Abstract
Taste is an important trait of sea urchin quality. Highly contained alanine in gonads of the sea urchin Mesocentrotus nudus results in desirable taste. Past studies hypothesized that high levels of glutamic acid and/or alanine in feed increase the alanine content in the gonads. To identify the amino acids in feed that increase the alanine content in the gonads, the free amino acid content in the gonads of M. nudus of the following five treatment groups were compared at the start and end of the feeding experiment during May–July: sea urchins fed one of four experimental diets, in which glutamic acid (Glu S), alanine (Ala S), aspartic acid (Asp S) or glycine (Gly S) was supplemented, or a control diet without supplementation (Control). The alanine content in the gonads of Ala S increased significantly from the start. The content in the gonads of Glu S increased without significance. There was no significant difference in the alanine content in the gonads between Ala S and Glu S. The content in the gonads of Ala S was significantly higher than that of Asp S, Gly S and Control. There were no significant differences in the aspartic acid and glutamic acid contents in the gonads among treatments at the end of the experiment. The higher alanine content in the gonads of Ala S than that in Glu S indicates that direct accumulation of alanine from the feed is effective. This study first identified the amino acids in feed that are closely associated with improvement in the taste of sea urchin gonad.
Highlights
From 1961 to 2016, the average annual increase in global fish and shellfish consumption (3.2%) outcompeted population growth (1.6%) and exceeded the consumption of meat from all terrestrial animals combined (2.8%) (FAO, 2018)
This study aimed to identify the amino acids in feed that increase the alanine content in gonads and verify the hypothesis that high levels of glutamic acid and alanine in feed increase the alanine content in the gonads of sea urchins
Feeding diets supplemented with glutamic acid or alanine increased the sweet-tasting alanine content in the gonads of M. nudus, which is attributed to their desirable taste
Summary
From 1961 to 2016, the average annual increase in global fish and shellfish consumption (3.2%) outcompeted population growth (1.6%) and exceeded the consumption of meat from all terrestrial animals combined (2.8%) (FAO, 2018). The annual fish and shellfish consumption increased from 9.0 kg in 1961 to 20.2 kg in 2015 (FAO, 2018). In northern Japan, studies focusing on the short-term culture of Mesocentrotus nudus adults, which are densely distributed in crustose coralline red algal communities (barrens) without erect macrophytes (reviewed by Agatsuma, 2013), have been advancing (e.g., Unuma et al, 2015; Inomata et al, 2016). Sea urchins on barrens have small gonads; exhibit undesirable gonad color, texture and taste; and are of no commercial value (e.g., Agatsuma et al, 2005; Takagi et al, 2017). There are no quantitatively ranked classes of sea urchin gonad in Japan. Takagi (2020) concluded that M. nudus gonads with 56.0–60.7 of L∗ value, 0.11–0.14 N of hardness, 235–595 mg/100 g of alanine content and 215– 334 mg/100 g of arginine content can have commercial value by sensory evaluation and quantitative measurements and analyses of gonad quality of M. nudus
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