Albumin extracts from giant snakehead and snakehead were prepared according to Sari and Rahmawati (2022). The fish were cleaned by removing the scales, viscera, gills, fins, and head. The fish flesh was washed under running water and drained of excess water. The fish flesh was scored to facilitate albumin release during the extraction process. Lime extract (0.5% w/v) was added at a rate of 5 mL per 1 kg of fish flesh. The fish flesh was marinated for approximately 3 min to reduce the fishy odor. The marinated flesh was then washed and drained. Albumin extraction was conducted at for 10–12 h without the addition of solvents. The liquid released during the first 2 h was discarded because it mainly contained water from fish flesh. The albumincontaining extract was identified by its slightly sticky texture. The albumin extraction process was completed approximately 10 h after the initial 2 h phase.

Fish flour was produced according to the method described by Sari et al. (2014), with modifications. The raw material consisted of residual fish flesh obtained from albumin extraction of the giant snakehead fish and the snakehead fish. The residual fish flesh was separated from the bones and skin. The flesh was then shredded and spread evenly on an oven tray to a thickness of approximately 0.5 cm. The drying process was conducted at for approximately 5 h. During drying, the fish flesh was stirred after the first two hours. The flesh was then stirred every 30 min until the drying process was complete. Gentle manual pressing was performed during drying to prevent clumping. The dried fish flesh was then cooled to room temperature. The cooled material was then ground using a dry grinder. The ground material was then sieved through 230-, 200-, 120-, 60-, 50-, and 35-mesh sieves to determine the fish flour yield based on particle size.

The observed parameters included the yield, physical properties, chemical composition, and amino acid profile. Yield was determined according to (AOAC, 2005). The physical properties included color, solubility, and swelling power. The color was measured according to (Setyawardani et al., 2021). Solubility and swelling power were measured according to the method described by (Muchlisyiyah et al., 2016). Chemical analyses comprised the determination of protein content (BSI, 2006), moisture content (BSI, 2015), ash content, fat content, carbohydrate content (calculated by diference, 100% minus the sum of other components), and amino acid profile (AOAC, 2005).

The fish flour yield was calculated as the ratio of the fish flour weight to the residual fish flesh weight. The yield was calculated using Equation (1).

The color was measured using the CIE color scale with a Minolta CR-400 Chromameter. The measurements were performed using the CIELAB system. This analysis determined the color changes after processing. The CIELAB system consists of three parameters: The L\* value indicates lightness and ranges from 0, which represents black, to 100, which represents white. The value represents the green-to-red spectrum of the sample. The value represents the blue-to-yellow spectrum of the color. The color reader was turned on before the measurement. The sensor was placed on the surface of the sample. The test button was pressed to obtain , and values. Each sample was measured at three diferent points on its surface. Hue and chroma values were calculated using Equations (2) and (3)(Kamal-Eldin et al., 2020)

Solubility indicates the ability of fish flour to dissolve in water. Swelling power indicates the ability of fish flour to absorb water and expand its volume. A 100 g sample of fish flour was placed in a pre-weighed test tube. Distilled water (10 mL) was then added. The mixture was vortexed for 10 s. The sample was incubated in a water bath at for 30 min, with occasional stirring. The samples were then cooled in ice water until they reached ambient temperature. The suspension was centrifuged at 2,000 rpm for 30 min using a Frontier 5000 Series centrifuge (type: FC5706). The supernatant was transferred to a pre-weighed dish and dried in an oven until a constant weight was obtained. The weight of the dried supernatant was recorded as . The remaining residue in the test tube was weighed and recorded as ws. The swelling power and solubility were calculated using Equations (4) and (5), respectively.

Data were analyzed using an independent t-test to compare the two treatments: giant snakehead and snakehead fish flour. Physical and chemical analyses were performed in triplicate. The physical analyses included color, solubility, and swelling power measurements. The chemical analyses included protein, moisture, ash, fat, and carbohydrate content. Amino acid profiles were qualitatively and quantitatively analyzed. This analysis was performed on one sample from each treatment group. Therefore, the amino acid data are presented descriptively.

