Chitosan as a functional ingredient in Nile tilapia sausages: enhancing antioxidant capacity, technological performance, nutritional quality, and consumer acceptance

1 Introduction

Fish and fishery products are widely recognized as valuable components of healthy diets, providing high-quality protein, essential fatty acids, vitamins, and minerals (Phogat et al., 2022; FAO, 2022). Beyond direct consumption, their incorporation into processed foods has been explored as a strategy to improve the nutritional quality of food products (Chambó et al., 2018). Global per capita consumption of aquatic foods continues to rise and is projected to exceed 21.2 kg by 2030, reflecting their increasing importance in food and nutrition security (FAO, 2022). In Brazil, aquaculture has expanded rapidly, with production surpassing 968,000 tons in 2024, of which Nile tilapia (Oreochromis niloticus) accounted for nearly 70% (Peixe BR, 2025).

Nevertheless, fish remains highly perishable due to its biochemical composition—characterized by high moisture, unsaturated lipids, and endogenous enzymes—which makes it vulnerable to lipid oxidation and microbial spoilage (Nie et al., 2022). Conventional processing, such as filleting, generates substantial by-products — ranging approximately from 30% to 70% of the raw material — depending on the species and methods used, underscoring the urgency for strategies that reduce waste and enhance resource efficiency (Jimenez-Champi et al., 2024; Rathod et al., 2024). Moreover, the seafood industry also generates large quantities of crustacean shell waste, mainly from shrimp, crab, and lobster processing, which represents a major source of chitin and its deacetylated derivative chitosan (Hamed et al., 2016). Developing innovative products that incorporate these by-products promotes circularity in the value chain and enhances the accessibility of safe, nutritious food products (Jimenez-Champi et al., 2024).

Restructured fish-based products, including nuggets, burgers, and sausages, have emerged as viable alternatives to enhance the utilization of fish raw material. These products combine the nutritional advantages of fish with the convenience demanded by modern lifestyles (Maia et al., 2015; Guiné et al., 2020). Fish sausages, in particular, offer an effective means of extending shelf life and providing consumers with high-protein, low-fat options. They can be produced from surimi or mechanically separated meat, supplemented with spices and natural preservatives, thereby generating value-added products from aquaculture species such as tilapia (Al-Bulushi et al., 2013; Silva et al., 2020; You et al., 2022).

At the same time, consumers increasingly expect not only convenience and safety but also improved nutritional and functional attributes, often linked to natural bioactive compounds rather than synthetic additives (Kazemzadeh et al., 2022). This trend has driven research into ingredients capable of enhancing quality while meeting clean label demands. Among them, chitosan, a cationic polysaccharide derived from chitin, has received renewed attention for its multifunctionality, including its antimicrobial, antioxidant, biodegradable, and biocompatible properties (El-Araby et al., 2024; Muñoz-Tebar et al., 2023).

Chitosan exhibits strong antimicrobial effects by disrupting microbial cell membranes and chelating essential ions, as well as antioxidant activity through free radical scavenging and metal ion binding (Tayel et al., 2010; Hussain et al., 2021; Fernando et al., 2024). From a technological perspective, it contributes to emulsion stability, improves water-holding capacity, and acts as a natural binder and texturizer in meat matrices (Han et al., 2018; Yang et al., 2020). Such properties highlight its potential for developing healthier fish-based products with both functional and technological benefits.

Despite their potential, fish sausages often face technological challenges such as cooking losses, decreased water-holding capacity, and weakening of gel strength during storage (You et al., 2022). Additionally, as fish sausages are generally low in dietary fiber, their nutritional profile could be further improved by the incorporation of functional ingredients.

