed. The weight of the half-filled 100 mL tub [W₁] was determined and the tub is sealed again. The tub was stored for 4 h at 25°C. Subsequently, the lid was removed and the sample was weighed again [W₂]. The value should be almost equal to W1, and was used as a check only. Then all fluid was removed from the tub and inside the tub was wiped with paper tissue, and the weight of the tub was determined again [W₃]. Finally, the sample was removed from the tub, and the empty tub was weighed [T]. The stability against syneresis of the samples was calculated by using the following equation: Syneresis = (W₁ − W₃) / (W₁ − T)

Centrifugation and thermal stability of GE were determined. Centrifugation stability was measured after the preparation of GE to observe any phase separation after centrifugation at 1400 rpm for 3 min (Serdaroğlu et al., 2016b). Creaming stability was measured according to Gu et al. (2005) in samples stored at 4°C for 7 d. Serum layer separation was observed and measured to express creaming stability as a percentage of initial sample height. Thermal stability, in terms of water and fat binding properties was measured in GE according to Surh et al. (2007). For thermal stability test, the tubes containing 25 g of the GE was hermetically sealed and heated in a water bath (70°C/30 min). Afterwards, they were then opened and left to stand upside down (for 50 min) to release the separated fat and water onto a plate. The stability of emulsions after heating (thermal stability) or storage (creaming stability) were recorded in terms of phase separation and expressed as a percentage of initial sample height. These parameters were determined in triplicate.

Moisture and ash contents of raw and cooked chicken patties were determined according to AOAC method (2012). Protein content of the samples was determined using an automatic nitrogen analyzer (FP 528 LECO, USA) based on the Dumas method. Fat content was analysed according to Flynn and Bramblet (1975).

The ability of the uncooked product to retain moisture was determined in triplicate according to Hughes et al. (1997) with modifications. 10 g batter was weighed (W₁), placed into glass jars and heated in 90°C water bath for 10 min. After cooling to room temperature, the samples were wrapped in cotton cheesecloth and centrifuged at 1400 rpm for 15 min and weighed again (W₂). Water-holding capacity (WHC) was calculated from the equation below:

The weights of chicken patties before and after cooking were recorded and the cooking yield was determined by calculating weight differences for samples before and after cooking.

The moisture retention value represents the amount of moisture retained in the 100 g cooked product and was determined according to an equation described by El-Magoli et al. (1996).

Fat retention was examined according to Murphy et al. (1975) and calculated as follows:

The diameter of each chicken patties were measured before and after cooking with a digital caliper. Change in the chicken patties' diameters were determined using the following equation (Modi et al., 2004):

Texture profile analysis (TPA) was performed five times for each treatment using a texture analyzer (TA-XT2, Stable Micro Systems, UK). Samples (1.5 cm × 2 cm × 2 cm) were taken and compressed to 50% of their original height with a crosshead speed of 5 mm/s and 50 kg load cell. The parameters calculated from the force and time curves were hardness (maximum force required for the initial compression as N), cohesiveness (ratio of active work done under the second compression curveto that done under the first compression curve as dimensionless), springiness (distance of the sample recovers after the first compression asmm), gumminess (the strength of internal bonds making up the body of the sample as N) and chewiness (the required work tomasticate the sample as N × mm).

Three sessions were conducted for sensory evaluation. In each session, sensory evaluation of cooked patties was performed by ten panelists who are post-graduate students in Food Engineering Department of Ege University. Chicken patties were labelled with 3-digit random numbers and served in random order to assessors in individual booths. A nine-point scale was used where 1 represented = dislike extremely and 9 = like extremely. The patties were served as warm (~38°C), sugar and salt free bread and water were used to clean the palate between samples. Panelist evaluated for appearance, texture, oiliness, flavor, and overall acceptability.

One-way analysis of variance (ANOVA) was used to evaluate the statistical significance (p<0.05) of the effect of chickern patties formulations, using the SPSS for Windows statistical package program (IBM, version 21.0, USA). The data was analyzed by using general linear model procedure (GLM). Least square differences (LSD) were used to compare mean values of formulations and significant differences (p<0.05) between chicken patties formulations were identified by Duncan multiple test.

