How thermal processing transforms bycatch into valuable nutritional resources
In modern fisheries, utilizing bycatch and processing waste has become a crucial focus for enhancing economic value and reducing resource waste. One highly valuable processed product from these byproducts is trash fish meal—a flour made from various small fish species, non-consumable fish, or fish parts typically considered waste.
What many may not realize is that behind the quality of the resulting fish meal lies a critical processing factor: steaming temperature.
The steaming process doesn't merely cook the raw materials but directly affects the protein structure, chemical composition, and physical characteristics of the resulting fish meal. The right steaming temperature can distinguish between high-quality fish meal with optimal nutritional value and an inferior product that may spoil quickly or be less nutritious.
Transforming low-value fish into nutritional resources
Steaming temperature determines final product quality
Understanding the physicochemical transformations
Trash fish meal is a processed product made from small fish, non-consumable fish species, or fish parts typically considered waste from bycatch. The term "trash" refers to the category of small-sized, low-economic-value fish, or mixed fish species that are not typically consumed directly by humans.
Although considered low-value for direct consumption, these fish contain high nutritional content, especially proteins, minerals, and essential fatty acids that can be utilized in various applications.
Processing trash fish into meal represents a sustainable resource utilization strategy that transforms potentially wasted materials into value-added products 7 .
The quality of fish meal is determined by a series of interrelated physical and chemical properties. These properties not only determine nutritional quality but also affect shelf life and practical applications of the fish meal.
Steaming is a heat treatment process with water vapor that aims to cook raw materials, deactivate destructive enzymes, and kill microorganisms that can cause spoilage. In the context of fish meal production, steaming is not merely a simple heating process but a complex interaction between temperature, humidity, and time that collectively affects the structure and composition of the material.
Temperature range causing protein changes
Critical points for soluble protein reduction
Optimal steaming temperature
From a scientific perspective, heat during steaming causes protein denaturation—changes in the three-dimensional structure of proteins that can improve digestibility but also affect their functional properties. Different temperatures will cause different levels and patterns of denaturation, which ultimately affect the quality of the final product.
Research on big head carp showed that different heating temperatures caused significant changes in muscle protein composition. The proportion of salt-soluble protein and water-soluble protein in cooked muscle decreased up to 50°C and 60°C respectively, while alkali-soluble protein increased with temperature in the range of 40-98°C 6 .
A study conducted in June-July 2014 at the Fisheries Product Processing Laboratory and Fisheries Chemistry Laboratory, Faculty of Fisheries and Marine Sciences, University of Riau, provided deep insights into the influence of steaming temperature on the quality of trash fish meal 3 . This study used a Completely Randomized Design (CRD) with three different steaming temperature treatments: S1 (100°C), S2 (90°C), and S3 (80°C).
Trash fish obtained from Tanjung Beringin Village, Rampah - North Sumatra, representing common trash fish types in Indonesian waters.
Fish were steamed at predetermined temperatures with strict temperature control.
Steamed fish were processed into meal and analyzed using internationally recognized standard methods.
The methodological steps in this study were designed to ensure data accuracy and result relevance to actual industrial conditions.
The research results revealed interesting and statistically significant patterns. Treatment with a steaming temperature of 80°C (S3) produced the best physical characteristics, while from a chemical perspective, it also showed an optimal nutritional profile compared to higher temperatures.
Higher water absorption indicates better hydration capacity, which is important in feed formulations as it affects the texture and stability of the resulting feed 3 .
From the chemical composition perspective, 80°C produced the highest protein content (50.95%) and lowest fat content (7.70%), indicating better nutrient retention and higher oxidative stability since lower fat reduces the risk of rancidity 3 . Lower moisture content at 80°C steaming temperature also suggests better storage potential as lower water activity inhibits microorganism growth.
The findings from this study have important implications for the fish processing industry, particularly in the production of trash fish meal. Selecting 80°C as the optimal steaming condition not only produces better quality meal but is also more energy efficient as it requires less thermal energy compared to 90°C or 100°C.
In a broader perspective, this study also supports sustainability principles in the fisheries industry by optimizing the utilization of bycatch through proper processing methods. By producing higher quality fish meal from trash fish, the economic value of materials previously considered waste or low-value can be significantly enhanced.
| Parameter | S1 (100°C) | S2 (90°C) | S3 (80°C) |
|---|---|---|---|
| Water Absorption (%) | 116.67 | 120.00 | 126.67 |
| Color Brightness | 30.33 | 32.00 | 33.67 |
| pH | 6.35 | 6.38 | 6.41 |
| Yield (%) | 15.80 | 16.35 | 16.90 |
Source: Research data from University of Riau 3
| Parameter | S1 (100°C) | S2 (90°C) | S3 (80°C) |
|---|---|---|---|
| Ash Content (%) | 18.25 | 17.99 | 17.72 |
| Moisture Content (%) | 7.80 | 7.65 | 7.51 |
| Protein Content (%) | 49.80 | 50.38 | 50.95 |
| Fat Content (%) | 8.25 | 7.98 | 7.70 |
| Crude Fiber (%) | 4.65 | 4.43 | 4.22 |
Source: Research data from University of Riau 3
Research on fish meal quality requires a range of specialized equipment and materials to ensure accuracy and reliability of results. Below are some key components in the fish meal researcher's "toolkit":
| Material/Equipment | Function and Application |
|---|---|
| Drying Oven | Removes moisture content from fish samples after steaming |
| Grinder | Transforms dried fish into fine meal |
| Soxhlet Extractor | Determines fat content through extraction with organic solvents |
| Kjeldahl Apparatus | Analyzes total protein content based on nitrogen |
| Combustion Furnace | Establishes ash content (mineral content) through combustion |
| pH Meter | Measures acidity level of fish meal |
| Colorimeter | Objectively assesses brightness and color of fish meal |
| Desiccator | Stores samples in dry environment during weighing |
Analytical methods used include thermogravimetry techniques for moisture content analysis, Kjeldahl method for protein determination, Soxhlet extraction for fat analysis, and combustion in a furnace for ash content determination 5 . Each of these methods has been standardized and internationally recognized, ensuring results comparable with other research in the same field.
Research on the influence of steaming temperature on the physicochemical properties of trash fish meal has revealed how critical temperature control is in the production process. A steaming temperature of 80°C proved optimal in producing trash fish meal with superior physical characteristics (higher water absorption, brighter color, higher yield) and superior chemical profile (higher protein, lower fat, lower moisture content) compared to higher temperatures.
These findings not only have academic value but also significant practical implications for the fish processing industry. By applying optimal steaming temperatures, producers can improve product quality, production efficiency, and economic value of trash fish that was previously often considered low-value material.
By continuing to investigate and optimize basic process factors like steaming temperature, we can unlock the full potential of these valuable fishery resources, support a sustainable feed industry, and significantly reduce food waste.