Yield is an important indicator of processing eficiency in fishery products. Yield describes the proportion of raw material converted to the final product (Nurfitriyani et al., 2024). The processing eficiency increases when a higher proportion of the raw material is retained as the product. Therefore, a high yield improves the economic value of fisherybased products (Senduk et al., 2022). Each species was prepared using 15 kg of fresh fish. Giant snakehead and snakehead each produced 10 kg of fish flesh, corresponding to a flesh yield of 66.67%. The albumin extraction process produced 1.5 L of albumin extract, corresponding to an extraction yield of 15%. This process also generates residual fish flesh as an extraction by-product. The residual flesh weighed 4.69 kg for giant snakehead and 4.68 kg for snakehead, corresponding to yields of 46.9% and 46.8%, respectively. The residual flesh was further processed into fish flour. The residual flesh of the giant snakehead produced 1.37 kg of fish flour, corresponding to a 29.21% yield of fish flour. The residual Snakehead dual flesh also produced 1.37 kg of fish flour, corresponding to a yield of 29.27%.

The fish meal yield is influenced by several processing factors, including drying, grinding, and sieving. In addition, the proportion of edible fish flesh significantly afects the final fish meal yield. In snakehead fish, the fillet accounts for approximately 47% of the total body weight (Niga et al., 2022). Similarly, in giant snakehead, flesh constitutes approximately 44% of the total body weight, resulting in a fish meal yield of 92.49% (Fakhriah, 2019). The yields of giant snakehead and snakehead flour based on particle size are presented in Table 1.

Particle-size-based yield observations were conducted to determine the particlesize distribution of the fish flour. The results showed that the largest proportion of particles from both fish species was retained on the 63 µm sieve (230 mesh). The yield of giant snakehead flour was 68.33±1.53 g (39.55±0.96%), whereas that of snakehead flour was 64.00±1.00 g (37.62±0.42%). These findings suggest that the majority of particles from both species were retained on the coarser sieves, indicating that the fish flour particles were relatively coarse. Fish flour contains high protein levels and has a complex matrix. This protein-rich matrix may reduce the grinding eficiency and limit the formation of finer particles. In general, fish flour has a dry texture with relatively uniform and fine particles. Particle size may also depend on nutritional components, particularly crude fiber, fat, and protein content (Purnamasari et al., 2018).

A reduction in sieve size (e.g., 500 µm or 35 mesh) resulted in a lower fish flour yield. The yield of giant snakehead flour was 0.77±0.40 g (0.44±0.23%), whereas that of snakehead flour was 0.80±0.35 g (0.47±0.21%). These results suggest that only a small proportion of particles were classified as very fine. The particle size can influence the sensory properties of processed products containing fish flour. However, Rahmaniar et al. (2023) reported that 60-, 80-, and 100- mesh particle sizes of snakehead fish flour did not significantly afect the moisture, protein, fat, ash, water absorption capacity, or oil absorption capacity.

The physical and chemical characterization used fish flour from the fraction with the highest yield, namely, the 63 µm fraction. The physical parameters included color, solubility, and swelling power of the starch. The chemical parameters, including protein, moisture, ash, fat, carbohydrate, and amino acid contents, are presented in Table 2.

The L\* value represents the lightness of the product. This value ranges from 0 to 100, where 0 indicates black and 100 indicates white color. Giant snakehead flour had an L\* value of 76.83±0.03, whereas snakehead flour had an L\* value of 72.68±0.51, respectively. The independent t-test indicated a significant diference between the two fish flours. The higher L\* value of the giant snakehead flour indicates a lighter color than that of the snakehead flour. Visually, both fish flours showed an of-white to ivory appearance; however, the giant snakehead flour appeared lighter than the snakehead flour. A previous study reported that biscuits fortified with 10% eel flour exhibited a higher lightness value (L\* ) than those fortified with 50% eel flour . The decrease in the L\* values with increasing proportions of eel flour was associated with a darker biscuit color (Wulandari et al., 2019).

The a\* value represents the greento-red spectrum. Positive values (0 to 80) indicate red hues, while negative values (0 to −80) indicate green hues (Fadlilah et al., 2022) Giant snakehead flour had an value of 2.74±0.07, whereas snakehead flour had an value of 3.68±0.02. The independent t-test indicated a significant diference between the two fish flours. The higher value of the snakehead flour indicates greater redness than that of the giant snakehead flour. The value represents the blue-to-yellow region of the color spectrum. Positive values (0–70) indicate yellow, whereas negative values (0 to −70) indicate blue. Positive values indicate yellowness, whereas negative values indicate blueness (Nanda et al., 2023). Giant snakehead flour had a b\* value of 24.45±0.08, whereas snakehead flour had a value of 22.88±0.26. The independent t-test indicated a significant diference between the two fish flours. The higher b\* value of giant snakehead flour indicates greater yellowness than that of the snakehead flour.

