The selective adsorption mechanism of V-type starches for key off-odors of sea cucumber intestinal peptides.

The off-odors of sea cucumber intestinal peptide (SCIP) severely limit its application. In this study, the V-type starches were derived from high amylose maize starch to adsorb odors of SCIP and the adsorption mechanism was explored. The inclusion complexes formed by V-type starches and volatile compounds of SCIP were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The electronic nose results revealed a decreasing trend in response values of SCIP, with significant differences before and after deodorization (p < 0.05). Furthermore, 82 volatiles were identified from SCIP, and six were determined as key volatiles using gas chromatography-mass spectrometry. The V6- and V7-type starches with smaller cavity sizes selectively adsorb butyric acid, isobutyric acid and nonaldehyde, and V8-type starches with a larger cavity size selectively adsorb trimethylamine. This study proved that using V-type starches for deodorization could effectively improve SCIP flavor.

Antioxidant characteristics of hydrolysate from low-value sea cucumber: In vitro and in vivo activities of Caenorhabditis elegans.

The antioxidant activity in vitro and in vivo of Actinopyga miliaris hydrolysate (AMH) was investigated. The proportion of oligopeptides with 150-1000 Da in AMH was 65.48%. The IC50 values of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), hydroxyl radical scavenging ability, and ferric ion reducing power of AMH were 0.37, 3.43, and 24.15 mg/mL, respectively. Compared with the control group, the body length of Caenorhabditis elegans fed with 8 mg/mL AMH extended from 632.08 µm to 1009.57 µm, and the swallowing frequency and head-swing frequency increased significantly. After being fed with AMH, the lifespan of C. elegans can be prolonged even under stress conditions, primarily due to superoxide dismutase activity, catalase activity, reduced glutathione content, and total antioxidant capacity in C. elegans increased, whereas reactive oxygen species level was reduced. The results showed that AMH had in vitro and in vivo antioxidant activity, which can alleviate oxidative damage and prolong life of C. elegans.

Preparation and characterization of soy protein isolate films by pretreatment with cysteine.

The effect of cysteine concentration on the viscosity of soy protein isolate (SPI)-based film-forming solution (FFS) and physicochemical properties of SPI films was investigated. The apparent viscosity of FFS decreased after adding 1 mmol/L cysteine but did not change after adding 2-8 mmol/L cysteine. After treatment with 1 mmol/L cysteine, the film solubility decreased from 70.40% to 57.60%, but the other physical properties did not change. The water vapor permeability and contact angle of SPI films increased as cysteine concentration increased from 4 mmol/L to 8 mmol/L, whereas the film elongation at break decreased. Based on scanning electron microscopy and X-ray diffraction results, cysteine crystallization could be aggregated on the surface of SPI films treated with 4 or 8 mmol/L cysteine. In conclusion, pretreatment with approximately 2 mmol/L cysteine could reduce the viscosity of SPI-based FFS, but did not change the physicochemical properties of SPI films.

Lacticaseibacillus paracasei fermentation broth identified peptide, Y2Fr, and its antibacterial activity on Vibrio parahaemolyticus.

Although Vibrio parahaemolyticus infections cause severe diseases of large yellow croaker (Larimichthys crocea), using antibiotics and other chemical agents to treat these infections could result in antimicrobial resistance, environmental pollution, and other associated problems. This study identified seven peptides from Lacticaseibacillus paracasei fermentation broth using ultra-high-performance liquid chromatography-mass spectrometry and screened antimicrobial peptide Y2Fr (VEIKNGLLKLNGKPLLIR) through its net charge, hydrophobicity and predicted secondary structure. Antibacterial activity analysis revealed that Y2Fr had a minimum inhibitory concentration (MIC) of 125 µg/mL, minimum bactericidal concentration (MBC) of 250 µg/mL against V. parahaemolyticus and a time-kill of 3 h. In a bacterial membrane environment, the secondary structure of peptide Y2Fr changed from a random coil to a ß-sheet to enhance its membrane permeability and binding to bacteria DNA to exert its antibacterial effect. Further molecular docking analysis revealed that peptide Y2Fr could bind to the membrane protein KKI11460.1 and DNA polymerase A0A0L8TVA4 of V. parahaemolyticus through hydrogen bonds. Meanwhile, treatment of Y2Fr with mammalian red blood cells and plasma revealed that it was noncytotoxic, nonhemolytic, and stable under physiological conditions. Thus, peptide Y2Fr has great potential use in treating and preventing infections caused by V. parahaemolyticus or similar bacteria in aquatic animals.

Encapsulation and release kinetics of ethylene into "pre-formed" V-type starch and granular cold-water-soluble starch.

