Evaluation of chicken nugget properties using spent hen meat added with milk fat and potato mash at different levels

Abstract

This study was aimed to develop chicken nuggets using spent hen meat (SHM) added with milk fat (MF) and potato mash (PM) at different levels. Four different spent hen nuggets (SHNs) i.e. T1 (75% SHM with 5% MF), T2 (70% SHM with 8% MF and 2% PM), T3 (65% SHM with 11% MF and 4% PM), and T4 (60% SHM with 14% MF and 6% PM) were formulated and compared with the control, using broiler chicken meat without MF and PM. The control, T1, and T2 were not significantly different with respect to protein and fat contents. The emulsion stability (92.2%), frying yield (84.1%), hardness (19.2 N) and chewiness (11.4 N) of T2 were similar to the control. The incorporation of MF and PM resulted in increased taste and flavor scores for SHN. The overall acceptability score was same for the control and T2. The conjugated dienes and thiobarbituric acid-reactive substance results showed that the addition of MF at 8 to 10% did not have an effect on the oxidative stability of SHN during storage. MF-incorporated SHN may be a regular chicken nugget for all consumers due to improved texture and sensory quality with similar fat content to the control.

Electronic supplementary material

The online version of this article (10.1007/s13197-020-04787-7) contains supplementary material, which is available to authorized users.

Introduction

Consumers’ demand for breaded and battered foods such as chicken nuggets has been increasing widely because of favorable sensorial characteristics, inexpensive, and longer storage life (Rahimi et al. 2018). Generally, chicken nuggets are prepared using broiler chicken meat because of its high carcasses, better tenderness and other quality characteristics when it is compared to the spent hen meat (SHM) (Bhosale et al. 2011). However, broiler chicken meat is a principal source of meat proteins and has a good demand with economic importance for direct consumption as meat throughout the world (Sabikun et al. 2019).

Globally, the egg industries produce a significant amount of spent hens. At the end of laying cycles, spent hens are mostly underutilized and used in very low priced minced products (Chuaynukool et al. 2007). The high toughness due to the collagen content and cross linkages prevents spent hens being used in whole meat foods and decreases the market value in many countries like Korea, Taiwan, Japan, and the United States (Chueachuaychoo et al. 2011; Lee et al. 2003). In addition, spent hen meat remains tough and fibrous even after cooking using high pressure for a long time (Mendiratta et al. 2012). However, SHM is a good protein source, and is a rich source of omega-3 fatty acids and low cholesterol (Lee et al. 2003). Thus, an efficient utilization of SHM for the preparation of comminuted meat products such as cutlets or nuggets may be a good economical support for the egg industries. In addition, the chicken nuggets using SHM (SHN) could be a good source of proteins, and unsaturated fatty acids particularly omega-3 fatty acids.

Several researchers have studied the developement of chicken nuggets using SHM added with different ingredients such as ground carrots and sweet potato mash (Bhosale et al. 2011) and amla (Emblica officinalis) fruit juice powder (Mahajan et al. 2017). However, to the best of our knowledge, there is no study related to the quality characteristics of SHN added with milkfat (MF) and boiled potato mash (PM) and compared with conventionally prepared broiler chicken nugget. Thus, in order to increase the acceptability particularly texture and sensory attributes of SHN, the MF and PM were incorporated at different levels by substituting SHM. Potato is a widely consumed vegetable, and PM contribiutes good functional properties such as consistency, increased water/oil absorption capacity, and good textural attributes to food products (Pęksa et al. 2002). MF is widely used in tropical regions of the world, particularly in South Asian countries for increasing the texture, emulsifying properties and sensory attributes in different food products (Pęksa et al. 2002; Chandan 2011). Moreover, MF is unique with natural fat imparting a good flavor and taste in processed food products, and is widely available. It has a high melting point and greater stability (Chandan 2011; Dhurvey et al. 2012).

Therefore, the objective of this study was to utilize SHM by developing SHNs added with MF and PM at different levels. The quality properties such as chemical composition, emulsion stability, frying yield, water loss and oil absorption capacity, color parameters, texture profile, sensory attributes and oxidative stability of SHN were evaluated and compared with control prepared using broiler chicken meat without MF and PM.

