教学课程资源库 更多>>

关键词： ultra-high pressure   angiotensin-converting enzyme inhibitory activity   Lactobacillus delbrueckii QS306   fermented milk  

摘要： The present study investigated the influence of ultra -high pressure (UHP) treatment on angiotensin-convert-ing enzyme inhibitory (ACEI) activity and quality of milk fermented with Lactobacillus delbrueckii QS306 af -ter storage. By varying treatment pressure, duration of pressure treatment, and duration of fermentation, opti-mal process parameters for the UHP treatment of milk fermented with QS306 to enhance ACEI activity were found to be 400 MPa, 10 min, and 48 h, respectively. The degree of ACE inhibition of the fermented milk was 91.63 +/- 0.02%. After UHP treatment, ACEI activity, apparent viscosity, concentrations of polypeptides and volatile aromatic substances, umami, and richness had increased significantly, bitterness and astringency were significantly reduced, and antioxidant properties were maintained. In addition, UHP fermented milk main-tained a high level of ACEI activity and good quality during storage. Thus, the data represent a valuable reference for improving the storage quality of fermented milk and research for the future development of dairy products with high ACEI activity.

关键词： Physicochemical properties  

摘要： This study was carried out to investigate the effect of different levels (0, 2, 4, 6 and 8% w/v) of sweet lupine powder (SLP) and Bifidobacterium longum ATCC 15707 on physiochemical, textural, microbiological and sensory properties of low-fat bio-Labneh samples during storage for 21 days at 5 +/- 1 degrees C. The results showed that the textural properties of low-fat bio-Labneh with a higher level of SLP (8%) were harder than those made without adding SLP. Overall acceptability of sample processed by using 2% of SLP indicated that it is more acceptable compared with other treatments. The total cell count of B. longum ATCC 15707 gradually increased until the 14(th) day of the storage period after that decreased till the end of the storage period. Furthermore, the number of viable cells of B. longum ATCC15707 remained >7 log cfu/g at the end of the storage period in the treated samples. Novelty impact statement Sweet lupine powder had a positive impact on the quality characteristics of low-fat bio-Labneh and enhanced the growth of B. longum ATCC 15707 in the Labneh matrix that resulted in a wider spectrum of health benefits of Labneh cheese to the consumers. The Labneh that was supplemented with 2% sweet lupine powder was the most acceptable treatment.

关键词： Fourier transform infrared   Nuclear magnetic resonance   Genetic variants   Milk   Micellar casein   Structure  

摘要： This study highlights differences in conformational and physicochemical characteristics of bovine skim milk and micellar casein from cows of different beta-casein phenotypes. These genetic variants have been one of the pre -dominant topics among dairy researchers due to their differences in beta-casein structure, and thus their potential effects on dairy processing and human health. For characterising differences in milk protein structure, Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (H-1 NMR) spectroscopies combined with chemo-metric analysis were used. Additionally, physiochemical properties such as mineral content, particle size, and electrostatic charge in skim milk and micellar casein samples were analysed at 4 and 20 degrees C. Results showed variation in the secondary structure of all three genetic variants independent of temperature. Moreover, the main differences involved a higher level of beta-turn and alpha-helical structures in A1/A1 beta-casein milk, while intermolecular beta-sheets were more numerous in A1/A2 beta-casein milk, whereas random or polyproline II (PPII) structures were more common in A2/A2 beta-casein milk. Temperature slightly affected these differences, which was due to the dissociation of beta-casein from the micelle at low temperature. In addition, A2/A2 beta-casein milk and its micellar casein had a larger average particle size, which resulted in a lower negative zeta-potential. The A2/A2 beta-casein samples contained greater amounts of phosphorus and less calcium compared to the other genetic variants of milk and their micellar caseins. The results also indicated that a combination of FTIR and 1H NMR spectroscopies could be used to establish conformational differences in milk and micellar caseins of different genetic variants.

