# Effects of Various Extraction Factors on Protein Yield of Haliotis discus hannai (Abalone)
###### Abstract  
Abalone (_Haliotis discus hannai_) is a widely consumed seafood in Asian countries. Rich in protein, abalone is consumed for refreshment, pregnancy care, and vitality. Although many studies have found that abalone protein has beneficial effects, the efficiency of the protein extraction method for abalone has rarely been studied. Therefore, this study aimed to examine the effects of various factors of abalone protein extraction, including extraction buffer, sonication, salt (NaCl) concentration, surfactant, and heating. Phosphate buffer showed higher protein yield compared with Tris-HCl buffer. In addition, the highest protein yield for each factor was observed at 60 s of sonication (84.44 \(\mathrm{\SIUnitSymbolMicro g}\)/mg dw), 0.6 M NaCl (141.9 \(\mathrm{\SIUnitSymbolMicro g}\)/mg dw), and 16 mM sodium dodecyl sulfate (SDS) (253.15 \(\mathrm{\SIUnitSymbolMicro g}\)/mg dw). However, a combined effect was not observed. Lower protein extraction efficiency was observed for sous vide-coked abalone. The electrophoresis assay revealed myofibrillar proteins, including paramyosin, actin, and tropomyosin. Overall, our results demonstrate that various extract conditions affect the protein extraction of abalone. abalone protein; protein extracting factor; buffer; salt; surfactant +
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Abalone is among the most expensive seafood in the world. The high cost of abalone is attributed to its rarity and the complications of harvesting. The abalone firmly attaches to rocks by its muscular foot, which is responsible for the difficulties of obtaining it from the rocky outcrops where it lives. Therefore, the continuous demand for abalones has shifted the production from wild-caught to aquaculture, and over 95% of commercial abalone is produced by farming. Furthermore, advanced seedling production technology, aquaculture technology, and fishery conditions have increased the supply of abalone. However, shellfish, especially abalones, are vulnerable to harmful algal blooms (HABs). HAB is a typical natural phenomenon resulting from eutrophication, which may affect the global abalone supply chain [5]. As abalone is expensive seafood, it is occasionally consumed as processed food. In particular, it is processed to dried abalone and used as herbal medicine or made into a steamed jerky to enhance the protein and taurine content. The amount of protein in abalone cultured in Korea is about 10.44-11.10% [6]. Myosin heavy chain, alpha-chain collagen, myofibril, and actin are the primary proteins in the foot muscle of abalone [6]. Various studies have revealed that abalone has a different composition of nutrients, particularly the composition and content of protein and amino acids, depending on the aquaculture environment, farming methods, and feed [6,7]. The extraction method is critical in determining the quantity of protein present in food [8]. Abalone protein is a major nutritional component and constitutes the primary purpose of abalone food processing. Therefore, quality control through accurate protein quantification is critical for processed abalone. Various methods are used to extract proteins from food materials, such as enzyme-assisted extraction, ultrasonic-assisted extraction, microwave-assisted extraction, supercritical extraction, and pulsed electric fields [9]. In addition, various extraction factors are controlled to increase extraction efficiency, including the pH and type of extraction buffer, use of surfactants, and inclusion of salts. The bicinchoninic acid (BCA) assay is widely used to quantify protein [10,11]. Different protein extraction methods are adopted depending on the food materials, particularly their protein composition. In addition, the surfactant and salts added during the extraction will affect the downstream protein content analysis, resulting in imprecise estimation of protein contents [11,12]. Therefore, it is critical to develop suitable extraction conditions.