Short communication: Effect of stirring operations on changes in physical and rheological properties of nonfat yogurts during storage.

The rheological and physical properties of stirred yogurt depend on several parameters, including the mechanical stress caused by stirring, smoothing, and cooling conditions (duration, intensity, or temperature). However, the literature reports little information about the effects of mechanical stress from all of the stirring operations on changes in yogurt properties during storage. The aim of this study was to determine, by means of a technical scale unit, the combined effects of stirring in the yogurt vat, smoothing, and cooling on changes in the rheological properties of nonfat yogurt during storage at 4°C. The yogurt was standardized to 14% total solids, 0% fat, and 4% protein, and was stirred with a technical scale unit using 2 stirring durations (5 min or 10 min), 2 types of cooling systems (plate or tubular heat exchanger), and 2 smoothing temperatures (38°C for yogurts smoothed before cooling or 20°C for yogurts smoothed after cooling). All yogurts were stored for 22 d at 4°C, and we determined the combined effect of the stirring operations on changes in syneresis, apparent viscosity, firmness, consistency, and flow time. During storage, post-acidification was the same for all stirred yogurts and involved restructuring of the protein network, which resulted in an increase in all properties except syneresis, which decreased. The combined stirring operations did not modify changes in syneresis during yogurt storage but did affect flow time, viscosity, consistency, and firmness. Changes in flow time depended on smoothing temperature, and viscosity and consistency depended on the cooling system used. Firmness was the property most affected by all combined stirring operations during storage. Therefore, the technical scale unit was effective for quantifying the combined effects of stirring, smoothing, and cooling on changes in yogurt properties during storage. This study also confirmed that the restructuring of stirred yogurt depended on the mechanical stress that occurred during the stirring process.

Individual and sequential effects of stirring, smoothing, and cooling on the rheological properties of nonfat yogurts stirred with a technical scale unit.

Few studies have considered the impact of unit operations during stirred yogurt manufacture because their operational sequence is difficult to replicate at the laboratory scale. The aim of this study was to investigate the individual and sequential effects of stirring in the yogurt vat, smoothing, and cooling on the rheological properties of yogurts, using a technical scale unit simulating some industrial conditions. The yogurts were prepared from a milk mixture that was standardized to contain 14% total solids, 0% fat, and 4% protein, and then homogenized, heated (94.5°C, 5 min), and inoculated at 41°C with the same thermophilic lactic starter. The operating parameters under investigation were 2 stirring durations in the yogurt vat (5 or 10 min), 2 cooling systems (plate or tubular heat exchanger), and 2 smoothing temperatures (38°C for smoothing before cooling; 20°C for smoothing after cooling). Sampling valves were installed at critical points on the technical scale unit so that the effect of each operation on the properties of stirred yogurt could be quantified individually. Syneresis, apparent viscosity, firmness, and consistency were analyzed after 1 d of storage at 4°C. In general, as the yogurts moved through the technical scale unit, the properties of the yogurts (evaluated after 1 d) changed: viscosity increased but syneresis, firmness, and consistency decreased. The individual effects of the operations showed that smoothing and cooling, compared with stirring duration, made the greatest contribution in terms of modifying yogurt properties. The stirring parameters (5 or 10 min) had similar effects on the yogurts. The use of a plate heat exchanger promoted a decrease in syneresis, whereas a tubular heat exchanger had a greater effect in terms of increasing firmness and consistency. The type of cooling system had no effect on stirred yogurt viscosity. Smoothing at 38°C had a greater effect on the increase in firmness, whereas smoothing at 20°C contributed more to a decrease in syneresis and increases in viscosity and consistency. This study confirms that each unit operation has a defined effect on the rheological properties of a nonfat stirred yogurt, which also depends on the operation sequence.

Estimates of water and solute release from a coal waste rock dump in the Elk Valley, British Columbia, Canada.

Long term (1999 to 2014) flow and water quality data from a rock drain located at the base of a coal waste rock dump constructed in the Elk Valley, British Columbia was used to characterize the release of three solutes (NO3-, Cl- and SO42-) from the dump and obtain whole dump estimates of net percolation (NP). The concentrations of dump derived solutes in the rock drain water were diluted by snowmelt waters from the adjacent natural watershed during the spring freshet and reached a maximum concentration during the winter baseflow period. Historical peak baseflow concentrations of conservative ions (NO3- and Cl-) increased until 2006/07 after which they decreased. This decrease was attributed to completion of the flushing of the first pore volume of water stored within the dump. The baseflow SO42- concentrations increased proportionally with NO3- and Cl- to 2007, but then continued to slowly increase as NO3- and Cl- concentrations decreased. This was attributed to ongoing production of SO42- due to oxidation of sulfide minerals within the dump. Based on partitioning of the annual volume of water discharged from the rock drain to waste rock effluent (NP) and water entering the rock drain laterally from the natural watershed, the mean NP values were estimated to be 446±50mm/a (area normalized net percolation/year) for the dump and 172±71mm/a for the natural watershed. The difference was attributed to greater rates of recharge in the dump from summer precipitation compared to the natural watershed where rainfall interception and enhanced evapotranspiration will increase water losses. These estimates included water moving through subsurface pathways. However, given the limitations in quantifying these flows the estimated NP rates for both the natural watershed and the waste rock dump are considered to be low, and could be much higher (e.g. ~450mm/a and ~800mm/a).