Better understanding the behaviour of pre-emulsions in meat systems is important to guarantee the quality of the end product which they are added (Serdaroğlu et al., 2016a). The characteristics of GE are shown in Table 2. The pH of GE was 5.40. CIE L*, CIE a* and CIE b* parameters of GE were recorded as 83.72, 3.14 and 16.29, respectively. Syneresis is an important parameter for emulsions and it effects characteristics of product such as stability and cooking yield. In our study syneresis value is 13.88% which is similar to our previous work (Serdaroğlu et al., 2016a). Interaction of gelatin and inulin with gel matrix helped GE to show stability against centrifugation forces, no phase separation was observed after centrifugation and protected its stability at different temperatures (4°C for 48 h, 25°C for 24 h). High thermal stability was recorded in GE (93%), also creaming stability results showed that GE protected its stability without any turbidity and separation of the layer up to 7 d at 4°C.

Chemical composition and pH values of raw and cooked samples are presented in Table 3 and 4, respectively. The differences of formulation resulted significant changes in moisture, fat and ash content of raw samples (p<0.05) while no effect was recorded in protein content (p>0.05). The highest moisture content was found in G100 where beef fat was completely replaced with GE due to the presence of water in GE. Addition of GE showed decreasing effect on fat content of raw samples and met the targeted levels, also increasing GE addition more than 25% significantly reduced ash content (p<0.05). pH values of raw samples were found between 6.05 and 6.12, increasing GE concentration (p<0.05) resulted slight decreament in pH since olive oil has lower pH than beef fat.

Cooking process increased pH, protein and ash contents of samples while decreased moisture content due to cooking loss. Addition of GE effected chemical composition and pH of cooked samples (p<0.05). Moisture content of C, G25 and G50 were found similar with each other while G100 had significantly lower moisture content (p<0.05). The highest protein content was observed in G100 as consequence of the high amount of water loss due to heat treatment, and showed significant differences with other samples (p<0.05). Similar findings were observed by Poyato et al. (2015) in burger patties. Fat content of C and G100 was found similar with each other and significantly different than G25 and G50 (p<0.05). pH values of cooked samples were found between 6.14 and 6.21.

Water-holding capacity (WHC), which is defined as the ability of meat to retain moisture, is one of the most important parameters in determination of emulsion stability. WHC results of samples are shown in Table 5. WHC was found affected by the addition of GE (p<0.05), C and G50 samples showed similar WHC while G100 found the lowest probably due to the lower pH value in this sample. Differences in WHC values can be attributed to the consistence of water in GE. Osburn et al. (1999) indicated that the protein gel prepared with connective tissue can be a potential water binder for low-fat meat products and it has also synergistic effect on water binding when myofibrilar proteins are in the system. To obtain this effect, gelatin concentration must be between 0.5-3.0 g/100 g (Stevens, 2010). Also, WHC could be affected by properties of inulin, in case added inulin has large particles it improves hydration and fat absorption capacity in meat systems (Lopez-Lopez et al., 2010).

Cooking characteristics such as cooking yield, moisture and fat retention, diameter reduction (Table 5) are some of the most important factors for food industry to predict the behavior of products during cooking. The highest cooking yields were observed in C and G50 samples while the lowest was observed in G100 sample (p<0.05). It was reported that higher inulin concentration can have negative impact on cooking yield (Afshari et al., 2015). High amount of fat and also having GE in formulation resulted in lower cooking yield, moisture and fat retention in G25 treatment since there is an inverse proportion between fat level and free space between fat cells. It was reported that decreasing free space between fat cells might cause coalescing and leaking of fat from the products (Lopez-Lopez et al., 2011). When gelatin is used at an appropriate concentration in meat emulsions, it acts as a stabilizer; promotes cooking yield, reduces fat and water losses due to its gelling ability. Inulin, as an another constituent of GE, can also absorb liquid in the products and promotes fat retention. Depending on aforementioned properties of gelatin and inulin, beef fat replacement at a level of 50% with GE improved cooking yield and G50 samples showed similarity with control patties. The lowest cooking yield was observed in G100 despite it had the lowest fat level. Having the highest GE addition and the lowest moisture retention result is the probable reason for the lowest cooking yield in G100. Another reason for lower cooking yield could be high gelatin percentage since high level of gelatin could melted out and could not interact with protein in G100.

