Effect Of Vacuum Mixing Research Articles

Effects of vacuum mixing and mixing time on the processing quality of noodle dough with high oat flour content

The effects of different mixing parameters (vacuum mixing and mixing time) on oat (70% oat flour) and wheat noodle dough were investigated on the basis of textural properties and gluten formation. The results showed that at a vacuum degree of −0.06 MPa and mixing time of 10 min, oat and wheat dough sheets exhibited the highest resistance to extension and glutenin macropolymer (GMP) content, and had the most compact and uniform gluten network. Compared with wheat noodle dough, oat dough had lower resistance to extension, lower tightly bound water content, and higher GMP content. Microstructural examination showed that oat noodle dough had a more aggregated distribution of gluten protein compared with wheat noodle dough under the optimum mixing parameters. Furthermore, the poor binding ability of vital wheat gluten with water molecules caused the indexes of oat noodle dough to be more strongly affected by the changes in mixing parameters than wheat noodle dough.

Effect of vacuum mixing and curing conditions on mechanical properties and porosity of reactive powder concretes

Abstract The paper contains quantitative characteristics of changes in the porosity and mechanical properties of RPCs caused by applying different pressures during concrete mixing, i.e. atmospheric pressure and pressure reduced to 500 and 40 mbar. The effect of curing conditions was determined as well: the impact of curing in water (Tmax = 20 °C), steaming (Tmax = 90 °C) and autoclaving (Tmax = 250 °C) on the porosity, compressive strength and flexural tensile strength of the materials tested. In addition, the maximum volumetric proportion of 6 and 14 mm steel micro-fibres which can be introduced in a standard manner, i.e. during the production of the RPC mix, was determined depending on their length. Besides the basic mechanical characteristics, tests of mechanical properties of RPCs containing fibres included the determination of the following parameters: σLOP (limit of proportionality), σMOR (modulus of rapture), Wf (work of fracture) and the toughness indices. Test results clearly confirm the considerable impact of pressure during RPC mixing and curing conditions on the durability and mechanical properties of the hardened composites. The maximum volumetric proportion of micro-fibres introduced during mixing was 8%. Steel fibre reinforcement was found to be more effective when longer fibres were used.

Dough and bread made from high- and low-protein flours by vacuum mixing: Part 1: Gluten network formation

The effects of reduced headspace pressure on the development of gluten network in doughs made from both high-protein flour (HPF) and low-protein flour (LPF) were investigated. The effect of vacuum mixing was found to be dependent on both flour-type and mixing-time. A significant increase in dough extensibility was observed when the HPF dough was mixed under moderate vacuum of −0.04 MPa for 3 min as compared to the one mixed under atmospheric pressure for the same duration. This was attributed to the formation of a more extensive gluten network associated with an increased disulphide bond density and a significantly higher β-sheet to β-turn ratio. On the other hand, over-mixing was observed in the LPF dough that was mixed for 5 min under atmospheric pressure. Applying moderate vacuum of −0.04 MPa allowed the LPF dough to withstand longer mixing time, as indicated by its increased disulphide bond density and biaxial extensibility compared to the control dough mixed under atmospheric pressure. Results of this study suggest the potential of applying vacuum to reduce the mixing time required for high protein flour and to prevent the over-mixing of low protein flour.

Influence of Vacuum Mixing on Structural Characteristics and Physical Properties of Noodle Dough

The effects of vacuum mixing on the structural characteristics and physical properties of noodle dough were investigated using three leading Chinese wheat cultivars. Texture profile analysis showed that vacuum mixed doughs when sheeted all gave significantly higher levels of adhesiveness, elasticity, and chewiness than doughs from nonvacuum mixing. The cross section of sheeted dough mixed at 0.06 MPa had a more continuous and compact microstructure with fewer holes and gaps, as well as more even protein distribution at the surface, as evidenced by scanning electron microscopy and Fourier transform infrared microimaging. However, a higher degree of vacuum was detrimental to the developed network for weak dough. Dough mixed at 0.06 MPa had higher glutenin macropolymer content and lower free thiol group concentration compared with nonvacuum mixed doughs, which may largely relate to the improvement of dough texture. The development of the gluten network for weak gluten flour was more sensitive to the degree of vacuum.

