Seafood Flavor Research Articles

Distribution of bromophenols in species of marine polychaetes and bryozoans from eastern Australia and the role of such animals in the flavor of edible ocean fish and prawns (shrimp).

Sixteen species (44 samples) of marine polychaetes and 10 species (14 samples) of bryozoans from eastern Australia were analyzed by GC/MS for the key seafood flavor components 2- and 4-bromophenol, 2, 4- and 2,6-dibromophenol, and 2,4,6-tribromophenol. All five bromophenols were found in 91% of polychaetes and 64% of bryozoans. The remaining samples all contained at least three bromophenols. 2,4, 6-Tribromophenol was found in all polychaetes and bryozoans and, with few exceptions, was present in the highest concentrations. The total bromophenol content determined on a wet-weight basis varied widely between species: for polychaetes, from 58 ng/g for Australonuphis teres to 8.3 million ng/g for Barantolla lepte, and for bryozoans, from 36 ng/g for Cladostephus spongiosus to 1668 ng/g for Amathia wilsoni. Species of polychaetes with the highest concentrations of bromophenols were all collected from muddy environments. The possible effects that dietary polychaetes and bryozoans have on the ocean-, brine-, or iodine-like flavors of certain seafoods are discussed.

Production of seafood flavor from red hake (Urophycis chuss) by enzymatic hydrolysis.

Protein hydrolysates were prepared as a natural flavor stock from the red hake (Urophycis chuss) headed-gutted (H&G) mince and frame mince using commercial enzymes, Flavourzyme and Savorase, at the natural pH of fish (6.8) and the water/fish ratio of 2:5. The addition of 1.5% NaCl and 0.4% STPP improved the flavor quality of the hydrolysate by masking bitterness and off-flavor. A 6 h hydrolysis of H&G mince with Flavourzyme yielded a hydrolysate of the highest acceptability. Hydrolysis increased the concentration of most free amino acids except Arg and His. Leu, Lys, and Arg were predominant free amino acids in the hydrolysates, whereas Leu and Arg were major ones in the cooking juice. The concentration of Glu responsible for umami taste was increased by 6-9 times upon hydrolysis. Hydrolysates contained higher percentages of free amino acids giving both umami and sweet tastes than did cooking juice.

Distribution of bromophenols in species of marine algae from eastern Australia.

Forty-nine species (87 samples) of marine macroalgae from eastern Australia were analyzed by GC/MS for the key seafood flavor components 2- and 4-bromophenol, 2,4- and 2,6-dibromophenol, and 2,4, 6-tribromophenol. All five bromophenols were found in 62% of samples, four in 32% of samples, and three in the remaining 6% of samples. 2, 4,6-Tribromophenol was found in all samples and, with few exceptions, was present in the highest concentrations. The total bromophenol content determined on a wet-weight basis varied widely across species from 0.9 ng/g in the green alga Codium fragile to 2590 ng/g in the red alga Pterocladiella capillacea. Species with the highest concentrations of bromophenols were all collected from sites exposed at low tide. The study demonstrates the wide occurrence of bromophenols in marine algae and provides a possible source of such compounds in fish that feed predominantly on ocean plants. The possible effect that dietary marine algae has on the flavor of omnivorous ocean fish is discussed.

Utilization of Fish Protein and Oil from the Anchovy Engraulis japonicus

Anchovy Engraulis japonicus, a small unutilized fish, is a rich resource or fish protein and oil. The utilization of anchovy protein and oil was studied. A non-bitter fish protein hydrolysate was prepared by exhaustive hydrolysis with proteolytic enzyme. The end product gained by spray dry was a protein-rich white powder with the appropriate ratio of essential amino acids. The results of a biological evaluation on rats indicated that the hydrolysate had a high nutritive value. The product may be used as a protein supplement. Another non-bitter fish protein hydrolysate was prepared by partial hydrolysis with proteolytic enzyme. The spray-dried product with a seafood flavor may be used as seafood flavoring. Polyunsaturated fatty acid concentrates were prepared from anchovy oil by using the urea addition and molecular distillation methods.

