教学课程资源库 更多>>

关键词： Aquificota   Persephonella   hydrothermal   chemolithoautotroph   temperature   thermophile  

摘要： A novel thermophilic, microaerophilic and anaerobic, hydrogen- sulphur- and thiosulphate-oxidising bacterium, designated MO1340(T), was isolated from a deep-sea hydrothermal chimney collected from the Lucky Strike hydrothermal vent field on the Mid-Atlantic Ridge. Cells were short, motile rods of 1.4-2.2 mu m length and 0.5-0.8 mu m width. Optimal growth was observed for a NaCl concentration of 2.5 % (w/v) at pH 6.5. As for other members of the genus Persephonella, strain MO1340(T) was strictly chemolithoautotrophic and could oxidise hydrogen, elemental sulphur or thiosulphate using oxygen as electron acceptor. Anaerobic nitrate reduction using hydrogen could also be performed. Each catabolic reaction had a different optimal growth temperature (65 to 75 degrees C) and an optimal dissolved oxygen concentration (11.4 to 119.7 mu M at 70 degrees C for aerobic reactions) that varied according to the electron donors utilised. These experimental results are consistent with the distribution of these catabolic substrates along the temperature gradient observed in active hydrothermal systems. They strongly suggest that this adaptive strategy could confer a selective advantage for strain MO1340(T) in the dynamic part of the ecosystem where hot, reduced hydrothermal fluid mixes with cold, oxygenated seawater. Phylogenetic analysis indicated that strain MO1340(T) was a member of the genus Persephonella within the order Hydrogenothermales as it shared a 16S rRNA gene sequence similarity <95.5 % and ANI respectively 75.66 % with closest described Persephonella (P. hydrogeniphila 29W(T)). On the basis of the physiological and genomic properties of the new isolate, the name Persephonella atlantica sp. nov. is proposed. The type strain is MO1340(T) (=UBOCC-M-3359(T) =JCM 34026(T)). (C) 2021 Elsevier GmbH. All rights reserved.

关键词： Whey protein isolate   Citric acid-treated   Dynamic high-pressure homogenization pre-treatment   Physicochemical and functional characteristics  

摘要： This study investigated the physicochemical and functional characteristics of citric acid (CA)-treated whey protein isolate (WPI) by dynamic high-pressure homogenization (DHPH) at different pressure levels (0, 25, 50, 75, and 100 MPa, 3 cycles). The number of macromolecular polymers increased in CA-treated WPI with DHPH at 0-100 MPa by the analysis of molecular size distributions. DHPH can reduce the particle size of WPI and CA treated WPI. Additionally, the content of free sulfhydryl groups and surface hydrophobicity of WPI and CA treated WPI increased after DHPH treatment (p < 0.05). Also, DHPH promoted gel formation in the CA treated WPI, with the gel hardness increased by 43.66% after DPHP pretreatment at 100 MPa (p < 0.05). Meanwhile, after DPHP pretreatment at 100 MPa, emulsifying activity index (EAI) of CA-treated WPI and WPI increased by 13.15% and 27.36%, respectively (p < 0.05). Thus, DHPH pretreatment could enhance the degree of crosslinking of the CA-treated WPI and improve its gel and emulsifying properties, broaden the application of WPI in food processing.

关键词： Starch-lipid complex   Wheat endogenous lipids   Physicochemical properties   Noodle quality  

摘要： The physicochemical properties of starch-wheat germ oil complex (SWGOC) and its influences on the water distribution and hardness of noodles were investigated. The results showed that SWGOC retarded the retrogradation, lowered the breakdown value and solubility, and increased the swelling power of starch compared to the control. The T-21 (immobilized water) of starch dough made by SWGOC was lower than that of the control, however, the T-21 of raw noodles increased slightly from 0.12 ms to the maximum 0.13 ms and then decreased to 0.10 ms with the increase of SWGOC. The pasting profile of SWGOC during the holding phase (95 degrees C) suggested the dissociation of starch-lipid complexes during cooking. The released amylose predominantly induced double-helix at 0 h, resulting in the higher initial hardness of noodles, while the combination of liberated lipids and amylose occurred concomitantly but in a slower rate, reducing the firming rate during the first 2 h. Interestingly, the anti-firming effect was not proportion to the content of starch-lipid complexes, and noodles with less starch complexes seemed to be more effective in reducing firming rate. This study provides insight into the importance of starch-wheat endogenous lipids on noodle quality.