Hue was calculated from and b\* values. Hue indicates the dominant color position in the color spectrum, such as red, green, yellow, blue, and violet (Handayani et al., 2022). Giant snakehead flour had a hue value of 83.60±0.17, whereas snakehead flour had a value of 80.89±0.14. The independent t-test indicated a significant diference between the two fish flours. Based on the color classification reported by (Tager et al., 2021), both values fall within the yellow-red range. However, visual observations showed that both fish flours appeared ivory white. The Hue angle represents a color characteristic based on the light reflected from an object. In a previous study, biscuits fortified with eel flour exhibited hue angle values ranging from 14.9±0.99 to 22.15±0.78 (Wulandari et al., 2019). Increasing the proportion of eel flour fortification afected the Hue angle, resulting in a darker biscuit color. The yellowish-brown color observed in biscuits fortified with fish protein concentrate has been attributed to the Maillard reaction between reducing sugars and free amino acids (Abraha et al., 2018).

Chroma represents the color saturation or intensity. It ranged from 0 to 100%. Higher chroma values indicate more vivid colors, whereas lower values indicate duller or lesssaturated colors (Dakhi et al., 2024). Giant snakehead flour had a chroma value of 24.60±0.06, whereas snakehead flour had a value of . The independent t-test indicated a significant diference between the two fish flours. These low chroma values correspond to the pale and weakly saturated appearances of both fish flours. Color is an important quality indicator of fish flour. Color diferences may reflect variations in chemical composition and heat-induced reactions during processing. The protein contents of giant snakehead and snakehead flours were 76.97% and 77.96%, respectively. Fish flour with a high protein content generally exhibits a light brown to yellowish color. In contrast, excessive darkening may indicate a deterioration in quality due to Maillard reactions during heating (Farida et al., 2024). The addition of 5–15% tilapia fish flour to biscuits increased the chroma values (Chambó et al., 2017).

Solubility describes a material’s ability to dissolve in water. Swelling power describes the ability of flour to absorb water and expand its volume. This property is commonly expressed as the amount of water absorbed by 1 g of material under high-temperature conditions with excess water (Ansharullah & Hermanto, 2021). Giant snakehead flour had a solubility of 21.00±1.00%. The solubility of snakehead flour was 22.00±1.73%. The independent t-test indicated no significant diference between the two fish flours Table 2. The comparable solubility values may be related to the similar particle size characteristics and protein-rich matrix structure of both fish flours. The particle size of fish flour from both species tended to be relatively coarse, with most particles being large. Fish flour contains a complex and elastic protein matrix that may limit water penetration and solubilization (Purnamasari et al., 2018). The particle size can influence flour solubility. Smaller particles generally provide a greater surface area, which improves water penetration and the interaction between the solid matrix and water (Lee et al., 2021).

Protein content also strongly influences flour functionality, including solubility, flavor binding, emulsification, viscosity, gelation, texture formation, and dough development. Therefore, proteins are key components that determine the functional characteristics of food products (Alfaro-Diaz et al., 2024). Proteins are the main factor determining solubility because they contain polar groups that bind water more efectively than other components (Zhang et al., 2019). In animalbased materials, proteins contribute more significantly to solubility than carbohydrates. Carbohydrates in animal tissues are present in limited amounts and are generally less soluble; thus, their contribution to solubility is relatively small (Liu et al., 2022).

Giant snakehead flour had a swelling power of 1.09±0.46%. Snakehead flour had a swelling power of 0.85±0.20%. The independent t-test indicated no significant diference between the two fish flours Table 2. The swelling power values of both fish flours were low. A low swelling power indicates limited water absorption and expansion capacity. Therefore, food products formulated with these flours may exhibit a firmer or denser texture. The protein content of flour can influence its functional properties, such as water absorption and swelling power. Proteins can influence the swelling power by interacting with starch and afecting the ability of starch granules to absorb water and expand during heating (Setiavani et al., 2024). The ability of flour to swell at low temperatures supports its use as a cold-swelling ingredient and thickening agent. Rapid swelling may also help form an instant matrix that supports protein particles and other ingredients in the formulated foods (Dobson et al., 2022).