In this context, the inclusion of chitosan provides a dual benefit. From a nutritional perspective, chitosan acts as a source of dietary fiber, slows gastric digestion, and may promote the gradual release of beneficial fatty acids (Yao and Chiang, 2006). The non-specific activity of pepsin on chitosan generates chitooligosaccharides (Renuka et al., 2024), compounds associated with anticancer potential, protection of the digestive tract lining, and positive modulation of the gut microbiome (Guan and Feng, 2022). Its antioxidative capacity further contributes to reducing oxidative stress (Adiletta et al., 2021), while chitosan has also been reported to limit the transfer of heavy metals from food to consumer organs (Howard et al., 2023). From a technological perspective, chitosan improves emulsion stability, enhances water-holding capacity, and reduces cooking loss, thereby improving firmness, juiciness, and sensory acceptance (Chattopadhyay et al., 2019a, 2023). Previous studies have also reported similar benefits of chitosan in different meat and fish matrices, confirming its ability to improve technological and preservation attributes (Amaral et al., 2016; Alirezalu et al., 2019; Chattopadhyay et al., 2019a; Kazemzadeh et al., 2022).

These combined nutritional and techno-functional properties make chitosan more than a conventional stabilizer, positioning it as a multifunctional ingredient with direct relevance for the development of healthier and consumer-preferred fish sausages. Although these findings are promising, evidence regarding the integrated effects of chitosan on nutritional composition, antioxidant activity, technological attributes, and consumer acceptance in tilapia sausages remains limited. Most available studies have focused on isolated aspects, such as preservation or specific technological parameters (Mithushan et al., 2024; Bastomy and Rahmadhia, 2025), without a comprehensive evaluation of multiple quality dimensions. In this context, the present study provides an integrated assessment of the effects of chitosan on nutritional, antioxidant, technological, and sensory properties in Nile tilapia sausages, contributing to a more holistic understanding of its multifunctional role in fish-based emulsified products. Given the central role of tilapia in aquaculture and global markets, this approach reinforces the relevance of applying chitosan in tilapia-based products.

It is hypothesized that the inclusion of chitosan acts as a multifunctional ingredient capable of simultaneously improving antioxidant capacity, technological performance, nutritional profile, and consumer acceptance in Nile tilapia sausages. Accordingly, the objective of the present study was to evaluate the influence of chitosan inclusion at different levels in Nile tilapia sausages on proximate composition, antioxidant capacity, physicochemical and technological characteristics, and sensory acceptance. By integrating these aspects, this work provides new insights into the functional role of chitosan in fish-based products, supporting the development of healthier, more stable, and consumer-friendly aquaculture-derived foods.

2 Materials and methods

2.1 Preparation of sausages

Mechanically separated meat (MSM) from Nile tilapia (Oreochromis niloticus), commercially obtained from Mar & Terra (Bello Alimentos, Itaporã, Brazil), was used as the raw material for sausage preparation. The MSM was stored under frozen conditions (−18 °C) until use and thawed under refrigeration (± 4 °C) prior to processing.

Four different fish sausages were produced with the inclusion of varying chitosan levels (0, 0.25, 0.50, and 0.75%, w/w), with the 0% formulation considered as the control, according to the formulation presented in Table 1, resulting in a total of four treatments. Chitosan was pre-dissolved using the amount of acetic acid indicated in Table 1 (0.10, 0.20, and 0.30%, v/v for the 0.25, 0.50, and 0.75% chitosan treatments, respectively), together with part of the chilled water from the formulation, to ensure complete solubilization before incorporation. The resulting viscous chitosan solution was then added to the minced fish mixture during the emulsification step along with the remaining ingredients. This procedure followed the approach described by Chattopadhyay et al. (2019a), with adaptations.

Table 1. Formulation of Nile tilapia sausages with different levels of chitosan inclusion.

For sausage preparation, mechanically separated meat was first thawed and homogenized in a multiprocessor together with the other ingredients and crushed ice until complete mixing was achieved. The emulsions were stuffed manually into synthetic cellulose casings (hydrated cellulose) of 22 mm caliber. After stuffing, the sausages were manually twisted into portions of approximately 13 cm in length and tied with string. Cooking was performed in heated water under controlled conditions: initially at 55 °C for 30 min, followed by 65 °C for 15 min, 75 °C for 15 min, and finally 85 °C until the internal temperature of the sausages reached 75 °C. Once this temperature was attained, the sausages were removed and immersed in ice for 5 min.

The sausages were then stored in plastic bags, identified according to treatment, and kept under refrigeration (6 ± 1 °C) until further physicochemical and sensory analyses were carried out.

