A further amendment to the classical core structure of gum arabic (Acacia senegal)

Using the more recently available techniques such as methylation–GC–MS, 1D (¹H, ¹³C) and 2D (COSY, TOCSY, HMQC and HMBC) NMR spectral analysis, we have revisited the classical structure of gum arabic (Acacia senegal). Methylation and GC–MS analysis confirmed that gum arabic (A. senegal) is a highly branched polysaccharide with the backbone composed of 1,3-linked galactopyransyl (Galp) residues substituted at O-2, O-6 or O-4 positions. The terminal sugar residues are 59.5% of the total sugars. The residues of →2,3,6-β-d-Galp1→, →3,4-Galp1→, →3,4,6-Galp1→ and substitutions at O-2 and O-4 position were not identified in previous studies.     

Comparison of molecular and emulsifying properties of gum arabic and mesquite gum using asymmetrical flow field-flow fractionation

The molecular and emulsifying properties of gum arabic (GA) and mesquite gum (MG) were characterized using asymmetrical flow field-flow fractionation connected to multi-angle light scattering and refractive index detection. Properties such as molar mass, root-mean-square radius (r_rms), hydrodynamic radius (r_h), conformation, apparent densities and distribution of proteinaceous matter over the whole molar mass range were determined. GA displayed a low molar mass (3.4 × 10⁵ g/mol), protein-poor component (population 1) and a high molar mass (1.9 × 10⁶ g/mol), protein-rich component (population 2). MG displayed one molar mass population with an average molar mass of 1.1 × 10⁶ g/mol. For both GA and MG, the conformation (r_rms/r_h) was increasingly spherical with increasing molar mass. However, MG had higher values of r_rms/r_h for a specific molar mass suggesting differences in structure between GA and MG. The protein content increased with increasing molar mass for both gums, although to a higher extent for GA. Selective adsorption, during emulsification experiments, could be observed of population 2 of GA which may be due to a combination of the higher protein content and a more flexible structure rendering it more surface active than population 1. Comparing GA and MG in terms of emulsion stability, it could be concluded that GA-stabilized emulsions have considerably higher stability against coalescence.     

Rheological study of gum arabic solutions: Interpretation based on molecular self-association

This study deals with the rheological properties of aqueous solutions of gum arabic, the complex arabinogalactan polysaccharide containing about 2% protein. The flow behavior of control gum and a matured gum (EM2), which have different molecular associations, was investigated at different concentrations in water and added urea (6M) by rheological and dynamic light scattering methods. The influence of molecular association on rheological behavior of gum arabic solutions was studied. It was found that though Newtonian behavior was observed across a wide range of concentrations and at high shear rates, gum arabic solutions showed a pronounced shear thinning in low shear rate ranges. The maximum difference in viscosity between shear rate increasing and decreasing processes was observed at 6% for both control gum and EM2 in water, and at 3% for control gum and 9% for EM2 in urea solutions. The results demonstrated macromolecular association of gum arabic occurring in the solutions, and the observed time-dependent flow behavior reflected microstructural breakdown and re-building in the systems. This phenomenon was understood in view of the relationship between rheological properties and microstructural characteristics. A model was presented to interpret the rheological behavior, which is attributed to the occurrence of shear-induced breakdown and re-formation of gum arabic aggregates.     

Effects of guar gum and arabic gum on the physicochemical,sensory and flow behaviour characteristics of frozen yoghurt

This study investigated the effect of guar gum and arabic gum on physicochemical, sensory and flow behaviour properties of frozen yoghurt. The results indicated that gums significantly affected the viscosity, overrun and melting rate of frozen yoghurt. The highest overrun value was observed in sample containing 0.5% arabic gum. Frozen yoghurt containing 0.3% guar gum had the highest viscosity. The longest first dripping time was observed in sample containing 0.5% arabic gum. Flow behaviour of samples showed that all frozen yoghurts exhibited shear thinning behaviour. Guar gum at a concentration of 0.2% and arabic gum at a concentration of 0.5% presented the best total acceptability. The results of this study revealed that the frozen yoghurt produced with arabic gum had the better overall sensory and physicochemical characteristics.     