Preliminary Identification of Lipoxygenase in Algae (Enteromorpha intestinalis) for Aroma Formation

Lipoxygenase (LOX) activity was identified in a green sea algae (Enteromorpha intestinalis). The oxygen consumption rate of sea algae-catalyzed oxidation of linoleic acid was 1.18 μmol/min·mg of protein. The catalytic rate was 911 times that of shrimp hemolymph LOX and 59 times that of trout gill LOX. Based on retention time in normal phase HPLC analysis and UV absorption spectrosocopy, hydroperoxidation of linoleic acid by sea algae LOX was at the C9 and C13 positions with a ratio of 1.97:1. The products of sea algae LOX treated with arachidonic acid were 12- (or 8-) and 15-HETE (hydroxyeicosatetraenoic acid) on the basis of retention time in reverse phase HPLC analysis. Thus, 12- (or 8-) and 15-LOX were the major LOX isozymes in the sea algae. The optimal pH of sea algae LOX was 7.8 and the optimal temperature was around 35 °C. Different treatments of sea algae generated volatile compounds contributing to flavor notes of clam, oyster, fresh apple, cucumber, mango, and algae identified with the GC-sniffing method. This is the first observation of LOX in marine algae with respect to its possible roles in seafood flavor formation. Keywords: Lipoxygenase; sea algae; seaweed; Enteromorpha intestinalis; flavor

Evaluation of Soybean Proteins as Replacements for Menhaden Fish Meal in Practical Diets for the Red Drum Sciaenops ocellatus

AbstractA series of growth trials was conducted to evaluate the use of soy protein as a replacement for fish protein in isonitrogenous practical diets for juvenile red drum Sciacnops ocellatus. Feeds were offered at or in excess of satiation to juvenile red drum maintained at 26–28 C and a salinity of 25–35 ppt. In the first growth trial, red drum were offered one of four diets containing graded levels of menhaden fish meal, replacing solvent‐extracted soybean meal and soy‐protein isolates. Differences in weight gain, survival and feed efficiency ratios of the fish corresponded to increases in fish meal content of the diets. Due to poor performance of the fish maintained on the low (15%) fish meal diet, a methionine supplement was introduced into this diet at the midpoint of the growth trial. A positive increase in growth indicated a dietary deficiency of methionine and/or total sulfur amino acids in the unsupplemented diet. A positive response to dietary fish meal also occurred in the second growth trial despite the supplementation of L‐methionine in the test diets. In low fish meal diets the utilization of solvent extracted soybean meal or a soy‐protein isolate resulted in similar growth responses. Hence, the presence of an antinutrient did not likely cause reduced growth rates. In the third feeding trial, weight gain also increased with increasing fish meal content of the diet despite the equalization of digestible protein and selected amino acids. There were no significant differences in whole‐body compositions which indicated similar biological value of the diets (protein digestibility, amino acid balance and energy availability). The singular deletion of fish‐solubles, glycine, lysine and methionine from the diet containing the lowest level of fish meal (10 g/100 g diet) did not result in significant changes in weight gain. This indicated that these components did not add to the nutritive value and/or palatability of this formulation. The final experiment was designed to evaluate the response of red drum to a control diet (high fish meal) as compared to a low fish meal diet with and without potential attractants/palatability enhancers. Weight gain and feed efficiency ratios of fish offered the low fish meal diet supplemented with seafood flavor or fish flavor #2 were not significantly different from the control (high fish meal diet). Based on the results of this study, with suitable formulation restrictions, soy protein is acceptable for inclusion in practical diet formulations for red drum. However, soy protein itself does not appear replete in sulfur‐containing amino acids and does not have acceptable palatability properties. Consequently, feeds containing reduced levels of marine proteins could require suitable attractants and/or amino acid supplements.