All sausage formulations were produced in a single batch under standardized conditions, resulting in approximately 80 sausages per treatment. These sausages were considered as independent experimental units. For each analysis, sausages were randomly selected from each treatment, and each replicate corresponds to a different sausage (n = 5 per treatment, depending on the analysis).

2.2 Proximate composition and caloric value

Proximate composition analyses were performed in triplicate for all four sausage formulations. Moisture content was determined by oven-drying at 105 °C until constant weight, according to AOAC method 950.46 (AOAC, 2005). Ash content was determined by incineration in a muffle furnace at 550 °C, following AOAC method 920.153 (AOAC, 2005).

Protein content was quantified using the Kjeldahl method (AOAC method 981.10, 2005), applying a nitrogen-to-protein conversion factor of 6.25. Total lipid content was determined according to the method of Bligh and Dyer (1959), using a chloroform–methanol–water system for extraction.

Carbohydrate content was calculated by difference, as described by Merrill and Watt (1973). Caloric value was estimated using Atwater factors (Atwater and Woods, 1896), considering 4 kcal/g for proteins and carbohydrates, 9 kcal/g for lipids, and 2 kcal/g for dietary fiber. Results were expressed as g/100 g and kcal/100 g.

2.3 Antioxidant capacity analysis

Extracts (1:1 w/v with methanol) were obtained according to Vital et al. (2016) using an Ultra-Turrax homogenizer (IKA^® - T10, USA), followed by centrifugation (4,000 rpm, 15 min) and filtration (filter paper: grammage – 80 g/m², thickness – 205 μm, pore size – 14 μm). Antioxidant activity was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, with extracts obtained from sausage samples.

The antioxidant capacity using the DPPH radical was assessed following Azeem et al. (2023), with modifications. Meat extracts (100 µL) were mixed with 1900 µL of a methanolic solution containing DPPH (60 μM) and incubated in the dark for 30 min. Absorbance was then measured at 515 nm against pure methanol, and the percentage inhibition was calculated according to Equation 1:

(1) I%=Abs control−Abs sampleAbs control×100

The antioxidant capacity using the ABTS radical was evaluated as described by Re et al. (1999). Methanolic extract (40 µL) was mixed with diluted ABTS reagent (7 mM ABTS and 2.45 mM potassium persulfate, 1.96 mL) and incubated in the dark for six minutes. The absorbance of the reaction mixture was measured at 734 nm in a spectrophotometer, and percentage of radical scavenging activity was calculated according to Equation 1.

2.4 pH and color analyses

pH was measured using a portable pH meter (Testo, model T 205, Testo Limited, Hampshire, UK) previously calibrated with standard buffer solutions at pH 4.0 and 7.0. Measurements were taken at room temperature (approximately 25 °C) on the homogenized internal portion of the sausages. For each treatment, five sausages were cut longitudinally, and the electrode was inserted directly into the geometric center of the sample to ensure representative readings.

Instrumental color analysis (n = 5) was performed on the internal portion of the sausages using a portable colorimeter (Konica Minolta Chroma Meter CR-410, Konica Minolta Optics Inc., Japan). The parameters L* (lightness), a* (redness), and b* (yellowness) were recorded.

2.5 Determination of cooking loss and water-holding capacity

Cooking loss (CL) in reheating was determined as described by You et al. (2022), with modifications. Sausage samples (n = 5 per treatment) were cut into 1 cm slices (~10 g), weighed on a precision balance, and placed in plastic bags. Samples were then cooked in a water bath at 90 °C for 20 min and cooled to room temperature. After removal from the bags and elimination of any free surface water, each sample was weighed again. CL was calculated according to Equation 2:

(2) CL(%)=(M1−M2)M1×100

where M1 is the mass of the sausage before cooking (g) and M2 is the mass after cooking (g).

Water-holding capacity (WHC) was determined according to You et al. (2022). Sausage samples (n = 5 per treatment; ~2 g) were precisely weighed, wrapped in filter paper (three layers), placed in centrifuge tubes, and centrifuged at 10,000 × g for 10 min. Samples were then removed from the tube and filter paper and weighed again. WHC was calculated according to Equation 3:

(3) WHC (%)= m2m1×100

where m1 is the sample weight before centrifugation (g) and m2 is the sample weight after centrifugation (g). WHC was expressed as percentage of weight retained after centrifugation, which inversely reflects expressible moisture.

