查看更多>>摘要：The characteristics, kinetic mechanisms and biological activities of glycosylated alpha-lactalbumin prepared under microwave heating (MH) and conventional heating (CH) at 85 degrees C for 1-3 h were compared and investigated. Glycosylated alpha-lactalbumin prepared by microwave heating showed a higher degree of browning and more free amino groups as compared to preparation by conventional heating. Studies of the reaction kinetics demonstrated that microwave heating induced a higher rate constant at 75 degrees C, 85 degrees C and 95 degrees C. Similarly, the activation energy of the microwave-mediated process was 8.27 kJ/mol lower than under conventional heating, indicating that microwave heating accelerated the glycosylation of alpha-lactalbumin. The glycosylated alpha-lactalbumin produced in the microwave showed greater surface hydrophobicity after 3 h than the conventionally heated product. Glycosylated alpha-lactalbumin produced via microwave heating also showed higher total antioxidant capacity and alpha-glucosidase inhibitory activity. Therefore, microwave heating effectively promotes alpha-lactalbumin glycosylation and enhances the functional properties and biological activities of glycosylated alpha-lactalbumin.
查看更多>>摘要：Brassica vegetables are typically cooked or processed prior to consumption, resulting in inactivation of endogenous myrosinase; intact glucosinolates (GLSs) released during digestion are then hydrolyzed by gut bacteria. To understand release behavior of GLSs from vegetable matrix, two experimental systems, namely, dynamic in vitro rat stomach-duodenum (DIVRSD) model and conventional shaking-incubator in vitro digestion model, were comparatively utilized. Bioaccessible contents of selected GLSs, i.e., sinigrin, glucoraphanin and glucobrassicin, that could be released upon digestion of white cabbage powder, which was used as test material, were monitored. Approximately 92% and 82% of sinigrin and glucobrassicin in cabbage powder were released within 10 min during digestion in DIVRSD model. No degradation of these GLSs occurred during either simulated digestion process. Contractions mimicking gastric peristaltic waves in DIVRSD model facilitated release of GLSs, especially glucoraphanin; the content observed in DIVRSD model was around 4-fold higher than that in shaking-incubator model. DIVRSD model could well capture continuous digestion process and transport behavior of GLSs along the GI tract. After digestion in DIVRSD model for 180 min, a decrease in GLSs contents in the stomach (20-29%) and an increase in GLSs contents in the duodenum (63-80%) were clearly observed.
查看更多>>摘要：Vacuum microwave drying (VMD) technique was applied for drying fresh navel orange peel (NOP) under different vacuum degrees including 0, 25, 45, 65, and 85 kPa. Compared with the traditional hot-air drying (HAD), the drying time of VMD was remarkably reduced by 90.7-94.7%. In addition, the drying time had a negative correlation to the vacuum degree, the drying time at 85 kPa was only 5.3% of HAD. The extraction yield of VMD pectin was significantly higher than that of HAD. Comparing to HAD, the extracted pectin by VMD exhibited an increase in the degree of methoxylation, but a decline in the average molecular weight and apparent viscosity. Moreover, the VMD can promote pectin adsorption capacities to the Pb2+ with the adsorption mechanism of the pseudo-second-order kinetic model. These findings indicated that VMD is a powerful, efficient, timesaving technology for drying fresh NOP and assisting extraction of pectin from NOP.
查看更多>>摘要：Worldwide, despite concerns about the possibility of Salmonella presence in eggs and the recommendations of regulatory agencies, soft-cooked eggs are served. Studies indicate that eggs cooked at low temperature for long times are able to inactivate Salmonella at safe levels. There are two main low cooking methods used in food services, thermocirculator (tested in a previous study) and steam oven, not yet validated. This study was undertaken to analyze the survival of Salmonella during soft-cooked eggs processing by steam oven. Five strains of Salmonella were inoculated in egg yolks and incubated at 37 degrees C, for 18 h, reaching 8.1 +/- 0.1 log10 CFU/g. Contaminated eggs were processed at 62 degrees C for 52 min in asteam oven and samples were collected for the purpose of investigating Salmonella survival. Results indicated that the egg's center temperature reached 58.7 +/- 0.4 degrees C after 17 min and no Salmonella was detected. After 52 min of cooking, yolk remained liquid. The results of this study demonstrated that soft-cooked eggs processing by steam oven showed similar results to the processing by thermocirculator and can also be used by chefs and food processors in order to validate another way of serving soft-cooked eggs safely.