关键词： Yeast  

摘要： Prolonging shelf life of fresh-cut water chestnuts (FCWC) by vitamin E (vit E) was investigated. Browning degree, decay degree, and edible quality (EQ) of FCWC were evaluated as evaluation indexes of shelf life. Meanwhile, total soluble solids concentration, titratable acid (TA) concentration, ascorbic acid (AA) concentration, hardness, ethylene concentration, polyphenol oxidase (PPO) activity, peroxidase (POD) activity, total phenols (TP) concentration, counts of thermophilic bacteria, yeasts, and molds colonies were analyzed. Shelf life of FCWC could be prolonged for 4 days by soaking them in 0.04% (v v(-1)) vit E anhydrous ethanol (1% [v v(-1)]) solution for 30 min. Vit E probably inhibited the increasing of PPO and POD activities, and the declining of TP concentration and hardness. Vit E had little effect on counts of thermophilic bacteria, yeasts, and molds colonies of FCWC. These results indicated that vit E could prolong shelf life of FCWC.

关键词： FAU(Y)   ion exchange   cesium   alkylation   aniline   methanol  

摘要： This study investigates the effects of the degree of ion exchange of sodium cations for cesium cations in FAU(Y) on its physicochemical properties. Using aqueous and solid-state ion exchange, a number of NaY samples with an exchange degree of sodium cations for cesium cations varying from 29 to 89% were prepared. The samples were examined by SEM, X-ray fluorescence, low-temperature nitrogen adsorption, XRD, NH3-TPD, IR spectroscopy of adsorbed chloroform, and Al-27 MAS NMR. It was demonstrated that samples with exchange degrees up to 87% can be synthesized with their crystalline structure intact. The test of the catalytic properties of the synthesized samples in aniline alkylation with methanol showed a growth in the selectivity for N-alkylated products as the number and strength of basic sites were progressively increased. Impregnating the Cs-containing zeolites with CsOH was found to significantly enhance the operating stability of the samples and the yield of N-alkylated products, compared to CsNaY. The CsOH-modified catalysts with a Na+/Cs+ exchange degree of 54-77% proved to be the most active and stable in aniline alkylation with methanol: they provided aniline conversion of 81-88% and selectivity for N-alkylation products as high as 99.6-99.7 mol %.

关键词： Collagen film   Collagen fiber   Glutaraldehyde   Cross-linking   pH   Physicochemical properties  

摘要： Collagen films cross-linked with glutaraldehyde (GTA) at different pH values were prepared to explore the in-fluence of pH on their physicochemical properties. The films were characterized using FTIR spectroscopy, XRD analysis, SDS-PAGE, shrinkage temperature, fluorescence analysis and SEM. The results indicated that cross-linking degree and reaction position were different at different pH values. The optimal cross-linking degree in collagen films was obtained under neutral and alkaline conditions. The main reaction under acidic conditions was intramolecular cross-linking and this gradually shifted to intermolecular cross-linking with an increase in pH. Cross-linked films had improved mechanical properties and thermal stability as well as higher b* values compared to films without cross-linking. These improvements correlated with the degree and position of cross-linking reactions. Controlling the reaction pH can be used to modulate the physicochemical properties of the collagen films to match specific application requirements.

关键词： Germination  

摘要： The effect of soaking, germination, and roasting on some physicochemical properties of defatted Moringa seeds flour was studied using a 2(3) complete factorial design. Soaking was operated for 24 hr in water (1/10, w/v) with changing of water every 4 hr. Germination consisted of soaking seeds previously for 6 hr in water and sprouting for 8 days. Roasting was done at 140 degrees C/50 min. A total of eight treatments were then applied to the seeds which were then dehulled, finely ground, and defatted, and the resulting flours were submitted to physicochemical analysis. The results showed that particle size of defatted flour was bimodal (13 and 300 mu m). The whiteness index varied from 66.9 for the soaked-germinated-unroasted (***) sample to 79.8 for the nonsoaked-germinated-unroasted (***) sample. The moringa flours (treated or untreated) were concentrated in proteins (57.21-70.45 g/100 g DW). While the protein and crude fiber (3.11-5.20 g/100 g DW) contents significantly increased with the treatment, the carbohydrate (14.56-24.67 g/100 g DW) and total dietary fibers (22.99-38.28 g/100 g DW) diminished. The antinutrients/toxicants as saponins, oxalates, phytates, and trypsin inhibitors were significantly (p < .05) reduced with treatment. While most of the antinutrients were at low level in the flour, the glucosinolates were at remarkably higher levels which may induce toxicity if consumed. Glucosinolates ranged 5.84-7.95 g/100 g DW and were not reduced above the tolerance limit (0.79 g/100 g DW). In overall, the treatments induced important improvement of the nutritional quality of the flour with combined treatment being more efficient. Novelty impact statement The combined treatments (***., ***.R, NS.G.R, and S.G.R) were more efficient compared to single treatments (***, ***, and ***.R) with raw (untreated) sample (***) as a reference. The most efficient combined treatment was S.G.R. followed by ***, NS.G.R., and ***.R because they pro