Effects of Vacuum Mixing, Water Addition, and Mixing Time on the Quality of Fresh Chinese White Noodles and the Optimization of the Mixing Process

In this study, the effects of mixing process parameters (degree of vacuum, water addition, and mixing time under vacuum) on the cooking and sensory quality properties of Chinese white noodles were investigated by using one commercial‐scale noodle production line and one typical commercial wheat flour. Noodle appearance, firmness, elasticity, smoothness, and total quality scores were significantly improved as the degree of vacuum increased from 0 to 0.06 MPa, although lower sensory scores and larger cooking losses occurred when noodles were mixed at 0.08 MPa. Noodles with a water addition of 35% had the highest total score and the highest scores for each sensory factor. As mixing time increased, the sensory score of cooked noodles increased initially and then decreased. With a mixing time of 7 min, the sensory score was the highest and cooking loss was the lowest. The results of response surface methodology indicated that fresh noodle quality was most affected by the water addition, followed by vacuum degree. Added water was a more important source of variation for appearance, firmness, stickiness, smoothness, total score, and cooking loss than degree of vacuum and mixing time, whereas degree of vacuum was the predominant source of variation for color and elasticity. The interactions between the factors had little effect on sensory and cooking properties. The optimal mixing conditions were determined to be as follows: degree of vacuum, 0.06 MPa; added water, 35.6%; and mixing time, 7.25 min. Furthermore, vacuum mixing produced a more even, coherent, and closed microstructure for the sheeted dough than nonvacuum mixing.

Delineating the protein changes in Asian noodles induced by vacuum mixing

In this study, the effect of vacuum mixing on Asian noodle qualities was investigated based on protein components changes and gluten formation. The results showed that the proportion of salt-soluble proteins decreased in vacuum mixed noodles while alcohol and alkali soluble proteins increased. The free sulfyhydryl content decreased significantly (P<0.05) in low protein (LP) noodles while slight and not significant (P>0.05) decrease was detected in high protein (HP) samples. Remarkable protein aggregates were observed in non-reduced SDS–PAGE patterns for LP noodles. The changes in secondary structure were reflected by the increase in α-helix and β-sheet as well as the decrease in β-turns. Furthermore, vacuum mixing conferred a more continuous and compact microstructure to both HP and LP noodle sheets as well as an increased breaking force and extensibility. In addition, less deterioration in noodle structure and water migration was observed by magnetic resonance imaging (MRI) for vacuum mixed samples during storage.

Effect of vacuum mixing on the quality characteristics of fresh noodles

Effect of vacuum mixing on the physicochemical properties, microstructure and water status of fresh noodles was investigated. Color changes, moisture, water activity, cooking quality and texture properties were measured as affected by different vacuum degrees. In addition, effect of vacuum mixing on the water status in noodles was evaluated at macroscopic, structural and molecular levels. Noodle brightness, cooking and texture properties were significantly (P<0.05) improved as vacuum degrees increased, except that −0.08MPa imparted slightly larger cooking loss and worse texture to low protein noodles. Both high and low protein flour noodles presented the best cooking and textural properties while mixed at −0.06MPa. Furthermore, vacuum mixing induced a more continuous and compact noodle structure, as shown in the SEM investigation. Water–solids interaction in the products was shown to be enhanced by the decreased water mobility, lower freezable water content (FW%), and the stronger proton density of T21.