Materials and methods

Sample preparation

Broiler chicken (6 weeks) and spent hens (50 weeks) were purchased from a local commercial poultry farm. They were transferred to the Meat plant at Gyeongsang National University and slaughtered by commercial slaughtering method. Feather, skin and excessive fat were removed and the carcasses were washed by tap water. After deboning, meat and fat were packaged in separate polyethylene bags and stored at − 20 °C till further use. MF (99.9% fat content), potato (Golden wonder) and all other ingredients were purchased from local market in Jinju, Korea.

Preparation and processing of nuggets

Five different nuggets (5 kg batches for each treatment) were prepared in triplicate. The formulations for control (using broiler chicken meat) and four SHNs (T1, T2, T3, and T4) are presented in Table 1. The potatoes (2 kg) were washed by tap water. Next, they were placed into a pressure cooker and boiled until soft (~ 15 min) by a gas burner. After peeling, boiled potatoes were mashed by a stainless steel potato masher. Required amounts of lean meat, chicken fat, MF, and PM were kept at 4 °C for 24 h prior to the preparation of meat batter. The lean meat, chicken fat, MF and PM were ground separately with a grinder (Magimix, Model No. 3100, France), and then homogenized for 2 min with all ingredients according to the formulations to obtain meat batter. Approximately 20 g of the resulting batter (raw nugget) was first dipped for 15 s in the batter (25 °C) consisted of the dry mixture and water (5:3 w/v). The dry mixture contained wheat flour (94%), salt (1%), baking powder (2.5%) and black pepper powder (2.5%). In order to drip out the excessive batter, the battered nuggets were vertically maintained for 10 s at room temperature (25 °C). The prepared nuggets were deep-fat fried using soybean oil at 180 °C for 4 min, placed in plastic bags and stored at 4 °C for subsequent analysis.

Table 1.

Formulation of the control and those of the chicken nuggets using spent hen meat added with milk fat (MF) and potato mash (PM) at different levels

Ingredients (%)	Control	T1	T2	T3	T4
Broiler chicken meat	80	–	–	–	–
Spent hen lean meat	00	75	70	65	60
Chicken fat	10	10	10	10	10
Milk fat (MF)	–	5	8	11	14
Potato mash (PM)	–	–	2	4	6
Wheat flour	3.5	3.5	3.5	3.5	3.5
Onion, garlic, ginger	5.0	5.0	5.0	5.0	5.0
Sodium triphosphate (STPP)	0.2	0.2	0.2	0.2	0.2
NaCl	0.7	0.7	0.7	0.7	0.7
Spices	0.4	0.4	0.4	0.4	0.4
Egg yolk	0.2	0.2	0.2	0.2	0.2

Control: Broiler chicken nugget prepared without MF and PM

T1, T2, T3, and T4: Chicken nuggets using different levels of MF and PM by replacing spent hen lean meat

Proximate composition and frying yield of different nuggets

The proximate composition of control and SHNs, including moisture, protein, crude fat, and ash contents, was measured by AOAC (2000) methods. Frying yields of all nuggets were determined gravimetrically following Eq. 1, and the method described by Bhosale et al. (2011).

$$\text{Frying}\text{yield}\left(\text{g}100{\text{g}}^{-1}\text{nugget}\right)={\text{W}}_2/{\text{W}}_1\times 100$$ 1

where W₁ is the weight of nugget before frying, W₂ is the weight of fried nugget.

Emulsion stability

Emulsion stability (ES) of nuggets was determined following the method described by Tamsen et al. (2018) with some modifications. The raw nugget (25 g) was placed in a pre-weighed heat proof screw cap tube. The tube containing nugget was heated at 80 °C using water bath for 30 min followed by centrifugation for 10 min at 1200 rpm. Then, the tube was turned upside down for 30 min into a pre-weighed crucible to release the fluids. The ES was calculated using Eq. 2.

$$\text{ES}\left(\text{g}100{\text{g}}^{-1}\text{nugget}\right)=(\text{W}-{\text{W}}_1)/\text{W}\times 100$$ 2

where W is the weight of sample, W₁ is the weight of released fluids.

