Chitosan Gel Prepared with Citric Acid as the Food Acidulant: Effect of the Chitosan Concentration and Gel pH on Physicochemical and Functional Properties of Fish Protein Emulsion Sausages

Abstract

Citric acid is a popular food acidulant with versatile utility as a preservative and acidity regulator in the meat industry, owing to its unique three pK_a values, which can be combined with the natural biopolymer chitosan to improve food quality. The scientific incorporation of a minimal range of chitosan and pH through organic acid additions for chitosan solubilization in the fish sausages can effectively improve their quality through their synergistic effect. Optimum conditions for emulsion stability, gel strength, and water holding capacity were found to be at a low concentration of chitosan, that is, 0.15 g at pH of 5.0, with their corresponding values of 42.55 ± 0.43 N mm, 94.91 ± 0.24, and 90.67 ± 0.50%. Lower pH ranges increased hardness and springiness values, and higher pH levels increased cohesiveness values at varying ranges of chitosan. Sensory analysis revealed tangy and sour flavors in the samples with lower pH.

1. Introduction

Meat-derived emulsion-based products as meal items fetch a significant demand in the contemporary food industry.^1,2 Among them, emulsified sausages are trending favorably among the versatile consumer domain around the world which are produced from diversified meat sources, predominantly the terrestrial ones such as veal, pork, beef, and rabbit.¹ However, in terms of severity related to the perilous health effects sourcing from red meat from terrestrial sources, aquatic animal meats like fish have emerged as an attractive source for making sausages concerning its cheaper availability and nutritional richness which can be made both as mince as well as surimi.³ Fish generally have less myoglobin and collagen content in their protein composition, which gives them a softer texture and a less reddish look when compared to terrestrial meat sources.⁴ In this regard, polysaccharides can be added both as fillers and as color enhancers, owing to their versatile functionality when added in the proper ratio.

In meat foods such as sausages, interactions thriving between polysaccharides and proteins hold a crucial functional role in their macroscopic characteristics. These interactive roles can be further altered by changes amalgamated in the processing conditions like pH, temperature exposure schedules, and level of homogenization, resulting in particle disintegration. These functional interactions produce products with desirable physicochemical and texture properties.^5,6 The change in processing pH through cooking procedures involves acid treatments in the form of marination, which has long been recognized as a traditional culinary technique to enhance the flavor, color, and tenderness of meat.⁷ The utility of such food acids, particularly the organic acids and their salts like citric, tartaric, and lactic acid, is highly effective in terms of their cost effectiveness, simplicity, and faster addition process.⁸ They are generally recognized as safe by the Food and Drug Administration (FDA) and hence are safe for incorporation as food acidulants in commercial meat food sectors where they are commonly employed for tenderizing any whole or meat cuts as preservatives, color stabilizers, and acidity regulators.^9,10 The maximum applicable amounts of the majority of organic acids along with their salts in food range between 0.1 and 0.4%.¹¹ Generally, organic food acids are weak acids that do not completely dissociate in water, unlike stronger acids. As a result, the pH-lowering ability of any weak organic acid is highly dependent on its concentration and chemical properties, specifically the acid constant (pK_a) and dissociation constant (K_a) numbers.^11,12 Citric acid (2-hydroxy 1,2,3-propane tricarboxylic acid) is one of the very few endogenous organic food acids, chiefly derived from citrus fruits, which is utilized explicitly in food to inhibit bacterial invasion, preserve food color, and improve the flavor features.^13,14 Being a weak organic acid uniquely having three pK_a values (3.06, 4.74, and 5.40) and other accessible carboxylic groups, citric acid can function as an active buffer when bound to the meat surface, making its application more diverse.¹⁵

Additives from aquatic wastes which are biological in nature like chitosan interacts with aquatic protein sources when added as a functional additive in solubilized forms. Being water insoluble in nature, chitosan solubilization and its amino charge activation are usually aided at a lowered pH of about 6.5, done primarily by incorporating food acidulants as a pH lowering agent for solubilizing. This can protonate the free amino groups present in chitosan at lower pH, triggering electrostatic repulsion between the polymer’s chains owing to effective chitosan solvation.¹⁶ Chitosan, as a soluble additive serving as preservative coatings, has been efficiently utilized in raw fish fillets as well as enrobed fish meat products in several investigational studies where natural acids were largely used as acidulants.¹⁷⁻²⁰ Conversely, a synergistic influence of different pH and chitosan concentration at minimal levels has not yet been seen to achieve better product quality and higher durability. In this context, the present study was conducted to test the influence of the combination of chitosan gel concentration prepared using citric acid at different pH conditions on the physicochemical and functional property enhancements of fish protein emulsion sausages. A minimal concentration of chitosan was chosen pertaining to the economic viability when added as an ingredient in meat products to impart maximum functionality.

