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Fresh sea squirt meat requires a modified processing and preservation process because it has a short shelf life due to its high mois ture content and strong proteolytic enzyme activity. In this study, bottled sea squirt meat prepared in vegetable oil (BSMO) to enhance the consumer acceptability was exposed to γ-ray (Co60, 10 kGy/h) irradiation to extend the shelf life without the use of a heating process. Response surface methodology was used to determine the optimal mixing ratio of BSMO containing 5% dehydrated fresh meat. Texture analysis and nutritional evaluation were also performed on a control and BSMO samples. The volatile basic nitrogen (VBN) content and total cell count were measured to determine the shelf life of irradiated BSMO products during chilled storage at 4°C for 60 days. According to a panel of 10 trained tasters (aged 20-29 years), the optimal mixing formulation was 80 g meat in 60 mL of mixed vegetable oil (30 mL of olive oil and 30 mL of sesame oil). The highest rated formulation, according to a panel of nine trained tasters (aged ≥30 years), was 80 g meat in 60 mL of mixed vegetable oil (42 mL of olive oil and 18 mL of sesame oil). Moisture, ash, and protein contents in BSMO did not change significantly ( P < 0.05) compared with the control. A higher lipid content (0.84 ± 0.23 to 2.13 ± 0.61; P < 0.05) was observed due to the presence of vegetable oil on the surface of BSMO. The vegetable oil raised the hardness, springiness, cohesiveness, gumminess, chewiness, and resilience of BSMO. BSMO products remained edible after 50 days of storage at 4°C based on the VBN content (BSMO 1: 27.92 ± 0.96 mg/100 g, BSMO 2: 24.84 ± 1.95 mg/100 g) and total cell count (BSMO 1: 4.60 ± 0.80 log CFU/mL, BSMO 2: 3.65 ± 0.20 log CFU/mL) when compared with standard levels of VBN (25.00 mg/100 g) and total cell count (5 log CFU/mL), respectively. The results showed that irradiated BSMO products could help to expand the processed seafood market and increase the popularity of seafood among the younger generations.

【This study was carried out to investigate nutritional and physiologically active characterizations of sikhae and the seasoned products from the sea squirt Halocynthia roretzi. The total taste values of sikhae fermented for 4 and 5 days were 10.9 and 15.4, respectively, which was lower than for commercially seasoned sea squirts. The sikhaes contained mostly glutamic and aspartic acids. The total amino acid contents of sikhaes fermented for 4 and 5 days were 5.5 and 6.0 g/100 g, respectively, which were lower than those of commercial seasoned-sea squirts or similar. An amount of 100 g of sikhae and its seasoned products contained P, K, Mg and Fe, and these minerals, which are deemed good for our health, were at 10% above the recommended daily requirements. The functional properties of sikhae fermented for 4 and 5 days were as follows: for ACE inhibiting activity, 69 and 69.5%, respectively; for antioxidative activity, 28.9 and 29.3%, respectively; for xanthine oxidase inhibitory activity, 52.8 and 53.1%, respectively; and for ${\alpha}$ -glucosidase inhibitory activity, 2.4 and 1.4%, respectively. Antimicrobial activity of the 5 day fermented sikhae against Vibrio parahaemolyticus and Staphyloccus aureus was detected in 8 mm and in 7 mm against Escherichia coli.】

In order to understand the co-culture impact of the sea squirt Halocynthia roretzi on the Pacific oyster Crassostrea gigas, we examined the filtration rate of the sea squirt in relation of water temperature () and body weight. The filtration rate increased in relation to body weight and water temperature, indicating a clear positive correlation with the two variables. Due to the clear positive correlation between filtration rates at each temperature groups for acceptable collinearity, each constants at regression equation was further analyzed for a unified model of filtration rate. Therefore the filtration rate of H. roretzi was estimated as: Fr (L/h/animal)

We examined the effect of starvation on the occurrence of tunic softness to determine the cause of mass mortality of cultured Halocynthia roretzi (Drasche) in the Tongyeong region, Korea. In terms of the survival rate of H. roretzi and the occurrence rate of tunic softness, H. roretzi starved for 35 days at water temperatures of 8, 12, and (room temperature of ) did not exhibit tunic softness at water temperatures of either or . for morphological changes, although the tunic of H. roretzi was shrunken and became visibly smaller with a darkening color in all experimental groups, as compared to the state prior to starvation, its tunics bulbs continuously. The ratio of RNA/DNA concentrations and protein contents for each of the tunic sections were lower in the starved group. Our results indicate that tunic softness is not related to feeding deficiency, as no histopathological symptoms were apparent in the digestive gland or tunic of H. roretzi due to starvation.

This study investigated the food biochemical characterization of commercial seasoned sea squirt Halocynthia roretzi (CSS). The proximate composition of CSS was 77.2-82.7% moisture, 7.1-9.1% crude protein, 0.3-2.6% crude lipid and 3.5-6.3% ash. Taste compound contents of CSS were 2.3-5.4% salinity (saltiness), 0.42-1.12 g/100 g total acidity (sourness) and 114.9-330.2 mg/100 g amino nitrogen (taste intensity). The Hunter color values of CSS were 23.79-32.50 for lightness, 9.97-20.45 for redness, 14.01-20.96 for yellowness and 64.50-76.63 for color difference. The odor intensity of CSS was 35.0-62.0. According to these results, there were large differences in proximate composition, taste compounds, Hunter color values and odor intensity of CSS. Viable cell counts ranged from 6.20 to 7.69 log (CFU/g), and most of the viable cells comprised of lactic acid-forming bacteria. CSS was not detected in the coliform group.