甘蔗混合汁粒径分布及陶瓷微滤膜过滤阻力研究

建立了甘蔗混合汁中颗粒粒径分布测定和分析方法;研究了0．1μm、0．2μm和0．45μm陶瓷微滤膜分析甘蔗混合汁时的阻力分布,探讨了不同膜元件主要阻力形式,确定了阻力分析方法。结果表明：致密性膜的制造精度越高,过滤料液时总阻力相对较小,孔隙率高的膜元件堵塞阻力随膜孔径减小而降低,利于膜通量的恢复和延长使用时间。     

Comparison of the viscosity of trehalose and sucrose solutions at various temperatures: Effect of guar gum addition

The viscosity of trehalose and sucrose solutions was measured and compared as well as the effect of adding guar gum. Viscosity measurements of trehalose and sucrose solutions were performed in the range 20-45 g/100 g; 0.1 g guar gum/100 g was added in mixed systems. Viscosity of trehalose or sucrose solutions was measured at 20, 27 and 34 °C. Trehalose solutions had always a higher viscosity than sucrose, with the biggest difference (p < 0.001) in the range 30-45 g/100 g. Addition of guar gum revealed a synergistic effect with both disaccharides, particularly for trehalose. Viscosity dependence on temperature was also analyzed by calculating activation energies for all systems studied.     

Steady-shear flow of semidilute guar gum solutions with sucrose, glucose and sodium chloride at different temperatures

Steady-shear flow curves of aqueous solutions of guar gum at 0.22% at different temperatures (5-65 °C), guar gum (0.22%) with sugars (sucrose or glucose) at different sugar/water ratio (0.10, 0.20 and 0.40) at 5 °C, guar-sugar (at 0.40 sugar/water ratio) at different temperatures (5-65 °C) and guar gum and guar-sucrose (0.40 sucrose/water ratio) with NaCl (1%) at 5 °C, were determined using a controlled-stress rheometer over a wide range of shear rate (1-1000 s⁻¹). Apparent viscosity increased with decreasing temperature and increasing sugar content independent of sugar type. Synergic effect on apparent viscosity due to sugar addition was found and was correlated with sugar content. Salt addition decreased slightly the apparent viscosity and increased the shear-thinning behaviour of the guar gum solution. Steady-shear flow curves were satisfactorily described by the Cross model. Semi-empirical correlations of Cross model parameters with sugar content and temperature were obtained.     

Evaluation of the effect of a novel membrane filtration system on the lifespan of frying oil

Frying oil has a limited lifetime which results in the disposal of approximately 67% of all used oil. The aim of this study is to determine the suitability of different membranes for purifying frying oil and investigate the application of continuous membrane filtration in a commercial deep fryer. Eleven different membranes were tested to assess their suitability for filtrating frying oil. A prototype continuous filtration system with an integrated membrane filter was developed for a deep fryer to assess the effect of continuous membrane filtration on oil degradation. The prototype was subjected to a frying test over 13 days and the results compared to those from a standard deep fryer. The prototype maintained total polar compounds (TPC) at an acceptable level of <12% and the oil remained light in colour even after more than 280 h of use, while TPC in the standard deep fryer rose to >27%.     

Effects of some anionic polysaccharides on the gelatinization and retrogradation behaviors of wheat starch: Soybean-soluble polysaccharide and gum arabic

Gelatinization and retrogradation behaviors of wheat starch were investigated in an aqueous system in the presence or absence of some anionic polysaccharides, soybean-soluble polysaccharide (SSPS), and gum arabic (GA). Weight-average molecular weight was almost equivalent between SSPS and GA, while z-average root-mean-square radius of gyration of GA was ca. twice as large as that of SSPS. The addition of each polysaccharide (0.1–1 w/v%) decreased the peak viscosity of the composite system (starch concentration: 5% or 13%) during gelatinization, and this effect of SSPS was greater than that of GA at the higher starch concentration. It also shifted the onset of viscosity increase to lower temperatures at the higher starch concentration, but no difference was seen in this effect between SSPS and GA. The addition of each polysaccharide (0.1–1%) decreased the amount of amylose leached during gelatinization, and this effect of SSPS was generally greater than that of GA. It hardly altered, on the other hand, the average particle diameter of the starch granules after gelatinization. “Starch ghosts” were less frequently observed microscopically in the presence of each polysaccharide, which appeared to exist around the surface of the starch granules to inhibit amylose leaching. The addition of each polysaccharide (0.5%) increased the rate constants, representing short-term (24 h) retrogradation of starch (5%). It also decreased the saturated dynamic storage modulus of the composite system after storage at 4 °C for 24 h, and this effect of SSPS was greater than that of GA with larger amount of syneresis generated. The results were discussed mainly in relation to the phase arrangement between starch components and each polysaccharide.     