Giant snakehead flour had a protein content of 76.97±0.46%. The protein content of the snakehead flour was 77.96±0.25%. The independent t-test indicated a significant diference between the two fish flours Table 2. Both values met the Indonesian National Standard for fish flour, which requires a minimum protein content of 65% (BSN, 1996). The nutritional composition of fish meal is influenced by several factors, including fish species, freshness of the raw material, body parts used, and processing methods. Diferent fish species produce fish meals with varying nutritional qualities owing to diferences in their proximate composition. Fresh fish generally yield fish meals with higher protein quality than fish that have undergone quality deterioration. In addition, the use of whole fish typically results in fish meal with a higher protein content than fish meal produced from processing by-products such as heads, bones, skin, and viscera (Ahmed et al., 2022).

Processing conditions also play a critical role in determining the nutritional quality of fish meals. Excessively high drying temperatures or prolonged drying times may cause protein denaturation and accelerate lipid oxidation, thereby reducing the nutritional value of fish meals (Rasul et al., 2022). Previous studies have reported variable protein contents in snakehead fish flour. (Permatasari et al., 2021) reported that oven-dried snakehead flour contained 79.62% protein after drying at for 8 h, while Wirawan et al. (2018) reported a protein content of 65.3%. (Dewantara et al., 2019) reported protein contents of 88.27% and 50.70% in diferent snakehead fish flour products. (Syafii & Fajriana, 2022) reported that penja fish flour contained 62.32% protein after drying at for 24 h. The high protein content of fish flour reflects the abundance of essential amino acids in fish muscle proteins (Rahmaniar et al., 2023).

Moisture content afects the texture, appearance, flavor, freshness, and shelf life of food (Mikdarullah et al., 2020). Giant snakehead flour had a moisture content of . The snakehead flour had a moisture content of 13.53±0.13%. The independent t-test indicated a significant diference between the two fish flours Table 2. The moisture values obtained in this study exceeded the limits set by the Indonesian National Standard for fish flour. BSN (1996) specifies a maximum moisture content of 10% for grade I fish flour and 12% for grades II and III fish flours. Giant snakehead flour slightly exceeded the grade I limit but met the limits for grades II and III. Snakehead flour exceeded the specified limits for all three grades of fish meal.

Moisture content afects the texture, appearance, flavor, freshness, and shelf life of food (Mikdarullah et al., 2020). Moisture variation among fish flours can result from diferences in species characteristics and processing conditions of the fish. Pressing, drying temperature, drying duration, and storage conditions strongly influenced the final moisture content. Higher drying temperatures generally promote faster evaporation and produce lower moisture content (Farida et al., 2024). Fish flour is hygroscopic, meaning that it easily absorbs moisture from the environment (Valentina et al., 2021). Previous studies have reported diferent moisture contents in snakehead fish flour. (Wirawan et al., 2018) reported a moisture content of 10%. (Dewantara et al., 2019) reported a moisture content of 4.33%. (Permatasari et al., 2021) reported a moisture content of 11.05%. (Orlan et al., 2019) reported a moisture content of 18.86% in skipjack fish flour. Ambarwati (2024) reported moisture contents of 7.41%, 5.01%, and 5.21% in catfish, African catfish, and tilapia fish flours, respectively.

The ash content represents the total mineral residue remaining after complete combustion. Fish contain minerals such as calcium and Mg. Giant snakehead flour had an ash content of 3.36±0.03. The ash content of the snakehead flour was 3.49±0.03%. The independent t-test indicated a significant diference between the two fish flours Table 2. The ash content of fresh giant snakehead fish was 4.68%, whereas processing it into fish flour increased the ash content to 7.51%. This increase can be attributed to the drying process, which removes moisture from the raw material and consequently increases the concentration of solids, including mineral constituents (Fakhriah, 2019).

The mineral content varies by species and tissue composition. Processing methods, especially drying, can also afect ash content because water removal concentrates the mineral components in the final product (Farida et al., 2024). The mineral content of C. striata is influenced by its habitat. As a benthic species, snakehead fish inhabit the bottom of aquatic environments and consume sediment (mud) as part of their diet. This feeding behavior may contribute to the relatively high mineral content observed in snakehead fish (Asfar, 2018). Previous studies reported ash contents of 2.94% and 3.80% in snakehead fish flour (Wirawan et al., 2018; Dewantara et al., 2019). (Ambarwati, 2024) reported ash contents of 2.01%, 2.99%, and 2.23% in catfish, African catfish, and tilapia fish flours, respectively.

