Lipids in bread making: Sources, interactions, and impact on bread quality

Lipids exhibit important functional properties in bread making, although they are present in lower levels than starch or protein. They originate from flour, in which they are endogenously present, or from added shortening and/or surfactants. This review discusses lipid sources and their interactions during the entire process of bread making from dough mixing to fermentation, proofing, baking and the stored product. The focus is on lipid interactions with starch and gluten proteins, their role in gas cell stabilisation and their impact on bread loaf volume, crumb structure and crumb firming. Widely accepted views on lipid functionality, although often opposing, are presented and critically discussed.     

Unintentional dispersal of aquatic invertebrates via footwear and motor vehicles in a Mediterranean wetland area

• 1. Several human activities, such as actions for nature conservation, research and recreational activities, are closely associated with inland aquatic habitats that are usually considered as isolated island habitats. In this study, the possibility of unintentional dispersal of aquatic invertebrates among water bodies via footwear and motor vehicles was investigated.
• 2. Mud samples collected from boots and from the tyres and wheel cases of cars used for field work by biologists (Camargue, Southern France) were hatched under laboratory conditions and also checked for the presence of unhatched propagules. A large number of organisms hatched and invertebrate propagules from a wide range of taxa were encountered (including Artemia, freshwater large branchiopods, Cladocera, Ostracoda, Rotifera, Turbellaria, Nematoda, etc.). The results also demonstrated that different research groups tend to transport the aquatic invertebrates typical for their respective study systems.
• 3. Human dispersal of aquatic invertebrates has been studied mainly on large continental scales, such as in the case of transoceanic transport via ballast water in ships. This study provides evidence that dispersal via footwear and motor vehicles may result in frequent dispersal of aquatic invertebrates on a local scale, and we presume also occasionally over longer distances. Given the rapid spread of invasive zooplankton species (e.g. Artemia franciscana encountered in this study), we promote caution and recommend cleaning before transport of any equipment which comes in contact with water or aquatic sediment. Copyright © 2010 John Wiley & Sons, Ltd.

     

15N Fertilizer recovery in different tillage–straw systems on a Vertisol in north‐west Mexico

Tillage and residue retention affect nitrogen (N) dynamics and nutrient losses and therefore nitrogen use efficiency (NUE) and crop fertilizer use, however, there is little information about residual fertilizer effects on the subsequent crop. Micro‐plots with ¹⁵N‐labelled urea were established in 2014/2015 on a long‐term experiment on a Vertisol in north‐west Mexico. N fertilizer recovery (NFR) and the effects of residual fertilizer N for summer maize (Zea mays L.) and the subsequent wheat (Triticum durum L.) crop were studied in three tillage–straw management practices (CTB: conventionally tilled beds; PB‐straw: permanent raised beds with residue retention; PB‐burn: permanent raised beds with residue burning). Fertilizer ¹⁵N recovery rates for maize grain across all treatments were low with an average of 11%, but after wheat harvest total recovered ¹⁵N (¹⁵N in maize and wheat straw and grain, residual soil ¹⁵N) was over 50% for the PB‐burn treatment. NFR was lowest in CTB after two cropping cycles (32%). Unaccounted N from applied fertilizer for the maize crop averaged 120 kg ¹⁵N ha^?1 after wheat harvest. However, more than 20% of labelled ¹⁵N was found in the 0–90 cm soil profile in both PB treatments after wheat harvest, which highlights the need for long‐term studies and continuous monitoring of the soil nutrient status to avoid over‐application of mineral N fertilizer.     

Impact of Puroindolines on Semisweet Biscuit Quality: A Fractionation–Reconstitution Approach

Puroindoline (PIN) proteins are a factor determining wheat kernel endosperm texture. Biscuits are preferably made from flour from soft wheat (Triticum aestivum L.). Such wheat contains relatively high levels of wild‐type PINs, the impact of which on biscuit quality is unclear. We here studied the impact of PINs on biscuit texture using model flour samples reconstituted from starch and gluten fractions with varying PIN levels. These were obtained by fractionating flour from soft or durum wheat containing either wild‐type or no PINs, respectively. This approach allowed largely retaining the interaction between PINs and either starch or gluten, such as it exists in flour. High PIN levels enhanced air incorporation during dough preparation, increased dough (lateral) expansion, and yielded larger biscuits with higher porosity, which was mainly because of the larger pores. Biscuit fracture stress negatively correlated with PIN level. Porosity contributed to biscuit mechanical properties, but PINs also affected biscuit matrix strength, which in turn affected fracture stress. PINs seem to exert their softening effect when present above a threshold level, and then they have a stronger impact on biscuit fracture stress than the wheat endogenous lipids.     

The Effects of Fresh Eggs,Egg White,and Egg Yolk,Separately and in Combination with Salt,on Mixogram Properties

Salt and eggs are common ingredients in some wheat flour‐based food systems and significantly impact dough mixing behavior. We evaluated the effect of either whole eggs, egg white, or egg yolk on dough formation and properties with the Mixograph. Inclusion of whole eggs in wheat flour dough recipes increased dough development time, dough stability, and dough strength upon further mixing less than inclusion of only egg white. In contrast, egg yolk addition decreased all of these parameters. Salt had a more pronounced impact on dough containing egg yolk than on dough containing egg white. The present observations can be explained in terms of shielding charges of the gluten protein's ionized groups, which largely affects dough mixing behavior. The work demonstrates that in some applications it can be useful to use egg fractions rather than whole eggs.     

