Chyuan-Yuan Shiau

Free amino acids and peptides as related to antioxidant properties in protein hydrolysates of mackerel (Scomber austriasicus)

Mackerel (Scomber austriasicus) hydrolysates were prepared by an autolytic process and accelerated hydrolysis with a commercial enzyme, Protease N. Changes in the levels and compositions of free amino acids and small peptides during hydrolysis were investigated to find out their relationships with antioxidant activities. Increased levels of free amino acids, anserine, carnosine and other peptides of the hydrolysates obtained with protease were much higher than those by autolysis. Different antioxidant measurements including the inhibition of linoleic acid autoxidation, the scavenging effect on α,α-diphenyl-β-picrylhydrazyl free radical, and the reducing power showed that mackerel hydrolysates possessed noticeable antioxidant activities. A good correlation existed between the amount of peptides and antioxidant activity. Three peptide fractions were separated from the hydrolysate by size exclusion chromatography. Results revealed that the peptide with molecular weight of approximately 1400 Da possessed a stronger in vitro antioxidant activity than that of the 900 and 200 Da peptides.

Effects of rice bran on sensory and physico-chemical properties of emulsified pork meatballs

Four kinds of bran, which are milled from important rice cultivators in Taiwan, have high contents of dietary fiber, fat and protein. The use of rice bran in Kung-wan, an emulsified pork meatball, was investigated. It was found that protein and fat contents, and white index of meatballs decreased as the amount of bran increased. A texture profile analysis (TPA) also indicated the hardness, gumminess and chewiness of the Kung-wan decreased. The sensory scores of taste, texture and overall acceptability of meatballs with less than 10% added bran showed no significant difference from those for meatballs without bran. However, the added amount of 15% enriched meatballs resulted in inferior sensory scores. The brans particle size profoundly affected the sensory and physico-chemical properties of the meat products. Meatballs enriched with smaller bran particles possessed higher TPA indices and sensory scores than those added with larger ones. No significant differences in proximate composition, cooking yield, color and sensory quality were found among emulsified meatballs enriched with four different kinds of bran. Conclusively, the suitable amount of rice bran that should be added to emulsified pork meatballs was less than 10% and a smaller particle size would result in better quality.

Effects of Sizes and Conformations of Fish-Scale Collagen Peptides on Facial Skin Qualities and Transdermal Penetration Efficiency

Fish-scale collagen peptides (FSCPs) were prepared using a given combination of proteases to hydrolyze tilapia (Oreochromis sp.) scales. FSCPs were determined to stimulate fibroblast cells proliferation and procollagen synthesis in a time- and dose-dependent manner. The transdermal penetration capabilities of the fractionationed FSCPs were evaluated using the Franz-type diffusion cell model. The heavier FSCPs, 3500 and 4500 Da, showed higher cumulative penetration capability as opposed to the lighter FSCPs, 2000 and 1300 Da. In addition, the heavier seemed to preserve favorable coiled structures comparing to the lighter that presents mainly as linear under confocal scanning laser microscopy. FSCPs, particularly the heavier, were concluded to efficiently penetrate stratum corneum to epidermis and dermis, activate fibroblasts, and accelerate collagen synthesis. The heavier outweighs the lighter in transdermal penetration likely as a result of preserving the given desired structure feature.

Identification of puffer fish species by native isoelectric focusing technique

Abstract This study was designed to validate the feasibility of using native isoelectric focusing electrophoresis (IEF) of water-soluble sarcoplasmic proteins in identifying puffer fish species. Each of the six tested species of puffer fish Lagocephalus wheeleri , L. gloveri , L. lunaris , L. inermis , L. sceleratus , and Takifugu oblongus showed species-specific protein band profiles after the focused gel was treated with Coomassie blue or silver stain. The majority of water-soluble puffer fish muscle proteins fell in the region with isoelectric point (pI) values of 5.85–8.65. Characteristic species-specific protein bands were present in all the three regions of pI 3.50–5.20, pI 5.85-6.55, and pI 7.35–8.15. Therefore, the species of puffer fish can be differentiated from the comparison of the characteristic native IEF protein band profiles.

Identification of species and measurement of tetrodotoxin in dried dressed fillets of the puffer fish, Lagocephalus lunaris.

The toxicity and species of dried dressed fish fillets were investigated. Three of seven dried dressed fish fillets were found to be toxic, with their levels of toxicity ranging from 9 to 18 mouse units per g. The toxin preparation was further purified and identified as tetrodotoxin and anhydrotetrodotoxin by high-performance liquid chromatography and gas chromatography-mass spectroscopy. The species of these fillets could not be distinguished from Lagocephalus lunaris by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis or restriction site and sequence analysis of a polymerase chain reaction amplicon of the cytochrome b gene. These fish fillets were identified as L. lunaris on the basis of their protein patterns and gene characteristics. Furthermore, the toxic samples contained low levels of tetrodotoxin and its derivative.