Determination of water loss and oil absorption capacity

Water loss (WL) or oil absorption capacity (OAC) of nuggets was determined by measuring the amounts (g) of water and fat of the same nuggets before (W₁) and after (W₂) frying according to AOAC (2000) method. The weight of the same nugget sample was different before (about 20 g) and after (16–17 g) frying. Therefore, the sample weight (W) was normalized by the weight of the raw nugget. The WL and OAC were calculated with Eqs. 3 and 4 respectively, and the results were expressed as g WL or OAC per 100 g nugget.

$$\text{WL}\left(\text{g}100{\text{g}}^{-1}\text{nugget}\right)=({\text{W}}_1-{\text{W}}_2)/\text{W}\times 100$$ 3

$$\text{OAC}\left(\text{g}100{\text{g}}^{-1}\text{nugget}\right)=({\text{W}}_2-{\text{W}}_1)/\text{W}\times 100$$ 4

Color parameters

The external color parameters of the nuggets were measured using a digital colorimeter (Minolta CR-300, Minolta Co., Japan) with an 8 mm aperture, a D₆₅ illuminant, a 2 °C Closely matches CIE 1931 Standard observer, and ф8 mm/ф11 mm measurement area. A standard white plate (Y = 93.5, x = 0.3132, y = 0.3198) was used to calibrate the colorimeter before measurement. The nugget samples were kept on tissue papers for 30 min at room temperature to avoid the influence of surface oil. Next, they were placed on a spectral glass Petri dish for the measurement of color parameters. The polar co-ordinate chroma, (C*), and total color differences (ΔE) were calculated using Eqs. 5 and 6, respectively, according to the method adopted by Rahman et al. (2018). The color parameters results were expressed as CIE (Commission International de l’Eclairage) L*, a*, b*.

$$C^{\ast }=\sqrt{a^{\ast 2}+b^{\ast 2}}$$ 5

$$\mathrm{\Delta }\text{E}=\sqrt{{\left(L_0^{\ast }-L^{\ast }{)}^2+{\left(a_0^{\ast }-a^{\ast }\right)}^2+(b_0^{\ast }-b^{\ast }\right)}^2}$$ 6

where ΔE was considered between control (indicated by index 0) and SHNs.

Texture profile analysis

Texture profile analysis (TPA) of different nuggets prepared in this study was carried out using a Sun Rheometer (Compact-100 II, Sun Scientific Co., LTD., Tokyo, Japan). Samples were cut into cubes (1.5 × 1.5 × 1.5 cm) from the central portion of nuggets and allowed to equilibrate at room temperature for 30 min. The cut nuggets were compressed twice to 60% of their original height using a flat adaptor (D: 25 mm). Force–time deformation curves were obtained with a 10 kg load range at a crosshead speed of 60 mm/min. TPA parameters in terms of hardness (N), cohesiveness, springiness (cm) and chewiness (N) were calculated based on the force–distance response by the method of Bourne (1978).

Sensory evaluation

A trained twenty-member panel consisting of students and researchers of the Department of Animal Sciences at Gyeongsang National University, Republic of Korea evaluated the sensory attributes. The panelist selection was carried out according to Lawless and Heymann (1999), adopted by Rahman et al. (2019b). Different nuggets were cut into small pieces (2 cm × 2 cm × 2 cm), and marked using random code numbers and placed on a glass container (Pyrex^®, Charleroi, PA, USA), allowed for 30 min at room temperature and then distributed to the panelists randomly. They judged each nugget sample in triplicates under fluorescent lighting. The drinking water was given to the panelist along with the nuggets for rinsing their mouth in between every sensory evaluation. The sensory attributes such as color, flavor, juiciness, taste, chewiness and overall acceptability of nuggets were judged using a 9–point hedonic scale ranging from extreme dislike (score = 1) to the extreme like (score = 9).

Lipid oxidation

1. Conjugated dienes

The conjugated dienes (CD) of the control and SHNs stored at 4 °C for 14 days were measured according to the method described by Roldan et al. (2014), with some modifications. Nugget samples were cut with a knife in small cubes, immersed in liquid nitrogen and minced. Next, 0.5 g sample was suspended in distilled water (5 mL) and homogenized. An aliquot (0.5 mL) of this slurry was mixed with 5 mL solvent mixture (3:1 (v/v) hexane/isopropanol) and stirred for 1 min. Then the mixture was centrifuged at 3500 rpm for 5 min. The supernatant was read at 233 nm for absorbance using a UV–Vis spectroscopy (Agilent 8453, USA). The CD concentrations of different samples were calculated with the molar extinction coefficient of 25,200 M⁻¹ cm⁻¹ and the results were expressed as mmol/kg sample.