Nanoencapsulation of EPA/DHA with sodium caseinate–gum arabic complex and its usage in the enrichment of fruit juice

In this study, encapsulating fish oil, as a source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), with multi-layered interfacial membranes using electrostatic attraction between sodium caseinate and gum arabic and its usage in the enrichment of fruit juice was investigated. Initially, optimum conditions for forming a stable complex between sodium caseinate and gum arabic were determined at pH 4 and at a concentration of 0.1 g/100 ml sodium caseinate-0.2 g/100 ml gum arabic. This complex was utilized for nanoencapsulation of fish oil. Encapsulation efficiency and particle size were obtained as 78.88 ± 2.89%, 232.3 nm, respectively. Fish oil nanocomplex containing 40–50–60 mg EPA + DHA were used in the enrichment of 100 ml fruit juice. After in vitro digestion, the bioaccessibility of EPA, DHA and EPA + DHA were found as 56.16 ± 6.39, 36.25 ± 5.38 and 47.37 ± 10.65 percent, respectively (p < 0.05). This study indicates that stable protein–polysaccharide complexes can be used for nanoencapsulating hydrophobic compounds such EPA and DHA, useful for enrichment of non- or low-fat beverages.     

高过滤性能石墨烯复合纳米纤维膜的制备及性能

将石墨烯(GR)纳米颗粒掺杂到聚丙烯腈(PAN)纺丝溶液中,利用静电纺丝技术制备石墨烯/聚丙烯腈(GR/PAN)复合纳米纤维膜。研究PAN质量分数、GR用量、纺丝电压及接收距离对GR/PAN复合纳米纤维膜形貌和过滤性能的影响,发现最优纺丝工艺参数为PAN质量分数14.0%、GR用量1.5%、纺丝电压26 kV、接收距离14 cm、注射速度1 mL/h。此最优纺丝工艺参数制备的GR/PAN复合纳米纤维膜的过滤效率为98.86%,过滤阻力为110.30 Pa。     

Membrane‐Filtered Olive Mill Wastewater: Quality Assessment of the Dried Phenolic‐Rich Fraction

A current trend in olive mill wastewater (OMWW) management is to not only decrease environmental pollution but also to extract and utilize valuable by‐products. Therefore, the objectives of this study were to explore different techniques for drying a phenolic‐rich membrane filtration fraction of OMWW and compare the techniques in terms of the dried product quality and feasibility of the process. The OMWW from 2 (3‐phase and 2‐phase) California mills was subjected to a 2‐step membrane filtration process using a novel vibratory system. The reverse osmosis retentate (RO‐R) is a phenolic‐rich coproduct stream, and the reverse osmosis permeate is a near‐pure water stream that could be recycled into the milling process. Spray‐, freeze‐, and infrared‐drying were applied to obtain solid material from the RO‐R. Drying of the RO‐R was made possible only with addition of 10% maltodextrin as a carrier. The total soluble phenolics in dried RO‐R were in the range 0.15 to 0.58 mg gallic acid equivalents/g of dry weight for 2‐phase RO‐R, and 1.38 to 2.17 mg gallic acid equivalents/g of dry weight for the 3‐phase RO‐R. Spray‐dried RO‐R from 3‐phase OMWW showed remarkable antioxidant activity. Protocatechuic acid, tyrosol, vanillic acid, and p‐coumaric acid were quantified in all dried RO‐R, whereas 3‐hydroxytyrosol was found in 3‐phase dried RO‐R. This combination of separation and drying technologies helps to add value and shelf‐stability to an olive oil by‐product and increase environmental sustainability of its production.     

