查看更多>>摘要：In the present work, a probiotic bacteria Weissella cibaria MD2 was used for the production of exopolysaccharide (EPS), which was characterized and evaluated for several technological and biological activities. The RSM assisted optimization resulted in maximum production of EPS (12.58 g/L) when the MRS broth was supplemented with optimal carbon and nitrogen source. The EPS produced was purified using chromatography techniques and the monosaccharide analysis by HPLC showed that it was a fructan EPS. The NMR analysis suggested that the EPS MD2 is an inulin-type linear polysaccharide that consists of beta (1 -> 2) linkage. The scanning electron microscopy (SEM) images revealed that EPS MD2 has a thin sheet-like appearance with fewer fibers-like structures. The results from the thermal analysis showed that the EPS MD2 was highly thermostable and possess a degradation temperature of 279.90 degrees C. The x-ray diffraction pattern showed that the powdered EPS MD2 has a semi-crystalline nature. The EPS MD2 showed excellent antioxidant activities to scavenge free radicals. The fructan EPS showed a promising effect in increasing oxidative stress tolerance and enhancing the lifespan of C. elegans by activating the nuclear localization of DAF-16. The incredible physico-chemical and antioxidant properties (in vitro and in vivo) of this EPS can be implemented in the pharmaceutical and food industry.
查看更多>>摘要：Demand for camel milk (CM) is increasing worldwide, due to its high nutritious value and health benefits. In this study, whole CM powders were produced by spray drying (SD) at six inlet temperatures (190 degrees C-250 degrees C) and by freeze drying (FD). Physicochemical and functional properties of CM powder proteins were investigated. SD at higher inlet temperatures (230 degrees C-250 degrees C) resulted in higher extent of Maillard reaction (MR), in comparison to lower temperatures (190 degrees C-200 degrees C) and FD treatment. Both treatments had negative effect on casein solubility, while whey proteins remained soluble and slightly increased its solubility with the extent of MR. The CM powders obtained at higher inlet temperatures demonstrated improved antioxidant activity. Secondary structure of whey proteins did not differ among the samples, while surface hydrophobicity of whey proteins was higher in all SD than in FD samples, suggesting only limited denaturation of camel whey proteins at higher inlet temperatures of drying. Thus, the effects of SD under the conditions applied in our study did not decrease camel whey protein solubility, while drying procedure itself regardless of temperature decreased solubility of camel milk caseins. MR generated during CM processing could be an important means of compensating for the lack of antioxidant protection normally associated with beta-lactoglobulin but happens to be absent from this milk.
查看更多>>摘要：The antimicrobial activity of blend of essential oils and their nanoemulsions against Clostridium sporogenes inoculated in mortadella with sodium nitrite reduction (75 ppm) was evaluated. In addition, physicochemical analysis such as pH, residual nitrite, lipid oxidation, a(w) and color were realized. Sensory characteristics of mortadella containing essential oils and their nanoemulsions were evaluated through a focus group and control difference test. Nanoemulsions were more effective than individual essential oils in reducing vegetative cells of C. sporogenes. The combinations of essential oils and their nanoemulsions acted as an antioxidant in the meat product and did not modify the other technological characteristics of the product. Although mortadella added with a natural preservative is an attraction, flavor and color variability must be considered. The present study showed good results for the application of essential oil nanoemulsions as a preservative in meat products and encourages further studies in this regard.
查看更多>>摘要：Protein oxidation can influence the quality of food during processing and storage. This study examined the changes in physicochemical properties and in vitro digestibility of egg white protein (EWP) oxidized with a peroxyl-radical-generating system (2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) simulating the oxidation environment of industrial processing. With the increasing AAPH concentration, all amino acid contents and protein solubility decreased, the carbonyl content almost doubled increased, free sulfhydryl content almost decreased by three quarters. The essential amino acids, such as phenylalanine, leucine, threonine, histidine was particularly sensitive towards oxidation, decreased by more than 10% after EWP oxidized by 5.0 mmol/L AAPH. Volume of larger soluble aggregates formed by AAPH increased, and the digestibility of EWP, decreased with the increase of oxidation degree. Molecular weight analysis showed that the content and antioxidant activity of low molecular weight peptides obtained by pepsin hydrolysis or trypsin hydrolysis was gradually reduced with the increase of the degree of oxidation, which indicated that the nutritional and biological activity of EWP was reduced by oxidation. These results may help to understand the changes in the functional and nutritional quality of egg-based foods that involve oxidation during processing.
