Settlement history, land holdings and landscape change, Eyjafjallahreppur, Iceland

In this paper we focus on a region in south Iceland and assess the confidence with which it is possible to determine the changing patterns of settlement history for a region and relate it to contemporaneous land boundaries. For a geographically coherent group of up to 38 possible farm sites in the northern and western part of Eyjafjallahreppur, south Iceland, the timing of occupation and abandonment is assessed. In addition, boundaries of landholdings, probable status and inter-site relationships are identified. Currently only 10 sites are occupied. There is some uncertainty over the location of the earliest settlements, but after the 11th century, successful principle farm sites such as Dalur, Seljaland and Mörk remain in the same locations. As a result, recent data on landholdings combined with a knowledge of the form of landholding sub-division, offers insights into pre-modern times, with some data relevant to medieval times. An ‘abandoned frontier’ exists in the inland area of Þórsmörk, but abandonment is not restricted to the uplands; it has occurred throughout the region. Most desertion occurred before the cold phases of the Little Ice Age in the 18th century. Overall, much farm desertion can be attributed to landscape destruction as a result of river migration, but it is also biased towards small dependent farms often established for social reasons (such as the property requirement for marriage) and evidently insufficiently resourced for long term success in a changing physical environment

Degrees of success : evaluating the environmental impacts of long term settlement in South Iceland.

This paper focuses on the occupation and landscape history of Dalur and Mörk, two areas of long-term settlement in the Eyjafjallahreppur district of southern Iceland. The aim is to illustrate the importance of evaluating not only farm occupation and abandonment, but also to assess the complexities of the environmental interactions of long-term settlements. Environmental records are assessed using data from 50 sediment profiles, constrained by tephrochronology, located in the farm infields (tún) and outfields (hagi). This record indicates that despite similar outward appearances today, the environs of Dalur and Mörk have experienced different histories of environmental change over the last 1000 years. At least 14 subsidiary settlements were at one time or another established within Dalur, or were dependent on the Church farm there. Ten of these settlements were subsequently abandoned and sediment accumulation rates, a proxy indicator of erosion, remained low, indicating restricted local human impact. We conclude that this illustrates the importance of access and rights to additional resources out with the principal farm. In addition, much of the immediate environs of the main farm site was probably un-wooded at the time of settlement, so the total degree of vegetative change was limited. In contrast, palaeoenvironmental data indicates that the environs of Mörk were extensively wooded at the time of Landnám, but this woodland was rapidly cleared and this was followed by several centuries of landscape instability. In a cultural contrast, the landholdings of Mörk experienced less subdivision with a total of only five dependent farms established across the land belonging to three main farms (all of which had chapels). From the early 10th to 14th centuries there was significantly enhanced erosion within the Mörk landholdings, but this stabilised and the principal farms endured and to form sites of long-term settlement. The ownership of additional resource rights, including woodland further up-valley, may have made the crucial contribution to long term endurance

An over-optimistic pioneer fringe ? environmental perspectives on medieval settlement abandonment in Þórsmörk, South Iceland.

We assess environmental factors that may have contributed to farm abandonment in Þórsmörk, south Iceland. Here farms were established during the initial Norse colonisation of Iceland and abandoned by the 13th century AD. Soil erosion has been identified as a possible factor in this settlement change. This hypothesis is assessed using sediment profiles constrained by tephrochronology in Þórsmörk and the nearby area of Stakkholt. In Þórsmörk, there is evidence for episodes of landscape instability between the 10th and 13th centuries and localised episodes of soil erosion to bedrock that ended before 1300 AD and the onset of the Little Ice Age (LIA) climate changes. This early instability is absent from Stakkholt. Later LIA stability in Þórsmörk contrasts with episodes of instability in Stakkholt. The implication is that Þórsmörk was sensitive to early settlement impacts that lead to extensive erosion. After farm abandonment in Þórsmörk, the surviving woodland was successfully conserved as a valuable source of wood and charcoal for lowland farms where woodland resources had been depleted. Mounting pressure on woodland resources in the 11th -12th centuries could have been an important factor in determining the precise timing of abandonment

Lactic acid bacteria as structural building blocks in non-fat whipping cream analogues

Lactic acid bacteria as food ingredients, show the potential of being exploited as structural building blocks in the formulation of colloidal foods such as emulsion and foam. The present work provides approaches to using lactic acid bacteria combined with two components, hydroxypropyl methylcellulose (HPMC) and casein sodium (CS) salt, to fully replace the saturated fat content in whipping cream analogues. By involving both hydrophobic and hydrophilic strains, the whipped cream exhibited comparable overrun (107%) and drainage stability (drainage area 1.4 mm2) to the commercial dairy whipping cream (30% and 2.7 mm2, respectively), where the foam stability was greatly affected by the Pickering capability and aggregating properties of the used strains. All the whipped cream displayed solid-like behaviors (G’>G″) and standing properties to different degrees (G’ ≈ 30–491 Pa), depending on the strength of bacterial aggregation jointly determined by both the intrinsic surface properties and the influence of added HPMC and CS components. No negative impacts on bacterial viability was found for the added components and the whipping process. The idea of involving edible lactic acid bacteria as fat replacers can thus provide possible alternatives to using nature-derived components as active structural building blocks for colloidal food systems such as whipping cream

