Effect of feeding black soldier fly larvae meal on colour parameters, structural attributes and Sensory evaluation scores of breast meat in commercial broilers

Introduction

Insects and their meal prepared contain high nutritive value in terms of crude protein, fats, minerals and essential vitamins. It has been well documented that larvae and pupae of insects such as house fly, black soldier fly have crude protein comparable to that of soyabean meal used in poultry diets (40-60%) and hence can be used as a potential and sustainable alternative protein source in broilers, pigs and fish farming (Kareem et al., 2018) [15] . Schiavone et al. (2016) [26] observed that the meal prepared from the BSF larvae had higher metabolizable energy and opined that it can be used as a potential source for replacement of maize in diets of broiler chicken. An attempt was made to incorporate and evaluate the effect of inclusion of black Soldier fly larvae meal in broiler diet on carcass colour analysis, structural attributes and Sensory evaluation scores of breast meat in commercial broilers.

Materials and Methods

A total of one hundred and twenty (120) day old commercial broiler chicks were procured from Venkateshwara Hatcheries Pvt. Ltd. Bengaluru and all the chicks were weighed and wing banded individually. The study was carried out with permission from Institutional Animal Ethics Committee, Veterinary College, Hebbal, Bangalore. The chicks were allocated to four different treatment groups each consisting of three replicates with 10 chicks each (30 chicks per treatment). Each of the treatment groups were fed with different types of experimental diets. The control group T 1 was fed with soyabean meal based basal diet as per BIS (2007) standards. Black Soldier Fly Larvae meal was procured from Sri Kalleshwari feeds Pvt Ltd, Kerala. The composition of BSF larvae meal is presented in Table 1. Birds in treatment groups T 2 , T 3 , T 4 were fed diet with 5, 10 and 15 Percent of black soldier fly larvae meal respectively and all the diets will be formulated to meet isocaloric and nitrogenous by manipulating the diet inclusion level in the basal diet. (Table 2, 3 and4). The chicks were reared in deep litter system and will be maintained under standard managemental practices till 6 th weeks of age. Feed and water will be provided ad libitum throughout the experimental period. At the end of the 6 th week, six (6) birds from each treatment will be slaughtered as per standard protocol to studied Colour parameters, structural attributes and Sensory evaluation scores of breast meat

Colour Analysis

Colour of the sample was tested using Hunter lab Mini scan XE plus Spectrocolorimeter (HunterLab, Model No: MSEZ-4500L, Reston, Virginia, USA) with geometry of diffuse/80 (sphere-8 mm view) and an illuminant of D65/10 deg (Bindu et al., 2007) [1] . The instrument was calibrated with black and white tile (L* = 94, a* = 1.10 and b* = 0.6) every time before the colour measurement was taken. The colour was expressed as L* (brightness), a* (redness) and b* (yellowness). The hue (relative position of colour between redness and yellowness) and chroma (colour intensity) was calculated as follows.

Average value for each colour parameter was determined by taking observation from six different areas of the same sample.

Myoglobin and Met-Myoglobin content:

Myoglobin was extracted from meat sample using a procedure as detailed by Warris (2007) [31] with slight modifications (Trout, 1989) [28] .

Rigor value estimation (R-Value):

Rigor value was estimated as per the method outlined by (Honikel and Fischer, 1977) [12] . The R-value of the meat samples were estimated at 2 and 24 hours after slaughter.

Collagen content: Hydroxyproline content of the meat sample was estimated based on the procedure of Nueman and Logan (1950) [22] with few modifications as recommended by Naveena et al. (2004) [21] . The collagen content was calculated by multiplying hydroxyproline content with 7.14 (Dransfield et al., 1983) [9] and was expressed in mg/g tissue.

Collagen solubility: Collagen solubility was assessed using the method described by Mahendrakar et al. (1989) [18] . HP content was calculated using the below formula. % Collagen solubility = 7.14 X % HP solubilized Myofibrillar fragmentation index: Myofibrillar fragmentation index was estimated by following the method given by Davis et al. (1980) [7] with slight modifications as suggested by Hawkins et al. (1987) [10] .

Warner-Bratzler shear force: Warner-Bratzler shear force (WBSF) of each muscle sample was determined by the method outlined by Wheeler et al. (1997) [32] .

Muscle fibre diameter: Fibre diameter was measured as per the method outlined by Jeremiah and Martin (1977) [14] .