Preparation, immunogenicity, and protective efficacy, in a murine model, of a conjugate vaccine composed of the polysaccharide moiety of the lipopolysaccharide of Vibrio cholerae O139 bound to tetanus toxoid.

The epidemic and pandemic potential of Vibrio cholerae O139 is such that a vaccine against this newly emerged serogroup of V. cholerae is required. A conjugate made of the polysaccharide moiety (O-specific polysaccharide plus core) of the lipopolysaccharide (LPS) of V. cholerae O139 (pmLPS) was prepared by derivatization of the pmLPS with adipic acid dihydrazide and coupling to tetanus toxoid (TT) by carbodiimide-mediated condensation. The immunologic properties of the conjugate were tested using BALB/c mice injected subcutaneously three times at 2 weeks interval and then a fourth time 4 weeks later. Mice were bled 7 days after each injection and then once each month for the following 6 months. LPS and TT antibody levels were determined by enzyme-linked immunosorbent assay using immunoplates coated with either O139 LPS or TT. Both pmLPS and pmLPS-TT conjugate elicited low levels of immunoglobulin M (IgM), peaking 5 weeks after the first immunization. The conjugate elicited high levels of IgG antibodies, peaking 3 months after the first immunization and declining slowly during the following 5 months. TT alone, or as a component of conjugate, induced mostly IgG antibodies. Antibodies elicited by the conjugate recognized both capsular polysaccharide and LPS from V. cholerae O139 and were vibriocidal. They were also protective in the neonatal mouse model of cholera infection. The conjugation of the O139 pmLPS, therefore, enhanced its immunogenicity and conferred T-dependent properties to this polysaccharide.

Crystal structure of an anti-carbohydrate antibody directed against Vibrio cholerae O1 in complex with antigen: molecular basis for serotype specificity.

The crystal structure of the murine Fab S-20-4 from a protective anti-cholera Ab specific for the lipopolysaccharide Ag of the Ogawa serotype has been determined in its unliganded form and in complex with synthetic fragments of the Ogawa O-specific polysaccharide (O-SP). The upstream terminal O-SP monosaccharide is shown to be the primary antigenic determinant. Additional perosamine residues protrude outwards from the Ab surface and contribute only marginally to the binding affinity and specificity. A complementary water-excluding hydrophobic interface and five Ab-Ag hydrogen bonds are crucial for carbohydrate recognition. The structure reported here explains the serotype specificity of anti-Ogawa Abs and provides a rational basis toward the development of a synthetic carbohydrate-based anti-cholera vaccine.

[Cholera update and vaccination problems]. / Actualité du choléra et problématique vaccinale.

Cholera remains an important public health problem. The long-term control of cholera depends on good personal hygiene, uncontaminated water supply and appropriate sewage disposal. However, the improvement of hygiene is distant goal for many countries. Thus the availability of an effective cholera vaccine is important for the prevention of cholera in these countries. Research on new cholera vaccines has mainly focused on oral formulations that stimulate the mucosal secretory immune system. Two oral cholera vaccines were experimented on large scale in human. The first vaccine, containing inactivated bacterial cells and B-subunit of cholera toxin, has been tested in Bangladesh from 1985 to 1989. This vaccine, according to WHO, may prove useful in the stable phase of refugee/displaced person crises, especially when given preventively. The second vaccine is a live attenuated vaccine containing the genetically manipulated Vibrio cholerae O1 strain CVD 103-HgR. Despite its efficacy in adult volunteers, results of a large-scale field trial carried-out in Indonesia for 4 years have shown a surprisingly low protection. Moreover, one of the safety concerns associated with live cholera vaccine is a possible horizontal gene transfer and recombination event leading to reversion to virulence. A new vaccine development program for cholera is based upon the hypothesis that immunoglobulins G directed to the O-specific polysaccharide of Vibrio cholerae O1 could confer protective immunity to cholera by inactivating the inoculum on intestinal mucosal surface. This program may lead to the development of cholera conjugate vaccines to elicit protection in infants.

On the antigenic determinants of the lipopolysaccharides of Vibrio cholerae O:1, serotypes Ogawa and Inaba.