The effect of surface properties of polycrystalline, single phase metal coatings on bacterial retention

In the food industry microbial contamination of surfaces can result in product spoilage which may lead to potential health problems of the consumer. Surface properties can have a substantial effect on microbial retention. The surface characteristics of chemically different coatings (Cu, Ti, Mo, Ag, Fe) were defined using white light profilometry (micro-topography and surface features), atomic force microscopy (nano-topography) and physicochemical measurements. The Ag coating had the greatest topography measurements and Fe and Mo the least. Mo was the most hydrophobic coating (lowest γAB,γ+, γ−) whilst Ag was the most hydrophilic (greatest γAB,γ+, γ−). The physicochemical results for the Fe, Ti and Cu coatings were found to lie between those of the Ag and Mo coatings. Microbiological retention assays were carried out using Listeria monocytogenes, Escherichia coli and Staphylococcus aureus in order to determine how surface properties influenced microbial retention. It was found that surface chemistry had an effect on microbial retention, whereas the shape of the surface features and nano-topography did not. L. monocytogenes and S. aureus retention to the surfaces were mostly affected by surface micro-topography, whereas retention of E. coli to the coatings was mostly affected by the coating physicochemistry. There was no trend observed between the bacterial cell surface physicochemistry and the coating physicochemistry. This work highlights that different surface properties may be linked to factors affecting microbial retention hence, the use of surface chemistry, topography or physicochemical factors alone to describe microbial retention to a surface is no longer adequate. Moreover, the effects of surface parameters on microbial retention should be considered individually for each bacterial genus

Enzymatic modification and adsorption of hydrophobic zein proteins on lactic acid bacteria stabilize Pickering emulsions

The effect of enzymatic and physical modifications of the surface of two different strains from lactic acid bacteria, Lactobacillus rhamnosus (LGG) and Lactobacillus delbruekii subs. lactis ATCC 4797 (LBD), to stabilize medium-chain triglyceride (MCT) oil based Pickering emulsions were investigated. A section of cell wall degrading enzymes, lysozyme from chicken egg white and human, lysostaphin, mutanolysin from Streptomyces globisporus and proteinase k and the hydrophobic protein zein were used for enzymatic and physical surface modifications. Cell surface modifications were characterized by optical microscopy, scanning electron cryo-microscopy (Cryo-SEM), transmission electron microscopy (TEM), microbial adhesion to hexadecane (MATH) test and zeta potential measurements. The modified cell hydrophobicity in terms of MATH values were increased (around four times) by the enzymatic and physical modifications for LBD and LGG compared to the control. Emulsions stabilized by modified bacterial cells showed higher stability in comparison with unmodified samples, especially for the samples modified with chicken egg lysozyme. Confocal microscopy revealed that the modified bacterial cells were absorbed at the interface between oil and water and preventing the oil particles from coalescence. Thus, modified bacterial cells can be used to formulate food-grade stable Pickering emulsions. Such Pickering emulsions can potentially be clean label alternatives to replace the conventional emulsion preparations

Multi-species colloidosomes by surface-modified lactic acid bacteria with enhanced aggregation properties

Hypothesis: Surface modification of lactic acid bacteria enhances their adsorption and aggregation at air–water interface and enables stabilization of microbubbles that spontaneously transform into water-filled colloidosomes, which can be further modified using LBL formulations. Experiments: The bacterial physicochemical properties were characterized using water contact angle (WCA) measurement, bacterial aggregation assay and zeta potential measurement. Cell viability was enumerated using plate-counting method. The LBL reinforcement of colloidosomes was examined by zeta potential measurement and the formed microstructure was investigated using bright-field microscopy, confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Shell permeability of colloidosomes was evaluated using a dye release study. Findings: Bacteria surface-modified using octenyl succinic anhydride (OSA) expressed strong adsorption and aggregation at air–water interface when producing microbubbles. Bacteria with enhanced aggregation ability formed stable shells, enabling complete removal of air and air–water interface without shell disintegration. The formed colloidosomes were studied as they were, or were further reinforced by LBL deposition using polymer or hybrid formulations. Hybrid coating involved assembly of two bacterial species producing colloidosomes with low shell porosity. The findings can be exploited to organize different living bacteria into structured materials and to encapsulate and release substances of diverse sizes and surface properties