• (b)Thiobarbituric acid-reactive substance (TBARS)

The TBARS values of the control and SHNs stored at 4 °C for 14 days were measured following the method described by Sabikun et al. (2019) with minor modifications. The analysis was carried out on 1th, 7th, and 14th, days of storage. The nugget sample (5 g) was mixed with 15 mL of 0.1 M phosphate buffer (pH 7.0) followed by homogenized for 2 min. A 1 mL of supernatant was placed into the glass tube, and 50 µL of butylated hydroxytoluene (BHT; 7.2% in ethanol) and thiobarbituric acid/trichloroacetic acid (TBA/TCA) solution (1.95 mL) was added. Next, the slurry was incubated for 15 min in a shaking water bath at 90 °C for reaction followed by allowing to stand at room temperature for cooling. Then the solution was filtered through a filter paper, and the supernatant was read at 532 nm using a UV–Vis spectroscopy (G1115AA, Agilant technologics, USA) against the blank containing 2 mL of TBA/TCA/HCl solution in 1 mL of deionized water without sample. TBARS values were calculated as mg of malonaldehyde (MDA)/kg sample.

Statistical analysis

The observations composing the experiment (5 nuggets × 3 batches × 3 storage periods) were statistically analyzed. All determinations were performed in triplicates and designed randomly. Data were presented as mean values ± standard error, and SAS^® (version 9.1, SAS Institute Inc., Cary, NC, USA) program was used for analyzing data. The storage data were analyzed by two-way ANOVA using the general linear model (GLM) procedure. To determine the difference of means amongest treatments Duncan’s multiple range tests (p < 0.05) were used.

Results and discussion

Proximate composition

The proximate composition of different nuggets is presented in Table 2. The control nugget had significantly higher moisture content (52.9%) as compared to those of the SHNs. Amongest the SHNs, T1 and T2 had significantly higher moisture contents with values of 51.6% and 51.3% respectively than those of the T3 (50.0%) and T4 (49.3%). According to the formulation, each nugget batch type was significantly different with respect to protein and fat contents. After frying, the control, T1 and T2 were not significantly different with respect to the protein and fat contents. But, all of them had significantly higher protein and lower fat contents compared to those for the T3 and T4. The higher protein and lower fat content could be due to the fact that of higher water and/or fat losses on frying. During frying, the water and/or fat holding capacity increased proportionaly with increasing protein and decreasing fat contents in the raw nuggets. In case of T3 and T4, a certain level of the fat was exudated on frying due to high content of fat. Kang et al. (2017) reported that protein, fat, and ash contents increased linearly with decreasing moisture content in foods, and lower proteins with higher levels of fat serve to hinder oil absorption in food products. Similar descriptions were also reported by Rahman et al. (2019b) for other meat products. The proximate composition results in our study agree with those of Chuah et al. (1998) who prepared chicken nuggets using 70 to 84.5% chicken meat with starch or other components.

Table 2.

Proximate composition (%), emulsion stability (ES), frying yield (FY), water loss (WL), and oil absorption capacity (OAC) of the control and for the nuggets using spent hen meat

Nuggets	Moisture	Protein	Fat	Ash	ES (g/100 g)	FY (g/100 g)	WL (g/100 g)	OAC (g/100 g)
Control	52.9 ± 0.3A	23.0 ± 0.5A	19.6 ± 0.4C	4.0 ± 0.2A	93.6 ± 0.3A	85.6 ± 0.7A	7.4 ± 0.2C	7.4 ± 0.3A
T1	51.6 ± 0.3B	22.6 ± 0.5A	20.0 ± 0.5C	3.3 ± 0.1B	92.9 ± 0.5A	85.2 ± 0.4A	8.6 ± 0.3B	5.3 ± 0.5B
T2	51.3 ± 0.2B	22.5 ± 0.6A	20.3 ± 0.5C	3.5 ± 0.2AB	92.2 ± 0.6A	84.1 ± 0.6A	8.8 ± 0.6B	3.5 ± 0.5C
T3	50.0 ± 0.3C	20.9 ± 0.2B	21.3 ± 0.7B	3.6 ± 0.2AB	90.6 ± 0.6B	81.6 ± 0.6B	9.7 ± 0.5A	− 0.4 ± 0.1D
T4	49.3 ± 0.2D	18.5 ± 0.3C	22.9 ± 0.5A	3.9 ± 0.2A	88.3 ± 0.4C	76.5 ± 0.4C	9.9 ± 0.1A	− 1.5 ± 0.1E