2.6 Shear force determination

Prepared sausages were equilibrated at room temperature for one hour and then cut into cylinders of 25 mm diameter × 30 mm height. Shear force was measured using a TA.XT Plus texture analyzer (Stable Micro Systems, United Kingdom). The analysis was performed on ten sausages per treatment.

The test parameters were set as follows: pre-test speed 1.00 mm/s, test speed 2.00 mm/s, post-test speed 10.00 mm/s, distance 35.000 mm, time 5 s, trigger type high, trigger force 0.04903 N, and auto tare mode.

2.7 Sensory analysis

The sensory analysis was approved by the Ethics Committee for Research Involving Human Subjects of the Federal University of Grande Dourados (CEP/UFGD), under Approval No. 5.644.903.

Tests were carried out with 50 untrained panelists randomly selected, in individual booths under white light, using two tests (acceptance and purchase intention). The panel consisted of equal proportions of males and females (50% each). Most participants were aged between 21 and 30 years (68.75%), followed by individuals under 20 years (25.0%), with smaller representation from older age groups (31–40 years: 4.17%; 41–50 years: 2.08%). Participants reported varying frequencies of sausage consumption, including weekly (12.5%), monthly (41.7%), and occasional consumption (45.8%), indicating different levels of familiarity with the product.

Sausages were cooked until reaching an internal temperature of 80 °C. Each evaluator received approximately 30 g of samples from each treatment. The samples were identified with three random-digit codes and served in disposable cups, accompanied by a glass of mineral water and a plain cracker to cleanse the palate.

The attributes evaluated were color, odor, flavor, juiciness, and texture, using a nine-point structured hedonic scale ranging from “dislike extremely” (1) to “like extremely” (9) (Kemp et al., 2009). From these data, the Acceptability Index (AI) was calculated using Equation 4 (Dutcosky, 2013):

(4) AI%=mean product score9×100

Additionally, the samples were evaluated for purchase intention using a five-point hedonic scale ranging from 1 (“certainly would not buy”) to 5 (“certainly would buy”), as described by Lawless and Heymann (2010).

2.8 Statistical analysis

Data normality was assessed using the Shapiro–Wilk test, and homogeneity of variances was evaluated using Levene’s test. Subsequently, the data were subjected to analysis of variance (ANOVA), followed by Tukey’s post hoc test at a significance level of 5%. All statistical analyses were performed using Statistica 7.0 software (StatSoft, Tulsa, OK, USA). Results are presented as mean ± standard error.

For hedonic scale data from sensory analysis, the non-parametric Kruskal–Wallis test was applied to identify differences among treatments, using JAMOVI software. Results were expressed as medians per treatment. Significant differences were considered when p < 0.05.

Additionally, Pearson’s correlation analysis was performed to assess the relationships among physicochemical, technological, and sensory parameters.

3 Results

In the centesimal composition (Table 2), it was observed that moisture content was higher in sausages with chitosan inclusion (p < 0.001) compared with the 0% chitosan sausage. Protein content also differed among treatments (p < 0.05), with the highest mean value found in the sausage containing 0.75% chitosan. On the other hand, sausages with 0.25% and 0.75% chitosan showed lower lipid contents, which was also reflected in the caloric value, being lower in these treatments. Ash and carbohydrate contents were not affected by chitosan inclusion in the sausages (p > 0.05).

Table 2. Centesimal composition (g/100 g) and caloric value (kcal/100 g) of Nile tilapia sausages with different levels of chitosan inclusion.

*Means in the same row followed by different letters differ significantly according to Tukey’s test (p<0.05).

The ABTS and DPPH methods, used to assess whether chitosan influenced the antioxidant activity of the sausages, revealed similar results, showing a linear increase (p < 0.05) in inhibition percentages as the levels of chitosan inclusion increased (Figure 1).

For pH values (Table 3), a linear decrease (Figure 2A) was observed with increasing levels of chitosan (p < 0.001). Sausage color (Table 3) also showed significant regression effects (p < 0.001), where lightness (L) and yellowness (b) increased linearly with higher chitosan levels, while redness (a) decreased as inclusion levels increased (Figures 2B–D*).