Cold ultrafiltered or microfiltered milk retentates: A systematic comparison of the effects of compositional differences on their gelation functionality

The colloidal stability of casein micelles suspensions prepared using ultrafiltration (UF) and microfiltration (MF) was studied by testing acid- and rennet-induced destabilization. Skim milk and 4× (based on volume reduction) concentrates were obtained by processing under similar conditions, at temperatures below 10°C. Concentrates were subjected to different levels of diafiltration (DF), resulting in samples with comparable casein volume fractions but different amounts of proteins and ions in the serum phase. The novelty of the work is the systematic comparison of MF and UF concentrates of similar history. More specifically, concentrates similar in ionic composition but with or without serum proteins were compared, to evaluate whether whey proteins and β-casein depletion from the micelles will play a role in the processing properties, or whether these are affected solely by the ionic balance. Microfiltered micelles' apparent diameter decreased by about 50 nm during the specific hydrolysis of κ-casein by chymosin, whereas those in skim milk control showed a decrease of about half that size. All concentrates subjected to extensive DF showed smaller hydrodynamic diameters, with reductions of ∼18 and 13 nm for MF and UF, respectively. Highly diafiltered UF retentates showed a delayed onset of rennet-induced gelation, due to low colloidal calcium, compared with other samples. Low-diafiltered samples showed weak storage modulus (∼1 Pa) after 60 min of onset of gelation. In addition, onset pH increased with diafiltration to ∼5.8 for UF and ∼6 for MF in high-diafiltered samples. These results clearly demonstrated that the functional properties of casein micelles change during membrane concentration, and this cannot be solely attributed to changes in ionic equilibrium.     

Study on the Membrane Filtration of Mash with Particular Respect to the Quality of Wort and Beer

The quality of a membrane filtered wort, and the beer from it, is different from that produced with a lauter tun or mash filter. A membrane is capable of producing a clear wort in terms of turbidity while solid contents, in particular larger molecular substances, are retained. The selectivity of separation is not directly set by the membrane's pore size but rather by the formation of the fouling layer. Thus an interaction between technical filtration parameters and selectivity determines the quality of the resulting wort and beer. The filterability of a beer produced with a membrane filter system for lautering was considerably better when a poorly modified malt was used and foam stability was worse when a normally modified malt was used. For all other properties examined in the beers, no significant differences between lauter tun and membrane filtration including sensory characteristics were observed.     

Simultaneous multiresidue analysis of 41 pesticide residues in cooked foodstuff using QuEChERS: Comparison with classical method

The principal objective of this study was to develop a simple multiresidue method involving a quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction method for the identification and quantification of 41 pesticide residues in cooked foodstuffs including cooked potatoes, radishes, and rice using GC-μECD. The analytes were subsequently confirmed via GC–MS. The results were then compared using the classical method established by the KFDA. The quantitation of individual pesticides was based on matrix-matched calibration curves with a correlation coefficient in excess of 0.993 for the 41 pesticides selected herein. Using QuEChERS, the mean recoveries ranged between 68.6 and 130.0% for the majority of the tested pesticides; however, the classical method exhibited low recoveries for dichlofluanid, tetraconazole, oxadixyl, fenbuconazloe, and paclobutrazol. After QuEChERS, the LODs and LOQs ranged between 0.004 and 0.3 μg/kg and 0.0125 and 1.0 μg/kg, respectively. The proposed method was applied successfully to determine the residue levels in cooked foodstuffs, and none of the samples contained detectable amounts of pesticide residues.     

