The WB was procured from local market. Carrots were also procured from local market. They were washed with clean water and subjected to juice extraction. Pomace obtained was washed gently with clean water, squeezed in a muslin cloth to remove excess water and dried at a temperature of 58°C±2°C in a hot air drier to obtain dried pomace. Both the fibre sources were ground in an electrical grinder separately, packed in an airtight container and stored in the deep freezer (−18°C) for further experiment.

Broiler birds of the same age (6 to 7 weeks) reared under similar feeding and managemental conditions were slaughtered and dressed as per the standard procedure in the slaughter house of the department. Carcasses were washed thoroughly and breast and leg cuts were separated. Both the cuts were deboned manually after trimming of visible fat and connective tissue. Deboned meat from both the cuts was mixed in equal proportion and frozen for 24 h in a freezer (−18°C).

Deboned and frozen meat obtained from breast and leg cuts was minced in an electrical mincer (4 mm plate). For preparation of control sausage, sodium chloride (1.6 g), sodium tripolyphosphate (0.3 g), sodium nitrite (0.015 g), spice mix (1.9 g), condiments paste (3 g), refined wheat flour (2 g), water (8 g), and groundnut oil (4 g) were added to minced meat (79.2 g). Treatments consisted of the addition of WB and DCP each at three different levels viz. 3%, 6%, and 9% by replacing lean meat. Other ingredients were used in similar concentration as in control. Minced meat along with additives and dietary fibre sources was mixed in a bowl chopper for 4 to 6 min to prepare a stable emulsion. The emulsion was stuffed in artificial cellulose casings (C-25×70 ft., Euromate Food Tech Pvt. Ltd, Noida, India) by hand-operated sausage filling machine and cooked in boiling water in a closed container for 30 minutes. After cooking, sausages were delinked, cooled to room temperature, packaged in low-density polythene bags and stored at refrigerated temperature for further study.

Sensory evaluation was carried by a semi-trained panel consisting of faculty members and research fellows of the department. The panelists were experienced and well informed with different sensory attributes during their post graduate program. They were briefly explained about nature of experiment without revealing the identity of samples. Sausage samples of 2 cm diameter and 2 cm thickness were cut, warmed and served to the panel members. Coded samples were presented to test panelists individually and they were asked to evaluate the samples for sensory attributes viz colour and appearance, flavour, texture, tenderness, juiciness and overall acceptability (OAA) using 8-point descriptive scale (where 8 indicates extremely desirable and 1 indicates extremely undesirable). The tests were carried out two hours before or after the midday meal. Drinking water at room temperature was provided to rinse the mouth between sample testing.

Moisture, protein, fat, ash and crude fibre content of chicken sausage were determined as per the standard procedure of AOAC [14]. Moisture content was determined by using hot air oven and fat content by soxhlet method using petroleum ether (boiling range 60°C to 80°C) as a solvent. The Kjeldahl method of digestion, distillation and titration was followed for estimation of protein content. Ash content of samples was determined in a muffle furnace. Crude fibre content was estimated after acid-alkali digestion. Total dietary fibre (TDF), IDF, and soluble dietary fibre (SDF) were determined by the standard procedure of AOAC [15]. The cholesterol content was estimated by the spectrophotometric method by Zak [16] and expressed as mg/100 g of product.

The cooking yield of the final product was calculated by recording the weight of cooked product and initial raw weight. The pH of samples was determined as per the method of Trout et al [17] using digital pH meter (CyberScan pH 510, Thermo Fisher Scientific Inc., Waltham, MA, USA). The method of Baliga and Madaiah [18] was used to determine the stability of control and treated emulsions. Thiobarbituric acid reacting substances (TBARS) (mg malondehyde/kg) were determined by the following method of Witte et al [19].

The texture profile analysis was performed as per the procedure outlined by Bourne [20]. Samples of 20 mm diameter and 15 mm height were compressed to 50% of their original height. A time of 5 s was allowed to elapse between the two compression cycles. Force time deformation curves were obtained with a 50 kg load cell applied at a cross-head speed of 2 mm/s. Textural attributes such as hardness, springiness, cohesiveness, gumminess and chewiness were analysed.

For estimation of shear press value, samples (20 mm diameter, 15 mm height) were sheared through Warner Bratzler shear probe of texture analyser.

Colour of all the products was measured using a Konica Minolta chroma meter CR-400 (Konica Minolta Sensing, Inc., Osaka, Japan) with 8 mm aperture for measurement. The instrument was calibrated with a white standard plate. Colour scores were expressed as International Commission on Illumination Lab L* (lightness), a* (redness), and b* (yellowness).