Table 3. pH, lightness (L), redness (a), yellowness (b), cooking loss (CL), water-holding capacity (WHC), and shear force (SF) of Nile tilapia sausages with different levels of chitosan inclusion.

¹Linear regression, Figure 2. ²Means in the same row followed by different letters differ significantly according to Tukey’s test (P<0.05).

It was also observed that chitosan inclusion in sausages reduced cooking loss (CL), possibly due to the higher water-holding capacity (WHC) found in these treatments (p < 0.001, Table 3). The highest CL and lowest WHC were recorded in the sausage without chitosan (0%), while the lowest CL was obtained in sausages with 0.75%. The addition of chitosan to the formulations was also effective in increasing sausage shear force, with the highest mean value observed at 0.75% inclusion and the lowest at 0% (control treatment) (p < 0.001).

In the sensory profile (Figure 3), only color did not differ among treatments (p > 0.05). For the other attributes, sausages without chitosan showed lower median values compared with those containing chitosan (p < 0.05). For odor, higher medians were obtained in sausages with 0.50% and 0.75% chitosan. For flavor, sausages with 0.25% and 0.50% chitosan were better accepted, while for texture, the sausage with 0.25% chitosan received the highest acceptance. Regarding overall acceptability (Figure 3E) and purchase intention (Figure 3F), sausages with 0.25%, 0.50%, and 0.75% chitosan had higher medians compared with the control treatment (0%).

The acceptability index was higher than 70% in sausages with 0.25%, 0.50%, and 0.75% chitosan, and these values were significantly (p < 0.05) greater than those observed in sausages without chitosan (Figure 4).

Pearson’s correlation analysis (Table 4) showed that pH was negatively correlated with L* (−0.876), b* (−0.727), and shear force (−0.749), indicating that lower pH values were associated with higher lightness, yellowness, and firmness. Cooking loss (CL) was negatively correlated with WHC (−0.661) and shear force (−0.715), and positively correlated with moisture (0.794), lipid content (0.800), and caloric value (0.888). These results are consistent with the reduction in CL observed in sausages with chitosan inclusion and the improvement in WHC and structural properties.

Table 4. Pearson’s correlation coefficients among physicochemical and technological parameters of Nile tilapia sausages with different levels of chitosan inclusion.

Significant correlations at p < 0.05 are shown in bold.

4 Discussion

The consumption of fish-based products has been gradually increasing as consumers become more aware of the benefits associated with their intake (Thilsted et al., 2016), mainly due to their nutritional composition (Atitallah et al., 2019).

In the centesimal composition analysis of Nile tilapia sausages, formulations containing chitosan showed significantly higher moisture content compared to the control. This difference may be related to differences in water migration and retention during the multistage cooking process rather than a direct causal relationship with WHC or cooking loss values. Although the control formulation contained slightly more added water, greater water loss likely occurred during cooking, as moisture released from the matrix remained in the casing. Nevertheless, the concurrent increase in WHC and reduction in cooking loss observed in the chitosan treatments support the interpretation that chitosan improved the water-holding behavior of the system. The enhancement in water retention may be attributed to the ability of chitosan to form hydrogen bonds with water and protein molecules through its hydroxyl and amine groups (Amaral et al., 2016), thereby strengthening the water–protein matrix and reducing fluid exudation. It is important to note that the WHC values obtained in this study represent weight retention after centrifugation, which indirectly expresses the ability of the samples to retain water (i.e., lower expressible moisture), as commonly applied in meat and fish emulsions (Han et al., 2018; Chattopadhyay et al., 2019a). Although a linear decrease in pH was observed with increasing chitosan levels, this effect is primarily attributed to the acetic acid used for its solubilization. However, the concurrent increase in WHC and reduction in cooking loss suggest that the main mechanism underlying water retention was the interaction of chitosan with the protein–water matrix, rather than the mild acidification alone.

Polysaccharides such as chitosan contain several polar groups, including hydroxyl and carboxyl groups, that can form hydrogen bonds with water and protein molecules, thereby enhancing water-holding capacity in meat products (Yang et al., 2020). Water-holding capacity is an essential attribute for meat products and contributes to emulsion integrity during processing and to product shelf life (Han et al., 2018). The hydrophilic structure of chitosan facilitates its ability to retain water and proteins, which contributes to juiciness and texture in processed meat products.