关键词： synthesis   theophylline derivatives   diuretic activity  

摘要： A method was developed for preparing previously unreported 8-amino-substituted 7-ethyltheophyllines, potential biologically active compounds. Their physicochemical properties and diuretic activity were studied.

关键词： Ascorbic acid  

摘要： The objective of this study was to determine the optimal thermoultrasound processing conditions for jackfruit nectar by applying response surface methodology and comparing the physicochemical parameters, antioxidant properties, microbiology, and fatty acid profile with pasteurized jackfruit nectar. Optimal condition was 80% of amplitude at 45 +/- 1 degrees C for 20 +/- 1 min, allowing physical stability of 68%, 60% of pectin methylesterase activity, ascorbic acid of 420 mg AA/L, total phenolic of 134 mg GAE/L, ABTS, DPPH, and chelating activity of 3,510 mu mol TE/L, 75 mu mol TE/L, and 96%, respectively. The thermoultrasonicated jackfruit nectar had lower microbial load and higher total soluble solids, ascorbic acid content, total phenolic content, antioxidant activity than pasteurized, and similar unsaturated fatty acids to the untreated sample. Our results demonstrated that thermoultrasound could be an option for processing jackfruit nectar as an alternative to pasteurization that allows successful inactivation of microorganisms, inactivation of enzymes, and good quality parameters. Practical applications Based on consumer demand for more natural or fresh-like products, alternative technologies have been evaluated by research works looking to reduce the effects of heat treatments in the Food Industry. Among these technologies, thermoultrasound technology have gained relevance and seems to be a good replacement to inactivate microorganisms and enzymes without affecting the quality parameters, maintaining the unsaturated fatty acids content, and even increasing bioactive compounds. For example, the thermoultrasound application in jackfruit nectar has been demonstrated as a viable preservation technique to develop an innocuous nectar without affecting their food quality. Nevertheless, in order to solve the challenges about potential applications of ultrasound technology, further research is needed to obtain optimal processing conditions according to the food matrix q

关键词： Lactic acid  

摘要： This study aims to explore the impact of fructooligosaccharides (FOS) on physicochemical, rheological, and microbiological properties of lactose-free functional yogurts fermented with probiotic cultures. Milk was hydrolyzed by addition of beta-galactosidase and supplemented with FOS at 3% (wt/wt). Lactose hydrolysis and FOS supplementation increased acidification rate during fermentation of yogurts. FOS helped to improve syneresis but resulted in weaker gel network. Viability of lactic acid bacteria increased when FOS was added. The results suggest that it is possible to obtain a lactose-free yogurt with functional properties contributing in improved nutritional characteristics suitable for people with lactose intolerance. Practical applications Lactose intolerance affects more than 75% of world population. This lactase deficiency condition limits people from consuming healthy dairy products. Although yogurts are known to have reduced lactose content, their lactose content, in fact, is still high. Manufacturing of low lactose and lactose-free milk has been developed. However, the variety of products is limited. In this present study, development of lactose-free yogurts enhanced with fructooligosaccharides as prebiotics was studied. Physicochemical, rheological, and microbiological characteristics of yogurts were evaluated. We believe that dairy product manufacturers can benefit from our findings and utilize our approach to create a new functional product for people with lactose intolerance.

关键词： Mass transfer  

摘要： Sesame seeds have economic interest owing to their oil content (45%-60%, dry basis). A multilevel factorial design was created in order to analyze the effects of air temperature (120, 150, and 180 degrees C) and roasting time (20, 25, and 30 min) in a laboratory-scale fluidized-bed dryer. All treatments showed oil recovery values higher than 70%, except for roasting at 180 degrees C for 25 and 30 min. The roasting treatment at 180 degrees C for 20 min yielded oils with the best sensory properties and with acceptable values for chemical quality parameters: acid value (1.82 mg KOH/g oil), peroxides (not detected), oxidative stability index (11.58 hr), and antioxidants' content (total tocopherols: 410 ppm;total lignans: 9.54 g/kg oil). The combination of the seeds' roasting by fluidized-bed drying and oil extraction by screw-pressing, allowed obtaining high oil recoveries and products with high oxidative stability and sensory acceptability. Practical applications Sesame oil is popular among healthy-food consumers given its bioactive components, mainly tocopherols and lignans, which confer a relatively high oxidative stability. Sesame seeds are roasted to change their microstructure for oil accumulation, to intensify flavor, and to increase the levels of antioxidants in the oil. Regarding the production of high-quality roasted oil, the roasting of sesame seeds in fluidized-bed dryers and the subsequent oil extraction in screw-presses have never been reported together. High oil recoveries and roasted sesame oils with a healthy physico-chemical composition, great oxidative stability, and sensory acceptability would be achieved by the oilseed industry through the use of two widely known technologies. First, fluidized-bed drying offers a high degree of mixing, and uniform heat and mass transfer over conventional direct heating methods for seed roasting. Second, screw-pressing of roasted seeds represents a green alternative to solvent extraction, mainly for specialty oils, b

