查看更多>>摘要：The aim of this work was to investigate the effects of pH and temperature on the structural characteristics of the Pediococcus pentosaceus R1 protease, which was isolated from Harbin dry sausage. UV-vis, fluorescence, circular dichroism and Fourier transform infrared spectroscopy were used to evaluate the structural changes as a function of pH and temperature. The protease had a stable spatial structure at pH 5 and 30 degrees C, and the extended secondary structures of the protease were identified. The structure of protease was changed at pH 8 and 70 degrees C, with changes predominantly manifested as changes in secondary structure components, the alpha-helices, beta-sheets, beta-turns and random coils contents at pH 8 were 5.32%, 37.08%, 19.45% and 38.22%, respectively; and at 70 degrees C the contents were 5.47%, 40.62%, 19.56% and 34.35% respectively, which were significantly different from that at pH 5, 30 degrees C. Carbonyl vibration (1651 cm(-1)), -NH vibration (1540 cm(-1)), C-H stretching vibration (2959-2857 cm(-1)) and disulfide bonds (560-460 cm(-1))were identified in P. pentosaceus R1 protease under various pH and temperature conditions. Molecular docking showed that the protease can interact with actin and myoglobin, which indicates certain options for the application of this enzyme in the fermentation of Harbin dry sausage.
查看更多>>摘要：In this study, 1500 W, 40 kHz ultrasound was used to treat chicken muscle during 5 days of ageing after slaughter. Ultrasound treatment-induced typical apoptosis was applied to chicken muscle after slaughter. Our Western blot results showed that the key factors of the death receptor pathway in apoptosis fas, fas-L, and caspase-8 were activated during storage of the meat. Treatment with ultrasound significantly stimulated the activity of caspase-9, cytochrome c and tbid, and increased the ratio of bax/bcl-2 as shown by western blotting analysis. Transmission electron microscopy images showed ultrastructural damage to the mitochondria and nucleus that was morphologically characteristic of apoptosis during post-mortem ageing. All the treatments reduced the band intensity of desmin and caspase-3 during 5 days of meat ageing. The hematoxylin-eosin staining of muscle tissue structure showed that ultrasound treatment increased the gap between muscle fibre bundles. Ultrasonic treatment significantly reduced the shear force of chicken breast, which could improve the tenderness of the meat. The findings of this investigation revealed that ultrasound affected meat ageing via apoptosis and possibly activated myofibril degradation. We speculate that the morphological and biochemical changes relating to apoptosis have the potential to contribute to the tenderization of meat.
查看更多>>摘要：Cloudy apple juice were subjected to ultrasound treatments at various power levels (525, 975, and 1125 W) and temperatures (50, 60, and 70 degrees C). The effects of temperature-controlled ultrasound treatment (TCUT) on the microbial load, color, sensory evaluation, total soluble solids, water soluble pectin (WSP), rheological properties, stability, and antioxidant activity of cloudy apple juice were investigated. Ultrasound and thermal treatment play a synergistic role in the reduction of microbial populations and could achieve microbial safety. TCUT enhanced the sensorial properties and improved the content of WSP, while reducing the particle size. TCUT significantly improved the rheological properties and suspension stability of apple juice. Moreover, the phenol content and percentage of DPPH inhibition also increased by TCUT in apple juice. The optimized TCUT conditions was at 60 degrees C with 1125 W power for 12min. The juice showed inactivation of microorganisms (<1 log CFU/mL), a preferable sensory property, obvious decreasing in particle size, more WSP, and better cloudy stability.
查看更多>>摘要：In this study, the effects of ultrasonication (0, 200, 300, 400, 500 and 600 W) on the intrinsic fluorescence spectra, surface hydrophobicity (H-0), particle size, ultraviolet (UV) spectra, emulsifying properties and solubility properties of Cyperus esculentus seed protein (CEP) solutions were investigated. An increase in ultrasound power significantly improved emulsifying activity and emulsion stability of CEP (P < 0.05). After ultrasonication, the solubility of CEP increased from 41.29% to 67.53%. Various spectral methods, such as the Fourier infrared spectroscopy, fluorescence spectroscopy, and ultraviolet spectroscopy, showed that ultrasonication changes the structure of the CEP protein, expose the water-transporting groups, and improves the hydrophobicity of the surface. The particle size and turbidity of the protein emulsion significantly decreased after ultrasound treatment, indicating that the particles in the protein solution became smaller and more uniformly distributed. The scanning electron microscopy (SEM) confirmed the results, verifying that the protein particle size was dramatically reduced after ultrasound treatment. This study provides a theoretical basis for the application of CEP in food processing.