The high water-holding capacity of chitosan in model systems of emulsified meat also promotes a reduction in cooking loss (Han et al., 2018). Cooking loss reflects the ability of the system to bind water and fat after protein denaturation and aggregation, with lower values generally representing higher-quality products (Chattopadhyay et al., 2019a). In the present study, however, the measured loss corresponds to reheating (recooking) loss rather than primary cooking loss, yet it can still be interpreted as an indicator of the product’s ability to retain water and fat during thermal treatment. The inclusion of chitosan significantly reduced cooking loss in the sausages, suggesting that chitosan improves moisture retention, possibly due to its ability to create a matrix that traps water. Chitosan is effective in reducing water and weight losses during thermal processing, similarly to other polymeric and protein additives such as carboxymethylcellulose, microcrystalline cellulose, carrageenan, gelatin, and collagen fibers (Souissi et al., 2016), resulting in a juicier product that is less prone to dehydration during cooking.

Chitosan also promoted protein retention in sausages while decreasing lipid content. The protein content may be associated with improved water retention and, to a minor extent, the nitrogen contribution from chitosan. Although the proportion of raw materials was constant among treatments, the lower lipid values observed in sausages with chitosan may be partially explained by a dilution effect caused by higher moisture retention. Additionally, chitosan can interact with lipids and proteins, forming a more stable emulsion that reduces free fat release during processing and analytical extraction (Han et al., 2018). This may indicate that this polysaccharide not only assists in water retention but also influences lipid emulsification and distribution. In addition to its affinity for proteins (Bakshi et al., 2020), chitosan, even at low concentrations, enhances the binding between water and fat, producing smaller and more homogeneous lipid droplets that maximize batter stability (Chattopadhyay et al., 2019b). The reduction in lipid content in sausages with chitosan also lowered their caloric value, an important aspect for calorie-restricted diets.

Chitosan has been widely reported as a multifunctional ingredient with antioxidant potential, mainly attributed to its ability to chelate pro-oxidant metal ions and to interfere with radical propagation reactions when incorporated into food systems (Fernando et al., 2024). In the present study, antioxidant activity was assessed using methanolic extracts of the sausage samples, which primarily reflects the radical scavenging capacity of methanol-soluble compounds present in the matrix rather than the direct activity of intact chitosan, due to its limited solubility in this solvent. The higher ABTS⁺ and DPPH⁺ inhibition percentages observed in sausages with increasing levels of chitosan therefore suggest an indirect antioxidant effect. This effect may be associated with structural modifications in the food matrix promoted by chitosan incorporation, including interactions with proteins and lipids (Han et al., 2018), reduced availability of pro-oxidant species (Fernando et al., 2024), and the possible formation of low-molecular-weight chitosan derivatives during processing (Carvalho et al., 2020). These changes may result in the generation or stabilization of compounds with greater radical scavenging capacity in the extracts. Similar interpretations have been reported in studies evaluating antioxidant capacity of meat products enriched with chitosan using solvent extracts, in which increased radical scavenging activity was attributed to system-level effects rather than to the direct extraction of chitosan or to direct measurements of lipid oxidation (Alirezalu et al., 2019; Carvalho et al., 2020).

The linear decrease in sausage pH observed with increasing chitosan levels is mainly associated with the amount of acetic acid added to enable chitosan solubilization (Giraldo and Rivas, 2021). In addition, chitosan may interact with the protein matrix, influencing the ionization of functional groups and, consequently, the overall acidity of the emulsion (Kurt, 2010). Slightly acidic conditions are known to favor protein gelation, particularly of myofibrillar proteins, which may contribute to improved emulsion stability and textural properties (Andrés-Bello et al., 2013). However, it should be noted that the experimental design does not allow the complete separation of the individual effects of acetic acid and chitosan on pH and emulsion behavior. Therefore, the observed improvements in stability and texture should be interpreted as the combined effect of chitosan incorporation under mildly acidic conditions, rather than as the exclusive effect of chitosan alone.