查看更多>>摘要：Eurotium cristatum, isolated from the unique stage of "fahua" in Fuzhuan brick tea, contributed greatly to aroma formation of fermented tea. This study aimed to characterize the main amino acids, tea polyphenols, volatile organic components (VOCs) and sensory qualities both in pure (E. cristatum) and mixed fermentation (E. cristatum, Aspergillus niger and Penicillium oxalicum) with summer-autumn tea as substrate. Amino acid content increased by 10.7% and 14.3% both in pure and mixed fermentation, respectively. Differently, tea polyphenols decreased rapider in pure fermentation (6%) than mixed fermentation (2.7%). Venn diagram indicated that more kinds of VOCs (286) were produced by synergetic effect of mixed strain compared with pure fermentation. PCA was performed to visualize the differences of VOCs, 2,6-dimethyl-1,5-heptadiene (93) and 2-ethyl-1-hexanol (95) were closely related to mixed fermentation, whilst, trans-linalool oxide (furanoid) (118), acetone (120), D-limonene (123) and diazene, dimethyl- (125) were closely related to pure fermentation. Moreover, two-way ANOVA exhibited that the effect of starters (F, 7940.846) on VOCs is more significant compared with fermentation time (F, 421.813). Mixed fermentation product provided better sensory proterties with the higher yield of 11.83% and score of 87.81 than pure fermentation. In summary, mixed fermentation of E. cristatum combined other strains may be a new channel to develop wasted summer-autumn tea.
查看更多>>摘要：Characterization of volatile off-odor compounds in thermal duck egg gels was investigated by gas chromatography-olfactometry-mass spectrometry (GC-O-MS), odor activity values (OAVs) and aroma recombination. The results demonstrated that the off-odor of thermal duck egg mainly came from egg yolk (EY), and content of aldehydes was the highest in EY. Anaerobic treatment in nitrogen contributed to decreased off-odor sensory scores and volatile components of the heated egg gels. Aerobic EY gels (treated in air) were determined to contain eight volatile compounds with OAVs greater than 1, such as hexanal, nonanal, benzaldehyde, (E)-2-octenal, (E)-2-nonenal, (E, E)-2,4-decadienal, 1-octen-3-ol and 2-pentylfuran. However, three key volatile components (nonanal, benzaldehyde and (E)-2-nonenal) with OAVs greater than 1 were found in anaerobic EY gels. Moreover, on the basis of results of recombination and omission experiments, hexanal, (E)-2-octenal, (E, E)2,4-decadienal, 1-octen-3-ol and 2-pentylfuran were identified as key off-odor components in thermal EY gels. Sensory evaluation of the recombination model with five aroma compounds scored 4.38 out of 5 points. The major aroma profile of the off-flavor from egg EY gels included strong fatty, nutty, and mushroom aromas.
查看更多>>摘要：Low solubility and poor emulsifying properties of walnut protein isolate (WPI) greatly influences its applications in the food industry. In the current work, WPI was extracted and phosphorylated from defatted walnut flour by sodium trimetaphosphate (STMP) at various pH values (7.0, 9.0, and 11.0). The measured phosphorus content of STMP-extracted WPI was approximately 7-10-fold higher than that of the alkaline-extracted WPI (A-WPI). The results of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) further confirmed the successful phosphorylation of extracted WPI. Conformational studies using FTIR and circular dichroism (CD) indicated that phosphorylated WPI (P-WPI) contained higher a-helical and lower beta-sheet contents than the A-WPI. Phosphorylation of WPIs altered the surface hydrophobicity and surface charges of the proteins, resulting in a significant improvement in the solubility of P-WPI. In addition, the emulsifying properties of P-WPI were significantly enhanced, which was exhibited by a 2.5-4-fold increase in the emulsifying activity index (EAI) and a maximum 6-fold increase in the emulsifying stability index (ESI). The emulsions stabilized by P-WPI manifested relatively smaller sizes and larger surface charges. This study demonstrated that phosphorylation modification can effectively modulate the surface hydrophobicity and charges of WPI to greatly improve its solubility and emulsifying ability.