Monoclonal, murine IgG1s S-20-4, A-20-6, and IgA 2D6, directed against Vibrio cholerae O:1 Ogawa-lipopolysaccharide exhibited the same fine specificities and similar affinities for the synthetic methyl alpha-glycosides of the (oligo)saccharide fragments mimicking the Ogawa O-polysaccharide (O-PS). They did not react with the corresponding synthetic fragments of Inaba O-PS. IgG1s S-20-4 and A-20-6 have absolute affinity constants for synthetic Ogawa mono- to hexasaccharides of from approximately 10(5) to approximately 10(6) M-1. For IgG1s S-20-4, A-20-6, and IgA 2D6, the nonreducing terminal residue of Ogawa O-PS is the dominant determinant, accounting for approximately 90% of the maximal binding energy shown by these antibodies. Binding studies of derivatives of the Ogawa monosaccharide and IgGs S-20-4 and A-20-6 revealed that the C-2 O-methyl group fits into a somewhat flexible antibody cavity and that hydrogen bonds involving the oxygen and, respectively, the OH at the 2- and 3-position of the sugar moiety as well as the 2'-position in the amide side chain are required. Monoclonal IgA ZAC-3 and IgG3 I-24-2 are specific for V. cholerae O:1 serotypes Ogawa/Inaba-LPS.1 The former did not show binding with members of either series of the synthetic ligands related to the O-antigens of the Ogawa or Inaba serotypes, in agreement with its reported specificity for the lipid/core region (1). Inhibition studies revealed that the binding of purified IgG3 I-24-2 to Ogawa-LPS might be mediated by a region in the junction of the OPS to the lipid-core region of the LPS. cDNA cloning and analysis of the anti-Ogawa antibodies S-20-4, A-20-6, and 2D6 revealed a very high degree of homology among the heavy chains. Among the light chains, no such homology between S-20-4 and A-20-6 on the one hand, and 2D6 on the other hand, exists. For the anti-Inaba/Ogawa antibodies I-24-2 and ZAC-3, their heavy chains are completely different, with some homology among the light chains.

The change experience of a long-term care centre.

This article highlights the methodology and approaches chosen in preparing for a major change in orientation at La Pietà in Hull, Quebec, devising the content for change and facilitating the implementation of new directions. It is based on the observations of the change seen within the organization, research and interviews with management and the hired consultant involved in the change process. The first part of the article establishes the situation confronting the organization. It then describes the frame of reference that was to guide the centre through the change process. The conclusion sums up the La Pietà experience in the light of the guiding principles and elements that together formed the frame of reference for the change.

Circulatory and metabolic responses to carbon monoxide hypoxia during beta-adrenergic blockade.

The role(s) of beta-adrenoceptors in whole body and hindlimb skeletal muscle cardiovascular and metabolic responses during carbon monoxide hypoxia (COH) was studied in anesthetized dogs. One group of animals was beta-blocked with propranolol (beta 1- and beta 2-blockade), a second was given ICI 118,551 (beta 2-blockade), and a third served as a time control. Immediately after a control-sampling period, COH was induced (about a 63% decrease in arterial O2 content), and additional measurements were then obtained at 30 and 60 min of hypoxia. Cardiac output values were not different between the three series at control; an increase (P less than 0.05) occurred in all groups during COH. This rise was greatest in the COH group; the values for the propranolol- and ICI 118,551-blocked groups were not different from each other during COH. Hindlimb blood flow rose (P less than 0.05) during COH only in the control group. Both whole body (30 min) and hindlimb (30 and 60 min) resistance values were greater during hypoxia in the beta-blocked groups (P less than 0.05) than in the control series. Furthermore, whole body oxygen uptake decreased (P less than 0.05) in both beta-blocked groups during COH. We conclude that approximately 35% of the rise in cardiac output occurring during COH depended on peripheral vasodilation mediated through beta 2-adrenoceptors.

The role of alpha-adrenergic receptors in carbon monoxide hypoxia.

The importance of alpha-adrenergic receptors in the cardiac output and peripheral circulatory responses to carbon monoxide (CO) hypoxia was studied in anesthetized dogs. Phenoxybenzamine (3 mg/kg i.v.) was injected to block alpha-receptor activity and the data obtained were then compared with those from a previous study of CO hypoxia in unblocked animals. Values for cardiac output, hindlimb blood flow, vascular resistance, and oxygen uptake were obtained prior to and at 30 and 60 min of CO hypoxia which reduced arterial oxygen content by approximately 50%. alpha-Adrenergic blockade resulted in a lower (p less than 0.05) control value for cardiac output than observed in unblocked animals, but no differences were present between the two groups at 30 or 60 min of CO hypoxia. Similarly, limb blood flow was lower (p less than 0.05) during the control period in the alpha-blocked group but rose to the same level as that in the unblocked animals at 60 min of COH. No change in limb blood flow occurred during CO hypoxia in the unblocked group. These findings demonstrated that during CO hypoxia alpha-receptor mediated venoconstriction does not contribute to the cardiac output response and alpha-receptor mediated vasoconstriction probably does prevent a rise in hindlimb skeletal muscle blood flow.