查看更多>>摘要：This study aimed to investigate the effect of cellulose nanocrystals (CNCs) combined with octenyl succinic anhydride modified starch (OSAS) on the stabilization of oil-in-water emulsions. Hydrogen bond and intermolecular electrostatic interaction were found in the formation of CNCs-OSAS complex as characterized by molecular dynamics simulation. A relatively stable emulsion could be formed by ultrasonic emulsification when the concentrations of CNCs-OSAS complex in the weight ratio of 2:8 and oil were 1.5 wt% and 10 wt%, respectively. Increase in Z-average diameter of emulsion prepared with the CNCs-OSAS complex (81.3 nm at 25 degrees C for 30 days) was considerably less than that of OSAS-stabilized emulsion (116.8 nm at 25 degrees C). No creaming was observed in emulsion prepared with the CNCs-OSAS complex after 30 days of storage. The apparent viscosity of emulsion stabilized by the CNCs-OSAS complex was 1.4 times as high as that of OSAS-stabilized emulsion when shear rate was 0.01 s(-1). Increased viscoelasticity of emulsions in the presence of CNCs probably enhanced the interaction between droplets and delayed the creaming of emulsions. This study provided a new perspective to broaden the application of CNCs and OSAS in "green" emulsion.
查看更多>>摘要：Alcalase hydrolysis of soybean proteins was shown effective in degrading epitopes, but with a significant loss of tastes and functional properties. In this study, the combined use of controlled Alcalase hydrolysis and transglutaminase (TGase)-cross-linking was used to produce hypoallergenic soybean protein hydrolysates (SPHs) with improved flavor and techno-functional properties. Through establishing the kinetic model of heterogeneous enzymatic processes, SPHs with different degrees of hydrolysis (2.5-10.0%) were obtained and polymerized by TGase to yield products with various peptide components. Results showed that post-hydrolysis cross-linking rearranged the (poly)peptides in SPHs via glutaminyl modifications. Following TGase-treatments, due to the masking of bitter-active peptides and free amino acids, the bitterness of SPHs was significantly reduced with a slight improvement in the overall flavor. Furthermore, TGase-cross-linking rescued multiple technofunctionalities of SPHs, particularly their emulsifying and foaming properties. Using sera from soybeanallergic individuals, it was evidenced that TGase-addition did not generate neoallergens and the residual allergenicity of SPHs was not distinctly affected. The final products maintained 44-71% reduction in the IgE-binding levels in comparison to the unhydrolyzed protein. Combining limited Alcalase hydrolysis with TGase-crosslinking provides a feasible way to produce hypoallergenic soybean ingredients with desired flavor and functional attributes.
查看更多>>摘要：In the present study, a combination of microwave and thermosonication treatment was introduced in the soymilk extraction process, and the process was optimized to minimize the enzymatic activity of Soybean Trypsin Inhibitor (STI) and Lipoxygenase (LOX) enzymes. Protein content, fat content, TSS (Total Soluble Solids), and viscosity of soymilk increased upon thermosonication process and was most affected by microwave time followed by ultrasonification time. The inactivation rate constant for STI and LOX was 0.2034 min(-1) and 0.3232 min(-1), respectively, indicating LOX was more susceptible to inactivation under microwave treatment as compared to STI. The activation energy of STI and LOX decreased from 48.44 to 10.24 kJ/mol and 53.47 to 3.07 kJ/mol after 5 min of microwave pasteurization. FTIR analysis confirmed the conformational deformation of proteins and enhanced molecular interactions in the optimized soymilk. The optimized condition was obtained as 3 min of microwave pasteurization followed by 30 min of ultrasonication at 60 degrees C in an ultrasonic bath of 28 +/- 2 kHz frequency. The optimized treatment produced the soymilk with enhanced nutritional quality and low enzymatic activities.