2. Materials and Methods

2.1. Raw Materials

Pangasianodon hypophthalmus fish were procured from a nearby fish retail store having a length of 85–100 cm with a weight of 1–1.5 kg and brought to the processing laboratory in a chilled state with ice (1:1). The characteristics (viscosity: 100 cP, molecular weight: 75 kDa, and deacetylation degree: 92%) of the chitosan (M/s. India Sea Foods, Cochin, India) used in the study were similar to that used in the study conducted by Chattopadhyay et al.²¹ All the food ingredients (sunflower oil salt, sugar, corn flour, etc.) were bought from a local supermarket, and the chemicals (analytical grade) were ordered from Merck, Germany. Caustic soda (food grade NaOH) was bought for pH adjustment purposes during the preparation of chitosan gel.

2.2. Experimental Design

The effect of two independent variables, that is pH (A) and chitosan (B), on gel strength (GS) (Y₁), emulsion stability (ES) (Y₂), and water holding capacity (WHC) (Y₃) were optimized by RSM. In this experiment, central composite design (CCD) was performed, the levels and coded values of which are described in Table 1. Preliminary experiments were carried out rigorously for selecting the factors and their levels. The entire design was executed randomly and comprehended of 11 combinations, with triplicates at a central point, as shown in Table 2. The following equation was used to fit a second-order polynomial model to experimental data using a multiple regression model.

Here, Y = the predicted response, β₀ = intercept, n = number of factors analyzed, β_i, β_ii, and β_ij= the linear, quadratic, and interactive model coefficients, respectively. Consequently, X_i and X_j= levels of the independent parameters. Design Expert software (version 8.0.7.1, Stat-Ease, Inc.) was used for modeling and detailed statistical investigation. Evaluation of the lack of fit, R² (coefficient of determination), the significance of the regression coefficients, and the F-test value acquired from analysis of variance (ANOVA) was carried out to validate the model apprehended.

Table 1. Independent Variables with Their Respective Levels for the CCD Experimental Design.

		levels
codes	variables (independent)	–1 (low)	0 (mid)	+1 (high)
A	pH of chitosan gel	4.00	4.50	5.00
B	chitosan concentration	0.15	0.22	0.30

Table 2. CCD for the Response Parameters (GS: Gel Strength, ES: Emulsion Stability, and WHC: Water Holding Capacity)^a.

	variables (independent)		variables (dependent)
	gel pH	chitosan concentrations (g)	GS (N mm)	ES (%)	WHC (%)
trials (treatments)	A	B	Y1	Y2	Y3
T1	3.80	0.225	29.31 ± 0.29	89.28 ± 0.08	85.17 ± 0.79
T2	5.20	0.225	43.83 ± 1.35	96.26 ± 0.07	91.68 ± 0.27
T3	4.50	0.120	44.99 ± 0.32	93.16 ± 4.28	92.37 ± 0.20
T4	4.50	0.330	29.11 ± 1.08	96.14 ± 0.02	84.49 ± 4.13
T5	4.00	0.150	41.53 ± 0.84	95.29 ± 0.13	92.38 ± 0.02
T6	5.00	0.150	42.55 ± 1.33	96.46 ± 0.96	90.65 ± 1.78
T7	4.00	0.300	18.89 ± 0.45	90.00 ± 0.88	85.04 ± 1.89
T8	5.00	0.300	35.39 ± 1.38	96.44 ± 1.03	89.03 ± 1.41
T9	4.50	0.225	27.29 ± 1.26	99.44 ± 0.33	83.61 ± 1.20
T10	4.50	0.225	28.49 ± 2.05	98.45 ± 0.25	84.06 ± 3.56
T11	4.50	0.225	28.49 ± 1.59	98.15 ± 0.22	83.06 ± 2.66

^aA—pH; B—chitosan concentration; Y₁—GS (N mm); Y₂—ES (%); and Y₃—WHC (%). Values conveyed as the mean ± standard deviation (taking n = 3).