Giant snakehead flour had a fat content of 7.12±0.10%. Snakehead flour had a fat content of 1.74±0.16. The independent t-test indicated a significant diference between the two fish flours Table 2. Both values met the Indonesian National Standard for fish flour, which specifies a maximum fat content of 12% (BSN, 1996). Previous studies have reported variable fat contents in snakehead fish flour. (Wirawan et al., 2018) reported a fat content of 13.81%. (Dewantara et al., 2019) reported a fat content of 3.48%. (Ambarwati, 2024) reported fat contents of 4.58%, 8.10%, and 4.31% in catfish, African catfish, and tilapia fish flours, respectively. Fat content strongly afects fish flour quality. High fat content can accelerate lipid oxidation and increase rancidity during storage (Farida et al., 2024; Orlan et al., 2019). In contrast, particle size does not significantly afect fat content in fish flour (Rahmaniar et al., 2023)

Giant snakehead flour had a carbohydrate content of 2.15±0.75%. The carbohydrate content of the snakehead flour was 0.27±0.04%. The independent t-test indicated a significant diference between the two fish flours Table 2. Previous studies reported carbohydrate contents of 21.83% and 2.07% in snakehead fish flour (Wirawan et al., 2018; Dewantara et al., 2019). (Ambarwati, 2024) reported carbohydrate contents of 4.34%, 7.30%, and 7.01% in catfish, African catfish, and tilapia fish flours, respectively. Carbohydrate content was calculated using the by-diference method. This method estimates the carbohydrate content by subtracting the measured protein, moisture, ash, and fat contents from 100%. Therefore, carbohydrate values strongly depend on the levels of other proximate components. Higher carbohydrate values occur when the measured protein, moisture, ash, and fat contents are lower, whereas lower carbohydrate values occur when these components are higher (Matsuo et al., 2019).

Amino acid analysis was conducted to determine the amino acid composition of the fish flour produced from albumin extraction byproducts. Table 3 shows that snakehead flour has a higher total amino acid content than giant snakehead flour. Snakehead flour contained 87.23% total amino acids, whereas giant snakehead flour contained 72.32% total amino acids.

Amino acids contain two main functional groups: carboxyl (-COOH) and amino (-NH₂) groups (Yuanita et al., 2025). Amino acids form proteins, serve as precursors of metabolic compounds, and bind to metal compounds during enzymatic processes. Therefore, the amino acid composition determines the nutritional quality and functional value of protein-rich food materials. The protein quality depends on the type and proportion of amino acids in a food product. The nutritional composition of fish varies according to internal and external factors. Internal factors include species, sex, age, and reproductive phases. External factors include habitat, feed availability and water quality (Fitriliyani et al., 2019). The processing conditions can also afect the amino acid composition. Fish flour processing has been reported to influence the amino acid profile of the swamp barb fish (Adawyah et al., 2020). (Sumandiarsa et al., 2020) reported that steaming preserved essential and nonessential amino acid proportions in cooked skipjack tuna more efectively than pressure cooking and steam pre-cooking did.

The three dominant essential amino acids in both fish flours were lysine, leucine, and valine, respectively. Giant snakehead flour contained 6.61% lysine, 6.78% leucine, and 4.12% valine content. Snakehead flour contains higher levels of these essential amino acids, with 8.66% lysine, 8.40% leucine, and 5.45% valine. Essential amino acids and glutamine regulate muscle and whole-body protein anabolism. These amino acids also support immune function and maintain cellular and physiological homeostasis, particularly under hypercatabolic conditions, such as surgery, cancer, and intensive care (Negro et al., 2024). Insuficient intake of essential amino acids can disrupt metabolic processes and impair linear growth in children (Nurbaiti et al., 2023). Lysine supports growth and tissue repair, whereas leucine supports growth in infants and children.

The three dominant non-essential amino acids in both fish flours were glutamic, aspartic, and alanine. Giant snakehead fish flour contained 14.02% glutamic acid, 7.98% aspartic acid, and 5.72% alanine. Snakehead flour contains higher levels of these amino acids, with 17.05% glutamic acid, 9.47% aspartic acid, and 7.04% alanine. Glutamate, aspartate, and glycine contribute to the savory taste of food products (Chan et al., 2023). Aspartic acid contributes to the aroma and taste of food during processing. Glutamic and aspartic acids contribute to seafood flavor. Their sodium salts, including monosodium glutamate, produce an umami taste (Tamaya et al., 2020). Umami is considered a savory taste because it enhances the overall flavor of food, especially protein-rich sources (Wang et al., 2020). It also strengthens sweetness and saltiness while reducing bitterness (Schmidt et al., 2021).