查看更多>>摘要：Volatiles in four Allium tenuissimum flower samples were detected and characterized by headspace-gas chromatography-olfactometry-mass spectrometry, and odor activity values. The key aroma compounds were determined by combining the sensory analysis with the omission and recombination experiments. The results illustrated that a total of 36 volatiles were identified and divided into six types, including sulfur-containing compounds, aldehydes, alcohols, ketones, nitrogen-containing compounds, and others. The sulfur-containing compounds and aldehydes were the two most abundant compounds in A. tenuissimum flower. The volatiles were quantified through authentic reference compounds, and the contents of these compounds in four A. tenuissimum flower samples were obtained. Five key aroma compounds of A. tenuissimum flower were confirmed as dimethyl disulfide, dimethyl trisulfide, linalool, 2-methylbutanal, and nonanal. Among these, the predominant compounds dimethyl disulfide and dimethyl trisulfide having strong onion and sulfur aroma, significantly contributed to the aroma of A. tenuissimum flower. The main aroma profiles of A. tenuissimum flower were onion, sulfur, flower, green and burnt. The closer the geographical location and environment of A. tenuissimum flower growth are, the more similar their chemical composition.
查看更多>>摘要：Transglutaminase (TGase) has high value to the field of food processing due to their protein cross-linking capacity. Compared with the widely used TGase from Streptococcus mobaraensis (MTG), Bacillus subtilis-derived TGase (BTG) exhibits higher thermal stability and broader range of pH, and is thus better suitable to food processing conditions. However, BTG's cross-linking preferences and characteristics are still unclear, restricting the application in food process. In this study, a modified in vitro RNA display was used to efficiently screen BTG's peptide substrates with a high library capacity. The results showed that BTG preferred to cross-link the Q sites around which were hydrophobic residues in the substrate sequences. LC-MS analysis validated that the top five screened peptides indeed showed high cross-linking rates by BTG. Moreover, the molecular dynamics simulation indicated that their binding affinity with BTG was mainly due to van der Waals interaction, which explained the cross-linking preference of BTG on the substrate. This study provided knowledge about BTG's cross-linking preference and characteristics, which will benefit the comprehensive understanding of BTG and promote its rational application in food industry.
查看更多>>摘要：This study aimed to compare the effects of extrusion and recrystallization treatments on the structural and physicochemical properties and digestibility of corn (CS) and potato starch (PS). CS and PS were conditioned at 40 % and 60 % moisture content and extruded at 40 degrees C-120 degrees C. The extrudates were stored for 1, 7, and 14 days at 4 degrees C for recrystallization. The structural properties of extruded CS (ECS) and extruded PS (EPS), as well as the crystallization and thermal properties, water solubility, water absorption, and in vitro digestibility of recrystallized ECS (RECS) and recrystallized EPS (REPS), were evaluated. Compared with native starch, both ECS and EPS exhibited a significant decrease in their measured molecular weight. The chain length distribution did not change significantly, but the amylose content increased remarkably. Both RECS and REPS with 60 % moisture content presented a typical B-type pattern, and RECS exhibited V-type characteristic peaks. The melting signals of recrystallized amylopectin (46-64 degrees C) and amylose (136-158 degrees C) of RECS were detected. In vitro digestion experiments showed that RECS had lower digestibility than REPS. The highest slowly digestible starch and resistant starch contents of RECS were approximately 3.5 and 6.5 times that of unextruded CS, respectively.
NSTL
Elsevier