Sarcomere length: Sarcomere length of each muscle sample was measured as per the method outlined by Hostetler et al. (1972) [13] .

Sensory Evaluation: The meat samples were cooked at 100 ˚C in a water bath for 30 minutes. The cooked meat chunks were served to semi-trained panelists and evaluated for appearance, flavor, juiciness, tenderness and overall acceptability using an 8-point descriptive scale in a score sheet (Where, 8 = extremely desirable, 1 = extremely undesirable) (Keeton, 1983) [16] .

Statistical analysis:

The descriptive statistics for the different types of data were determined as per Snedecor and Cochran (1994) [28] and the SPSS 20 statistical software. The differences between the mean values were evaluated using Tukey's Range Test at a significance level of 0.05 (P ≤ 0.05).

Results

Meat colour

The Mean ± SE of lightness, redness, yellowness, hue, chroma, myoglobin and met-myoglobin values of breast meat from commercial broilers fed with Black soldier fly larvae meal are presented in the Table 5.

Lightness (L*):

The Mean ± SE of the lightness of breast meat in T 1 , T 2 , T 3 and T 4 were 54.73±0.72, 55.11±0.29, 55.23±0.40 and 55.97±0.19, respectively. No significant differences in lightness value were recorded between all the four treatments groups. In the present study, no significant difference could be observed in the lightness values between the different treatments and the value ranged from 54.73 to 55.97.

Redness (a*):

The Mean ± SE of the redness of breast meat in T 1 , T 2 , T 3 and T 4 were 2.70±0.11, 2.97±0.14, 2.98±0.07 and 3.20±0.11, respectively. Statistical analysis revealed a significant (p<0.05) difference in redness (a*) values between the treatment groups. It was observed that T 4 has the highest redness and was not significantly different from T 2 and T 3 , similarly no significant difference in redness value could be observed between T 1 , T 2 and T 3 . The redness values increased linearly with increase in inclusion levels of BSF larvae meal. The results of the redness (a*) values revealed that with the increase in level of inclusion of BSF larvae meal there was a linear increase in redness (a*) values, with higher values being observed in 15 Percent level of inclusion compared to other groups. This could be attributed to higher myoglobin concentration in 15 Percent inclusion level in this study. No significant difference could be observed between the three levels of inclusion of BSF larvae meal.

Yellowness (b*):

The Mean ± SE of the yellowness values of breast meat in T 1 , T 2 , T 3 and T 4 were 11.03±0.14, 10.38±0.24, 10.18±0.40 and 9.68±0.23, respectively. Analysis of variance revealed a significant (p<0.05) difference in yellowness (b*) values between the treatment groups. It was observed that T 4 has the lowest yellowness value and was not significantly different from T 2 and T 3 .

There was also no significant difference in yellowness value between T 1 , T 2 and T 3 . A linear decrease in yellowness value could be observed with the increasing levels of BSF larvae meal inclusion in this study. The Mean ± SE of the hue of breast meat of T 1 , T 2 , T 3 and T 4 were 0.51±0.003, 0.52±0.004, 0.50±0.005 and 0.51±0.005, respectively. No significant difference could be observed in hue values between the treatment groups. The Mean ± SE of the chroma of breast meat in T 1 , T 2 , T 3 and T 4 were 3.32±0.02, 3.22±0.03, 3.18±0.06 and 3.11±0.03, respectively. The ANOVA revealed significant (p<0.05) difference in chroma value among different treatment groups. T 4 had the highest chroma values and was significantly different for T 1 and no significant difference could be observed between T 4 , T 2 and T 3 and between T 1 , T 2 and T 3 .

The Mean ± SE of the myoglobin value of breast meat in T 1 , T 2 , T 3 and T 4 were 0.88±0.01, 0.94±0.03, 0.9 3±0.05 and 1.06±0.05, respectively. A significant (p<0.05) difference in myoglobin content was recorded between the treatment groups. T 4 had the highest myoglobin content and was significantly different from control, whereas no significant difference could be observed between T 2 , T 3 and T 4 . Similarly, no significant difference could be observed with respect to myoglobin content between T 1 , T 2 and T 3 . A linear increase in myoglobin content was observed with increase in level of inclusion of BSF larvae meal in the diet. The Mean ± SE of the met-myoglobin value of breast meat in T 1 , T 2 , T 3 and T 4 were 66.17±1.12, 68.28±2.65, 68.60±1.11 and 65.87±2.55, respectively. No significant differences in met-myoglobin value were recorded between all four treatments. The results of the study indicated that there was a significant difference in concentration of myoglobin between different treatment groups with higher concentration being recorded in 15 Percent inclusion level. No significant difference could be observed with respect to met-myoglobin concentration between the treatment groups in this study. A linear and non-significant increase was evident with increase in level of inclusion of BSF larvae meal.

