Quality and Sensory Characteristics of Reduced-fat Chicken Patties with Pork Back Fat Replaced by Dietary Fiber from Wheat Sprout

Wheat (Triticum aestivum L.) sprouts were obtained from local market, Seongnam, Korea. Raw buckwheat sprouts were washed three times with four volumes of water (25℃). The cleaned buckwheat sprouts were freeze dried. The dried buckwheat sprouts were pulverized to milling systems and passed through a 35-mesh sieve (particle size of <0.5 mm). The crushed buckwheat sprouts (moisture content: 2.48%; fat content: 5.47%; protein content: 30.36%; ash content: 0.95%; dietary fiber: 39.87%; L*-value: 59.46; a*-value: −6.12; b*-value: 23.43; pH: 5.82) were then placed in polyethylene bags, packaged using a vacuum packaging system (FJ-500XL, Fujee Tech., Korea), and stored at 4℃ until used for product manufacture.

Fresh chicken breast (M. pectoralis major) and pork back fat (moisture 12.78%, fat 85.42%) were purchased from a local processor. These chicken breast and pork fat were ground through an 8-mm plate, and then ground through a 3-mm plate. Each batch of samples consisted of seven chicken patties with different fat levels (10%, 15%, and 20%) and buckwheat sprout powder (0%, 1%, and 2%). Chicken patties were produced using the traditional recipe (Choi et al., 2012). The mix of chicken patty was kneaded for 15 min at 4℃ by hand. The chicken patty mixtures were divided into seven equal portions (Table 1). Each portion was kneaded for an additional 15 min to obtain homogeneous mixtures. These mixtures shaped with a household hamburger mold (PM 10/13 Burger press, AB Services Food Machinery, England; diameter: 10.0 cm, thickness: 2.3 cm) into meat products with a weight of about 90 g. Chicken patties were cooked on a preheated grill (CG20, USA) at grill surface temperature of 150℃. They were cooked for 3 min on one side and 3 min on the opposite side until the targeted core temperature reached 75℃. The core temperature of the pork patties was monitored with a digital thermometer (Tes-1305, Tes Electrical Co., Taiwan) equipped with a data logger (RS-232, Tes Electrical Co., Taiwan) by inserting an iron constant an thermocouple.

The moisture content (950.46B, Oven drying method), fat content (960.69, Soxhlet method), protein content (981.10, Kjeldahl method), and ash content (920.153, Muffle furnace method) of the chicken patties were determined using an AOAC (2000).

The caloric contents were obtained by the Mansour and Khalil (1999) method. Total calorie estimates (kcal) for chicken patties were calculated on the basis of a 100 g portion using At water values.

The pH values of raw and cooked chicken patties were measured in a homogenate (Ultra-Turrax T25, Janke & Kunkel, Germany) prepared with 5 g of sample and distilled water (20 mL) using a pH meter (Model 340, Mettler-Toledo GmbH, Switzerland).

The color of each raw and cooked chicken patty was determined using a colorimeter (Minolta Chroma meter CR-210, Minolta Co., Japan; illuminate C, calibrated with a white plate, L*=+97.83, a*=−0.43, b*=+1.98). The lightness (CIE L*-value), redness (a*-value), and yellowness (b*-value) values were recorded.

Cooking loss was determined by calculating the weight differences before and after cooking as follows:

Cooking loss (%) = [(weight of raw chicken patty (g) − weight of cooked chicken patty (g)) / weight of raw chicken patty (g)] × 100

The diameter and thickness of the raw and cooked patties were recorded using vernier calipers (530-122, Mitutoyo, Japan) and calculated using the following expression.