Vacuum-Mixing Significantly Changes Antibiotic Elution Characteristics of Commercially Available Antibiotic-Impregnated Bone Cements

Evidence-based medicine indicates the use of antibiotic-impregnated polymethylmethacrylate bone cement during hip and knee replacement reduces the rate of prosthetic joint infection. In the United States, so-called off-label use of antibiotic-impregnated polymethylmethacrylate for primary joint replacement is increasing and multiple antibiotic-containing polymethylmethacrylate products are commercially available. However, there are sparse published data comparing the antibiotic elution characteristics of these bone cement products and the effect that vacuum-mixing has on antibiotic elution from these products. This study compares the antibiotic elution characteristics of six commercially available antibiotic polymethylmethacrylate formulations mixed under atmospheric pressure and vacuum conditions. The antibiotic-impregnated polymethylmethacrylate products were mixed with use of a commonly employed intraoperative technique at atmospheric pressure and clinically relevant vacuum conditions. A standard Kirby-Bauer bioassay technique was subsequently used to quantify antibiotic elution from the products. An international infectious disease database was mined to determine antibiotic susceptibility of common bacteria causing prosthetic joint infection and to define the gentamicin concentration above which optimal antibiotic efficacy begins for these organisms. Statistical analyses incorporating the above susceptibility data were performed to compare antibiotic elution (1) among products mixed at atmospheric pressure, (2) among vacuum-mixed products, and (3) between atmospheric and vacuum-mixing for each individual product. Comparisons of antibiotic-loaded polymethylmethacrylate products mixed at atmospheric pressure indicated that significant antibiotic elution differences exist among the products. Comparisons of vacuum-mixed antibiotic-loaded polymethylmethacrylate products indicated that significant antibiotic elution differences exist among the products. When mixing under atmospheric pressure was compared with vacuum-mixing for each individual antibiotic polymethylmethacrylate product, vacuum-mixing significantly increased the clinically relevant cumulative antibiotic elution from three products but significantly decreased antibiotic elution from three other products. The method by which antibiotic-containing polymethylmethacrylate products are prepared significantly affects their antibiotic elution characteristics. The effect of vacuum-mixing on antibiotic elution is product-specific.

An Important Backdrop to the Continued Discussion on the Use of Antibiotic-Containing Bone Cements

The use of antibiotic-containing polymethylmethacrylate, or antibiotic PMMA, in revision of a total hip or total knee replacement due to a previous infection is currently accepted practice. Additionally, despite lack of regulatory approval in the United States, the “off-label” use of antibiotic PMMA for primary arthroplasty by orthopaedic surgeons is substantial and has continued to increase. The widespread use of antibiotic PMMA in total joint replacement provides ample clinical relevance to the article by Meyer et al. regarding the effects of vacuum-mixing on six widely used antibiotic PMMA formulations. One of the strengths of the work is the logical study design. The authors utilize a previously reported methodology for creating pellets of uniform consistency with virtually identical geometry1. Thirty pellets of each antibiotic (fifteen vacuum-mixed and fifteen atmospheric) were evaluated each day during a five-day elution protocol and were compared between groups as …

Effect of Vacuum Mixing on Antimicrobial Activity of Commercially Available Bone Cements: An In vitro Analysis

Infection remains a significant cause of early and late implant failure after THA and TKA. Large prospective TKA and THA cohort studies indicate antibiotic bone cement (abPMMA) may decrease both the incidence of infection and revision. For these reasons, abPMMA utilization is increasing.

The effect of vacuum mixing and pre-heating the femoral component on the mechanical properties of the cement mantle

We investigated the effect of pre-heating a femoral component on the porosity and strength of bone cement, with or without vacuum mixing used for total hip replacement. Cement mantles were moulded in a manner simulating clinical practice for cemented hip replacement. During polymerisation, the temperature was monitored. Specimens of cement extracted from the mantles underwent bending or fatigue tests, and were examined for porosity. Pre-heating the stem alone significantly increased the mean temperature values measured within the mantle (+14.2 degrees C) (p < 0.001) and reduced the mean curing time (-1.5 min) (p < 0.001). The addition of vacuum mixing modulated the mean rise in the temperature of polymerisation to 11 degrees C and reduced the mean duration of the process by one minute and 50 seconds (p = 0.01 and p < 0.001, respectively). In all cases, the maximum temperature values measured in the mould simulating the femur were < 50 degrees C. The mixing technique and pre-heating the stem slightly increased the static mechanical strength of bone cement. However, the fatigue life of the cement was improved by both vacuum mixing and pre-heating the stem, but was most marked (+ 280 degrees C) when these methods were combined. Pre-heating the stem appears to be an effective way of improving the quality of the cement mantle, which might enhance the long-term performance of bone cement, especially when combined with vacuum mixing.