关键词： Ascorbic acid  

摘要： Sweet corn kernels are easily perishable because of their high amount of moisture content. Microwave blanching was applied at the power level of 180-900 W for 30-70 s to inactivate the enzymes of sweet corn kernels. The increase in microwave power level and processing time reduced the length from 11.13 to 10.78 mm, width from 9.54 to 9.24 mm, thickness from 4.01 to 3.71 mm, true density from 1052.07 to 1012.03 kg/m(3), porosity from 37.43 to 24.54%, moisture content from 70.00% to 68.93% on a wet basis, total soluble solid from 22.3 to 18.7 degrees Brix, total sugar from 8.80% to 6.67%, ascorbic acid from 8.04 to 5.92 mg/100 g, and peroxidase activity up to 1.37% in sweet corn kernels, but it increased the bulk density from 658.23 to 763.6 kg/m(3) and total color difference up to 14.55. Novelty impact statement The microwave blanching was found adequate for processing sweet corn kernels at the power level of 720 W for a short duration of 40 s to achieve a 90% reduction in peroxidase activity. The ascorbic acid, total sugar, overall acceptability after the microwave blanching were 6.86 mg/100 g, 7.87%, and 8.21, respectively, indicating 85, 89, and 94% retention of fresh samples properties. The total plate count was 9.1 log cfu/g in fresh kernels, which was also reduced to 1.8 log cfu/g in kernels blanched at the power level of 720 W for 40 s duration.

关键词： Fermentation   functional properties   legumes   microstructural properties   nutritional properties   Rhizopus oligosporus  

摘要： The present study investigated the effect of fermentation by Rhizopus oligosporus on the nutritional, functional, colour and microstructural properties of some commonly consumed legumes, that is, chickpea (kabuli and desi), pigeon pea and soybean. Results revealed a substantial (P < 0.05) increment in the protein (5-14%) and ash (5-15%) contents as well as those of essential (13-21%) and non-essential (3-15%) amino acids with fermentation. Fatty acid composition showed the varied concentrations of polyunsaturated, monounsaturated and saturated fatty acids in fermented legumes. Further, fermentation significantly (P < 0.05) modified the functional and colour properties of legumes. The alteration in the structural conformation of legumes upon fermentation was observed with scanning electron microscopy which confirmed the enzymatic action on the proteins, fibres and lipid bodies. The results concluded that fermentation of these legumes could be a potential approach in developing the novel functional foods to address the concerns of food and nutrition securities.

关键词： Hydrogels  

摘要： The impact of three arabinoxylan (AX) cultivars (262, 44, 229) on the physicochemical, rheological, and microstructural characteristics of AX hydrogels was explored. The gelation of AX262 was faster and the viscoelastic modulus was higher. During the gelation process, the consumption of ferulic acids was 96%, 87%, and 69% for AX262, AX44, and AX229, respectively, indicating a higher oxidative cross-linking degree of AX262. The decline of adsorption intensity for AX262 hydrogel at 1,644 and 3,423 cm(-1) was more pronounced, which might be related to a denser gel network as a result of higher oxidation degree of FA. Meanwhile, AX262 hydrogel was more capable of binding water molecules and exhibited better thermal stability. The difference in the gelation properties of varied AX cultivars lied in the molecular structure. AX262 had a higher ferulic acid content (0.23 mu g/mg) and larger molecular weight with 1.17 x 10(6) Da, contributing to an enhanced oxidative cross-linking capacity. Novelty impact statement Wheat bran arabinoxylans extracted from strong gluten wheat cultivars with higher contents of FA were suitable to fabricate hydrogel system, due to their better oxidative cross-linking capacity. The prepared AX hydrogel had uniform honeycomb structure with enhanced thermal stability and mechanical properties, which could be potentially used as delivery system for bioactive compounds.