Reduction in diameter (%) = [(raw chicken patty diameter − cooked chicken patty diameter) / raw chicken patty diameter] × 100

Reduction in thickness (%) = [(raw chicken patty thickness − cooked chicken patty thickness) / raw chicken patty thickness] × 100

Shear force was performed at room temperature with a texture analyzer (TA-XT2i, Stable Micro Systems Ltd., England). Chicken patty samples were taken from the central portion of each meat patty. Prior to analysis, samples were allowed to equilibrate to room temperature (20℃, 3 h). Each patty was cut with a knife into 5.0 cm (L) × 2.5 cm (W) × 2.0 cm (D) and the sections were sheared in two separate locations with a Warner-Bratzler blade set attached to a texture analyzer. Test speed was set at 2 mm/s. Data were collected and analyzed to determine shear force values and the maximum force required to shear through each sample (Bourne, 1978).

The sensory evaluations were performed in triplicate on each sample by sensory panelist. Training of panelists was performed according to sensory evaluation procedure (Lawless & Heymann, 1999). Each chicken patty was evaluated in terms of color, flavor, juiciness, tenderness, and overall acceptability. Chicken patties were cut into quarters (size: 5.0 × 5.0 × 2.0 cm), and served to the panelists randomly. The color (1 = extremely undesirable, 10 = extremely desirable), flavor (1 = extremely undesirable, 10 = extremely desirable), tenderness (1 = extremely tough, 10 = extremely tender), juiciness (1 = extremely dry, 10 = extremely juicy), and overall acceptability (1 = extremely undesirable, 10 = extremely desirable) of the cooked samples were evaluated using a 10-point descriptive scale. This analysis was conducted using the hedonic test described.

All tests were done at least three times for each experimental condition and mean values are reported. An analysis of variance was performed on all the variables using the general linear model (GLM) procedure of the SAS (Statistical Analysis Systems Institute, 2011) statistical package. Duncan’s multiple range test (p<0.05) was used to determine the differences between treatment means.

Proximate compositions of reduced-fat chicken patties formulated with different amounts of fat and wheat sprout are shown in Table 2. The moisture content of reduced-fat chicken patties was higher than that of control patties with regular-fat level. Moisture content was increased significantly when fat level was reduced from 20% to 10% because reduced fat samples had less fat and more water. Protein content of chicken patties ranged from 16.48% to 18.58%. The protein content was slightly decreased when wheat sprout level was increased from 0% to 2%. Fat contents in chicken patties formulated with reduced-fat and wheat sprout were significantly (p<0.05) lower than those of control patties. Ash contents of reduced-fat chicken patties samples containing wheat sprout were higher than those of the control patties. Ash content was significantly (p<0.05) increased when wheat sprout level was increased from 0% to 2%. Similar trends in proximate composition have been reported in studies of Choi et al. (2012) when Laminaria japonica is added to reduced-fat pork patties. They have reported that reduced-fat pork patties containing Laminaria japonica have significantly higher moisture contents and ash contents than control patties while protein content and fat content of control samples with regular-fat level are higher than reduced-fat pork patties containing Laminaria japonica. Choi et al. (2014b) have reported that the proximate composition of reduced-fat frankfurters is supported by dietary fiber extracted from makgeolli lees. They have indicated that the moisture and ash contents in reduced-fat frankfurters containing makgeolli lees fiber are higher than those in control frankfurters with regular-fat level. They have closely approximated targeted fat concentration for the samples. An (2015) has reported that the moisture content of foods containing wheat sprout are higher than those in the control due to the fact that wheat sprout contains 37% dietary fiber. According to Choi et al. (2008), emulsion-type sausages with dietary fiber from rice bran have higher moisture and ash contents than control sausages without rice bran fiber. That is, depending on dietary fiber sources, the proximate composition of meat products can be different.

Energy values of reduced-fat chicken patties formulated with different fat levels and wheat sprout were significantly (p<0.05) lower than those of controls. When wheat sprout concentration was increased from 0% to 2% with fat level reduced from 20% to 10%, the energy values of reduced-fat chicken patties were decreased significantly (p<0.05). This was due to the fact that reduced-fat treatments had fat replaced by water and wheat sprout. Similar trends in energy values have been observed by Choi et al. (2012). It has been reported that meat patties with reduced-fat containing Laminaria japonica fiber have less energy values than control patties with regular fat level due to the fact that reduced-fat treatments samples have less fat but more water and dietary fiber sources (Choi et al., 2012). Cengiz and Gokoglu (2005) have reported that frankfurters with reduced fat and fat replacer have lower energy values because energy values can be affected by fat replacer levels and water content. Some researchers have reported that energy values of meat products were depend on added fat levels because fat has 9.0 kcal of energy per / gram (Choi et al., 2010; Salcedo-Sandoval et al., 2012).