Control: Broiler chicken nugget prepared without MF and potato mash (PM)

T1, T2, T3, and T4: Chicken nuggets prepared using different levels of MF and PM by replacing spent hen meat

All values are mean ± standard error (n = 3)

Different letters (A–D) in a column indicate significant differences (p < 0.05)

Emulsion stability

The ES is related to the amount of juiciness present in the emulsified food product (Kang et al. 2017). The ES was in the range of 88.3 to 93.6 g 100 g⁻¹, while the highest value was for control and the lowest value was for T4 (Table 2). The ES of control, T1, and T2 was not significantly different and was higher (p < 0.05) than the T3 and T4, which may be due to higher protein contents. Higher protein contents could serve as surface-active agents between water/oil interfaces resulting in an increased ES under adverse conditions such as heating (Zayas 1997; Rahman et al. 2019b). On the other hand, T3 and T4 had higher levels of fat and carbohydrate (PM) with lower proteins resulting in reduced hydrophilic–lipophilic balance and ionic strength for making a stable emulsion. It was reported that emulsifying properties of food products are related to the contents of protein and fat, the processing parameters, pH, etc. (Rahman et al. 2019a). The ES values in this study are in accordance with those reported by Tamsen et al. (2018).

Frying yield

The addition of MF and PM showed a little unfavorable effect on the frying yield of SHN. The yield decreased with increasing fat contents in nuggets. The ranges of frying yield were 76.5 to 85.6 g 100 g⁻¹, and the highest yield was found for control followed by T1, T2, T3, and T4 (Table 2). However, the frying yields (g 100 g⁻¹) for T1 (85.2) and T2 (84.1) were not significantly different from the control (85.6). The lower yield for T3 and T4 may be due to lower ES resulting in increased water/oil loss on frying. It was reported that thermal treatment leads to loss of lipids from meat products containing high fat resulting in increasing cooking loss (Estévez et al. 2005). The results of frying yield are in agreement with Bhosale et al. (2011) who reported that chicken nuggets incorporated with sweet potato mash had lower proteins, ES and cooking yield.

Water loss and oil absorption capacity

The WL and OAC of the control and SHNs are presented in Table 2. T3 and T4 showed significantly higher WL (9.7 and 9.9 g 100 g⁻¹, respectively) and lower OAC (− 0.4 and − 1.5 g 100 g⁻¹ nugget, respectively) on frying compared to that of the control (WL = 7.4 g 100 g⁻¹, OAC = 7.4 g 100 g⁻¹). The WLs for T1 and T2 were not significantly different from the control. The results indicated that WL increased by frying with a decreasing protein content in raw nuggets. By contrast, OAC decreased by frying with increasing fat content in raw nuggets. The raw nugget containing high fat exudated excess lipid on frying, as a result, T3 and T4 showed lower OAC. Similarly, it was reported that high fat containing raw nuggets exudated more liquid on cooking and seem to have a negative influence on the water/oil retention capacity in the cooked nugget (Bhosale et al. 2011). Such a characteristic for chicken nugget agrees with Prinyawiwatkul et al. (1997). Khalil (2000) reported that fat was removed easily from beef patties containing high lipid due to a greater probability of encounter and expansion of fat droplets, consequently, dense meat protein matrix of low-fat ground beef retarded fat migration. Zayas (1997) reported that high proteins exposed more polar groups that can bind more liquid such as water and oil.

Color

The external color parameters of the control and SHNs were investigated at 1st, 7th, and 14th days of storage, and the results are presented in Table 3. It was observed that the lightness (L*) was increased and redness (a*) and yellowness (b*) were decreased with storage for all nuggets. The incorporation of MF and PM by replacing SHM increased L* values and decreased a* values in SHNs, which could be due to higher L* values (64.2 for MF and 63.2 for PM) and lower a* values for MF and PM (supplementary data; Table S1). The polar co-ordinate chroma (C*) value was not significantly different between control and SHNs (except T4). The color differences (ΔE) increased with increasing the storage time and the amounts of MF and PM in nuggets. Thus, at the end of storage, T4 had a significantly lower a*, b* and C* and higher ΔE compared to those for other nuggets due to increasing lightness. It was reported that L* values increased and linearly decreased a* values in deep fat fried chicken nuggets with storage time (Hwang et al. 2011). The color parameters found in this study agree with Bhosale et al. (2011) who studied the characteristics of different chicken nuggets added with sweet potato mash and ground carrot. Further, the high meat protein content leads to more myoglobin pigment resulting in increased redness, and during grinding the fat globules scatter within the protein matrix affecting the color properties (Rahman et al. 2019b).