Moisture retention in ground meat products is an important cooking parameter, since retained moisture in the product effects eating quality. Moisture retention results of samples showed similarity with cooking yield results. The highest moisture retention was found in G50 among GE added samples (p<0.05) and showed similarity with C sample. This could explain the fact that in G50 treatment inulin might create hydrogen bounds with water and keep the moisture in the meat matrix. Another possible reason for this phenomena is the interaction of gelatin with inulin and water.

Retaining fat within the matrix of meat products during processing is necessary to ensure sensory quality and acceptability. Improvement in fat retention in GE addedsamples could be attributed to the stabilizing effects of the oil in the established emulsion system.This might be due to the increased concentration of inulin and gelatin by the addition of increasing amount of GE. Inulin might interact with the proteins of patty matrix and reduce migration of fat from products (Anderson and Berry, 2001). The lowest fat retention was found in C sample since it has higher fat content and due to melting of fat globules higher leakage was observed during cooking.

A dimensional change is one of the most important alterations of patties which can be affected by incorporation of new ingredients. Protein denaturation, moisture and fat release of products are some of the main diameter reducing effects during cooking (Soltanizadeh and Ghiasi-Esfahani, 2014). In this research, the lowest reduction in the diameter was observed in C samples and showed significant differences with GE added samples (p<0.05). The reason for the higher diameter reduction in GE added samples could be the result of swelling and gel forming characteristics of inulin. Swelling of the inulin and gelatin molecules in meat protein matrix resulted swelling up in patties during cooking and flat shape of patties turn into round. Afshari et al. (2015) reported that the highest diameter reduction was observed when inulin (8%) added to low-fat beef burgers.

Color is one of the most essential factors on consumer’s attitude toward meat and meat products. The color parameters of the samples were shown in Table 6. Results showed that GE addition significantly affected CIE L* and CIE b* values (p<0.05) while no effect was observed in CIE a* values. The highest CIE L* value was observed in G50 treatment which kept GE well in the sample matrix, due to lighter color of inulin. Large beef fat droplets absorbed light more than small droplets in GE and that caused the lowest CIE L* value in C samples. Adding GE caused higher CIE b* values as a result of color difference between beef fat and olive oil which has yellowish-green color (Delgado-Pando et al., 2011; Pintado et al., 2015a, Pintado et al., 2015b; Poyato et al., 2014, Serdaroğlu et al., 2016a).

The results of texture profile analysis (TPA) are presented in Table 7. GE addition affected all of the textural properties of chicken patties (p<0.05), the observed differences in textural parameters can be attributed to the different effcets of inulin and gelatin as well as olive oil. Increasing GE concentration in formulation decreased the hardness, gumminess and chewiness values. Different characteristics and behaviours of beef fat and GE was the probable cause of obtained results in texture parameters. Increasing water percentage could cause softer texture while protein amount is constant (Jimenez-Colmenero et al., 1996).

Besides, the dilution effect of non-meat ingredients in meat protein systems primarily responsible for softer texture. Álvarez and Barbut (2013) studied the effects of inulin and reported that the addition of inulin resulted in a creamy and softer product. Replacing beef fat with GE significantly affected springiness and cohesiveness values (p<0.05) while the lowest springiness and cohesiveness values were observed in G50. Gumminess and chewiness of samples showed similar trend with hardness and all of the treatments showed significant differences (p<0.05).

One of the limiting factors for fat reducing strategies is sensory properties due to the functions of fat in meat products. The results of sensory analysis are shown in Fig. 1. In general terms, the scores awarded by the panelists were similar in all the treatments except G100. Replacing all of the beef fat with GE showed negative impact on all investigated sensory characteristics of chicken patties and G100 samples received the lowest scores. Flavor parameter could be affected by the existince of beef fat. Even the beef fat was reduced to half, it gave characteristic flavor to the samples. Negative effects of replacing 100% of the animal fat with GE on sensory characteristics have been reported in other researches (Pintado et al., 2015a, Pintado et al., 2016).

Fig. 1. Sensory properties of chicken patties.

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As a result, all the treatments were accepted by panelists in term of overall acceptibility. Besides, these results showed that GE addition up to 50% can be good reformulation strategy to obtain chicken patties similar to original product.