Influence of emulsion composition and spray-drying conditions on microencapsulation of tilapia oil.

The influence of processing conditions on the microencapsulation of tilapia oil by spray drying was studied. Trehalose, gelatin, sucrose and xanthan were used as emulsion composition. The experimental parameters of spray drying such as inlet air temperature, solid content, drying air flow rate and atomizing pressure were optimized using a central composite design. Encapsulation efficiency and lipid oxidation were determined. Bulk density, powder morphology and particle size were also analyzed. Trehalose improved the glass transition temperature of wall material significantly and prevented the oxidation of the fish oil. Encapsulation efficiency reached a maximum of 90 % under optimum conditions with an inlet air temperature of 121 °C, a drying air flow rate of 0.65 m(3)/min and a spray pressure of 100 kPa.

Proteomics study of mitochondrial proteins in tilapia red meat and their effect on color change during storage.

The underlying mechanism of the role of mitochondria in color changing of tilapia fillet during 0-4 d storage is not completely clear. A total of 209 differentially significant expressed proteins (DSEPs) were identified by using label-free mitochondrial proteomics, with 56 proteins up-regulated in T2 and 61 proteins (up-regulated) in T3. Protein-Protein interaction reveled proteins which participate in TCA cycles (Citrate synthase (cs)), Oxidoreductase (Malate dehydrogenase (mdh1, mdh2), Succinyl-CoA (Oxct1), Hydroxyacyl-coenzyme a dehydrogenase (hadh), Dehydrogenase/reductase (SDR family) member 1 (dhrs1)) interacted strongly with each other. In turn, they can increase the level of mitochondrial respiration and mitochondrial function, leading to color changing of tilapia fillet. The heat shock 60kD protein 1 (chaperonin, hspd1) interacted with metabolic enzymes (cs and mdh2) and had important effects on color. These results could help researchers better understand the color changing mechanism on the surface of tilapia fillet during the storage.

Isolation and characterization of antioxidant peptides from oyster (Crassostrea rivularis) protein enzymatic hydrolysates.

Peptides from oysters have several bioactive functions. In this study, we identified antioxidant peptides from oysters (Crassostrea rivularis) and investigated their structure-function relationship. We used an 8 kDa molecular-weight (MW) cut-off membrane and semiprep reversed-phase liquid chromatography to collect five peptides (F1-F5) and identified the highest-abundance ion-peak sequences AWVDY (F1), MSFRFY(F2), EPLRY(F3), RKPPWPP(F4), and YAKRCFR(F5) having MWs of 652, 850, 676, 877, and 943 Da, respectively, using ultra-performance liquid chromatography-quadrupole/time-of-flight tandem mass spectrometry. These peptides exhibited high antioxidant activities, similar to butylated hydroxytoluene, reduced glutathione, and ascorbic acid. F5 demonstrated the highest scavenging activity for DPPH radicals (IC50 = 21.75 µg/ml), hydroxyl radicals (IC50 = 18.75 µg/ml), and superoxide radicals (IC50 = 11.00 µg/ml), while F3 demonstrated the highest reducing power. Furthermore, F5 significantly protected Caco-2 cells from H2O2-induced oxidative damage. These results suggest that the antioxidant peptide F5 is a promising food additive that protects against oxidative damage.

Microplastic pollution and its relationship with the bacterial community in coastal sediments near Guangdong Province, South China.

The ecological stress caused by microplastic (MP) pollution in marine environments has attracted global attention. However, few studies have investigated the relationship between MP pollution and the microbial community in natural sediments. This study was the first to systematically characterize MP pollution (i.e., its abundance, shape, size and color) and investigate its relationship with the bacterial community in coastal sediments from Guangdong, South China, by microscopic observation and Illumina sequencing. The results of this study indicated that the abundance of microplastics (MPs), which was 344 ± 24 items/kg in 33 coastal sediments from 11 sites from South China, represented a relatively high level of MP pollution. MPs with sizes of <0.5 m, 0.5-1.0 mm and 1-2 mm accounted for the highest proportion (75%) in the sediments. Fiber/film (82%) and white/blue (91%) were the dominant shapes and colors, respectively, in all MP samples. Furthermore, the abundances, three shapes (fiber, film and fragment), three sizes (<0.5 mm, 0.5-1.0 mm and 1-2 mm), and two colors (blue and white) of MPs displayed positive correlations with some potential pathogens, including Vibrio, Pseudomonas, Bacillus and Streptococcus, but exhibited negative correlations with an environmentally friendly bacterial genus, Sphingomonas (which degrades various hazardous organic compounds), indicating that MPs might increase the potential ecological risks of coastal sediments. Our results may help to elucidate the relationship between MP pollution and the microbial community in coastal sediments.

Application of UHPLC-Q-TOF-MS/MS metabolomics approach to investigate the taste and nutrition changes in tilapia fillets treated with different thermal processing methods.