2.3. Experimental Procedure

2.3.1. Chitosan Gel Preparation Using Citric Acid at Diverse pH Values

11 combinations of chitosan gel at various concentrations (w/w) and pH conditions were prepared ensuing Chattopadhyay et al.²² with minor alterations. Chitosan powder was dissolved in a calculated quantity of water containing citric acid (2 g/g of chitosan powder) to the definite pH levels. The ultimate pH was adjusted to the requisite pH points using a sodium hydroxide (food-grade NaOH) solution. The resultant viscous gels were maintained under cold condition until used.

2.3.2. Catfish Mince Emulsion Sausage Preparation

As per the procedure charted by Chattopadhyay et al.²² with slight modifications, Pangasius emulsion sausage was prepared. After proper dressing (degutting and evisceration) of the whole fish, a deboning machine (Baader 694, Germany) was used for extracting the fresh mince from the dressed catfish. Throughout the process, a chilled temperature of lower than 10 °C was maintained. Fresh mince was augmented with iced water supplemented with sodium tri-polyphosphate (0.25% w/w), sugar (1% w/w), and NaCl (2.0% w/w), and kept separately for a few minutes. Cold mince was then mixed for 2–3 min using a bowl chopper of stainless-steel material (Stephan UMC 5 Electronic Cutter, Germany), after which the required amount of sunflower oil (5% of mince weight) was added subsequently for proper emulsification. Ice was sprinkled simultaneously during this step to maintain a cold temperature throughout. 11 combinations of citric acid–chitosan gels (≈10% v/w) were added to each treatment, followed by uniform batter mixing for 2–3 min and subsequent addition and mixing of corn starch for another 2–3 min. The final emulsion fish meat batters with all added ingredients were stuffed into synthetic casings by a sausage stuffer of stainless-steel material (Kitchener 5-Lb, China) having a diameter of 4 cm and a length of 17.5 cm, tied at the ends, and subjected to heat treatments for cooking (40 °C for 30 min followed by 90 °C for 20 min) in a thermally controlled water bath (Strike 300, Steroglass, Perugia, Italy). Final gelled sausages were cooled in chilled ice water before loading into the refrigerator (3–4 °C) for further study.

2.4. Process Parameters

2.4.1. pH (Cooked Sausages)

Sausage samples of 10 g weight were macerated finely in a homogenizer with 50 mL of distilled water maintaining a mixing ratio of 1:5 (w/v) for about 1 min at 10,000 rpm. A pre-probe-based digital pH meter (Eutech, UK) was used for noting down the respective pH values of each homogenate.

2.4.2. Cooking Loss

The meat batters of sausages were analyzed for cooking loss in each treatment group by the procedure described by Chattopadhyay et al.²¹ Final calculations were carried out using the following formula

where X₁ = initial weight of the emulsion sausage prior to cooking and X₂ = final weight of the cooked emulsion sausage.

2.4.3. Purge Loss

The sausages were peeled out from casings, put in small conduit tubes for a minute, and then bloated with the filter paper to absorb any liquid that leaked out of the sausage surface. To calculate the final purge loss as a weight loss percentage, the difference between the initial and final sausage weight after bloating is observed.²³

2.5. Response Parameters

2.5.1. Emulsion Stability

The ES parameter was determined as a percentage weight loss difference by centrifugal separation of oil from the freshly prepared fish emulsion batter samples similar to the methodology described by Chattopadhyay et al.²¹ and Verbeken et al.²⁴

2.5.2. Water Holding Capacity

The WHC for each combination group of the sausage samples was estimated as a percentage of centrifugal weight loss of sausage samples similar to the methodology described by Chattopadhyay et al.²¹

2.5.3. Gel Strength

Sausages stored at 4 °C were brought to room temperature before being cut up into small strands (cylinders of height = 2.5 cm). The highest breaking force (in g) and deformation (in cm) were analyzed through the TA.XTplus device (Stable Micro Systems, UK), using a spherical probe (5 mm diameter, 60 mm/min) having a 2 kg load cell. Every sample result was confirmed in triplicates.

2.6. Texture Profile Analysis

After equilibrating to room temperature, sausages of each treatment were cut into short strands (height and diameter = 2.5 cm) with triplicates. Textural attributes like hardness 1, cohesiveness, elasticity, and adhesiveness were analyzed using a TA.XTplus device (Stable Micro Systems, UK) where individual strands of sausages were subjected to a primary striking force of 0.5 N, compressions (40%), deformation rates (1 mm/s for both up speed and down speed), along with a wait point of 5 m and a 5 s delay gap. A cylindrical probe (diameter = 50 mm) with a sensor of 50 kg was used as the load cell. Finally displayed force–time curves, time variances, and peak areas generated from each compression series were used to compute all the textural parameters.