Comparison of the rheology of bubbly liquids prepared by whisking air into a viscous liquid (honey) and a shear-thinning liquid (guar gum solutions)

Many bubbly liquids found in food applications feature non-Newtonian liquid phases whereas most investigations of bubbly liquid rheology have employed Newtonian liquids as the continuous phase. The influence of the nature of the continuous phase on bubbly liquid rheology was investigated using bubbly liquids prepared in the same planetary mixer using a viscous liquid, honey (almost constant shear viscosity with a small elastic contribution) and a shear-thinning liquid (1 wt% aqueous solution of guar gum). The viscosity of the honey was similar to the low-shear-rate limit viscosity of the guar gum solution. Although similar bubble volume fractions (up to 25%) were entrained in each liquid under identical mixing conditions, the bubble diameters in the shear-thinning liquid were about two to three times larger than those in the honey. Introduction of a surfactant into the shear-thinning liquid increased the volume fraction of bubbles to approx. 40% and further increased the size of the bubbles. The presence of the bubbles in the honey caused it to become shear-thinning, to exhibit noticeable elastic effects and exert significant normal stress differences. The honey-based bubbly liquids exhibited many of the features in the simulations of Loewenberg and Hinch (1996) and fitted the model of Llewellin et al. (2002) well. In the guar gum solution, these characteristics, already present, were accentuated strongly by the presence of the bubbles. Subjecting both types of bubbly liquids to high shear rates caused the volume fraction of bubbles to decrease and made the bubbly liquids less shear-thinning. Noticeable thixotropy was observed. Shear-thinning, associated with bubble deformation, was observed at lower values of the relative shear stress in the shear-thinning liquid.     

具有B-D反应项的捕食系统解的稳定性

讨论了一类带Bedd ington-DeAngelis反应项的捕食-食饵模型在Neumann边界条件下解的性质.利用极值原理和算子谱理论,得到在扩散系数不相同的情况下系统解的耗散性及非负常数平衡态解的稳定性.结果表明,该系统在参数满足一定的数量关系时,两物种不可能长期共存.     

Comparison of two strategies for systemic antibiotic treatment of dairy cows with retained fetal membranes: preventive vs. selective treatment

The objective of this study was to evaluate the efficacy of a blanket systemic preventive treatment (PT) of cows having retained fetal membranes (RFM) with 1 mg/kg of ceftiofur administered the first day after calving regardless of their body temperature. This strategy was compared with a selective treatment (ST) strategy in which only cows having RFM and a rectal temperature ≥ 39.5°C within 10 d postpartum received ceftiofur. Cows that retained their fetal membranes for at least 24 h after calving were allocated to 2 groups. Rectal temperature was measured daily for 10 d postpartum. Sixty PT cows having RFM received a daily ceftiofur (1 mg/kg of body weight) treatment, administered subcutaneously during the first 3 d after diagnosis of RFM. If rectal temperature was ≥ 39.5°C after 3 daily treatments, cows received ceftiofur for 2 more days. Therapy in 53 ST cows was based on selective administration of ceftiofur to cows having fever during the first 10 d postpartum. Treatment was conducted for 3 to 5 consecutive days as described for PT cows, beginning on the first day of fever. In both groups, manual removal of the placenta was not attempted and antibiotic drugs were not administered into the uterus. For every cow having RFM enrolled in PT or ST, 1 cow without RFM that had calved on the same day was enrolled in a healthy control group (n = 113). All cows received two 25-mg doses of PGF_2α: 1 dose between 18 and 24 d and 1 dose between 32 and 38 d postpartum. The PT did not reduce the proportion of cows experiencing fever during 10 d postpartum compared with ST cows (71.7 vs. 69.8%). Results were compared using logistic regression models and survival analyses. The artificial insemination submission rate between 42 and 62 d postpartum was greater in PT (41.2 vs. 20.8 vs. 24.5%), but total conception rate was less in ST and control cows, respectively (25.0 vs. 38.9 vs. 36.2%). In this trial, a preventive systemic antibiotic treatment of all cows having RFM was not superior to a selective antibiotic treatment of cows only in case of fever.     

Effect of thermal and non‐thermal pasteurisation on the microbial inactivation and phenolic degradation in fruit juice: a mini‐review

Fruit juice has been traditionally preserved by thermal pasteurisation. However, the applied heat can cause detrimental effects on health‐promoting components such as phenolic compounds. Several non‐thermal technologies such as membrane filtration, pulsed electric field (PEF) and ultraviolet (UV) exposure are promising methods developed for liquid food preservation. In particular, the combination of UV and PEF has proven to be more effective for microbial inactivation and maintaining nutritional quality of fruit juice compared with individual applications. © 2012 Society of Chemical Industry