Effect of vacuum mixing and manual pressurisation on residual strains in polymethyl methacrylate bone cement mantles

Residual stresses associated with the polymerisation and subsequent cooling of PMMA bone cement are suspected to be responsible for the initiation of cement cracks following total hip arthroplasty (THA). A previous study has measured temperatures and strains developed in a twin cylinder construct representing the implant and femur, during and after bone cement polymerisation, for hand mixed PMMA bone cement. In the present study, the effect of manual pressurisation of the cement mantle is experimentally investigated through stem and femur strain measurements which are directly attributable to cement stresses. Manual pressurisation of the curing cement mass had a significant effect on the measured residual strains. The mean representative femur hoop residual strain was reduced from a compressive strain of -1802 (± 449.8) μe to tensile strain of 49 (± 374.3) μe, while the mean axial residual strain reduced from -649.2 (± 196.6) μe to -271.0 (± 173.6) μe. This study demonstrates that a reduction in net residual stress may be achieved by pressurisation of the bone cement mantle.

Mixing systems and the effects of vacuum mixing on bone cement.

The aim of a good cement mix is to produce bone cement that has the best mechanical properties possible in order that it can carry out its load transfer role successfully over the lifetime of the implant. The data presented shows that vacuum mixing reduces the cement porosity, which results in improved strength, and resistance to creep deformation and fatigue failure in the bone cement. It seems, however, that eliminating a high degree or all of the cement porosity may be detrimental because it leads to greater shrinkage and cracking in the material. A moderate vacuum level will improve the mechanical properties, but reduce the risk of thermal shrinkage and cracking which is seen at higher vacuum levels. In addition, the mixer design has a significant influence on the quality of the cement produced, affecting porosity, unmixed powder and subsequently the mechanical properties of the material. In the next issue we will be concluding this series of articles by covering the importance of temperature and its effects on the phases of the cement polymerisation process. Bone cement training courses are being run within hospitals by Summit Medical as part of our commitment to enhancing the skills of the perioperative practitioner and to ensuring the best long-term outcome for the patient.

Effect of vacuum mixing on the mechanical properties of antibiotic‐impregnated polymethylmethacrylate bone cement2

Polymethylmethacrylate bone cement, containing either no added antibiotic, 0.5 g of Vancomycin, 1.0 g of Vancomycin, or 1.0 g of Tobramycin, was mixed either in air or a vacuum chamber. Following storage in a water bath at 37 degrees C for 48 h, the specimens were tested in four-point bending. The porosity of the specimens was assessed radiographically, and their antibacterial activity was monitored for 21 days. The bending strength of the vacuum mixed specimens containing no antibiotic was 40% greater than that of similar air-mixed specimens. However, there were no significant differences in the bending strength of either the air- or vacuum-mixed specimens when any of the antibiotic dosages were added. The bending modulus of the vacuum-mixed specimens, containing no antibiotic, was significantly greater than the moduli of all the other specimen groups which did not differ from each other. Vacuum mixing reduced the apparent porosity of the specimens fivefold, and while the addition of antibiotic did not effect porosity of the air-mixed specimens, that of the vacuum-mixed specimens was doubled. Although initial rapid decreases were seen, leaching of antibiotic from the cement and antibacterial activity continued through the 21-day monitoring period.

Effects of Vacuum Mixing and Precooking on Restructured Steaks

ABSTRACTThe effects of vacuum mixing and precooking on the binding strength and cook yield of restructured steaks were evaluated. Vacuum mixing was responsible for an increased binding strength of the restructured steak, but had no effect on the cook yield. Precooked, reheated steaks had a significantly higher binding strength, but a lower cook yield than steaks cooked from the frozen, raw state.