2.7. Sensory Evaluation

A group of 15 trained panellists representing various age groups (20–45 years old) were selected for conducting the sensory tests of each of the 11 sausage combinations. The panel constituted of research scholars: three from food specialization and three non-specialized students, three food scientists of the institute, and six laymen including children above 12 years of age. The panellists were served in a proper light and ventilated kitchen area in cleaned fiber plates displayed with sausage pieces (1 cm thick) of every combination. Each individual was given a sheet (hedonic scale sensory score sheet having a scale from 1 to 9) having spaces for scores conferring to the sausage taste, texture, flavor, color, odor, appearance, and overall acceptability.²⁵

3. Results and Discussion

3.1. Validation of the Model and Optimization of the Independent Variables in Emulsion Sausage Preparation

In order to get the highest values for GS, WHC, and ES, the pH and chitosan concentration were considered to be the two most important process variables. RSM and CCD were applied to optimize the emulsion sausage conditions. In Table 2, depending on two independent variables: pH (A) and chitosan concentration (B), the responses of GS (as Y₁), ES (as Y₂), and WHC (as Y₃) are shown. ANOVA, regression coefficients, R² values, and lack of fit are presented in Table 3. Figure 1A–F shows all the contour plots and 3D response surface plots depicting cumulative impact on the GS, ES, and WHC at the respective pH and chitosan concentrations.

Table 3. Results of ANOVA and Regression Coefficients for the Three Response Variables (GS, ES, and WHC)^a.

source	GS	ES	WHC
β0	28.09***	98.68*	83.58**
A	4.76***	2.19*	1.43*
B	–6.53***	–0.14NS**	–2.51**
AB	3.87*	1.32NS**	1.43NS*
A2	3.68**	–2.74*	2.64**
B2	3.92**	–1.80NS*	2.64**
P value	0.0006***	0.0295*	0.0044**
F value	37.88	6.59	15.81
R2	0.9743	0.8682	0.9405
adjusted R2	0.9486	0.7364	0.8810
lack of fit	0.0760NS*	0.0944NS*	0.0864NS*

^a* = significant at p < 0.05. ** = significant at p < 0.01. *** = significant at p < 0.001. ^NS* = non-significant at p > 0.05. ^NS** = non-significant at p > 0.1.

Figure 1.

Respective response surface plots and contour plots designed for the combined effect of pH and chitosan levels on GS (A,D), ES (B,E), and WHC (C,F).

The investigational data were compiled into a polynomial quadratic equation to analyze the maximum GS, ES, and WHC, which are listed serially below, respectively

The validity of the design is indicated by the coefficient determination (R²), which explains the overall variations of the model.²⁶ Hence, as can be perceived in Table 3, the R² obtained for all three response variables was 0.9743, 0.8682, and 0.9405, respectively, demonstrating that the model can explain 97.43, 86.82, and 94.05% variation in the data. These numbers suggest that the chosen model is an appropriate choice for illustrating the interconnections between the variables. The ANOVA for all three response parameters displayed lower p-values (p < 0.05) and higher F values of 37.88, 6.59, and 15.81, respectively, indicating the significance of the present model. Furthermore, the lack of fit for GS, ES, and WHC models was non-significant (p > 0.05), indicating a good fit of the models.²⁷

Table 4 shows the optimal conditions predicted, that is, pH of 5.00 and chitosan concentration of 0.15. The corresponding prophesied GS, ES, and WHC were 43.1173 N mm, 95.1388, and 91.3699%, respectively, with a moderately high desirability value of 0.781. Predicted values were further verified experimentally. GS, WHC, and ES, at these exact conditions, were found to be 42.55 ± 0.4250 N mm, 90.67 ± 0.5040, and 94.91 ± 0.2371%, respectively. Thus, the adequacy and accuracy of the model are precisely verified, yielding excellent agreement with the results predicted by the model, that is, within a 95% confidence interval.

Table 4. Experimental and Predicted Values of the Response Parameters (GS, ES, WHC) under the Optimum Conditions^a.

	optimum conditions		values
response parameters	pH	chitosan (g)	predicted	experimental*
ES	5.00	0.15	95.14	94.91 ± 0.24
GS			43.12	42.55 ± 0.43
WHC			91.37	90.67 ± 0.50

^aValues conveyed as the mean ± standard deviation (taking n = 3).