Thermal processing is a common processing method for tilapia which has an important impact on the quality and characteristics of fish meat. This study aimed to investigate changes in the metabolites of tilapia fillets after thermal processing. In this work, we used a UHPLC-Q-TOF-MS/MS metabolomics method to identify and screen differential metabolites. A total of 249 metabolites were identified from tilapia fillet samples, 24, 29 and 24 differential metabolites were screened from steaming/raw, boiling/raw and air frying/raw groups, respectively. Thermal processing significantly changed the quality of tilapia fillets, and the contribution of amino acids, phospholipids and nucleotides to different metabolites was large and had important impacts on the taste and nutrition of tilapia fillets. Metabolomics is an effective method for quality detection of thermal processing in aquatic products. This study provides the theoretical basis for the selection of optimized processing methods for tilapia.

Investigation of fermentation-induced changes in the volatile compounds of Trachinotus ovatus (meixiangyu) based on molecular sensory and interpretable machine-learning techniques: Comparison of different fermentation stages.

Fermented golden pomfret (Trachinotus ovatus) is appreciated by local consumers owing to its distinct flavor. Electronic nose (E-nose) and gas chromatography-ion mobility spectrometry (GC-IMS) technologies were used to analyze the changes in volatile compounds responsible for evolution of the golden pomfret odor profile during fermentation. Forty-five ion peaks were detected using GC-IMS. Although aldehydes represented the major initial volatile compound group, their levels decreased as fermentation proceeded. Between 3 and 15 days, increased levels of esters contributed to a stable volatile organic compounds profile. After 18 days, high levels of indole and pyrazines were detected. Eleven key volatile compounds were screened based on partial least squares discriminant analysis (PLS-DA). Back propagation artificial neural network (BP-ANN) predicted the fermentation stage enabling the development of better strategies to regulate golden pomfret fermentation. This study provided a theoretical basis for real-time monitoring and quality control of Chinese fermented golden pomfet.

Red color-related proteins from the shell of red swamp crayfish (Procambarus clarkii): Isolation, identification and bioinformatic analysis.

Two water-soluble red color-related proteins with the molecular masses of 24 and 73 kDa were purified from the shell of Procambarus clarkii. Initial color changes of these two proteins were detected at 30 °C and the large amount of red precipitate were obtained at 80 °C. PAGE analysis showed that the 24 kDa protein was the monomer, while the 73 kDa protein was the trimer. Identification revealed that these two proteins belonged to the hemocyanin subunit 2 family. With respect to the amino acid sequence similarity, the red color-related proteins shared the highest sequence identity with the hemocyanin derived from giant freshwater prawn (Macrobrachium rosenbergii). The phylogenetic tree analysis also clearly supported this finding. The shell-derived red color-related proteins show potential use as the edible thermal-sensitive indicator in food processing field.

Novel insight into the formation mechanism of volatile flavor in Chinese fish sauce (Yu-lu) based on molecular sensory and metagenomics analyses.

Complex microbial metabolism is the basis for flavor formation in traditional fish sauce. To guide the targeted regulation of production quality, we used molecular sensory and metagenomics analyses to determine dynamic changes in volatile flavor compounds and microbial communities of fish sauce as fermentation progressed. In total, 56 volatile compounds were identified; of these, 3-methylthiopropanal had the highest average odor activity value. Twelve volatile compounds, key for fish sauce flavor development, were identified. Bidirectional orthogonal partial least squares analysis was applied to investigate the correlation between microorganisms and flavor substances. Five microbial genera including Halanaerobium, Halomonas, Tetragenococcus, Halococcus and Candidatus Frackibacter constituted the core microbial flora responsible for flavor formation. The microbial metabolic pathways degraded raw materials into primary metabolites, such as glucose, amino acids, and fatty acids. This study provides novel insights into the flavor formation mechanism of traditional fish sauce fermentation.

The effects of different extraction methods on composition and storage stability of sturgeon oil.

The objective of this study was to assess the effect of different extraction methods on oil yield, colour attributes, oxidative stability, fatty acids composition and production of volatile compounds in sturgeon oil during storage. The supercritical fluid extraction (SFE) method with carbon dioxide resulted in higher oil yields, better colour attributes, and higher oxidative stability compared to other traditional extraction methods such as enzymatic extraction, amino, and wet reduction. After storage at 4 °C for 33 days, the aldehyde content in oil extracted by the enzymatic extraction and wet reduction methods was twice as high as that obtained by the other methods. There was a significant reduction in the content of total acids in oils extracted by the enzymatic extraction and wet reduction methods (p<0.05), whereas amine compounds were mainly detected in oil extracted by the amino method. The oil extracted by SFE exhibited higher UFA and lower SFA. Significant diffidence among PUFA with C above 20 was observed in oil extracted with SFE.