查看更多>>摘要：In this study, the effect of two hot air drying conditions (40 degrees C for 23 h and 60 degrees C for 9 h) on the content, antioxidant activity, microstructure, and luminescence properties of persimmon carotenoids in three ripening stages was studied. Based on the results from total carotenoids content and HPLC analysis, the carotenoid's content increased with the advance of ripening, highlighting the beta-cryptoxanthin fraction. In addition, drying treatments did not affect the carotenoid content and profile but decreased the antioxidant activity. Microstructural studies showed that the ripening progress and/or drying treatments, led persimmon tissues to lose integrity, allowing the diffusion of carotenoids and their degradation. Photoluminescence measurements evidenced the synthesis of beta-cryptoxanthin during the fruit ripening. After drying, a new emitting specie at 340 nm was attributed to the carotenoid's isomerisation while the emission at 500 nm experienced a shift that was related to the formation of thermal degradation products. Both facts could explain the loss of antioxidant activity in persimmon submitted to drying treatments. In this sense, photoluminescence, in combination with spectro-photometric, chromatographic and structural techniques, helps to understand the phenomena caused by both, ripening and drying treatments, in the persimmon's carotenoids fraction.
查看更多>>摘要：This research aimed to find a natural biological preservative that inhibits harmful bacteria in the food production process. We screened a bacteriocin-producing Lactobacillus plantarum SHY 21-2, which was isolated from yak yogurt. The bacteriocin was purified by salting out, AKTA purifier 10 and reversed-phase high-performance liquid chromatography (RP-HPLC). The LC-MS/MS analysis revealed that the molecular weight of bacteriocin was 1362.84 Da and the predicted the amino acid sequence was RPNEPRLLLPR. This strain produced a novel IId bacteriocin and named plantaricin LP 21-2. LP 21-2 was heat-resistant and still had 96% antibacterial activity after being exposed to 121 degrees C for 15 min. LP 21-2 had obvious antibacterial activity at pH 2-5 and could be completely inactivated by pepsin, trypsin, and papain. LP 21-2 had a broad antimicrobial spectrum against on Gram-positive bacteria, Gram-negative bacteria and fungi, including Staphylococcus aureus ATCC25923, Salmonella typhi CMCC50071 and Saccharomyces cerevisiae ATCC9763. The minimal inhibitory concentration (MIC) of LP 21-2 on Staphylococcus aureus ATCC 25923 was 0.18 mg/ml. Analyzed by scanning electron microscopy and transmission electron microscopy, LP 21-2 induced pore formation in cell membranes and caused cytoplasmic leakage to kill bacteria. These results indicate that plantaricin LP 21-2 has potential as a bioprotective agent in food.
查看更多>>摘要：The impact of sous-vide cooking (So-Vc) temperature and time on the quality and shelf-life of crab lump meat (CLM) was elucidated. CLM was treated with sous-vide at varying temperatures (75, 80 and 85 degrees C) and times (1 and 2 h). Regardless of the cooking regime, no microorganisms were detected in CLM after treatment with So-Vc (svt-CLM). Lipid oxidation became more pronounced in svt-CLM as time and temperature augmented (p < 0.05). No significant alterations in protein pattern were observed in svt-CLM. Lightness in CLM was increased after treatment with sous-vide, except for those treated at 85 degrees C, in which lightness was decreased. A gradual decrease in poly- and mono-unsaturated fatty acid with increasing temperature and time was observed for svt-CLM. So-Vc profoundly influenced the shelf-life of CLM, in which the shelf-life longer than 60 days at 4 degrees C was recorded. Therefore, So-Vc was demonstrated as an effective mild heat treatment for shelf-life extension of CLM, and the cooking condition of 80 degrees C for 1 h is recommended for CLM based on the less impact on color and lipid oxidation, assured microbial safety, and reduced energy consumption.