关键词： El-Guedid   Dry-salted meat product   Lactic acid bacteria   Coagulase negative staphylococci  

摘要： El-Guedid is an Algerian traditional meat-based product that is prepared from red meats. It belongs to the wide diversity of salted/dried meat products. This study described the physicochemical and microbiological properties of different products from four animal origins and during all the conservation. Results indicated that these products were mainly characterized by a low moisture with an average decrease of water content between 15.6% and 16.3% for all the samples, and a decrease in water activity ranging from 0.66 to 0.68, while the salt content ranged from 8.8 to 19.3%. A decrease in pH values oscillated from (6.3-6.4) to reach (5.2-5.5) at T0 and T365 consecutively, in all the samples. Microbial analyses revealed the absence of pathogenic bacteria such as Listeria and Salmonella but the sporadic contamination by Staphylococcus aureus up to one month of ripening. Lactic acid bacteria and coagulase negative staphylococci were the dominant populations in El-Guedid with Leuconostoc mesenteroides, Lactobacillus sakei, and Staphylococcus saprophyticus as the main species identified. All these populations decreased along the process and reached low levels (2 log CFU/g) at the end of storage (365 days). The drastic drying of El-Guedid led to safe traditional meat product that could promote its production.

关键词： Electron beam   Irradiation   Inactivation   Mycotoxin   Quality   Red pepper powder  

摘要： This study reported the impact of electron beam (e-beam) treatment on microbiota and mycotoxins naturally present in red pepper powder and physicochemical quality changes. Treatment at 6 kGy indicated significant (p < 0.05) decontamination of yeasts and molds by 3.0 and 4.4 log CFU/g, respectively. A reduction of 4.5 log CFU/g of total plate counts (TPC) was observed at 10 kGy for 23 s. Fungal inactivation followed first-order kinetics while TPC better fitted with Gompertz function (R-2 = 0.9912). E-beam treatment was not efficient for the degradation of aflatoxins but indirectly controlled their production by inactivation of mycotoxigenic molds. Indeed, reduction of 25% ochratoxin A was recorded at 30 kGy retaining >85% of total phenols, carotenoids and antioxidants activity. Moreover, treatment impact on total color difference (Delta E*) indicated 'slight differences'. Overall, e-beam treatments up to 10 kGy were efficient in decontaminating the natural microbiota without detrimental effects on the physicochemical qualities of red pepper powder.

关键词： color   fries   phosphorus   reconditioning   starch grains   storage   temperature  

摘要： This work aims to determine the effect of time, temperature of storage and the reconditioning process on the physico-chemical characteristics of isolated starch of the potato cultivar used in the production of french fries. The storage and reconditioning processes result in a significant reduction in the large-size grain (SSG) fraction > 40.1 mu m. Long-term storage (nine months) results in a significant increase in acidity (SA) and a decrease in the amylose (AM) content in starch by 16.5% and 1.3%, respectively. A significantly lower starch stability (SDS) is obtained after storage at a higher temperature (6 degrees C) and it is 36.6% and 38.8% lower on average for the starch without reconditioning and after reconditioning, respectively. The phosphorus (P-tot) content in starch after harvest averages 647 mg kg(-1). Starch from potatoes stored at 2 degrees C or 6 degrees C contains on average 1.5% more P(tot)than starch from tubers before storage. The starch lightnessL-value significantly depends on the SSG (r = 0.851) and SA (r = -0.760). The best french frie quality (FFQ) values are obtained for starches extracted after harvest and reaches 4.8 points. Reconditioning of tubers after storage results in a significant improvement in the FFQ (0.8 point).