The Relationship between Chemical Compositions and Body Weight of Cultured Cobia (Rachycentron canadum) of Different Growing Stages

The condition factor of 31 cage-cultured cobia (Rachycentreon canadum) with body weight ranging from 1.5 to 8730 grams was significantly and positively correlated with body weight for fish below 1.4 Kg (r=0.79), while no good correlation was found among fish above 1.4 Kg. The pH value of white muscle in cobia was between 5.5 and 6.3, which was similar to that of pelagic fishes. The levels of ammonia and urea were low in cobia. This is also similar to the most teleosts. No significant correlation was found between fish body weight and pH, ammonia and urea. There were large variations in fat and moisture contents of white muscle among different size of cobia, but not in protein and ash. The fat level in the ventral meat was two times higher than that of the dorsal meat of the same fish. Fat contents of both dorsal and ventral meats were significantly and positively correlated with body weight (r=0.8 and 0.78, respectively). In contrast, moisture content decreased gradually as fish body weight increased. The predominant free amino acids (FAAs) in cobia were taurine, glycine, alanine and glutamic acid. The contents of these FAAs and total FAAs tended to decrease as body weight increased. When comparing with glycine, alanine and glutamic acid, taurine was most significantly and negatively correlated with fish size. Anserine, a dipeptide, was detected in the meat of cultured cobia, and its content ranged from 14 to 80 mg/100g; however, it was not significantly correlated with fish body weight. Inosine monophosphate (IMP) was the most prominent component of ATP-related compounds. Both ATP-related compounds and IMP had no significant correlation with fish size.

Comparative chemical, taste, and functional components in different tissues of giant grouper (Epinephelus lanceolatus)

ABSTRACT The chemical composition, nutrition, and flavor components of various giant grouper tissues were determined. The muscle protein content was about 20%, and the muscle fat content was in the range of 3.9–6.4%, which is higher than that of most other groupers. The bone had the highest fat value (12.5–14.2%). The major nucleotide-related compound in the tissues was inosine monophosphate (IMP); whereas in the skin, adenosine monophosphate (AMP) was predominant. The predominant free amino acid (FAA) in the tissues was taurine (Tau), followed by arginine (Arg), lysine (Lys), and glycine (Gly). Tau content was higher in chin meat, and lower in bone. The total peptide content was in the range of 660–1,390 mg/100 g, which was much higher than that observed in other fish species. Muscle was rich in C16:0, C18:0, C18:1, and omega-3 highly unsaturated fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

Studies on the Development and Quality of Fish Chiffon Cake and its Storage Stability

ABSTRACT Thirty percent flour was substituted with dolphinfish (Coryphaena hippurus) and unicorn leatherjacket (Aluterus monoceros) paste in a cake recipe to evaluate the quality and shelf life of fish chiffon cakes stored at 4℃ and 25℃. Proximate composition, free amino acid (FAA), aerobic plate count (APC), total volatile basic nitrogen (T-VBN), and texture profile and sensory evaluation of fish chiffon cakes were conducted. Fish paste addition increases proteins. Cakes made with dolphinfish paste had the highest FAA content, followed by the cake made with unicorn leatherjacket. Histidine is the predominant FAA in dolphinfish chiffon cake, and it is significantly higher than the other two cakes. T-VBN values and APC increased with the addition of fish paste and was lower than the upper limit of acceptable fish products during storage period. The hardness of the two fish cakes was slightly lower than the control after 1 and 2 days storage at 25℃ or 3 and 5 days storage at 4℃ and increased during storage. Sensory evaluation showed no significant differences among the ordinary cake and two fish chiffon cakes for odor, texture, flavor, and overall acceptability. Therefore, incorporation of white fish meat is feasible for chiffon cake.

Chemical compositions of commercial cobia feeds in Taiwan and the effects of the practical finisher diets on the fish meat quality.

The chemical compositions of fifteen commercial feeds of cobia (Rachycentron canadum) from six feed manufacturers were analyzed. The effect of two diets designated as A (low protein: 46.3%, low fat: 16.8%) and B (high protein: 48.6%, high fat: 19.9%) on the chemical compositions and meat quality of the fish raised in a practical commercial production scale were also investigated. The commercial cobia feeds had different sizes and shapes according to the culturing stages of the fish. The moisture contents of the feeds ranged from 3.56% to 9.91%, ash 9.40% to 13.32%, protein 41.15% to 50.86%, fat 10.85% to 21.34%, and carbohydrate 15.24% to 24.32%. The major fatty acids were C16:0 and C18:1n-9. The levels of n-3 polyunsaturated fatty acids including EPA and DHA were also high (ranged from 6.05% to 14.22% and from 4.42% to 14.81%, respectively); suggesting that the feeds contained good levels of fish oil. When two finisher diets were fed to two groups of cobia for two months to grow the fish to their marketable size (5~6 kg/fish), the protein, fat, ATP-related compounds, free amino acids and anserine in both dorsal (D) and ventral (V) meats of the fish tended to increase with a raise of 2.37% protein plus a raise of 3.14% fat in the diets. The fatty acid profiles of D and V meats from A and B groups were relatively similar to those of the two diets. The predominant fatty acids were C16:0, C18:1n-9, C16:1n-7, EPA and DHA. However, n-6/n-3 ratios in both D and V meats changed from 0.51 or 0.50 to 0.66 or 0.69 with the raise of protein and fat levels in the diets.