Jaiswal, AishwaryaPathania, VanshdeepLakshmi, Jyothi A.
9页
查看更多>>摘要：Iron and zinc deficiencies have emerged as controllable nutritional problems of concern all over the globe with varying intensities in all age groups. Additionally, the micronutrients especially zinc is associated with maintaining a sound immune system and hence enhancing the bioavailability of minerals to be an ideal strategy for alleviation of deficiencies. The investigation was undertaken to study the effect of spices on the digestibility of proteins and bioaccessibility of iron and zinc in complementary food mixes (CFM) and Indian flatbread mixes (IFBM). CFM and IFBMs were formulated and spices were added at 1 and 2% to the matrices and their effect on protein, iron and zinc bioaccessibility was determined. In CFMs, spices enhanced the bioaccessible iron by 3-6 fold and 1.7-2.5 fold in IFBMs and zinc bioaccessibility by 1.2-2.0 fold at 2% level in both the mixes. Thermal treatments showed further enhancement in nutrient digestibility at sensorial acceptable levels. To the best of our knowledge this is the first report demonstrating the beneficial role of spices on mineral bioaccessibility in CFM's and IFB's. Spices in addition to enhancing the mineral bioaccessibility is also known to boost immunity which is the need of the hour.
Nie, JingguiChen, DantingLu, YanbinDai, Zhiyuan...
9页
查看更多>>摘要：This paper aims to study the effects of hot water blanching, salt water blanching, microwave blanching, and steam blanching on the quality of Sargassum fusiforme using different detection indicators, such as fucoxanthin content, pigment composition, antioxidant activity (2,2-diphenyl-1-picrylhydrazyl and hydroxyl radical scavenging ability), and sensory quality. Results revealed that the blanching treatment exhibits dual effects of promoting dissolution and degradation of fucoxanthin. Besides hot-water blanching with 98.3 degrees C, the other three methods were not conducive to the retention of fucoxanthin. The Weibull model provides a good description of the degradation kinetics of fucoxanthin during blanching. For the radical scavenging assay, the extract obtained by microwave blanching had the strongest activity, followed by steam blanching. However, the other two kinds of blanching with water were not conducive to retaining activity. Sensory analysis revealed that the sensory quality could be better restored by blanching for a shorter time. Finally, the following three essential blanching conditions were selected from all the tests: the best pretreatment condition for fucoxanthin extraction: hot water blanching at 60 degrees C for 12 min; the best antioxidant activity: microwave blanching for 8 min; the best sensory quality: microwave blanching for 2 min.
查看更多>>摘要：Campylobacter jejuni is a common and important zoonotic pathogen that can cause bacterial gastroenteritis and other diseases, even leading to Guillain-Barre Syndrome or death. It is therefore necessary to investigate the prevalence and pathogenic risk of C. jejuni. Here, we investigated the prevalence of C. jejuni isolated from retail food in China from 2015 to 2016 and analyzed the distribution of virulence genes, antibiotic susceptibility, and genetic diversity of different isolates. Eighteen out of 1588 samples, collected from 15 main cities of China, were contaminated by C. jejuni, with more than 70% of the strains possessing 14 virulence-genes. Antimicrobial susceptibility testing suggested that all strains were resistant to vancomycin (100%) and cefoperazone (100%), and highly resistant to quinolones (>96%). In contrast, they showed sensitivity to erythromycin. Nevertheless, all the isolated strains were multi-drug resistant. Regarding genetic polymorphism, 20 sequence types (STs) were found by multilocus sequence typing (MLST), ten of which were new STs. Moreover, 40% of the strains could form biofilms, of which 23.33% strains were strong biofilm-forming. In conclusion, our study provides the prevalence and characteristics of C. jejuni isolated from retail food in China, revealing the potential pathogenic risk of C. jejuni in contaminated food.
NSTL
Elsevier