Abstract
Fermented squid, Loligo kobiensis, is widely used and occupies an important position in foods of this country. But no study on its taste compounds has been reported. This study was attempted to establish the basic data for evaluating taste compounds of fermented squid. The changes of such compounds during fermentation as free amino acids, nucleotides and their related compounds, TMAO, TMA and betaine were analysed. The sample was prepared with 20% salt content and fermented at a controlled temperature of $15{\pm}3^{\circ}C$. ADP, AMP and inosine tended to degrade rapidly while hypoxanthine increased more than four times as compared with raw sample at 91 day fermentation. In the free amino acid composition of fresh squid, abundant amino acids were proline, taurine, alanine, arginine, serine, glutamic acid, lysine, glycine, leucine and valine in order. Such amino acids like phenylalanine, methionine, tyrosine, isoleucine, and histidine were poor. In squid extract, proline and taurine were dominant holding 40.2% and 32.0% of total free amino acids respectively. The total free amino acid nitrogen in fresh squid was 33.6% of its extract nitrogen. The changes of free amino acid composition in the extract of squid during fermentation was not observed. In the extract of fermented product, abundant amino acids were proline, leucine, lysine, serine, arginine, alanine, valine, isoleucine, phenylalanine, methionine and glycine in order. Glutamic acid and histidine were poor and taurine and tyrosine were trace in content. The increase of total free amino acids during 63 day fermentation reached approximately wore than 1.8 times as compared with that of raw sample and than decreased slowly. The amount of betaine increased more than 1.2 times as compared with that of raw sample during 91 day fermentation. TMA increased while TMAO decreased during fermentation. The amount of TMAO nitrogen in 91 days fermented squid was 402.4mg% on moisture and salt free base. Betaine and TMAO known as sweet compounds were abundant in fermented squid. It is supposed that these compounds could also play a role as important taste compounds of fermented squid. It is concluded that the major taste compounds of fermented squid were amino acids like proline, leucine, serine, lysine, arginine, alanine and betaine. Other compounds such as valine, isoleucine and TMAO and hypoxanthine could also not be excluded as taste supporters in fermented squid.
젓갈은 우리나라에서 옛부터 즐겨 먹어온 수산발효식품(水産醱酵食品)으로서 우리나라 고유(固有)의 젓갈이 많지만, 이에 대한 상세(詳細)한 연구보고(硏究報告)는 의외(意外)로 적다. 본(本) 실험(實驗)에서는 꼴뚜기젓의 정미성분(呈味成分)을 밝히기 위하여 선도(鮮度) 좋은 꼴뚜기를 원료(原料)로써 젓갈 숙성(熟成) 중의 핵산(核酸) 관련물질(關聯物質), 유리아미노산(酸), TMAO, TMA 및 betaine의 변화(變化)를 실험(實驗)하였다. 꼴뚜기젓 숙성(熟成) 중 ADP, AMP 및 inosine은 현저히 감소(減少)하는 반면(反面) hypoxanthine은 급증(急增)하여 숙성(熟成) 91일(日) 후(後)에는 건물량기준(乾物量基準) $9.3{\mu}mole/g$로서 원료(原料)에 비(比)하여 3.9배(倍) 증가(增加)하였다. 원료(原料)의 유리아미노산(酸) 조성(組成)을 보면, 함량(含量)이 많은 것은 Pro, Tau이고 다음이 Ala, Arg, Ser, Glu, Lys, Gly, Leu 및 Val이며, 함량(含量)이 적은 것은 Phe, Met. Tyr, Ileu, His의 순(順)이었다. 함량(含量)이 특(特)히 많은 아미노산(酸)의 전(全) 유리아미노산(酸)에 대한 비율(比率)을 보면, Pro 40.2%, Tau 32.0%로서 이들 2종(種)의 아미노산(酸)이 72.2%를 차지하였고, 엑스분질소(分窒素) 중 전(全)유리아미노산질소(酸窒素)가 차지하는 비율(比率)도 64.9%로서 높은 편이었다. 꼴뚜기젓 숙성(熟成) 중 유리아미노산(酸)의 양적(量的) 변화(變化)는 있으나 조성(組成)에는 변화(變化)가 없었다. 꼴뚜기젓의 유리아미노산(酸) 중 함량(含量)이 많은 것은 Pro, Leu, Lys, Ser, Arg, Ala, Val이고, Ileu, Phe, Met등도 상당히 많았으며, Glu, His등은 함량(含量)이 적었고 Tau과 Tyr은 흔적량에 불과(不過)하였다. betaine은 젓의 숙성(熟成)과 더불어 증가(增加)하기 시작하여 숙성(熟成) 91일(日)까지 증가(增加)하다가 그 후(後) 약간 감소(減少)하였다. TMAO는 숙성(熟成) 중 감소(減少)하는 반면(反面) TMA는 증가(增加)하였다. 63일간(日間) 숙성(熟成)시킨 꼴뚜기젓에는 건물량기준(乾物量基準)으로 TMAO질소(窒素)가 432.3mg%로서 상당히 많은 함량(含量)이었다. 꼴뚜기젓의 정미성분(呈味成分)으로서는 Pro, Leu, Ser, Lys, Arg, Ala, Val, Ileu, Phe, Met 및 Gly등과 같은 유리아미노산(酸)과 단맛을 가진 betaine, TMAO 그리고 핵산(核酸) 관련물질(關聯物質)로서는 hypoxanthine등이 중요(重要)한 정미성분(呈味成分)이라는 결론(結論)을 얻었다.