Research On The Taste Characteristic Components And Flavor Peptides Of Bred Pufferfish

T.obscurus and T.rubripes are the most commonly consumed pufferfish in China.Because the legal edible policy was opened in Sep,2016,T.obscurus and T.rubripes will have a great market in China.Takifugu is famous for its delicious taste,such as the non-volatile taste-active compounds,free amino acids,5?-nucleotides,organic acids,organic bases,inorganic ions and flavor peptides.These components were reported as the contributors to unique taste of pufferfish.However,up to now,researches on non-volatile taste compounds,especially umami components in both pufferfish were not comprehensive and systematic enough.Moreover,the connection between consumer preference and umami intensity in pufferfish meat is unknown,and the reported key taste compounds in T.obscurus were contradictory.Recently,several flavor peptides from T.obscurus have been identified by using a series of sensory-guided seperation and purification technology processes.However,their sensory impact and contribution on overall taste profile in T.obscurus is still unclear,and their taste attributes and taste-related characteristics are also still in the blank.So this study explored the key taste-active compounds,taste profile and taste contribution of flavor peptides according to quantitation analysis and sensory evaluation,which would help to reveal the secret of delicious taste of T.obscurus and provide the basis for development of deeper flavor analysis of pufferfish.(1)The boiled and steamed T.obscurus and T.rubripes(the most common ways to cook pufferfish in China)were targeted,and their taste compounds including proximate compositions,inorganic ions,free amino acids,5?-nucleotides and organic acids were analyzed.Non-volatile taste active components and umami synergistic effects were measured and evaluated by taste activity values(TAV)and equivalent umami concentrations(EUC),respectively.Additionally,the relationship between EUC and sensory evaluation were also investigated.The amount of the main taste components in T.obscurus was higher than T.rubripes,and similar results that steaming had a higher amount of taste compounds than boiling were obtained during cooking.Inosine-5?-monophosphate(IMP)was the dominant taste compound(148-370mg/100 g)and its TAV in all samples were far greater than 1.Na~+and K~+significantly contributed to the taste of both fish.EUC values in T.obscurus were greater than T.rubripes,and the umami intensities of 100 g were equivalent to 0.50-3.06 g monosodium glutamate(MSG).Subsequently,a positive relationship was shown among the EUC values,sensory score of umami and acceptability.All results suggested that T.obscurus has higher umami taste and was more acceptable.(2)T.obscurus,which was proven to have the higher umami intensity and more acceptable,was targeted.28 putative taste compounds in cooked muscle of T.obscurus were quantitatively analyzed,and the pivotal components were identified by taste reconstitution,omission and addition tests.Moreover,the role of flavor peptides in overall taste profile of T.obscurus was also evaluated.Sensory evaluation revealed that glutamic acid,serine,proline,arginine,lysine,IMP,succinic acid,sodium,potassium,phosphates and chlorides were the core taste-active contributors to T.obscurus.However,simplified taste recombinent(STR)composed of the above 12 components cannot perfectly reproduce the overall taste of pufferfish compared with the natural extract.Based on this,the identified flavor peptides by our group in T.obscurus were added and two peptides,Pro-Val-Ala-Arg-Met-Cys-Arg(PR-7)and Tyr-Gly-Gly-Thr-Pro-Pro-Phe-Val(YV-8),were confirmed to have significant contribution of typical umami and kokumi taste.The overall taste profile of T.obscurus can be greatly reconstituted by the above key taste components and flavor peptides.(3)The taste-related characteristics of two flavor peptides(PR-7 and YV-8),which contribute significantly to typical taste of T.obscurus,were revealed by using the combination of artificial and intelligent sensory as well as instruments and quantum chemical calculations.The results showed that PR-7 and YV-8 were umami peptides while possessing kokumi effect.Peptides both presented prominent umami at near neutral pH,and they also induced pronounced umami-enhancing effects andsignificantly decreased the threshold of MSG.Simultaneously,the kokumi effect of PR-7 was close to glutathione.Additionally,two peptides have great pH and thermal stability,especially YV-8.All results suggested that PR-7 and YV-8 have potential to be used in the complex food system and provided desirable taste.In conclusion,this article found T.obscurus had more prominent umami and overall taste than T.rubripes,and T.obscurus was favored by consumers.Fl PR-7 and YV-8can contributed to the characteristic taste of T.obscurus.T.obscurus-like taste was reproduced ideally by combining key taste components with flavor peptides.In addition,PR-7 and YV-8,which have great potential to be used in flavoring system,have ideal umami and kokumi taste and stability.This study provided a theoretical basis for the flavor research of pufferfish and promoted the application of flavor peptides in food system.