3.2. Effects on the Response Parameters of Sausages

3.2.1. Influence of pH and Chitosan on the GS

Protein functionality, particularly protein gelation, is greatly influenced by the initial batter pH, which finally affects the unfolding and aggregation of proteins during heating.²⁸ Studies suggest that slightly acidic conditions largely favor protein gelations, particularly of the myofibrillar ones.²⁹ Study outcomes in this experiment reveal that at a particular chitosan concentration (0.225 gm), a variation in GS on varying pH values was found. In general, increasing pH from 3.8 to 5.0 caused an increase in GS values, with T1 at the lowest pH showing the lowest GS compared to T2 at the highest pH range when the same quantity of chitosan was dissolved, that is, 0.225 gm. However, the GS values depended on the amount of chitosan dissolved at a particular pH. Moreover, an excessive quantity of chitosan can disorder the patterns of polymerization and aggregation in fish myofibrillar protein, thus weakening their concentrations during the heat exposures, making the GS of meat gels to reduce.³⁰ In chitosan-based studies on food, it is supposed that chitosan at upper low pH gradients (pH exceeding 5.0) forms strong gels because of the existence of the reactive −NH₃ moiety at the C₂ position of chitosan molecule.³¹ A lucid concept in such inferences reveals that pH values greater than chitosan’s pK_a values (around 6.5) cause deprotonation of the amino groups (−NH₃) in chitosan, resulting in an augmented self-aggregation of protein molecules and their enhanced gelation.^32,33

3.2.2. Influence of pH and Chitosan on the Fish ES

Chitosan, even at lower concentrations, can bind efficiently to the present moisture and fat in food, making a layer of homogenized lipid droplets and giving better stability to the emulsion batter mix.^34,35 Higher extreme pH and chitosan values produce a maximum ES value (Figure 1B,E). Low pH can adversely affect the batter emulsion properties; T1 with the lowest pH had lower ES than T2, T9, T10, and T11 at comparatively higher pH ranges. A similar trend was observed in samples T7 and T8 when pH was increased from 4.0 to 5.0 at the same level of chitosan concentration dissolution. The decrease in the ability of emulsification is principally due to the aggregation of proteins in fish induced by pH lowering, which reduces the charge on the protein, causing the stabilizing layer of emulsion to collapse.^36,37 However, when T5 and T7 were compared at the same pH and with a higher chitosan concentration, ES was found more in samples with lower concentrations. This could be due to the fact that only fixed volume chitosan dissolution is possible at a particular pH, exceeding which can cause charge inactivation to impart higher ES. This proves that the added chitosan cannot fully stimulate the required activity at fixed pH ranges when the pH is too acidic.³⁸

3.2.3. Influence of pH and Chitosan on the WHC

pH is an important parameter that determines the ability of muscle proteins to hold water.¹⁵ Chitosan is solvable in weak solutions of organic acids like citric acid and behaves like a non-Newtonian solution.³⁹ Dissolution of chitosan as a polycationic polymer in any acidic solution (pH below 5.5) protonates its amino group, assigning it a positive charge.⁴⁰ This indicates that maximum chitosan activation is held around this pH, where stronger cross-linking occurs between the amino group of chitosan and fish protein, forming an intact matrix entangling maximum water.^31,41 According to samples T5 and T7, the ability of chitosan to hold water reduces as its concentration rises within a certain pH range. Water retention capacity was determined to be higher at higher pH levels. Figure 1C,F displays that extreme pH ranges and chitosan values produce maximum values of WHC with the highest desirability when all three response parameters are simultaneously observed. However, when WHC is tested singly, practically the whole pH range along with lower-middle to higher-extreme chitosan values yields the highest values of WHC. Irreversible changes are common at pH below 4.5, when meats are marinated in food acids along with their salts that negatively affect the capacity of meat proteins to conserve their own water. A lower pH of 4.0 or lower can further restrict the ability of chitosan to activate, weakening its charged amino groups.⁴²

3.3. Effects on the Process Parameters of Sausages

3.3.1. pH

The pH of any food product is one of the prime parameters in accessing the final product quality specifically its texture, which is well established in various previous studies.⁴³⁻⁴⁵ Chitosan dissolution with citric acid lowered the pH values of chitosan–acid gel treated emulsion sausages which is similar to previous studies conducted on fish products by Lopez-Caballero et al.¹⁸ and Xavier et al.¹⁹ In this study, the typical pH range for all the sausage combinations was around 6.0 (Figure 2). Because of its meat-buffering capability via its three pK_a values and other available carboxylic groups when adhered to meat surfaces, citric acid cannot cause significant decreases in meat pH.¹⁵

Figure 2.