The pH and color of reduced-fat chicken patties with various fat levels and 1% or 2% of wheat sprout are shown in Table 3. The pH values of uncooked and cooked chicken patties samples were the highest in control. Increased wheat sprout levels were associated with decreased pH values of uncooked and cooked chicken patties in samples with the same fat level. Increasing fat level from 10% to 20% significantly increased the pH values of uncooked and cooked chicken patties, indicating that the pH values of meat products could be affected by fat levels and wheat sprout levels. These results may be due the addition of wheat sprout whose pH was 5.82. Our results are in agreement with An (2015) who has reported that the pH values of food formulated with wheat sprout powder are lower than those of the control. Chung and An (2015) have reported that increasing wheat sprout levels can significantly decrease pH value because the pH values of products are affected by the pH of wheat sprout powder. Similar results have been reported by Choi et al. (2015) that the pH values of frankfurters with increasing fat levels in samples are slightly increased.

The differences in CIE L*-values (lightness), CIE a*-values (redness), and CIE b*-values (yellowness) of uncooked and cooked low-fat chicken patties containing different levels of wheat sprout were significant (Table 3). In samples with the same fat level, increasing wheat sprout levels were associated with decreased lightness and redness of uncooked and cooked low-fat chicken patties samples. This could be due to the effect of wheat sprout color. Decreasing fat level from 20% to 10% significantly (p<0.05) decreased the lightness and redness values of uncooked and cooked chicken patties. The yellowness values of uncooked and cooked low-fat chicken patties samples were significantly (p<0.05) increased when wheat sprout level was increased in samples with the same fat level. The yellowness value of uncooked chicken patties was increased when fat level was decreased. The yellowness values of cooked chicken patties were not significantly different from each other at different fat levels. According to Chung and An (2015), food with increasing wheat sprout levels have significantly decreased lightness and redness values but increased yellowness values. This might be due chlorophyll in wheat sprout. Similar results on color changes have been reported by Park (2015) on the quality characteristics of muffins with sprout concentrate added. Crehan et al. (2000) have indicated that reducing fat concentrations can lead to significant decrease in lightness and yellowness of meat products. These results are in agreement with those of Choi et al. (2015). They have found similar trends of color change for frankfurters with different fat levels (5%, 12%, and 30%) (Choi et al., 2015). Hand et al. (1987) have also reported that the lightness values of high fat frankfurters are greater than those of low fat frankfurters.

Results of cooking loss, reduction in diameter, and reduction in thickness of reduced-fat chicken patties formulated with various fat and wheat sprout levels are shown in Table 4. The cooking loss was the highest in reduced-fat chicken patties containing 10% fat. When fat levels and wheat sprout levels were increased, the cooking loss was decreased. These results are in agreement with Choi et al. (2015) who have reported similar trend of cooking loss for frankfurters containing different fat levels (5%, 12%, and 30%) and 2% rice bran fiber. Choi et al. (2012) have reported that the cooking loss of reduced-fat patties containing L. japonica powder is significantly lower than that of control patties with regular-fat level. They have also reported that a reduction in fat content can cause significant increase in cooking loss compared to low-fat control due to the fact that these samples initially have more water contents than the controls. This is most likely due to the fact that dietary fiber sources have high water holding capacity and binding capacity. Lee et al. (2008) have reported that low-fat meat products without containing dietary fiber have the highest cooking loss during heating. Some researchers have reported that the addition of dietary fiber sources can decrease cooking loss in meat products (Choi et al., 2010; Hughes et al., 1997; Kim et al., 2013; Turhan et al., 2005). This is because cooking loss occurs through releasing fat and moisture. Cooking loss is related to the binding ability among meat protein, fat, and moisture. The differences in reduction in diameter and thickness of low-fat chicken patties formulated with various fat levels and wheat sprout levels were significant (Table 4). The reduction in diameter and thickness was decreased when fat contents and wheat sprout levels were increased. The reduction in diameter and thickness of low-fat chicken patties exhibited results similar to cooking loss. These results are consistent with those of Choi et al. (2012) who have reported that the reduction in diameter and thickness of reduced-fat pork patties containing dietary fiber is significantly lower than that of control samples due to that fact that reduced-fat patties during cooking could improve the binding and stabilizing properties of dietary fiber. These results are also in agreement with the results of a study conducted by Turhan et al. (2005) on low-fat beef burgers made with various concentrations of hazelnut pellicle. Kim et al. (2013) have reported that pork patties containing brewer’s spent grain dietary fiber have lower reduction in diameter and thickness because dietary fiber has high water holding capacity and binding capacity. Thus, improving water holding capacity and binding capacity of meat patties can decrease the reduction in diameter and thickness by reducing the deformation of patties during cooking.

