Effect of Maillard reaction with xylose, yeast extract and methionine on volatile components and potent odorants of tuna viscera hydrolysate

The aim of this research was to enhance the flavor of visceral extracts from skipjack tuna. Flavor precursors and the optimum condition for the Maillard reaction were determined. The flavor extract was prepared from the tuna viscera using Endo/Exo Protease controlled in 3 factors; temperature, enzyme amounts and incubation time. The optimal condition for producing tuna viscera protein hydrolysate (TVPH) was 60°C, 0.5% enzyme (w/w) and 4-hour incubation time. TVPH were further processed to tuna viscera flavor enhancer (TVFE) with Maillard reaction. The Maillard reactions of TVFE were conducted with or without supplements such as xylose, yeast extract and methionine. The Maillard volatile components were analyzed with gas chromatography-mass spectrometry. Sixteen volatiles such as 2-methylpropanal, methylpyrazine, 2,5-dimethylpyrazine, dimethyl disulfide and 2-acetylthaizone were newly formed via Maillard reaction and the similarity of volatile contents from TVPH and TVFE were virtualized using Pearson’s correlation integrated with heat-map and principal component analysis. To virtualize aromagram of TVPH and TVFE, odor activity value and odor impact spectrum (OIS) techniques were applied. According to OIS results, 3-methylbutanal, 2-methylbutanal, 1-octen-3-ol 2,5-dimethylpyrazine, methional and dimethyl trisulfide were the potent odorants contributed to the meaty, creamy, and toasted aroma in TVFE

Thermal denaturation profiles of catfish and tilapia myofibrils as affected by pH for heating

Thermal denaturation profiles of catfish myosin when heated as myofibrils (Mf) were compared with those of tilapia ones. Ca2+-ATPase inactivation rate of catfish myofibrils was the same as that of tilapia myofibrils. The conclusion was the same with isolated myosin. Catfish Mf was clearly distinguished form tilapia Mf in subfragment-1 (S-1) and rod denaturation. A quick denaturation of rod relative to S-1 was characteristic for catfish Mf while a slower denaturation of rod relative to S-1 was the pattern of tilapia Mf. These patterns were greatly affected by the pH for heating. With increasing the pH for heating, rod denaturation was accelerated and oppositely suppressed by lowering the pH for both Mf. Tilapia Mf showed a similar S-1 and rod denaturation pattern to catfish Mf by increasing 1 pH unit. For example, a pattern with catfish Mf at pH 7.5 was similar to one with tilapia Mf at pH 8.5. Less rigid filament structure of catfish Mf than tilapia Mf was demonstrated by studying chymotryptic digestion at various pH. Accordingly, difference S-1/rod denaturation pattern for two fish species was explained by the different rigidity of myosin filaments

Characteristics and Properties of Acid- and Pepsin-Solubilized Collagens from the Tail Tendon of Skipjack Tuna (<i>Katsuwonus pelamis</i>)

The tail tendons of skipjack tuna (Katsuwonus pelamis), a by-product from the meat-separation process in canned-tuna production, was used as an alternative source of collagen extraction. The acid-solubilized collagens using vinegar (VTC) and acetic-acid (ATC) extraction and pepsin-solubilized collagen (APTC) were extracted from tuna-tail tendon. The physiochemical properties and characteristics of those collagens were investigated. The obtained yield of VTC, ATC, and APTC were 7.88 ± 0.41, 8.67 ± 0.35, and 12.04 ± 0.07%, respectively. The determination of protein-collagen solubility, the effect of pH and NaCl on collagen solubility, Fourier-transform infrared spectroscopy (FTIR) spectrum, and microstructure of the collagen-fibril surface using a scanning electron microscope (SEM) were done. The protein solubility of VTC, ATC, and APTC were 0.44 ± 0.03, 0.52 ± 0.07, and 0.67 ± 0.12 mg protein/mg collagen. The solubility of collagen decreased with increasing of NaCl content. These three collagens were good solubility at low pH with the highest solubility at pH 5. The FTIR spectrum showed absorbance of Amide A, Amide B, Amide I, Amide II, and Amide III groups as 3286–3293 cm−1, 2853–2922 cm−1, 1634–1646 cm−1, 1543–1544 cm−1, and 1236–1237 cm−1, respectively. The SEM analysis indicated a microstructure of collagen surface as folding of fibril with small pore