Variations in pH, cooking loss, and purge loss of sausages incorporated with citric acid–chitosan gel at various pH levels.

3.3.2. Cooking Loss

Cooking loss is defined as the expellation of water and fat from heated products, which can determine the ability of any system to bind the required water and fat globules after denaturation and aggregation of the existing protein.⁴⁶ Lower cooking loss specifies a higher cook yield, resulting in a preferable valued stable product.⁴⁷ Chitosan is known to contribute toward the reduction of water and weight in meat foods during thermal processing like other additives (microcrystalline cellulose, CMC seaweeds, gelatin, collagen, etc.).^21,34,48 Experimental results as per the study had a minimal cooking loss between 0.19 and 0.7%, which is displayed in Figure 2. At a fixed pH of 4.5, incorporating the highest and lowest chitosan concentrations (samples-T3, T4) gave the cook loss values nearer to the highest observed range, that is, 0.7%. Furthermore, at a fixed chitosan concentration of 0.15 g, with different pH of 4.0 and 5.0 (samples-T5, T6), it was noticed that low pH notably contributes to reduced cook loss values, which was also noted from sample T1 having the lowest pH. A similar finding was also noted in an earlier study with processed burger meat, where higher citric acid incorporation significantly reduced the cooking loss, which was principally suggested owing to the higher water-binding ability of muscle proteins due to the swelling effect caused by acid incorporation.⁴⁹

3.3.3. Purge Loss

The quantity of fat and water swept out from meat during a specific timeframe is defined as purge loss.²³ An initial purge loss of 0.18 to 0.69% was noted from the fresh samples according to this experiment which indicates good stability of the fish meat matrices (Figure 2). Similar minimal ranges of purge loss was also reported in emulsion-based gels in low-fat frankfurters prepared with blends of vegetable oils and numerous gelling agents.^50,51 The lowest purge loss value of 0.18–0.21% was observed at a fixed chitosan concentration of 0.15 g at both pH 4.0 and 5.0 (T5 and T6). For other combinations, no typical trend was observed with respect to either chitosan or pH; instead, an interactive effect was noted. At the lowest chitosan concentration, purge loss is effectively reduced; however, too much acidic pH cannot entirely activate the chitosan added to impart its necessary functionality at each pH ranges.³⁸

3.4. Textural Attributes

Analysis of the textural parameters of sausages by instrumental methods is carried out using a texture profile analyzer that provides an extensive idea of the various deformation and gel properties of any food. Hardness scores are technically increased due to the loss of water from the sausage parts during compression cycles.⁵² Hardness was higher among the low pH range treatment groups with chitosan incorporation of the same concentration. However, at the same chitosan concentration, hardness was lowest among all the treatments at the highest pH of 5.2 (T2). Overall, in most treatment combinations, a variable interactive effect of pH and chitosan was observed, as displayed in Table 5. The result might be attributed to the reduced pH, which may have increased the hardness of the sausages due to the emulsion destabilization triggered by water and fat segregation from the protein matrix.⁴⁴ Cardoso et al.⁵³ also noted a similar finding in cod sausage added with the hydrocolloid carrageenan having a lower pH, which was attributed to higher hardness. A study conducted by Desmond and Troy⁵⁴ also suggested a lower tenderness in citric acid incorporated beef sausages at lower levels as higher concentrations can deteriorate the meat functionality. The cohesiveness values were witnessed to be reasonably higher at elevated pH ranges.⁴³ Conversely, the springiness values in this experimentation were noticeably higher at a lower pH range (3.8–4.0) with relatively high chitosan incorporation levels (0.225–0.3 g), that is, samples T1 and T7. Values for gumminess and chewiness were found to be lowest for T2 samples having the highest pH of around 5.2 and a chitosan application of 0.225 g and were found to be the highest for T4 samples having a lower pH of 4.5 and the highest chitosan concentration of 0.33 g. This is in line with the findings of Gu et al.¹⁰ in restructured fish meat.