Ethylene gas was loaded into "pre-formed" V-type starch (V6, V7 and V8) by molecular encapsulation, and granular cold-water-soluble starch (GCWSS) was chosen as a control. The formation, structural characteristics and morphological properties of inclusion complexes (ICs) were investigated using X-ray diffraction, scanning electron microscopy, and 13C solid-state nuclear magnetic resonance spectroscopy. The V6a-type starch represented the most effective structure in encapsulating ethylene gas among different "pre-formed" V-type starches. The Avrami equation was used to describe the release kinetic properties of ethylene gas from ICs under various conditions of temperatures and relative humidities (RHs). The release of ethylene from ICs conformed to diffusion-limited release mechanisms (temperature) and first-order kinetics (RH). This could be caused by the differences in starch structure and association mechanisms between ethylene and starch single helices. Accelerated ripening experiments showed that ethylene-starch ICs could ripen bananas within 5 days, suggesting that this molecular encapsulation technology can provide precise control and targeted application of ethylene gas in the ripening of vegetables and fruits.

Characteristics of pressurized hot water extract from abalone muscle and the antioxidant ability during simulated digestion in vitro.

The physicochemical properties of pressurized hot-water extract (PHE) from abalone muscle and the antioxidant activities of its digestive products were investigated in this study. The PHE contained protein of 49.58% and carbohydrate of 41.95%. After ethanol graded precipitation, most of carbohydrate and protein in PHE were successively remained in 40% ethanol precipitate (EP40) and 80% ethanol precipitate (EP80), respectively. High proportions of Glu and Gly were found in the PHE, EP40 and EP80, but the proportion of Ala in ethanol soluble extract (ESE) reached up to 46.00%. Both PHE and EP40 were rich in glucose, while galactose and glucose were main monosaccharides in the EP80 and ESE. Based on the results of SDS-PAGE and HPLC, high molecular weight components from PHE were precipitated in the EP40, but oligopeptides and free amino acids were fractionated in EP80 and ESE. Among the PHE and the digestive products, the highest antioxidant ability was found to be EP80 hydrolysate, the IC50 values of which for scavenging activity on hydroxyl radical, DMPD radical and ABTS radical were 1.05 mg/mL, 1.40 mg/mL and 0.56 mg/mL, respectively. It is concluded that carbohydrate of abalone muscle was dissolved more easily into hot water than protein, and protein hydrolysate of PHE might play an important role in antioxidant activity of gastrointestinal digestion.

Preparation and bioavailability of calcium-chelating peptide complex from tilapia skin hydrolysates.

BACKGROUND: With the continuous improvement in material life, the generation of fish by-products and the market demand for calcium supplements have been increasing in China. Therefore a calcium-chelating peptide complex (CPC) from tilapia skins was prepared and its effect on calcium (Ca)-deficient mice was investigated. RESULTS: The molecular weight distribution of CPC mainly ranged from 2000 to 180 Da, and its contents of complete amino acids and free amino acids were 85.30 and 8.67% (w/w) respectively. Scanning electron microscopy images and Fourier transform infrared data revealed that Ca crystals were bound with gelatin hydrolysates via interaction between Ca ions and NH/CN groups. When Ca-deficient mice were fed CPC and CaCO3 respectively for 4 weeks, no significant differences in serum biochemistry or bone mineral density were found. However, the length, weight, Ca content and hydroxyproline content of the femur, Ca absorption and body weight gain of mice fed CPC were significantly higher than those of mice fed CaCO3 . CONCLUSION: It is concluded that the prepared CPC could promote bone formation via better bioavailability of Ca and an increase in bone collagen. © 2017 Society of Chemical Industry.

Purification and characterization of a gelatinolytic metalloproteinase from the skeletal muscle of red sea bream (Pagrus major).

A gelatinolytic metalloproteinase (gMP) from red sea bream ( Pagrus major ) skeletal muscle was highly purified by ammonium sulfate fractionation and column chromatographies including (diethylamino)ethyl (DEAE)-Sephacel, phenyl-Sepharose, and gelatin-Sepharose. Purified gMP revealed two bands with molecular masses of 52 and 55 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions. The 55 kDa band is quite possibly a glycosylated form of the 52 kDa band. The proteinase revealed optimal activity at 40 degrees C and pH 8.0. Metalloproteinase inhibitors including ethylenediaminetetraacetic acid (EDTA), ethylene glycol bis(2-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), and 1,10-phenanthroline specifically suppressed its activity. gMP was also significantly inhibited by cysteine and dithiothreitol. Divalent metal ion Ca(2+) is essential for its gelatinolytic activity. Thus, the proteinase is regarded as a matrix metalloproteinase-like proteinase. Furthermore, gMP hydrolyzed gelatin and type-I collagen effectively even at 4 degrees C, suggesting the possibility of its involvement in the texture tenderization of fish muscle during the post-mortem stage.