The shear forces of reduced-fat chicken patties formulated with various fat levels and wheat sprout levels are shown in Fig. 1. The shear forces of reduced-fat patties were decreased when fat levels were increased. The shear forces of reduced-fat chicken patties with wheat sprout were decreased when wheat sprout levels were increased. Similar results have been reported by An (2015) who has demonstrated the effect of wheat sprout on foods. These results indicate that increasing wheat sprout level can decrease the hardness of cookies due to the water holding capacity of wheat sprout. Choi et al. (2011) have reported that chicken meat patties added with lotus leaf powder have lower values of hardness compared to control patties. An et al. (2010) has reported that the shear forces of meat products are gradually decreased in dietary fiber content. For these reasons, shear force needs to be changed in meat products because shear force is related to water holding capacity, moisture content, and cooking yield. However, Choi et al. (2014a) have reported that reduced-fat sausages with increasing pre-emulsion of brewer’s spent grain levels have increased hardness. They have also reported that these improvements in textural properties might be due to dietary fiber because it has abilities of binding water and fat absorption. Previous studies have found that fat levels and dietary fiber can affect the textural properties of meat products (Kim et al., 2013; Turhan et al., 2005).

Fig. 1. Effect of wheat sprout on shear force of reduced-fat chicken patties.¹⁾Control, 20% fat; T1, 15% fat; T2, 15% fat + 1% wheat sprout; T3, 15% fat + 2% wheat sprout; T4, 10% fat; T5, 10% fat + 1% wheat sprout; T6, 10% fat + 2% wheat sprout. a-e the different letters within shear force are significantly different (p<0.05).

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The sensory scores of reduced-fat chicken patties with different fat and wheat sprout levels are summarized in Table 5. The color and flavor scores of control samples were significantly (p<0.05) higher than those of reduced-fat chicken patties containing wheat sprout. The tenderness and juiciness scores of samples were not significantly (p>0.05) different from those of the controls. The overall acceptability was the highest for the control patties and patties containing 15% fat and 2% wheat sprout (T3). Similar results have been obtained by Choi et al. (2012) on the sensory characteristics of reduced-fat pork patties. These results have revealed that the overall acceptability of reduced-fat pork patties containing 1% or 3% dietary fiber is the highest. According to Bloukas et al. (1993), dietary fiber has beneficial influence on the sensory quality of reduced-fat pork products. Choi et al. (2015) have reported that the overall acceptability scores of reduced-fat frankfurters with rice bran fiber are significantly higher than those without fiber added. There is no significant difference in acceptability among samples with various fat levels (Choi et al., 2015). Chung and An (2015) have reported that sensory evaluation scores in terms overall preference of groups containing 3% and 6% of wheat sprout are not significantly different from each other or higher the control. Thus, reduced-fat and low-fat meat products may be produced through addition of dietary fibers to improve their sensory characteristics so that they are acceptable to consumers.