Quantification of the Flavor and Taste of Gonads from the Sea Urchin Mesocentrotus nudus Using GC-MS and a Taste-Sensing System.

Sea urchin gonads are a delicious seafood item of high commercial value. Our past studies have revealed that the gonads of the sea urchin Mesocentrotus nudus fed the basal frond portion of fresh Saccharina kelp (BS) or the sporophylls of fresh Undaria (SU) during May-July are of high-quality. The present study investigated the flavor and taste of BS and SU gonads in comparison with those from non-fed M. nudus (NF) using gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC)-sniffing techniques, and a taste-sensing system. Data of the estimated intensity of taste (EIT) were compared with assessment of gonads from M. nudus collected from an Eisenia bed (fishing ground) and a barren in July. Gonads from both BS and SU released pleasant green, sour, and fruity aromas characteristic of butyl acetate, which are here recognized essential flavor components of high-quality gonads. The gonads of BS and SU had a strong umami taste compared to those of NF, and the Eisenia bed and the barren. The most marketable M. nudus gonads were assessed to be those with green and fruity aromas from butyl acetate, sweet aroma from benzaldehyde, umami EIT > 13.8, bitterness EIT < 3.1, and without any unpleasant sulfurous odor from sulfur-containing compounds.

Odor-active compounds from the gonads of Mesocentrotus nudus sea urchins fed Saccharina japonica kelp.

Gonad size, color, texture and taste of Mesocentrotus nudus sea urchins collected from a barren can be improved by a short-term cage culture while being fed fresh Saccharina japonica kelp during May-July. We investigated the effect of S. japonica feeding during May-July on the improvement of gonad flavor in M. nudus collected from a barren. After feeding, we analyzed the odor-active volatile organic compounds (VOCs) from the gonads using gas chromatography-mass spectrometry and GC-sniffing analyses and compared to those from the gonads of wild sea urchins from an Eisenia kelp bed (fishing ground) and a barren. A total of 48 VOCs were detected from the gonads of cultured and wild sea urchins. Of them, a larger number of odor-active compounds were detected in the gonads of cultured sea urchins (25) than in those from the Eisenia bed (14) and the barren (6). Dimethyl sulfide from the gonads of sea urchins from the barren was described as having a strong, putrid odor. Sea urchin-like aromas were attributed to 2-butanol, 2-ethylhexanol, benzaldehyde and ethylbenzene from the gonads of cultured sea urchin and those of the Eisenia bed. Kelp feeding decreased the putrid odor from dimethyl sulfide, and enhanced pleasant, sweet aromas.

Reproduction and population structure of the sea urchin Heliocidaris crassispina in its newly extended range: The Oga Peninsula in the Sea of Japan, northeastern Japan.

Ocean warming has facilitated the range expansion of commercially important sea urchin species to higher latitudes. Heliocidaris crassispina was recorded to extend northward to Toga Bay along the Oga Peninsula, Japan following an increase in seawater temperatures, and replacement of local sea urchin species Mesocentrotus nudus. In order to identify evidence of adaptation occurring in response to a range extension of H. crassispina to the newly extended environments, we randomly collected 106 H. crassispina in August 2014 in Toga Bay, determined the growth and age composition and examined gonad traits (size, color and development). To confirm the gonad development, 30 H. crassispina with > 30 mm diameter were collected in July, August and September 2017. We found slower growth in the extended range than the central range. More delayed gonad development of males than those of females and a large variety of developmental stages in the acini of testis indicated that the spawning of both sexes of the sea urchins were asynchronous. In terms of gonad color, L* (lightness) values increased with increasing GI, while b* (yellowness) values decreased with increasing age. The population consisted of seven year-classes from 2006 to 2012, suggesting persistent juvenile recruitment. Long-term water temperature data indicated that the range extension of H. crassispina was due to ocean warming, in particular during the summer spawning season.