Table 3.

Textural attributes and color parameters of control and spent hen nuggets

Storage period (d)	Nuggets	Textural attributes				Color parameters
		Hardness (N)	Cohesiveness	Springiness (cm)	Chewiness (N)	L*	a*	b*	C*	ΔE
01	Control	18.9 ± 1.3Aa	0.61 ± 0.06Aa	0.88 ± 0.04ABa	10.9 ± 1.0Ba	50.5 ± 1.01Bb	14.4 ± 0.4ABa	30.3 ± 0.6Aa	33.6 ± 0.6Aa	–
	T1	20.2 ± 1.7Aa	0.59 ± 0.12Aa	0.98 ± 0.03Aa	14.0 ± 1.0Aa	49.4 ± 0.4Bc	15.9 ± 0.3Aa	31.1 ± 0.9Aa	34.9 ± 1.3Aa	2.0 ± 0.2Ba
	T2	19.2 ± 1.2Aa	0.58 ± 0.06Aa	0.91 ± 0.03ABa	11.4 ± 1.2ABa	52.4 ± 1.4ABb	13.8 ± 0.5Ba	31.1 ± 1.4Aa	34.0 ± 1.5Aa	2.2 ± 0.3Ba
	T3	17.3 ± 1.5ABa	0.52 ± 0.05ABa	0.85 ± 0.04Ba	10.8 ± 1.5Ba	52.6 ± 1.1ABb	13.5 ± 0.7Ba	32.9 ± 0.8Aa	35.5 ± 0.8Aa	3.5 ± 0.5Aa
	T4	16.4 ± 1.4Ba	0.47 ± 0.03Ba	0.83 ± 0.05Ba	10.0 ± 1.5Ba	53.4 ± 0.3Ac	13.2 ± 0.4Ba	31.9 ± 1.4Aa	34.5 ± 1.2Aa	3.5 ± 0.5Ac
07	Control	20.5 ± 0.9Ba	0.66 ± 0.06Aa	0.98 ± 0.03ABa	11.56 ± 0.9ABa	52.7 ± 0.9Bab	14.3 ± 0.2Aa	28.1 ± 0.6Ab	31.5 ± 0.7Ab	–
	T1	22.9 ± 1.2Aa	0.65 ± 0.02Aa	1.08 ± 0.05Aa	14.01 ± 1.3Aa	51.8 ± 0.8Bb	13.0 ± 0.4ABb	28.7 ± 0.7Ab	31.5 ± 0.6Ab	1.7 ± 0.2Dab
	T2	20.1 ± 1.3Ba	063 ± 0.04ABa	0.99 ± 0.04ABa	12.73 ± 1.6ABa	53.3 ± 1.4Ba	13.0 ± 0.6ABab	29.9 ± 0.4Aa	32.6 ± 0.8Aab	2.2 ± 0.3Ca
	T3	19.6 ± 0.8BCa	0.55 ± 0.04ABa	0.89 ± 0.03Ba	11.64 ± 0.8Ba	55.4 ± 0.5ABa	11.6 ± 0.8Ba	28.5 ± 0.8Ab	30.8 ± 0.8Ab	3.8 ± 0.3Ba
	T4	17.3 ± 0.7Ca	0.49 ± 0.05Ba	0.88 ± 0.04Ba	11.00 ± 1.1Ba	56.8 ± 0.5Ab	11.2 ± 0.9Bab	27.9 ± 0.3Ab	30.0 ± 1.1Ab	5.1 ± 0.5Ab
14	Control	20.1 ± 1.0ABa	0.63 ± 0.04Aa	0.97 ± 0.03ABa	11.06 ± 0.9Ba	53.5 ± 0.8Ca	12.4 ± 0.5Ab	27.6 ± 0.6Ab	30.3 ± 0.7Ab	–
	T1	22.2 ± 0.6Aa	0.64 ± 0.04Aa	1.01 ± 0.03Aa	14.26 ± 1.5Aa	54.2 ± 1.1BCa	12.8 ± 0.5Ab	27.5 ± 0.3Ab	30.3 ± 0.6Ab	0.8 ± 0.2Db
	T2	21.1 ± 0.8ABa	0.63 ± 0.04Aa	0.96 ± 0.04ABa	11.48 ± 0.7Ba	55.5 ± 0.6BCa	11.7 ± 0.5ABb	27.3 ± 1.7Aa	29.7 ± 1.8Ab	2.1 ± 0.2Ca
	T3	19.1 ± 0.6BCa	0.56 ± 0.03ABa	0.91 ± 0.04ABa	11.25 ± 1.3Ba	56.4 ± 0.7ABa	11.2 ± 0.5ABa	26.4 ± 0.6ABb	28.6 ± 0.7ABc	3.4 ± 0.4Ba
	T4	18.4 ± 0.7Ca	0.50 ± 0.04Ba	0.89 ± 0.04Ba	10.92 ± 1.2Ba	58.8 ± 0.4Aa	10.4 ± 0.4Bb	25.6 ± 0.8Bb	27.7 ± 0.9Bc	6.0 ± 0.2Aa