Sausages were packaged in low density polyethylene bags and stored at a refrigeration temperature of 4°C±1°C. The samples were drawn at a regular interval of 5 days from day of preparation (0 day) to till spoilage of products. Initially, TBARS value and microbiological quality were analyzed to determine the shelf life of products, and then the sensory quality was determined up to the shelf life of nuggets at an interval of 5 days under refrigerated storage.

Standard plate count (SPC) (log cfu/g), psychrotrophic count (PC) (log cfu/g), and yeast and mould counts (log cfu/g) were determined by using the method recommended by APHA [21].

The data obtained from six replicates were subjected to analysis of variance. For fresh products, one way analysis of variance (treatment being independent variable) and for refrigerated stored products, two way analysis of variance (treatment and storage period being independent variables) was conducted. Duncan’s multiple range test at 5% significance level was applied to find out significant differences in mean [22].

Sensory scores of 3% fibre incorporated sausage were comparable with that of control (Table 1). No significant difference was noticed in colour scores of both WB and DCP added chicken sausage in comparison to control. A significant decline in flavour scores was noticed at 9% level in WB and 6% level in DCP incorporated sausages. A significant decline in texture, juiciness and tenderness scores was noticed at 6% level in both types of treatments. A significant decline in overall acceptability scores was noticed at 6% level in bran added sausages and at 9% level in DCP added sausages. Still, the overall acceptability scores for 6% and 9% fibre added sausage were around 7 and 6.5 representing very good and moderate to very good acceptability respectively. The addition of dietary fibre influences the sensory properties of meat products depending on the concentration. Dilution of meaty flavour at higher levels of fibre incorporation resulted in a decrease in flavour scores of fibre enriched sausages. The addition of carrot dietary fibre at a level above 3% resulted in a decrease in sensory acceptability of dry fermented sausage [23]. Mehta et al [24] also reported a decrease in sensory scores of chicken rolls and patties with increasing levels of rice bran and psyllium husk.

The addition of dietary fibre resulted in a significant decline in moisture content of chicken sausages (Table 2). Dietary fibres are recognized for their ability to bind water. The decline in moisture content of treated products in this study was due to the quantitative replacement of meat with dietary fibre sources containing very low moisture (5.09% to 9.47%) in comparison to meat. Characteristics of dietary fibre used may be another reason for decreased moisture content of treated products. As specified by Elleuch et al [25], the affinity of a dietary fibre to bind water depends upon its source, structure and physicochemical properties. Dietary fibre from algae has higher affinity to hold water and cereal derivatives present the lowest affinity. The low moisture content of treated products in the present study might be due to relatively less water binding ability of fibre sources used. Incorporation of dietary fibre in the dried form has been reported to decrease the moisture content of meat products. The addition of dried raw orange albedo at 2% level to bologna sausage resulted in a decrease in moisture content [26]. The decrease in moisture content has also been reported in low fat meat balls containing rye bran [13] and Turkish meat balls containing cereal brans (wheat, rye, oat, corn) [27]. The addition of DCP to chicken sausages resulted in a significant decrease in their protein content in comparison to control. Lower protein content in DCP treated sausage was due to less protein content in DCP in comparison to meat. The fat content of chicken sausages decreased after fibre incorporation. All WB treated sausage had significantly lower fat content in comparison to control whereas a significant decrease in fat content was noticed at 9% level in DCP treated sausages. Ash content increased after fibre addition and a significant increase in comparison to control was noticed at 6% level in WB treated sausages and 3% level in DCP treated sausages. This was due to more ash content in WB and DCP in comparison to meat. These results indicate that composition of fibre sources influence the proximate composition of meat products in which they are incorporated. Increased level of carrot dietary fibre resulted in a decrease in moisture and fat content of dry fermented sausage while no significant difference was noticed in protein and ash content [23]. Talukdar and Sharma [28] had reported that addition of WB resulted in a decrease in moisture and protein content and increase in ash content of chicken patties.

Meat does not contain dietary fibre. However, a small amount of crude fibre was noticed in control treatment which was due to fibre contributed by spices and condiments (Table 2). As expected, the crude fibre content of sausages increased significantly after incorporation of fibre sources to meat. This was due to the presence of crude fibre in WB (11.58%) and DCP (12.93%).