Structural characteristics

The Mean ± SE of shear force, muscle fiber diameter, sarcomere length, collagen content, collagen solubility and myofibrillar fragmentation index values of breast meat from commercial broilers fed with Black soldier fly larvae meal are presented in the Table 6 Shear force (kg/cm 2 ): The Mean ± SE of the shear force value of breast meat in T 1 , T 2 , T 3 and T 4 were 5.50±0.11, 5.48±0.08, 5.43±0.11 and 5.32±0.07 respectively. No significant differences in shear force value were recorded between all four treatments. However, shear force value increased with increase in the inclusion levels of BSF larvae meal.

Muscle fiber diameter (µm):

The Mean ± SE of the muscle fiber diameter of breast meat in T 1 , T 2 , T 3 and T 4 were 54.69±0.77, 56.05±1.5, 55.52±0.34 and 54.73±1.4 respectively. No significant differences in muscle fiber diameter were recorded between all four treatments.

Sarcomere length (µm):

The Mean ± SE of the sarcomere length of breast meat in T 1 , T 2 , T 3 and T 4 were 1.36±0.03, 1.30±0.02, 1.31±0.02 and 1.32±0.02, respectively. No significant differences in sarcomere length were recorded between all four treatments.

The Mean ± SE of the collagen content of breast meat in T 1 , T 2 , T 3 and T 4 were 363.67±5.18, 367.21±2.47, 367.57±4.23 and 362.61±4.01, respectively. No significant differences in collagen content were recorded between all four treatment groups.

The Mean ± SE of the collagen solubility of breast meat in T 1 , T 2 , T 3 and T 4 were 17.97±0.39, 18.30±0.30, 18.38±0.25 and 18.52±0.43, respectively. The ANOVA revealed significant no significant difference in collagen solubility between the treatment groups,

Myofibrillar fragmentation index (MFI):

The Mean ± SE of the MFI value of breast meat in T 1 , T 2 , T 3 and T 4 were 59.18±0.79, 61.58±1.75, 60.67±3.96 and 61.01±1.13, respectively. No significant differences in MFI value were recorded between the treatment groups.

Sensory evaluation

The Mean ± SE of appearance, juiciness, tenderness, flavour and overall acceptability of breast meat from commercial broilers fed with Black soldier fly larvae meal are presented in the Table 7. The results of the present study revealed that there was no significant difference in appearance, juiciness, tenderness, flavor and overall acceptability of breast muscles between different treatments. The sensory scores this study corroborates with the results of shear force values and water holding capacity of meat in the present study. The Mean ± SE of the appearance value of breast meat in T 1 , T 2 , T 3 and T 4 were 7.23±0.22, 7.18±0.30, 7.50±0.34 and 7.33±0.33, respectively. No significant difference in appearance scores was recorded between the different treatment groups. The Mean ± SE of the juiciness value of breast meat in T 1 , T 2 , T 3 and T 4 were, 7.21±0.21, 7.00±0.26, 7.33±0.33 and 7.17±0.31, respectively. No significant difference in juiciness scores was recorded between the different treatment groups. The Mean ± SE of the tenderness value of breast meat in T 1 , T 2 , T 3 and T 4 were, 6.66±0.33, 6.67±0.21, 6.82±0.31 and 6.60±0.22, respectively. No significant difference in tenderness score was recorded between the different treatment groups. The Mean ± SE of the flavour value of breast meat in T 1 , T 2 , T 3 and T 4 were 7.16±0.31, 7.50±0.22, 7.00±0.37 and 7.05±0.31, respectively. No significant difference in flavour score was recorded between the different treatment groups. The Mean ± SE of the overall acceptability value of breast meat in T 1 , T 2 , T 3 and T 4 were 7.33±0.21, 7.16±0.40, 7.33±0.33 and 7.21±0.22, respectively. No significant difference in overall acceptability was recorded between the treatment groups.