Control: Broiler chicken nugget prepared without milkfat (MF) and potato mash (PM); T1, T2, T3, and T4: Spent hen nuggets prepared using different levels of MF and PM by replacing spent meat. All values are mean ± standard error (n = 3); Different letters (A–E for different samples in the same week, a–e for same sample in different weeks) in a column indicate significant differences (p < 0.05); L* = Lightness; a* = Redness; b* = Yellowness; C* = Chroma value; ΔE = Total color differences

Texture

The favorable texture has a good relation with the mouthfeel and other sensory attributes of food products (Kang et al. 2018). The textural profiles of the control and SHNs were measured at 1st, 7th, and 14th days of storage and the results are shown in Table 3. The textural attributes amongest the nuggets were very close to each other. The hardness, cohesiveness, springiness, and chewiness increased slightly at 7 days and again decreased slightly at 14 days of storage, but the changes were not significantly different. At 1st day of storage, the highest hardness (20.2 N) was for T1 followed by T2 (19.2 N), control (18.9 N), T3 (17.3), and T4 (16.4 N). T1 had significantly higher chewiness (14.0 N) compared to the control, T3, and T4. The chewiness between T2 and control nuggets was not significantly different. The springiness was also higher for T1 compared to the T3 and T4. The higher hardness, springiness, and chewiness for T1 may be due to high content of SHM, which is low in tenderness and high in toughness than the broiler chicken meat. The incorporation of MF (> 8%) and PM (> 2%) by substituting SHM led to decreased hardness, cohesiveness, springiness, and chewiness in SHNs due to increasing level of fat. Andres et al. (2006) reported that hardness of meat products increased with storage at 4 °C due to loss of water. Cofrades et al. (2000) reported that protein-rich meat products have the ability to retain water/oil, and in doing so develop the juiciness and tenderness of meat products. The textural attributes of this study are in accordance with those reported by Bhosale et al. (2011) and Rahimi et al. (2018) for chicken nuggets prepared using different ingredients.

Sensory evaluation

Sensory properties are a major concern for the development of meat products using SHM. The sensory traits for the control and different SHNs are shown in Fig. 1. The color score was higher for the control (7.3) followed by T2, T1, T3, and T4. The control, T1, and T2 were not significantly different with respect to the color. The MF and PM incorporation showed a positive impact on the flavor in SHNs. Thus, T2, T3, and T4 had a higher score for flavor with values of 6.8, 6.6, 6.6 respectively as compared to the control (6.1) and T1 (6.2). The juiciness scores were not significantly different which may be due to similar contents of total fluids (water and oil) in each nugget. The incorporation of MF led to an increased taste score for SHN. Thus, the taste scores were higher for T2, T3, and T4 than that of the T1 and control. The T1 had lower chewiness score amongest the nuggets owing to a higher level of SHM which could result in lower tenderness and higher toughness. The overall acceptability scores for the control, T2, and T3 were not significantly different and had higher (p < 0.05) scores compared to other SHNs. According to the panelists’ judgement, about 65–70% SHM with 20% total fat including 8–10% MF was preferable in terms of color, flavor, juiciness, taste, chewiness, and overall acceptability. It was reported that meat products containing 20% fat showed more acceptable organoleptic quality characteristics and overall acceptability as compared to the high/low fat-containing meat products (Rahman et al. 2019b). Bhat et al. (2013) found good sensory attributes on meat ball prepared using SHM with the milk powder, vegetable fat and other ingredients and coated with skin.