Cooking yield and emulsion stability increased in treated sausages and a significant difference was noticed at 6% level of fibre incorporation (Table 2). Retention of water by fibre present in treated sausages resulted in an increase in cooking yield and emulsion stability. The addition of carrot fibre improved water binding capacity of pork sausage [29]. Verma and Banerjee [30] have reported that fibre retains water and decreases cooking losses. Emulsion stability and cooking yield increased on the incorporation of rice bran in meat batters [31] and wheat and oat bran in chicken patties [28].

pH of chicken sausages increased significantly after WB addition whereas DCP incorporation resulted in a significant decrease in pH values (Table 2). pH of the fibre source influences the pH of meat product. Higher pH of WB added sausages was due to higher pH of WB (6.47) whereas, lower pH of DCP added sausages was due to acidic pH of DCP (4.94). Goat meat patties having kinnow rind powder extract had lower pH (6.02) as compared to control which was due to acidic pH of extracts [32]. The addition of dried orange fibre at 10, 15, and 20 g/kg level in dry cured fermented sausage resulted in a progressive decrease in pH [33]. Similarly, Verma et al [34] observed decrease in pH of sheep meat nuggets incorporated with guava powder.

TDF, SDF, and IDF content of treatments WB-2 (6% WB incorporated chicken sausage) and DCP-2 (6% DCP incorporated chicken sausage) i.e treatments with very good acceptability was estimated and compared with control. Both the treatments had significantly higher TDF and IDF content in comparison to control (Table 3). Treatment DCP-2 had significantly highest dietary fibre content among all the treatments. These results signify that drying of vegetable pomace results in a concentration of fibre in the pomace. The Higher amount of fibre in the pomace also results in higher amount of fibre in the product in which they are incorporated. Treatment DCP-2 had significantly higher SDF content in comparison to control and WB-2 treatments. Fibre derived from fruits and vegetables have a considerably higher proportion of SDF, whereas cereal fibres contain more insoluble cellulose and hemicelluloses [35]. No significant difference was noticed in SDF content of control and WB-2 treatment. This was due to proportionately very less amount of SDF in WB. Ranhotra et al [36] had reported that WB contains a high amount of IDF. Cholesterol content of fibre incorporated sausages were significantly lower than the control sausage. This was due to the lower meat content in fibre incorporated sausage than control.

TPA measurements may define the quality of the finished product and can contribute to the selection of the best functional ingredients [37]. Texture profile analysis of control and treated sausage depicted an increase in hardness of both type of sausage in comparison to control (Table 4). The increase in hardness of treated sausage is consistent with sensory evaluation results in which sensory panelists observed a decrease in texture, tenderness and juiciness scores. Springiness decreased in fibre added sausage and a significant decrease in comparison to control was noticed in DCP treated sausages. A significant decrease in cohesiveness with respect to control was also observed in both types of treated sausage. Significant increase in gumminess and chewiness was observed at 6% level in WB treated sausage and 9% level in DCP treated sausage which was due to increase in their hardness. Gumminess and chewiness are secondary parameters of texture profile analysis since gumminess depends on hardness and cohesiveness scores and chewiness depend on gumminess and springiness scores. Force needed to shear sausage samples transversely was expressed as shear force. The significantly higher shear force was observed at 9% bran level in comparison to control, whereas no significant difference was noticed in shear force value of control and DCP treated sausage. Varied results have been obtained on textural properties of meat products depending on amount and type of fibre. Results of the present study agree with those of Eim et al [23], who reported an increase in hardness of dry fermented sausage with an increase in the percentage of carrot dietary fibre. Saricoban et al [38] also reported that addition of WB to cooked beef patties increased their hardness and gumminess and decreased springiness and cohesiveness without influencing the adhesiveness. Similarly, Huang et al [39] noticed an increase in hardness value in rice bran added pork meatballs. However, Garcia et al [40] had reported that addition of peach, apple and orange fibres resulted in decreased hardness and increased springiness of low fat dry fermented sausages. Insoluble fibre can increase the consistency of meat products by forming an insoluble three dimensional network [41] which can influence the rheological properties of the continuous phase of emulsions. Grossi et al [42] reported that incorporation of carrot dietary fibre in a comminuted meat emulsion, result in a high order of network organization leading to a harder texture and high water binding capacity. Mansour and Khalil [6] had also reported that incorporation of WB to beef burger resulted in a significant increase in shear press value.

No significant difference was noticed in lightness and redness scores of WB and DCP treated sausages (Table 4). Yellowness increased significantly in WB treated sausages. Fibres may influence the colour of meat products due to their diversified colours and presence of pigments. Yasarlar et al [27] reported an increase in yellowness after incorporation of corn, oat and rye brans which was attributed to the presence of carotenoid pigments.