查看更多>>摘要：Desert truffles are popular ectomycorrhizal fungi valued worldwide for their nutritional and traditional health benefits. Herein, two chief desert truffles viz., Terfezia claveryi and T. boudieri were assessed for their metabolites heterogeneity in context of their volatile sensory and nutrients profile as analyzed via GC-MS. Primary metabolites accounting for nutritive indices in T. claveryi and T. boudieri were investigated with 61 peaks belonging to sugars, sugar alcohols and amino acids. After headspace solid-phase microextraction (HS-SPME), a total of 106 volatiles were annotated belonging to alcohols, ketones, aldehydes, esters, ethers and furans. The abundance of oxygenated monoterpenes as antimicrobials rationalizes for the folk use of desert truffles against trachoma. Benzyl isothiocyanate was detected as the sulfur containing volatile component in desert truffle and absent from truffles. Multivariate data analyses (MVA) revealed that 1-octen-3-ol and 3-octanone were the most significantly contributors in the discrimination of T. claveryi and T. boudieri specimens. Being more enriched in essential amino acids, T. claveryi provided a better sugar diet composition concurrent with lower sugars and higher sugar alcohols compared to T. boudieri. This study provides the first insight into desert truffles metabolites and sensory composition, and to account for its culinary and medicinal uses.
查看更多>>摘要：In this study, we used the lytic Siphovirus phage LPST10 to develop a rapid and accurate detection method for Salmonella. Salmonella cells were separated from complex food matrices through magnetic separation, then subjected to SYBR green-based real-time quantitative PCR detection. Bacterial concentrations of 10(2)-10(6) (Colony forming unit per milliliter, CFU/mL), with 200 of mu g LPST10 phage-MBs, and 15 min reactions at 37 degrees C were found to be optimal to allow the phage-magnetic beads to capture the Salmonella cells. The phage-magnetic beads specifically recognized Salmonella cells of different serotypes. Under optimal conditions, DNA was extracted from the resulting bacteria phage-magnetic bead complexes through either alkaline lysis with sodium dodecyl sulfate (SDS) or boiling. The detection assay was subsequently assessed in food matrices (Tryptic soy broth medium, milk, and lettuce). The detection limit reached <30 CFU/mL in the food matrices. The entire assay, including bacterial capture, DNA extraction, and real-time polymerase chain reaction (RT-PCR) detection, could be completed within 1.5 h. This approach using a lytic Siphovirus phage has potential for rapid, specific, and accurate detection of Salmonella enterica subsp.enterica in different food matrices.
查看更多>>摘要：Unsaturated fatty acids in vegetable oil are prone to lipid oxidation that leads to rancidity, subsequently, the oil's nutritional value is compromised. Edible oils can be tailored to obtain an antioxidant-rich oil blend with better oxidative stability under accelerated storage conditions. In this research, the oxidative stability of the six oil blends containing rice bran oil (RBO: 50-75%), flaxseed oil (FO: 5-10%), peanut oil (PO: 20-40%) at different concentrations is assayed by Arrhenius and Eyring equations (R-2 > 0.95, p < 0.05) under Rancimat test conditions (100, 110, 120, 130 degrees C @ air flowrate 20L/h). The activation energy (E-a), enthalpy change (Delta H), and entropy change (Delta S) of control and oil blends ranged from 74.28 to 93.59 kJ/mol-K, 71.05-90.36 kJ/mol, -41.87 to -100.19 J/mol-K, respectively. Addition of RBO increased tocopherol and oryzanol content in oil blends from 398 to 725 ppm, 0.7 to 1.0 %g, respectively. Hierarchical cluster analysis conferred that RBO-PO-FO: 75-20-5, had better oxidative stability (induction period, IP100: 21.34 h) comparable to RBO with a slower kinetic rate and can be used as a functional oil source. Better understanding of the influence of oil blending on quality traits was delineated by principal component analysis.
NSTL
Elsevier