Table 5. Textural Parameters of Emulsion Sausage Prepared by Citric Acid Made Chitosan Gel Incorporation at Different pH Conditions^a.

	textural parameters
treatments	hardness I (N)	hardness II (N)	springiness (mm)	cohesiveness	gumminess	chewiness
T1	60.29 ± 0.73	65.25 ± 1.20	0.88 ± 0.02	0.74 ± 0.04	48.18 ± 1.68	42.4 ± 0.44
T2	51.2 ± 1.28	54.32 ± 1.31	0.92 ± 0.03	0.81 ± 0.02	43.96 ± 1.23	40.54 ± 2.44
T3	56.75 ± 0.98	60.15 ± 1.07	0.93 ± 0.02	0.81 ± 0.02	48.60 ± 0.74	45.3 ± 0.95
T4	68.79 ± 0.60	74.13 ± 0.63	0.92 ± 0.01	0.75 ± 0.04	55.52 ± 0.55	51.3 ± 0.41
T5	63.05 ± 0.17	67.04 ± 0.18	0.91 ± 0.04	0.79 ± 0.02	52.69 ± 0.01	47.79 ± 1.93
T6	61.03 ± 1.27	65.87 ± 1.04	0.91 ± 0.02	0.82 ± 0.05	55.48 ± 3.8	50.52 ± 3.11
T7	61.75 ± 1.09	71.81 ± 1.50	0.86 ± 0.01	0.73 ± 0.02	52.26 ± 1.26	49.08 ± 1.02
T8	58.13 ± 1.94	61.96 ± 2.08	0.9 ± 0.02	0.79 ± 0.02	48.77 ± 1.73	44.08 ± 0.70
T9	61.92 ± 1.16	66.47 ± 1.19	0.91 ± 0.01	0.76 ± 0.01	50.57 ± 0.97	46.14 ± 0.86
T10	62.63 ± 1.03	67.28 ± 1.32	0.93 ± 0.01	0.76 ± 0.01	51.06 ± 0.53	47.35 ± 1.20
T11	62.59 ± 1.05	66.99 ± 1.27	0.91 ± 0.04	0.75 ± 0.01	50.99 ± 0.89	46.89 ± 0.99

^aValues conveyed as the mean ± standard deviation (taking n = 3).

3.5. Sensory Assessment

Sensory assessment is précised as the dimension of umpiring food quality by the sensorial traits that include taste, smell, sight, and touch.⁵⁵ All 11 combinations of sausages were assigned respective tallies according to the hedonic scale standards, which are displayed in Figure 3. As per the results, all the sensory grades were judged similarly in terms of color and appearance. Samples with lower end pH (T1, T5, and T7) had a mildly acidic, tangy taste that reduced their final overall acceptability scores compared to the other samples at higher pH, the scores being highest for samples T2 and T6. Reduced meat products’ pH is responsible for imparting such tangy sour flavors, thereby creating higher consumer repulsions. Higher pH can eliminate such complications and have better acceptability, which was also concluded from our study considering three response parameters. Studies on citric acid inclusions in meat sausages have shown similar flavor scores, indicating higher sourness.⁵⁶ Citric acid-treated beef and turkey breast cuts have also been found to have lower flavor scores in sensory evaluations.^54,57

Figure 3.

Sensory parameters depicted as radar diagram for fish emulsion sausages prepared with chitosan gel in citric acid at different pH conditions.

4. Conclusions

Incorporating hydrocolloids like chitosan at a minimal level may positively enhance the quality features in meat sausages when added as food components, primarily when solubilized in organic food acids. Therefore, when the range of the chitosan concentration and pH is scientifically optimized before inclusion, attention must be paid to ensure that the sensory and textural attributes are not significantly impacted. The optimal range of chitosan for improving overall food functionality is only 0.15 g when dissolute at pH 5.0. In addition to being affordable and reliable goods in the consumer sphere, products produced through scientific optimization, specifically from low-cost fish species, deliver improved acceptability in terms of overall quality traits.

Author Contributions

K.C.—data investigation and writing the initial draft preparation; M.X.—conceptualization supervision, reviewing, and editing; S.N.—software application and manuscript editing; S.K.—data investigations; A.B.—review and supervision; and B.B.N.—project administration supervision.

The authors declare no competing financial interest.

Notes

The sensory evaluation was conducted in accordance with the principles embodied in the Institute of Food Science & Technology (IFST) guidelines. All participants gave written informed consent to participate in the study.