Potential of willow and its genetically engineered associated bacteria to remediate mixed Cd and toluene contamination

Purpose

The purpose of this study was to investigate if bacteria with beneficial properties that were isolated from willow growing on a metal-contaminated site can be further equipped with genes coding for a specific degradation pathway to finally obtain transconjugants that can be inoculated in willow to improve phytoremediation efficiency of mixed contaminations.

Materials and methods

Cultivable rhizosphere bacteria and root endophytes were isolated from willow (cv. Tora) growing on a metal-contaminated soil. All isolated strains were tested for their metal resistance and potential to promote plant growth. The two most promising strains were selected and were equipped with the pTOM plasmid coding for toluene degradation. Both transconjugants were inoculated separately and combined in willow cuttings exposed to mixed Cd–toluene contamination, and their effect on phytotoxicity, Cd uptake, and toluene evapotranspiration was evaluated.

Results and discussion

Many of the isolated strains tested positive for the production of siderophores, organic acids, and indole acetic acid (IAA) and showed increased Cd resistance. The Cd-resistant, siderophore-producing rhizosphere strain Burkholderia sp. HU001 and the Cd-resistant root endophyte Pseudomonas sp. HU002, able to produce siderophores, organic acids, and IAA, were selected as receptors for conjugation with the toluene-degrading Burkholderia vietnamiensis BU61 as a donor of the pTOM-TCE plasmid. Although inoculation with the individual transconjugant strains had no effect on plant growth and negatively affected Cd uptake, their combined inoculation resulted in an increased shoot biomass upon Cd–toluene exposure did not affect Cd uptake and strongly reduced evapotranspiration of toluene to the atmosphere.

Conclusions

In this study, inoculation of willow with a consortium of plant-associated bacteria equipped with the appropriate characteristics resulted in an improved phytoremediation of a mixed Cd–toluene contamination: the degradation of toluene was improved leading to a decreased toxicity and evapotranspiration, while Cd uptake and translocation were not affected.     

Salmonella Typhimurium induces SPI-1 and SPI-2 regulated and strain dependent downregulation of MHC II expression on porcine alveolar macrophages

ABSTRACT: Foodborne salmonellosis is one of the most important bacterial zoonotic diseases worldwide. Salmonella Typhimurium is the serovar most frequently isolated from persistently infected slaughter pigs in Europe. Circumvention of the host's immune system by Salmonella might contribute to persistent infection of pigs. In the present study, we found that Salmonella Typhimurium strain 112910a specifically downregulated MHC II, but not MHC I, expression on porcine alveolar macrophages in a Salmonella pathogenicity island (SPI)-1 and SPI-2 dependent way. Salmonella induced downregulation of MHC II expression and intracellular proliferation of Salmonella in macrophages were significantly impaired after opsonization with Salmonella specific antibodies prior to inoculation. Furthermore, the capacity to downregulate MHC II expression on macrophages differed significantly among Salmonella strains, independently of strain specific differences in invasion capacity, Salmonella induced cytotoxicity and altered macrophage activation status. The fact that strain specific differences in MHC II downregulation did not correlate with the extent of in vitro SPI-1 or SPI-2 gene expression indicates that other factors are involved in MHC II downregulation as well. Since Salmonella strain dependent interference with the pig's immune response through downregulation of MHC II expression might indicate that certain Salmonella strains are more likely to escape serological detection, our findings are of major interest for Salmonella monitoring programs primarily based on serology.     

The role of gluten in a sugar-snap cookie system: A model approach based on gluten–starch blends

The cookie making properties of dough made from blends of commercial wheat starch and gluten were determined. Higher gluten levels decreased dough piece weight, its density, stickiness and hardness. The largest spread was obtained when no gluten was added. However, this resulted in cookies of unacceptable structure. Higher gluten contents increased spread onset time, decreased cookie spread but generally had little impact on set time while additional water lowered spread onset time and likewise had no statistically significant impact on set time. The results showed that the final cookie diameter is quite dependent on the spread onset time which itself depends on the amount of water available to the non-gluten constituents in the system. Size-exclusion high performance liquid chromatography showed that during baking, proteins aggregated. This indicated that during the process the added gluten acquired the necessary mobility for interaction. However, because increasing levels of gluten increasingly decreased the relative level of water available to itself, and because the set time, and, hence, the set temperature, did not depend on the gluten level, we concluded that cookie dough setting was not determined by an ‘apparent’ glass transition. Furthermore, more protein aggregation went hand in hand with less spread.     

The Rheo Extrusion Meter,a New Device for Measuring Wheat Flour Baking Absorption and Dough Consistency: Principle and Applications

The Rheo Extrusion Meter (REM) measures the time for vertical upward extrusion of wheat flour dough (subsequently referred to as extrusion time, ET) as a measure of its consistency. ET evidently increases with dough consistency. ETs are highly reproducible and sensitive to differences in dough moisture content. A single REM analysis takes 20 min, and the measured ET can be converted into the correct baking absorption at a given temperature. The heights of the extruded dough pieces are negatively correlated with straight‐dough bread loaf specific volume, both when comparing different flour samples and when adjusting moisture content of dough prepared from a given flour sample. The REM also allows determination of the consistency of complex wheat flour based systems and the impact of vital wheat gluten or ascorbic acid thereupon. Furthermore, in contrast to the farinograph, it detects the impact of endoxylanases hydrolyzing water‐extractable arabinoxylan on dough consistency.