# Influence of Pre-Treatment on the Seasonal Variation of Smoked Baltic Strat Texture and Color
## 1 Introduction  
Baltic sprat (_Sprattus sprattus balticus_) is a fast-growing, short-lived fish from the _Clupedae_ family, typically reaching a size of 10-16 cm [1]. It is recognized as a valuable source of proteins and lipids [2]. The spawning season in the Baltic Sea generally spans from March until June, depending on the weather conditions [1]. The catching season, geographical location, fish size, weight, and age affect the chemical composition of sprat [3]. The protein content remains relatively stable throughout the catching period. However, [PERSON] et al. [4] documented a substantial variation in the lipid content, ranging from 5.10% during the spawning season to 15.46% in the fish-feeding season. [PERSON] et al. [5] identified a strong negative correlation between the water and lipid contents in Baltic sprat. This variance in the chemical composition may lead to changes in sensory attributes, resulting in a higher sensory quality of autumn fish having the highest lipid content compared to fish caught in other seasons (winter and spring). Following catching, fish undergo fast freezing as a preservation method to maintain their quality throughout the supply chain, extending their shelf-life up to 12 months. This practice ensures a continuous supply during the non-catching season. Freezing effectively slows or stops biological, chemical, and physical changes in fish. However, enzymatic activity linked to lipid oxidation can lead to the degradation of food quality attributes such as color, taste, and texture. Additionally, the freezing and thawing process introduces structural damage from ice crystals with potential impacts on the ultimate quality of the final product [6]. The freezing process can induce the denaturation andaggregation of proteins, diminishing their extractability. This, in turn, may contribute to muscle toughening and a decrease in the water-holding capacity [7]. Baltic sprats have widely been used to produce various nutritionally valuable products including smoked, salted, marinated, and canned sprats. Traditionally, the preservation of fish and the enhancement of their sensory attributes have been achieved through salting and smoking [8]. However, the predominant methods for fish preservation are canning and freezing [9]. In the Baltic and Eastern European countries, canned smoked sprats in oil are known as a local delicacy. Furthermore, innovative products have emerged from smoked sprat, such as dried smoked sprat snacks, marinated smoked sprat preserves, and smoked sprat pate. During the smoking processes, the increased temperature leads to protein denaturation, potentially resulting in a softer texture, particularly in spring, when fish contain a higher water content. The varied lipid content may lead to differences in the water distribution. Therefore, to ensure an acceptable texture in smoked sprats, raw fish should possess sufficient firmness, influenced by such factors as the fat and moisture content, pH, storage time, and processing methods. The ionic strength and pH play crucial roles in the water-binding ability of muscle proteins; the addition of a low amount of salt (1-2%) can enhance the water-holding capacity. A 2-5% NaCl brine causes myosin to swell strongly, leading to firmer binding in tissues [7]. After salting and smoking, the structural properties of the fish are altered, and shrinkage of the muscle fibers occurs [10]. The salting and smoking processes contribute to a reduction in the lightness value L*, attributed to water loss and protein degradation [2]. While no studies on factors affecting the smoked sprat color were found, [PERSON] et al. [2] reported that marinated sprats were lighter, with a decreased redness compared to that of thawed sprats used as raw material. This phenomenon was linked to the effects of acids, as reported by [PERSON] et al. [11], which influenced discoloration and increased the autooxidation of myoglobin in the fish tissue.