This study was conducted to develop and characterize sea squirt Halocynthia roretzi sikhae. According to the results for pH, total acidity, lactic acid bacteria, amino nitrogen and sensory evaluation of sea squirt sikhae during fermentation for 6 days at , the optimum fermentation periods were 4 days for sourness-disliking customers and 5 days for sour-disliking customers. No differences in the proximate compositions of sea squirt sikhaes fermented for 4 days (4D) and for 5 days (5D) were found. There was a difference in the eproximate compositions of commercial seasoned sea squirts, 4D and 5D, sea squirt sikhaes. The results of salinity, total acidity, amino nitrogen and sensory evaluation of two kinds of sikhae suggest that the taste was stronger for 5D than for 4D, both of which were superior to commercial seasoned sea squirts. There was, however, no difference in color of 4D, 5D and commercial seasoned sea squirts. The results of E. coli analyses suggest that sea squirt sikhae is a safe food in terms of sanitation.

The hemocytes of the tunicate Halocynthia roretzi are classified into six types based on their size, cellular form, and fine structure of the cytoplasmic granules: hyalinocytes, granulocytes, phagocytes, nephrocytes, morula cells, and multi-vacuole cells. Based on cell size, they are ordered multi-vacuole cells ()>nephrocytes ()>phagocytes ()>granulocytes ()>morula cells ()>hyalinocytes (). The proportion of hemocytes is ranked in the order multi-vacuole cells (54.8%)>nephrocytes (16.9%)>granulocytes (9.9%)>morula cells (8.8%)>phagocytes (6.1%)>hyalinocytes (3.5%).

【The sea squirt Halocynthia roretzi is mainly cultured in Tongyeong, Southern coastal area of Korea. This study presents the physiological rates of respiration, excretion, feeding and assimilation efficiency of the sea squirt Halocynthia roretzi to analyze the SFG(scope for growth) and net growth efficiency, determined during 2007. Oxygen consumption and nitrogen excretion rates increased with a rise in temperature during the summer period whereas feeding rates decreased. The O:N ratio was high during winter(October to February). Assimilation efficiency showed an annual average of 75.4% during the experimental period, except during a period of elevated temperature in July to September(average $25^{\circ}C$ ). Net growth efficiency( $K_2$ ) was 8.7 to 64.2% except for May to September, when temperature increased at the aquaculture farm. SFG was negative from May to September, reflecting high temperatures and low feeding rates during this period; its highest positive values occurred during winter.】

To examine the functional properties of conjugated linoleic acid (CLA) and ascidian tunic extracts in fish, we compared mackerel fed ascidian tunic extract and CLA (CA25) and a control group. The daily growth index of CA25 was 1.92 compared to 1.86 in the control group. The viscerosomatic index of CA25 was 36.7% lower than that of the control group. After 8 weeks, the protein content decreased from 19.7 to 17.5% in the CA25 group. The ascidian tunic extract content in the viscera was much higher than in muscle (0.13 vs. 0.03 mg/100 g) after 8 weeks. At the start, the n-3 fatty acid content of the experimental fish was 25.2% in muscle and 23.7% in viscera. The CLA content in muscle in the CA25 group was 2.1% after 4 weeks and 2.3% after 8 weeks. By contrast, the CLA content in viscera did not change after 8 weeks.

This study examined the antidiabetic and antihyperlipidemic activities of an ascidian (Halocynthia roretzi) in rats in vivo. Rats were fed on experimental diet including dried ascidian powder (200 mg/kg body weight) for 4 weeks, and then the triglyceride and total cholesterol levels in blood were analyzed. On the ascidian tunic powder diet, the triglyceride level decreased by more than 20.9% and the total cholesterol content decreased by more than 24.4%. In comparison, the triglyceride and total cholesterol level in the blood of rats fed ascidian meat powder decreased only slightly. Therefore, the ascidian tunic powder might be a healthy food with antidiabetic and antihyperlipidemic effects.

To understand the effect of heated effluent from a nuclear power plant on marine organism, experimental culture of Halocynthia roretzi was carried out at heated effluent of Wolsung nuclear power plant from January to December 1996. Temperature was and salinity was during the culture period, The Growth of H. roretzi on lower area of Bonggil-ri (St. 1) was not normal in height, breadth and weight due to heated effluent. Daily growth rate (DGR) of H. roretzi about Kampo area (St, 4) was significant other station, and St. 1 was significant from other station except St. 4, Mytilus edulis was major fouling organism (over ) that were M. edulis, Dideninum moseleyi, Styela clava in experiment culture farm. St. 1 was higher (mean 143 individual) and St. 4 was lower (mean 56 individual) appearance attached of M. edulis. Growth of H. roretzi reduced when attached number of M. eduiis was increased, because correlation between DGR and number of M. edulis was negative.