Fig. 1.

Sensory attributes of the control and for the nuggets using spent hen meat (SHNs). Control: The nugget prepared using broiler chicken meat without milkfat (MF) and potato mash (PM); T1, T2, T3, and T4: SHNs using different levels of spent hen meat added with MF and PM

Oxidative stability

1. Conjugated dienes

Conjugated dienes are good indicators of an early stage of lipid oxidation, at this stage, CD formation occurs due to the rearrangement of double bonds of hydroperoxides produced from polyunsaturated fatty acids (Shahidi and Zhong 2010). The CD values (mmol kg⁻¹ sample) were in the range of 2.5 to 3.5 for the control, 2.6 to 3.5 for T1, 2.5 to 3.6 for T2, 2.6 to 3.6 for T3, and 2.7 to 3.6 for T4, during storage. Figure 2A showed that the CD values significantly increased during 7 days of storage and later (7–14 days) increased slightly. At the same storage period, the CD values amongest the nuggets (except T4) were not significantly different. The T4 had a significantly higher CD than those for other nuggets due to higher fat content. Similar results have been reported by Hwang et al. (2011) who demonstrated that CD values significantly increased for 7 days and then decreased until the end of 10 days storage. It was reported that the CD concentration in pork patties added with whey and soy proteins was significantly increased initially, followed by a decreased thereafter (Peña-Ramos and Xiong 2003). Roldan et al. (2014) reported that thermal process, cooking time, and protein and fat ratio are important factors for increasing CD.

• (b)Thiobarbituric acid-reactive substance (TBARS)

Fig. 2.

Oxidative stability of the control and spent hen nuggets; (A) conjugated dienes and (B) thiobarbituric acid-reactive substance (TBARS) values during storage; Control: the nugget using broiler chicken; T1, T2, T3, and T4: SHNs using different levels of spent hen meat added with MF and PM. Different letters (A–C for different samples at the same week, a–c for same samples at different week) in lines indicate significant differences (p < 0.05)

The TBARS values (mg MDA kg⁻¹ sample) for the control and SHNs increased with storage time (Fig. 2B). Initially, the range of TBARS was 0.25 (control) to 0.30 (T4). At the end of storage, the highest TBARS was for T4 (0.44) followed by T3 (0.36), T1 (0.33), T2 (0.32), and control (0.32). The T3 and T4 samples had significantly higher TBARS values than those for rest of the nugget samples owing to higher fat content. The control, T1, and T2 were not significantly different with respect to TBARS values. These results indicated that the incorporation of MF up to 8% by substituting SHM did not significantly affect the TBARS value in SHNs during storage. The TBARS results are in good agreement with those reported by Hwang et al. (2011) for the chicken nuggets stored at 4 °C for 10 days. It was reported that malondialdehyde (MDA) is more susceptible to react with other compounds that exist in meat which have primary amino acid groups in terms of proteins, phospholipids, DNA or amino acids (Ventanas et al. 2007). These lead to reducing the amount of MDA and other reactive lipid carbonyls present to react with TBA and by contrast decrease the TBARS values (Roldan et al. 2014). Therefore, the higher proteins in control, T1, and T2 might react with MDA and inhibit the increase in TBARS values.

However, the results of CD and TBARS for oxidative stability showed a good similarity between control and SHNs (T1 and T2). Amongest the nuggets, control, T1, and T2 showed a statistically insignificant difference for oxidative stability during storage.

Conclusion

The utilization of SHM is important for the egg-producing industries. MF may be an effective functional ingredient for increasing the quality characteristics particularly texture, flavor, taste and other sensory attributes of SHN. The findings of this study confirmed that SHN added with MF and PM had comparable quality characteristics with that of the chicken nugget prepared using broiler chicken meat. Consumer preferences towards high fat diets have changed and low-fat diets are preffered to avoid chronic diseases. However, the total fat content of SHN was not significantly higher after frying when compared to that of the broiler chicken nuggets; due to combined effects of water loss and oil absorption capacity. Moreover, the addition of MF and PM at a certain level did not show any adverse effects on SHN for increasing oxidative deterioration. Therefore, PM- and MF-added SHN prepared in this study may be a regular chicken nugget for all consumers.

Electronic supplementary material

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