During sausage processing, chitosan was added as a solution in acetic acid after the addition of salt and other ingredients. Under these conditions, partial solubilization of myofibrillar proteins by salt likely favored electrostatic interactions with the positively charged chitosan molecules. This may have promoted localized aggregation and mild acid-induced gelation, contributing to the observed improvement in emulsion stability and texture (Han et al., 2018; Kurt, 2010).

In this study, pH showed a strong correlation with sausage shear force and color parameters. The addition of chitosan increased the shear force of sausages, and this greater firmness was better accepted by consumers in the texture attribute, especially in sausages with 0.25% chitosan. Possibly, chitosan tends to improve interactions with negatively charged proteins and increase the gelation capacity of the meat emulsion, leading to the formation of a strong gel structure with favorable textural properties (Alirezalu et al., 2019; Wang et al., 2023). According to Abdallah et al. (2023), the shear force results may also be explained by the higher water-holding capacity and lower water release in sausages processed with chitosan compared to the control group.

Regarding color, lightness (L) and yellowness (b*) increased with higher chitosan levels in sausages. This effect is associated with changes in their availability and reactivity within the food matrix, as well as with structural modifications promoted by chitosan incorporation. Under mildly acidic conditions, protonated amino groups of chitosan and protein–polysaccharide interactions may influence the distribution of water and fat in the sausage matrix, modifying light scattering and contributing to increased lightness, as previously reported for chitosan-based emulsions and coatings in meat systems (Shin et al., 2022).

Additionally, previous studies have suggested that chitosan incorporation may favor color changes through indirect effects on thermal reactions during cooking, including Maillard-type reactions involving available amino groups from proteins rather than an increase in their absolute number (Xavier et al., 2017). Furthermore, the increase in sausage lightness with chitosan inclusion may be related to a reduction in fat particle size, as demonstrated by Wang et al. (2023).

In addition to the positive effects on nutritional composition and technological characteristics, chitosan inclusion in sausages also improved sensory acceptance in odor, flavor, texture, and overall acceptability attributes, as well as increasing purchase intention. Tambaqui burgers with chitosan gel inclusion also showed better sensory acceptance in texture (Santos et al., 2024). Several studies have demonstrated that chitosan incorporation into meat products results in higher sensory scores compared to control samples, without unfavorable changes in their characteristic sensory traits (Casquete et al., 2017; Arslan and Soyer, 2018; Fernando et al., 2024).

One limitation of this study is that the experimental design does not allow the complete separation of the individual effects of chitosan and acetic acid, as chitosan was incorporated in solubilized form. The presence of acetic acid may have contributed to the observed reduction in pH and could indirectly influence protein interactions and water-holding capacity, potentially affecting emulsion stability. Therefore, the observed effects should be interpreted as the combined result of chitosan incorporation under mildly acidic conditions. Additionally, the results were obtained under fresh product conditions, and further studies evaluating the effects of chitosan during storage are necessary to better understand its role in product stability.

In summary, the incorporation of chitosan into Nile tilapia sausages improved nutritional composition by reducing lipid content and caloric value while increasing protein and moisture. Technologically, it enhanced water-holding capacity, reduced cooking loss, and contributed to greater firmness and desirable color changes. Moreover, chitosan demonstrated antioxidant activity and improved sensory acceptance, particularly in texture and overall acceptability, which were reflected in higher purchase intention. These findings highlight the potential of chitosan as a multifunctional ingredient for developing healthier, more stable, and consumer-preferred fish-based products.

5 Conclusions

The inclusion of up to 0.75% chitosan in Nile tilapia sausages not only improved stability, texture, and nutritional composition but also enhanced antioxidant capacity and sensory acceptance. These findings reinforce the functional value of chitosan as a multifunctional ingredient in fish-based products, a category still less explored compared to traditional meat matrices. Overall, the use of chitosan represents a promising strategy for the development of healthier, more stable, and consumer-preferred products with direct applicability in the food industry.

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Footnotes

Edited by: Stanley Iheanacho, University of Kiel, Germany

Reviewed by: Marcia M. English, St. Francis Xavier University, Canada

Shobana Sampath, Vel Tech Rangarajan Dr. Sagunthala R&D Institute of Science and Technology, India