Discussions

Meat colour remains the main visual parameter assessed by consumers and the most impacting criterion in the meat purchase decision. Indeed, it is an essential parameter in meat industry, in which carcasses should be pink or pale pink, preferred by the consumers, while darker meat is considerably difficult to market (Calnan et al., 2016) [3] .

The values Lightness (L*) are well within the normal range of lightness values as reported by Van Laack et al. (2000) [30] who stated that the normal values of lightness in broiler muscle ranged from 50 and 56. The findings of the Redness (a*) study are in line with Cullere et al. (2016) [5] who observed that inclusion of BSF larvae meal significantly affected the redness (a*) value in the breast meat of broiler quails and they reported that higher redness value in birds fed 10 Percent BSF meal (1.13). Similar increase in redness values have been reported by Schiavone et al. (2019) [27] , Daszkiewicz et al. (2022) [6] and Murawska et al. (2021) [20] in broilers fed different levels of BSF larvae meal. The increase in redness values could be attributed to the fact that BSF larvae contain higher concentrations of minerals, including Fe, than other edible insects used as animal feed. Hence, higher supply of Fe, which is present in the heme group of heme pigments, may be linked with the concentration of heme pigments in meat (Dierenfeld and King, 2008) [8] . In the present experiment, it was observed that there was a significant linear decrease in yellowness (b*) and chroma value with increase in levels of BSF larvae meal. The findings are in alignment with Murawska et al. (2021) [20] who observed a decrease in yellowness and saturation (chroma) values in breast muscle in broiler supplemented with HI larvae meal as compared to that of control. Popova et al. (2020) [24] also reported that both breast and thigh muscle of broiler fed with BSF larvae meal had a significantly lower yellowness (b*) and chroma value. However, contrary to the findings of this study Heuel et al. (2022) [11] observed a significant increase in yellowness in birds fed with BSFL meal as compared to control and Leiber et al. (2017) [17] who did not find any significant difference in meat colour of broilers fed BSF larvae meal. The findings of Myoglobin (mg/g) and Met-myoglobin (%) were in line with Daszkiewicz et al. (2022) [6] who also reported a linear and quadratic increase in total concentration of heme pigments in the muscles of broiler chickens with increasing HI meal levels, with a maximum concentration in diet with 75 Percent meal. In addition, the present findings cannot be compared with the results of other studies investigating BSF larvae meal because none of the researchers have studied the implication of BSF meal on muscle pigments. The results of the present Structural characteristics study revealed no significant difference in shear force value, sarcomere length, muscle fibre diameter, collagen content, solubility and Myofibrillar fragmentation index between the treatment groups indicating no negative influence of BSF larvae meal inclusion in broiler diets. It has been documented earlier that there is a strong positive relationship between sarcomere length and meat tenderness and muscles with the sarcomere length shorter than 2.0 µm are found to be tender (Wheeler et al., 2000) [33] . The values in the present study fall within this range and hence meat from all the treatments had similar shear force values. However, studies related to collagen content and solubility in broilers is very limited since the birds are slaughtered relatively in early stage of physiological development when intramuscular collagen is not significantly cross-linked (Purslow, 2018) [25] and there is paucity of data or information related to the effect of insect meal on structural characteristics in the meat of broiler chickens.

The findings of the present Sensory evaluation study are in agreement with Cross et al. (1986) [4] who concluded that BSF larvae meal did not cause any adverse effect on the eating quality attributes such as juiciness, tenderness and flavor as compared to that of control group. Similalry, Mohammed et al. (2017) [19] observed that the sensory panel scores did not reveal any significant differences in color, aroma, tenderness, flavor or overall acceptability in birds fed up to 33 Percent BSF meal. BSF larvae meal inclusion did not cause any significant influence on the aroma, flavour, initial and sustained juiciness and tenderness of cooked broiler breast muscles as that of soyabean fed broilers (Pieterse et al., 2018) [23] . However, contrary to the findings of this study, Murawska et al. (2021) [20] opined that the taste panelists could notice a slight but steady decrease in flavor of the meat as the inclusion level of BSF meal increased in the feed. They also reported that chickens fed the highest amount of BSF insect meal (100%) was tougher and had less desirable flavor compared to other groups.

Conclusion

The increase in redness values in commercial broiler breast meat could be attributed to the fact that BSF larvae contain higher concentrations of minerals, including Fe, leads to concentration of heme pigments in meat. BSF larvae meal feeding did not cause any adverse effect on the eating quality attributes such as juiciness, tenderness and flavor as compared to that of control group

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